Catalog NDT 2010

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GERMANN INSTRUMENTS

Test smart - Build right

Taking NDT to new heights!

This catalog is intended to acquaint potential users with the principles that underpin the proven test systems that are presented and to provide typical examples of their application. Please contact Germann Instruments for additional technical and ordering information On the Cover: Rising to a majestic height of 828 m, the Burj Khalifa shattered the previous height record and is the World's Tallest Building. It is a testament to our ability to meet difficult challenges by using our technical knowledge in combination with our creative abilities. We are grateful to Skidmore, Owings & Merrill LLP for providing the cover photo and inspiring us to new heights.

GERMANN INSTRUMENTS A/S Emdrupvej 102, DK-2400 Copenhagen, Denmark Phone: +45 39 67 71 17, Fax +45 39 67 31 67 E-mail: germann-eu@germann.org Web site: www.germann.org

GERMANN INSTRUMENTS, Inc. 8845 Forest View Road, Evanston, Illinois 60203, USA Phone: (847) 329-9999, Fax: (847) 329-8888 E-mail: germann@germann.org Web Site: www.germann.org

GI

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Introduction

1

For over a quarter of a century, Germann Instruments has been the leader in the field of test systems for nondestructive testing (NDT) and on-site investigation of reinforced concrete structures.

Germann Instruments constantly develops, manufactures, and markets worldwide its innovative and cutting-edge product line through offices in Denmark, the United States, and Luxembourg and through distributors in Europe, the Middle East, and Asia.

The test systems cover varied aspects of concrete construction and investigation, such as

Durability Assessment

Service Life Estimation

Fast-Track Construction

Structural Integrity

Corrosion Survey

Repair Quality

Structural Monitoring Every year, Germann Instruments adds new products to its long line of test systems and keeps improving its existing systems. This catalog includes seven new systems that were not in the previous catalog.

The systems are used to perform totally nondestructive test methods or test methods that require limited near-to-surface specimen removal. When properly applied, these test systems allow rapid testing and provide immediate results on-site. Also include are two methods for testing fresh concrete. While they are the traditional types of NDT tests, they are important methods for on-site quality control and quality assurance.

For correct operation, the test systems have to be maintained properly and need to be calibrated according to the procedures outlined in the users’ manuals and in accordance with applicable standards.

For optimal use of these systems, field engineers and consultants have to be trained and skilled in planning testing programs, using the test systems, and interpreting test results. Furthermore, an understanding of the fundamental deterioration mechanisms of reinforced concrete structures is essential for proper planning and execution of testing programs. Germann Instruments has, therefore, formed an international group, the NDT-Titans, to provide consulting, training, technical support, and on-site testing of structures. This group brings the knowledge and expertise of well-seasoned, engineering professionals to as many users of these test systems as possible. The services are outlined page 129 and on the homepage of the group:

www.NDT-Titans.com Germann Instruments continues to affirm its commitment to serve the in-situ and nondestructive testing community by placing state-of-the-art, technically proven, diagnostic tools in the hands of field engineers and consultants.

Alphabetical List of Test Systems

2

Product Name Property or Parameter Measured Relevant Standard/Document pg.

Auto-Shrink Autogenous shrinkage of specimens in special molds using sealed curing ASTM C1698 5

AVA Spacing factor and specific surface of air-void system in air-entrained fresh concrete AASHTO TP 75 7

Be4Cast Simulation of development of temperature gradients and stresses during hardening of concrete for evaluation of cracking potential

13

BOND-TEST Bond strength of overlay or tensile strength of substrate BS 1881:207, ASTM C1583 15

CAPO-TEST Concrete strength in existing structures EN 12504-3, ASTM C900, BS 1881:207 20

CMD Crack movement 24 COMA-Meter Maturity of hardening concrete ASTM C1074 26

CORECASE Coring for strength and durability assessment ASTM C42/C42M , EN 12504-1 28

CorroEye Corrosion rate of reinforcement ACI 228.2R 30 CorroWatch Chloride penetration into concrete 32

CoverMaster Location, depth and size of reinforcement; plus half-cell potential

BS 1881:204, ACI 228.2R ASTM C876 33

CrackScope Width of cracks 36 Deep Purple and Rainbow Indicator Carbonation depth 37

DK-5000 Resonant frequency of specimens for material properties and monitoring degradation of specimens in durability tests

ASTM C215, BS 1881:209 39

DOCter Thickness measurement and flaw detection, including depth of flaws by impact-echo ASTM C1383 41

DSS-TEST Shear-bond strength of carbon fiber reinforced polymer (CFRP) strips 47

Eddy-Dowel Location of dowel bars in jointed pavements ACI 228.2R 49

Eddy-Thick Thickness measurement of slab-of-ground using embedded metal targets and pulse-induction method

52

ERE-Probe Long-term monitoring of half-cell potential of reinforcement using embedded probe 55

EyeCon Flaw detection and thickness measurement by ultrasonic pulse-echo ACI 228.2R 56

GalvaPulse Corrosion rate and half-cell potential of reinforcement; electrical resistance of concrete

ASTM C876 (half-cell potential) 61

Guardian Actual temperatures and maturity development in hardening structure ASTM C1074 65

GWT Water penetrability ISO/DIS 7031 67 HUM-Meter Internal moisture content using probes 69

ICAR Rheometer Measures yield strength and dynamic viscosity of fresh concrete 71

Alphabetical List of Test Systems

3

Product Name Property or Parameter Measured Relevant Standard/Document pg.

LOK-TEST Early-age strength of concrete BS EN 12504-3, ASTM C900, BS 1881:207 75

Merlin Bulk conductivity of saturated specimens, which can be related to the chloride ion diffusion coefficient

80

Mini Great Dane Half-cell potential of reinforcement and electrical resistance of concrete ASTM C876 85

MIRA Tomographic imaging of flaws and thickness measurement by ultrasonic pulse-echo ACI 228.2R 87

Moisture Encounter Near surface moisture content 93 PetroPlaner

Prepare polished plane surfaces for air void, petrographic, or SEM analysis ASTM C457, ASTM C856 94

PetroThin

Prepare polished thin sections, including fluorescent epoxy impregnation, for petrographic analysis

ASTM C856 96

POWER Proof-loading of anchors 98 Profile Grinder

Chloride diffusion coefficient on-site or after ponding of specimens in the laboratory

ASTM C1556, NT Build 443, ASTM C1543 99

PROOVE´it

Resistance to chloride ion penetration and estimation of the chloride diffusion coefficient ASTM C1202, NT BUILD 492 101

PUNDIT Ultrasonic pulse velocity by through transmission

ASTM C597, BS EN 12504-4, BS 1881:203 105

RapidAir

Air content, spacing factor and specific surface of hardened, air-entrained concrete ASTM C457 108

RAT Alkali content of fresh concrete 110

RCT and RCTW Chloride content of powder samples using acid or water to extract soluble chlorides

AASHTO T 260, ASTM C114, ASTM C1152, ASTM C1218 112

s´MASH Rapid testing for flaws and for length of piles using impulse-response method ACI 228.2R 116

STEPPER Automated testing for flaw detection and thickness using impact-echo method ACI 228.2R 121

Surfer Ultrasonic pulse velocity by surface measurement 124

TORQ-TEST Shear-bond strength of overlays or CFRP laminates 127

Test Systems by Application

4

Application/Property Test System (pg) Application/Property Test System (pg)

Air void system AVA (7) Rapid Air (108)

Electrical resistance CorroEye (30) Mini Great Dane (85)

Alkali Content RAT (110) Electrical resistivity Merlin (80)

Anchor bolt proof load test POWER (98)

Flaw detection

DOCter (41) Eyecon (56) MIRA (87) s”MASH (116) STEPPER (121)

Autogenous shrinkage AutoShrink (5)

Half-cell potential Mini Great Dane (85) ERE Probe (55) CoverMaster (33)

Bond/Tensile strength BOND TEST (15)

In-place strength

BOND-TEST (15) CAPO-TEST (20) LOK-TEST (75) TORQ-TEST (127)

Carbonation Deep Purple and Rainbow Indicator (37)

Maturity COMA-Meter (26) Guardian (65)

Chloride content RCT and RCTW (112)

Moisture content HUM-Meter (69); Moisture Encounter (93)

Chloride penetrability Merlin (80) PROOVE’it (101)

Resonant frequency DK-5000 (39)

Chloride penetration CorroWatch (32) RCT and RCTW (112)

Rheology of concrete (yield strength and viscosity)

ICAR-Rheometer (71)

Chloride profiling Profile Grinder (99) RCT and RCTW (112

Shear strength DSS-TEST (47) TORQ-TEST (127)

Core drilling CORECASE (28) Shear-bond strength DSS-TEST (47)

Corrosion rate CorroEye (30) GalvaPulse (61)

Specimen preparation PetroPlaner (94) PetroThin (96)

Cover over reinforcement

CoverMaster (33) Eddy-Dowel (49)

Temperature measurement Guardian (65)

Crack depth DOCter (41) Surfer (124)

Thermal modeling Be4Cast (13)

Crack movement CMD (24)

Thickness measurement

DOCter (41) EyeCon (56) Eddy-Thick (52) MIRA (87) STEPPER (121)

Crack width CrackScope (36) Tomography MIRA (87);

Dowel bar alignment Eddy-Dowel (49) Ultrasonic pulse velocity PUNDIT (105) Surfer (124)

Electrical conductivity Merlin (80) Water penetrability GWT (67)

Auto-Shrink

5

Purpose The Auto-Shrink system measures the unrestrained autogenous shrinkage of a specimen of cement paste or mortar cured under sealed conditions (ASTM C1698). Auto-Shrink permits evaluation of the relative autogenous shrinkage potential of different cementitious systems. Excessive autogenous shrinkage may lead to microcracking that increases the permeability of concrete.

Principle When cement hydrates through chemical reactions with water, the volume occupied by the products of hydration is less than the original volume of cement and water. This phenomenon is known as “chemical shrinkage.” When concrete is cured under sealed conditions (no external source of moisture), the reduction in paste volume due to hydration causes internal tensile stresses that can lead to microcracking. The microcracking, in turn, reduces concrete’s resistance to penetration of water and deleterious substances.

If a specimen of paste or mortar is cured under sealed conditions and allowed to change in volume, the chemical shrinkage of the paste will cause autogenous shrinkage of the specimen. The Auto-Shrink digital dilatometer is designed for linear measurement of autogenous shrinkage in hardening cement-based materials. A special corrugated plastic mold is used to prevent moisture loss and allow the specimen to shrink freely. With Auto-Shrink, it is possible to measure the time dependent deformation of many different specimens simultaneously over periods of weeks or even years. Auto-Shrink is intended primarily for measurements after setting of cement pastes or mortars with a maximum aggregate size of 2 mm. To minimize the influence of temperature variations, the dilatometer should be used in a thermostatically controlled room. Background information on the measurement technique used in Auto-Shrink can be found in the following reference:

Mejlhede Jensen, O. and Freiesleben Hansen, P. “A Dilatometer for Measuring Autogenous Deformation in Hardening Portland Cement Paste,” Materials and Structures, 1995, 28 (181) 406-409

Auto-Shrink System The Auto-Shrink digital dilatometer is composed of the following basic elements: • A corrugated plastic mold with tight-fitting plugs to prepare a slender test specimen • A rigid frame to support the specimen • A digital dial gauge with remote control to measure change in specimen length • A reference bar

Principal components of the Auto-Shrink system

Cement

Water

Fresh Paste Hardening Paste

Cement

Hydrated Cement

Void

Water

Auto-Shrink

6

The digital displacement gauge is fixed firmly to the frame with a blunted hex screw. The remote control is mounted on the side of the gauge. A lock function for the remote control is provided.

Specimens are cast vertically by using support tubes, which can be mounted to a vibrating table. To ensure that the cast specimens have approximately the same length, the corrugated mold should not be stretched or compressed during filling. The mold is filled to approximately 15 mm below the end of the tube to allow room for the top sealing plug. Before the top sealing plug is mounted, the corrugated tube is compressed slightly to bring the cement paste in contact with the sealing plug.

Measurements in the Auto-Shrink dilatometer are conveniently done relative to a reference bar. To ensure optimal measuring accuracy, the reference bar as well as the specimens should be placed in the frame in the same orientation during each measurement. A line mark with permanent ink at one end of the corrugated tube may be used to indicate the proper orientation of the specimen during measurement in the dilatometer. Testing Example In 2009, ASTM adopted a standard test method based on the Auto-Shrink system: "Test Method for Autogenous Strain of Cement Paste and Mortar," ASTM C1698.

The following graph is an example of autogenous strain measured over 2 weeks on a cement paste (w/cm = 0.25) with 10 % silica fume cured at 30 °C. Time is measured from the addition of water. The strain has been defined as 0 at the time of final setting of the paste (from Mejlhede Jensen and Freiesleben Hansen, 1995).

-2000

-1500

-1000

-500

0

0 50 100 150 200 250 300 350

Shrin

kage

, mic

rost

rain

Time, hours Auto-Shrink Ordering Numbers

Item Order # 1 Dilatometer support frame with stop pin AS-1000 1 Digital displacement gauge including remote control AS-1010 1 Reference bar AS-1020 1 Spanner 15 mm AS-1030 1 Hex key 2½ mm AS-1040 50 Corrugated tubes AS-1050 100 Sealing plugs AS-1060 1 Support tube for casting AS-1070 5 grooved support racks each for 10 specimens AS-1080 2 pairs of gloves AS-1090

AVA

7

Purpose The AVA (Air Void Analyzer) is used to measure the air-void parameters (spacing factor and specific surface) of samples of fresh air-entrained concrete. Samples are taken after concrete is placed.

Background The durability of concrete subjected to wetting and cycles of freezing and thawing can be enhanced by deliberately introducing many, small and closely spaced air bubbles (air voids) in the cement paste. During freezing, the ice formed in the capillary pores of the paste will expand into adjacent air voids without damaging the paste, provided the air-void spacing and the size distribution of the air voids are within certain limits. To characterize the air voids, the spacing factor (maximum distance from any point in the cement paste to an air-void boundary) and the specific surface (ratio of the surface area of the air voids to their volume) are used. In general, a good quality, frost resistant concrete requires a spacing factor less than 0.20 mm and a specific surface greater than 25 mm-1.

The spacing factor and the specific surface of the air-void system are determined typically according to ASTM C457 “Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete.” This method requires a sample cored from the hardened concrete on-site and prepared properly in the laboratory as illustrated in the photo to the left. The spacing factor and the specific surface are then measured manually by the linear traverse method using a microscope, or by an automated image analyses system as illustrated on page 108. Determination of the air-void structure in this manner cannot produce timely information during construction, which would be needed to make adjustments to the concrete mixture if the measured parameters are not within specified limits.

Timely information is important, because practice has shown that the air-void structure created by air entraining agents can change easily during construction; for example, due to the type and dosage of normal or high-range water-reducing admixtures, by changes in sources of cementitious materials, by pressure influences in concrete pumps, by high hydrostatic pressure, or by over-vibration.

With the AVA, the air-void structure is measured after the concrete is placed but while it is still fresh, thereby providing timely information of the spacing factor and the specific surface of the air-void system in the cement paste of the in-place concrete. The testing time is 25 minutes or less.

Principle The air bubbles entrained in a mortar sample, which is removed from fresh concrete, are transferred to a blue AVA release liquid as the mortar is stirred. Provided the release liquid has the proper viscosity and hydrophilic character, the bubbles released from the mortar retain their original size and neither coalesce nor disintegrate into smaller bubbles.

Above the blue AVA release liquid there is a column of water through which the air bubbles rise. According to Stoke´s Law, larger bubbles will rise faster than smaller bubbles.

The air bubbles rising through the water column are collected under an inverted and submerged pan attached to a sensitive balance. As air bubbles accumulate in the top of the pan, the apparent mass of the pan decreases as water is displaced by air. The apparent mass of the pan is recorded over time.

Based of the recorded change in apparent mass of the pan, an algorithm calculates the size distribution of the collected air bubbles. From the size distribution, the spacing factor and the specific surface are calculated. The algorithm ensures the parameters are the same as obtained from ASTM C457 linear traverse measurements.

AVA

8

Correlation and Variability The results from the AVA have been correlated to ASTM C457 determinations. Among the published reports are: • Brite Euram Project No: BE-3376-89, Task 2, “Quantitative and Qualitative Determination of

the Air Void structure in Fresh Concrete,” Dansk Beton Teknik A/S, Hellerup, Denmark, Feb. 1994

• FHWA-SA-96-062, “Air Void Analyzer Evaluation,” Federal Highway Administration, Washington DC, USA, 1995

• Price, B., “Measuring Air Voids in Fresh Concrete,” CONCRETE, July/August 1996 • Wojakowski, J., “Air in Portland Cement Concrete Pavements,” Kansas Department of

Transportation, USA, 2002 • Crawford, G.L., Wathne, L.G., and Mullarky, J.I.: “A ‘Fresh’ Perspective on Measuring Air in

Concrete,” Federal Highway Administration, Washington DC, 2003 Bridge Conference, USA

The general conclusion is that the AVA results in air-void parameters that are within ± 10 % of those obtained by ASTM C457. The repeatability coefficients of variation for the AVA spacing factor and the specific surface determinations are normally 8 to 10 %. In 2008, AASHTO adopted a provisional test method for the AVA: "Method of Test for Air-Void Characteristics of Freshly Mixed Concrete by Buoyancy Change," AASHTO TP 75-08.

Testing Example

• A sample of the mortar fraction of the air-entrained concrete is taken by vibrating a wire cage into the plastic concrete (left above). The mortar enters the cage, which excludes particles larger than 6 mm. A syringe is used to collect a 20 cm3 mortar test specimen from within the cage.

• The specimen is injected into the riser column (center above). The riser column has the blue AVA release liquid at the bottom and water above it. The mortar and the liquid are stirred gently by a magnetic stirrer for 30 seconds, and the air voids are released (right above).

• The bubbles rise through the liquids at rates that depend on their size, which results in a separation in time when different size bubbles arrive at the top of the column.

• The bubbles are collected under a submerged pan attached to a balance. A computer connected to the balance records the change in mass of the inverted pan as a function of time.

• In the early stages of the measurement, the size distribution of the air bubbles collecting under the pan range from a few mm to a few micrometers. For each succeeding period, the size of the bubbles that collect under the pan decreases.

• The measurement continues for 25 minutes unless no mass change is recorded for 2 consecutive minutes, in which case the measurement is stopped.

• The AVA software processes the time history of the balance readings and calculates the air-void parameters including spacing factor and specific surface, as shown on the following page.

• In addition, the software produces a graph of the bubble size distribution and a histogram of the different bubble sizes, also illustrated on the following pages.

AVA

9

AVA System Features Two AVA systems are available: the AVA-2000 and the AVA-3000.

AVA-2000 The AVA-2000 is the daily workhorse, and is based on the original Dansk Beton Teknik (DBT) design from the late 1980s. This model features: • A complete system, ready-to-use, including a laptop computer with the AVA-2000 software and

an installed PCMCIA card with driver software • Optimized sensitivity of the balance for eliminating the effects of external vibrations during

testing

AVA-3000 Recently developed, the AVA-3000 features: • Latest microprocessor technology with components minimized in size and number • Only one USB cord is used to connect the laptop computer and the base unit • Incorporates a mini balance that can withstand rough treatment during transport and/or testing • Elimination of the influence of external vibrations on the test results, including the introduction

of a wind shield positioned on top of the riser column • Improved stirrer operation with constant rotational speed independent of the load applied on the

stirrer • Incorporates a 35-L temperature bath tank for automated de-aerating and controlling the

temperatures of the water and the AVA release liquid for testing. The water-filled tank may also function as ballast for stabilizing the base unit

• In addition to the calculation of the spacing factor and the specific surface for chord length less than 2 mm (as in the AVA-2000), the AVA-3000 calculates the air-void parameters for chord length less than 1 mm, as required by the current ASTM C457 standard

Example of AVA-2000 printout, documenting: • The change in mass of the buoyancy pan (x-axis) as a function of time (y-axis), • The results of the analyses, including the spacing factor and the specific surface, and • Comments

AVA

10

Example of AVA-3000 printout, documenting: • The change in mass of the buoyancy pan (x-axis) as a function of time (y-axis), • The results of the analyses, including the spacing factor and the specific surface, and • Comments

Example of AVA-2000 or AVA-3000 printout, documenting: • The size distribution of air voids less than 2 mm (left), and • A histogram of air-void sizes less than 2 mm (right).

AVA

11

The AVA-2000 System

AVA-2000 System

Supplied in a rugged transport case The AVA-2000 base unit with riser column,

buoyancy pan and laptop computer

AVA-2000 System Ordering Numbers

Item Order # Item Order # Base unit AVA-2010 Brush AVA-2130 Riser column AVA-2020 Plexiglas plate with hole for

sampling AVA-2140

Piston with temperature sensor AVA-2030 Bucket for de-aeration of water AVA-2150 Buoyancy pan AVA-2040 Connector box AVA-2160 Vibrating cage AVA-2050 Interface cord, connector box to PC AVA-2170 Vibrating collector AVA-2060 Cord, PC to balance AVA-2180 Electric drill AVA-2070 PCMCIA card and driver software AVA-2190 Funnel for insertion of AVA release liquid into riser column

AVA-2080 Manual for PCMCIA card AVA-2200

Sampling syringes, 5 pcs AVA-2090 CD-ROM for PCMCIA card AVA-2210 Digital thermometer AVA-2100 AVA-2000 software diskette AVA-2220 Heating element AVA-2110 AVA-2000 manual AVA-2230 Bottle for heating AVA release liquid

AVA-2120 AVA release liquid, 5 L AVA-2240

Laptop computer AVA-2250 The AVA-2240 release liquid comes in 5-L containers with controlled batch number and certificate that it has the proper viscosity and hydrophilic characteristics. Each test requires 200 mL of liquid. Delivered separately is the AVA-2260 verification kit (calibrated masses applied to weighing rod). Offered separately is a one-day course by an AVA specialist.

AVA

12

The AVA-3000 System

AVA-3000 System composed of base unit, riser column, temperature bath and laptop computer

AVA-3000 accessories as described below

AVA-3000 System Ordering Numbers

Item Order # Item Order # Base unit AVA-3010 Bottle for heating AVA release liquid AVA-3120 Riser column AVA-3020 Brush AVA-3130 Piston AVA-3030 Plexiglas plate with hole for sampling AVA-3140 Buoyancy pan AVA-3040 Laptop computer AVA-3150 Vibrating cage AVA-3050 Cord, PC to base unit AVA-3180 Vibrating collector AVA-3060 AVA-3000 software diskette AVA-3220 Electric drill AVA-3070 AVA-3000 manual AVA-3230 Funnel for insertion of AVA release liquid into riser column

AVA-3080 AVA release liquid, 5 L AVA-2240

Sampling syringes, 5 pcs AVA-3090

As with the AVA-2000, the AVA-2260 verification kit for checking the balance is offered separately as well as a 1-day training course by an AVA specialist.

Be4Cast

13

Purpose Be4Cast is an advanced software package for simulating temperature evolution and stress development in concrete structures during early-ages. The software allows modeling different construction methods for a given structure in order to arrive at an optimal solution for reducing the risk of early-age cracking due to thermal gradients and thermal shrinkage. Be4Cast is based on heat transfer in 3-dimensions, which permits more accurate simulation of heat transfer in a structural element of any shape.

It is important to control the early-age hardening process of concrete. Inappropriate construction methods can cause: • Freezing before the concrete is strong enough to resist expansion stresses • Rapid evaporation leading to a weak cover layer • High temperature gradients leading to crack formation • Reduction in long-term strength due to high early-age temperatures • Delayed ettringite formation due to high curing temperature • Inadequate strength at formwork removal, prestressing, or loading

In all cases, the concrete structure may be damaged permanently and the durability, functionality, and appearance will be substantially reduced. On the other hand, it is also important to avoid using costly preventive measures that may unnecessary. By running simulations of alternative schemes before start-up of a project, engineers can arrive at economical solutions for reducing the risk of early-age damage.

The Be4Cast computer program is useful for: • Contractors, in planning construction methods to

meet specification requirements and economic limitations.

• Consultants, during the design phase where it is possible to check feasibility of planned construction activities.

• Precast concrete producers, for optimizing production schedules

Because Be4Cast is based on the finite-element method and modeling is in 3D, a wide range of problems can be solved. The computer-program is menu-driven and simple to use. Extensive knowledge of the finite-element method is not required. The information needed to run an analysis includes description of the construction method, thermal boundary conditions, and properties of the concrete that will be used. A mouse click starts the calculations, and various graphical outputs are available to check if the results are reasonable.

Construction Method Volumes corresponding to different placements are defined geometrically. Time of placement and the placement temperature are defined. Volumes are prismatic with arbitrary polygonal cross sections.

Materials The following properties define the hardening concrete: • Heat of hydration versus

maturity • Thermal conductivity • Heat capacity • Density

• Cement content • Activation energy • Tensile strength vs. maturity • Compressive strength vs.

maturity

• E-modulus vs. maturity • Poisson’s ratio vs. maturity • Coefficient of thermal expansion • Autogenous shrinkage • Creep function

Material properties can be imported from and exported to libraries. Thus the same material can be used in different analyses. The software includes ready-to-use default material properties.

Model of construction scheme in which the thick upper part of the wall is cooled

by water circulating through the previously cast foundation

Be4Cast

14

Thermal Boundaries The following conditions can be assigned to surfaces: • Temperature related to convection • Wind-speed • Thermal shields: user defined formwork,

insulation, etc. • Heat flux • Temperature related to radiation • Transmission coefficient related to radiation

All boundary conditions are functions of time. Internal heating or cooling can be modeled by specifying heating cables and cooling pipes (open circuits, closed circuits, and cooling plants can be specified). Thermal barriers can be imported from and exported to libraries, which allows the same materials to be used in different jobs. The software includes several ready-to-use thermal barriers.

Displacement Boundaries and External Loads The structure can be provided with displacement boundary conditions to model external restraints. Displacement boundary conditions are also used to specify planes of symmetry for reducing analysis run time. If insufficient displacement boundary conditions are supplied by the user, the software automatically provides boundary conditions so that the structure is statically determinate.

Calculation Method The analyses (thermal and stress) in Be4Cast are performed by means of the finite-element method. The structure is meshed into tetrahedrons. The variation of temperature and stress within elements is assumed to be parabolic.

Results The results from a Be4Cast analysis include the following parameters: • Temperatures • Maturities • Tensile and compressive

strengths • Stresses, principal stresses, and

tensile stress-strength ratio

Variations of given results within the structure are presented as contour plots at user-defined cross sections (as shown to the right).

Variations of given results with time are presented as graphs of minimum and maximum values, average values, or values at user-defined points.

Cross sections with extreme values of the parameters can be located automatically.

Contours of longitudinal stress component at section shown on right. Half length-model is shown due to symmetry.

Example of Be4Cast input screen to describe formwork and curing procedures

BOND-TEST

15

Purpose The BOND-TEST is used to conduct a pull-off test in accordance with ASTM C1583, "Test Method for Tensile Strength of Concrete Surfaces and the Bond Strength or Tensile Strength of Concrete Repair and Overlay Materials by Direct Tension (Pull-off Method)." The obtained pull-off strength can be used for the following purposes: • To evaluate the in-place bond strength between a repair overlay and the substrate • To evaluate the in-place tensile strength of concrete or other materials • To evaluate the effect of surface preparation procedures on the tensile strength of the substrate

before applying a repair material or overlay • To estimate the in-place compressive strength of surface concrete using the following

approximate relationship between tensile strength ft (MPa) and compressive strength fc (MPa):

10c

tff =

Principle In the BOND-TEST, a disc is bonded to a prepared testing surface and the disc is pulled off after a partial core has been cut around the disc (extreme left in following figure). The pull-off force, F, is divided by the cross-sectional area of the partial core to obtain the pull-off strength fp:

2

4p

Ffdπ

=

where d is the diameter of the partial core.

