High-strength concrete has been available for many … · Figure 3.18 500-Kip (2,200-kN)...

ABSTRACT

LOGAN, ANDREW THOMAS. Short-Term Material Properties of High-Strength Concrete (Under the direction of Amir Mirmiran)

The need to extend the applicability of the AASHTO LRFD Bridge Design

Specifications to high-strength concrete is being addressed by a series of projects being

sponsored by the National Cooperative Highway Research Program (NCHRP). Among

these projects, NCHRP Project 12-64 is being carried out at North Carolina State

University (NCSU) to expand the use of the design specifications to 18,000 psi (124

MPa) for reinforced and prestressed concrete members in flexure and compression. As a

part of this project, specimens were tested to determine the material properties of three

high-strength concrete mixtures having target compressive strengths of 10,000, 14,000,

and 18,000 psi (69, 97, and 124 MPa). The effects of various curing methods were also

studied. This study covers the compressive strength, elastic modulus, Poisson’s ratio, and

modulus of rupture of high-strength concrete. The study showed that extended curing

beyond 7 days resulted in little or no increase in compressive strength. For predicting the

elastic modulus of high-strength concrete, the ACI 318-02 or AASHTO-LRFD equation

over-estimates the actual modulus while the ACI 363R-92 equation adequately predicts

the measured value. The modulus of rupture equation in ACI 318-02 or AASHTO-LRFD

gives a good approximation of the modulus of rupture of high-strength concrete when 1-

day heat curing and 7-day moist curing are used. The equation from ACI 363R-92 gives

a good estimate of modulus of rupture values for continually moist-cured specimens. The

Poisson’s ratio of high-strength concrete is generally within the range of that reported for

normal-strength concrete.

North Carolina State University Department of Civil, Construction,

and Environmental Engineering

M.S. Thesis

SHORT-TERM MATERIAL PROPERTIES OF HIGH-STRENGTH CONCRETE

By

Andrew T. Logan B.S. University of Florida, Gainesville, Florida, 2000

Thesis Committee: Amir Mirmiran, Chair

Sami Rizkalla Michael L. Leming

June 6, 2005

Biography

Andrew Thomas Logan was born in Leesburg, Florida. He received a B.S. in

Civil Engineering from the University of Florida and then worked for several years as a

roadway, drainage, and land development engineer for a civil engineering firm in Naples,

Florida. In 2003, he relocated to Raleigh, North Carolina, to pursue a M.S. degree in

civil engineering structures.

ii

Acknowledgments

The completion of this thesis would not have been possible without the support I

received from my wife, Shelly Logan. I am also grateful for the support and

encouragement from my parents who have always pushed me to challenge myself. At

North Carolina State University I was fortunate to have the privilege to work on this

project under the direction of my chairperson, Dr. Amir Mirmiran. I would like to thank

Dr. Mirmiran as well as Dr. Sami Rizkalla, Dr. Michael Lemming and Dr. Paul Zia for

their guidance and wisdom. I thank my fellow graduate students that were part of this

project team who gave me the physical and intellectual support to complete this study. I

would like to acknowledge Boral Material Technologies, Degussa Admixtures, Roanoke

Cement, Carolina SunRock , and Elkem for their generous material donations and

support. Finally, I would like to thank Ready Mixed Concrete Co. in Raleigh, North

Carolina for the efforts they made to assist in the development of the concrete mixtures

used in this project as well as producing and delivering all of the concrete used to cast the

test specimens.

iii

Table of Contents

List of Tables v

List of Figures vi

1. INTRODUCTION 1

1.1 Background 1

1.2 Previous Research 3

1.3 Relationship to NCHRP Project 12-64 6

1.4 Structure of the Thesis 7

2. PRELIMINARY WORK 9

2.1 Trial Batches 9

2.2 End Treatment of Cylinders for Compression Tests 16

3. EXPERIMENTAL PROGRAM 19

3.1 Batching 19

3.2 Casting 22

3.3 Curing 25

3.4 Test Procedure 33

4. TEST RESULTS AND DISCUSSIONS 45

4.1 Compressive Strength 45

4.2 Elastic Modulus 55

4.3 Poisson’s Ratio 58

4.4 Modulus of Rupture 60

5. CONCLUSIONS 65

References 69

Appendix A – Properties of Aggregate 74

Appendix B – Test Data 80

Modulus of Elasticity/Compression Test 81

Modulus of Rupture Test 102

iv

List of Tables

Table 2.1 Mixture Proportions Previously Developed at NCSU 12

Table 2.2 Trial Batches for Target Strength of 18,000 psi (124 MPa) 13

Table 2.3 Selected Concrete Mixture Proportions 16

Table 3.1 Moisture Contents of the Aggregates Used 20

Table 3.2 Description of Test Specimens for Each Target Strength 23

v

List of Figures

Figure 2.1 Preparing Materials for Trial Batches 11

Figure 2.2 Filling Cylinder Molds 12

Figure 3.1 Testing for Moisture Content of Aggregates 20

Figure 3.2 Loading of Truck at Batch Plant 21

Figure 3.3 Control Room at Batch Plant 21

Figure 3.4 Rodding of 4 x 8-in. (100 x 200-mm) Cylinders 24

Figure 3.5 Finishing the Surfaces of 6 x 6 x 20-in. (150 x 150 x 510-mm) Beams 25

Figure 3.6 Molds Covered with Wet Burlap and Sealed with a Plastic Sheet 28

Figure 3.7 Initial Temperature Time History for the 10,000 psi (69 MPa) Target Strength Under Moist Curing

28

Figure 3.8 Initial Temperature Time History for the 14,000 psi (97 MPa) Target Strength Under Moist Curing

29

Figure 3.9 Initial Temperature Time History for the 18,000 psi Target Strength Under Moist Curing

29

Figure 3.10 Curing Tank 30

Figure 3.11 Beams Covered with Wet Burlap and Plastic Sheet in the Environmental Chamber

31

Figure 3.12 Initial Temperature Time History for the 10,000 psi (69 MPa) Target Strength Under Heat Curing

32


32


33

Figure 3.15 Grinding Machine 34

Figure 3.16 Cutting Wheel Passing Over the Cylinder 35

vi

Figure 3.17 Cylinder Surface After Grinding 35

Figure 3.18 500-Kip (2,200-kN) Compression Machine 36

Figure 3.19 Apparatus Prior to Inserting Cylinder – Top View 38

Figure 3.20 Apparatus Prior to Inserting Cylinder – Side View 38

Figure 3.21 Attaching Apparatus to Cylinder with Screws 39

Figure 3.22 Removal of Temporary Aluminum Support Bar 49

Figure 3.23 Fully-Instrumented Cylinder After Removal of Temporary Support Bars

40

Figure 3.24 Specimen in Compression Machine 40

Figure 3.25 2,000-kip (8,900-kN) Compression Machine 42

Figure 3.26 6 x 12-in. (150 x 300-mm) Cylinder in Compression Machine 43

Figure 3.27 Modulus of Rupture Test Setup 44

Figure 4.1 Compressive Strength of 4 x 8-in. (100 x 200-mm) Cylinders at 28 Days

46

Figure 4.2 Compressive Strength of 4 x 8-in. (100 x 200-mm) Cylinders vs. Time for 10,000 psi (69 MPa) Target Strength

47


47


48

Figure 4.5 Strength Gain Over Time Expressed as % of the 28-Day Strength 50

Figure 4.6 Typical Failure Modes of Concrete Cylinders 52

Figure 4.7 Fractured Coarse Aggregate 53

Figure 4.8 Specimen Size Effect on Compressive Strength 54

Figure 4.9 Elastic Modulus vs. Time for 10,000 psi (69 MPa) Target Strength 56

vii

Figure 4.10 Elastic Modulus vs. Time for 14,000 psi (97 MPa) Target Strength 56

Figure 4.11 Modulus vs. Time for 18,000 psi (124 MPa) Target Strength 57

Figure 4.12 Elastic Modulus vs. Compressive Strength 58

Figure 4.13 Poisson’s Ratio vs. Time for Various Concrete Strengths 59

Figure 4.14 Poisson’s Ratio vs. Time for Various Curing Methods 59

Figure 4.15 Modulus of Rupture vs. Time for 10,000 psi (69 MPa) Target Strength 61

Figure 4.16 Modulus of Rupture vs. Time for 14,000 psi (97 MPa) Target Strength 62

Figure 4.17 Modulus of Rupture vs. Time for 18,000 psi (124 MPa) Target Strength

62

Figure 4.18 Surface Cracking of 7-Day Moist-Cured Specimens After Removal from Curing Tank

63

Figure 4.19 Modulus of Rupture vs. Compressive Strength 64

viii

1. INTRODUCTION

1.1 Background

The American Concrete Institute’s (ACI) Committee 363 defines high-strength concrete

as concrete with a specified compressive strength greater than or equal to 6,000 psi (40 MPa)*.

The Committee excludes the consideration of special concretes “made with exotic materials or

techniques” [ACI 363R-98 1998]. The materials used to make high-strength concrete are for the

most part the same as the materials used to make conventional-strength concrete. High-strength

concrete consists of portland cement, high-quality coarse and fine aggregates, water, and a water-

reducing admixture. In addition to the cement, supplementary cementitious materials including

fly ash, silica fume, metakaolin, and ground granulated blast furnace slag are typically used. The

characteristic of high-strength concrete mixtures that differentiates them from conventional

concrete mixtures is the low water to cementious materials ratio. Water to cementitious material

ratios for high-strength concrete are usually below 0.35 [Neville 1996].

That using low water to cement ratios would create high-strength concrete (HSC) has

been known for many years. Early research with high-strength concrete was done in 1930 by

Yoshida in Japan [Mirmiran, et al. 2003]. From that time, experimental research continued but

HSC was not used in practical applications because special methods of compaction and curing

were required. The highest-strength commercially available concrete in the 1950’s was

approximately 5,000 psi (34 MPa). In the following decade commercial concretes were reaching

strengths of 6,000 to 7,500 psi (41 to 52 MPa) [ACI 363R-92 1997].

Development of high-range water reducing admixtures (superplasticizers) in the 1960’s

proved to be the catalyst that would make it possible for high-strength concrete to be used in the

construction industry. By using superplasticizers in conjunction with set retarders, concrete * ACI Committee 363 has proposed to increase this value to 8,000 psi.

1

with low water to cementitious material ratios could be produced using standard practices while

maintaining acceptable criteria for workability and set time [Mirmiran, et al. 2003].

The development of high-strength concrete has led to more efficient designs of buildings

and bridges. The higher strength allows designers to utilize shallower cross sections and longer

spans. Currently, the growing demand to utilize high-strength concrete requires modifications of

design codes to expand their applicability to concretes with high-compressive strengths. The

American Association of Highway and Transportation Officials is addressing the need to expand

the applicability of its LRFD Bridge Design Specifications to high-strength concrete with a

series of projects under the sponsorship of the National Cooperative Highway Research Program

(NCHRP). Among these projects, NCHRP Project 12-64 is being carried out at North Carolina

State University (NCSU) to expand the limit of the design specifications to 18,000 psi (124 MPa)

for reinforced and prestressed concrete members in flexure and compression. As a part of this

project, specimens are being tested to determine the material properties of three high-strength

concrete mixtures having target compressive strengths ranging from 10,000 to 18,000 psi (69 to

124 MPa) [Mirmiran, et al. 2003].

The material properties investigated in this research project were compressive strength,

elastic modulus, Poisson’s ratio, and modulus of rupture. The elastic modulus is the slope of the

linear portion of the axial stress-strain curve, and is used in structural design to “calculate

deflections, axial shortening and elongation, buckling and relative distribution of applied forces

in composite and non-homogeneous structural members”. Poisson’s ratio is the ratio of the

transverse strain to axial strain that is induced by an uniformly-distributed axial load. The

modulus of rupture is the flexural tensile strength of a material, which is generally used to

estimate the load at which a concrete member will develop flexural cracks [PCI 1999].

2

1.2 Previous Research

A project similar to this one was conducted in the late 1970’s at Cornell University to

investigate the material properties of high-strength concrete. The research was performed by

Carrasquillo, et al. (1981) and included tests of three concrete mixtures with 53-day compressive

strengths ranging from 4,600 psi to 11,100 psi (31.7 MPa to 76.5 MPa). Some of the specimens

were moist cured for 7 days and then allowed to dry until tested at an age of 28 days. Others

were moist cured for 28 days and then allowed to dry until tested at an age of 95 days. The

control group was moist-cured until the day of testing. It is important to note that the specimens

that were continually moist cured were removed from the moist room and allowed to dry for

approximately 2 hours prior to testing. The data showed that when compared to the normal-

strength concrete, drying of the specimens resulted in a lower compressive strength and modulus

of rupture for high-strength concrete. The reduction in the modulus of rupture was more

significant than the reduction in the compressive strength. Carrasquillo, et al. also compared

compressive strengths measured from 6 x 12-in. (150 x 300-mm) and 4 x 8-in. (100 x 200-mm)

cylinders. They concluded that the ratio of the strengths from the larger cylinders to smaller

ones was 0.90 and was neither a function of compressive strength nor the testing age. From their

data for the elastic modulus and modulus of rupture, they proposed the following equations

relating these properties to the compressive strength of the concrete for compressive strengths

ranging from 3,000 psi (21 MPa) to 12,000 psi (83 MPa):

E = 40,000(f’c)0.5 + 106 psi (1a)

[E = 3,320(f’c)0.5 + 6,900 MPa] (1b)

fr = 11.7√f’c psi (2a)

[fr = 0.94√f’c MPa] (2b)

3

where E is the modulus of elasticity, fr is the modulus of rupture, and f’c is the specified

compressive strength [Carrasquillo, et al. 1981]. In 1992, these equations were reported in ACI

Committee 363’s State-of-the-Art Report of High-Strength Concrete [ACI 363R-92 1997].

In 1993, a Strategic Highway Research Program report on the mechanical behavior of

high performance concrete was published. The research for this project was conducted by Zia, et

al., at North Carolina State University. The concrete specimens referred to as “Very High

Strength” had 28-day compressive strengths ranging from 8,080 psi (55.7 MPa) to 13,420 psi

(92.5 MPa) depending on raw materials used. The authors found that the ratio of strengths from

6 x 12-in. (150 x 300-mm) to 4 x 8-in. (100 x 200-mm) cylinders ranged from 0.91 to 0.98,

depending on the type of coarse aggregate used. Considering all test ages, the data was in

agreement with the ACI 318 equation for elastic modulus, which is similar to the AASHTO-

LRFD. They found that the equation in ACI 363 developed by Carrasquillo, et al. (1981) under-

estimated the measured elastic modulus. With regards to the modulus of rupture, the researchers

found that at the design age, the ratio of the observed value to the value predicted by ACI 318

was 1.06 for concrete made with fly ash and 1.15 for concrete made with silica fume.

Comparing the measured values to those predicted by ACI 363, the ratio was as low as 0.68 [Zia,

et al. 1993].

More recent research on the subject was reported by Mokhtarzadeh and French (2000).

The study included 142 mixtures with reported 28-day strengths ranging from 8,000 psi (55 MPa)

to 18,600 psi (128 MPa). Their data showed the ACI 318 equation to over-predict the elastic

modulus of high-strength concrete, while the ACI 363 equation provided a more reasonable

prediction of the elastic modulus for their specimens. For the modulus of rupture, they found

that values measured for the moist-cured specimens were adequately predicted by the ACI 363

4

equation. Values from the heat-cured specimens fell in between the values predicted by the ACI

363 and ACI 318 equations. The authors proposed a new relationship with a coefficient of 9.3 to

be used in lieu of the 7.5 in the ACI 318 equation [Mokhtarzadeh and French 2000].

Légeron and Paultre (2000) published a technical paper compiling modulus of rupture

data by themselves and various other researchers. The authors reported that several studies had

found that curing conditions significantly affected the measured value of the modulus of rupture.

Burg and Ost (1992) found that the ratio of the moduli of rupture of moist-cured specimens to

air-cured specimens ranged from 1.54 to 2.02. From the compiled data, Légeron and Paultre

proposed the following three equations to represent the wide range of experimental values:

fr, min = 8.2√f’c psi [fr, min = 0.68√f’c MPa] (3a)

fr, avg = 11.7√f’c psi [fr, avg = 0.94√f’c MPa] (3b)

fr, max = 14.5√f’c psi [fr, max = 1.20 √f’c MPa] (3c)

where fr, min, fr, avg, and fr, max are the minimum, average, and maximum values of the modulus of

rupture. They recommended that fr, min be used for “serviceability checks that include deflection

and crack control”, and fr, max “to ensure that the flexural members behave in a ductile manner”.

They also stated that when scale and curing effects are accounted for, this value is similar to that

suggested by ACI 318.

As previously stated, ACI 363R-92 reported the findings of Carrasquillo, et al. (1981) as

well as their proposed equations for elastic modulus and the modulus of rupture. The report also

discusses the effect of coarse aggregate type and proportions on the modulus of rupture and

modulus of elasticity. Regarding the Poisson’s ratio of concrete, ACI 363 concluded that the

values found for high-strength concrete were comparable to the expected values for normal-

strength concrete [ACI 363R-92 1997].

5

1.3 Relationship to NCHRP Project 12-64

To expand the applicability of the AASHTO LRFD Bridge Design Specifications, the

NCHRP initiated four projects. NCHRP Project 18-07 was initiated to study prestress losses in

pretensioned concrete girders (Tadros 2003). NCHRP Project 12-56 was initiated to study shear

in reinforced and prestressed concrete members. NCHRP Project 12-60 was established to study

bond and development length in reinforced and prestressed concrete. The goal of the fourth

project, NCHRP Project 12-64, was to recommend revisions to the LRFD Specifications to

extend flexural and compression design provisions for reinforced and prestressed concrete

members to concrete compressive strengths up to 18,000 psi (124 MPa). The project includes a

series of experiments on three target compressive strengths of 10,000, 14,000, and 18,000 psi (69

MPa, 97 MPa, and 124 MPa). The experiments include the following:

1. Material properties tests:

Axial compression tests of 4 x 8-in. (100 x 200-mm) and 6 x 12-in. (150 x 300-

mm) cylinders to determine compressive strength and elastic modulus

Flexural tests of 6 x 6 x 20-in. (100 x 100 x 510-mm) beams to determine

modulus of rupture

Axial creep tests of 4 x 12-in. (100 x 300-mm) cylinders to determine creep

properties

Shrinkage tests of 3 x 3 x 12-in. (50 x 50 x 300-mm) prisms to determine

shrinkage properties

Eccentric axial compression tests of 9 x 9 x 40-in. (230 x 230 x 1,020-mm)

eccentric bracket specimens to determine parameters of the rectangular stress

block

6

2. Structural tests:

Concentric and eccentric axial loading of 9 x 12 x 40-in. (230 x 300 x 1,020-mm)

reinforced concrete columns with different longitudinal and transverse steel

reinforcement to verify design equations for columns

Axial-flexural loading of 9 x 12 x 40-in. (230 x 300 x 1,020-mm) reinforced

concrete columns to verify design equations for short columns

Transverse loading of 9 x 12 x 132-in. (230 x 300 x 3,350-mm) reinforced

concrete beams with different reinforcement ratios to verify flexural design

equations

Transverse loading of prestressed AASHTO girders with different composite deck

configurations to verify the applicability of flexural design equations to

prestressed high-strength concrete

With the exception of the prestressed AASHTO girders, the specimens for each target

compressive strength were generally cast from two truck-mixed batches. The first batch was

used to make the specimens for the material properties tests. The second batch was used to cast

the structural test specimens. The two batches were made using the same materials and mixture

proportions. Excluding creep and shrinkage, the experiments listed above that pertain to the

material properties of concrete and the analysis of the resulting data are the subject of this thesis.

1.4 Structure of the Thesis

This thesis is comprised of five chapters. Chapter one, this chapter, is an introduction to

the development of high-strength concrete, and also includes a summary of previous research

related to the material properties of high-strength concrete. Chapter 2 describes the preliminary

7

work performed to determine appropriate mixture proportions and to select the most effective

method of end surface preparation for testing high-strength concrete cylinders. Chapter 3

summarizes the experimental program and details the tests conducted to determine the

compressive strength, elastic modulus, Poisson’s ratio, and modulus of rupture of high-strength

concrete. In Chapter 4, the results from the tests are analyzed and compared to the values

predicted by current code equations. The final chapter, Chapter 5, presents the conclusions that

resulted from this study.

8

2. PRELIMINARY WORK

2.1 Trial Batches

The objectives for the NCHRP Project 12-64 include developing a range of three

different concrete strengths between 10,000 and 18,000 psi (69 and 124 MPa). The

initial target strengths were set as 10,000, 14,000, and 18,000 psi (69, 97, and 124 MPa).

In order to attain these strength levels, it was necessary to conduct numerous trial batches

to determine the appropriate mixture proportions.

It was the intent of this project to study specimens cast using commercially

produced concrete. Therefore, the project team chose the materials based on the

expectation that they would need to be locally and commercially available for use by a

ready-mixed concrete supplier.

Selection of coarse aggregate can significantly affect the compressive strength

and elastic modulus of concrete. The type of coarse aggregate used in concrete

production is typically dictated by the geographic location of the concrete producer. For

instance, near the coast of North Carolina, the coarse aggregate typically used is marine

marle. This type of aggregate produces concrete with lower compressive strength and

lower modulus of elasticity when compared to concrete made with crushed granite which

can be found in the central part of North Carolina. Geographic variations in coarse

aggregate types are present throughout the country and are important to consider when

analyzing research from various sources.

The source of the coarse aggregate for this project was chosen because of its

reputation in being able to produce aggregate stronger than most other sources in the

region. The size of the coarse aggregate was selected based on the clear spacing of the

9

steel reinforcement in the large-scale test specimens for the NCHRP Project 12-64. The

selection of type and sources of the other materials was based primarily on their usage by

the Ready-Mixed Concrete Company, which provided assistance with mixture

development and large-scale batching throughout this project.

The coarse aggregate was obtained from Carolina Sunrock Corporation. The

aggregate selected was #78M crushed stone quarried in Butner, North Carolina. The

nominal maximum size aggregate of #78M stone is 3/8 in. (10 mm). According to a

report of test results provided by the aggregate producer, this material met the

requirements of ASTM C 33, Class 5S, and AASHTO M 80 Class A Coarse Aggregate in

Portland Cement Concrete. Additional information about the coarse aggregate can be

found in Appendix A.

Two types of fine aggregate were used depending on the target compressive

strength. The first type of fine aggregate was a natural sand used by the Ready-Mixed

Concrete Company in all of their concrete mixtures. The results of a sieve analysis

performed at NCSU are shown in Appendix A. The second type of fine aggregate used

was a manufactured sand produced by Carolina Sunrock Corporation. Both the

manufactured sand and the coarse aggregate were produced from material mined in the

same quarry. Details about the material properties of the manufactured sand are given in

Appendix A.

The cement used for this study was a Type I/II cement produced by Roanoke

Cement. The fly ash producer was Boral Material Technologies and the silica fume

producer was Elkem Materials, Inc. Both the high-range water-reducing and the

retarding admixtures were manufactured by Degussa Admixtures, Inc.. The high-range

10

water-reducing admixture (HRWRA) used was Glenium® 3030. The retarding

admixture used in the initial laboratory trial batches was Pozzolith® 300R. DELVO®

Stabilizer was used in later laboratory batches and the batches used to cast the test

specimens for the project.

The goal of the first set of laboratory trial batches was to attain a compressive

strength of 18,000 psi (124 MPa). Previous trial batches developed at NCSU for the

NCHRP 12-64 Interim Report resulted in compressive strengths in excess of 16,000 psi

(110 MPa) at 28 days. The mixture proportion that resulted in the highest 28-day

strength (shown in Table 2.1) was chosen to be the starting point for the development of

the mixture proportions for this study.

An experimental parametric study was carried out in March 2004 by making 12

1.5-cubic-feet batches with varying mixture proportions (See Table 2.2). The base or

reference mixture was labeled Mixture ID #1. Mixtures 2 and 3 were derived from

mixture 1 by varying the water/cementitious materials (w/cm) ratio. It was believed that

the w/cm ratio for mixture 1 was too low, therefore mixture 2 was used as the base for

deriving the other mixtures because its w/cm ratio was 0.25.

Figure 2.1 - Preparing Materials for Trial Batches

11

Figure 2.2 - Filling Cylinder Molds

Table 2.1 – Mixture Proportions Previously Developed at NCSU

Material lbs/yd3 (kg/m3)

Cement (Type I/II) 960 (570) Microsilica Fume (Densified) 80 (47) Sand (Natural) 1220 (725) Rock (Diabase 78M) 1830 (1085) Water 230 (136) HRWRA** – oz./cwt (mL/100 kg) * 26 (1695) Retarding Agent - oz./cwt (mL/100 kg) * 2.6 (170) * Ounces per 100 pounds of cementitious materials (mL per 100 kg cementitious materials) ** High-Range Water-Reducing Admixture

12

Table 2.2 - Trial Batches for Target Strength of 18,000 psi (124 MPa)

Mixtures Material 1 2 3 4 5 6 7 8 9 10 11 12

Cement (Type I/II) - lbs/yd3 (kg/m3)

960 (570)

935 (555)

904 (536)

907 (538)

729 (433)

546 (324)

703 (417)

887 (526)

998 (592)

960 (570)

975 (578)

960 (570)

Microsilica Fume (Densified) - lbs/yd3 (kg/m3)

80 (47)

78 (46)

75 (44)

101 (60)

77 (46)

76 (45)

75 (44)

74 (44)

83 (49)

80 (47) - -

Slag - lbs/yd3 (kg/m3) - - - - 198

(117) 280

(166) - - - - - - Fly Ash - lbs/yd3 (kg/m3) - - - - -

80 (47)

192 (114) - -

140 (83) -

140 (83)

Micron3 - lbs/yd3 (kg/m3) - - - - - - - - - - -

100 (59)

Sand (Natural) - lbs/yd3 (kg/m3)

1190 (705)

1195 (710)

1180 (700)

1190 (705)

1185 (705)

1190 (705)

1185 (705)

1230 (730)

1020 (605)

945 (560)

1275 (755)

915 (545)

Rock (Diabase 78M) - lbs/yd3 (kg/m3)

1830 (1085)

1830 (1085)

1830 (1085)

1830 (1085)

1830 (1085)

1830 (1085)

1830 (1085)

1880 (1115)

1910 (1135)

1830 (1085)

1830 (1085)

1830 (1085)

Water - lbs/yd3 (kg/m3) 242

(144) 250

(148) 267

(158) 250

(148) 250

(148) 242

(144) 242

(144) 236

(140) 267

(158) 275

(163) 242

(144) 283

(168) HRWRA** - oz./cwt (mL/100 kg) *

36 (2345)

36 (2345)

36 (2345)

36 (2345)

36 (2345)

33 (2152)

36 (2345)

36 (2345)

36 (2345)

36 (2345)

36 (2345)

20 (1305)

Retarding Agent - oz./cwt (mL/100 kg) *

3 (195)

3 (195)

3 (195)

3 (195)

3 (195)

3 (195)

3 (195)

3 (195)

3 (195)

3 (195)

3 (195)

3 (195)

w/cm 0.23 0.25 0.27 0.25 0.25 0.25 0.25 0.25 0.25 0.23 0.25 0.24 * Ounces per 100 pounds of cementitious materials (mL per 100 kg cementitious materials) ** High-Range Water-Reducing Admixture

13

The strength results of the 4x 8-in. (100 x 200-mm) cylinders tested ranged from

15,000 to 18,000 psi (103 to 124 MPa) after 28 days. The highest strength resulted from

mixture 2. The strength of mixture 4 was comparable to mixture 2 but its consistency

was significantly stickier. Therefore, the project team chose mixture 2 for the target

strength of 18,000 psi (124 MPa). Also, as a result of these 12 trial batches, it was

determined that while the use of fly ash decreased the strength when compared to using

silica fume only, it greatly improved the workability of the concrete. For this reason, it

was decided to adjust mixture 7 by increasing the w/cm ratio to attain the target strengths

of 10,000 and 14,000 psi (69 and 97 MPa).

Next, additional laboratory batches were made to determine the appropriate w/cm

ratios to reach the target strengths of 10,000 and 14,000 psi (69 and 97 MPa). It was

anticipated that there would be a 10% to 20% strength reduction between the laboratory

batches and truck-mixed batches. To reach a 28-day compressive strength between

11,000 and 12,000 psi (76 and 83 MPa), a w/cm ratio of 0.30 was chosen for mixture 7.

The w/cm ratio was lowered further in subsequent laboratory batches to create the

mixture for the target strength of 14,000 psi (97 MPa). It became apparent that lowering

the w/cm alone was not sufficient to reach a strength high-enough to offset the strength

reduction between laboratory batches and the truck-mixed batch. Two laboratory

mixtures were then made to determine if a manufactured sand made from the same rock

as the coarse aggregate would perform better than the natural sand used by the ready-

mixed supplier. The laboratory mixtures clearly showed the manufactured sand to

improve the strength of the concrete, and therefore was chosen for the study. The

improvement in strength could be a result of the increased angularity and the lack of

14

clays and fine silts in the manufactured sand. The downside to using the manufactured

sand was that it required the use of a larger quantity of HRWRA. The w/cm ratio that

was found necessary to reach the target strength of 14,000 psi (97 MPa) was 0.26.

To finalize the mixture proportions for the target strength of 18,000 psi (124 MPa),

laboratory batches of mixture 2 from the parametric study were repeated using the

manufactured sand. The laboratory batches produced 28-day strengths of approximately

17,000 psi (117 MPa) and 56-day strengths of 18,000 psi (124 MPa). By the time the

18,000 psi (124 MPa) mixture was being finalized, truck-mixed batches of the 10,000 and

14,000 psi (69 and 97 MPa) concrete had been produced and partially tested. The actual

production showed that the strength reduction between the laboratory and truck-mixed

batches was overestimated. For both the 10,000 and 14,000 psi (69 and 97 MPa)

mixtures, the truck-mixed batches resulted in strengths similar to the strengths of their

respective laboratory batches.

The three concrete mixtures for the target strengths of 10,000, 14,000, and 18,000

psi (69, 97, and 124 MPa) that resulted from the preliminary laboratory batches are

shown in Table 2.3.

15

Table 2.3 - Selected Concrete Mixture Proportions

Target Strengths – psi (MPa) Material 10,000 (69) 14,000 (97) 18,000 (124)

Cement (Type I/II) - lbs/yd3 (kg/m3) 703 (417) 703 (417) 935 (555) Microsilica Fume (Densified) - lbs/yd3 (kg/m3) 75 (44) 75 (44) 75 (44) Fly Ash - lbs/yd3 (kg/m3) 192 (114) 192 (114) 50 (30) Sand - lbs/yd3 (kg/m3) 1055 (625) 1315 (780) 1240 (736) Rock (Diabase 78M) - lbs/yd3 (kg/m3) 1830 (1085) 1830 (1085) 1830 (1085) Water - lbs/yd3 (kg/m3) 292 (173) 250 (148) 267 (158) HRWRA - oz./cwt (mL/100 kg) *** 17 (1110) 24 (1565) 36 (2345) Retarding Agent - oz./cwt (mL/100 kg) * 3 (195) 3 (195) 3 (195) w/cm 0.30 0.26 0.25 28-Day Compressive Strength of Laboratory Batch – psi (MPa)

11,450 (78.9)

14,370 (99.1)**

17,090 (117.8)

* Ounces per 100 pounds of cementitious materials (mL per 100 kg cementitious materials) ** Interpolated from Test Results *** High-Range Water-Reducing Admixture

2.2 End Treatment of Cylinders for Compression Tests

Different end treatments for compression test specimens are known to affect the

measured concrete strength and the variability of the resulting data (ACI 363R-98 1998).

When testing high-strength concrete, many of the standard techniques for preparing the

ends of the specimens either do not work or are not practical. ACI Committee 363 (1998)

reported that using sulfur mortar caps may result in greater variability and lower

measured test values. Unbonded neoprene caps have been used in tests of high-strength

concrete with compressive strengths up to 19,000 psi (130 MPa) (ACI 363R-98 1998).

When testing concrete having a compressive strength greater than 7,000 psi (50 MPa),

16

trial tests must be conducted to verify that the neoprene caps are suitable in order to

comply with ASTM C 1231. It was also reported that for compressive strengths greater

than 10,000 psi (70 MPa), grinding the cylinder ends leads to less variability and higher

average compressive strengths. An alternative method listed in ACI 363R-98 is used in

France. Steel molds filled with sand are used to cap the ends of the cylinder (ACI 363R-

98 1998). The end treatment alternatives considered for this project were; (a) using

unbonded neoprene caps in steel retaining rings, (b) grinding the end surfaces and loading

them directly, (c) capping the cylinders with mortar compound, and (d) using steel

retaining rings filled with sand.

Review of studies related to end treatments showed that grinding the cylinders

would provide the highest strength and the lowest coefficient of variation (FHWA-RD-

97-030). Inquiries were made to local material testing companies about the strength of

available mortar compounds. However, no capping material was found stronger than the

concrete specimens. Several concrete specimens were tested in the laboratory to

qualitatively determine the effects of using neoprene caps, sand caps, and ground end

surfaces. Confirming reports by previous researchers, it was found that the ground

cylinders resulted in the highest compressive strengths. Moreover, the ground cylinders

consistently failed in a cone shape. The neoprene caps that were available worked well

up to approximately 12,000 psi (83 MPa). Above 12,000 psi (83 MPa), however, the

neoprene caps were significantly damaged and had to be replaced after two or three uses.

The steel retaining rings filled with sand performed well but gave results consistently

lower than the specimens with ground surfaces. After reviewing the literature and the

17

data from the pilot experiments, it was decided that all the cylinders used for compression

tests would be prepared by grinding both ends.

18

3. Experimental Program 3.1 Batching

Testing the material properties of high-strength concrete is one of several

components of NCHRP Project 12-64. Therefore, the concrete made and tested to

determine the material properties was batched in the same manner as the concrete used

for the large-scale specimens made for the project. The batching and casting procedures

were also intended to follow typical commercial production techniques as closely as

possible.

The concrete used to make the specimens was batched from a “dry” batch plant

operated by a local ready-mixed concrete supplier. The size of each batch of concrete

was 2 cubic yards. Prior to loading the materials into the 10-cubic-yard truck, the

moisture content values for the coarse aggregate and the fine aggregate were determined.

For all target strengths, the total moisture content of the coarse aggregate was determined

by weighing and drying samples per AASHTO T 255 (ASTM C 566). The saturated

surface dry (SSD) moisture content was then subtracted from the total moisture content to

calculate the free moisture content. The batch weights for the added water and the coarse

aggregate were adjusted using the free moisture content.