F

BOND-TEST (a) Failure in substrate (b) Bond failure (c) Failure in overlay

The types of failures that can occur in a BOND-TEST are illustrated above. Failure in the substrate (a) indicates that the bond strength is greater than the tensile strength of the substrate. A failure at the interface (b) provides a measure of the tensile bond strength between the overlay and the substrate. A failure in the overlay (c) indicates that the bond strength is greater than the tensile strength of the overlay. During a test, it is very important that negligible bending is introduced to the disc by the loading system. Otherwise, low and erratic test results will be obtained.

Failure type (a) is the preferred one, as it shows that the bond strength of the overlay is greater than the tensile strength of the substrate. Note that failure occurs at the weakest link of the composite system, and one cannot predict which type of failure will occur. Only tests results with the same typ of failure should be averaged when computing the average pull-off strength.

The nature of the BOND-TEST has been investigated by finite element analyses (see Petersen, C.G., Dahlblom, O. and Worters, P., “Bond-Test of Concrete and Overlays,” Proceedings, International Conference on NDT in Civil Engineering, University of Liverpool, U.K., 1997). Failure in the BOND-TEST using a 75-mm disc was predicted to occur at a displacement of 0.02 mm to 0.03 mm and the nominal stress in the partial core before rupture is about 3 % lower than the uniaxial tensile strength of the substrate concrete.

BOND-TEST

16

Variability For 75-mm discs, the coefficient of variation of replicate test results is about 8 to 10 % on concrete with a maximum aggregate size of 38 mm. For 50-mm discs, the coefficient of variation is 14 to 16 %.

The BOND-TEST procedure

1. Surface planing The surface is ground with a diamond wheel to expose the aggregates and to obtain a plane surface. The center knob is removed with a separate grinder. The dry surface is steel brushed and any dust or powder is blown away. The suction plate is used to control the planing operation.

Diamond planing wheel unit

Electric drill

Suction plate

Vacuum

2. Bonding the disc A clean disc is bonded to the prepared surface using a rapid-curing adhesive (GRA). The GRA adhesive has a tensile strength of 10 MPa when fully cured, which takes 2 to 5 minutes at normal temperatures. The progress of hardening is observed in the pot in which the two-component GRA was mixed. In cold weather conditions, the concrete surface and the disc are heated with a heat gun to accelerate curing of the adhesive.

Vacuum

Centering plate

75-mm dia. disc

3. Partial coring A partial core is cut perpendicular to the surface; the bonded disc serves as a drill guide (the inner diameter of the coring bit is slightly larger than the disc diameter). The partial core is cut with the CORECASE (page 28). For tests to measure bond strength, the core is cut to a depth of 25 mm into the substrate or one-half of the core diameter, whichever is greater; for tensile strength of the substrate, cut to a depth of 25 mm.

Vacuum

Corecase housing

Water in

Waste water out

To spindle assembly and drill

4. Pull-off The disc is loaded in direct tension at a controlled rate using a calibrated hydraulic pull machine. The machine bears against a circular counter pressure ring positioned centrally on the planed surface. The peak force in kN is recorded and used to obtain the pull-off strength by dividing by the cross-sectional area of the partial core. The type of failure, (a), (b) or (c), as shown on the previous page, is recorded.

Counter pressure ring

Centering disc

Bearing ring of pull machine

Pull bolt w/ spherical

end

Pull off load measured by gage

The procedure and the special equipment used for the BOND-TEST ensure that the disc is loaded in direct tension without bending. Such bending may lower results by 20 to 50 %. The discs have sufficient stiffness to avoid distortion during testing. By bonding a clean disc on a planed, dry surface with the GRA adhesive, failure should not occur at the disc/overlay interface. Failure at the disc/overlay interface is an invalid test and must be repeated if the bond strength is to be evaluated.

BOND-TEST

17

Testing Examples

BOND-TEST being performed for quality control of the bond between a wear resistant overlay and a concrete slab; coring after bonding the 75- mm disc is shown (left), application of pull-off load (middle), and the bond

failure, type (b), between the overlay and the substrate (right) at 1.8 MPa

BOND-TEST being performed on granite

tiles in a subway station The bond of a repair on a balcony being

evaluated with BOND-TEST

BOND-TEST

18

The BOND-TEST Equipment and Ordering Numbers

B-10000 DSV-Kit: For surface planing, bonding the disc, and attaching the coring rig to produce the partial core without anchoring.

Item Order # Diamond planing wheel unit B-10010 Suction plate with valve and gauge B-10020 Two adjustable clamping pliers B-10030 Centering plate for 75 mm disc Optionally, centering plate for 50 mm disc

B-10040 B-10050

Vacuum pump with hose B-10060 Wrench, 17 mm B-10070 Small screwdriver B-10080 Attaché case B-10090

B-11000 BOND-TEST Preparation Kit: For removing the center knob after surface planing, cleaning the surface, bonding the discs, and heating the discs in cold weather conditions

Item Order # Grinder with cup stone B-11010 Heat gun B-11020 Steel brush B-11030 75 mm discs, 6 pcs Optionally, 50 mm discs, 6 pcs

B-11040 B-11050

GRA glue, box B-11060 Putty knife B-11070 Araldite epoxy (for acrylic-based materials) B-11080 Attaché case B-11090 Optionally: GRA glue, can with ½ kg powder B-11100 GRA liquid, bottle with 200 mL B11110

CORECASE CS-75: For producing the partial core.

Item Order # Coring rig with coupling CC-10 Handles for coring rig, 3 pcs CC-20 Coring bit, 75 mm x 110 mm CCB-75/110 Water pump with 2 hoses CC-30 Clamping pliers, adjustable, 2 pcs CC-40 Set of anchoring tools, 8 mm CC-50 8 mm expansion anchors, 20 CC-60 Chisel CC-70 Hammer CC-80 Corelifter, 75 mm diameter CC-90 Wrench, 14 mm CC-100 Measuring tape CC-110 Set of spare bearings for coring rig CC-120 Reinforcement locator CC-130 Manual CC-140 Attaché case CC-150

BOND-TEST

19

B-12000 BOND-TEST Pull Machine Kit Item Order #

Hydraulic pull machine with analog gauge

B-12010

Centering piece B-12020 Coupling L-16 Pull bolt L-17 Bolt handle L-19 Oil refilling cup L-24 Oil refilling bottle L-25 Large screwdriver C-149 Small screwdriver C-157 Calibration table B-12030 Manual B-12040 Attaché case B-12050

The hydraulic pull machine comes with a 0 to 25 kN analog dial gauge, with 0.5 kN least division. The pull machine needs to be calibrated once a year, or sooner, if it is serviced or damaged. The L-30 calibration unit on page 79 may be used for calibration

B-13000 BOND-TEST Pull Machine Kit Item Order #

Hydraulic pull machine with electronic gauge

B-13010

AMIGAS printout software L-13 Cable for printout L-14 Centering piece B-12020 Coupling L-16 Pull bolt L-17 Bolt handle L-19 Oil refilling cup L-24 Oil refilling bottle L-25 Large screwdriver C-149 Small screwdriver C-157 Calibration table B-13030 Manual B-13040 Attaché case B-13050

The hydraulic pull machine has a 0 to100 kN precision electronic gauge with memory for storage of test results (peak-value, time and date of testing). The peak-value is shown after a test has been completed. The internal accuracy of the gauge is 0.01 kN. The display shows the pull force in 0.1 kN digital increments. The pull machine needs to be re-calibrated once a year, or sooner, if serviced or damaged.

B-14000 BOND-TEST Pull Machine Kit Item Order # Hydraulic pull machine with electronic gauge

B-14010

AMIGAS printout software L-13 Cable for printout L-14 Centering piece B-12020 Coupling L-16 Pull bolt L-17 Bolt handle L-19 Oil refilling cup L-24 Oil refilling bottle L-25 Large screwdriver C-149 Small screwdriver C-157 Calibration table B-14030 Manual B-14040 Attaché case B-14050

The hydraulic pull machine has an automatic loading rate control and a 0 to 100 kN precision electronic gauge with memory for storage of test results (peak-value, time and date of testing). The peak-value is shown after a test has been completed. The internal accuracy of the gauge is 0.01 kN. The display shows the pull force in 0.1 kN digital increments. The pull machine needs to be re-calibrated once a year, or sooner, if serviced or damaged.

CAPO-TEST

20

Purpose The CAPO-TEST permits performing pullout tests on existing structures without the need of pre-installed inserts. CAPO-TEST provides a pullout system similar to the LOK-TEST system (page 75) for accurate on-site estimates of compressive strength. Procedures for performing post-installed pullout tests, such as CAPO-TEST, are included in ASTM C900.

Typical applications of the CAPO-TEST include the following: • Quality control of the finished structure • Verification of in-place strength when strength of standard-cured specimens fails to meet

acceptance criteria • Estimating residual strength of concrete in existing structures • Evaluation of fire-damaged structures • Integrity of structures

Principle When selecting the location for a CAPO-TEST, ensure that reinforcing bars are not within the failure region. The surface at the test location is ground flat and a 18.4 mm hole is cored perpendicular to the surface. A recess (slot) is routed in the hole to a diameter of 25 mm and at a depth of 25 mm. A split ring is expanded in the recess and pulled out using a pull machine reacting against a 55 mm diameter counter pressure ring. As in the LOK-TEST, the concrete in the strut between the expanded ring and the counter pressure ring is in compression. Hence, the ultimate pullout force F is related directly to compressive strength.

The test is performed until the conic frustum between the expanded ring and the inner diameter of the counter pressure is dislodged. Thus there is minor surface damage, which should be repaired for aesthetic reasons or to avoid potential durability problems.

Correlation and Accuracy of Estimated Strength Several investigations have shown that the pullout strength measured by the CAPO-TEST is essentially the same as the pullout strength measured by LOK-TEST. This equality is illustrated in the graph to the right, which includes data from four independent studies. The maximum aggregate size varied from mortar up to 40 mm. Thus the general correlations for the LOK-TEST shown on page 76 are also valid for the CAPO-TEST.

Based on testing experiences and laboratory studies, it has been found that the accuracy of the compressive strength estimated by the CAPO-TEST using the general correlations shown on page 76 is similar to results obtained with the LOK-TEST. For normal density concrete, the coefficient of variation of individual CAPO-TEST results is about 8 %.

25 mm

25 m

m

F 55 m

m

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70

Krenchel 1982Yun et al. SP-112, MSA = 40 mmYun et al. SP-112, MortarMeyer 1994Bellander 1983, MSA = 38 mmBellander 1983, MSA = 18 mm

CA

PO-T

EST

Forc

e, k

N

LOK-TEST Force, kN

Line of Equality

CAPO-TEST

21

Comparison with Core Strength An investigation on 10 bridges compared the strength of cores with strengths estimated on the basis of the CAPO-TEST and the rebound hammer test (ASTM C805). As shown in the following figure, strengths estimated by the CAPO-TEST were on average within 6 % of the core strength. This study confirms the inherent reliability of pullout testing for estimating in-place compressive strength.

Reference: Moczko, A., “Comparison Between Compressive Strength Tests From Cores, CAPO-TEST and Schmidt Hammer,” Wroclaw Technical University, Poland, 2002.

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50

CAPO-TESTRebound Hammer

Estim

ated

Str

engt

h, M

Pa

Core Strength, MPa

Line of Equality

Example Applications

CAPO-TEST being performed in parking garage to evaluate in-place

strength of suspect concrete

Routing recess for the expandable ring in preparation for CAPO-

TEST to evaluate surface strength of an industrial floor

slab

Expanded ring

View of valid CAPO-TEST of aslab. Note the well formed failure

ring on the surface of the slab.

CAPO-TEST

22

CAPO-TEST Equipment and Ordering Numbers

Inserts and Resizing Tool

C-112 CAPO expandable inserts

C-111 Resizing Tool

For resizing C-112 insert 2 to 3 times

CAPO-TEST Kits The CAPO-TEST kits includes C-101 Preparation Kit, the C-102 DSV-Kit and a pull machine kit, either the C-103 kit containing a pull machine with the 0 to 60 kN analog dial gauge or the C-104 kit containing a pull machine with the 0 to 100 kN digital gauge.

C-101 CAPO-TEST Preparation Kit This kit is used to drill the center hole and to cut the recess to accommodate the expandable insert. The kit also contains the unit for expanding the CAPO-TEST insert and other miscellaneous tools for conducting the test.

Item Order #

Counter pressure C-142 Expansion unit C-101-1 Water pump C-150 Recess router unit C-101-2 Distance piece, 25 mm C-136 Bottle w. CAPO-Oil C-143 Diamond drill unit C-101-3 Electric drill C-101-4 Wrench, 14 mm C-151 Wrench, 19 mm C-155

Item Order # Screwdriver C-149 Tweezers C-148 Plastic hose C-157 Marking chalk C-160 Pliers C-147 Allen key, 4 mm C-156 Wrench, 46 mm C-147-1 Wrench, adjustable C-147-2 Vernier caliper C-135 Attaché case C-160

C-102 DSV-Kit The kit includes the diamond planer, the suction plate, a vacuum pump, and the necessary tools for grinding the surface so that it is flat before drilling the center hole and routing the recess. The diamond planer, the diamond core drill unit, and the recess router are positioned in the recess of the suction plate for proper alignment and dimensional control.

Item Order #

Diamond planner C-102-1 Vacuum pump w. hose C-102-4

Centering brass tap C-102-5 Suction plate C-102-2

Item Order #

Clamping pliers, 2 C-102-3 Small screwdriver C-158 Wrench, 17 mm C-154 Plastic hose C-147 Attaché case C-161

CAPO-TEST

23

Two pull machines are available for the CAPO-TEST. These are the same machines as used for the LOK-TEST.

C-103 CAPO Pull Machine Kit The hydraulic pull machine comes with a calibrated 0 to 60 kN analog gauge. Alternatively, the instrument can be supplied with a 0 to 40 kN gauge (Order No. L-10-2) for testing up to 40-MPa concrete. The pull machine accuracy is within 0.6 %, exceeding the ±2 % requirement of ASTM C900.

Item Order # Hydraulic pull machine with analog gauge L-10-3 Oil refilling cup L-24 Oil refilling bottle L-25 Large screwdriver C-149 Small screwdriver C-157 Manual C-165 Attaché Case C-166

C-104 CAPO Pull Machine Kit The hydraulic pull machine has a calibrated 0 to100 kN precision electronic gauge with memory for storage of test results (peak-value, time and date of testing). The peak-value is shown after a test has been terminated. The internal resolution of the gauge is 0.01 kN, but the pull force is displayed to the nearest 0.1 kN.

Item Order # Hydraulic pull machine with electronic gauge L-11-1 AMIGAS printing software L-13 Cable for printer L-14 Oil refilling cup L-24 Oil refilling bottle L-25 Large screwdriver C-149 Small screwdriver C-157 Calibration table L-32 Manual L-33 Attaché Case C-104-1

Note: The calibration of the pull machines needs to be verified at least once a year, or sooner, if serviced or damaged. The L-30 Load Verification Unit shown on page 79 is available for this purpose.

CMD

24

Purpose The CMD system is used to monitor the opening and closing of a surface crack as well as relative lateral movement between the two sides of the crack as a function of time.

Principle With the CMD (Crack Monitoring Device), a three-point rosette, in the shape of an equilateral triangle with 50-mm side lengths, is bonded to the surface. Two of the rosette points are positioned parallel to the crack, and the third one is positioned on the opposite side of the crack approximately half the distance to the base line.

A B

C

B A

C

50 mm

Temperature and moisture related movements, measured between points A and B, together with crack movement measurements between points A and C as well as between points B and C are transformed mathematically into the opening or closing of the crack and into the relative lateral movement of the two sides of the crack.

The measurements are made manually with the CMD-200 using a caliper, or they can be made electronically with the CMD-300 using displacement sensors (LVDTs). The CMD-300 also has the option for remote monitoring from the office by means of a phone line.

Precision and variation The resolution of the displacement measurements is 0.01 mm and the coefficient of variation for replicate measurement on the same crack is 5 %.

Testing Examples

-0.20

-0.10

0.00

0.10

0.20

0.30

0.40

0.50

0 1 2 3 4 5 6 7

OpenLateral

Mov

emen

t, m

m

Months

The CMD-200 being used for measurement of crack movement caused by ASR

Opening and lateral movement of a crack measured over 6 months

CMD

25

The CMD-300 rosettes with LVDT sensors mounted. Computer display from the logging of the crack movement downloaded to a PC on-site or at the office

by a phone line CMD Ordering Numbers

CMD-200

CMD-300

Item Order #

Three rosettes CMD-210 Positioning plate, acrylic CMD-220 GRA glue, box CMD-230 Precision caliper, electronic CMD-240 Manual CMD-250

The CMD-250 manual contains the mathematical equations for calculating the crack opening or closing and the lateral movement based on the recorded distances between the rosette points.

Item Order # Case with electronics and phone line cord

CMD-310

Three point rosette mounted with LVDT sensors (illustrated top of page)

CMD-320

Positioning plate, acrylic CMD-330 Extension RS-232 cable CMD-340 GRA glue, box CMD-350 Set of anchoring tools CMD-360 Tube with silicone CMD-370 CMD-300 software, CD-ROM CMD-380 Manual CMD-390

COMA-Meter

26

Purpose The COMA-Meter (COncrete MAturity-Meter) is used to measure the maturity of newly cast concrete at a depth of 80 mm from the surface for the following purposes: • Estimating the compressive strength at an early age using a pre-established strength-maturity

relationship (see page 27 for illustration) • Timing of pullout testing with LOK-TEST for early-age strength measurement • Evaluating the effective in-place curing temperature

Principle A glass capillary contains a liquid for which the rate of evaporation varies with temperature according to the Arrhenius equation, which is the same function that is used to determine maturity of concrete from the temperature history. The closed capillary is placed on a card with a calibrated scale indicating maturity in equivalent age at 20 ºC. The card is attached to a cap threaded onto a transparent container. After the concrete is cast, the capillary tube is snapped at the zero mark on the scale, the cap is threaded in the container, and the container is pressed into the fresh concrete.

Absorption compound Liquid filled glass capillary

Scale attached to capCap threaded on container

Container

The temperature within the container will stabilize quickly with the temperature of the surrounding concrete. The liquid in the capillary tube evaporates at a rate determined by the temperature and time. The level of the liquid, readable on the scale, measures the maturity of the concrete stated in M20 units, which is the number of equivalent days of curing at 20 ºC.

0

50

100

150

0 50 100 150

Cal

cula

ted

from

Tem

pera

ture

, day

s

COMA-Meter, days

0

1

2

3

4

5

-10 0 10 20 30 40 50 60

ArrheniusCOMA-Meter

Equi

vale

nt A

ge a

t 20

o C, d

ays

Temperature, oC Comparison between COMA-Meter maturity and

maturity calculated from temperature readings (Source: Möller, G. “Evaluation of COMA-test,” Report

8335-1983, CBI, Stockholm, Sweden

Maturity calculated by Arrhenius equation compared with COMA-Meter readings after one actual day at

temperatures between -5 ºC and 50 ºC

COMA-Meter

27

Resolution and Accuracy The measuring ranges of the two types of COMA-Meters are 0 to 5 M20 days for the COMA-5 and 0 to 14 M20 days for the COMA-14. The scale allows the maturity to be estimated to within ±0.1 M20 days. The meter is accurate to within ±5 % compared with maturity values calculated from temperature readings as shown on the previous page. The activation energy E for the COMA-Meter is 40 kJ/mol.

Applications

0

10

20

30

40

50

0 5 10 15 20 25 30

Mixture AMixture BMixture C

Com

pres

sive

Ste

rngt

h, M

PaM

20, days at 20 oC

Maturity measured by the COMA-Meter before in-

place strength testing with LOK-TEST for early form removal.

Examples of pre-established strength- maturity relationships, allowing in-place strength estimation by

means of maturity.

COMA-Meter installed in concrete for strength

indication before stripping of forms in cold weather conditions.

COMA-Meter installed in a newly cast airport runway slab for evaluation of the timing of cutting

the joints.

COMA-5

Pack of five 0 to 5 M20 days COMA-Meters COMA-14

Pack of five 0 to 14 M20 days COMA-Meters

CORECASE

28

Purpose CORECASE is a portable light weight coring rig for quickly obtaining drilled cores that are accurate in diameter, have straight sides, and are perpendicular to the surface. In addition to determining in-place compressive strength, drilled cores can also be used for the following purposes: • Verification of flaws identified by NDT methods such as the s’MASH impulse-response

system; the DOCter impact-echo system; and the MIRA and EyeCon pulse-echo systems • Preparing a partially drilled core for conducting a pull-off test with BOND-TEST in accordance

with BS 1881:207 or ASTM C1583 • Other laboratory tests such as: rapid chloride penetration using the PROOVE’it system, bulk

conductivity using Merlin, air-void parameters using the RapidAir system, or for petrographic analysis

Principle A thin-walled coring barrel with a high-performance diamond bit is attached to a water-cooled drill rig weighing between 1.8 kg and 3.5 kg. The drill rig pushes the drill barrel forward concentrically thereby avoiding bending forces during drilling. A special plastic coupling is used between the electric drill and the coring barrel to reduce vibration of the bit, ensuring a long life for the diamond bit and a smooth core surface. The drill rig is kept securely perpendicular to the surface by adjustable clamps anchored to the surface or by a suction plate. The end result is a quickly drilled core that has a smooth surface, accurate diameter, and drilled perpendicular to the surface. Two versions are available: CORECASE CS-75 for a 75-mm core diameter and CORECASE CEL-100 for a 100-mm core diameter.

Example Applications

Coring with the CS-75 rig clamped to the surface The CS-75 coring rig attached to the suction plate

before conducting BOND-TEST

Coring with the CS-75 rig for inspection of cracks following chloride extraction

Coring with the CEL-100 rig to obtain specimen for testing with PROOVE’it for

chloride permeability

CORECASE

29

CORECASEG49 CS-75 (75-mm core) Item Order #

Optional suction plate with vacuum pump

Coring rig with coupling CC-10 Handles for coring rig, 3 pcs CC-20 Coring bit, 75 mm x 110 mm CCB-75/110 Water pump with 2 hoses CC-30 Clamping pliers, adjustable, 2 CC-40 Set of anchoring tools, 8 mm CC-50 8 mm expansion anchors, 20 CC-60 Chisel CC-70 Hammer CC-80 Core lifter, 75-mm diameter CC-90 Wrench, 14 mm CC-100 Measuring tape CC-110 Set of spare bearings for coring rig CC-120 Reinforcement locator CC-130 Manual CC-140 Attaché case CC-150

Optional items Suction plate CC-160 Vacuum pump CC-170 1150 W electric drill CC-180

CORECASE CEL-100 (100 mm core) Item Order #

Coring rig with coupling CC-15 Handles for coring rig, 3 pcs CC-20 Coring bit, 100 mm x 210 mm CCB-100/210 Water pump with 2 hoses CC-30 Clamping pliers, adjustable, 2 CC-40 Set of anchoring tools, 12 mm CC-55 12 mm expansion anchors, 20 CC-65 Chisel CC-75 Hammer CC-80 Core lifter, 100-mm diameter CC-95 Wrench, 14 mm CC-100 Measuring tape CC-110 Set of spare bearings for coring rig CC-120 Reinforcement locator CC-130 Manual CC-145 Attaché case CC-155 Optional 1150 W electric drill CC-180

Extension rods, 100 mm long, for drilling deeper than 110 mm (CS-75) or deeper than 210 mm (CEL-100) are available on request, Order # CC-190.

Additional coring bits For CORECASE CS-75 For CORECASE CEL-100

Core diameter × length Coring bit # Core diameter × length Coring bit # 25 mm × 110 mm CCB-25/110 25 mm × 210 mm CCB-25/210 35 mm × 110 mm CCB-35/110 35 mm × 210 mm CCB-35/210 50 mm × 110 mm CCB-50/110 50 mm × 210 mm CCB-50/210 75 mm × 110 mm CCB-75/110 75 mm × 210 mm CCB-75/210 100 mm × 210 mm CCB-100/210

CorroEye

30

Purpose CorroEye is used to monitor the corrosion rate of steel reinforcement in critical areas of a reinforced concrete element or structure by means of a post-installed sensor.

Principle The reinforcement in question is located and the cover depth and the bar size are measured with a covermeter, e.g., with the CoverMaster shown on page 33.

The CorroEye sensor is mounted on the surface above the reinforcement. A slot is cut into the surface; an ERE-Probe (page 55) is placed in the slot parallel to the surface and covered with mortar. An 8 mm hole is drilled to a depth of 25 mm and a mounting anchor is inserted into the hole and expanded. A firm connection to the reinforcement is made with an adaptor installed in another drilled hole. Electrical connections are made to the pulse generator and the data logger, which has input options for up to eight CorroEye sensors.

The 90 mm long CorroEye sensor has four 15 mm diameter contact points. The two outer points act as guard electrodes and the two inner points act as counter electrodes, as illustrated below.

The sensor measures, at pre-set time intervals, the corrosion rate by the same galvanostatic pulse principle as used for the GalvaPulse instrument (page 61). The readings are stored in a watertight data logger, which is also attached to the surface at a convenient location. The recorded data are downloaded on-site to a portable computer whenever required. Alternatively, the data logger has an option for connection to a mobile phone for remote monitoring. Each phone line can handle up to 200 data loggers by the RS 485 communication port.

Two types of sensors are available. The CorroEye Mark I is used on a vertical surface or on a horizontal surface where the sensor will not interfere with traffic or access. The CorroEye Mark II is used in all other cases and is covered with a thin layer of protective mortar.

CorroEye Mark I

Pulse Generator and Data Logger

ERE Probe

CorroEye Mark II

Pulse Generator and Data Logger

ERE Probe

Accuracy and variation The accuracy of the CorroEye is better than stated in the table on page 62 for actively corroding areas because the position of the reinforcement is known before the sensor is attached and the polarized area of the reinforcement is also better defined. The variation from sensor to sensor for measurements on reinforcement with the same corrosion rate is within ±10 %.

CorroEye

31

Testing Examples

The CorroEye Mark I sensor installed on a

vertical surface close to a construction joint in a parking garage (ERE-Probe is not shown

mounted)

Two CorroEye Mark II sensors on a bridge deck before application of a protective mortar overlay (ERE-

Probe is not shown mounted)

The CorroEye pulse generator and data logger unit

CorroEye Ordering Numbers

Item Order # CorroEye, Mark I sensor with 20 meter cable CE-MkI-20-100 CorroEye, Mark II sensor with 20 meter cable CE-MkII-20-110 CorroEye Pulse generator and data logger, box CE-PGDL-120 CorroEye PC card for downloading test results to a PC CE-PC card-130 Anchors, 8 mm, 20 pcs CE-140 Set of anchoring tools CE-150 ERE-Probe, with 3 m cable ERE-Probe-3

CorroWatch

32

Purpose CorroWatch is a monitoring system for early warning of the onset reinforcement corrosion. It can also be used to estimate the time before corrosion of reinforcement begins so that corrective measures may be taken early enough to minimize repair costs.

Principle The CorroWatch is a multi-probe device consisting of four black steel bars acting as anodes and a noble metal as the cathode. The bars are positioned at different elevations and when cast into concrete, CorroWatch allows determination of corrosion activity as a function of cover distance.

In addition, the ERE-Probe (page 55) may be cast into the concrete for monitoring the potentials of the four black steel anodes of the CorroWatch.

ERE-Probe

Anodes

By monitoring the potential drop of the four anodes as a function of time, the gradual penetration of the depassivation front can be tracked and the service life can be estimated reliably, based on the actual depth of the reinforcement.

Accuracy In terms of measuring the ingress of the depassivation front, the CorroWatch is just as accurate as if the penetration were monitored using normal black-steel reinforcement.