During normal operation, the total moisture content of the fine aggregate was

measured with a moisture probe located in the bin that holds the fine aggregate prior to

being loaded in to the truck. The computer then automatically compensated for the

moisture content by adjusting the batch weights for the fine aggregate and added water.

For the target strength of 10,000 psi (69 MPa), the sand used was the same as the sand

used by the Ready-Mixed Concrete Co. in all of their concrete batches. Therefore, the

19

moisture in the sand was measured using the normal operating procedure. For the other

two target strengths, a manufactured sand was used. The manufactured sand had never

been used at the plant, thus the moisture probe was not calibrated for use with this

material. As a result, the total moisture content of the fine aggregate was determined by

weighing and drying samples of the material as directed by AASHTO T 255 (ASTM C

566). The saturated surface dry (SSD) moisture content was then subtracted from the

total moisture content to calculate the free moisture content. The batch weights for the

added water and the fine aggregate were adjusted using the free moisture content.

Table 3.1 - SSD Moisture Contents of the Aggregates Used

Natural Sand Manufactured Sand Coarse Aggregate – 78M

Target Strength

10,000 psi (69 MPa)

14,000 and 18,000 psi (97 and 124 MPa)

All Target Strengths

Percent Absorption 0.5 % 0.64% 0.42 %

Figure 3.1 - Testing for Moisture Content of Aggregates

20

Loading of materials into the truck began by adding the densified silica fume by

hand. The silica fume was packaged in 25-lb bags. For all target strengths, the mixtures

contained 75 lb/cy of silica fume, or three bags per cubic yard of concrete. Next, the

truck was positioned in the loading station. Weighing and batching of the cement, fly

ash, aggregates, retarding admixture, and water were carried out by the plant manager

using computer controls.

Figure - 3.2 Loading of Truck at Batch Plant

Figure 3.3 - Control Room at Batch Plant

21

Next, the truck was driven away from the loading station. Before leaving the

plant, approximately 20% of the estimated amount of high-range water reducing

admixture (HRWRA) was added by hand to the truck. The concrete mixture was then

mixed for five minutes. The concrete was visually inspected in the truck and then sent to

the Constructed Facilities Laboratory (CFL) at NCSU.

Upon arrival at the CFL, the concrete was again visually inspected. If needed, a

second dose of HRWRA was added to the concrete which was then mixed for an

additional five minutes. When mixing was completed and the desired workability was

attained, the concrete was discharged from the truck and work began on casting the test

specimens. As the specimens were being prepared, the fresh concrete was tested for

slump (AASHTO T 119, ASTM C 143), air content (AASHTO T 152, ASTM C 231),

and unit weight (AASHTO T 121, ASTM C 138).

3.2 Casting

3.2.1 Casting Overview

The specimens used for the material property tests consisted of 4 x 8-in. (100 x

200-mm) cylinders and 6 x 12-in. (150 x 300-mm) cylinders for determining the

compressive strength and elastic modulus and 6 x 6 x 20-in. (150 x 150 x 510-mm)

beams for determining the modulus of rupture. The number of specimens was such that

three identical specimens cured in the same manner could be tested at a specific testing

age. The testing ages for this project were 1 day, 7 days, 14 days, 28 days, and 56 days.

On each testing day, two of the 4 x 8-in. (100 x 200-mm) cylinders were used to

determine the elastic modulus before being tested to failure. Below is a table illustrating

22

the number of specimens cast, testing ages, and the curing methods used. Further

discussion of the curing methods can be found in Section 3.3.

Table 3.2 - Description of Test Specimens for Each Target Strength

Testing Age (days) Specimen Test Type Curing

Method* 1 7 14 28 56

Total

7-Day Moist Curing 3 3 3 3 3 15

1-Day Heat Curing 3 3 3 3 3 15

4 x

8-in

. (1

00 x

200

-m

m)

Cyl

inde

rs

Axial Compression

Continual Moist Curing 3 3 6

Total Number of 4 x 8-in. (100 x 200-mm) Cylinders 36

7-Day Moist Curing 3 3 6

1-Day Heat Curing 3 3 6

6 x

12-in

. (1

50 x

300

-m

m)

Cyl

inde

rs

Axial Compression

Continual Moist Curing 3 3 6

Total Number of 6 x 12-in. (150 x 300-mm) Cylinders 18

7-Day Moist Curing 3 3 3 3 3 15

1-Day Heat Curing 3 3 3 3 3 15

6 x

6 x

20-in

. (1

50 x

150

x

510-

mm

) B

eam

s

Modulus of Rupture

Continual Moist Curing 3 3

Total Number of 6 x 6 x 12-in. (150 x 150 x 510-mm) Beams 33 * See Section 3.3 for explanation of curing methods.

3.2.2 4 x 8-in. (100 x 200-mm) Cylinders

The 4 x 8-in. (100 x 200-mm) cylinders were cast using plastic molds. The

procedure used to make the specimens was in accordance with AASHTO T 23 (ASTM C

31). The concrete was taken from the truck to the area where the cylinders were made in

a wheelbarrow. The molds were filled in two approximately equal layers. Each layer

was rodded 25 times with a 3/8-in. (10-mm) diameter rod with a hemispherical tip. After

23

rodding each layer, the sides of the molds were tapped to remove air bubbles. Next, the

excess concrete was struck off and the top surface was smoothed using a trowel. Finally,

the specimens were capped and placed in their respective curing locations.

Figure 3.4 - Rodding of 4 x 8-in. (100 x 200-mm) Cylinders

3.2.3 6 x 12-in. (150 x 300-mm) Cylinders

Casting of the 6 x 12-in. (150 x 300-mm) cylinders was similar to the 4 x 8-in.

(100 x 200-mm) cylinders with the differences being that rodding was done using a 5/8-

in. (16-mm) rod, and that the molds were filled in three approximately equal layers.

3.2.4 6 x 6 x 20-in. (150 x 150 x 510-mm) Beams

The 6 x 6 x 20-in. (150 x 150 x 510-mm) beams were cast using steel molds. The

procedure used to make the specimens was in general accordance with AASHTO T 23

(ASTM C 31) except for consolidation. The concrete was discharged from the truck

directly into the molds. The molds were filled until overflowing. Each mold was

24

consolidated with a 1-in. diameter concrete vibrator. Next, the excess concrete was

struck off and the top surface was smoothed with a trowel. The specimens were then

placed in their respective curing locations. Finally, wet burlap was placed on the exposed

concrete surface and then plastic sheets were placed over the tops of the specimens to

prevent moisture loss

Figure 3.5 - Finishing the Surfaces of 6 x 6 x 20-in. (150 x 150 x 510-mm) Beams

3.3 Curing

3.3.1 Overview

The test specimens made for this project were subjected to one of the three

following curing conditions: 7-day moist curing, 1-day heat curing, or continual moist

curing until the time of testing. The curing conditions were chosen to simulate actual

field applications. The 7-day moist curing regiment was selected to represent typical

curing procedures for reinforced concrete members. The 1-day heat-cured specimens

25

were subjected to conditions that are similar to those used in precast concrete plants for

curing prestressed structural members. The continually moist-cured specimens were

cured according to the ASTM standards which are used for quality control testing in the

concrete industry. The ASTM standard curing conditions do not reflect actual field

curing exposures but are used to standardize the curing procedures for the purposes of

certifying the compressive strength of concrete.

High-strength concrete typically has a high cement content and therefore produces

a large amount of heat during the cement hydration process. It is important to note that

the curing temperatures reported in the following discussion are measured in specimens

having volume to surface ratios much smaller than typical structural members.

Temperatures within structural members may be significantly higher which could lead to

lower compressive strength.

3.3.2 7-Day Moist Curing

The specimens subjected to the conditions of 7-day moist curing remained in their

molds at room temperature for 24 hours ± 2 hours. The cylinder molds were equipped

with plastic lids which effectively sealed the specimens, preventing moisture loss. The

beam molds did not have lids so moisture loss from these specimens was prevented by

placing wet burlap on the top surface of the specimens and then covering the specimens

and the burlap with a sheet of plastic (see Figure 3.6). During the first 24 hours of

curing, both the air temperature around the specimens and the internal temperature of a 6

x 12-in. (150 x 300-mm) cylinder were recorded using thermocouples and a data

acquisition system. The cylinder containing the thermocouple was discarded after the

first day of curing. These temperature measurements are shown in Figures 3.7, 3.8, and

26

3.9 for the 10,000, 14,000 and 18,000 psi (69, 97, and 124 MPa) target strengths,

respectively. It is evident from these figures that the maximum internal concrete

temperature was reached more quickly in the 10,000 psi (69 MPa) target strength

concrete than in the concrete mixtures for the other two target strengths. Two factors

contributing to this result were the larger doses of high-range water-reducing admixtures

used in the 14,000 and 18,000 psi (97 and 124 MPa) target strength mixtures and the

elevated ambient air temperature at the time of casting of the 10,000 psi (69 MPa) target

strength concrete. High-range water-reducing admixtures have a retarding effect and

therefore using a larger dose can delay the set time. The 10,000 psi (69 MPa) target

strength concrete set time was also accelerated due to the outside air temperature which

was over 80° F (26.7° C).

After 24 hours, the specimens were removed from their molds and were

submerged in water in curing tanks. The curing tanks were prepared in accordance with

ASTM C 511. The water temperature was maintained at 73.5°F +/- 3.5°F (23°C +/- 2°C)

by heaters equipped with adjustable thermostats. The water was saturated with calcium

hydroxide to prevent leaching of calcium hydroxide from the test specimens. The curing

tanks also contained pumps to circulate the water for the purpose of maintaining a

constant temperature and concentration of calcium hydroxide throughout the tank. On

the 7th day of curing, the specimens were removed from the curing tanks and then stored

in the laboratory until the time of testing. In the laboratory, the ambient temperature was

approximately 72°F (22°C). The relative humidity was approximately 50%.

27

Figure 3.6 - Beam Molds Covered with Wet Burlap and Sealed with a Plastic Sheet

60

70

80

90

100

110

120

130

140

150

160

170

0 5 10 15 20 25 30

Time (Hours)

Tem

pera

ture

(°F

)

15

25

35

45

55

65

75

Tem

pera

ture

(°C

)

Internal Concrete Temperature

Air TemperatureOutside of Mold

Max 109°F (43 °C)

Figure 3.7 – Initial Temperature Time History for the 10,000 psi (69 MPa) Target Strength Under Moist Curing

28

60

70

80

90

100

110

120

130

140

150

160

170

0 5 10 15 20 25 30

Time (Hours)

Tem

pera

ture

(°F

)

15

25

35

45

55

65

75

Tem

pera

ture

(°C

)


Air TemperatureOutside of Mold

Max 88°F (31 °C)


60

70

80

90

100

110

120

130

140

150

160

170

0 5 10 15 20 25 30

Time (Hours)

Tem

pera

ture

(°F

)

15

25

35

45

55

65

75

Tem

pera

ture

(°C

)Internal Concrete Temperature

Air TemperatureOutside of MoldMax 90° F (32° C)


29

Figure 3.10 - Curing Tank

3.3.3 1-Day Heat Curing

Before the initial set of concrete occurred, the heat-cured specimens were

carefully placed by hand in an environmental chamber for 24 hours where the

temperature was controlled to simulate curing procedures used in some prestressed

concrete plants. The cylinder molds were equipped with plastic lids which effectively

sealed the specimens, preventing moisture loss. The beam molds did not have lids so

moisture loss from these specimens was prevented by covering the top surface of the

specimens with wet burlap and then a sheet of plastic (see Figure 3.11).

The temperature in the chamber remained at room temperature for approximately

four to six hours until the internal temperature of the concrete began to rise due to

hydration of the cement. At that point the temperature control program was initiated.

The program consisted of a ramp up to a constant temperature such that the resulting

30

internal concrete temperature would be between 150°F and 160°F (66°C and 71°C). The

elevated temperature was maintained for 10 to 12 hours and then decreased back to room

temperature. Figures 3.12, 3.13, and 3.14 show the temperature time histories in the

chamber for the 10,000, 14,000, and 18,000 psi (69, 97, 124 MPa) target strengths,

respectively. Variations in mixture proportions made it difficult to produce matching

temperature profiles for subsequent batches. For the 14,000 and 18,000 psi (97 and 124

MPa) target strengths, the chamber temperature was adjusted several times so that the

concrete would reach the desired internal temperature range.

Following the 24-hour heat curing, the specimens were removed from their

molds. The specimens were then stored in the laboratory where the temperature was

maintained at approximately 72° F (22°C) and 50% relative humidity until the time of

testing.

Figure 3.11 - Beams Covered with Wet Burlap and Plastic Sheet in the Environmental Chamber

31

60

70

80

90

100

110

120

130

140

150

160

170

0 5 10 15 20 25 30

Time (Hours)

Tem

pera

ture

(°F

)

15

25

35

45

55

65

75

Tem

pera

ture

(°C

)


Air TemperatureInside Chamber

Max 163°F (73 °C)

Figure 3.12 – Initial Temperature Time History for the 10,000 psi (69 MPa) Target

Strength Under Heat Curing

60

70

80

90

100

110

120

130

140

150

160

170

0 5 10 15 20 25 30

Time (Hours)

Tem

pera

ture

(°F

)

15

25

35

45

55

65

75

Tem

pera

ture

(°C

)



Max 153°F (67 °C)

Figure 3.13 – Initial Temperature Time History for the 14,000 psi (97 MPa) Target Strength Under Heat Curing

32

60

70

80

90

100

110

120

130

140

150

160

170

0 5 10 15 20 25 30

Time (Hours)

Tem

pera

ture

(°F

)

15

25

35

45

55

65

75

Tem

pera

ture

(°C

)



Max 154° F (68° C)

Figure 3.14 – Initial Temperature Time History for the 18,000 psi (124 MPa) Target Strength Under Heat Curing

3.3.4 Continual Moist Curing

The continually moist-cured specimens were subjected to the same conditions as

the 7-day moist-cured specimens, except that moist curing continued until the time of

testing.

3.4 Test Procedure

3.4.1 Compressive Strength/Elastic Modulus Test

Cylindrical specimens were used to determine both the compressive strength and

the elastic modulus of the concrete. All of the cylinders used for these tests were first

prepared by grinding both end surfaces to remove irregularities in the surfaces and to

ensure that the ends were perpendicular to the sides of the specimen. Grinding the end

surfaces was accomplished with a rotary grinding machine shown in Figure 3.15. The

33

cylinders were held firmly to the base plate by the clamping apparatus. The cutting

wheel was moved across the top surface of the cylinder removing a thin layer of material.

The machine contained a pump and reservoir system that constantly flooded the ground

surface with water reducing the amount of dust created. Next, the cutting wheel was

lowered approximately 1/32 in. (1 mm) and passed over the surface of the cylinder again.

This process was continued until the top of the cylinder was smooth and free of

irregularities (See Figure 3.17). The cylinder was then turned upside down and the same

procedure was followed for grinding the opposite end of the cylinder. The cylinders were

typically ground at least one day prior to being tested with the exception of the specimens

tested after one day.

Cutting Wheel Concrete

Cylinder

Clamping Apparatus

Figure 3.15 - Grinding Machine

34

Figure 3.16 - Cutting Wheel Passing Over the Cylinder

Figure 3.17 - Cylinder Surface After Grinding

35

Compression tests were performed using both the 4 x 8-in. (100 x 200-mm)

cylinders and the 6 x 12-in. (150 x 300-mm) cylinders. The tests were in accordance with

ASHTO T 22 which corresponds to ASTM C 39. Prior to testing, the diameter of each

cylinder was measured at mid-height in two opposing directions. The average of the two

measurements was later used to calculate the stresses.

The 4 x 8-in. (100 x 200-mm) cylinders were tested in a 500-kip (2,200-kN)

compression machine at testing ages of 1, 7, 14, 28, and 56 days (See Figure 3.18).

Bottom Loading Platen

Spherical Bearing Block

Figure 3.18 - 500-Kip (2,200-kN) Compression Machine

On the day of testing, one specimen from each curing method was first tested

solely for the purpose of determining its compressive strength. Subsequently, the

36

remaining two specimens for each curing method were first used to determine the elastic

modulus and then tested to failure to determine the compressive strength. The use of

specimens for both the elastic modulus test and the compression test is permitted in

Section 6.5 of ASTM C 469.

Per ASTM C 39, the load rate should be 35 +/- 7 psi/sec (0.25 +/- 0.05 MPa/sec).

The rate used in the tests for this project was approximately 40 psi/sec (0.28 MPa/sec). A

rate near the high end of the standard range was used for testing high-strength concrete,

since longer loading time could possibly permit more extensive micro cracking as

compared to normal-strength concrete specimens.

The method used to determine the elastic modulus of the 4 x 8-in. (100 x 200-

mm) concrete cylinders was in general accordance with ASTM C 469. Deflections were

measured with potentiometers attached to two fixed rings. Four vertical potentiometers

were used to measure the axial deflection and two horizontal potentiometers were

attached at mid-height to measure the lateral dilation of the cylinder. The apparatus

consisted of two aluminum rings with screws to attach them to the test specimen. Prior to

attachment the rings were joined by three aluminum bars. The spacing between the

screws on the top ring and the screws on the bottom ring when the aluminum bars were

attached was 4.99 in. This length was later used as the gage length for calculating the

axial strains from the recorded deformation readings.

37

Vertical Potentiometers

Screw for Fastening Apparatus to

Cylinder

Figure 3.19 - Apparatus Prior to Inserting Cylinder – Top View

Screw for Fastening Apparatus to

Cylinder

Aluminum Bar for Temporary Support

of Top Ring Vertical Potentiometer

Figure 3.20 - Apparatus Prior to Inserting Cylinder – Side View

38

The concrete cylinder was then centered horizontally and vertically inside the

apparatus. Next, the screws were tightened, firmly attaching the apparatus to the

cylinder. The temporary aluminum bars connecting the upper and lower rings were then

removed.

Figure 3.21 - Attaching Apparatus to Cylinder with Screws

Figure 3.22 - Removal of Temporary Aluminum Support Bar

39

Figure 3.23 - Fully-Instrumented Cylinder After Removal of Temporary Support Bars

At this point, the cylinder and the apparatus were placed inside the 500-kip

(2,200-kN) compression machine. The specimen was centered on the bearing plates and

the potentiometers were made plum and level.

Figure 3.24 - Specimen in Compression Machine

40

Once the instrument readings were reset to zero, the loading cycles commenced.

The test consisted of three loading cycles. The first loading cycle began at zero applied

load and ended at 40% of the anticipated capacity of the specimen. The anticipated

capacity was determined by the first of the three specimens for each curing method which

was tested only for the purpose of determining the compressive strength. The first

loading cycle was only intended to seat the gauges and the specimen, no data was

recorded. The second and third loading cycles also began at zero applied load and ended

at 40% of the anticipated capacity of the specimen. The deflections and load were

recorded during these two loading cycles and later used to calculate the elastic modulus

and the Poisson’s ratio. After the third loading, the specimen was unloaded and the

horizontal potentiometers were removed. Finally, the specimen was loaded to failure as

the data acquisition system recorded the applied load and the vertical deflections.

The 6 x 12-in. (150 x 300-mm) cylinders for the 10,000 psi (69 MPa) target

strength were tested at 28 and 56 days in the same 500-kip (2,200-kN) compression

machine used to test the 4 x 8-in. (100 x 200-mm) cylinders. Because the load required

to fail the 14,000 and 18,000 psi (97 and 124 MPa) target strength specimens was at or

near the capacity of the smaller machine, those specimens were tested in a 2,000-kip

(8,900-kN) compression machine at the ages of 28 and 56 days. Three cylinders of each

curing method were tested solely for the purpose of determining the compressive

strength. The 2,000-kip testing machine consisted of a fixed top plate and a flat base

plate that was raised and lowered by a hydraulic cylinder. This testing machine can

accommodate specimens over 40 in. (1 m) tall. Therefore it was necessary to place

several thick steel plates below and above the 6 x 12-in. (150 x 300-mm) cylinders. The

41

additional plates above the specimen were attached to the fixed top plate with bolts.

Since there was no way of fixing a spherical bearing to the top plate of the machine, a

spherical bearing plate was placed immediately below the test specimen.

The load rate was maintained within the same range of 35 +/- 7 psi/sec (0.25 +/-

0.05 MPa/sec). The load was recorded by a data acquisition system. Plexiglas and

plywood were placed around the testing machine for safety reasons due to the explosive

failure of the high-strength concrete specimens.

Compression Machine Data

Acquisition System

Plexiglas

Figure 3.25 - 2,000-kip (8,900-kN) Compression Machine

42

6 x 12-in. (150 x 300-mm) Cylinder

Spherical Bearing Plate

Figure 3.26 - 6 x 12-in. (150 x 300-mm) Cylinder in Compression Machine

3.4.2 Modulus of Rupture

The modulus of rupture tests were carried out using the 6 x 6 x 20-in. (150 x 150

x 510-mm) beams. Irregularities caused by the seams in the beam molds protruding

above the plane of the loading surfaces of the specimen were removed by hand using a

grinding stone. Next, marks were made on the specimen to align it with the supports and

the two loading points. The specimen was then placed in the testing frame (See Figure

3.27) and oriented so that the specimen is turned on its side with respect to its position as

molded as specified in ASTM C 78. A 90-kip (400-kN) hydraulic jack mounted inside a

structural steel test frame applied the load. A load cell measured the applied load. Below

the load cell, there was a spherical head and a plate/roller assembly to distribute the load

evenly to the two loading points on top of the specimen. The span length of the specimen

was 18 in. (460 mm) and the spacing between supports and the nearest loading point as

well as the space between the two loading points was 6 in. (153 mm).

43

Figure 3.27 - Modulus of Rupture Test Setup

The modulus of rupture test was conducted in accordance with AASHTO T 97,

which corresponds to ASTM C 78. The hydraulic jack was operated with a hand pump.

The load was applied such that the stress at the extreme bottom fiber of the specimen

increased at a rate of approximately 150 psi/sec. Load readings from the load cell were

recorded using a data acquisition system. After the test, the dimensions of the fractured

surface were measured. Three measurements were taken in each direction (height and

width). The average distance in each direction was later used to calculate the stress at the

extreme bottom fiber of the beam.

44

4. TEST RESULTS AND DISCUSSIONS

The scope of this project included tests to determine the compressive strength, elastic

modulus, Poisson’s ratio, and modulus of rupture for three levels of high-strength concrete

having target strengths of 10,000 psi (69 MPa), 14,000 psi (97 MPa), and 18,000 psi (124 MPa).

The mixture proportions for the three target strengths were determined from trial laboratory

batches. The mixtures for the 10,000 psi (69 MPa) and 14,000 psi (97 MPa) concrete strengths

were proportioned to exceed the target strength by 10 to 20 percent assuming that there would be

a strength reduction due to the large batch size, the increased difficulty in maintaining quality

control in truck-mixed batches, and the routine variation to be expected in commercial

production.

In both cases, the strengths of the truck-mixed batches were approximately the same as

the laboratory batches. In the following presentation of the test results, it is apparent that the

compressive strengths for the first two concrete mixtures exceeded their respective target

strengths. The compressive strength of the 18,000 psi (124 MPa) target strength batch however,

failed to reach its desired strength. Since the compressive strength of the third batch was higher

than the strength of the 14,000 psi (97 MPa) target strength batch, it still provided useful

information for expanding and adding to the knowledge base of high-strength concrete material

properties. Despite the variations between the target strengths and the actual measured strengths,

the specimens are referred to according to the values of their initial target strengths. This chapter

provides a summary of the test results. The complete test results are provided in Appendix B.

4.1 Compressive Strength

The effects of curing procedures on the compressive strength measured from 4 x 8-in.

(100 x 200-mm) cylinders at 28 days are illustrated in Figure 4.1. This figure clearly shows that

45

for all three target strengths, cylinders subjected to 7-day moist curing resulted in the highest

compressive strengths at 28 days. It is also evident that the 1-day heat curing typically resulted

in the lowest compressive strength at 28 days. Heat curing is beneficial in increasing the rate of

strength gain at early ages but is detrimental to the strength of concrete at later ages. This

behavior has been attributed to rapid hydration which causes the structure of the cement paste to

be more porous than when cement paste hydrates slowly. Subsequently, higher porosity leads to

decreased compressive strength [Neville 1996]. The ratio of the average measured strength at 28

days of the 7-day moist-cured specimens to the heat-cured specimens was 1.17 for the 10,000 psi

(69 MPa) target strength, 1.10 for the 14,000 psi (97 MPa) target strength, and 1.16 for the

18,000 psi (124 MPa) target strength. Although the majority of the strength gain for the heat-

cured specimens occurred during the first few days, the test results in Figures 4.2, 4.3, and 4.4

show that the strength did continue to increase through 56 days of curing at a very slow rate (less

than 3% between 28 and 56 days).

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

10,000 psi [69 MPa]

14,000 psi [97 MPa]

18,000 psi [124 MPa]

Target Strength

Com

pres

sive

Str

engt

hat

28

Day

s (p

si)

0

20

40

60

80

100

120C

ompr

essi

ve S

tren

gth

at 2

8 D

ays

(MPa

)

28-D

ay M

oist

Cur

ing

28-D

ay M

oist

Cur

ing

28-D

ay M

oist

Cur

ing

7-D

ay M

oist

Cur

ing

7-D

ay M

oist

Cur

ing

7-D

ay M

oist

Cur

ing

1-D

ay H

eat C

urin

g

1-D

ay H

eat C

urin

g

1-D

ay H

eat C

urin

g

Figure 4.1 – Compressive Strength of 4 x 8-in. (100 x 200-mm) Cylinders at 28 Days

46

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

0 10 20 30 40 50 60

Time (Days)

Com

pres

sive

Str

engt

h (p

si)

0

20

40

60

80

100

120

Com

pres

sive

Stre

ngth

(MPa

)

Continual Moist Curing

7-Day Moist Curing

1-Day Heat CuringX

Figure 4.2 – Compressive Strength of 4 x 8-in. (100 x 200-mm) Cylinders vs. Time for 10,000 psi (69 MPa) Target Strength

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

0 10 20 30 40 50 60

Time (Days)

Com

pres

sive

Stre

ngth

(psi

)

0

20

40

60

80

100

120

Com

pres

sive

Str

engt

h (M

Pa)


7-Day Moist Curing

1-Day Heat Curing

X


47

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

0 10 20 30 40 50 60

Time (Days)

Com

pres

sive

Str

engt

h (p

si)

0

20

40

60

80

100

120

Com

pres

sive

Str

engt

h (M

Pa)

Continual MoistCuring

7-Day Moist Curing

1-Day Heat Curing

X


As shown in Figure 4.1 as well as in Figures 4.2, 4.3, and 4.4, the compressive strength of

the 28-day moist-cured specimens was found to be less than the compressive strength of the 7-

day moist-cured specimens. This result seemingly contradicts the phenomenon that occurs

routinely with normal-strength concrete where extended moist curing results in a higher

compressive strength. A possible explanation for this behavior is that high-strength concrete has

very low permeability. Within the first few days after casting, the capillary pores within

concrete become segmented by the cement gel created in the hydration process. The time

required to make the capillary pore system discontinuous decreases significantly as the water to

cement ratio decreases. For a water to cement ratio of 0.45, the time it takes for the capillary

pores to become segmented is approximately 7 days [Powers 1959].

Since the concretes used in this study have water to cement ratios of 0.3 and lower, the

capillary pores probably become segmented after only 1 to 2 days of curing. Because the

discontinuous capillaries can no longer convey water from the surface of the specimen to the un-

48

hydrated cement inside, hydration beyond this point in time results from water trapped in the

pores, not from water applied to the surface of the concrete. Therefore, extended moist curing of

high strength concrete should not generate any additional cement hydration when compared to

specimens cured for seven days.

Accordingly, the strengths of 7-day moist-cured and continually moist-cured specimens

should be approximately the same. The test data from this project show, however, that the

specimens moist cured up to the time of testing typically failed at lower strengths than the 7-day

moist-cured specimens. This relationship is most likely an artifact of the testing condition. At

28 days and 56 days the continually moist-cured specimens were tested in the moist condition

while the 7-day moist-cured specimens had been allowed to dry out for several weeks. This

result is in agreement with the general rule that for compressive strength of concrete, dry

specimens exhibit higher strengths than moist specimens. It has been reported that for 5,000 psi

(34 MPa) concrete, drying would increase the compressive strength by as much as 10% [Neville

1996].

The ratio of the compressive strength measured for the 7-day moist-cured specimens to

the strength measured for the 28-day moist-cured specimens was 1.04 for the 10,000 psi (69 MPa)

target strength, 1.11 for the 14,000 psi (97 MPa) target strength, and 1.07 for the 18,000 psi (124

MPa) target strength. It should be noted that the coefficient of variation for the compressive

strength data of the 28-day moist-cured specimens for the 10,000 psi (69 MPa) target strength

was abnormally high when compared to the other curing methods and testing ages. In general,

the variability in the compressive strength values obtained for the continually moist-cured

specimens was higher than the other specimens. The average of the coefficients of variation for

49

the continually moist-cured specimens was 3.73 while the averages for the 7-day moist-cured

and the heat-cured specimens were 2.32 and 1.83, respectively.

Figure 4.5 illustrates how the specimens gained strength over time. For the 10,000 psi

(69 MPa) and 14,000 psi (97 MPa) target strengths, the heat-cured specimens reached

approximately 90% of their 28-day strength during the first day of curing. The specimens made

from the 18,000 psi (124 MPa) target strength concrete also gained the majority of their 28-day

strength in the first day but the percentage was less than those of the other two target strengths.

The slightly lower rate of strength gain for the 18,000 psi (124 MPa) target strength could

possibly be attributed to being exposed to the elevated temperature for a shorter period of time

(See Figure 3.14). The longer set time is consistent with the large dose of superplasticizer used

in this mixture. The retarding effect of the superplasticizer could be offset by preheating the

concrete to a temperature of approximately 100° F (40° C) prior to the initial set.

0

20

40

60

80

100

120

140

Legend 10,000 psi[69 Mpa]

14,000 psi[97 Mpa]

18,000 psi[124 Mpa]

10,000 psi[69 Mpa]

14,000 psi[97 Mpa]

18,000 psi[124 Mpa]

10,000 psi[69 Mpa]

14,000 psi[97 Mpa]

18,000 psi[124 Mpa]

Curing Method and Target Strength

% o

f 28-

Day

Stre

ngth

0 - 1Day

1-7Days

7-14Days

14-28Days

28-56Days

1-Day Heat Curing

7-Day MoistCuring

Continual MoistCuring

7-28Days

7-28Days

7-28 Days

Figure 4.5 – Strength Gain Over Time Expressed as % of the 28-Day Strength

50

As shown in Figure 4.5, test data from the three target strengths showed similar patterns

of strength gain over time related primarily to the curing method used. In particular, the strength

gain of the 10,000 psi (69 MPa) and 14,000 psi (97 MPa) target strengths were nearly identical.

The similarities between the two concrete strengths may be attributed to the fact that they had

identical proportions of cementitious materials. The 14,000 psi (97 MPa) mixture was derived

from the 10,000 psi (69 MPa) mixture by reducing the amount of water and adding sand to

compensate for the reduced volume. In contrast, the proportions of the cementitious materials

were altered to create the 18,000 psi (124 MPa) target strength mixture. In comparison to the

10,000 psi (69 MPa) and 14,000 psi (97 MPa) target strengths, the 18,000 psi (124 MPa) target

strength mixture contained less fly ash and a larger quantity of cement.

Figures 4.2 - 4.4 showed that the continuously moist-cured and 7-day moist-cured

specimens had significant strength gains during the testing intervals prior to the 28th.

Comparing the strength at 56 days to the strength at 28 days, the strength of the continuously

moist-cured specimens increased 4% for the 10,000 psi (69 MPa) target strength, 14% for the

14,000 psi (97 MPa) target strength, and 5% for the 18,000 psi (124 MPa) target strength. These

values may not accurately represent the material properties because the coefficients of variation

for the 10,000 psi (69 MPa) 56-day specimens and the 14,000 psi (97 MPa) 28-day specimens

were abnormally high. The 7-day moist-cured specimens for the 10,000 psi (69 MPa) and

14,000 psi (97 MPa) target strengths had measured strengths at 56 days 6% higher than their

respective 28-day strengths. The increase was less than 1% for the 18,000 psi (124 MPa) target

strength.

The observed failure modes could be categorized according to the testing age and curing

method. All of the heat-cured specimens tended to display explosive, cone-shaped failure modes.

51

For tests done at 1, 7, and 14 days, the failures of the 7-day moist-cured and continually moist-

cured specimens were more gradual. The specimens developed numerous cracks at mid-height

and once the fragments were removed, the remaining portions of the specimens near the ends

were cone-shaped. At 28 and 56 days, the failure modes for the 7-day moist-cured specimens

were typically explosive and cone-shaped. The specimens that were moist cured continually

exhibited a slightly different failure mode at 28 and 56 days. Instead of cracks extending

diagonally from one side of the cylinder at the top to the opposite side at the bottom, the majority

of the cracking occurred only in the outer portion of the cylinder sometimes leaving the core of

the cylinder intact. Because these specimens were tested under moist conditions, this occurrence

could possibly be a result of the pore water pressure causing the concrete near the surface of the

specimen to fail first. Figure 4.6 illustrates the typical failure modes described above. Cracks

observed in all of these failure modes extended through the coarse aggregate particles (see Figure

4.7).

Failure at Early Ages for Continual and 7-Day Moist

Curing

Failure for Heat Curing at all ages and 7-Day Moist Curing

at 28 and 56 Days

Failure for Continual Moist Curing at 28 and 56 Days

Figure 4.6 – Typical Failure Modes of Concrete Cylinders

52

Figure 4.7 – Fractured Coarse Aggregate

In addition to testing the 4 x 8-in. (100 x 200-mm) cylinders, 6 x 12-in. (150 x 300-mm)

cylinders were tested at 28 and 56 days to compare with the results from the smaller cylinders

and to determine whether the specimen size affects the measured compressive strength. Previous

research by Cook (1989) reported that 4 x 8-in. (100 x 200-mm) cylinders have compressive

strengths approximately 5% greater than strengths from 6 x 12-in. (150 x 300-mm) cylinders for

a concrete having a design strength of 10,000 psi (69 MPa). Research by Carino et al. (1994)

showed that the difference was less than 2%. For a range of concrete strengths from 10,000 psi

(69 MPa) to 20,000 psi (138 MPa), Burg and Ost (1992) determined that the difference was

approximately 1% [ACI 363R-98].