Testing Example

-250

-200

-150

-100

-50

0

0 5 10 15 20

Depth 1Depth 2Depth 3Depth 4

Pote

ntia

l, m

V (A

g/A

gCl)

Time, years CorroWatch measurements from a marine structure showing the advancement of the depassivation front

CorroWatch Ordering Numbers

Item Order # CorroWatch with 3 meter cables CW-3 CorroWatch with 5 meter cables CW-5 CorroWatch with 10 meter cables CW-10

CoverMaster

33

Purpose CoverMaster covermeters are used for the following purposes: • Locate reinforcing bars and metal cable ducts in concrete

structures • Measure the cover depth of reinforcement • Estimate the size of reinforcing bars • Locate other metal objects embedded in concrete

Principle CoverMaster instruments are based on the pulse-induction technique. A repetitive current pulse is applied to the coils in the search head (below left). During each pulse, current increases gradually in the coils but is turned off rapidly. The sudden end of the pulse causes a sudden collapse in the magnetic field produced by the coils, which induces eddy currents in a bar located within the coils’ influence zone. As the eddy currents decay, a decaying magnetic field induces a secondary current in the coils (below right). The instrument measures the amplitude of the induced current, which depends on the orientation, depth, and size of the bar. The search head is directional and maximum signal is obtained when the bar is aligned with the long axis of the search head. The pulse-induction technique is uniquely stable, is not affected by moisture in concrete or magnetic aggregates, and is immune to temperature variations and electrical interference.

Applied current pulse Magnetic field induced by decaying eddy currents in bar

Recommendations on the use of covermeters can be found in BS 1881:204

CoverMaster P3312

Basic features: • Large graphics display of cover depth • Signal strength indicator and variable

tone to identify proximity to bar • Precise indication of bar direction • Easy-to-use, menu driven instrument • Single-handed operation; search head

includes key function buttons • Maxpip™ mode (emits sound when

search head is over center of bar) • Under cover mode (emits sound

when minimum cover has been detected)

• International bar sizes included

CoverMaster

34

Basic Features (continued) • Quick release battery pack and charger • Can be used with different search heads (See below) • Includes standard search head, cable, carrying case, and instruction manual • Rechargeable battery pack

Optional Search Heads In addition to a choice of four search heads, the CoverMaster P3312 can also be used with half-cell probes to measure the half-cell potential (see page 85). A borehole probe is also available for locating a second layer of reinforcement or deeply embedded tendon ducts. The borehole probe can be switched from the “forward looking” to the “side looking” mode.

Standard

For general purpose use; maximum cover 70 to 95

mm

Narrow Pitch

For resolving closely-spaced bars; maximum

cover 60 to 80 mm

Deep Scan

Maximum cover 160 to 180 mm

Dual Search Head

For high strength and stainless steel

Borehole Probe

For measurement of second layer of

reinforcement and tendon ducts

Half-Cell Potential Kit

Cu/CuSO4 or Ag/AgCl

Sample Display

CoverMaster P3312 Models

Model B includes the basic features listed on previous page. Model BH inlcudes all of the features of Model B with the additional of capability to make half-cell potential readings Model SH includes all the features of Model BH plus the following: • Automatic bar sizing (autosize mode for quick estimate or orthogonal method for greater

accuracy) • Orthogonal mode bar diameter determination • Min-Max cover limits (enter minimum and/or maximum cover to check with specifications) • Data storage (up to 1000 individual cover measurements in linear sequence) • Software to upload stored data to PC

CoverMaster

35

Model TH includes all the features of Model SH plus the following: • Data storage up to 240,000 points • Linear and grid data storage (data stored in 2-D format) • User defined 2-D testing grid • Graphics plot and threshold plot

Model THD includes all the features of Model TH plus a stainless steel measurement probe.

CoverMaster P3312 Feature Comparison

Description Model

B BH SH TH THD

Rebar location, orientation and depth of cover ● ● ● ● ●

Cover thickness reading in mm and inches ● ● ● ● ●

Graphics display with backlight ● ● ● ● ●

Multiple language menu structure ● ● ● ● ●

Signal strength display ● ● ● ● ●

Interchangeable heads with LED and keypad ● ● ● ● ●

User selectable bar range sizes and numbers ● ● ● ● ●

Measurement sound modes: ● ● ● ● ●

Locate (tone increases as head approaches rebar) ● ● ● ● ●

Under Cover (tone only sounds for low cover) ● ● ● ● ●

Maxpip™ (tone only as head passes rebar center) ● ● ● ● ●

Half-cell potential capability ● ● ● ●

Autosize mode for bar diameter determination ● ● ●

Orthogonal mode for bar diameter determination ● ● ●

RS232 output to printer or PC ● ● ●

EDTS Excel Link Software ● ● ●

CoverMaster® Software ● ● ●

Statistics ● ● ●

Minimum and maximum cover limits ● ● ●

Date and time ● ● ●

Memory ● ● ●

Graphics plot ● ●

Threshold plot ● ●

Stainless steel probe ●

Rugged waterproof case (IP65) ● ● ● ● ●

Adjustable beep volume and earphone socket ● ● ● ● ●

Bar Diameter Ranges

Metric 5 to 50 mm in 21 values U.S. Bar Numbers #2 to #18 in 16 values ASTM/Canadian 10 to 55M in 8 values Japanese 6 to 57 mm in 17 values

CrackScope

36

Purpose The CrackScope CS-100 can be used for accurate measurement of the width of surface opening cracks as well as measurement of the depth of surface holes or irregularities.

Principle The CrackScope is a small size, lightweight and conveniently portable microscope with a 25× magnification. It has a build-in scale for crack-width measurement and another scale on the focusing adjustment ring for depth indication.

Resolution The magnification of the CrackScope is 25 times. The built-in 3-mm scale has a least division of 0.05 mm, allowing the width of cracks to be estimated within ±0.025 mm. Depth measurement is achieved by focusing at the bottom of a depression and then focusing at the perimeter of the depression. By reading the scale engraved on the focusing ring and the needle of the lens barrel, depths can be measured with an accuracy of ±0.05 mm.

Application Example

0 0.5 1.0 1.5 2.0 2.5 3.0

Ordering Number: CrackScope CS-100

Deep Purple and Rainbow Indicator

37

Purpose Deep Purple and Rainbow Indicator are used to determine the depth of carbonation in samples of field concrete. Carbonation depth can be used for the following purposes: • To evaluate the cause of corrosion when conducting corrosion surveys • To estimate service life where penetration of the carbonation front is critical • To monitor the effectiveness of procedures for re-alkalization of the cover layer • To make a rough estimate of concrete strength from the age of concrete and the relative humidity

Principle The natural alkalinity of cement paste in concrete results in a protective oxide coating on steel reinforcement that prevents the steel from rusting. When carbon dioxide (CO2) in the air penetrates into concrete, it reacts with the calcium hydroxide (CaOH2) in the cement paste producing calcium carbonate (CaCO3). This reaction is called carbonation, and it causes the alkalinity of the paste to decrease, that is, the pH decreases below its normal value of about 13. When the pH drops below 9, the protective oxide coating is destroyed and, in the presence of moisture and oxygen, the steel will corrode. Thus measurement of the depth of carbonation is an essential step for corrosion evaluation of a reinforced concrete structure.

To measure the pH of the cement paste, a freshly broken piece of concrete or a newly cut core is sprayed with the indicator, and allowed to dry. The approximate pH of the paste is indicated by colors as illustrated below.

Deep Purple Indicator Color:

pH: 8.5 to 9.5

Rainbow Indicator Color:

pH: 5 7 9 11 13

Accuracy The carbonation front measured with the Deep Purple Indicator represents where the cement paste has a pH within the range of 8.5 to 9.5 as shown above.

The results of the Rainbow Indicator were correlated with the depth of carbonation determined by petrographic thin section analysis for a wide range of concretes with varying slump, with or without calcium chloride or fly-ash, different water-cement ratios, varying degrees of consolidation and different finishing methods. The results were published in:

Campbell, D.H., Sturm, R.D. and Kosmatka, S.H., “Detecting Carbonation,” Concrete Technology Today, Vol. 12, No. 1, March 1991, Portland Cement Association, USA

The results indicated that the depth of carbonation determined from thin section analysis correlated with the depth where the Rainbow Indicator indicated a green color or pH of 9 as shown above.

On normal concrete, the depth of the carbonation front can be determined with an accuracy of ± 10 % to ± 15 %. Testing Examples

The depth of carbonation evaluated by the Deep Purple Indicator. An average depth of carbonation of 16 mm was measured.

Deep Purple and Rainbow Indicator

38

Shown in the photo to the left, the pH profile was evaluated by the Rainbow Indicator on a newly cut core. The first 2 to 3 mm from the surface is colored red to yellow indicating a pH of 5 to 7. The green color, corresponding to a pH of 9, is dominant at a depth from 4 mm to 7 mm. A pH higher than 11 is indicated by the blue and purple colors, deeper than 7 mm. Also note that some of the aggregates had a reddish color indicating a pH of 5.

The figure to the right illustrates the approximate relationship between depth of carbonation lc in mm, the compressive strength fc in MPa, and the age of the structure h in years for exposure to a 50 % relative humidity. In the example shown, the depth of carbonation was measured to be 16 mm for a 10-year old structure. This implies that the concrete compressive strength is about 25 MPa. Alternatively, the graphs, or the given equation, can be used for service life estimation, where service life is defined as when the carbonation front reaches the depth of the reinforcing steel. As an example, for a cover depth of 25 mm, if the depth of carbonation is 4 mm at the time of testing and the compressive strength is 25 MPa, the carbonation front will reach the steel (an additional penetration of 21 mm), in approximately 22 years. For a relative humidity different from 50 %, a correction factor has to be applied to the graphs.

Ordering Numbers

RI-7000 Deep Purple Indicator Set of 4 spray bottles, 80 mL each

RI-8000 Rainbow Indicator Set of 4 spray bottles, 80 mL each

Average relationships between depth of carbonation, compressive strength, and time of exposure in air at 50 % RH. Source: “The

Concrete Book,” CTO, Aalborg, Denmark

DK 5000

39

Purpose The DK-5000 determines the resonant frequency of prismatic or cylindrical specimens in accordance with the impact resonance method described in ASTM C215, "Test Method for Fundamental Transverse, Longitudinal, and Torsional Resonant Frequencies of Concrete Specimens." The impact resonance method is a simple test that determines the resonant frequency very quickly. Resonant frequency testing can be used for the following applications: • Determination of the dynamic elastic properties (modulus of elasticity, Poisson’s ratio, and shear

modulus of elasticity) • Monitoring damage as a result of exposure to accelerated weathering, such as cycles of freezing

and thawing in accordance with ASTM C666/C666 M • Quality control of manufactured products

Principle When a test specimen is subjected to mechanical impact, such as being struck by a hammer, it will vibrate at it natural or resonant frequency. The DK-5000 uses a small hammer to impact the test specimen and a small accelerometer to monitor the vibration of the specimen. By using the correct specimen support condition, the proper position of the impact point, and the correct location of the accelerometer, the resonant frequencies for different modes of vibration can be determined. The illustration below shows the locations of the specimen support(s), the impact point, and accelerometer position to measure the longitudinal, flexural, and torsional resonant frequencies. In the impact resonance method, the resonant frequency is determined by transforming the time history of the accelerometer signal into the frequency domain. The resultant amplitude spectrum will contain one or more peaks that correspond to the excited frequencies.

Impact Accelerometer

Longitudinal mode Flexural mode Torsional mode

The DK-5000 consists of a laptop computer, a data acquisition and signal conditioning system, the DK Tester software, a hammer, and an accelerometer. In addition, a test bench is provided for supporting the test specimen. The DK Tester software is used to set up the testing parameters, to input specimen size and mass, and display test results. In accordance with ASTM C215, the test is repeated three times on the same specimen. The software displays each test result, and calculates the average resonant frequency.

From the specimen mass, specimen geometry, and measured frequencies, equations given in ASTM C215 are used to compute the dynamic elastic properties.

DK-5000

40

DK Tester Software The DK Tester software displays each replicate test result. The graphs are the amplitude spectra obtained by transforming the recorded accelerometer signals into the frequency domain. The horizontal axis is frequency and the vertical axis is amplitude. The dominant peak represents the resonant frequency. In this example, the resonant frequencies from two replicate tests on the same specimen are both 6738 Hz, which indicates the highly repeatable nature of the impact resonance method. The green window indicates that the instrument is “active” and ready for the third replicate test. The software allows the user to compute the

dynamic modulus of elasticity (from transverse or longitudinal modes), the dynamic shear modulus of elasticity (from the torsional mode), and the dynamic Poisson’s ratio in accordance with ASTM C215.

Resolution The frequency resolution depends on the sampling frequency and the number of data points in the accelerometer signal. For example, for 1024 points at a sampling frequency of 20 kHz, the frequency resolution is 20 Hz.

DK-5000 Ordering Numbers

Item Order #

Laptop PC with data acquisition card and DK Tester software

DK5000-1

Accelerometer and cable DK5000-2

Impactor DK5000-3

Test bench DK5000-4

Manual DK5000-5

Specimen supported on test bench for measurement of longitudinal resonant frequency. Specimen is struck at end

opposite to transducer postion.

DOCter

41

Purpose The use of traditional stress wave methods, such as ultrasonic through transmission (page 105), to identify the presence of anomalies in structures requires access to both faces of a member. Furthermore, it is not possible to determine the depth to anomalies. These drawbacks are eliminated by using the impact-echo method, which requires access to only one surface. The impact-echo method is based on monitoring the periodic arrival of reflected stress waves and is able to obtain information on the depth of the internal reflecting interface or the thickness of a solid member.

The DOCter is a versatile, portable system based on the impact-echo method, and can be used for the following applications: • Measure the thickness of pavements, asphalt overlays, slabs-on-ground and walls • Detect the presence and depth of voids and honeycombing • Detect voids below slabs-on-ground • Evaluate the quality of grout injection in post-tensioning cable ducts • Integrity of a membrane below an asphalt overlay protecting structural concrete • Delamination surveys of bridge decks, piers, cooling towers and chimneystacks • Detect debonding of overlays and patches • Detect ASR damage and freezing-and-thawing damage • Measure the depth of surface-opening cracks • Estimate early-age strength development (with proper correlation) Principle A short-duration stress pulse is introduced into the member by mechanical impact. This impact generated three types of stress waves that propagate away from the impact point. A surface wave (R-wave) travels along the top surface, and a P-wave and an S-wave travel into the member. In impact-echo testing, the P-wave is used to obtain information about the member.

When the P-wave reaches the back side of the member, it is reflected and travels back to the surface where the impact was generated. A sensitive displacement transducer next to the impact point picks up the disturbance due to the arrival of the P-wave. The P-wave is then reflected back into the member and the cycle begins again. Thus the P-wave undergoes multiple reflections between the two surfaces. The recorded waveform of surface displacement has a periodic pattern that is related to the thickness of the member and the wave speed.

The displacement waveform is transformed into the frequency domain to produce an amplitude spectrum, which shows the predominant frequencies in the waveform. The frequency of P-wave arrival is determined as the frequency with a high peak in the amplitude spectrum. The thickness (T) of the member is related to this thickness frequency (f) and wave speed (Cp) by this simple approximate equation (see page 42):

2pC

Tf

=

The same principle applies to reflection from an internal defect (delamination or void). Thus, the impact-echo method is able to determine the location of internal defects as well as measure the thickness of a solid member.

Impact Transducer

P --T

Impact Transducer

Incident P-wave

Reflected P-waveT

Data Acquisition and Analysis

System

DOCter

42

Example The upper plot in this example shows the surface displacement waveform obtained from a test of a solid concrete slab. The figure below the waveform is the amplitude spectrum obtained by transforming the waveform into the frequency domain. The peak at 11.47 kHz is the thickness frequency. For a wave speed of 4240 m/s, this frequency corresponds to a thickness of 4240 /(2×11,470) = 0.185 m, or 185 mm.

Thickness Measurement by ASTM C1383 Accurate measurement of thickness requires knowledge of the in-place P-wave speed. ASTM C1383, "Test Method for Measuring the P-Wave Speed and the Thickness of Concrete Plates Using the Impact-Echo Method," permits two methods for obtaining the P-wave speed. One method is by determining the thickness frequency and then measuring the actual plate thickness at that point. The equation on page 41 is used to solve for Cp, i.e., Cp = 2 f T.

Alternatively, Cp may be determined by measuring the time for the P-wave to travel between two transducers

with a known separation. With the LONGSHIP two-transducer assembly, the transducers are placed 300 mm apart and the impactor is about 150 mm from one of the transducers one the line passing through the transducers. The distance L (300 mm) between the transducers, is divided by time difference Δt between arrival of the P-wave at the second and first transducers. In the figure shown on the next page, Δt was measured to be 67 μs, and the P-wave speed is 0.300 / 0.000067 = 4480 m/s. When the wave speed is determined by the surface measurement method, the resulting value is multiplied by 0.96 when it used to calculate thickness. Thus the correct equation for thickness calculation is:

0.962

pCT

f=

The explanation for this 0.96 factor can be found in the following reference: Gibson, A. and Popovics, J.A., 2005, "Lamb Wave Basis for Impact-Echo Method Analysis," J. of Engineering Mechanics (ASCE), Vol. 131, No. 4, April, pp. 438-443.

300 mm

Spacer

150 ±10 mm

Transducer 2Impact Transducer 1

Data Acquisition and Analysis

System

DOCter

43

Measurement of P-wave Speed The figure to the right is an example of the measurement of P-wave speed by using two transducers a known distance apart. The time of arrival of the P-wave at each transducer is determined as the point when the signal for each transducer rises above the background value. The Viking software allows the user to place cursors at the points corresponding to the P-wave arrivals, and calculates the value of Cp. In this case, the calculated speed is 4480 m/s, and 96 % of this value is 4300 m/s.

Detection of Internal Defects The P-wave generated by impact will reflect at interfaces within the concrete where there is a change in acoustic impedance, which is defined by the density and wave speed of a material. At a concrete-air interface, there is complete reflection of the P-wave, and this permits detection of internal defects such as delaminations, cavities, and honeycombed concrete. If the plan area of the reflecting interface is large, the impact-echo response will be similar to that of a solid plate except that the thickness frequency will be shifted to a higher value. If the defect is just large enough to be detectable, the amplitude spectrum will show two peaks: one corresponds to reflection from the interface and the other corresponds to the portion of the P-wave that travels around the defect and reflects from the opposite surface of the plate. By positioning the cursor at the frequency associated with the flaw, the flaw depth is shown by the Viking software. The frequency associated with the portion of the P-wave that travels around the defect will be shifted to a lower frequency value than the solid plate thickness frequency. This is because the wave has to travel a longer distance as it diffracts around the flaw. The frequency shift is a good indicator of the presence of a flaw if it is known that the plate thickness is constant.

Depth of Surface-Opening Cracks The DOCter can also be used to measure the depth of surface-opening cracks, using a time domain analysis. The LONGSHIP transducers are placed on opposite sides of the crack (as shown on in the sketch to the right) and impact is generated on the line passing through the transducers. When the P-wave reaches the tip of the crack, the crack tip acts as a P-wave source, a process called diffraction. The diffracted P-wave is detected by the transducer on the opposite side of the crack from the impact. By measuring the time interval between the arrival of the direct P-wave at the first transducer and the arrival of the diffracted wave at the second transducer, the depth of the crack can be calculated. The example shown is from testing a fire-damaged structure, and a crack depth of 87 mm was estimated for a time difference of 35 μs and a P-wave speed of 3155 m/s.

DOCter

44

Accuracy For P-wave speed determined by calibration with a known thickness, the error in thickness measured by the DOCter system is estimated to be within ± 2 %. This assumes that the same P-wave speed is applicable at all test points.

In the case of thickness measurement based on measuring the P-wave speed from surface measurements, the error in thickness dues to systematic errors associated with the digital nature of the measurements is about ± 3 %. This assumes that the P-wave speed is uniform with depth.

The depth of surface-opening cracks can be estimated within ± 4 %.

Testing Examples

Detection of cracks in large anchor

blocks of bridge Measurement of thickness of cast-in-place tunnel lining

Measurement of depth of surface-opening cracks in fire-damaged

slab

Detection of delaminations and

honeycomb in sewer pipe Measurement of P-wave speed by

surface method Testing for quality of grout

injection in cable ducts located by ground penetrating radar

DOCter

45

DOCter Ordering Numbers

The DOCter comes in two versions: the DOC-700 for flaw detection and thickness measurement; and the DOC-4000 for flaw detection, thickness measurement, crack depth measurement, and P-wave speed measurement. The Spider multiple impactor unit can be purchased as an option to increase the operating range of the systems.

DOC-700 The DOC-700 system is a one-channel system for thickness measurement and flaw detection. The P-wave speed is determined by testing over a solid portion of a plate with known thickness. The system includes a laptop computer, a data acquisition module, one Mark IV transducer with impactors, and software. The hardware components and computer are delivered in attaché cases (not shown).

Item Order #

Laptop computer DOC-10 Data acquisition module with USB cable DOC-20 Viking software, CD-ROM Data DOC-30 Mark IV transducer DOC-40 Star support with 5, 8 and 12 mm impactors DOC-60 Protection caps for transducer tips, 4 pcs DOC-80 Single cable DOC-90 Attaché case for Mark IV transducer DOC-120 Attaché case for laptop computer DOC-140 Manual for Viking software DOC-150 Operation manual for DOC-700 system DOC-160 Testing case studies DOC-170

DOCter

46

DOC-4000 The DOC-4000 system is a two-channel system that complies with the surface method for P-wave speed measurement given in ASTM C1383. Besides thickness determination and flaw detection, the DOC-4000 can be used to estimate the depth of surface-opening cracks.

Item Order #

Laptop computer DOC-10 Data acquisition module with USB cable DOC-20 Viking software, CD-ROM Data DOC-30 Viking LONGSHIP with long handle and two Mark IV handheld transducers

DOC-50

Star support with 5, 8 and 12 mm impactors DOC-60 Short handle for crack depth measurement DOC-70 Protection caps for transducer tips, 8 pcs DOC-80 Double cable DOC-100 Attaché case for LONGSHIP DOC-130 Attaché case for laptop computer DOC-140 Manual for Viking software DOC-150 Operation manual for DOC-4000 system DOC-160 Testing case studies DOC-170

Spider, Order # DOC-210

The Spider contains 8 spherical impactors, with diameters ranging from 2 mm to 15 mm. The frequency content covered by the Spider impactors is approximately 1.2 kHz to 100 kHz on a hard concrete surface. The Spider is placed adjacent to the Mark IV transducer as shown to the right.

DSS-TEST

47

Purpose The DSS-TEST is used to measure the direct shear bond strength of a carbon fiber reinforced polymer (CFRP) laminate bonded to concrete.

Principle CFRP laminates are used as external reinforcement to strengthen existing concrete structural elements. The laminates are bonded to the concrete with epoxy adhesives. The effectiveness of the CFRP laminates to act as external reinforcement relies on adequate shear bond strength with the concrete. The DSS-TEST (Direct Shear Strength-TEST) measures the shear bond strength of 50-mm wide CFRP strips with a 200-mm bonded length to a concrete element in-situ or in the laboratory.

The CFRP strip is bonded to the concrete element using the manufacturer’s recommended adhesive. The strip is bonded perpendicular to the edge of the concrete so that it extends 200 mm beyond the edge.

After the adhesive has cured, a pedestal is placed over the strip and made to rest against the edge of the concrete member.

The 200-mm length of the CFRP strip that extends beyond the member is bonded to a pair of gripping jaws using a fast-setting adhesive (GRA). The jaws are firmly tightened to the strip with transverse fasteners.

A pull assembly with an attached coupling device is connected to the jaws. The reaction to the applied tensile load is transferred to the pedestal through two reaction plates.

A hydraulic pull machine is attached to the coupling and rests against the reaction plates. The tensile load applied by the pull machine results in a shear stress at the CFRP/concrete bond line. The load is increased until rupture occurs between the CFRP strip and the substrate.

The ultimate load in kN is a direct measure of the anchorage force of the strip for the 200 mm bonded length.

Examples of test results have been published in: Jensen, A.P., Petersen, C.G., Poulsen, E., Ottosen, C. and Thorsen, T., “On the Anchorage to Concrete of Sika CarboDur CFRP Strips: Free Anchorage, Anchorage Devices and Test Results,” International Congress, Creating with Concrete, Dundee, Scotland, September 1999.

Variability The coefficient of variation of the ultimate load is about 5 % for replicate tests using the same concrete substrate.

200 mm

CFRP Strip

Pedestal Reaction plate

Coupling

Gripping jaw

200 mm

DSS-TEST

48

Testing Example

DSS-TEST being performed to determine anchorage load of bonded CFRP strips (left) and typical failures (right)

The DDS-TEST Equipment and Ordering Numbers DSS-500 Kit

Item Order # Jaw plates, 2 pcs DSS-510 Transverse fasteners, 4 pcs DSS-520 Pedestal DSS-530 Counter pressure DSS-540 Pull assembly DSS-550 Pull cylinder, 19 mm diameter DSS-560 Coupling C-141 GRA glue, box B-11060 Set of anchoring tools, 12 mm DSS-570 12 mm anchors, 20 pcs DSS-580 Manual DSS-590 Attaché case DSS-600

C-104 CAPO-TEST Pull Machine Kit As shown page 23, consisting of

Item Order # Hydraulic pull machine with electronic gauge, 0-100 kN, 0.1 kN digital division

L-11-1

AMIGAS printout software L-13 Cable for printout L-14 Oil refilling cup L-24 Oil refilling bottle L-25 Large screwdriver C-149 Small screwdriver C-157 Manual L-33 Attaché case C-104-1

Eddy-Dowel

49

Purpose The Eddy-Dowel is a rail-mounted system for accurate measurement of the position of dowel bars and tie bars used in jointed concrete pavements. The device was developed by MIT Mess- und Prüftechnik GmbH, Dresden, Germany, who named it the "MIT Scan-2." The measuring unit includes five computer controlled eddy current sensors. Data are acquired at a high sampling rate as the measuring unit is pulled along rail system resting on the pavement. The large amount of acquired data allows reconstruction of bar alignment, which can be compared with specification tolerances.

The main features of the Eddy-Dowel system include: • Bar depth and alignment can be measured immediately after concrete has undergone setting • Portable hand-held computer with wireless communication with the measuring unit for

immediate on-site analysis using MagnoNorm software • Comprehensive analysis and visualization of dowel alignment with desktop MagnoProof

software • Efficient inspection: up to 500, 16-m traverses per day • High precision; ±4 mm for depth and horizontal alignment; ±8 mm for longitudinal alignment

(side shift)

The Eddy-Dowel system has been evaluated by several departments of transportation in North America and it has been found to be capable of making highly accurate measurements of bar location and alignment. See the following reference:

FHWA Concrete Pavement Technology Program, "Tech Brief: Use of Magnetic Tomography Technology to Evaluate Dowel Bar Placement," FHWA-IF-06-002, October 2005, http://www.fhwa.dot.gov/pavement/pccp/pubs/06002/06002.pdf

Principle The Eddy-Dowel uses the pulse induction, eddy current technique to determine the distance to the bars (see page 33 for a description of this method). Because the measuring unit includes five sensors, a fast sampling rate, and an accurate distance sensing system, the acquired signals can be used to reconstruct accurate 3-dimensional images of the embedded bars. These images show the depth and alignment of the bars.

The age of the concrete does not affect the results, so it is possible to take measurements as soon as the concrete is strong enough to support foot traffic. The presence of iron in the aggregates does not interfere with the measurement process. Because measurements are based on sensing low amplitude magnetic fields, precautions are necessary to ensure that magnetic materials, such as steel-toed shoes, tools, and vehicles, are sufficiently distant from the measuring unit.

Method of operation The Eddy-Dowel field system includes three principal components: 1) the measuring unit, 2) a portable rail system; and 3) a handheld Pocket PC. Making a measurement of the bars crossing a transverse of longitudinal joint is simple and rapid.