Figure 4.8 shows the ratio of the compressive strength measured from 4 x 8-in. (100 x

200-mm) cylinders to the compressive strength measured from 6 x 12-in. (150 x 300-mm)

cylinders tested in this project. Each data point represents the average strength of 4 x 8-in. (100

x 200-mm) strength divided by the average strength of 6 x 12-in. (150 x 300-mm) strength at

53

ages of 28 and 56 days. The results are divided into categories according to curing method. By

averaging the ratios for each curing method, it can be seen that for the 7-day moist-cured

specimens the 4 x 8-in. (100 x 200-mm) cylinders resulted in strengths approximately 5% greater

than the 6 x 12-in. (150 x 300-mm) cylinders. For the heat-cured and continually moist-cured

specimens, the 4 x 8-in. (100 x 200-mm) cylinder strengths were approximately 3% greater. It

should be noted that for the 10,000 psi (69 MPa) target strength specimens, the 4 x 8-in. (100 x

200-mm) cylinders and the 6 x 12-in. (150 x 300-mm) cylinders were tested on the same testing

machine. Testing of the 6 x 12-in. (150 x 300-mm) specimens for the other two target strengths

had to be carried out on a different compression machine because the specimen strength was

approaching the capacity of the machine used to test the 4 x 8-in. (100 x 200-mm) cylinders.

Test data from the larger testing machine showed a greater amount of variation. The average

coefficient of variation for the 6 x 12-in. (150 x 300-mm) cylinders when tested on the smaller

compression machine was 2.1. When tested in the larger compression machine, the average

coefficient of variation was 4.7.

0.85

0.90

0.95

1.00

1.05

1.10

1.15

Curing Method

Com

pres

sive

Str

engt

h of

4

x 8-

in. [

100

x 20

0-m

m] /

6

x 12

-in. [

150

x 30

0-m

m]

28 Days 56 Days*

7-Day Moist 1-Day Heat Continual Moist

* For the 18,000 psi (124 MPa) target strength, the 6 x 12-in. (150 x 300-mm) cylinders were tested after 61 days rather than 56 days because the testing machine was unavailable.

Figure 4.8 – Specimen Size Effect on Compressive Strength

54

4.2 Elastic Modulus

4.2.1 Effects of Curing and Aging

The results from the elastic modulus tests for the three target strengths are shown in Figures

4.9 - 4.11. The figures also show the predicted values from the ACI 318-02 equation, as will be

discussed in Section 4.2.2. From these figures one can see that typical patterns emerge for each

curing method. After one day of curing, the highest value for the modulus of elasticity was

measured in the heat-cured specimens. This was the expected result because the compressive

strength of the heat-cured specimens was also much greater after one day than the specimens

cured by the other two methods. The elastic modulus of the heat-cured specimens increased only

slightly after the first day. The highest measured increase was approximately 14% and occurred

for the 10,000 psi (69 MPa) target strength.

The elastic modulus values for the 7-day moist-cured specimens at testing ages of 7 days or

higher were similar to the values attained from the heat-cured specimens. The 7-day moist-cured

specimens showed significant increases in the elastic modulus values up to the 7th day of curing.

At the ages of 28 and 56 days, specimens that were continually moist cured typically

resulted in higher values of elastic modulus when compared to the heat-cured and 7-day moist-

cured specimens. This occurrence is possibly due to testing the specimens under wet surface

conditions.

55

0.0E+00

1.0E+06

2.0E+06

3.0E+06

4.0E+06

5.0E+06

6.0E+06

7.0E+06

8.0E+06

9.0E+06

0 10 20 30 40 50 60

Time (Days)

Elas

tic M

odul

us (p

si)

0.0E+00

1.0E+04

2.0E+04

3.0E+04

4.0E+04

5.0E+04

6.0E+04

Elas

tic M

odul

us (M

Pa)

7-Day Moist Curing1-Day Heat Curing


X

ACI 318-02 at 28 Days

Figure 4.9 – Elastic Modulus vs. Time for 10,000 psi (69 MPa) Target Strength

0.0E+00

1.0E+06

2.0E+06

3.0E+06

4.0E+06

5.0E+06

6.0E+06

7.0E+06

8.0E+06

9.0E+06

0 10 20 30 40 50 60

Time (Days)

Elas

tic M

odul

us (p

si)

0.0E+00

1.0E+04

2.0E+04

3.0E+04

4.0E+04

5.0E+04

6.0E+04

Elas

tic M

odul

us (M

Pa)

7-Day Moist Curing1-Day Heat Curing


X



56

0.0E+00

1.0E+06

2.0E+06

3.0E+06

4.0E+06

5.0E+06

6.0E+06

7.0E+06

8.0E+06

9.0E+06

0 10 20 30 40 50 60

Time (Days)

Elas

tic M

odul

us (p

si)

0.00E+00

1.00E+04

2.00E+04

3.00E+04

4.00E+04

5.00E+04

6.00E+04

Elas

tic M

odul

us (M

Pa)

7-Day Moist Curing

1-Day Heat Curing


X



4.2.2 Comparison to Codes

The current code equation in ACI 318-02 and the AASHTO-LRFD Bridge Design

Specifications for estimating the elastic modulus of concrete is:

E = 33w1.5√f’c psi (4.1a)

[E = 0.043w1.5√f’c MPa] (4.1b)

where w is the unit weight of the concrete and f’c is the specified compressive strength. As a

result of high-strength concrete research by Carasquillo et al. (1981), the following equation was

proposed and published in ACI 363R-92 for estimating the elastic modulus of concrete mixtures

having strengths ranging from 3,000 psi to 12,000 psi (21 MPa to 83 MPa):

E = (40,000(f’c)0.5 + 106)(w/145)1.5 psi (4.2a)

[(3,320(f’c)0.5 + 6,900)(w/2320)1.5 MPa] (4.2b)

Figure 4.12 shows test results from this research project compared to the ACI 318-02 or

AASHTO-LRFD, and the ACI 363R-92 equations. The measured values were generally in

agreement with the predicted values calculated using the ACI 363R-92 equation regardless of

curing method or compressive strength. The data also supports the findings of ACI 363R-92 that

57

the ACI 318-02 or AASHTO-LRFD equation consistently over-estimates the elastic modulus for

high-strength concrete. The data from Zia (1993) was measured from concrete mixtures

containing coarse aggregate similar to the aggregate used for this project. Figure 4.12 shows that

those values are comparable to the results of this study.

0

2

4

6

8

10

8,000 10,000 12,000 14,000 16,000 18,000 20,000

Compressive Strength (psi)

Elas

tic M

odul

us

(psi

x 1

0^6)

0

10,000

20,000

30,000

40,000

50,000

60,000

55 65 75 85 95 105 115 125 135

Compressive Strength (MPa)

Elas

tic M

odul

us (M

Pa)

7-Day Moist Curing at 28 Days 7-Day Moist Curing at 56 Days1-Day Heat Curing at 28 Days 1-Day Heat Curing at 56 DaysContinual Moist Curing at 28 Days Continual Moist Curing at 56 DaysACI 318-02 (AASHTO-LRFD) Data by Others *ACI 363R-92 Zia (1993) - Crushed Granite

ACI 318-02 (AASHTO-LRFD)

ACI 363R-92

Figure 4.12 – Elastic Modulus vs. Compressive Strength

* Sources for this data were Le Roy (1996), Dong and Keru (2000), Chin and Mansur (1997), Carrasquillo et al. (1981), Khan et al. (1995), Iravani (1996), and Cusson and Paultre (1994).

4.3 Poisson’s Ratio The Poisson’s ratio was found by first determining the changes in lateral and axial strains

between two points on the stress-strain curve. The lower point was defined by an axial strain

value of 50 με. The upper point was defined by an axial stress value of 40% of the peak stress.

The Poisson’s ratio was calculated by dividing the change in lateral strain by the change in axial

strain. The values of Poisson’s ratio for concrete determined from the test specimens showed

large amounts of variation. Figure 4.13 shows no apparent correlation between the Poisson’s

ratio and the compressive strength for any of the batches. In addition, from Figure 4.14 it is

apparent that curing procedures and age have little or no effect on the Poisson’s ratio. The

58

average Poisson’s ratio for all of the specimens tested was 0.17 with a standard deviation of 0.07.

The generally accepted range for the Poisson’s ratio of normal-strength concrete is between 0.15

and 0.25, while it is generally assumed to be 0.20 for analysis [Nawy 2001]. The test data from

this project suggest that it is reasonable to apply the same assumed value for high-strength

concrete as that of the normal-strength concrete.

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0 10 20 30 40 50 6

Time (Days)

Pois

son'

s R

atio

0

10,000 psi Target Strength (69 MPa)14,000 psi Target Strength (97 MPa)18,000 psi Target Strength (124 MPa)10 k i li

Figure 4.13 – Poisson’s Ratio vs. Time for Various Concrete Strengths

0.000.050.100.150.200.250.300.350.400.450.50

0 10 20 30 40 50 60

Time (Days)

Pois

son'

s R

atio

7-Day Moist-CuredHeat-CuredContinually Moist-CuredH t C d A

Figure 4.14 – Poisson’s Ratio vs. Time for Various Curing Methods

59

4.4 Modulus of Rupture 4.4.1 Effects of Aging and Curing The results from tests performed during this project showed that the modulus of rupture is

significantly affected by curing conditions. From Figures 4.15, 4.16, and 4.17 it is evident that

following the removal of the 7-day moist-cured specimens from the curing tank the modulus of

rupture sharply declined. Similarly, the 1-day heat-cured specimens showed reduced values for

the modulus of rupture following their removal from the molds which prevented moisture loss

during the first day of curing.

In both cases the reduced modulus of rupture is consistent with the presence of cracks

initiated by drying shrinkage. The low permeability of the high-strength concrete causes

differential shrinkage strains because the moisture trapped in the interior part of the specimens

cannot escape as quickly as the moisture very close to the surface. As the surface concrete

shrinks more rapidly, it is restrained by the concrete inside the specimen and eventually cracks

[Neville 1996]. The photograph in Figure 4.18 illustrates the surface cracking observed in the 7-

day moist-cured specimens several days after removal from the curing tank. These small cracks

cause a reduction in the modulus of rupture because they are extended when the load is applied

[van Mier 1997]. On the other hand, the specimens that were moist cured up until the time of

testing and were never allowed to dry out, showed values for the modulus of rupture sometimes

as high as two times greater than those of the 7-day moist-cured specimens.

By dividing the average measured modulus of rupture by the average elastic modulus for

each target strength, the apparent tensile strain capacities were calculated to compare with tensile

strain capacities measured and reported by Zia, et al. (1993). Some of the concrete mixtures

used in their study contained coarse aggregate from quarries near the source of the aggregate for

60

this project. The 28-day compressive strength of the concrete mixtures with similar aggregate

reported by Zia, et al., were 12,200 psi (84.1 MPa) for a fly ash mixture and 13,420 psi (92.5

MPa) for a silica fume mixture. The measured tensile strain capacities at 28 days for these

concrete mixtures was -160 and -175 microstrains, respectively. The apparent tensile strain

capacity at 28 days of the 10,000 psi target strength concrete used in this study ranged from -120

microstrains for the 1-day heat-cured specimens to -220 microstrains for the continually moist-

cured specimens. Similar values resulted from the calculations for the 14,000 and 18,000 psi (97

and 124 MPa) target strengths. The values ranged from -115 to -235 and -115 to -210

microstrains, respectively.

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

0 10 20 30 40 50

Time (Days)

Mod

ulus

of R

uptu

re (p

si)

0

2

4

6

8

10

12

Mod

ulus

of R

uptu

re (M

Pa)Continual Moist Curing

7-Day Moist Curing

1-Day Heat CuringX

ACI 318-02 at 28 days

Figure 4.15 – Modulus of Rupture vs. Time for 10,000 psi (69 MPa) Target Strength

61

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

0 10 20 30 40 50

Time (Days)

Mod

ulus

of R

uptu

re (p

si)

0

2

4

6

8

10

12

Mod

ulus

of R

uptu

re (M

Pa)

ContinualMoist Curing

7-Day Moist Curing

1-Day Heat Curing

X



0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

0 10 20 30 40 50

Time (Days)

Mod

ulus

of R

uptu

re

(psi

)

0

2

4

6

8

10

12

Mod

ulus

of R

uptu

re

(MPa

)


7-Day Moist Cured

1-Day Heat CuringX



62

Figure 4.18 – Surface Cracking of 7-Day Moist-Cured Specimens After Removal from Curing Tank

4.4.2 Comparison to Codes

Modulus of rupture is an indirect indicator of the tensile strength of the material. Most

design codes include an equation that correlates the modulus of rupture of concrete to its

compressive strength. The current ACI 318-02 equation for estimating the modulus of rupture of

concrete is:

fr = 7.5√f’c psi (4.3a)

[fr = 0.6√f’c MPa] (4.3b)

where fr is the modulus of rupture and f’c is the specified compressive strength. The same

equation is used by AASHTO-LRFD.

Figure 4.19 shows the test data from this project compared to this design code. Also

shown on the figure is the estimated value of the modulus of rupture using the equation

developed by Carrasquillo et al. (1981) and published in ACI 363R-92, as

fr = 11.7√f’c psi (4.4a)

[fr = 0.94√f’c MPa] (4.4b)

63

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000

Compressive Strength (psi)

Mod

ulus

of R

uptu

re (p

si)

0

2

4

6

8

10

12

27.5 47.5 67.5 87.5 107.5 127.5

Compressive Strength (MPa)

Mod

ulus

of R

uptu

re (M

Pa)

ACI 318-02 (AASHTO-LRFD) ACI 363R-927-Day Moist Curing at 28 Days 1-Day Heat Curing at 28 Days7-Day Moist Curing at 56 Days 1-Day Heat Curing at 56 DaysContinual Moist Curing at 28 Days Zia (1993) - Crushed GraniteData by Others *

ACI 363R-92

ACI 318-02(AASHTO-LRFD)

* Sources for this data were Légeron and Paultre (2000), Paultre and Mitchell (2003), and the Noguchi Laboratory.

Figure 4.19 – Modulus of Rupture vs. Compressive Strength

The results shown in Figure 4.19 suggest that the equation published in ACI 363R-92 is a

good estimation of the modulus of rupture measured from specimens that are moist cured

continually up to the time of testing. In most practical applications, the curing period of concrete

is however finite. Therefore, the condition of the concrete may be more similar to the specimens

that were moist cured for 7 days or heat cured for one day. The equation in ACI 318-02 appears

to be more suitable for estimating the modulus of rupture for those specimens. Looking only at

the data from the 7-day moist-cured specimens, a coefficient of 6 used in the design equation

(English units or 0.5 in S.I. units) would most accurately predict this data set.

64

5. CONCLUSIONS

The goal of NCHRP Project 12-64 was to extend the applicability of the flexural and

compression design provisions of the AASHTO LRFD Bridge Design Specifications to high-

strength concrete. The testing program of the project was comprised of reinforced concrete

beam and column tests, prestressed girder tests, and material property tests. The experimental

program for this study is providing a portion of the material property research needed for the

parent project, NCHRP Project 12-64.

The scope of this study included testing several “short-term” material properties of three

truck-mixed batches of high-strength concrete with varying target compressive strengths. The

target strengths were 10,000, 14,000, and 18,000 psi (69, 97, and 124 MPa). In addition to

varying the compressive strength, the effects of curing were studied by employing three curing

methods. Some of the specimens were moist cured for 7 days to simulate curing conditions for

reinforced concrete. Other specimens were heat cured for 1 day to simulate conditions used in

prestressed concrete applications. The remainder of the specimens were moist cured up to the

time of testing according to the ASTM standards which are widely used for quality control

monitoring in the concrete industry. The material properties of concrete mixtures were

monitored over time by testing specimens at intervals of 1, 7, 14, 28, and 56 days.

The specific material properties covered by this study were compressive strength, elastic

modulus, Poisson’s ratio, and modulus of rupture. Analysis was done to correlate the elastic

modulus, Poisson’s ratio, and modulus of rupture to the compressive strength of concrete. In

addition, the relationships found from this research were compared to those specified by the

American Concrete Institute (ACI) and the American Association of State Highway and

Transportation Officials (AASHTO).

65

Below are the conclusions that were made from this research project:

1. At ages of 28 and 56 days, specimens moist cured for 7 days exhibited the highest

compressive strengths among the three different curing methods; 1-day heat curing

generally resulted in the lowest strength. Specimens moist cured up to the time of

testing resulted in strengths slightly lower than the 7-day moist-cured specimens, but

the reduced strength is consistent with the differences in surface moisture conditions

at the time of testing.

2. Comparisons of the compressive strengths of the 7-day moist-cured and the

continually moist-cured specimens suggested that for high-strength concrete, moist

curing beyond 7 days does not result in any significant increase in strength. This

finding is consistent with the low permeability of high-strength concrete and the short

period of time required for the capillary pores to become discontinuous.

3. Average ratios of compressive strengths of the 4 x 8-in. (100 x 200-mm) to the 6 x

12-in. (150 x 300-mm) cylinders for the 7-day moist-cured, 1-day heat-cured, and

continually moist-cured specimens were 1.05, 1.03 and 1.03, respectively.

4. At ages of 28 and 56 days, the continually moist-cured specimens were found to

result in the highest values of elastic modulus. This occurrence is consistent with the

moist surface conditions at the time of testing.

5. The elastic moduli of the 1-day heat-cured and 7-day moist-cured specimens were

comparable despite a difference in compressive strengths.

6. The equation published in ACI 363R-92 provided a good estimate of the elastic

modulus regardless of the curing method or the compressive strength. The equation

from ACI 318-02 overestimated the elastic modulus for all specimens tested.

66

7. The average Poisson’s ratio measured from the test specimens was 0.17 which is

within the range generally assumed for normal-strength concrete (0.15 - 0.25). This

finding suggests that it is adequate to use the same Poisson’s ratio for high-strength

concrete as that of normal-strength concrete.

8. The modulus of rupture for test specimens was reduced significantly when the

specimens were removed from their sealed or moist environments and allowed to dry.

The continually moist-cured specimens which were never allowed to dry out

exhibited modulus of rupture values in some cases twice as great as the values

attained from the 7-day moist-cured specimens.

9. The equation published in ACI 363R-92 provided a good estimate of the modulus of

rupture for the continually moist-cured specimens but overestimated the modulus of

rupture for the 1-day heat-cured and 7-day moist-cured specimens. The equation in

ACI 318-02 was found to more accurately estimate the modulus of rupture for these

two curing methods.

Other members of the research team are continuing to research several other material

properties of high-strength concrete. Tests are currently underway to determine the

equivalent stress-block parameters as well as the creep and shrinkage characteristics of high-

strength concrete. In addition to the material property tests, columns, beams, and prestressed

girders are being tested for the purpose of extending the AASHTO-LRFD flexural and

compression design provisions for use with high-strength concrete.

Innumerable combinations of material proportions and material sources can be used to

make high-strength concrete. Therefore, there is still a need for additional research of the

material properties of high-strength concrete to create a comprehensive data base comparable

67

to that of normal-strength concrete. In particular, the elastic modulus of concrete can be

greatly affected by the type and size of aggregate used. Testing of concretes made from

numerous types of aggregates originating from various parts of the country will be necessary

to improve estimates of the elastic modulus of high-strength concrete.

68

REFERENCES

AASHTO LRFD Bridge Design Specifications, Third Edition, American Association of

State Highway and Transportation Officials, Washington DC, 2004.

ACI Committee 214, “Evaluation of Strength Test Results of Concrete (ACI 214R-02)”,

American Concrete Institute, Detroit, 2002, 14 pp.

ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-02)

and Commentary (318R-02)”, American Concrete Institute, Farmington Hills, MI,

2002, 443 pp.

ACI Committee 363, “State of the Art Report on High-Strength Concrete (ACI 363R-

92)”, American Concrete Institute, Detroit, 1992 (Revised 1997), 55 pp.

ACI Committee 363, “Guide to Quality Control and Testing of High-Strength Concrete

(ACI 363.2R-98)”, American Concrete Institute, Farmington Hills, MI, 1998,

18 pp.

Burg, R. G., and Ost, B. W., “Engineering Properties of Commercially Available High-

Strength Concretes,” PCA Research and Development Bulletin RD104T, 1992.

Carino, N. J., Guthrie, W. F., and Lagergren, E. S., “Effects of Testing Variables on the

Measured Compressive Strength of High-Strength (90 MPa) Concrete,” NISTIR

5405, National Institute of Standards, and Technology, Gaithersburg, 1994,

pp. 141.

Carrasquillo, R. L., Nilson, A. H., and Slate, F. O., “Properties of High Strength Concrete

Subject to Short-Term Loads”, ACI Structural Journal, Vol. 78, No. 3, 1981, pp.

171-178.

Cook, J. E., “10,000 psi Concrete,” Concrete International, V. 11, No. 10, 1989,

69

pp. 67- 75.

Chin, M. S., Mansur, M. A. and Wee, T. H., “Effect of Shape, Size and Casting Direction

of Specimens on Stress-Strain Curves of High-Strength Concrete”, ACI Materials

Journal, Vo. 94, No. 3, 1997, pp. 209-219.

Cusson, D. and Paultre, P., “High-Strength Concrete Columns Confined by Rectangular

Ties”, Journal of Structural Eingineering, Vol. 120, No. 3, 1994, pp. 783-804.

Dong, Z. and Keru, W., “Fracture Properties of High-Strength Concrete”, Journal of

Materials in Civil Engineering, Vol. 13, No. 1, 2001, pp. 86-88.

Iravani, S., “Mechanical Properties of High-Performance Concrete”, ACI Materials

Journal, Vol. 93, No. 5, 1996, pp. 416-426.

Khan, A. A., Cook, W. D. and Mitchell, D., “Early Age Compressive Stress-Strain

Properties of Low, Medium and High Strength Concretes”, ACI Materials

Journal, Vol. 92, No. 6, 1995, pp. 617-624.

Légeron, F. and Paultre, P., “Prediction of Modulus of Rupture of Concrete”, ACI

Materials Journal, Vol. 97, No. 2, 2000, pp. 193-200.

Le Roy, R., “Instantaneous and Time Dependant Strains of High-Strength Concrete”,

Laboratoire Central des Ponts et Chaussées, Paris, France, 1996, 376 pp.

Mirmiran, A., Rizkalla, S., Zia, P., Russell, H., and Mast, R., NCHRP Project 12-64

Interim Report, National Cooperative Highway Research Program, Raleigh, 2003,

pp.118.

Mokhtarzadeh, A. and French, C., “Mechanical Properties of High-Strength Concrete

with Consideration for Precast Applications”, ACI Materials Journal, Vol. 97,

No. 2, 2000, pp. 136-147.

70

Nawy, E. G., Fundamentals of High-Performance Concrete, Second Edition, John Wiley

& Sons, Inc., New York, 2001, pp. 441.

Neville, A. M., Properties of Concrete, Fourth and Final Edition, New York: J. Wiley,

New York, 1996, pp. 884.

Noguchi Laboratory Data, Department of Architecture, University of Tokyo, Japan,

(http://bme.t.u-tokyo.ac.jp/index_e.html).

Paultre, P. and Mitchell, D., “Code Provisions for High-Strength Concrete – An

International Perspective”, Concrete International, 2003, pp. 76-90.

PCI Design Handbook, Fifth Edition, Precast/Prestressed Concrete Institute, Chicago,

1999.

Powers, T. C., Copeland, L. E., and Mann, H. M., “Capillary Continuity or Discontinuity

in Cement Pastes”, Journal of Portland Cement Association Research and

Development Laboratories, Vol. 1, No. 2, 1959, pp. 38-48.

van Mier, J. G. M., Fracture Processes of Concrete, CRC Press, Inc., Boca Raton, 1997,

pp. 448.

Zia, P., Ahmad, S., Leming, M., “High Performance Concretes”, FHWA-RD-97-030,

Federal Highway Administration, 1997.

Zia, P., Ahmad, S., Leming, M., Schemmel, J. J., and Elliot, R. P., “Mechanical Behavior

of High Performance Concrete, Vol. 5 – Very High Strength Concrete”, SHRP

Report C-365, Strategic Highway Research Program, National Research Council,

Washington, D.C., 1993.

71

CITED TESTING STANDARDS

American Society for Testing and Materials (ASTM)

C 31 Practice for Making and Curing Concrete

C 33 Specification for Concrete Aggregates

C 39 Test Method for Compressive Strength of Cylindrical Concrete Specimens

C 78 Standard Test Method for Flexural Strength of Concrete (Using Simple

Beam with Third-Point Loading)

C 138 Standard Test Method for Density (Unit Weight), Yield, and Air Content

(Gravimetric) of Concrete

C 143 Standard Test Method for Slump of Hydraulic-Cement Concrete

C 231 Standard Test Method for Air Content of Freshly Mixed Concrete by the

Pressure Method

C 469 Standard Test Method for Static Modulus of Elasticity and Poisson´s Ratio

of Concrete in Compression

C 511 Standard Specification for Mixing Rooms, Moist Cabinets, Moist Rooms,

and Water Storage Tanks Used in the Testing of Hydraulic Cements and

Concretes

C 566 Test Method for Total Moisture Content of Aggregates by Drying

C 1231 Practice for Use of Unbonded Caps in Determination of Compressive

Strength of Hardened Concrete Cylinders

American Association of State Highway and Transportation Officials (AASHTO)

M 80 Standard Specification for Coarse Aggregate for Portland Cement

Concrete

72

T 22 Standard Method of Test for Compressive Strength of Cylindrical

Concrete Specimens

T 23 Standard Method of Test for Making and Curing Concrete Test Specimens

in the Field

T 97 Standard Method of Test for Flexural Strength of Concrete (Using Simple

Beam with Third-Point Loading)

T 119 Standard Method of Test for Slump of Hydraulic Cement Concrete-

Twentieth Edition

T 121 Standard Method of Test for Mass per Cubic Meter (Cubic Foot), Yield,

and Air Content (Gravimetric) of Concrete

T 152 Standard Method of Test for Air Content of Freshly Mixed Concrete by

the Pressure Method

T 255 Standard Method of Test for Total Ecaparable Moisture Content of

Aggregate by Drying-Twentieth Edition

73

APPENDIX A

Properties of Aggregate

74

Properties of Coarse Aggregate

75

Carolina Sunrock Corporation Physical Properties for #78M Crushed Stone Butner Quarry #178 May 12, 2003

ASTMC 136 Method for Sieve Analysis of Fine and Coarse Aggregates

Average Gradation from Specifications 1/1/01 to 4/25/03 NCDOT

3/4" 1/2" 3/8"

#4 #8

ASTM C117

#200

ASTM C 131

Grading Size "8"

ASTMC88

Grading Size > 3/8" >#4

Combined

ASTMC 142

100.0 100.0 98.7 26.8 3.7

100 98-100 75-100 20-45 0-15

Test Method for Materials Finer than 75-llm (No. 200) Sieve in Mineral Aggregates by Washing

% Finer 0.2%

NCDOT <0.6%

Specifications I AASHTO M 80 I ASTM C 33

< 1_5% III

Test Method for Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine

% Wear 18%

NCDOT <55%

Specifications I AASHTO M 80 I ASTM C 33

<50% •

Soundness of Aggregates by Use of Sodium Sulfate or Magnesium Sulfate ( 5 cycles)

Weighted Specifications % Loss NCDOT I AASHTO M 80 I ASTM C33 0.4% 0.1% 0.5% <15% <12% •

Clay Lumps and Friable Particles in Aggregates

Specifications

% Deleterious L_..:N~C~D~OiT_--1I.!.AA=S=sH6T~0WoM=80=1==A=S=T=M~C~3::::3~ 0.0% <3.2% <2.0% •

Test results indicate that #78 stone meets or exceeds the requirements of ASTM C 33, Class 5S and AASHTO M 80, Class A Coarse Aggregate in Portland Cement Concrete.

Properties of Coarse Aggregate (Continued)

This information was provided by Carolina Sunrock Corporation.

76

Properties of Manufactured Sand

77

Carolina Sunrock Corporation Physical Properties for 2MS Concrete Sand Butner Quarry #178 May 12, 2003

ASTMC 136 Method for Sieve Analysis of Fine and Coarse Aggregates

Average Gradation from 111103 to 4129103 NCDOT

Specifi cations AASHTO M 6 ASTM C 33

318" (9.5mm)

#4 (4 .75mm)

#8 (2 .36mm)

#16 (1.18mm)

#30 (.600mm)

#40 (.425mm)

#50 (.300mm)

#80 (.180mm)

#100 (.150mm)

Fineness Modulus

ASTMC117

#200

ASTMC88

Grading Size Combined

AASHTOT21

ASTM C 142

100.0 99.7 88.7 66.2 48.8 39.4 30.9 18.1 13.3

2.53

100 95-100 84-100 45-95 25-75

8-35

0.5-20

± 0.20

100 ~

95-100 • 80-100 • 50-85 • 25-60 • 10-30 • 2-10 •

±0.20 • Test Method for Materials Finer than 751lm (No. 200) Sieve in Mineral Aggregates by Washing

% Finer 5.0%

NCDOT 0-8

Specifications AASHTO M6 ASTM C 33

<5% • Soundness of Aggregates by Use of Sodium Sulfate or Magnesium Sulfa

( 5 cycles)

Weighted % Loss 0.5%

NCDOT <15%

Specifications AASHTO M6

<10%

Organic Impurities in Fine Aggregates for Concrete

% Organic 0.0%

NCDOT Specifications AASHTO M 6

Clay Lumps and Friable Particles in Aggregates

% Deleterious 0.0%

NCDOT <1 .0%

Specifications AASHTOM80

<3.0%

ASTM C 33

•

ASTM C 33

ASTM C33 <2.0%

Properties of Manufactured Sand (Continued)

This information was provided by Carolina Sunrock Corporation.

78

Carolina Sunrock Corporation Physical Properties for 2MS Concrete Sand Butner Quarry #178

ASTMC29 Unit Weight and Voids in Aggregate

Dry Rodded Unit Weight

Loose Unit Weight

122.0 Iblft3 %Voids

112.9 Ib/ft3 %Voids

ASTM C 128 Specific Gravity and Absorption of Fine Aggregate

33.9%

38.9%

Bulk Specific Gravity (Gsb) Bulk Specific Gravity SSD

Apparent Specific Gravity (Gsa)

2.959 2.981 3.003

% Absorption 0.64%

ASTMC 1252 Fine Aggregate Angularity (Standard Graded Sample)

Uncompacted Air Voids 46.6%

ASTMD2419 Sand Equivalent Value of Soils and Fine Aggregate

Sand Equivalent 84

May 12, 200

Sieve Analysis of Natural Sand

Sieve Size Cummulative % Passing

3/8 in. (9.5 mm) 100.01/4 in. (6.35 mm) 100.0

#4 (4.75 mm) 98.2#8 (2.36 mm) 90.1

#16 (1.18 mm) 72.7#50 (0.30 mm) 12.8

#100 (0.15 mm) 1.6

79

APPENDIX B

Test Data

80

10,000 psi Target Strength - Modulus of Elasticity/Compression Test1 - Day Tests

Specimen Loading Diam. 1 (in.)

Diam. 2 (in.)

Avg. Diam.

(in)

Stress 1 (psi) Stress 2 (psi) Strain 1 Strain 2 Strain at

Peak Stress H. Strain 2 H. Strain 1 Poisson's Ratio E (psi) Avg. E (psi) Avg. E

(psi)

n/an/a2nd 160 2000 5.00E-05 5.13E-04 6.70E-05 1.83E-05 0.11 3.97E+063rd 80 2000 5.00E-05 5.00E-04 7.39E-05 -9.34E-06 0.18 4.27E+062nd 120 1980 5.00E-05 4.91E-04 9.90E-05 2.61E-05 0.17 4.22E+063rd 70 1990 5.00E-05 5.05E-04 8.02E-05 1.66E-05 0.14 4.22E+06n/an/a2nd 70 3790 7.57E-05 8.11E-04 1.09E-04 1.74E-05 0.12 5.06E+063rd 210 3780 9.47E-05 8.11E-04 1.20E-04 1.14E-05 0.15 4.98E+062nd 10 3780 3.47E-04 1.06E-03 6.19E-05 3.53E-05 0.04 5.29E+063rd 30 3780 3.55E-04 1.09E-03 6.78E-05 2.84E-05 0.05 5.10E+06

Conversions Spcimen Labels1 in. = 25.4 mm M-#: 7-Day Moist Curing1000 psi = 6.9 Mpa H-#: 1-Day Heat Curing

A-#: Continual Moist Curing per ASTM Standard

4"x8" Compressive Strength Definitions and CalculationsSpecimen Peak Load (lbs)Stress (psi) Avg. (psi) Stress 1 = Stress at strain approx. = 0.00005

M-1 62830 4950 Stress 2 is approximately 40% of Peak StressM-2 64880 5120 Strain 1 = strain @ Stress 1M-3 65090 5120 Strain 2 = strain @ Stress 2H-1 120730 9510 H. Strain 1 = horizontal strain @ Stress 1H-2 123990 9760 H. Strain 2 = horizontal strain @ Stress 2H-3 120070 9450 Poisson's Ratio = (H. Strain 2 - H. Strain 1)/(Strain 2 - Strain 1)

E = (Stress 2 - Stress 1)/(Strain 2 - Strain 1)*Coefficient of Variation is calculated per ACI 214R-02 as follows: Axial Strains are calculated using a gauge length of 4.988 in.

V = (Standard Deviation of Sample / Average Strength) x 100 Horizontal Strains are calculated using Diam. 1 as the gauge length.The ratings are taken from Table 3.3 (Within-Test Variation forfield control testing).

Excellent

Excellent

*Coeff. Of Variation

M-3

H-1

H-2

H-3

4.12E+06

4.22E+06

5.02E+06

5.19E+06

M-1

M-2

4.03 4.01

4.01

4.02

4.00

4.04

4.17E+06

5.11E+06

4.02 4.02

4.02 4.02

4.02

4.02

4.02

4.04 4.02

5060

9570

4.02

4.02

4.02

1.9

1.7

2.9E-03

2.8E-03

3.2E-03

3.0E-03

81



Diam. 2 (in.)

Avg. Diam.

(in)



(psi)

n/an/a2nd 10 3270 1.05E-04 7.25E-04 3.51E-04 2.68E-04 0.13 5.26E+063rd 40 3270 1.02E-04 7.29E-04 3.51E-04 2.75E-04 0.12 5.15E+062nd 30 3260 4.69E-05 6.48E-04 -1.90E-05 -1.10E-04 0.15 5.37E+063rd 50 3260 5.01E-05 6.52E-04 -3.20E-05 -1.00E-04 0.11 5.33E+06n/an/a2nd 160 4020 5.00E-05 7.47E-04 1.34E-04 1.29E-05 0.17 5.54E+063rd 170 4020 5.74E-05 7.56E-04 1.34E-04 3.83E-05 0.14 5.51E+062nd 300 4030 5.01E-05 7.45E-04 3.83E-05 -1.27E-05 0.07 5.37E+063rd 200 4040 5.07E-05 7.49E-04 5.07E-05 1.88E-05 0.05 5.50E+06



4"x8" Compressive Strength Definitions and CalculationsSpecimen Peak Load (lbs)Stress (psi) Avg. (psi) Stress 1 = Stress at strain approx. = 0.00005




8270

10090

4.02

4.02

4.01


1.9 Excellent

5.20E+06

1.5

5.28E+06

5.48E+06

4.03

4.02

4.02

Excellent

4.02

M-1

M-2

4.06 3.98

4.04

4.03

3.99

4.03 4.01

4.04

4.04

M-3

H-1

2.4E-03

4.00

H-2

4.02

5.52E+06

H-3

2.5E-03

3.1E-03

3.1E-03

5.35E+06

5.43E+06

82



Diam. 2 (in.)