First, the mobile rail system is placed on the pavement so that it is centered along the joint. The rail system is made of lightweight glass fiber reinforced plastic composite. Information about the testing location and type of bars is entered into the Pocket PC. The measuring unit is placed at the starting end of the rail system, and it is then pulled slowly over the rails at a steady speed (0.25 to 0.5 m/s).

Eddy-Dowel

50

Control of the measurement process and data acquisition is done by the Pocket PC, which communicates wirelessly with the measuring unit. During a scan, the acquired data are shown on the display of the Pocket PC for immediate feedback of data quality. After the scan is completed, the program MagnoNorm, running on the Pocket PC, calculates the positions of the bars and displays a table listing bar depth, bar spacing, and bar misalignment. The results can be printed immediately on-site. Detailed reports of the measurements and three-dimensional images of bar positions and alignment can be created with the post processing software MagnoProof. This Windows® based software allows rapid analysis of large quantities of data and includes tools for the analysis of bar alignments that deviate greatly from planned locations. It can also assist in analyzing the results of complex measurement situations such as crossing bars at the intersection of longitudinal and transverse joints.

Application Dowel bars are designed to allow load transfer across transverse joints cut into the slab but at the same time allow pavement sections to expand and contract freely. Tie bars serve the same functions across longitudinal joints. If the bars are not aligned properly these two functions are compromised and joint failures may occur. The following figure shows five types of misalignments that are of concern. Horizontal skew and vertical tilt are of especially problematic because they prevent the bars from slipping freely across the joint and introduce restraint forces that can lead to joint spalling and slab cracking.

The MagnoNorm software running on the Pocket PC analyzes rapidly the data acquired during a scan and provides a gray-scale image and a summary table of the results. The gray-scale image is a contour plot of signal amplitude (which is related to depth) as a function of distance from the starting point. The contour plot provides an overall assessment of relative bar depth and bar position. The image below on the left shows an example of a contour plot for bars with relatively uniform depth and alignment, but irregular spacing. By changing the intensity level of the display,

Horizontal translation

Longitudinal translation (side shift)

Horizontal skew

Vertical translation Vertical tilt

Planned position Actual position

PLAN

SECTION

Joint x

y

y

z

Rails provide precise scan Real-time display of scan Post processing report

Eddy-Dowel

51

different details can be viewed. The image on the right shows irregular contour plots due to variations of bar depth.

The table of results provides the following information about each bar: • Sequential bar number • Distance from the starting point of the scan • Average depth • Longitudinal misalignment (side shift) • Horizontal misalignment • Vertical misalignment • Distance between adjacent bars

Eddy-Dowel Specifications

Measurement Measurement range Accuracy Depth Side shift Horizontal translation Vertical translation

110 to 190 mm 80 mm maximum 40 mm maximum 40 mm maximum

± 4 mm ± 8 mm ± 4 mm ± 4 mm

Operating conditions Operating temperature Storage temperature Humidity Daily output

-5 to 50 ºC -10 to 50 ºC Operates on wet surfaces and young concrete 500 to 600 joints for 16 m joint length

Eddy-Dowel Ordering Numbers

Item Order # Measuring unit Size 1160 x 655 x 95 mm Weight 16.5 kg 12 V rechargeable battery (8 h operating time; 4 h recharging time) Carrying case Manual

ED-2001

Rail system Segment length 1 m Rail width 1.18 m Total length 10 m standard Wheeled cross ties Carrying case

ED-2002

Pocket PC Large battery pack Memory card USB cable MagnoNorm and MagnoProof software Manual

ED-2003

Eddy-Thick

52

Purpose Eddy-Thick is lightweight portable device for measuring the thickness of concrete slabs-on-ground. The device was also developed by MIT Mess- und Prüftechnik GmbH. The system uses metal targets that are placed on the supporting base before concrete is placed. After the concrete has hardened sufficiently to support the weight of a person, the instrument is used to locate the target and then to measure the thickness of the slab. Eddy-Thick can be used for the following purposes: • Measurement of pavement thickness in support of

performance-based specifications • Measurement of slab thickness for the purpose of

determining the stress-wave velocity of the concrete for use with stress-wave based methods for measuring thickness at other locations

• On-site quality control of pavement thickness

Principle Eddy-Thick is based on the pulse-induction technique that is used for measuring cover over reinforcing bars (see page 33). In this case, eddy currents are induced in a metal plate (target) resting on the base instead of reinforcing bars in the concrete. For a given target, the amplitude of the signal induced by the decaying eddy currents in the target is proportional to the distance from the surface to the plate. Targets can be round or rectangular pieces of aluminum foil or plates of aluminum or steel. The target material and target size will affect the amplitude of the response for a given concrete thickness. Before using the instrument, the operator uses the menu system to select the target from a pre-defined list. If a target is used that is not included in the pre-defined targets, a standardization procedure is required to define a correction factor to be applied to the depth calculated using a pre-defined target (see the FHWA reference at the end of this section).

The sensor head of the instrument is housed a three-wheeled enclosure that is rolled along the concrete surface. The head includes four sensors that make many measurements as the head passes over the target. From the multiple measurements and the known characteristics of the target, the depth of the target is calculated and shown on the LCD on the instrument handle. The depth measurement accuracy is 0.5 % of the measured value plus 1 mm. For example, for a 200 mm nominal depth slab, the measurement accuracy is ± 2 mm.

Because of the high sensitivity of the instrument, there should not be any other embedded metal objects within 1 m of the target plate. In addition, there should be no parked vehicles within 2 m and no construction equipment within least 4 m of the test point. Operators should not wear steel-toed shoes because they can affect instrument response. Measurement accuracy is not affected by wet surfaces and measurements can be made on hydraulic cement concrete or asphalt cement concrete.

Method of operation The targets are placed on the prepared base before concrete placement. The number and locations of targets depend on the purpose of the thickness measurements and should be stated clearly in the contract documents for the project. The size of the target to be used depends on the nominal

Eddy-Thick

53

thickness to be measured. The following circular targets made of 0.65 mm thick sheet metal are available for different slab thickness measurements:

Target ID Target Diameter, mm

Depth Measurement Range, mm

ST RO 07 70 15 to 120

ST RO 12 120 40 to 180

ST RO 30 300 120 to 350

Eddy-Thick can be operated in two modes:

• SEARCH—This mode is used to locate the approximate center of the embedded target. • MEASUREMENT—This mode is used to measure the depth of the target.

In the SEARCH mode, the sensor head is elevated above the concrete surface and moved across the surface in a sweeping motion as is done with a common "metal detector." The instrument is in a continuous sampling mode and the LCD shows a bar graph of the amplitude of each of the four sensors. When the head is located at the approximate center of the target, each bar will have equal amplitude.

After the target is located, the sensor head is positioned on the surface of the concrete at approximately 300 mm in front of the target edge. Eddy-Thick is then placed in the MEASUREMENT mode, and the search head is rolled over the target until the sensor head is about 1.8 m from the start position. During the scan, data are automatically recorded. When data recording is completed, the depth is calculated and displayed in the LCD. The following summarizes the measurement process:

SEARCH mode to locate target MEASUREMENT mode to measure thickness

Display of measured thickness

Eddy-Thick

54

Evaluations Eddy-Thick (also called MIT Scan T-2) was evaluated by the FHWA Concrete Pavement Technology Program and by Caltrans. In both cases, it was concluded that the device was easy to use and resulted in accurate thickness measurements (see References).

Eddy-Thick Specifications • Measurement range: 15 to 350 mm depending on target size • Accuracy: ±(0.5 % of measured thickness plus 1 mm) • Operating temperature range: -5 to 50 °C • Memory capacity: up to 16,000 test results • NiMH rechargeable batteries with approximately 8 h of operation • Interface for data transfer to PC

Eddy-Thick Ordering Numbers

Item Order #

Basic measurement system including: • Sensor head and control unit • Battery recharger • Microcontroller firmware • Carrying case and strap • User manual

ET-001

Cable for data transfer to PC ET-002

Software for data transfer to PC ET-003

Charging system for use with 12 V auto battery ET-004

Printer with charging unit and thermal paper ET-005

Targets: diameter • 70 mm • 120 mm • 300 mm

ET-ST R0-07 ET-ST R0-12 ET-ST R0-30

References FHWA Concrete Pavement Technology Program, 2009, "TechBrief: Determination of Concrete Pavement Thickness Nondestructively Using the Magnetic Imaging Tomography Technique," www.fhwa.dot.gov/pavement/concrete/pubs/hif09023/index.cfm Rao, S. and Kumar, T., 2007, "Final Report—Method to Determine Pavement Thickness Using Recommended Technology," Division of Engineering Services, Caltrans, Sacramento, CA.

ERE-Probe

55

Purpose The ERE-Probe is a reference half-cell that is embedded in concrete and can be used to: • Monitor the reinforcement potentials in critical areas for corrosion such as construction joints,

splash zones in marine structures, bridge decks, and bottoms of bridge columns exposed to ingress of chlorides

• Monitor the efficiency of cathodic protection • Monitor the ingress of the depassivation front, due to chloride penetration or carbonation, in

combination with installing the CorroWatch (see page 32)

Principle The ERE-Probe (Embeddable Reference Electrode) is a stable, long life reference electrode for monitoring the half-cell potential of reinforcement. It is based on a manganese dioxide electrode in a steel housing with a chloride-free, alkaline gel and having a porous cement plug at one end. The housing is made from a corrosion resistant material. Diffusion of ions through the porous cement plug is low because the pH of the alkaline gel corresponds to that of pore water in normal concrete. The diameter of the ERE-Probe is 20 mm and the length is 85 mm

Porous cement

plug Alkaline solution MnO2

In new structures, the ERE-Probe is attached to the reinforcement by plastic straps before placement of the concrete. In existing structures, a hole is drilled to the required depth and the ERE-Probe is embedded using an appropriate mortar. A high impedance voltmeter is used to measure the half-cell potential between the probe and the reinforcement.

Accuracy and variation At 23 °C in a saturated Ca(OH)2 solution, the potential of the ERE-Probe is +160 mV ±20 mV versus a saturated calomel electrode (SCE). The in-place operating temperature is from 0 °C to +40 ºC.

Over a long period of time, the variation of each ERE-Probe is within ±5 mV compared with the initial value at the same temperature and for the same electrolyte environment. The expected life time is 100 years.

Testing Example

The ERE-Probe attached to

reinforcement before placing concrete

ERE-Probe Ordering Numbers

Item Order # ERE-Probe with 3 meter cable ERE-Probe-3 ERE-Probe with 5 meter cable ERE-Probe-5 ERE-Probe with 10 meter cable ERE-Probe-10

The ERE-Probe comes with a calibration certificate stating the potential value measured at 23 °C in a saturated Ca(OH)2 solution versus a saturated calomel electrode (SCE).

EyeCon

56

Purpose EyeCon is a portable hand-held instrument for flaw detection and thickness measurement. It is based on the ultrasonic pitch-catch method and uses an antenna composed of an array of dry point contact (DPC) transducers, which emit shear waves into the concrete. Test results can be displayed as individual A-Scans (reflection amplitude versus time or depth) or as B-scans showing the cross section of the test object along a scan line. EyeCon can be used for the following applications: • Thickness measurement • Detection of voids in grouted tendon ducts • Detection of poor quality bond in overlays

and repairs • Detection of delaminations • Detection of voids and honeycombing in concrete members

Principle EyeCon is based on the ultrasonic pulse-echo method using transmitting and receiving transducers in a "pitch-catch" configuration as illustrated on page 87. EyeCon uses an antenna composed of 24 transducers arranged in a 4 by 6 array as shown to the right. Each transducer is independently spring loaded to conform to surface irregularities. As is shown below, the first three rows of transducers act as transmitters and the other three rows act as receivers. By using the multiple transmitters and receivers, the signal-noise ratio is improved because random reflections from aggregate particles will tend to cancel, while reflections from large concrete-air interfaces will be superimposed.

The averaged signal recorded by the receiving transducers is stored in the hand-held unit as a time-domain waveform. An example of such a waveform is shown at the top of the next page. In this case, the test was done on a solid concrete slab with a thickness of about 200 mm. The figure on the left side of the next page shows signal amplitude as a function of time (A-Scan). The three peaks are due to multiple reflections

of the pulse by the back wall (bottom) of the slab. The figure on the right is the rectified version of the signal in which the negative portion of the original signal is plotted as a positive signal. EyeCon allows the user to display the signal as recorded originally (left side) or as a rectified signal. The latter is preferred because it allows more detail in the display. These time-domain signals of the received pulse are used to measure the solid thickness or detect the presence of voids or cracks within the test object.

EyeCon

57

0 100 200 300 400 500 600

Am

plitu

de

Time, μs

A-Scan

0 100 200 300 400 500 600

Am

plitu

de

Time, μs

Rectified A-Scan

The key features EyeCon include the following:

• The use of a 4 by 6 array of point transducers to introduce into the concrete pulses of shear waves with a nominal center frequency of 50 kHz. The use of the array increases the signal-noise ratio at the test point.

• The transducers are spring loaded to conform to an irregular surface, and they do not require a coupling medium, that is, testing is done in the dry.

• The signals captured by the antenna are stored as a time-domain waveforms (A-Scans). • Signals captured in a 2-dimensionl scan can be displayed on the hand-held unit as a black and

white cross section of the test object (B-Scan) along each scan line. • Data can be transferred to a computer for subsequent analysis and construction of a 3-

dimensional view of reflecting interfaces with color to represent different signal amplitudes.

Method of operation The handheld unit includes a 320 by 240 pixel LCD with backlighting. Setup parameters for recording and displaying signals are entered using a menu system. These parameters can be stored in memory for reuse. A series of icons is used to select the active display mode for the instrument. There are two basic display modes for the EyeCon:

• A-Scan—This display mode is used to show the results of individual measurements. The amplitude of the received signal can be displayed as a function of time or as a function of distance (depth) if the shear-wave speed is known. The signal can be displayed in its actual form or in rectified form (preferred). There are two A-Scan display modes: REVIEW and ZOOM. These are described later.

• B-Scan—This display mode uses the stored A-Scan records to create cross-sectional views along scan lines. There are two modes available: BAND for displaying the cross section along a single scan line and MAP for displaying cross sections along a series of parallel scan lines. These are also described later.

To carry out an inspection of a concrete member, the user first lays out a 2-dimensional grid on the testing surface. The grid lines should have the same spacing (step) in both directions. The step spacing depends on the size of defects to be detected, with a smaller spacing for smaller defects. The long axis of the antenna is oriented perpendicular to the scan direction and data are recorded at each step along each scan line. The grid layout (step distance, number of steps per line, and the number of lines) is entered into the hand-held unit and that information is used in referencing the displayed test results to the testing position on the test object.

EyeCon

58

After the scanning is completed, the results can displayed be in two ways. The individual A-Scans can be analyzed or cross sections (B-Scans) along each scan line can be viewed. The following explains the approach used to construct a cross-sectional view of the test object and show the depth of reflecting interfaces. The signal at each test point is plotted with time in the vertical direction as shown in left hand figure (a). If the shear-wave speed in the concrete is known, the time axis

can be converted to distance from the surface by multiplying by one-half of the wave speed (because the travel time is for a round trip equal to twice the depth). If the shear wave speed is assumed to be 2400 m/s, the distance axis is as shown in figure (b). To construct a cross-sectional view, a threshold level of signal amplitude is chosen and a black dash is drawn at the depth where the signal exceeds the threshold amplitude. In this example, a low threshold is used and the second echo from the back wall is plotted. If a higher threshold were used, only the first back wall echo would be shown. This process is repeated for each signal along the scan line, and the end result is a 2-dimensional representation (or a B-Scan) of the locations of reflecting interfaces along each scan line. As shown on the right, each scan line has an associated B-Scan plane that can be viewed as shown below.

Examples of Display Modes

The following are examples of the various displays that are available in EyeCon.

REVIEW—This display mode shows the recorded signal at a single antenna position. The signal can be from one set of pulses or an average of several sets of pulses, depending on the set up of the instrument. Different display formats are available. In this case, the signal has been rectified and filled in. The horizontal axis is in units of time (microseconds), but it could also be displayed in units of distance if the wave speed is entered when the instrument is set up. Various measurements can be made such time to first peak or peak-to-peak interval. A portion of the signal can be selected for a more detail view by using an adjustable window and switching to the ZOOM mode.

EyeCon

59

ZOOM—This display mode shows the full signal in the top half of the display. The bottom half of the display is an expanded view of the portion of the signal within the selected window. The user defines the location and length of the window. The right side of the display shows the shear-wave speed entered during instrument setup. The depth and time corresponding to the position of the horizontal cursor is shown in the upper right corner.

BAND—This is one of the B-Scan modes that can be used after testing along a scan line is completed and the individual A-Scans have been stored. The scan line is defined by the number of steps and the step distance. There are five boxes in the display. The lower left shows the B-Scan for the scan line. The cursor can be used to select a test point along the scan line. The upper left box shows the A-Scan for the selected test point. The upper right box shows which point along the scan is selected (4), the step distance (50 mm), and the location of the selected point along the scan line (0.2 m). The middle box on the right is the amount of memory used. The lower right box shows the

wave speed entered during instrument set up.

MAP—This mode is used to review results acquired when a 2-dimensional testing grid is used. The upper left box shows the grid layout (5 lines, 5 steps/line). The horizontal cursor is used to select the scan line for which the B-Scan cross section is to be shown. The vertical cursor selects the step along a scan line for viewing the individual A-Scan. The lower left box is the B-Scan along the selected scan line. The lower right box shows the A-Scan for the test point defined by the two cursors. The positions of the horizontal and vertical cursors in terms of steps in each direction (and corresponding distance) are shown in the two remaining boxes on the right side of the display.

EyeCon

60

EyeCon Specifications • Dry point contact shear-wave transducers with ceramic wearing tip • 50 kHz center frequency • Transducers are spring loaded to conform to rough surfaces • Antenna array: 4 by 6 • Maximum testing depth: 600 mm • Error in depth measurement: less than 10 % • Rechargeable batteries • Time for one measurement and saving to memory: 10 s • Saves up to 200 non-rectified A-Scans • 320 × 240 pixel black and white LCD • Backlight illumination • A-Scan and B-Scan display • Operating temperature -20 °C to 45 °C • Connection for data transfer to computer • Software for 3-D visualization on PC

EyeCon Ordering Numbers

Item Order #

Hand-held unit with rechargeable battery and soft carrying case

EYE-1001

Antenna array (4 by 6) EYE-1002

Cables EYE -1003

Battery charger EYE -1004

AC adapter EYE -1005

Software on CD-ROM EYE -1006

User manual EYE -1007

Hard shell carrying case EYE -1008

Approximate dimensions of case and total mass of equipment 405 mm x 315 mm x 165 mm, 5.5 kg 16 in. x 12 in. x 6.5 in, 12 lb

GalvaPulse

61

Purpose The GalvaPulse is used to measure the corrosion rate of reinforcement in concrete for the following typical applications: • Monitoring corrosion activity in reinforced concrete structures • Service life estimation • Evaluating the efficiency of corrosion arresting measures such as application of inhibitors,

membranes, or electrochemical removal of chlorides • Condition surveys of suspect reinforced structures, especially structures in wet environments

where the classic potential mapping may provide misleading or insufficient information • Measuring corrosion activity in repaired areas

Principle The GalvaPulse evaluates the corrosion rate of reinforcement by measuring polarization resistance using the galvanostatic pulse technique, as described below.

Guard Ring

Sponge

Reference Electrode

Counter Electrode

-200

-100

0

100

200

300

0 1 2 3 4 5 6 7

Volta

ge, m

V

Time, s

IRo

IRP

Emax

Ecorr

A current pulse I is imposed on the reinforcement from a counter electrode placed on the concrete surface. A guard ring confines the current to an area A of the reinforcement below the central counter electrode.

The applied current is usually in the range of 5 to 400 μA and the typical pulse duration is 5 to 10 seconds. The reinforcement is polarized in the anodic direction compared to its free corrosion potential, Ecorr. The resulting change of the electrochemical potential of the reinforcement is recorded as a function of time using a reference electrode (Ag/AgCl). A typical potential response for reinforcement actively corroding is shown in the right figure above.

When the current is applied to the system, there is an ohmic potential drop IRo as well as change in potential due to polarization of the reinforcement, IRp. The polarization resistance of the reinforcement Rp is calculated by curve fitting to the transient portion of the potential data. By means of the Stern-Geary equation for active corrosion (Icorr = (26 A)/Rp) and Faraday’s law of electrochemical equivalence, the corrosion rate is estimated as:

Corrosion Rate (μm/year) = 11.6 Icorr /A

where A is the confined area (in cm2) of the reinforcement below the central counter electrode. The factor 11.6 is for black steel.

The value of Ro, the electrical resistance of the concrete between the counter electrode and the reinforcement, is also determined.

GalvaPulse

62

Variation and Accuracy The half-cell potential is measured to an accuracy of ±5 mV with the Ag/AgCl electrode. The electrical resistance is estimated to be measured with an accuracy of ± 5 %.

The accuracy of the corrosion rate estimation can only be evaluated by comparison with actual mass loss measurement of the reinforcement subjected to long term corrosion conditions. One such laboratory investigation produced the following comparison between corrosion rates calculated from measured mass loss measurements and from the GalvaPulse.

Corrosion Rate (µm/year)

Reinforcement Mass Loss GalvaPulse

A 53 36

B 56 29

A+B connected 55 61 Reference: Baessler, R. and Burkert, A., “Laboratory Testing of Portable Equipment,” Brite/Euram Project Integrated Monitoring System for Durability Assessment of Concrete Structures, BAM (Federal Institute for Materials and Testing), Berlin, Germany, 2001

The findings support the general conclusion that the GalvaPulse is accurate well within a factor of two for estimating the corrosion rate in anodic areas. In addition, other uncertainties should be taken into account when evaluating on-site test results, e.g., the actual area of the reinforcement being polarized and the variation over time in corrosion rates due variation in temperature and moisture conditions.

In passive regions (corrosion rates < 1 µm/year), the GalvaPulse will overestimate the corrosion rate by a factor of 3 to 4. Such areas are, however, not interesting in terms of corrosion.

In a long term field study, 30-year old bridge columns subjected to deicing salts were examined regularly over a 20-year period since corrosion began. The chloride levels and moisture content in the concrete of the bridge were high. When the last measurements were performed, the temperature was 15°C and the following test results were obtained.

0 3 0 60 90 1 20 1 50 180 21 0 24 0 27 0 3 00 330 3600

3 3

6 6

1 00

1 33

1 66

2 00

0-15 15 -3 0 30 -4 5 4 5-60 6 0-75 75-90

0 30 60 90 120 150 180 210 240 270 300 330 3600

33

66

100

133

166

200

1 8 -2 0 1 6 -1 8 1 4 -1 6 1 2 - 1 4 1 0 -1 2 8 -1 0 6 -8 4 - 6 2 -4 0 - 2

Dra in

0 30 60 90 120 150 180 210 240 270 300 330 3600

33

66

100

133

166

200

-5 0 0 --4 5 0 -4 5 0 - -4 0 0 -4 0 0 - -3 5 0 -3 5 0 - -3 0 0 -3 0 0 --2 5 0 -2 5 0 --2 0 0 -2 0 0 - -1 5 0 -1 5 0 - -1 0 0 -1 0 0 --5 0 -5 0 -0 0 -5 0 5 0 -1 0 0 1 0 0 -1 5 0

Corrosion Rate µA/cm2

Half Cell Potentials mV vs Ag/AgCl Resistance KOhm

210 to 230 μm/yr

-450 to -500 mV

0 to 2 kOhm

The fairly constant corrosion rate measured over the 20-yr period corresponds to a cross section loss of the reinforcement of 20 yeras times 0.22 mm/y = 4.4 mm. Removal of concrete at several locations at the bottom of the columns revealed approximately 4 mm cross section loss of the reinforcement.

GalvaPulse

63

The GalvaPulse Features • Reliable evaluation of reinforcement corrosion in anaerobic concrete environment • Lightweight, handheld equipment, easy to operate • Two operation modes: one for speedy measurement using only half-cell potentials and electrical

resistance (1 to 2 s/test), and another for corrosion rate, half-cell potentials and electrical resistance (5 to 10 s/test). The first mode is normally used to identify the anodic and the cathodic areas, while the second mode is used in anodic areas, where the corrosion rate is a decisive parameter to be measured

• Testing on rough or curved surfaces • Storage capacity of up to 20,000 records in the handheld computer • Easy-to-use Windows® based software for presentation of the test results in 2D or 3D color

graphics • Portable system including calibration unit and a check block with embedded stainless steel and

corroding black steel bars

Testing Examples

GalvaPulse corrosion rate measurement

at a leaking joint Highway bridge column being tested for

corrosion rate with the GalvaPulse

Corrosion activity being evaluated on a

bridge wall with the GalvaPulse GalvaPulse testing in progress for corrosion

activity of a heavily corroded column

GalvaPulse

64

Examples of the Graphic Displays to View GalvaPulse Data

3-D Plot of corrosion rate

3-D Plot of half-cell potential

Following testing, the handheld computer is connected to a PC with the installed Windows® based GalvaPulse viewing and reporting software. The records are transferred to the PC and data can be viewed using 2D or 3D graphic displays. Here we see 3-D displays of the corrosion rates(above), the half-cell potential (above right), and the electrical resistance (right). Such plots permit the display of a large amount of data in a concise manner for preparing test reports.

3-D Plot of resistance

The GalvaPulse-5000 Ordering Numbers Item Order #

The newly developed GP-5031 measuring cell ensures a long life for the half-cell electrode by keeping the tip moist during storage.

Handheld computer with installed GalvaPulse software and pulse generator

GP-5010

Calibration unit for pulse generator GP-5020 Measuring cell with 3 meter cable GP-5031 Sponge for measuring cell GP-5040 Reinforcement locator GP-5050 Reinforcement conductivity meter GP-5060 Cable for data transfer to PC GP-5070 Measuring cable GP-5080 Two adjustable reinforcement clamps GP-5090 Two reinforcement adaptors GP-5100 12 mm and 18 mm drill bits GP-5110 10 mm Allen key GP-5120 Sponge for grinding of electrode rings GP-5130 Hammer and chisel GP-5140 Measuring tape and chalk GP-5150 GalvaPulse data viewing and reporting software

GP-5160

Manual GP-5170 Attaché case GP-5180 Supplied separately with the GP-5000 Kit Cable drum with 15 meters of cable GP-5190 Check block with embedded a corroding bar and a stainless steel bar

GP-5200

Guardian

65

Purpose Guardian is a system to measure the temperatures, temperature differences and maturity values during hardening of a structure at critical locations, such as those identified by Be4Cast simulations (see page 13).

Guardian allows strength estimation at an early age as well, provided the strength-maturity relationship for the concrete mixture used in the structure has been established and programmed into the software.

Alarms stored in the Guardian software alert the operator if preset temperatures or temperature differences have been exceeded. The Guardian also permits automatic control of cooling or heating measures designed by Be4Cast simulations.

The Guardian can perform other monitoring and surveillance tasks such as recording wind speed, relative humidity, barometric pressure, water levels, strains, corrosion parameters, and crack movement. Any device providing an appropriate electrical output can be monitored.

Principle Thermocouples are installed at pre-established locations in the structure and connected to the data logger. The Guardian software is installed on a PC with a Windows® operating system. Temperatures are recorded by the data logger at desired time intervals from the time of casting. The data are transferred to a PC, either by a cable connection to the logger or by a wireless modem connection, allowing remote monitoring of the temperatures and other measured parameters.

Several users may be working on the same project simultaneously allowing, for example, setting up the measurement scheme at one site while at the same time monitoring in-situ measurements at another site.

Data logger

Cooling water outlet

Cooling water inlet

Modem

Network

Wall cast on cold foundation

Bridge deck

Data logger with modem

Guardian Guardian

Guardian

66

Data Logger The data logger is kept on-site in a watertight case, allowing it to operate in all kinds of weather conditions.