Avg. Diam.

(in)



(psi)

n/an/a2nd No Data3rd No Data2nd 60 4370 6.30E-05 8.76E-04 8.68E-05 -1.30E-05 0.12 5.30E+063rd 60 4370 6.61E-05 8.80E-04 9.57E-05 -1.30E-05 0.13 5.30E+06n/an/a2nd 90 3800 5.00E-05 7.56E-04 1.22E-04 1.03E-05 0.16 5.25E+063rd 60 3800 5.00E-05 7.52E-04 1.22E-04 7.51E-06 0.16 5.33E+062nd 70 3900 5.00E-05 7.83E-04 1.17E-04 1.59E-05 0.14 5.23E+063rd 20 3900 5.00E-05 7.83E-04 1.15E-04 1.71E-05 0.13 5.29E+06



4"x8" Compressive Strength Definitions and CalculationsSpecimen Peak Load (lbs)Stress (psi)Avg. (psi) Stress 1 = Stress at strain approx. = 0.00005




Very Good

M-3

H-1

H-2

H-3

5.30E+06

5.29E+06

5.26E+06

M-1

M-2

3.999 4.048

4.0155

4.013

4.002

4.033

5.30E+06

5.28E+06

4.016 4.0335

4.0105 4.029

4.02425

4.01975

4.02475

4.037 4.0195

10830

9760

4.0205

4.0235

4.028


2.2 Excellent

3.7

3.0E-03

2.9E-03

2.8E-03

83


Specimen Loading Diam. 1 (in.) Diam. 2 (in.)

Avg. Diam.

(in)



(psi)

n/an/a2nd 14.5 4837 5.82E-05 9.11E-04 2.34E-04 1.45E-04 0.10 5.65E+063rd 10.2 4864 5.03E-05 9.26E-04 2.34E-04 1.13E-04 0.14 5.54E+062nd 9 4828 5.19E-05 1.00E-03 6.43E-04 5.92E-04 0.05 5.08E+063rd 10 4837 6.14E-05 1.02E-03 6.30E-04 5.79E-04 0.05 5.04E+06n/an/a2nd 110 4170 6.21E-05 7.58E-04 1.16E-04 1.30E-05 0.15 5.83E+063rd 20 4090 5.56E-05 7.39E-04 1.16E-04 3.24E-05 0.12 5.96E+062nd 110 4070 6.29E-05 7.69E-04 -2.92E-04 -3.44E-04 0.07 5.61E+063rd 50 4060 5.19E-05 7.82E-04 -2.92E-04 -3.69E-04 0.11 5.49E+06n/an/a2nd 300 4510 5.15E-05 8.25E-04 1.59E-04 6.62E-06 0.20 5.44E+063rd 280 4520 4.98E-05 8.33E-04 1.52E-04 1.28E-05 0.18 5.41E+062nd 130 4710 5.28E-05 8.07E-04 1.02E-04 2.40E-07 0.13 6.07E+063rd 190 4710 5.14E-05 8.06E-04 5.02E-04 3.76E-04 0.17 5.99E+06



4"x8" Compressive Strength Definitions and CalculationsSpecimen Peak Load (lbs) Stress (psi) Avg. (psi) Stress 1 = Stress at strain approx. = 0.00005

M-1 151860 11970 Stress 2 is approximately 40% of Peak StressM-2 155580 12260 Strain 1 = strain @ Stress 1M-3 153470 12100 Strain 2 = strain @ Stress 2H-1 127570 10070 H. Strain 1 = horizontal strain @ Stress 1H-2 133700 10540 H. Strain 2 = horizontal strain @ Stress 2H-3 132490 10430 Poisson's Ratio = (H. Strain 2 - H. Strain 1)/(Strain 2 - Strain 1)A-1 150280 11840 E = (Stress 2 - Stress 1)/(Strain 2 - Strain 1)A-2 143670 11290 Axial Strains are calculated using a gauge length of 4.988 in.A-3 149640 11770 Horizontal Strains are calculated using Diam. 1 as the gauge length.

*Coefficient of Variation is calculated per ACI 214R-02 as follows:V = (Standard Deviation of Sample / Average Strength) x 100The ratings are taken from Table 3.3 (Within-Test Variation forfield control testing).

2.6 Excellent

1.2 Excellent

2.4 Excellent

A-1

A-2

A-3

3.99

4.05

4.05

4.06 4.02

12110

10350

4.02

4.02

4.04

4.05

4.00

4.00

4.01

4.02

4.02

4.02M-1

M-2

3.99 4.05

4.03

3.99

3.98

4.01

4.04 3.99

5.60E+06

5.06E+06

5.73E+06

M-3

H-1

H-2

H-3

5.89E+06

5.55E+06

5.33E+06

5.72E+06

4.02

11630

5.43E+06

6.03E+06

4.02

4.02

4.02

2.5E-03

2.6E-03


3.0E-03

3.5E-03

2.9E-03

3.2E-03

84



Avg. Diam.

(in)



(psi)

n/an/a2nd 94 5059 5.11E-05 9.84E-04 8.30E-05 -1.28E-05 0.10 5.32E+063rd 302 5055 9.23E-05 9.96E-04 7.02E-05 1.27E-05 0.06 5.26E+062nd 85 5093 5.37E-05 9.76E-04 8.95E-05 1.27E-05 0.08 5.43E+063rd 67 5190 5.83E-05 1.03E-03 3.25E-04 -1.30E-05 0.35 5.27E+06n/an/a2nd 140 4240 5.25E-05 7.87E-04 1.14E-04 -1.30E-05 0.17 5.58E+063rd 110 4240 5.24E-05 7.93E-04 1.52E-04 -1.30E-05 0.22 5.58E+062nd 180 4240 5.27E-05 7.59E-04 5.67E-05 7.88E-08 0.08 5.75E+063rd 120 4240 5.42E-05 7.67E-04 3.78E-05 1.27E-05 0.04 5.78E+06n/an/a2nd 80 4190 4.89E-05 6.75E-04 8.80E-05 3.20E-05 0.09 6.56E+063rd 70 5000 5.35E-05 8.83E-04 No data No data ------- 5.94E+062nd 70 4970 5.03E-05 7.95E-04 1.70E-04 -6.20E-06 0.24 6.58E+063rd 110 4890 5.20E-05 7.24E-04 1.60E-04 9.90E-08 0.24 7.11E+06






3.3E-03

3.4E-03

3.2E-03

3.0E-03

12130

6.25E+06

6.85E+06

4.02

4.03

4.03

2.7E-03

2.5E-03


6.55E+06

M-3

H-1

H-2

H-3

5.58E+06

5.76E+06

5.32E+06

5.67E+06

4.04

5.29E+06

5.35E+06

M-1

M-2

4.06 3.98

4.00

4.03

4.04

4.03

4.00 4.03

3.99

4.01

4.01

4.02

4.00 4.02

12780

10520

4.02

4.02

4.01

4.04

4.01

4.02

A-1

A-2

A-3

4.00

4.05

4.04

6.3 Poor

2.5 Excellent

2.5 Excellent

85

10,000 psi Target Strength - 6" x 12" Compression Test28 - Day Tests

6"x12" Compressive Strength

Specimen Diam. 1 (in.)

Diam. 2 (in.)

Avg. Diam. (in.)

Peak Load (lbs)

Stress (psi)

Avg. Stress (psi)

M-1 6.02 6.00 6.01 330640 11660M-2 6.00 6.00 6.00 333350 11780M-3 6.01 5.99 6.00 325300 11510H-1* 6.06 5.98 6.02 188480 6630H-2 6.02 6.02 6.02 293610 10320H-3 6.04 5.99 6.01 287830 10140A-1 6.01 5.99 6.00 323770 11460A-2 6.01 6.00 6.00 315570 11150A-3 6.03 5.99 6.01 339260 11970

H-1* was not included in the average because it is an abnormal result.


Spcimen LabelsM-#: 7-Day Moist CuringH-#: 1-Day Heat CuringA-#: Continual Moist Curing per ASTM Standard

Conversions1 in. = 25.4 mm1000 psi = 6.9 Mpa

11650

10230

11530


1.2 Excellent

1.2 Excellent

3.6 Very Good

86




Diam. 2 (in.)

Avg. Diam. (in.)

Peak Load (lbs)

Stress (psi)

Avg. Stress (psi)

M-1 6.00 6.02 6.01 346980 12240M-2 5.99 6.02 6.00 350520 12380M-3 5.99 6.01 6.00 337370 11930H-1 5.99 6.00 6.00 307310 10870H-2 5.99 6.02 6.00 297980 10520H-3 5.99 6.01 6.00 300300 10620A-1 5.98 6.03 6.00 329880 11650A-2 6.03 5.98 6.00 347720 12280A-3 6.00 6.00 6.00 342880 12130

A-3* was left in open air for 1 day between removal from the form and placement in the water bath.Moist-cured specimens were tested below the standard load rate. The rate was approximately 18 psi/sec.




12180

10670

12020


1.9 Excellent

1.7 Excellent

2.7 Excellent

87



Avg. Diam.

(in)



(psi)

n/an/a2nd 70 2490 5.31E-05 6.19E-04 1.58E-04 6.25E-06 0.27 4.28E+063rd 120 2470 5.15E-05 6.05E-04 1.45E-04 -1.30E-05 0.29 4.25E+062nd 210 2490 5.28E-05 5.40E-04 1.28E-04 -1.30E-05 0.29 4.68E+063rd 160 2500 4.97E-05 5.49E-04 1.34E-04 -1.30E-05 0.29 4.69E+06n/an/a2nd 50 5090 6.23E-05 9.42E-04 1.08E-04 -4.50E-05 0.17 5.73E+063rd 50 5090 1.04E-04 9.55E-04 1.08E-04 -4.50E-05 0.18 5.92E+062nd 90 5080 5.92E-05 9.30E-04 1.40E-04 -1.28E-05 0.18 5.73E+063rd 50 5160 8.57E-05 9.53E-04 1.21E-04 -1.28E-05 0.15 5.89E+06







Excellent

Excellent


M-3

H-1

H-2

H-3

4.26E+06

4.68E+06

5.83E+06

5.81E+06

M-1

M-2

4.00 4.04

4.00

4.01

4.00

4.04

4.47E+06

5.82E+06

3.99 4.02

3.99 4.04

4.02

4.01

4.02

4.04 4.02

6170

12750

4.02

4.02

4.03

2.0

1.3

3.1E-03

3.0E-03

3.1E-03

3.3E-03

88



Diam. 2 (in.)

Avg. Diam.

(in)



(psi)

n/an/a2nd 80 4360 5.15E-05 7.52E-04 -7.10E-04 -2.30E-04 No Data 6.11E+063rd 80 4650 5.62E-05 8.07E-04 -2.30E-02 -9.40E-04 No Data 6.09E+062nd 90 4720 5.15E-05 8.07E-04 1.16E-04 -1.30E-05 0.17 6.13E+063rd 90 5070 5.78E-05 8.69E-04 1.29E-04 -1.30E-05 0.18 6.14E+06n/an/a2nd 40 5450 5.63E-05 9.69E-04 2.84E-04 3.88E-05 0.27 5.93E+063rd 30 5440 5.63E-05 9.74E-04 5.17E-04 8.41E-05 No Data 5.90E+062nd 60 5390 7.18E-05 9.91E-04 8.30E-05 -5.10E-05 0.15 5.80E+063rd 70 5390 8.73E-05 1.00E-03 1.00E-04 -4.50E-05 0.16 5.83E+06







11350

13470

4.01

4.01

4.06


5.6 Fair

6.10E+06

1.1

6.12E+06

5.86E+06

4.01

4.01

4.03

Excellent

4.02

M-1

M-2

4.00 4.02

3.96

3.96

4.05

4.05 4.01

4.06

3.99

M-3

H-1

2.9E-03

3.97

H-2

4.05

5.91E+06

H-3

3.1E-03

3.2E-03

3.5E-03

6.13E+06

5.81E+06

89



Avg. Diam.

(in)



(psi)

n/an/a2nd 50 5830 8.10E-05 1.03E-03 1.15E-04 -4.50E-05 0.17 6.09E+063rd 40 5850 8.42E-05 1.04E-03 1.28E-04 -6.50E-06 0.14 6.08E+062nd 120 5850 8.26E-05 1.01E-03 1.59E-04 3.19E-05 0.14 6.18E+063rd 20 5850 6.24E-05 1.02E-03 2.42E-04 1.28E-05 0.24 6.09E+06n/an/a2nd 50 5580 6.24E-05 1.03E-03 2.30E-04 -9.00E-05 0.33 5.72E+063rd 30 5600 6.87E-05 1.05E-03 -1.30E-05 -2.30E-04 0.22 5.68E+062nd 40 5580 6.55E-05 9.32E-04 No Data No Data No Data 6.39E+063rd 30 5660 7.03E-05 9.55E-04 No Data No Data No Data 6.36E+06







Excellent

M-3

H-1

H-2

H-3

6.08E+06

6.13E+06

5.70E+06

6.38E+06

M-1

M-2

3.99 4.03

4.01

4.00

4.00

4.01

6.11E+06

6.04E+06

4.03 3.99

4.04 3.98

4.01

4.01

4.01

3.99 4.00

14530

13990

4.01

4.01

4.01


0.9 Excellent

1.1

3.6E-03

3.5E-03

3.5E-03

3.4E-03

90



Diam. 2 (in.)

Avg. Diam.

(in)



(psi)

n/an/a2nd 242 6027 5.63E-05 1.03E-03 2.26E-04 5.30E-06 0.23 5.94E+063rd 244 5684 5.16E-05 9.47E-04 3.20E-04 0.00E+00 0.36 6.08E+062nd 241 6328 4.97E-05 9.78E-04 2.28E-04 5.56E-05 0.19 6.56E+063rd 341 6234 5.01E-05 9.35E-04 1.85E-04 -3.19E-05 0.25 6.66E+06n/an/a2nd 307 5679 5.15E-05 9.40E-04 1.41E-04 6.02E-06 0.15 6.05E+063rd 305 5680 5.06E-05 9.40E-04 1.35E-04 0.00E+00 0.15 6.04E+062nd 276 5699 5.53E-05 9.69E-04 1.60E-04 0.00E+00 0.18 5.94E+063rd 290 5699 5.56E-05 9.63E-04 1.96E-04 5.06E-05 0.16 5.96E+06n/an/a2nd 338 5575 5.00E-05 8.09E-04 2.09E-04 6.18E-05 0.19 6.90E+063rd 444 5660 4.97E-05 8.07E-04 2.16E-04 2.38E-05 0.25 6.89E+062nd 255 5691 5.54E-05 8.90E-04 1.63E-04 -2.55E-05 0.23 6.51E+063rd 330 5755 5.00E-05 8.86E-04 2.19E-04 -6.00E-06 0.27 6.49E+06






6.5 Poor

4.1 Good

1.6 Excellent

A-1

A-2

A-3

4.00

4.03

4.02

4.02 4.01

15640

14240

4.01

4.02

4.01

4.00

4.00

4.00

3.98

4.02

4.00

4.01M-1

M-2

3.99 4.05

4.01

4.01

4.00

4.03

4.00 4.01

6.01E+06

6.61E+06

6.70E+06

M-3

H-1

H-2

H-3

6.04E+06

5.95E+06

6.31E+06

6.00E+06

4.03

14120

6.89E+06

6.50E+06

4.00

4.01

4.01

2.6E-03

2.9E-03


3.4E-03

3.4E-03

3.5E-03

3.5E-03

91



Diam. 2 (in.)

Avg. Diam.

(in)



(psi)

n/an/a2nd 228 6632 5.30E-05 1.10E-03 2.20E-04 4.40E-05 0.17 6.12E+063rd 272 6636 4.90E-05 1.08E-03 1.93E-04 0.00E+00 0.19 6.17E+062nd 313 6545 5.26E-05 9.99E-04 9.64E-05 8.75E-06 0.09 6.58E+063rd 267 6684 5.02E-05 1.03E-03 1.31E-04 8.72E-06 0.12 6.55E+06n/an/a2nd 159 5808 5.69E-05 9.92E-04 1.32E-04 -8.79E-06 0.15 6.04E+063rd 266 5805 6.85E-05 9.84E-04 1.76E-04 8.77E-06 0.18 6.05E+062nd 202 5813 4.87E-05 9.39E-04 1.05E-04 3.50E-05 0.08 6.30E+063rd 195 5805 5.93E-05 9.30E-04 6.12E-05 8.74E-06 0.06 6.44E+06n/an/a2nd 282 6303 5.14E-05 1.00E-03 1.91E-04 8.71E-06 0.19 6.35E+063rd 241 6295 5.08E-05 1.01E-03 1.83E-04 2.61E-05 0.16 6.31E+062nd 329 6411 4.98E-05 9.72E-04 1.23E-04 -3.50E-05 0.17 6.60E+063rd 248 6623 5.10E-05 1.01E-03 1.58E-04 0.00E+00 0.16 6.65E+06






3.3E-03

3.2E-03

3.6E-03

3.3E-03

16050

6.33E+06

6.62E+06

4.015

4.011

4.0175

3.1E-03

3.0E-03


6.48E+06

M-3

H-1

H-2

H-3

6.05E+06

6.37E+06

6.36E+06

6.21E+06

3.994

6.14E+06

6.57E+06

M-1

M-2

4.047 3.985

4.038

4.029

3.995

4.016

4.021 3.974

4.034

4.027

4.014

3.9975

4.029 4.012

16610

14640

4.0115

4.016

3.994

4.052

3.954

3.991

A-1

A-2

A-3

3.978

4.068

4.044

3.0 Very Good

0.9 Excellent

1.4 Excellent

92


6"x12" Compressive StrengthSpecimen Width 1 Width 2 Avg. Peak Load Stress Avg.