Each logger can accommodate up has 48 channels. The amount of data that can be recorded is limited only by the amount of RAM in the computer. The unit has a back-up battery ensuring continuous operation should a power outage occur.

Guardian Ordering Numbers

Item Order #

Guardian software G-3000

Thermocouple, 5 m, with protection cap, ready to use G-3200

Protection cap for thermocouple G-3250

Thermocouple wiring, 100 m (optional) G-3300

Data logger for 48 channel operation G-3500

Modem for wireless transfer of data by mobile phone G-3600

Antenna for wireless transfer of data G-3700

GWT

67

Purpose The GWT (Germann Water permeation Test) is used for on-site evaluation of • The water permeation of the skin-concrete in finished structure • The water permeation of masonry panels • The water tightness of construction joints and sealed control joints • Effectiveness of water proofing membranes

Principle

The GWT measures the permeation of water into the test surface under an applied pressure.

A pressure chamber containing a watertight gasket is secured tightly to the surface by two anchored clamping pliers or by means of a suction plate. Alternatively, the gasket may be bonded to the surface with an adhesive.

The chamber is filled with water and the filling valve is closed. The top cap of the chamber is turned until a desired water pressure is displayed on the gauge. As water permeates into the concrete, the selected pressure is maintained by means of a micrometer gauge pushing a piston into the chamber. The piston movement compensates for the volume of water penetrating into the material.

The travel of the piston as a function time is used to characterize the permeation of the test surface.

Application Examples 1. Permeation of Concrete Surface

High-performance concrete being tested with the GWT. The four adjacent conical holes are from the CAPO-TEST. At a pressure of 1 bar or 100 kPa (left photo), water was observed to penetrate through surface cracks. After grinding off a 1.5 mm layer of the surface, the test was repeated (right photo), and the pressure was increased to 5 bar or 500 kPa. No penetration through cracks was observed. A water flux of 1.3×10-5 mm/s was measured.

GWT

68

2. Effect of Curing on Permeability

Water permeability of concrete measured with the GWT for different water curing temperatures and silica fume (SF) contents. The water-cement-ratio of the concrete was 0.42 and the compressive strength was 40 MPa. The results show the benefit of silica fume in reducing permeability.

3. Masonry Permeability

The GWT is shown being used for testing the water tightness of a brick masonry wall. During rain and for a normal wind pressure, water penetrated the wall. The problem was shown to be the related to the brick units, not to the mortar joints. The brick units had been burned at a higher temperature than normal to produce the required color, but the higher temperature increased the permeability of the brick. GWT-4000 Kit Ordering Numbers Optional Items:

Item Order # Item Order # Pressure chamber unit with 0-1.5 bar* gauge

GWT-4010 Suction plate & vacuum pump

GWT-4230

Wrench for pressure lid GWT-4020 Hammer drill GWT-4240 Extra 0-6.0 bar gauge GWT-4030 GRA glue, box GWT-4250 Water filling cup GWT-4050

Adjustable clamping pliers

GWT-4060

Set of anchoring tools GWT-4080 Wrenches: 14 and 17 mm GWT-4090 Sealant tape GWT-4100 Bottles with boiled water, 3

GWT-4110

Gaskets, 10 mm thick, 4 GWT-4120 Gaskets, 15 mm thick, 4 GWT-4130 Manual GWT-4140 Attaché case GWT-4150

*1 bar = 100 kPa

0.000

0.005

0.010

0.015

0.020

0 10 20 30 40 50 60

0 % SF5 % SF10 % SF

Per

mea

bilit

y C

oeffi

cien

t, m

m2 /(s

bar

)

Temperature, oC

HUM-Meter

69

Purpose The HUM-Meter is used to monitor the internal moisture content in concrete for evaluation of: • The corrosion process of reinforcement, because moisture content is one of the parameters that

affects corrosion rate • The effectiveness of drying procedures for arresting the progress of harmful reactions, such as

ASR (alkali silica reaction), that depend on moisture • The effectiveness of methods used to dry the concrete substrate before application of a moisture

sensitive covering

Principle To measure internal moisture content, sensors are installed into holes drilled into the concrete. The system is based on measuring the electrical resistance between two graphite probes or between a graphite probe and the reinforcement. The measured resistance and the known distance between the probes (or between a probe and reinforcement) are used to calculate the resistivity of the concrete and the moisture content is determined using a calibration relationship. The calibration relationship can be established experimentally for a given concrete, or approximate empirical relationships can be used for common concretes.

The graphite probes are 12 mm in diameter and 20 mm long. The holes are drilled to the depth where moisture content is to be determined.

Precision and accuracy The accuracy of the moisture content measured by the HUM-Meter with graphite probes is ±1 % for concrete with a water-cement ratio of 0.50. For concretes with other w/c values, the accuracy has to be evaluated by specific correlations developed on cores. The coefficient of variation of replicate test results is about 5 %.

Testing Example

7.0

7.5

8.0

8.5

9.0

9.5

10.0

0 5 10 15 20 25 30

% M

oist

ure

at R

einf

orce

men

t

Time, months The effect of a surface treatment on a bridge column

measured over time with HUM-Meter Graphite Probes

HUM-Meter

70

The HUM-Meter and Ordering Numbers

Item Order # H-10000 HUM-Meter

Digital meter with AC converter H-10010 Cables, 2 pcs H-10020 Temperature probe H-10030 HUM-Graphite Probes, 10 pcs. H-10040 Bushings for surface installation, 10 pcs H-10050 Attachment pin, 20 mm long, 10 pcs H-10060 Attachment pin, 40 mm long, 10 pcs H-10070 Attachment pin, 140 mm long, 10 pcs H-10080 Probe installation shaft, 300 mm long H-10090 Silicone tube H-10100 Drill bits: 12 mm and 18 mm H-10110 Reinforcement locator H-10120 Reinforcement adaptor H-10130 Allen key, 10 mm H-10140 Rubber ball dust remover H-10150 Manual H-10160 Attaché case H-10170

ICAR Rheometer

71

Purpose The ICAR Rheometer is a rugged, portable instrument for measuring fundamental flow (rheological) properties of fresh concrete. The instrument was developed at the International Center for Aggregate Research (ICAR) located at The University of Texas at Austin to fill the need for a method to characterize the true flow behavior of concrete mixtures. The traditional methods of measuring slump or slump flow are not capable of characterizing the fundamental rheological properties of concrete during the processes of mixing, transporting, and placement. As a result, the true performance of innovative concrete mixtures cannot be measured with these traditional slump-based methods. The ICAR Rheometer provides, for the first time, a low-cost and simple to operate instrument that can be used for: • Research and development to characterize the influence of new materials on concrete rheology • Optimizing mixture proportions so that the resulting concrete flows readily but is resistant to

segregation (especially important for self-consolidating concrete) • On-site quality control

Principle Fresh concrete can be considered as a fluid, which means that it will flow under the action of shear stresses. The flow behavior of concrete can be represented by the following two-parameter relationship 0τ τ μ γ= + , which is known as the Bingham model: The parameter τo is the yield stress, and it represents the shear stress required to initiate flow. The slope of the line is the plastic viscosity, µ, and it affects the resistance to flow after the yield stress has been surpassed. These two parameters, which define the flow curve, provide a complete description of the flow behavior of a concrete mixture.

Concrete, however, is not a simple fluid because it displays thixotropic behavior, which means that the shear stress required to initiate flow is high when the concrete has been in an “at rest” condition, but a lower shear stress is needed to maintain flow once it has begun. This type of behavior is summarized in the schematic plot shown to the left, which shows the variation in shear stress with time for the case of a slowly applied shear strain. At the start, the shear stress increases gradually with time but there is no flow. When the stress reaches the static yield stress, the concrete begins to flow and the stress required to maintain flow is reduced to the dynamic yield stress. If the applied shear strain is

removed and the concrete is allowed to rest, inter-particle forces create a weak framework that restores the static yield stress. With time, the static and dynamic yield stresses increase as the effectiveness of water-reducing admixtures diminish and hydration proceeds, which is commonly referred to as “slump loss.”

Dynamic yield stress

Time

Shea

r str

ess,

τ, (

Pa)

Static yield stress

0τ τ μ γ= +

Shear strain rate, γ , (1/s)

Shea

r str

ess,

τ, (

Pa)

τ0

µ

1

ICAR Rheometer

72

The ICAR Rheometer is designed to characterize the static yield stress, the dynamic yield stress and plastic viscosity of the concrete. A high static yield stress is desirable because it reduces formwork pressure and increases the resistance to segregation. But for ease of pumping, placement, and self consolidation, a low dynamic yield stress is necessary. The dynamic viscosity provides cohesiveness and contributes to reducing segregation when concrete is flowing. The schematic plot to the right shows dynamic flow curves for conventional concrete and different types of self-consolidating concrete (SCC) mixtures. The conventional concrete has a high dynamic yield stress and additional energy (vibration) is needed for consolidation after the concrete is placed in forms. The self-consolidating mixtures all have low dynamic yield stress and will consolidate due to self-weight, but they have different rheological properties. The SCC with a high plastic viscosity (red line) will be sticky and difficult to finish. On the other hand, the mixture with low plastic viscosity (green line) will be prone to segregation. Thus by determining the dynamic flow curves of concretes with different mixture proportions and type of admixtures, and optimum balance between ease of flow and resistance to segregation can be realized. These types of determinations cannot be done using conventional slump-based tests.

Method of operation The ICAR Rheometer is composed of a container to hold the fresh concrete, a driver head that includes an electric motor and torque meter; a four-blade vane that is held by the chuck on the driver; a frame to attach the driver/vane assembly to the top of the container; and a laptop computer to operate the driver, record the torque during the test, and calculate the flow parameters. The container contains a series of vertical rods around the perimeter to prevent slipping of the concrete along the container wall during the test. The size of the container and length of the vane shaft are selected based on the nominal maximum size of the aggregate. The vane has a diameter and a height of 127 mm.

Two types of tests can be performed. The first is a stress growth test in which the vane is rotated at a constant slow speed of 0.025 rev/s. The initial increase of torque is measured as a function of time. The maximum torque measured during the test is used to calculate the static yield stress. The other type of test is a flow curve test to determine the dynamic yield stress and the plastic viscosity. The flow curve test begins with a “breakdown” period in which the vane is rotated at maximum speed. This is done to breakdown any thixotropic structure that may exist and to provide a consistent shearing history before measuring the Bingham parameters. The vane speed is then decreased in a specified number of steps, which is selected by the user but at least six steps are

Container Driver

Computer

Vane Frame

ICAR Rheometer

73

recommended. During each step the speed is held constant and the average speed and torque are recorded. The plot of torque versus speed of vane rotation is the flow curve.

The ICAR Rheometer software performs all the necessary functions: operates the driver, records the torque, computes test results, and stores data. For simplicity, the entire program is operated from a single screen as shown below. The user defines the test geometry and provides the test parameters to run the flow curve test. A simple press of the “Start” button initiates the tests, which takes less than 1 minute to complete.

Example results The figure on the left shows the results of a stress growth test. The peak torque and test geometry are used to calculate the static yield stress, which is displayed at the bottom of the computer display. The figure on the right shows the plot of the average torque and average vane rotation measured during six steps of decreasing vane speed. The software computes a best-fit line to the data and reports the intercept and slope as relative parameters. The software also computes the Bingham parameters: dynamic yield stress and plastic viscosity.

0

2

4

6

8

10

12

0 5 10 15 20 25 30

Torq

ue, N

-m

Time, s

Stress Growth Test

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Torq

ue, N

-m

Vane Speed, rev/s

Dynamic Flow Curve

Input test geometry

Define test parameters for flow curve test

Test results

ICAR Rheometer

74

ICAR Rheometer Specifications • Requires that concrete have slump greater than 50 to 75 mm, otherwise the concrete is too stiff

for testing by the apparatus • Nominal maximum size of aggregate: 32 mm for largest available container • Vane rotation speed: 0.001 to 0.6 rev/s • Performs static stress growth test and dynamic flow curve tests • Software control tests and computes static yield stress, dynamic yield stress, and plastic viscosity

in fundamental units • Test time: 1 minute

ICAR Rheometer Kit Ordering Numbers

Item Order #

Motor drive/torque meter unit RHM-3001

Power cord for motor drive/torque meter unit RHM-3002

Base plate for attaching motor drive/torque meter unit to container

RHM-3003

Container for 19 mm NMSA aggregate – standard (see below for other sizes)

RHM-3005

Four-blade vane for 19 mm NMSA aggregate Vane is 127 mm in height and diameter Overall length depends on NMSA (see

below for other sizes)

RHM-3009

USB cable to connect motor drive/torque meter unit to computer

RHM-3012

Laptop computer with installed software RHM-3013

Software on CD-ROM RHM-3014

User manual RHM-3015

Carrying case for laptop computer RHM-3016

Carrying case for Rheometer and accessories Container does not ship with case Weight of case and Rheometer kit – 19

kg

RHM-3017

Ordering numbers for container and vane for different nominal maximum size of aggregate (NMSA) Nominal Maximum Size of Aggregate

12.5 mm 19.0 mm 25.0 mm 32 mm

Container Diameter/Height

RHM-3004 280 mm/280 mm

RHM-3005* 305 mm/312 mm

RHM-3006 355 mm/380 mm

RHM-3007 405 mm/460 mm

Vane Overall length

RHM-3008 235 mm

RHM-3009* 240 mm

RHM-3010 290 mm

RHM-3011 330 mm

*Size provided if another size is not specified.

LOK-TEST

75

Purpose The LOK-TEST system is used to obtain a reliable estimate of the in-place strength of concrete in newly cast structures in accordance with the pullout test method described in ASTM C900, BS 1881:207, or EN 12504-3. Two principal uses of LOK-TEST are for: • Determining whether in-place concrete strength is sufficient for early application of loads, such

as due to formwork removal, application of prestressing. • Determining whether the in-place strength is sufficient for terminating curing and thermal

protection. • Evaluating the quality of the critical cover layer protecting the reinforcement in the finished

structure.

Principle A steel disc, 25 mm in diameter at a depth of 25 mm, is pulled centrally against a 55 mm diameter counter pressure ring bearing on the surface. The force F required to pullout the insert is measured. The concrete in the strut between the disc and the counter pressure ring is subjected to a compressive load. Therefore the pullout force F is related directly to the compressive strength.

Loading is performed either to a required force, in which case the test is nondestructive, or to the peak-load, which results in a slightly raised, 55-mm diameter ccrack on the surface.

The disc is cast into concrete either by attaching it to formwork before placing concrete or by inserting it manually into the fresh concrete. Various LOK-TEST inserts are available, as shown on page 77.

Correlation and Accuracy of Estimated Strength LOK-TEST provides an accurate estimate of in-place strength because the peak pullout force has a well-defined correlation to compressive strength measured using standard cylinders or cubes. More than 30 years of correlation experience from all over the world indicates close agreement, suggesting that one general correlation is applicable for all normal density concrete mixtures, as shown below. A different correlation, however, has been found for concrete made with lightweight (low density) aggregate.

0

20

40

60

80

100

120

0 20 40 60 80 100

Cyl

inde

r Str

engt

h, M

Pa

Pullout Load, kN

Cylinder Stength Correlations

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70

Cub

e St

reng

th, M

Pa

Pullout Load, kN

Cube Strength Correlations

Source: Petersen, C.G., “LOK-Test and CAPO-Test Pullout Testing: Twenty Years

Experience,” Conference on Non-Destructive Testing in Civil Engineering, Liverpool, UK, April 1997, British Institute of Non-Destructive Testing

25 mm

25 m

m

55 m

m

F

LOK-TEST

76

The general correlations shown in the following figure will provide sufficient accuracy for all normal density concrete mixtures. Project specifications, however, may require development of mixture specific correlations. In this case, ACI 228.1R can be be used to develop such relationships.

0

20

40

60

80

100

0 10 20 30 40 50 60 70 80

Com

pres

sive

Stre

ngth

, MP

a

Pullout Load, kN

General Correlations forCylinder and Cube Strength

fcube

= 0.76 F1.16

fcyl

= 0.69 F1.12

At the 95 % confidence level and for an average of 4 tests, the estimated compressive strength based on the LOK-TEST and the general correlations indicated above is within ± 6 % of the strength measured from tests of standard specimen (cylinders or cubes) for a maximum aggregate size of 38 mm. The coefficient of variation of individual LOK-TEST results is about 8 % for normal density concrete.

Example Applications

LOK-TEST being performed on a wall for quality control of the finished structure. “H” on the display

indicates the highest pullout force obtained. The L-40 Control Insert was used.

Testing for in-place quality control on a slab. The L-49 floating insert was used. Maturity was measured

with the COMA-Meter, shown in front of technician’s knee

LOK-TEST

77

LOK-TEST performed from the bottom of a slab, through the formwork, for safe and early form removal. The L-42 early stripping insert was used with the L-44 steel plate attached to a removable plug through a porthole in the formwork. The L-10-2 pull machine with analog display is shown. COMA-Meters are used for timing of the LOK-TEST.

LOK-TEST Inserts and Ordering Numbers LOK-TEST inserts are supplied in four different configurations (shown left to right below) and in two strength classes: 0 to 50 kN and 0 to 100 kN pullout force. • Control inserts for nailing to wooden formwork. The formwork has to be removed before testing. • Early stripping inserts, with a steel plate for attachment to a removable plug through a porthole

in the formwork, for use when testing has to be performed before the formwork is removed. • Disc and stem, only, for replacement of used inserts • Floating inserts for insertion into the top surface of newly cast concrete

0 – 50 kN Inserts 0 – 100 kN Inserts

Item Order # Item Order #

Control insert L-40 Control insert L-41 Early stripping insert with L-44 steel plate

L-42 Early stripping insert with L-44 steel plate

L-43

Disc and stem, thread locked and coated

L-45 Disc and stem, thread locked and coated

L-46

Floating insert L-49 Floating insert L-50

Inserts may be re-used provided the discs are thread locked to the stems and coated with a coating agent, L-29, before re-use. For complete pulling out of discs from the concrete, a separate travel ring, L-26, is available. For testing 0 to 100 kN inserts, a special high-strength pull bolt with flange is needed, L-17-1, along with the high-strength coupling device C-141.

LOK-TEST

78

LOK-TEST Kits and Ordering Numbers Three types of hydraulic pull machines are available in the L-10, L-11 and L-12 LOK-TEST kits.

L-10 LOK-TEST Kit The L-10 hydraulic, hand-operated pull machine comes with a calibrated 0 to 40 kN analog dial gauge. Alternatively, the instrument can be supplied with a 0 to 25 kN gauge (Order No. L-10-1) or a 0 to 60 kN gauge (Order No. L-10-3). The accuracy of the pull machine is within ± 0.6 %.

Item Order # Hydraulic pull machine with analog gauge (0 to 40 kN)

L-10-2

Centering plate L-15 Coupling L-16 Pull bolt L-17 Stem removal tool L-18 Bolt handle L-19 Adjustable pliers L-20 Oil refilling cup L-24 Oil refilling bottle L-25 Large screwdriver C-149 Small screwdriver C-157 Calibration table L-32 Manual L-33 Attaché case L-34

L-11 LOK-TEST Kit The L-11-1 hydraulic pull machine comes with a 0 to 100 kN precision electronic gauge that includes memory for storage of test results (peak-value, time, and date of testing). The peak-value is displayed after a test has been terminated. The internal resolution of the gauge is 0.01 kN. The display, however, shows the pull force to the nearest 0.1 kN.

Item Order # Hydraulic pull machine with electronic gauge

L-11-1

AMIGAS Printout software L-13 Cable for printout L-14 Centering plate L-15 Coupling L-16 Pull bolt L-17 Stem removal tool L-18 Bolt handle L-19 Adjustable pliers L-20 Oil refilling cup L-24 Oil refilling bottle L-25 Large screwdriver C-149 Small screwdriver C-157 Calibration table L-32 Manual L-33 Attaché case L-34

LOK-TEST

79

L-12 LOK-TEST Kit The L-12-1 pull machine features an automatic loading rate that ensures consistent testing speed in accordance with testing standards. The machine has a 0 to 100 kN precision electronic gauge with memory for storage of test results (peak-value, time, and date of testing). The peak-value is displayed after a test has been terminated. The internal resolution of the gauge is 0.01 kN. The display, however, shows the pull force to the nearest 0.1 kN.

Item Order # Hydraulic pull machine with electronic gauge

L-12-1

AMIGAS printout software L-13 Cable for printout L-14 Centering plate L-15 Coupling L-16 Pull bolt L-17 Stem removal tool L-18 Bolt handle L-19 Adjustable pliers L-20 Oil refilling cup L-24 Oil refilling bottle L-25 Large screwdriver C-149 Small screwdriver C-157 Calibration table L-32 Manual L-33 Attaché case L-34

Note: The LOK-TEST pull machines may also be used for other types of tests that require application of a tensile load. These include the following Germann Instruments test systems: the CAPO-TEST, the BOND-TEST, the TORQ-TEST, the DSS-TEST and the POWER. The recommended pull machine for all the tests is the L-11-1 hydraulic pull machine supplied in the L-11 LOK-TEST Kit.

Load Verification Unit The calibration of a pull machine needs to be verified at least once a year, after servicing, and after repair. The L-30 Load Verification Unit has a working range of 0 to 100 kN. The load is displayed to the nearest 0.1 kN. The unit comes with a certificate verifying the accuracy of its calibration. The L-30 unit ensures that the load displayed by the pull machine is within ±2 % of the actual load, as required by ASTM C900.

Merlin

80

Purpose The Merlin is one of the newest developments by Germann Instruments. It is used to measure the bulk electrical conductivity, or its inverse, the bulk electrical resistivity, of saturated 100 by 200 mm concrete cylinders or cores. The test is simple to perform and a test result is obtained within two seconds. The conductivity of a saturated concrete specimen provides information on the resistance of the concrete to penetration of ionic species by diffusion. Merlin can be used for the following purposes: • Research and development to characterize

the influence of new materials on the electrical conductivity of concrete

• Optimizing mixture proportions and supplementary cementitious materials to increase concrete service life

• On-site quality control and quality assurance • Evaluation of in-place concrete (using cores).

Principle The electrical resistance R of a conductor of length L and uniform cross-sectional area A is given by the equation shown in the figure to the right. The quantity ρ is called the electrical resistivity and is a material property, with units of resistance multiplied by length, such as ohm·m. If the electrical resistance R of a specimen is measured, the resistivity can be calculated from the relationship ρ = R A/L. The inverse of electrical resistivity is the electrical conductivity, σ. The inverse of ohms is a unit called siemens (S). Therefore, electrical conductivity has units of S/m. For concrete, it is convenient to express conductivity in millisiemens per meter or mS/m.

In assessing the ability of a concrete mixture to resist penetration of a particular type of ion, one of the key properties is the diffusivity, which defines how readily the given type of ion will migrate through saturated concrete in the presence of a concentration gradient. For a saturated porous material, such as hardened concrete, the diffusion coefficient of a give type of ion can be related to electrical conductivity through the Nernst-Einstein equation as follows (Snyder et al. 2000; Nokken and Hooton 2006):

p w

DD

σσ

= (1)

where σ = bulk electrical conductivity of the saturated porous material σp = conductivity of the pore fluid D = bulk diffusion coefficient of the specific type of ion through the porous material, and Dw = diffusion coefficient of the specific ion through water (Mills and Lobo 1989). If the conductivity of the pore fluid is assumed to be similar among different concretes, the measured bulk electrical conductivity is related directly to the bulk diffusion coefficient (Berke and Hicks 1992). Measurement of the bulk diffusion coefficient of a particular type of ion through concrete is a time consuming process, while electrical conductivity can be measured in a matter of seconds.

The electrical conductivity of saturated cement paste is related to the paste porosity (volume of pores and how they are connected). The paste porosity is in turn related to the degree of hydration, the types of cementitious materials, and the water-cementitious materials (w/cm) ratio. If electrical measurements are made at a fixed degree of hydration for a given system of cementitious materials, the measured conductivity is related to the w/cm.

L

A LRA

ρ=

Merlin

81

Method of operation The following is a schematic of the measurement method incorporated in Merlin. The four-point measurement method that is used provides an accurate measure of specimen resistance by minimizing the effects of the conductive sponges and the pressure applied to the electrodes. The specimen must be in a water-saturated condition to obtain a meaningful measurement.

An alternating current source is used to apply current through the saturated cylinder or core. A voltmeter is used to measure the voltage drop across the specimen, and an ammeter measures the current. From the measured current I and voltage V, the bulk conductivity is calculated as follows:

I LV A

σ = (2)

where, L is the specimen length and A is the specimen cross-sectional area. The bulk resistivity is the inverse of the bulk conductivity, that is, ρ = 1/σ.

A 100 by 200 mm verification cylinder is provided to check that the Merlin system is operating correctly. The cylinder includes a push button switch than can be used to select one of several precision resistor from 10 Ω to 1 MΩ. For example, if the 1000 Ω resistor is selected and the system is functioning correctly, the conductivity reading of the verification cylinder should be 25.46 mS/m

and the resistivity should be 39.27 Ω•m.

Application From the theoretical basis of the Merlin, it can be seen that measurement of the bulk electrical conductivity of a saturated concrete specimen provides an indication of the diffusivity properties of the concrete. If the test is conducted at a consistent degree of hydration for a given combination of cementitious materials, the variation in measured bulk electrical conductivity can be used as an indicator of variation of w/cm using a pre-established correlation. If the bulk electrical conductivity of the approved concrete mixture for a project is known, that value can be used for quality control and quality assurance. Thus Merlin can be considered as a surrogate test to verify the w/cm of a specimen.

The bulk conductivity measured with Merlin is related directly to the charge passed through a specimen as measured by ASTM C1202 using the PROOVE’it system, provided that the current remains constant during the 6 h test duration. This is typically not the case for highly conductive concretes due to electrical heating of the specimen, which increases the pore fluid conductivity and the current. If we assume that current is constant during a PROOVE’it test, we can convert the

Current source

A Ammeter

V

Voltmeter

Gap

Sponge

Merlin

82

0

2000

4000

6000

8000

10000

12000

0 10 20 30 40 50 60

L = 100 mm L = 50 mmEq. 3Eq. 3

Cha

rge

Pas

sed,

C

Conductivity (Initial RCPT), mS/m

ASTM C1202 coulomb limits for the different categories of "chloride ion penetrability" into bulk conductivity limits using the following relationship:

QLVtA

σ = (3)

where Q = charge passed in the PROOVE’it test V = applied voltage in the PROOVE’it test (60V) L = length of the PROOVE’it specimen A = area of the PROOVE’it specimen t = measurement time (6 h = 21,600 s) of the PROOVE’it test The bulk resistivity limits can also be calculated by taking the inverse of the above equation.

For a specimen length of 50.8 mm and a diameter of 95 mm (the reference dimensions specified in ASTM C1202), the conversion from charge passed using ASTM C1202 to bulk conductivity (Eq. 3) and bulk resistivity values is as follows:

Charge passed using PROOVE’it, Coulombs†

Merlin Bulk Conductivity mS/m

Merlin Bulk Resistivity Ω·m

50 0.28 3636 100* 0.55 1818

1,000* 5.50 181.8 2;000* 11.00 90.89 4,000* 22.00 45.45 10,000 55.01 18.18

†It is assumed that current is constant during the 6 h test duration, which is typically not true for high conductivity concrete *Limiting values in ASTM C1202 used to define different categories of "chloride ion penetrability" (see page 101)

Test Data

Snyder et al. (2000) measured the charge passed through 100 mm diameter cylindrical specimens in accordance with ASTM C1202 and used the initial current during the test to calculate the bulk conductivity according to Eq. 2. This calculated bulk conductivity is based on the same principle as used by Merlin. The cylinders had lengths of 50 and 100 mm. The graph on the left shows the charge passed versus the bulk conductivity. The solid lines represent the theoretical relationships between charge passed and bulk conductivity as given by Eq. 3. It is seen that there are approximately linear relationships between charge passed and bulk conductivity. The measured charges passed are,

however, greater than predicted by Eq. 3. This can be explained, in part, by heating of the specimens. The concretes used by Snyder et al. (2000) had relatively high conductivities. As explained above, specimens with high conductivity will heat up during the ASTM C1202 test. As specimen temperature increases, the conductivity of the pore fluid increases and the current increases. This leads to instability and a higher charge passed compared with a specimen kept at a constant temperature.

Berke and Roberts (1989) also measured charge passed (AASHTO T-277, which is similar to ASTM C1202) and specimen resistivity based on a polarization method. In this case the concretes that were

Merlin

83

0

500

1000

1500

2000

0 2 4 6 8 10 12 14

DataEq. 3

Cha

rge

Pas

sed,

C

Conductivity, mS/m

used had relatively low conductivities. The graph to the left shows the Coulomb values reported by Berke and Roberts (1989) plotted versus the inverse of the reported resistivity values (conductivity) and the prediction based on Eq. 3. Again there is an approximately linear relationship between conductivity and charge passed. In this case, however, the data fall below the prediction based on Eq. 3. This difference is likely due to the method used to measure resistivity. In summary, these studies confirm the expected strong relationship between bulk conductivity and charge passed using ASTM C1202.

Specimen Conditioning and Test Interpretation An electrical conductivity test will provide an indication of the diffusivity of the concrete only if the specimen is saturated. Thus it is essential that cylinders be kept under water from the time of molding until time of testing. Reusable steel molds are available to provide specimens of consistent dimensions and to facilitate storage under water. Except for the ends, the cylinder should be in a surface dry condition at time of testing. Special caps are available to keep the cylinder ends wet while the surface is allowed to dry. Because of the high sensitivity of the measurement method, the cylinder must be supported on an insulated stand during the measurement. The conductivity of the pore solution affects the measured bulk conductivity of concrete. Thus comparisons should not be made between concretes with very different pore solution conductivities. For example, the use of calcium nitrite as a corrosion inhibitor will increase the conductivity of the pore fluid, and the measured bulk conductivity of the concrete will be higher than for another concrete without calcium nitrite but with a similar diffusivity. On the other hand, concrete with supplementary cementitious materials may have a reduced pore fluid conductivity, which will reduce the measured bulk conductivity while the actual diffusivity may not be reduced (Liu and Beaudoin 2000).

References Berke, N.S. and Hicks, M.C., 1992, "Estimating the Life Cycle of Reinforced Concrete Decks and Marine Piles Using

Laboratory Diffusion and Corrosion Data," Corrosion Forms and Control for Infrastructure, ASTM STP1137, pp. 207-231, http://www.astm.org/DIGITAL_LIBRARY/STP/SOURCE_PAGES/STP1137.htm

Berke, N.S. and Roberts, L.R., 1989, "Use of Concrete Admixtures to Provide Long-Term Durability from Steel Corrosion," Third CANMET/ ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Ed. V.M. Malhotra, Ottawa, Canada, October 4-6, 1989, ACI SP 119, American Concrete Institute, p. 383-403.

Liu, Z. and Beaudoin, J. J., 2000, “The Permeability of Cement Systems to Chloride Ingress and Related Test Methods,” Cement, Concrete, and Aggregates, CCAGDP, Vol. 22, No. 1, June, pp. 16–23. http://www.astm.org/DIGITAL_LIBRARY/JOURNALS/CEMENT/

R. Mills and V. M. M. Lobo, 1989, Self-Diffusion in Electrolyte Solutions, Elsevier, New York. Nokken, M,R, and Hooton, R.D., 2006, "Electrical Conductivity Testing," Concrete International, October, pp. 58-63,

http://www.concreteinternational.com/pages/index.asp Snyder, K.A., Ferraris, C. Martys, N.S. and Garboczi, E.J., 2000, "Using Impedance Spectroscopy to Assess the Viability of the

Rapid Chloride Test for Determining Concrete Conductivity," J. Res. Natl. Inst. Stand. Technol. 105, pp. 497-509, http://nvl.nist.gov

Merlin

84

Merlin Specifications • Specimen diameter 90 to 110 mm • Specimen length up to 200 mm • 325 Hz AC current supply • Measurement time: approximately 2 seconds • Sampling rate 5 Hz • Test results in terms of bulk conductivity or resistivity • Test results can be stored for preparing test reports

Merlin Ordering Numbers

Item Order #

Merlin bulk conductivity cell MRLN-1001

Netbook computer with software installed MRLN -1002

Merlin software MRLN-1003

Merlin verification cylinder MRLN-1004

Insulating specimen support MRLN-1005

Caps to prevent drying of ends of cylinders MRLN-1006

Spray bottle MRLN-1007

Carrying case MRLN-1008

Precision steel mold, reusable MRLN-1009

Precision steel mold

The MRLN-1009 precision steel mold produces cylinders with a diameter of 100 mm and a length of 200 mm with an accuracy of 0.02 mm on the cylinder dimensions. The steel mold is reusable and mold removal is simple. To remove the mold, the top and bottom lids are removed first. Then, the container is opened slightly by applying a small pressure with the screws in the welded flanges. The mold allows specimens to be produced within the tolerances stated and with plane end faces that are perpendicular to axis of the specimen. This minimizes test variability due to specimen geometry.

Mini Great Dane

85

Purpose The Mini Great Dane is used to measure the half-cell potential of uncoated reinforcing steel in concrete (in accordance with ASTM C876) and to measure the electrical resistance of the cover concrete. Typical applications include the following: • Condition surveys of suspect reinforced concrete

(RC) structures to identify areas with corrosion activity for further analysis (testing for chlorides, depth of carbonation, flaws, or permeation) to establish the cause of the corrosion and estimate remaining service life

• Monitoring RC structures for changes in corrosion activity • Checking the effect of re-alkalization or electrochemical removal of chlorides • Measuring the corrosion activity in repaired areas

Principle Reinforcement in concrete will not corrode if the protective film formed in the presence of highly alkaline pore fluid with a pH of about 13 is maintained. The passive layer may, however, be destroyed by the ingress of chloride ions or by a reduction in pH due to carbonation. When the passive film is destroyed, corrosion may occur in the presence of moisture and oxygen.

During the corrosion process, anodic and cathodic areas are formed on the reinforcement. At the

anodes, iron dissolves and iron ions diffuse into the concrete, leaving behind electrons. At the cathodic sites, the iron ions combine with water and oxygen to form an expansive corrosion product, i.e., rust. The rate of corrosion is controlled by how easily the iron ions can move through the concrete from the anodes to the cathodes and it depends on the availability of oxygen and moisture at the cathodes.

The flow of irons ions through the concrete is associated with a potential field as shown on the right. The Mini Great Dane measures the surface potentials (relative to an Ag/AgCl reference electrode) and the electrical resistance of the cover concrete between the electrode and the reinforcement. The indicated potential, Ecorr, is in terms of a Cu/CuSO4 electrode (CSE), which are -110 mV lower in value than for the Ag/AgCl electrode. The risk of corrosion is evaluated by means of the steepness of the potential gradients measured at the concrete surface and the level of the electrical resistance of the cover concrete. A large potential gradient and a low concrete resistance will normally indicate a high corrosion rate, except in saturated concrete because of the low oxygen content.

Cover Condition

Dry w/o Cl- ions Wet w/o Cl- ions Wet with Cl- ions

Ecorr, mV -50 to -200 -250 to -350 -400 to -600 Gradient

R, kOhm 20 to 50 5 to 10 0 to 1

-0.150

Reference Electrode

Wet Sponge

Control and Display Unit

H2O O2

Rust

- AnodeCathodee--

Fe2+

CO2 Cl-

Mini Great Dane

86

After areas with the lowest potential, highest gradients, and lowest electrical resistance are identified, additional tests are performed to establish the cause of corrosion, e.g., testing for chlorides and carbonation. The concrete is removed at several “hot spots,” and the actual degree of corrosion is correlated to the readings. After identification of the cause of corrosion and establishment of the chloride ion profiles and depth of carbonation, the remaining service life may be estimated (e.g., using diffusion theory) or an appropriate repair strategy may be developed.

Variation The variation of the potential readings with the Ag/AgCl measuring electrode supplied with the Mini Great Dane is normally within ± 5 mV. The electrical resistance variation is less than ± 5 %.

Testing Example The access slabs of a housing complex had been subjected to de-icing salts for 18 years. No major rust stains or spalling were observed. Shown to the right are the electrical resistance and the potentials measured with the Mini Great Dane on one of the slabs. The relatively low electrical resistance towards the railings indicates a water saturated concrete and/or the presence of chlorides in the concrete. A large potential gradient is noted from the wall towards the railing. When the concrete was removed at several locations towards the railing, the bars were found to have heavy corrosion with a 1 to 20 % reduction of the cross section. Based on further testing with the RCT and the Rainbow Indicator, service life was estimated and a repair strategy was developed.

The Mini Great Dane-2000 Ordering Numbers

Item Order # Digital meter with signal box GD-2001 Ag/AgCl measuring cell GD-2002 Connecting cable GD-2003 Cable drum, 15 meters GD-2004 Reinforcement locator GD-2005 Drill bits, 10 mm and 18 mm GD-2006 Two reinforcement adaptors GD-2007 Allen key GD-2008 Two reinforcement clamping pliers GD-2009 Hammer and chisel GD-2010 Telescoping rod for Ag/AgCl cell GD-2011 Manual GD-2012

Optional Items Calibration cell GD-2013 Temperature probe GD-2014 Electric hammer drill GD-2015 Garden spray pump GD-2016

kOhm mV (CSE)

72 55 5 -50 -110 -390

70 64 5 -40 -120 -125

68 60 5 -30 -100 -135

71 65 8 -45 -120 -120

64 62 14 -50 -90 -110

59 55 10 -45 -95 -380

81 49 19 -50 -110 -390

73 59 20 -45 -110 -380

78 54 15 -60 -125 -365

82 68 27 -55 -135 -405

89 74 19 -45 -100 -355

98 72 21 -50 -90 -325

92 87 35 -60 -85 -310

99 90 44 -50 -75 -115

102 103 65 -55 -70 -65

Line A

Line B

Line C

Line A

Line B

Line C

Wal

l

Wal

l

Railing Railing

MIRA

87

Purpose The MIRA Tomographer is a state-of-the-art instrument for creating a three-dimensional (3-D) representation (tomogram) of internal defects that may be present in a concrete element. MIRA is based on the ultrasonic pitch-catch method and uses an antenna composed of an array of dry point contact (DPC) transducers, which emit shear waves into the concrete. The transducer array is under computer control and the recorded data are transferred wirelessly to a host computer in real time. The computer takes the raw data and creates a 3-D image of the reflecting interfaces within the element. MIRA has been used successfully for the following applications. • Thickness measurement • Detection of voids in grouted tendon ducts • Detection of poor quality bond in overlays and repairs • Detection of delaminations • Detection of voids and honeycombing in concrete members

Principle MIRA is based on the ultrasonic pulse-echo method using transmitting and receiving transducers in a "pitch-catch" configuration as shown on the right. One transducer sends out a stress-wave pulse and a second transducer receives the reflected pulse. The time from the start of the pulse until the arrival of the echo is measured. If the wave speed C is known, the depth of the reflecting interface can be calculated as shown (the equation assumes that the two transducers are close to each other).

The key features that distinguish MIRA from other flaw detection devices include:

• The use of point transducers to introduce into the concrete pulses of shear waves with a nominal center frequency of 50 kHz

• The use of an array of point transducers to obtain rapidly 180 transit time measurements during each test

• The transducers are spring loaded to conform to an irregular surface and they do not require a coupling medium, that is, testing is done in the dry

• The transducer array (antenna) is connected wirelessly to the host computer, thereby eliminating the need for long cables

• The signals captured by the antenna are transferred automatically to the host computer, where the synthetic aperture focusing technique (SAFT) is used to reconstruct a 3-D model of the internal structure of the concrete

• The visualization software allows views of different slices of the reconstructed internal structure

The following provides additional description of the principles involved in the MIRA system. The antenna is composed of a 4 by 10 array of point transducers and a control unit that operates the transducers. The transducers act as transmitters and receivers in a sequential mode. The transducers are heavily damped so that a short duration pulse is created. The first figure

MIRA

88

to the right shows the typical shape of the received pulse after it has reflected from an air interface. Also shown is the amplitude spectrum of the pulse. It is seen that the nominal center frequency is about 50 kHz.

The operation of the antenna is described next. Basically, the control unit within the antenna excites one row of transducers and the other rows of transducers act as receivers. The left side figure below shows the first row of transducers acting as transmitters and the remaining rows of transducers acting as receivers. Then, as shown in the figure on the right, the next row of transducers is excited and the remaining rows to the right act as receivers. This process is repeated until each of the first nine rows of transducers has acted as transmitters.

The figure to the right shows the 45 ray paths that are involved for each of the four rows of transducers. It takes less than 3 seconds to complete data acquisition, data processing, and data transfer for a test at one antenna location. As will be discussed, the transit time for each reflected pulse is processed by the computer to create a 3-D model of the locations of the reflecting interfaces, which could be the opposite side of the member (back wall reflection), the location of reinforcing bars, and most importantly the location of internal concrete-air interfaces (such as voids, cracks, and delaminations).

If there is a defect within the member in the form of a sufficiently large concrete-air interface, a portion of the stress pulse will be reflected by the defect; and the reflected pulse will arrive at the receiver sooner than reflections from the back wall. This is illustrated in the figure to the left. As discussed below, the signal processing software uses the arrival times of the reflected pulses to determine the location of the defect within the member.

Method of operation There are four modes of operation of the MIRA system as follows:

• CALIBRATION—This mode is used at the start of testing to determine the shear wave speed of the concrete. It is recommended that testing be done at eight or more positions to obtain a good estimate of average wave speed. The determined wave speed is representative of the concrete near the surface.

• EXPLORE—This mode is intended for preliminary testing at arbitrary locations on the surface of the test object. Ideally, preliminary tests should be done at locations where the internal conditions are known. This mode is used to check the settings of the instrument before beginning actual scans.

• SCAN—This mode is used to acquire the data that will be used to evaluate the test object. Data are stored automatically after completion of measurements at the antenna location. The method for conducting a scan is discussed below.

MIRA

89

• REVIEW—This mode is for detailed study of the processed data acquired during the scan.

To carry out an inspection of the complete concrete member, the user lays out a series of scan lines 500 mm apart on the testing surface. The antenna is oriented perpendicular to the scan direction and data are recorded at predetermined steps along each scan line. The distance between successive antenna positions will depend on the nature of the defects to be detected, with closer spacings required for smaller defects. The testing layout is entered into the computer and that information is used during signal processing to establish the locations of the reflecting interfaces within the member.

After data are acquired along all the scan lines, a signal processing technique called synthetic aperture focusing (SAFT) is used to reconstruct a 3-D tomographic image of

the interior of the concrete member. In simple terms, the member is subdivided into small volume-elements (analogous to finite elements used for stress analysis). From the pulse arrival times and the known positions of the transmitter-receiver pairs, the depth of the reflecting interface can be established. Because of the inclined ray paths, the depth of the reflector is calculated using the formula for the relationship between the lengths of the sides of a right triangle (Pythagorean Theorem). In the formula shown to the right, Cs is the shear wave speed determined by MIRA during the initial calibration for the test object. If there is a large reflecting interface, reflections will be picked up by more than one receiver. This will allow reconstruction of the approximate extent of the reflecting interface.

The reconstructed 3-D image is stored in the computer, and the user can look at a 3-D picture of the locations of all detected interfaces or the user can look at the projection of the interfaces on three orthogonal planes. The views on the three orthogonal planes have formal names. A C-scan shows the reflecting interfaces projected on a plane parallel to the test surface; that is, a C-scan is a "plan view" of the reflectors. A B-scan shows the reflectors projected on a plane perpendicular to the test surface and perpendicular to the scan direction; that is, it provides and "end view" of the reflectors. A D-scan shows the reflectors projected on a plane perpendicular to the test surface but parallel to the scan direction; that is, it provides an "elevation view" of the reflectors. The user can also look at specific "slices" through the member in each of the three directions by defining the Z-coordinate for a C-scan

image, the X-coordinate for a B-scan image, and the Y-coordinate for a D-scan image.

The following is a simple test case to illustrate these different displays. The test object is a 0.43 m by 0.43 m by 0.8 m plain concrete block containing three holes as shown. The antenna was scanned along the center of the block parallel to the direction of the holes. The resulting cross-sectional views are shown. The red areas correspond to the locations of reflectors that produce high amplitude reflections. In the C-scan, we see a plan view of the holes. In the B-scan we see the end view of the block; the three holes are seen clearly and the large red zone is the bottom (back wall) of the block. In

MIRA

90

the D-scan, we see an elevation view of the holes and the bottom of the block. The views show the projections of all reflectors onto the three planes. The user can also look at the reflectors in specific slices.

Testing Examples Testing for voids in grouted cable ducts of bridge girders: MIRA was used to evaluate the conditions of prestressing ducts near the anchorage zones of a box-girder bridge. Before testing, the locations of the ducts were marked on the face of the web using information on the construction drawings (center photo below). One of the test records is shown below. The B-scan is at the cross section shown as a dashed line in the C-scan. The large amplitude signal at the location of duct indicated a high probability that the duct was not properly grouted. This was confirmed by drilling a core and carefully removing the duct to reveal the bare tendons. (Courtesy of Ramboll Finland Ltd.)

Scanning along web View of web and drilled core Condition of duct

C-scan13 mm hole 55 mm deep 30 mm hole

130 mm deep 13 mm hole 160 mm deep

D-scan

C-Scan

D-Scan

B-Scan

MIRA

91

Testing for voids in grouted cable ducts in circular columns: Circular columns, 500 mm diameter, contained 80 mm steel ducts within the central cores. The ducts contained 25 mm bars that were supposed to have been surrounded with mortar grout. Single tests (Explore Mode) were made using MIRA and the results were displayed as a B-scan image. Voided ducts were easily identified and confirmed by drilling cores into the columns.

Single test being perfomed on column and condition observed after coring

Examples of B-scans

Testing quality of bond: A steel box girder bridge was overlaid with 100 mm of fiber-reinforced concrete. The overlay included several layers of reinforcing bars that interfered with proper consolidation of the fiber-reinforced concrete below the bars. MIRA was used to evaluate the presence of voids at the interface with the steel deck. An example of the results from a scan line is shown below. Because of the shallow depth of the overlay, the B-scans and D-scans show the multiple reflections of the back wall of the overlay. The C-scan shows the locations of reflectors on a plane 90 mm from the top surface. The red regions represent possible presence of voids. Subsequent coring confirmed the MIRA results. Note that the green regions in the C-scan appear to be reflections from the reinforcing bars.

Scanning along overlay Side view of overlay showing congestion of

reinforcement

Grouted Duct Empty Duct

Duct

Opposite side of column

MIRA

92

Solid Core Core with voids below bars

MIRA Tomographer Specifications • Dry point contact shear-wave transducers with ceramic wearing tip • 50 kHz center frequency with 15 to 150 kHz operating frequency • Transducers are spring loaded to conform to rough surfaces • Phased array antenna containing 40 transducer in a 4 by 10 configuration; dimensions 435 × 235

× 146 mm; weight 4.5 kg • Wireless communication (WLAN) • Testing depth: 50 to 2500 mm • Rechargeable batteries • Time to process data at test location: not more than 3 s • 3-D tomographic display • Operating temperature -0 °C to 45 °C

MIRA Tomographer Ordering Numbers

Item Order #

Laptop computer and case (not shown) MIR-1001

Phased array antenna MIR-1002

Wireless transmitter MIR-1003

AC Adaptor MIR-1004

Cables MIR-1005

Software on CD-ROM MIR-1006

User manual MIR-1007

Wheeled carrying case MIR-1008

Approximate dimensions of case and total mass of equipment 560 mm x 350 mm x 230 mm, 13 kg 22 in. x 14 in. x 9 in, 28 lbs

Moisture Encounter

93

Purpose Moisture Encounter is used to measure near-surface moisture content in concrete or other materials • during condition surveys, e.g. for corrosion investigations, or • to check whether drying measures were adequate prior to applying a coating or an overlay on an

existing element or floor.

Principle

The Moisture Encounter is a totally nondestructive instrument that indicates moisture content by means of an impedance measurement. Parallel co-planar electrodes fitted with spring-loaded contacts are mounted on the base of the instrument, as shown to the left. During operation, a low frequency electrical signal is transmitted into the test material. The level of moisture in the material affects the impedance measured by the instrument. The detection depth is 15 to 25 mm.

Precision and accuracy For concrete with compressive strength between 20 MPa and 45 MPa, the Moisture Encounter is accurate within ±0.5 % for moisture content in the range of 2 % to 6 %. The coefficient of variation of replicate measurements on concrete with the same moisture content is about 5 %.

The presence of chlorides affects conductivity of the concrete and the may give erroneous readings. In such cases, the relative scale on the meter can be calibrated by taking readings, removing samples, and measuring their moisture content by oven-drying.

Testing Example

The Moisture Encounter is shown measuring a moisture content of 1.8 % on a concrete floor prior to application of a covering

The ME-3000 Moisture Encounter

supplied in a leather case with calibration

certificate

PetroPlaner

94

Purpose The PetroPlaner is a state-of-the-art lapping and polishing machine for preparing lapped/polished plane surfaces for: • Air Void Analysis according to ASTM C457 • Petrographic examination of polished fluorescent epoxy impregnated surfaces • Polishing of thin sections for SEM / EDS examination

When preparing polished plane sections for-air-void analysis according to ASTM C457, it is crucial that the polishing be of very high quality. Both the paste and the aggregates have to be polished to exactly the same level and no erosion of the paste has to occur. In order to measure reliably the correct chord length of each air void, it is extremely important that the individual air voids have clear and sharp edges without any degradation. Otherwise, the results of the air-void analysis will be erroneous.

Polishing of concrete specimens for air-void analysis by ASTM C457 is especially difficult if • The paste is weak due to low maturity, poor curing, or a high water-cement ratio • The paste is deteriorated • The aggregates are extremely hard, having higher resistance to abrasion than the paste • The concrete has a high air content causing erosion of the paste between individual air voids

The PetroPlaner grinding system, with its different grinding slurries, maximizes the success of such grinding and polishing jobs. The procedure can be supplemented by impregnation with an acetone based hardener that is applied prior to each grinding step.

The grinding technique, which involves three rotating parts, the specimen itself, the transverse arm connecting the two specimens and the rotating table, ensures even grinding of the specimens and even wear of the grinding surfaces.

Examples of polished plane sections with the PetroPlaner. Above left is a surface prepared for air-void analysis using the RapidAir system according to ASTM C 457 after contrast enhancement. At center and right are examples of surfaces prepared for forensic, petrographic analysis.

PetroPlaner

95

The PetroPlaner features: • Optimized pressure on the specimens during grinding with the different grinding and polishing

slurries • Eccentric operation of the polishing heads ensuring totally even and uniform grinding of the

surface • Even and minimal wear of the rotating cast iron grinding plate • Polishing of two specimens simultaneously, reducing the specimen preparation time • Built-in, self feeding and recycling mechanism of the slurry, reducing cost of the slurries • Simple and durable design with a low demand for maintenance and a long service life • Low requirements for laboratory facilities, simple and easy operation • Proven track record of 15 years with excellent results

PetroPlaner Description The photo on the left shows the complete PetroPlaner unit. Shown below are details of the attachment to the two specimens and the built-in self feeding and recycling system for the grinding slurry.

The specimens rotate eccentrically in relation to the rotating cast ion bottom plate with the grinding or polishing slurry in between. Grinding and polishing takes place using selected slurries with varying fineness of silicon carbide particles.

The typical specimens are 150 mm by 150 mm (6 in. by 6 in.) in polishing area and 40 mm (1.6 in.) in thickness.

Requirements The PetroPlaner requires access to 380 VAC and to cold water. The PetroPlaner is supplied with different silicon carbide (Carborundum™) powders for grinding and polishing. Also required are: a diamond saw, equipment for vacuum impregnation, a fume hood, and a drying oven. Germann Instruments will provide all the necessary additional equipment upon request as well as assistance in setting up the PetroPlaner and technician training. We also provide courses in concrete petrography using macroscopic examination and optical microscopy.

PetroThin

96

Purpose PetroThin is the ultimate thin section preparation machine.

Principle For the last 40 years, thin sections have been used extensively by petrographers to study the microstructure of concrete. Fluorescent epoxy impregnation of thin sections of concrete and related materials is one of the most powerful methods for determining and characterizing the following features: • The water-cement (w/c) ratio • The cement type, degree of hydration, and dispersion of cement particles • The type of pozzolan, degree of hydration, and cement-pozzolan ratio • Mixture proportions • Aggregate type, gradation, and quality • Crack measurement and characterization • Air-void structure • Surface structure and finishing defects • Alkali silica reaction (ASR) • Alkali carbonate reaction (ACR) • Delayed ettringite formation (DEF) • Freezing and thawing damage • Freezing of fresh concrete • Bleeding characteristics • Depth of carbonation • Deleterious aggregates

A thin section is an extremely powerful and versatile tool for quality control and development of new types of concrete, admixtures, fibers, or alternative raw materials. In forensic examination of deteriorating or damaged concrete, fluorescent thin section analysis is the fastest and the most reliable tool for describing and determining causes of deterioration or damage.

The PetroThin is a compact machine that can be fitted easily into

an existing laboratory Grinding roller and massive sample holder

in operation

1 2 3

1. Rough cut sample 2. Polished block 3. 20 μm thick polished section

Three Basic Steps

PetroThin

97

The standard fluorescent epoxy impregnated thin section for concrete microscopy is only 20 μm thick. The process involved in preparing the 20 μm thick slice of fluorescent epoxy impregnated concrete is extremely difficult using ordinary lapping equipment.

PetroThin is the only machine in the world that can perform the required type of grinding on an inexpensive, rapid, and routine basis. The grinding guides on PetroThin use the surface of the glass slide as a reference for grinding. Thus, it is possible to prepare 20 μm thick slices quickly and accurately.

The PetroThin has 25 years of proven track record with excellent results.

The machine is easy and safe to operate. The training needed to operate the equipment and prepare thin sections in a consistent manner can be accomplished within one week.

The standard thin sections produced on the PetroThin are 30 mm × 40 mm, but it is also possible to produce larger 30 mm × 70 mm thin sections.

The PetroThin comes with a built-in diamond saw and a grinding unit.

Procedure The basic steps in the preparation of thin sections on the PetroThin are as follows:

1 A 30 mm × 40 mm × 20 mm block of concrete is cut out of the sample (see previous page). 2 The block is bonded to a 30 mm × 40 mm piece of glass and it is trimmed on the diamond saw to

a thickness of 10 mm. 3 The block is mounted on the PetroThin and ground by the three successively finer diamond

grinding rollers. 4 The block is vacuum impregnated with fluorescent epoxy. When the epoxy has cured, excessive

epoxy is ground off plus 7 μm into the material. 5 The block is glued by a UV-hardening adhesive to the final glass slide and excess material is cut

off with the diamond saw. 6 The glass slide is mounted on the traveling head of the PetroThin, and the material is ground

down to a thickness of 20 μm using three successively finer diamond grinding rollers. The thickness is controlled by checking the birefringence colors of quartz or feldspar particles using a polarizing microscope or by direct measurement with a caliper.

7 Eventually, a cover glass is glued to the polished surface of the thin section. Alternatively, the specimen is polished if it will be used for scanning electron microscopy (SEM) or microprobe analysis.

Requirements The PetroThin is simple to install in a laboratory or other suitable area. The PetroThin requires access to 380 VAC, cold water, and a vacuum source. Additionally, it is desirable to have access to a fume hood, drying oven, equipment for vacuum impregnation of the samples, and a rugged diamond saw for rough cutting of larger samples. Germann Instruments can provide all the necessary supporting equipment.