M-1 5.944 5.9985 5.97125 No Data No DataM-2 5.992 5.997 5.9945 No Data No DataM-3 5.973 5.985 5.979 No Data No DataH-1 5.965 5.9845 5.97475 No Data No DataH-2 6.0715 6.0385 6.055 4.08E+05 14150H-3 5.9795 5.987 5.98325 3.64E+05 12930A-1 5.9535 5.989 5.97125 4.34E+05 15500A-2 6.0175 5.9815 5.9995 4.09E+05 14480A-3 5.9775 5.992 5.98475 4.12E+05 14660




No Data

13540

14880


No Data No Data

6.4 Poor

3.7 Very Good

93


6"x12" Compressive StrengthSpecimen Width 1 Width 2 Avg. Peak Load Stress Avg.

M-1 5.987 6.005 5.996 453860 16070M-2 6.108 5.968 6.038 483820 16900M-3 6.034 5.967 6.0005 408360 14440H-1 5.945 6.04 5.9925 398170 14120H-2 5.953 6.024 5.9885 420070 14910H-3 5.987 6.002 5.9945 421140 14920A-1 6.035 5.96 5.9975 391120 13840A-2 6.062 5.926 5.994 426170 15100A-3 5.982 5.991 5.9865 406600 14450

*M-3 appeared to fail early because of misalignment of specimen




15800

14650

14460


7.9 Poor

3.1 Very Good

4.4 Good

94



Diam. 2 (in.)

Avg. Diam.

(in)



(psi)

n/an/a2nd 310 2330 4.93E-05 5.12E-04 1.53E-04 5.11E-05 0.22 4.37E+063rd 300 2330 5.09E-05 5.04E-04 1.66E-04 1.28E-05 0.34 4.48E+062nd 250 2330 5.06E-05 5.28E-04 1.02E-04 6.45E-06 0.20 4.36E+063rd 320 2380 4.92E-05 5.25E-04 1.34E-04 3.17E-05 0.22 4.33E+06n/an/a2nd 340 3980 5.24E-05 6.28E-04 8.95E-05 2.56E-05 0.11 6.32E+063rd 360 3970 5.06E-05 6.26E-04 1.47E-04 6.39E-06 0.24 6.27E+062nd 360 4740 5.04E-05 7.69E-04 1.40E-04 0.00E+00 0.19 6.10E+063rd 350 4740 4.91E-05 7.70E-04 1.09E-04 -2.53E-05 0.19 6.09E+06







H-1 is not included in the average because the value is significantly different from the other two specimens.

3.1E-03

3.1E-03

2.8E-03

2.6E-03

4.01

5990

12200

4.02

4.02

4.01

3.0

4.0

4.38E+06

6.20E+06

4.01 4.03

4.02 4.01

4.02

4.01

4.02

4.02

6.30E+06

6.09E+06

M-1

M-2

4.01 4.03

4.03

4.02

4.01

4.01

4.42E+06

4.34E+06

Excellent

Very Good


M-3

H-1

H-2

H-3

95



Diam. 2 (in.)

Avg. Diam.

(in)



(psi)

n/an/a2nd 403 4869 5.03E-05 7.41E-04 1.41E-04 -6.34E-06 0.21 6.47E+063rd 442 4870 5.00E-05 7.34E-04 3.06E-05 -1.17E-04 0.22 6.47E+062nd no data no data no data no data no data no data no data no data3rd 287 4833 5.04E-05 8.07E-04 1.40E-04 0.00E+00 0.19 6.01E+06n/an/a2nd 371 5.28E+03 5.02E-05 8.32E-04 8.27E-05 1.44E-07 0.11 6.28E+063rd 350 5.28E+03 5.04E-05 8.31E-04 8.93E-05 6.46E-06 0.11 6.31E+062nd 454 5.24E+03 5.06E-05 8.49E-04 1.72E-04 -3.18E-05 0.26 5.99E+063rd 371 5.24E+03 4.91E-05 8.72E-04 1.73E-04 2.54E-05 0.18 5.91E+06







H-2

4.00

6.30E+06

H-3

3.0E-03

3.0E-03

2.9E-03

6.01E+06

5.95E+06

4.01

M-3

H-1

2.8E-03

4.00

M-1

M-2

4.01 4.02

4.03

4.02

4.00

3.99 4.01

4.04

6.47E+06

0.4

6.24E+06

6.12E+06

4.01

4.02

4.00

Excellent

4.01

12000

13130

4.02

4.01

4.01


1.7 Excellent

96



Diam. 2 (in.)

Avg. Diam.

(in)



(psi)

n/an/a2nd 294 5877 5.07E-05 9.21E-04 1.78E-04 6.40E-06 0.20 6.42E+063rd 231 5877 5.05E-05 9.29E-04 1.84E-04 -4.47E-05 0.26 6.43E+062nd 310 6051 5.50E-05 9.26E-04 1.53E-04 6.98E-05 0.10 6.59E+063rd 325 6050 5.19E-05 9.32E-04 1.27E-04 2.53E-05 0.12 6.50E+06n/an/a2nd 316 5435 5.03E-05 8.02E-04 1.84E-04 6.39E-06 0.24 6.81E+063rd 286 5431 5.18E-05 7.97E-04 1.97E-04 -4.47E-05 0.32 6.90E+062nd 426 5577 5.21E-05 8.63E-04 1.27E-04 1.28E-05 0.14 6.35E+063rd 414 5589 4.89E-05 8.68E-04 1.28E-04 -1.25E-05 0.17 6.32E+06







2.8E-03

3.0E-03

2.5E-03

3.0E-03

4.01

14950

13810

4.01

4.01

4.00


1.5 Excellent

1.4

6.48E+06

6.60E+06

4.04 4.00

4.03 4.00

4.01

4.02

4.02

4.01

6.86E+06

6.34E+06

M-1

M-2

4.01 4.01

4.02

4.02

4.02

4.00

6.42E+06

6.55E+06

Excellent

M-3

H-1

H-2

H-3

97



Avg. Diam.

(in)



(psi)

n/an/a2nd 420 6740 5.09E-05 9.92E-04 1.98E-04 3.83E-05 0.17 6.72E+063rd 330 6760 5.19E-05 9.96E-04 2.17E-04 2.57E-05 0.20 6.81E+062nd 440 6600 5.05E-05 9.95E-04 2.48E-04 5.09E-05 0.21 6.52E+063rd 440 6660 5.22E-05 1.00E-03 2.42E-04 4.45E-05 0.21 6.56E+06n/an/a2nd 430 5770 5.33E-05 8.81E-04 5.16E-05 1.91E-05 0.04 6.45E+063rd 370 5760 5.22E-05 8.75E-04 8.33E-05 1.30E-05 0.09 6.55E+062nd 350 5770 5.21E-05 8.70E-04 1.47E-04 6.54E-06 0.17 6.63E+063rd 260 5780 5.33E-05 9.03E-04 1.91E-04 0.00E+00 0.22 6.50E+06n/an/a2nd 390 5950 5.04E-05 8.79E-04 1.85E-04 0.00E+00 0.22 6.71E+063rd 340 6170 5.21E-05 9.12E-04 1.85E-04 1.92E-05 0.19 6.78E+062nd 420 6450 5.03E-05 8.70E-04 2.17E-04 6.05E-06 0.26 7.36E+063rd 460 5940 5.50E-05 7.91E-04 1.92E-04 -6.42E-06 0.27 7.45E+06






3.2E-03

3.3E-03

3.8E-03

3.0E-03

15640

6.74E+06

7.40E+06

4.02

4.02

4.02

2.5E-03

2.8E-03


7.07E+06

M-3

H-1

H-2

H-3

6.50E+06

6.56E+06

6.65E+06

6.53E+06

4.00

6.76E+06

6.54E+06

M-1

M-2

4.02 4.01

4.02

4.02

4.01

4.00

4.03 4.01

4.02

4.01

4.01

4.02

4.02 4.02

16730

14400

4.02

4.01

4.03

4.01

4.03

4.04

A-1

A-2

A-3

4.03

4.01

4.01

2.7 Excellent

1.2 Excellent

0.4 Excellent

98



Diam. 2 (in.)

Avg. Diam.

(in)



(psi)

n/an/a2nd 320 6500 5.22E-05 9.77E-04 1.39E-04 0.00E+00 0.15 6.68E+063rd 260 6500 5.22E-05 9.84E-04 1.40E-04 3.18E-05 0.12 6.70E+062nd 280 6780 5.07E-05 9.73E-04 1.66E-04 1.28E-05 0.17 7.05E+063rd 250 6710 5.07E-05 9.63E-04 1.85E-04 6.34E-06 0.20 7.08E+06n/an/a2nd 200 5840 5.02E-05 8.71E-04 1.35E-04 0.00E+00 0.16 6.87E+063rd 180 5920 5.05E-05 8.86E-04 1.73E-04 -3.17E-05 0.25 6.87E+062nd 340 5890 5.08E-05 9.11E-04 2.29E-04 3.79E-05 0.22 6.45E+063rd 360 5890 5.25E-05 9.22E-04 2.35E-04 5.72E-05 0.20 6.36E+06n/an/a2nd 380 6620 5.06E-05 9.48E-04 1.66E-04 2.53E-05 0.16 6.95E+063rd 290 6620 5.22E-05 9.59E-04 1.91E-04 -1.28E-05 0.22 6.98E+062nd 340 6380 4.75E-05 8.89E-04 1.84E-04 6.38E-06 0.21 7.18E+063rd 380 6380 5.20E-05 8.89E-04 1.91E-04 -6.24E-06 0.24 7.17E+06






2.6 Excellent

3.9 Very Good

2.5 Excellent

A-1

A-2

A-3

4.02

4.01

4.03

4.04 4.02

16810

14690

4.01

4.01

4.02

4.02

4.01

4.01

4.02

4.02

4.02

4.02M-1

M-2

4.03 3.99

4.01

4.01

4.00

4.03

4.03 4.02

6.69E+06

7.06E+06

7.07E+06

M-3

H-1

H-2

H-3

6.87E+06

6.41E+06

6.88E+06

6.64E+06

4.02

16430

6.97E+06

7.17E+06

4.02

4.01

4.02

2.7E-03

2.4E-03


3.0E-03

3.2E-03

3.0E-03

2.9E-03

99




Diam. 2 (in.)

Avg. Diam. (in.)

Peak Load (lbs)

Stress (psi)

Avg. Stress (psi)

M-1 5.98 6.02 6.00 443423 15680M-2 5.94 6.04 5.99 424810 15070M-3 6.00 6.00 6.00 454951 16090H-1 6.02 5.98 6.00 397374 14070H-2 5.96 6.02 5.99 392673 13940H-3 5.98 5.99 5.99 373545 13270A-1 6.00 6.02 6.01 387585 13680A-2 6.03 5.97 6.00 433054 15320A-3 5.97 6.03 6.00 423265 14980




15610

13760

14660


3.3 Very Good

3.1 Very Good

5.9 Fair

100


The cylinders were tested on the 61st day rather than the 56th day because the testing machine was not available.



Diam. 2 (in.)

Avg. Diam. (in.)

Peak Load (lbs)

Stress (psi)

Avg. Stress (psi)

M-1 6.02 5.98 6.00 476750 16860M-2 6.04 5.97 6.01 426360 15050M-3 6.02 5.99 6.00 456000 16120H-1 5.98 6.02 6.00 431770 15270H-2 5.97 6.02 6.00 365990 12960H-3 6.00 5.99 6.00 330610 11710A-1 6.03 5.98 6.00 465150 16430A-2 5.99 6.01 6.00 470430 16650A-3 6.02 5.97 5.99 419960 14900

*M-3 appeared to fail early because of misalignment of specimen




16010

13310

15990


5.7 Fair

13.6 Poor

6.0 Fair

101

10,000 psi Target Strength - Modulus of Rupture TestDay of Test: 1

Edge 1 Middle Edge 2 Avg. Edge 1 Middle Edge 2 Avg.M-1 6.02 6.01 6.00 6.01 5.85 5.90 5.93 5.89 8554 737M-2 6.00 5.99 5.98 5.99 5.90 5.89 5.89 5.89 7633 661M-3 5.99 6.02 6.02 6.01 5.92 5.93 5.93 5.93 6577 561H-1 6.06 6.08 6.12 6.09 6.00 6.02 6.02 6.01 12466 1021H-2 5.96 6.00 6.03 5.99 5.97 6.02 6.02 6.00 No Data No DataH-3 6.09 6.08 6.05 6.07 6.01 6.07 6.07 6.05 12328 998


Conversions1 in. = 25.4 mm1000 psi = 6.9 Mpa Definitions and Calculations

Rate (lb/min) = Sbd^2/L = 1800 lb/minS = Stress at Bottom Fiber = 150 psi/min +/- 25 psi/minL = Span Length = 18 in.Tare Weight - 96.0 lbsTensile Strength = PL/bd^2P = Peak Loadb = Width (in.)d = Height (in.)

653

1009

Specimen Width (in.) Height (in.) Peak Load (lb)

Modulus of Rupture (psi)

Avg. Modulus of Rupture (psi)

102


Edge 1 Middle Edge 2 Avg. Edge 1 Middle Edge 2 Avg.M-1 6.07 6.07 6.06 6.06 6.11 6.12 6.14 6.12 12205 974M-2 5.99 6.02 6.04 6.02 5.93 6.00 6.02 5.98 11115 936M-3 6.02 6.02 6.02 6.02 6.01 5.96 5.93 5.97 10943 927H-1 6.06 6.06 6.04 6.05 6.12 6.14 6.13 6.13 10442 834H-2 5.96 5.96 5.95 5.96 6.00 5.99 6.01 6.00 10568 895H-3 6.06 6.08 6.04 6.06 6.01 6.02 6.03 6.02 9638 798




946

842




103



Spcimen LabelsM-#: 7-Day Moist Curing

Notes: 1. A spike in the applied load occurred at the time of failure of M-1. H-#: 1-Day Heat Curing2. A dry band of concrete about 1/4" thick appears around the heat-cured specimA-#: Continual Moist Curing per ASTM Standard



542

939




104


Edge 1 Middle Edge 2 Avg. Edge 1 Middle Edge 2 Avg.M-1 5.89 5.90 5.90 5.90 6.00 5.95 5.92 5.96 7556 658M-2 5.88 5.86 5.87 5.87 6.02 6.00 5.99 6.00 6832 590M-3 5.88 5.91 5.89 5.89 6.00 5.98 5.97 5.98 7286 630H-1 5.95 5.93 5.92 5.93 6.00 5.99 5.98 5.99 9855 841H-2 6.08 6.09 6.10 6.09 6.03 6.04 6.04 6.03 9116 748H-3 6.08 6.05 6.04 6.06 6.00 5.99 5.95 5.98 9334 784A-1 6.00 5.97 5.98 5.99 6.03 6.03 6.01 6.02 14403 1203A-2 5.89 5.83 5.91 5.87 6.00 6.00 5.97 5.99 15422 1326A-3 5.86 5.87 5.92 5.88 5.99 5.99 5.98 5.99 14959 1286

M-#: 7-Day Moist CuringH-#: 1-Day Heat CuringA-#: Continual Moist Curing per ASTM StandardA-#: Continually Moist-Cured per ASTM Standard



626

791

1271




105






637

785




106




Conversions1 in. = 25.4 mm Definitions and Calculations1000 psi = 6.9 Mpa Rate (lb/min) = Sbd^2/L = 1800 lb/min

S = Stress at Bottom Fiber = 150 psi/min +/- 25 psi/minL = Span Length = 18 in.Tare Weight - 96.0 lbsTensile Strength = PL/bd^2P = Peak Loadb = Width (in.)d = Height (in.)

748

1177




107






1353

994




108






744

1041




109





S = Stress at Bottom Fiber = 150 psi/min +/- 25 psi/minL = Span Length = 18 inL = Span Length = 18 in.Tensile Strength = PL/bd^2P = Peak Loadb = Widthb = Width (in.)d = Height (in.)

721

1000

1587




110






811

978




111






720

1056




112






1082

788




113






724

819




114





Rate (lb/min) = Sbd^2/L = 1800 lb/minS = Stress at Bottom Fiber = 150 psi/min +/- 25 psi/minL = Span Length = 18 inL = Span Length = 18 in.Tensile Strength = PL/bd^2P = Peak Loadb = Widthb = Width (in.)d = Height (in.)

779

736

1480




115






796

837




116

High-strength concrete has been available for many … · Figure 3.18 500-Kip (2,200-kN)...

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