Germann Instruments will provide assistance in setting up the equipment and training technicians. Additionally, we will provide courses in concrete petrography, optical microscopy, and SEM/Microprobe analysis.

POWER

98

Purpose The POWER test system is used for proof-load testing of anchors in concrete.

Principle An adaptor of the appropriate size is threaded to the anchor bolt. A counter pressure assembly is placed on the concrete so that it is centered with the anchor bolt. A pull bolt with coupler is threaded into the adaptor and attached to a hydraulic pull machine. The load is increased to the required proof load and held for at least 10 seconds. If the load is maintained during the hold period, the anchor passes the proof load test.

Adaptor

Counter Pressure Assembly

Pull Bolt and Coupler

POWER being used to proof load

anchor bolt

POWER Ordering Numbers Item Order #

POW-100 POWER Kit

Hydraulic pull machine with electronic gauge

L-11-1

AMIGAS printout software L-13 Cable for printout L-14 Oil refilling cup L-24 Oil refilling bottle L-25 Large screwdriver C-149 Small screwdriver C-157 Calibration table L-32 Manual L-33 Counter pressure POW-110 Pull bolt with coupling POW-120 Adaptors (specify threads), 5 pieces POW-130 Attaché case C-104-1

Profile Grinder

99

Purpose The Profile Grinder is used to obtain concrete powder by precision grinding at small depth increments for accurate determination of the chloride ion profile for the following applications: • Following ponding of specimens in the laboratory, e.g., according to NT BUILD 443 or ASTM

C1556, or • On-site on structures that have been subjected to chloride ion ingress.

From the chloride ion content profile, the chloride ion diffusion coefficient can be estimated in accordance with ASTM C1556 and used for service life calculations.

Principle A grinding bit, 18 mm in diameter, grinds the concrete to a fine powder at selected, exact depth increments, selected between 0.5 mm to 2.0 mm. The bit is attached to a grinding machine that is held against the surface by a grinding plate. The grinding takes place by working the bit over the surface in three rotations. The grinding area is 73 mm in diameter and the maximum depth is 40 mm. The powder produced at each depth increment is collected with a battery-operated vacuum cleaner (Dust Buster) containing a re-usable filter. On a vertical face, the powder is collected in a plastic bag attached to the grinding plate. For every depth increment of 0.5 mm, approximately 5 grams of powder is obtained for analysis. It takes 4 to 6 minutes to obtain each sample and about 5 minutes to determine the chloride content using the RCT (see page 112).

Depth Accuracy The depth increments are accurate to within ± 2 %

Testing Examples

0.0

0.2

0.4

0.6

0.8

1.0

0 5 10 15 20 25 30 35

Chl

orid

e C

onte

nt, %

Depth, mm Profile grinding of specimen subjected to

35 days of ponding in the laboratory. Chloride content of each sample is

determined using the RCT (page 112)

Chloride profile of a specific concrete. A chloride coefficient of 29 mm2/y is determined using

Fick’s second law of diffusion in accordance with NT BUILD 443 or ASTM C1556.

Profile Grinder

100

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0 10 20 30 40 50 60 70 80

Chl

orid

e C

onte

nt, %

Depth, mm The Profile Grinder is ready for grinding on

a 1-year old wall. The powder obtained for each depth increment is collected in a separate plastic bag. Chloride content at each depth is

determined on-site using the RCT.

Chloride content profile for the 1-year old wall. The chloride diffusion coefficient was calculated to be 75 mm2/y. It is estimated that another 5

years will elapse before initiation of corrosion of the reinforcement with a cover of 50 mm.

The Profile Grinder Kit and Ordering Numbers

Item Order # Grinder unit consisting of variable-speed grinding machine, grinder housing, handle cover with flange and counter nut, two handles, and high performance grinding diamond bit

PF-1101

Grinding plate with green felt, attachments for plastic bag and top plastic cover

PF-1102

Grinding bench plate with screws and nuts PF-1103 Attachment ring and two bolts PF-1104 Allen key, 4 mm CC-25 Two adjustable fastening pliers C-102-3 Set of anchoring tools CC-30 Two seating rubber rings PF-1105 Plastic bags, 50 pcs PF-1106 Brush PF-1107 Measuring tape RCT-1028 14 and 17 mm wrenches C-155/151 Sponge PF-1108 Dust mask PF-1109 Silicone oil bottle L-24 Spare green felt PF-1111 Manual PF-1112 Portable vacuum cleaner PF-1200

Complete Profile Grinder Kit PF-1100

Portable vacuum cleaner with reusable filter PF-1200

L

PROOVE’it

101

Purpose The PROOVE´it system is used to evaluate the resistance of concrete to the ingress of chloride ions in two ways: • By determining how easy it is to force chloride ions into saturated concrete by applying an

electrical potential across a test specimen in accordance with AASHTO T 277 or ASTM C1202. This is known as the “Coulomb Test” or the “Rapid Chloride Permeability Test (RCPT).”

• By measuring the penetration depth of chloride ions, after an electric potential has been applied to the specimen in accordance with NORDTEST BUILD 492 (Chloride Migration Coefficient from Non-Steady State Migration Experiments) to determine the “Chloride Migration Coefficient,” which can be used to estimate the chloride diffusion coefficient for service life calculations.

Principle A water-saturated concrete specimen, 100 mm diameter and 50 mm thick, is positioned in a cell (right and page 104) containing fluid reservoirs on both sides. For the RCPT or Coulomb Test, one reservoir is filled with a 3 % NaCl solution and the other with a 0.3N NaOH solution. A potential of 60 VDC is applied across the cell. The negative terminal is connected to the electrode in the reservoir with the NaCl solution and the positive terminal is connected to the electrode in the NaOH solution. The negatively charged chloride ions will migrate towards the positive terminal.

The more permeable is the concrete, the more chloride ions will migrate through the specimen, and a higher current will be measured. The current is measured for 6 hours. The area under the curve of current versus time is determined, which represents the total charge or Coulombs passed across the specimen. The Coulomb values are used for classifying the concrete as follows (ASTM C1202):

Coulombs Permeability Class Typical of >4000

4000-2000 2000-1000 1000-100

<100

High Moderate

Low Very Low Negligible

w/c* > 0.5 w/c = 0.4 to 0.5

w/c < 0.4 Latex-modified concrete

Polymer concrete *w/c = water-cement ratio

Alternatively, for the NT BUILD 492 migration test, the reservoir surrounding the negative terminal contains a 10 % NaCl solution and the reservoir surrounding the positive terminal contains a 0.3N NaOH solution. A 30 VDC potential is applied across the specimen, and the initial current is measured. Based on the initial current, the test voltage and test duration are selected accordingly. For example, if the initial current is between 120 and 180 mA, the test voltage is reduced to 15 VDC and the test duration is 24 h, but if the initial current is less than 5 mA, the test voltage is 60 VDC and test duration is 96 h. After the test is completed, the specimen is split, and the chloride ion penetration is measured by spraying the split surface with a 0.1 M silver nitrate solution. From the penetration depth and test conditions, the chloride ion migration coefficient is calculated.

The chloride diffusion coefficient can be determined directly by profile grinding (page 99) and testing for chloride ion content after ponding with a NaCl solution, in accordance with NT BUILD 443 “Concrete, Hardened: Accelerated Chloride Penetration” or ASTM C1556 "Test Method for Determining the Apparent Chloride Diffusion Coefficient of Cementitious Mixtures by Bulk Diffusion." The required ponding period is at least 35 days. A correlation can be developed between the chloride ion migration coefficient and the diffusion coefficient.

Accuracy and Variability At 60 VDC, the accuracy of the PROOVE´it microprocessor power supply is within ± 0.1 mA for a current between 30 mA and 300 mA. The repeatability of the RCPT or Coulomb Test is reported to

60 V DC Power Supply + -

NaCl Cl- NaOH

PROOVE’it

102

be about 12 % (ASTM C1202), and the repeatability of the migration test is reported to be about 9 % (NT BUILD 492).

PROOVE’it System Features Windows®-based software for testing and report preparation • Computer controlled microprocessor power supply • Testing up to 8 cells simultaneously • Voltage settings of 10, 20, 30, 40, 50, and 60 VDC • Programmable testing time as required • Temperature measurement and recording

• Cyclic testing option for effect of curing duration • Measure concrete conductivity at 60 VDC in 1

minute • Predicted 6-h Coulomb value every 5 minutes • Documentation of each test result • Easy to assemble, simple to maintain, watertight

cells

A complete system composed of coring and slicing equipment, vacuum desiccator, vacuum pump, watertight test cells, microprocessor power supply, and software are shown on the following page.

Testing Example

PROOVE´it screen-shot after completion of 8 simultaneous tests according to ASTM C1202

Pointing with the mouse arrow on any of the windows will produce a pop-out window with explanatory notes for that window. The “Status” line for the eight cells is either OFF, ON or FIN, as shown after the tests have been completed. The “Voltage-Actual” line indicates the test voltage, and the “Current-Actual” line indicates the instantaneous current during testing. The “Temperature” line indicates the instantaneous temperature in the reservoir solutions during testing, and “Elapsed Time” indicates the time since start-up of each cell. The “Pred. Coulombs” line indicates the predicted Coulombs at 6 hours, which are estimated after every 5 minutes of testing. The “Testing time” indicates the selected testing time, and the “Specimen Diameter” indicates the actual diameter of the specimen. The “Coulombs” line indicates the measured Coulombs at any time during testing.

The last line shows the “chloride ion permeability” classification according to ASTM C1202, as indicated on page 101. In arriving at the classification, the displayed Coulomb values are adjusted to a standard specimen diameter of 95 mm, as required by ASTM C1202. As an example, cell number 3 containing a specimen with a diameter of 100 mm has been measured to have 2100 Coulombs. Adjusted for a diameter of 95 mm, the Coulomb value is 1898 and, according ASTM C1202, the permeability class is LOW and not MODERATE as evaluated from the measured Coulomb value.

PROOVE’it

103

Sample Test Report The following figure shows an example test report. In this case, the report is for Cell #2 shown on the previous page. The top of the report summarizes the test result. The graph shows the measured solution temperature (——) and current (—–), and the table shows the temperature and current at 5-min intervals.

GI

The PROOVE’it System

The PROOVE´it system is shown with its main components: At the front is the PROOVE´it microprocessor power supply connected to one PROOVE´it test cell. Optional Items: At the back is the CEL-100 CORECASE for coring with an electric drill, a diamond saw for trimming the core, a vacuum desiccator, and a vacuum pump.

Note: A computer is also required with the following minimum requirements: 75 MHz Pentium, 32 MB RAM, 1.0 GB hard drive, and Windows 95, 98, NT, 2000 or XP.

PROOVE’it

104

The PROOVE’it Cells Two types of cells are available, the PR-1000 cell and the PR-1100 cell, shown below. The PR-1000 cell is the standard cell. The PR-1100 is supplied with cooling fins, which are needed if the temperature is required to be kept constant, as for example, for chloride ion migration testing using the NT BUILD 492 test method.

The cell is sealed by tightening the four corner bolts, which squeezes the gaskets against the specimen.

The following gaskets are available for different specimen diameters:

Specimen Diameter

Ordering #

104 to 102 mm PR-1010A

101 to 97 mm PR-1010B

96 to 93 mm PR-1010C

The cells are supplied with PR-1010B gaskets, unless otherwise specified. The PR-1010B gaskets match the 100-mm core diameter produced by the CEL-100 coring equipment (see page 29).

The PR-1055 Verification Unit

The PR-1055 verification unit is used to verify that the microprocessor controlled power supply is working properly. The unit is connected to line power, 110 VAC or 220 VAC. Each channel of the PROOVE’it power supply is set up for testing at a selected voltage and connected to the verification unit. When the PROOVE’it system is operating properly, the “Current-Actual” indicated on the computer screen (see page 102) should be within 30 mA ± 0.1 mA or 300 mA ±0.1 mA for the two switch settings on the verification unit.

PROOVE’it Ordering Numbers*

Item Order # Item Order # PROOVE´it cell, standard PR-1000 Power cable for power supply 230 VAC PR-1064 PROOVE´it cell, with cooling ribs PR-1100 Power cable for power supply 110 VAC PR-1065 Red connecting cord PR-1001 RS-232C serial cable for power supply PR-1066 Black connecting cord PR-1002 PROOVE´it manual PR-1090 Spare mesh for PROOVE´it cell PR-1003 Verification unit PR-1055 Temperature probe PR-1005 Vacuum desiccator for max.16 specimens PR-1070 17 mm (2) wrenches for bolts PR-1006 Vacuum pump, < 10 mm Hg (1.3 kPa) PR-1081 300 mL bottle of 3.0 % NaCl solution PR-1020 CORECASE for 100 mm cores CEL-100 300 mL bottle of 0.3N NaOH solution PR-1030 Drilling machine, 1150W CC-29 PROOVE´it software for Windows® PR-1040 Diamond saw for trimming cores PR-1060 PROOVE´it power supply for 8 cells PR-1050

*These items can be selected as needed to assemble a system to meet the purchaser's requirements.

Two types of PROOVE’it cells: standard PR-1000 cell (left) and PR-1100 cell with cooling ribs (right)

PUNDIT

105

Purpose The PUNDIT (Portable Ultrasonic Nondestructive Digital Indicating Tester) is used to measure the propagation speed of a pulse of ultrasonic longitudinal stress waves. The ultrasonic pulse velocity (UPV) that is determined can be used for the following applications: • Evaluating the uniformity of concrete within a structural member • Locating internal voids and cracks • Estimating severity of deterioration • Estimating depth of fire damaged concrete • Evaluating effectiveness of crack repairs • Identifying anomalous regions for invasive sampling with drilled cores • Estimating early-age strength (with correlation)

Principle A pulse of ultrasonic (> 20 kHz) longitudinal stress waves is introduced into one surface of a concrete member by a transducer coupled to the surface with a coupling gel or grease. The pulse travels through the concrete and is received by a similar transducer coupled on the opposite surface. The transit time of the pulse is determined by the instrument. The distance between the transducers is divided by the transit time to obtain the pulse velocity. The longitudinal pulse velocity, Cp, of an elastic solid is a function of the elastic constants (modulus of elasticity, E, and Poisson’s ratio, ν) and the density, ρ.

(1 )(1 )(1 2 )p

EC νρ ν ν

−=

+ −

The UPV test method is governed by various standards including ASTM C597, BS 1881:203, and EN 12504-4. The test

method is totally nondestructive and it is possible to repeat the test at the same point at different times to determine changes of UPV with time.

The figure to the right illustrates different conditions that may be encountered when testing an element. At the top, the path between the transducers is through solid concrete, and the travel time would be the shortest. Below that is the case where there is an internal pocket of porous concrete, such as honeycombed concrete. The pulse is scattered as it travels though the contiguous portions of the honeycombed concrete. As a result, the travel path is longer and the pulse travel time is longer. This results in a reduced pulse velocity. In the next case, the transducers are located so that the direct travel path is near the edge of a crack. The pulse cannot travel across a concrete-air interface, but it is able to travel from the transmitter to the receiver by diffraction at the crack edge. Because the travel path is longer than the distance between the transducers, the apparent pulse velocity is lower than through sound concrete. In the lowermost case, the pulse is reflected completely by the crack, and travel time is not measurable.

Precision and Accuracy The UPV test is highly repeatable. For tests of sound concrete, the coefficient of variation for repeated measurements at the same location is 2 %. The accuracy of the pulse velocity is a direct function of the accuracy of the measured distance between the transducer faces. The PUNDIT instruments have a transit time resolution of 0.1 μs.

T = Transmitter R = Receiver

T R

PUNDIT

106

Two models are available: The PUNDIT Plus and the PUNDIT 7. Both instruments are capable of investigating the structural integrity of concrete, ceramics and refractory, timber and other materials. They include the following features:

• Light, portable, rugged, simple to operate • Rechargeable battery and 110/240 VAC 50/60 Hz power supply • Large, highly visible LCD display • RS232 and oscilloscope outputs • Largest range of transducer options (24 kHz to 1 MHz) • Designed for laboratory or field operation

PUNDIT Plus

Key features: • Auto ranging transit time display; up to 9999 μs • Programmable trigger rate • Wide range of pulse repetition frequency • Measure transit time, pulse velocity, and elastic

modulus • Three transmitter voltage options; 250 V, 500 V,

or 1.2 kV • Data transferrable to Excel® spreadsheet

PUNDIT Plus Ordering Numbers Item Order #

PUNDIT Plus with data conversion software for downloading to Excel®

PP-1010

AC power cord PP-1020 Two 54-kHz transducers (transmitter and receiver) PP-1030 Two 3.7 m cables PP-1050 Couplant (250 mL bottle) PP-1060 Operating manual (CD ROM) PP-1070

Optional

Attaché case PP-1080 PUNDIT 7

Key Features: • Auto ranging transit time display: up to 6.553 ms transit time • Signal level bar graph • On screen display of test settings • Remote control by PC through RS232 port • Four transmitter voltage options: 250 V, 500 V, 750 V, or 1 kV • Wide range of pulse repetition frequency, up to 100 Hz • Built-in rechargeable batteries • Auto detecting of AC power supply • Built-in handle also functions as stand for bench or field use

PUNDIT

107

PUNDIT 7 Ordering Numbers Item Order #

PUNDIT 7 P7-2010 AC power cord P7-2020 Two 54-kHz transducers (transmitter and receiver) P7-2030 Verification bar P7-2040 Two 3 m cables and serial cable P7-2050 Couplant (250 mL bottle) P7-2060 Operating manual (CD-ROM) P7-2070

Optional

Carrying case for easy use on-site P7-2090

A range of amplifiers and attenuators are available to cover a variety of applications. Also, cables up to 30 m in length can be ordered, along with different coupling fluids to suit various applications.

Optional Transducers Transducers with resonant frequencies from 24 kHz to 1 MHz are available, including wheel probes for continuous testing in the field or in a production environment. Use lower frequencies for large, dense, and heterogeneous test objects and higher frequencies for smaller, less dense and more homogeneous test objects. General guidelines are:

Concrete: 24 to 150 kHz Graphite: 200 kHz to 1 MHz

Timber: 150 to 220 kHz Cast iron: 1 MHz

Ceramics: 24 to 220 kHz

Order # Frequency Nominal Dimensions

UTR24KHZ 24 kHz 50 mm dia × 96 mm long. UTR37KHZ 37 kHz 50 mm dia × 50 mm long. UTR54KHZ 54 kHz 50 mm dia × 38 mm long. UTR82KHZ 82 kHz 33 mm dia × 34 mm long. UTR150KHZ 150 kHz 25 mm dia × 34 mm long. UTR200KHZ 200 kHz 20 mm dia × 34 mm long. UTR220KHZ 220 kHz 6 mm dia tip, 13 mm dia body, 60 mm long (including connector) UTR500KHZ 500 kHz 6 mm dia tip, 13mm dia body, 60 mm long (including connector) UTR1MHZ 1 MHz 15 mm dia × 67 mm long (including connector).

Operating temperature range for transducers is 0 to 70 ºC. A waterproofed option is available on the 24, 37, 54 kHz transducers by special order for applications requiring use in wet conditions or immersion up to 1 m depth

RapidAir

108

Purpose RapidAir is an image analysis system for automatic determination of the air content in hardened concrete according to the linear traverse method in ASTM C457: “Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete.”

The measured parameters of the air-void structure are total air content, spacing factor, and specific surface.

Principle A core is taken from the structure, sliced, ground, and lapped in the laboratory. The resulting surface is plane, smooth, and with sharp edges along the perimeter of air voids. Before final specimen preparation, the lapping quality is checked under a stereomicroscope.

The lapped surface is colored black with a hard stamp pad containing black ink. After heating the specimen to 55 ºC, a white zinc paste is applied to the surface with a rubber spatula. The zinc paste melts on the surface and flows into the voids.

After cooling to room temperature, excess paste is removed from the surface with a straight, sharp steel blade. The quality of the black-white contrast is checked under a stereomicroscope. The voids should be totally filled with white paste and no white regions should be visible on the surface. Finally, voids in aggregates and obvious cracks are colored black under the stereomicroscope using a black marking pen. The photo on the left shows a properly prepared specimen.

The preparation of a well-lapped specimen surface for analysis takes about 30 minutes. The RapidAir measurement is done automatically in less than 17 minutes. This should be compared with a time of 4 to 6 hours normally required for manual analysis using a light microscope in accordance with ASTM C457.

Following contrast enhancement, the prepared specimen is mounted on a moving X-Y-Z stage positioned below a video camera.

The RapidAir control unit automatically moves the stage, and the software determines the portion of the total traverse length that passes through the white air voids, as shown in the magnified view to the right. After the scan is completed, the air-void parameters are determined in accordance with ASTM C457.

The specimen scan is saved automatically in a report file documenting the air content, spacing factor, and specific surface. In addition, graphical presentation of the air-void distribution and the raw data are available.

RapidAir

109

Prepared specimen positioned on the moveable stage

ready for image analysis. Overall view of RapidAir system in operation.

Correlation with ASTM C457 and Precision As reported in Pade, C., Jakobsen, U.H. and Elsen, J., “A New Automatic Analysis System for Analyzing the Air Void System in Hardened Concrete,” International Cement Microscopy Association Conference, San Diego, CA, USA, April 2002, very good agreement was found between the air-void system parameters measured by the RapidAir system and by the ASTM C 457 standard method. The study involved thirteen European laboratories. The standard deviations of the air-void parameters determined by RapidAir were as follows: • Air content: 0.37 % • Specific surface: 1.57 mm-1 • Spacing factor: 0.011 mm

Comparison between RapidAir and ASTM C457 determinations of air

content and specific surface

RapidAir Ordering Number

The RapidAir-3000 system shown to the right comes as a complete system, ready to plug in and operate, including PC with software, control unit, and manual.

A one day course is offered separately by a RapidAir specialist.

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RAT

110

Purpose The RAT (Rapid Alkali Test) measures the amounts of sodium and potassium ions that may contribute to alkali-silica reaction (ASR), which is harmful to concrete structures. The alkalies (potassium and sodium ions) in the cement paste react with reactive (amorphous) silica particles in fine or coarse aggregate and cause expansion and cracking, provided sufficient moisture is present.

To reduce the risk of ASR in new concrete structures, the quantity of sodium and potassium ions in the cement paste of fresh concrete may be lowered so as not to exceed the critical limit defined in the project specifications.

The RAT measures the amount of sodium and potassium ions in the fresh concrete or in its constituents. The test may also be used for testing powder samples of hardened concrete.

Principle A sample of the fresh concrete, or its constituents, is taken and mixed with specific amount of acid extraction liquid. A calibrated set of electrodes, one for measuring the sodium ions and one for measuring the potassium ions, is submerged into the solution and the corresponding electrode readings (in mV) are taken.

The mV-readings are transformed directly into amount of Na2O and 0.658 x K2O in kg/m3 by means of established calibration curves, and added together to give the equivalent amount of Na2O.

One test takes about 10 minutes to perform after the electrodes have been calibrated.

Similarly, for hardened concrete, a powder sample may be analyzed. Should aggregates containing reactive material need to be excluded, a core is taken, the core is fractured, and the aggregate particles are removed. The remaining material is then pulverized and analyzed.

Correlation with Other Methods and Variability

The graph shows the correlation between alkali contents determined by flame photometry and RAT, for tests performed on the same solutions prepared from different concrete mixtures. The solutions were prepared by acid extraction of the alkalies.

The correlation coefficient for these results is 0.97 and the alkali contents determined by RAT are within ±5 % of the values determined by flame photometry.

0.0

0.5

1.0

1.5

0 0.5 1 1.5

SodiumPotassium

RA

T, k

g/m

3

Flame Photometry, kg/m3

RAT

111

Testing Example

0.1

1.0

10.0

-40 -20 0 20 40 60 80 100

SodiumPotassium

Equi

v. N

a+ Con

tent

, kg/

m3

Electrode Voltage, mV Calibration of the electrodes is performed on the three calibration liquids producing typical calibration curves as indicated above. The concrete sample is dissolved in the extraction liquid, and the electrodes are submerged into the solution. In this example, the mV-reading for the Na+ electrode is 12.0 mV and for the K+ electrode it is 18.9 mV. The corresponding amounts of equivalent Na20 are 0.46 kg/m3 and 1.40 kg/m3, respectively. Adding these values gives an equivalent Na2O content of 1.86 kg/m3.

The RAT-1000 Kit and Ordering Numbers

Item Order # K+ electrode RAT-700 Spare cover for K+ electrode RAT-701 Na+ electrode RAT-800 Spare cover for Na+ electrode RAT-801 Reference electrode RAT-900 Holster for electrodes RAT-910 Electrometer w. spare battery RAT-950 Adaptor switch box RAT-960 Wetting agent for K+ electrode RAT-970 Wetting agent for Na+ electrode RAT-980 Wetting agent for ref. electrode RAT-990 Set of filling syringes, three RAT-1005 Spray bottle with distilled water RAT-1010 Calibration liquid # 1 RAT-1020 Calibration liquid # 2 RAT-1030 Calibration liquid # 3 RAT-1040 Cleaning tissues RAT-1050 Calibration sheets, 30 pcs RAT-1060 Data sheets, 30 pcs RAT-1070 Pencils (black and red) and ruler RAT-1080 Spatula, 5 pcs RAT-1090 Safety goggles RAT-1100 Rubber gloves RAT-1110 Mixing container RAT-1120 Sampling cup for fresh concrete RAT-1130 Plastic lid with holes for electrodes RAT-1140 Temperature probe RAT-1150 Manual RAT-1160

RAT-2030 Calibration

liquids

RAT-2032 Vials for

fresh concrete

RAT-2023 Vials for hardened concrete

RCT and RCTW

112

Purpose The RCT and RCTW systems are used to accurately and quickly determine the chloride ion content from powder samples of concrete obtained on-site or in the laboratory. The test results can be used for: • Establishing the chloride ion profile for service life estimation • Establishing the depth of removal of a chloride ion contaminated surface layer • Diagnosing a structure for corrosion activity, in combination with other test systems such the

Mini Great Dane, the GalvaPulse, and the Rainbow Indicator • Monitoring the chloride ion content during electrochemical removal of chlorides • Measuring the chloride ion content of fresh concrete or its constituents

Principle A powder sample of hardened concrete is obtained by drilling or grinding from the structure, or a sample is obtained from the fresh concrete. The sample is mixed into a distinct amount of extraction liquid and shaken for five minutes. The extraction liquid removes disturbing ions, such as sulfide ions, and extracts the chloride ions in the sample.

A calibrated electrode is submerged into the solution to determine the amount of chloride ion, which is expressed as percentage of concrete mass.

Two extraction methods are used:

• The RCT (Rapid Chloride Test) is used to determine the amount of acid-soluble chlorides • The RCTW (Rapid Chloride Test Water) is used to determine the amount of water-soluble

chlorides The two methods use different kinds of extraction liquids. The type of method to use will depend on the specification criteria for maximum allowable chloride ion content in either hardened or fresh concrete.

Accuracy Numerous correlations have been made between RCT test results and chloride ion content determined by standard laboratory potentiometric titration methods such as AASHTO T 260, ASTM C114, DS 423.28 or NS 3671. The following graph shows the results of such correlations made by various laboratories in the Scandinavian countries and in the U.S.

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0.25

0.00 0.05 0.10 0.15 0.20 0.25

FHWADTI, DenmarkSwedish Cement and Concrete InstituteNorwegian Concrete TechnologySwedish State Testing InstituteDanish Road Directorate%

Cl p

er C

oncr

ete

Mas

sPo

tent

iom

etric

Titr

atio

n

% Cl per Concrete Mass - RCT

RCT and RCTW

113

In one comparison, the Swedish National Testing Institute produced concrete powders containing known amount of chloride ion introduced into the concrete by diffusion. The concretes were made with different binders as illustrated in the table below. Parallel testing was done in accordance with, AASHTO T 260 and with the RCT system. The RCT readings were taken after the powder samples were kept in the extraction liquid overnight to obtain full extraction of acid-soluble chlorides. Alternatively, if the result is obtained after 5 minutes of shaking of the vial, a correction factor has to be applied to the measured chloride ion content.

The following table compares the known chloride ion content with the values determined by the RCT and by AASHTO T 260.

% Cl¯ per Mass of Concrete

Known Amount AASHTO T 260 RCT Portland Cement (CEM I)

0.023 0.071 0.328

0.024 0.070 0.314

0.022 0.072 0.321

Fly Ash Cement (CEM II/B-V)

0.020 0.057 0.244

0.019 0.052 0.229

0.019 0.061 0.238

Slag Cement (CEM III/B)

0.020 0.056 0.244

0.019 0.052 0.231

0.019 0.059 0.238

The accuracy of the RCT results compared with the known amount of chlorides is as good as with the AASHTO T 260 potentiometric titration method. The average deviation of the RCT results from the known amount of chlorides is within ± 4 %.

For repeated testing with the RCT on the same concrete powder, the coefficient of variation of test results is on average 5 %.

The precision and accuracy of the RCTW test for water-soluble chlorides is similar to RCT results.

Testing Examples Examples of chloride ion profiles measured with the RCT are illustrated on pages 99 and 100.

The graph to the right show two other profiles that were obtained from on-site profile grinding on a highway bridge column exposed to deicing salts for 4 years. Concrete powder samples were obtained at depth increments of 1 to 2 mm and were analyzed for acid-soluble chlorides with the RCT and for water-soluble chlorides with the RCTW. The depth of carbonation was measured to be 2 mm using the Rainbow Indicator, corresponding to the initial peaks of the chloride ion profiles obtained.

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RCT and RCTW

114

RCT and RCTW Ordering Numbers Item Order #

RCT-5000

RCT chloride electrode RCT-770 Electrometer for mV, pH and ºC RCT-990 Electrode wetting agent, 80 mL, w. spout RCT-1000 Distilled water, spray bottle RCT-1001 Polishing strips for electrode RCT-1002 Plastic bags for powder sampling RCT-1003 Powder collecting bowl RCT-1004 Powder collecting pan, circular RCT-1005 Powder collecting square w. clip RCT-1006 Adjustable pliers RCT-1007 Set of anchoring tools RCT-1008 Mandrel RCT-1009 Hammer RCT-1010 Powder compression pin RCT-1011 Powder weighing ampoules, 6 pcs RCT-1012 Calibration liquid, 0.005 % Cl− RCT-1013 Calibration liquid, 0.020 % Cl− RCT-1014 Calibration liquid, 0.050 % Cl− RCT-1015 Calibration liquid, 0.500 % Cl− RCT-1016 Cleaning tissues RCT-1017 Calibration sheets for hardened concrete RCT-1018 Calibration sheets for fresh concrete RCT-1019 Rubber ball dust remover RCT-1020 Pencil and ruler RCT-1021 Measuring tape RCT-1022 Extraction vials, hardened concrete, 10 pcs RCT-1023 Manual RCT-1024 RCT calibrations and applications, binder RCT-1025 Attaché case RCT-1026

The manual included in the RCT-500 kit covers testing for acid and water-soluble chlorides in hardened as well as in fresh concrete. Separately delivered is a binder (RCT-1100) with 15 years of testing experience, including advanced theory for chloride diffusion modeling.

Extra Parts

RCT-1030 set of calibration liquids RCT-1000-1 electrode wetting agent RCT-1032 mixing container and

cup

It is recommended to always have an extra set of clean RCT-1030 calibration liquids to ensure that the chloride electrode is working properly should deviations occur from the usual obtained calibration curve. The RCT-1000-1 EWA (electrode wetting agent) contains 300 mL of liquid for refilling of the RCT-1000 EWA bottle, which has a spout that fits into the electrode hole. The RCT-1032 mixing container and cup is for testing samples of fresh concrete.

RCT and RCTW

115

Consumables Extraction liquids for RCT testing for acid-soluble chlorides in hardened concrete or fresh concrete:

RCT-1023 vials, set of 25, for testing

hardened concrete RCT-1031 vials, set of 4, for testing

fresh concrete

Extraction liquids for RCTW testing for water-soluble chlorides in hardened concrete or fresh concrete:

RCTW-1023-1 vials, set of 25,

RCTW-1023-2 buffer vials, set of 25, for testing hardened concrete

RCTW-1031-1 vials, set of 4, RCTW-1031-2 buffer vials, set of 4, for

testing fresh concrete

Optional items

RCT-1027 Certified Reference Powders Nine jars, each containing 70 grams of concrete powder, with known amounts of chlorides and titrated according to AASHTO T 260

Cement type* Known amounts of Cl− Portland cement 0.023 % 0.071 % 0.328 % Fly ash cement 0.020 % 0.057 % 0.244 % Slag cement 0.020 % 0.056 % 0.244 %

*According to ENV- 197-1

RCT-1028 pH-electrode

RCT-1029 temperature probe

RCT-995 the 1.5 g balance for checking the powder weighing

ampoules supplied in the RCT-500 kit

s’MASH

116

Purpose For a long time, users of NDT systems have wished for a rapid, easy to use method for rapid screening of the integrity of structures. The s´MASH impulse-response test system fulfills this wish. The idea is to quickly screen a structure for flaws and identify suspect areas for subsequent detailed analysis, e.g. by the impact-echo test (using the DOCter), pulse-echo testing (with MIRA or EyeCon), or by invasive inspection with drilled cores (using CORECASE).

With the s´MASH, rapid evaluation can be conducted for: • Detecting voids beneath concrete slabs in highways,

spillways and floors • Detecting the curling of slabs • Evaluating anchoring systems of wall panels • Locating delaminations and honeycombing in bridge decks,

slabs, walls and large structures such as dams, chimney stacks and silos

• Detecting the presence of damage due to freezing and thawing • Detecting the presence of alkali-silica reaction (ASR) • Detecting debonding of asphalt and concrete overlays and repair patches from concrete

substrates • Evaluating the effectiveness of load transfer system in transmitting stresses across joints in

concrete structures

Principle The s´MASH uses a low-strain impact, produced by an instrumented rubber tipped hammer, to send stress waves through the tested element. The impact causes the element to vibrate in a bending mode and a velocity transducer, placed adjacent to the impact point, measures the amplitude of the response. The hammer load cell and the velocity transducer are linked to a portable field computer with s´MASH software for data acquisition, signal processing and storage.

The time histories of the hammer force and the measured response velocity are transformed into the frequency domain using the fast Fourier transform (FFT) algorithm. The resultant velocity spectrum is divided by the force spectrum, to obtain the mobility as a function of frequency. An example of such a mobility plot is given below for a solid concrete member. Mobility is expressed in units of velocity per unit force, such as (m/s)/N.

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2.5 x 10-7

0 100 200 300 400 500 600 700 800

Mob

ility

(m/s

)/N

Frequency, Hz

1K

dyn = Dynamic stiffness = 0.48 MN/mm

Average mobility

s’MASH

117

The parameters from the mobility plot that are used for integrity evaluation are: • The dynamic stiffness (the inverse of initial the slope of the mobility plot, the blue line in

previous figure; • The average mobility (dotted blue line in previous figure); • The mobility slope between 100 to 800 Hz; and • The voids ratio (the ratio of the amplitude of the initial mobility peak to the average mobility)

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ility

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/s)/N

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Void below slab

Good support

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obili

ty, (

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)/NFrequency, Hz

Honeycombed concrete

Solid concrete

Examples of mobility plots for different types of flaws are shown above. The figure on the left compares the mobility plot for a slab-on-ground with a void below the slab with the mobility plot for a slab with uniform support. The voids ratio is the ratio of the amplitude of the peak to the average mobility of the slab with good support. The figure on the right figure compares the mobility plot of a honeycombed region in a silo wall with the mobility plot of properly consolidated concrete. Honeycombed concrete is typically associated with a high mobility slope (the dashed lines).

Testing is performed on a grid marked on the surface of the structure. The s’MASH software constructs color contour plots of the various parameters, from which it is easy to identify anomalous regions of the structure that merit detailed investigation. This is done on-site after the testing has been completed, producing immediate information of the presence of anomalies.

Testing Examples Shown on the right is the result of one test as displayed on the computer with the s’MASH software. The top left window is the force-time curve obtained from the impact of the instrumented hammer. The top right window shows the velocity-time curve obtained from the geophone in contact with the concrete surface. The figure in the lower window is the mobility plot obtained from the previous two waveforms. The bottom of the display shows the various parameters calculated from the mobility plot.

s’MASH

118

Below is the contour plot of the average mobility from s’MASH tests performed on the soffit of a bridge slab that was suspected of containing delaminations. Tests were performed on a 1 × 1 m grid. Based on the contour plot, cores were drilled at three locations: (1) a region of low mobility, (2) a region of intermediate mobility, and (3) a region of high mobility. The cores confirmed that low mobility corresponded to a sound slab and higher mobility corresponded to the presence of delaminations.

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Testing Applications

Testing for voids behind tunnel lining Testing for honeycombing in slip-formed silo

s’MASH

119

Testing for delaminations in dam spillway Testing for tightness of joints of concrete tank

Testing for honeycombing and delaminations in bridge

piers Testing for cracking and debonding of limestone

cladding

Testing for anchoring quality of granite panels in high-

rise building Testing for internal cracking and debonding of

terracotta cladding

s’MASH

120

s´MASH Ordering Numbers

s´MASH-4000 Instrument Case

Item Order #

Instrumented hammer s´MASH-4000-10

Calibration certificate for hammer s´MASH-4000-20

Rubber tip for regular testing s´MASH-4000-30

Aluminum tip for pile testing s´MASH-4000-40

Transducer for 360º testing s´MASH-4000-50

Calibration certificate for horizontal transducer

s´MASH-4000-60

Belt box with 3 m cable s´MASH-4000-90

Manual s´MASH-4000-100

Attaché case s´MASH-4000-110

The instrumented hammer and the transducers need to be calibrated once a year.

s´MASH-4000 Computer Case

Item Order #

Computer with Windows®, Excel®, and s´MASH software installed

s´MASH-4000-200

s´MASH software, CD-ROM s´MASH-4000-210

Amplifier box s´MASH-4000-220

Protection shield for connecting cable s´MASH-4000-230

110-220V AC adaptor with cords s´MASH-4000-240

Attaché case s´MASH-4000-250

The amplifier box can also be used for DOCter impact-echo testing, for spectral analysis of surface waves (SASW) testing, as well as for parallel seismic testing.

A two-day training course is offered separately. The course covers the theoretical background of impulse-response testing, the testing methodology, testing cases from a variety of structures and hands-on training on testing with the s´MASH.

STEPPER

121

Purpose The STEPPER is an automated impact-echo test system for increasing the speed of testing. It is especially suited when large areas need to be tested with close spacing between test points, such as for: • Locating voids in grouted tendon ducts • Accurate assessment of regions of delamination or honeycombing

Principle Manual impact-echo testing, such as by using the DOCter system, can be time consuming when test points need to be closely spaced because the defects to be detected are small or an accurate assessment is desired of the extent of internal defects. The STEPPER permits automated impact-echo testing along a given scan line. As shown, a DOCter impact-echo receiver is attached to a cart that moves automatically from test point to test point. The spacing between test points can be as small as 20 mm. A pneumatic system is used to activate two spherical impactors: a small impactor provides high frequency input for locating small, near surface defects and a larger impactor provides for deeper penetration to identify the back face of the test object.

The STEPPER unit contains an electrical drive system for automated scanning and a pneumatic system for automated testing

A close up view of the DOCter transducer and one of the two spherical impactors

As the STEPPER moves along a scan line, data are automatically recorded for subsequent post processing by software developed at the Federal Institute for Materials Research and Testing (BAM). The software analyzes the data and provides a 2-D image that shows the depth of reflecting interface as a function of distance along the scan line (known as a B-scan). An example of such an image is shown on page 123.

To further increase the rate of testing, the STEPPER can be augmented with an array attachment for five DOCter transducers as shown to the left. With the array attachment, testing can be done simultaneously along five scan lines.

STEPPER

122

Scanning Frames The STEPPER is suited for automated impact-echo testing on horizontal surfaces. When testing needs to be done on a vertical surface or on a soffit (overhead surface), special frames are available to support the impact-echo test unit and carry out an automated scan of the test area. A scanning frame is composed of a longitudinal track that is fixed to the test surface and a transverse track that travels along the longitudinal track. An impact-echo unit is attached to the transverse track and travels in discrete steps from test point to test point. When a transverse scan is completed, the longitudinal drive moves the transverse track to the next scan line and the scan is repeated. Thus tests are completed automatically on a grid of test points. The grid points can be as close as 10 mm.

Fixed track

Transverse drive

Transducer/Impactor

Longitudinal drive

Plan View Scanning frames can be attached to surfaces by anchor bolts or they can be held in place with a vacuum attachment system. The vacuum attachment system is typically faster to install, but as a safety precaution the scanner needs to be secured with cables or chains.

The vertical wall scanner that is anchored to the surface has a 1.7 m limit for the transverse scan, but the longitudinal scan is not limited to any specific distance. For the vacuum system, the scan limits are 1.4 m in one direction and 1.6 m in the perpendicular direction.

The 2-D scanning system requires two computers. One computer is used to control the movement of the longitudinal and transverse drives. The other computer is for data acquisition and data processing.

For a grid spacing of 50 mm, the rate of testing is about 1 m2/h and it takes about 1 h to process the data for each m2 of testing.

Testing Examples

Vertical wall scanner system attached to web of post-

tensioned bridge Vacuum scanner attached to soffit of post-tensioned

bridge

STEPPER

123

Impact-Echograms The large number of data obtained during a 2-D impact-echo scan can be used to generate images of the internal structure of the test object, known as impact-echograms. The technique is illustrated in the schematic below on the left. For each scan line, each amplitude spectrum is replaced by a dash at each peak in the spectrum. The amplitude of the peak is indicated by grayscale. When these dashes are placed next to each other, the result is a cross-sectional image of the reflecting interface (or a B-scan). A lower frequency corresponds to a deeper reflector as indicated by the basic impact-echo equation shown on page 41. Alternatively, a plan view can be obtained for a selected frequency (or depth). This is called a C-scan and shows the extent of reflectors that are present at the selected depth. This analogous to a “slice” in a medical tomogram.

Example of a cross-sectional image (B-scan) created by

processing impact-echo data along a scan line. The test object was a concrete slab with an irregular cross section as shown above. The resulting impact-echogram shows correctly the varying thickness of the slab. The low frequency peak at

about 2 kHz is an artifact of the transducer.

STEPPER Ordering Numbers Scanning Frames Ordering Numbers Item Order # Item Order #

STEPPER drive unit, including pneumatic system

STEP-1000 Vertical wall scanner frame including X and Y drive motors , motor controllers, and pneumatic system

STEP-1070

Adapter for single transducer STEP-1010 Adapter for transducer STEP-1080 Mark IV DOCter transducer DOC-50 Computer and software for

controlling frame (specify Linux or Windows)

STEP-1090

12 V Battery STEP-1020 Computer and software for data acquisition and data processing

STEP-1100

BAM software STEP-1030 Optional Items Optional Items Array attachment for 5 Mark IV transducers

STEP-1040 Vacuum scanner frame: X and Y drive motors, controllers, and vacuum plates

STEP-1110

Four additional Mark IV transducers STEP-1050 Vacuum pump STEP-1120 Software for transducer array STEP-1060

0.3 m

1.5 m 1.5 m1.0 m

0.2 m

Surfer

124

Purpose Surfer is a compact hand-held instrument for measuring the propagation speed of a pulse of ultrasonic longitudinal stress waves. The instrument incorporates two dry-point-contact (DPC) transducers that are brought into contact with the surface of the test object. Thus ultrasonic pulse velocity can be measured without having access to opposite sides of the test object. Surfer can be used for the following applications: • Assessment of concrete uniformity • Estimation of the extent and severity of deterioration of near-

surface concrete • Evaluate flexural strength of stone panels using correlations • Evaluation of damage to test specimens during durability

testing (freezing and thawing, sulfate attack, alkali-silica reaction)

• Estimation of depth of surface-opening cracks • Estimation of early-age strength development (with correlation)

Principle Surfer is based on measuring the time it takes for a pulse of longitudinal stress waves (P-waves) to travel from one transducer to another on the same surface. The nominal distance between the transducers is 150 mm. Because point transducers are used, the wave pulse travels away from the

transmitting transducer along a spherical wavefront. When the wavefront arrives at the receiving transducer, a signal is generated. The instrument measures the pulse transit time from transmitter to receiver, and computes the pulse velocity using the known distance between transducers. The transducers are designed to work without a coupling material (grease or gel). In contrast with traditional pulse velocity instruments, which are based on through transmission, Surfer measures the wave speed in the near-surface concrete. Thus it is not necessary to have access to opposite sides of the test object. Because there is no cabling, no coupling fluid, and no need to measure the distance between transducers, measurements can be made rapidly within 2 to 3 seconds.

Method of operation There are two modes of operation:

• Measurement of transit time and pulse velocity • Measurement of depths of surface-opening cracks

Before making transit time measurements, the menu system and keypad are used to set up the instrument, which includes entering the exact distance between the transducers. The instrument includes an liquid crystal display (LCD) that can be set up to display transit time or pulse velocity. After the set-up parameters have been entered, the transducers are pressed against the concrete surface with a force between 50 to 100 N (10 to 20 lb). The device will self-activate and begin taking measurements. The transducers need to be perpendicular to the surface and a steady pressure needs to be maintained to obtain accurate and consistent measurements.

When making measurements in reinforced concrete, a reinforcement locator (see page 33) should be used to establish the locations of the reinforcement. Orient the Surfer so that the longitudinal axis is not aligned parallel to the direction of the reinforcement. The sketch to the right shows acceptable and

Surfer

125

unacceptable positioning of the Surfer. If the device is aligned close to and parallel to the reinforcement, the stress pulse will refract into the reinforcement and a short transit time will be measured.

Surfer can also be used to measure the depths of surface-opening cracks. When the stress pulse reaches the tip of a surface-opening crack, the stress pulse is diffracted by the crack tip. The diffracted pulse travels away from the crack tip and is detected by the receiver. Because the crack increases the length of the travel path from transmitter to receiver, the transmit time will be greater than when no crack is present. Crack depth is determined by making two transit time measurements. The first one is made with the transducers aligned parallel to the crack, and the second one is made with the transducers perpendicular to the crack. For the second measurement, the crack should be at the midpoint between the transducers. Surfer uses these transit times and the distance between the transducers to calculate the crack depth:

2

12

c

p

tLdt

⎛ ⎞= −⎜ ⎟⎜ ⎟

⎝ ⎠

Where L is the distance between the transducers, tp is the transit time parallel to the crack, and tc is the transit time with transducers perpendicular to the crack. The LCD will indicate the two transit times and the calculated crack depth. The crack depth measurement range is 10 to 50 mm. The following summarizes the process:

Measure transit time (tp) parallel to crack

Measure transit time (tc) across crack

Display of transit times and crack depth

To use Surfer to estimate early-age strength development of concrete, a relationship needs to be established between concrete strength and pulse velocity. Such a relationship can be established by making pulse velocity measurements on standard strength test specimens and then testing the specimens for strength. The resulting data can be used to develop a regression equation to represent the relationship between concrete strength and pulse velocity. Refer to ACI 228.1R (In-Place Methods to Estimate Concrete Strength) for guidance on developing and using the strength relationship.

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126

Because the modulus of elasticity is proportional to the square of the pulse velocity (see page 105), Surfer can be used as an alternative to resonant frequency testing to monitor deterioration of specimens used in standard durability tests, such as freezing and thawing. In such tests, the decrease in the dynamic modulus of elasticity is used as an indicator of deterioration. The elastic modulus ratio is equal to the square of the pulse velocity ratio:

2

n n

i i

E VE V

⎛ ⎞= ⎜ ⎟

⎝ ⎠

Where Vi and Ei are the initial values of pulse velocity and modulus of elasticity; and Vn and En are the values of pulse velocity and modulus of elasticity after exposure to the test conditions.

Surfer Specifications • Dry point contact, longitudinal-wave transducers with ceramic wearing tips • 50 kHz center frequency • Battery operated (3 AA batteries required) • LCD with backlighting • Transit time range: 15 to 100 µs • Transit time measurement accuracy: ±1 % • Crack depth measurement range: 10 to 50 mm • Pulse repetition frequency: 5 to 20 Hz • Operating temperature range: -20 to 45 °C • Storage capacity: 4000 results • Metric and inch-pound units • Data transfer to computer

Surfer Ordering Numbers

Item Order #

Hand-held unit with soft carrying case SUR-1001

Plastic plate for operational check SUR-1002

Cable for connection to PC SUR-1003

Software on CD-ROM SUR-1004

User manual SUR-1005

TORQ-TEST

127

Purpose The TORQ-TEST is used to evaluate the shear strength of • Surface concrete • The bond between carbon fiber reinforced polymer (CFRP) sheets or strips and concrete • The bond between an overlay and concrete

Principle A disc with an integral ring, 55-mm inner diameter and 75-mm outer diameter, is bonded to the surface using a rapid curing adhesive (GRA) and is used to impart shearing stress to the test surface.

For tests of bare concrete, the surface should be prepared first with a diamond grinding tool to produce a flat surface and to expose the coarse aggregate. Before bonding the ring, a special double-barrel coring bit is used to produce partial cores as illustrated below. The coring bit diameters match the inner and outer diameters of the ring.

55 mm

75 mm

0

2

4

6

8

10

12

0 5 10 15 20 25 30 35 40

She

ar S

treng

th, M

Pa

Peak Force, kN

After the adhesive has cured, a torque is applied to the ring until rupture occurs due to shearing stress. The torque is applied with a special torque housing that is anchored to the surface. The loading is accomplished with one of the pull machines used for the CAPO-TEST, as shown on page 23. The load from the pull machine is applied eccentrically to the torque housing, thus producing a torsional moment.

The peak force is recorded and is converted to a shear strength using the provided conversion relationship, as shown above (right).

Additional information can be found in the following reference: Petersen, C.G. and Poulsen, E., “In-Situ Testing of Near-to-Surface Layer of Concrete and Epoxy-Bonded CFRP Strips,” US-Canada-Europe Workshop on Bridge Engineering, Zürich, Switzerland, 1997.

Variation The coefficient of variation of replicate test results is about 10 % on concrete with a maximum aggregate size of 38 mm.

TORQ-TEST

128

Testing Example

Testing with the TORQ-TEST on a bridge girder before application of CFRP strips

The TORQ-TEST Equipment and Ordering Numbers

TORQ-800 kit Item Order #

Torque housing with eccentric loading TORQ-810 Torque discs, 6 pcs TORQ-820 Steel brush TORQ-830 GRA glue, box B-11060 Set of anchoring tools, 8 mm TORQ-850 Anchors, 8 mm, 20 pcs TORQ-860 Emery cloth TORQ-870 Rubber ball dust remover TORQ-880 Hammer TORQ-890 Manual TORQ-900 Attaché case TORQ-910 C-104 CAPO-TEST Pull Machine Kit As shown on page 23, consisting of:

Item Order #

Hydraulic pull machine with electronic gauge, 0-100 kN, 0.1 kN digital division

L-11-1

AMIGAS printout software L-13 Cable for printout L-14 Oil refilling cup L-24 Oil refilling bottle L-25 Large screwdriver C-149 Small screwdriver C-157 Calibration table TORQ-920 Manual TORQ-930 Attaché case TORQ-940

The twin drill bit for partial coring (Order # TORQ-950) is used with the CS-75 CORECASE, page 29.

Torque housing

Pull machine

Rupture surface

NDT-Titans www.NDT-Titans.com

129

The NDT-Titans is an international group of testing experts providing professional services in nondestructive testing (NDT) of concrete and related subjects.

The NDT-Titans have on average more than 25 years of experience with NDT systems and their applications. The NDT-Titans are academics, consultants, and researchers, all with a practical background in testing. They have invented, researched and developed many of the systems covered in this catalog. They are involved on a day-to-day basis with NDT in major consulting and testing companies or educational and research institutions. The NDT-Titans are members of relevant ACI, ASTM, and European standards-development committees.

The NDT-Titans offer the following services to clients on a worldwide basis:

1. General NDT seminars The seminars are tailored to the client’s specific needs, e.g., in relation to: • Durability • Safely loading of structures at early ages • Quality control of finished structure • Upgrading of structures • Locating flaws in dubious structures • Estimating remaining service life • Quality assurance of repairs • Monitoring of structures

The seminars deal with NDT systems in general, outlining the properties measured with the various systems, the background of the test systems, their benefit(s), their limitations, and the costs. Typical testing cases are illustrated for each of the categories mentioned above.

2. NDT training courses There are courses for each of the following subjects and NDT systems: • Chloride penetration into concrete; the Profile Grinder and RCT/RCTW • Evaluation of resistance to chloride penetration with PROOVE’it and Merlin • Air-void analyses of fresh concrete with the AVA • Rheology of fresh concrete using the ICAR Rheometer • Simulation of temperatures and stresses during hardening of a structure with Be4Cast software • Testing for accelerated construction schedules with the LOK-TEST and COMA-Meter for in-

place compressive strength • Testing of the near-to-surface properties for resistance to chloride penetration, strength, and

water permeation with the PROOVE’it, the CAPO-TEST and the GWT • Upgrading of structures, testing for strength with CAPO-TEST and depth/size of reinforcement

with the CoverMaster • Quick screening of flaws in structures and testing for depth of piles with the s’MASH impulse-

response system • Thickness measurement and location of flaws with the DOCter impact-echo test system, and

with the EyeCon and MIRA pulse-echo systems • Pavement thickness measurement and dowel bar locations with Eddy-Thick and Eddy-Dowel • Testing for corrosion activity and service life calculations using GalvaPulse and RCT/RCTW • Testing of repairs with DOCter, BOND-TEST, and GalvaPulse • Testing with TORQ-TEST and DSS-TEST when using CFRP-strips for structural

strengthening

www.NDT-Titans.com NDT-Titans

130

3. Implementation Support Support is provided during initial planning and implementation of the NDT systems on a particular project. Such support is typically related to: • Contract specifications and procedures • Discussion of the testing problem for a specific type of structure • Selecting the proper test system(s) and choosing the correct settings and/or hardware • Developing correlations and analysis of the test results • Planning of the testing, interpretation of the test results and methods of verification • On-site assistance during implementation of test system(s) • Transfer of data and installation of additional software • Experience with similar structures

4. Testing with NDT methods The NDT-Titans can participate in the testing on a specific job, either by offering training for the client in the correct application of the NDT system and the interpretation of the test results, or by providing testing services.

Examples of Activities by the NDT-Titans Team

General NDT seminar, Mumbai, India

On-site DOCter training prior to testing

General NDT seminar, Poland

s’MASH seminar, USA

DOCter training course, Beijing, China

General NDT seminar, Iran

AVA training for Pennsylvania DOT

personnel USA

On-site LOK-TEST training for early

removal of formwork, UK

Training seminar on use of DOCter

impact-echo system, Denmark

Rev. 4-5-10

GERMANN INSTRUMENTS A/S Emdrupvej 102, DK-2400 Copenhagen, Denmark Phone: +45 39 67 71 17, Fax +45 39 67 31 67 E-mail: germann-eu@germann.org Web site: www.germann.org

GERMANN INSTRUMENTS, Inc. 8845 Forest View Road, Evanston, Illinois 60203, USA Phone: (847) 329-9999, Fax: (847) 329-8888 E-mail: germann@germann.org Web Site: www.germann.org

Test smart - Build right GIGI

Claus Germann Petersen President

Mariana Lara Vice- President