Essential sampling and testing for Site Personnel...Mar 09, 2016 · (3) The flow test (BS EN...

Essential sampling and testing for

Site Personnel

(Concrete Works)

Presented by San Nwe

Goal and Objective

Know must have tests for construction projects.

How to do tests systematically.

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Contents

(1) Sampling (2) Slump Test (3) Flow Test (4) Air Content Test (5) Making Cubes (5-1) Storing Cubes (6) Compressive Test of Cubes (7) Testing Concrete Cores (8) Re-bound hammer test (9) Ultrasonic Pulse Velocity Test

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Purpose of Concrete Tests

To detect the variation of quality of concrete being supplied for a given specification.

To establish whether the concrete has attained a sufficient strength or concrete has set sufficiently for stripping, stressing, de-propping, opening to traffic etc.

To establish whether the concrete has gained sufficient strength for the intended purpose. P

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Tests on fresh concrete

Workability Tests (slump test and Flow Test)

Air Content Test

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Compressive Test of cubes (cylinders)

Testing of cores

Re-bound hammer test

Ultrasonic Pulse Velocity Test

Tests on hardened concrete

(1) Sampling fresh concrete

The standard composite sample (BS EN 12350-1)

To ensure it is representative of the whole truck load a standard sample consists of scoopfuls taken from four different parts of the load and collected in buckets.

Scoopfuls must be taken through the moving stream, as the load is discharged, sampling the whole width and depth – not just the top part. The size of sample taken should be 1.5 times the estimated volume required for testing. P

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(1) Sampling fresh concrete (cont’d)

Let very first concrete go

• Take a scoopful from part 1




Let the last concrete go

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(2) The Slump Test (BS EN 12350-2) Pre

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(2) The Slump Test (Cont’d)

Step 1

• Empty the sampling buckets onto the mixing tray

• Scrape each bucket clean

Step 2

• Thoroughly remix the sample, shovelling into a heap

• Turn the heap over to form another

• Do this three times

Step 3

• Flatten the final heap by repeatedly digging-in the shovel vertically

• Lift the shovel clear each time

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Step 4

• Ensure the slump cone and base plate are clean and damp

• Place the metal plate on solid level base away from vibration or other disturbance

• Place the cone on the plate and stand on the foot-pieces

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Step 5

• Fill the cone in three equal depth layers

• Use the standard slump rod

• Rod each layer 25 times

• Spread the blows evenly

• Heap the concrete above the top of the cone before rodding the third layer over the area

• Make sure the rod just penetrates the layer below

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Step 6

• Top up if necessary

• Use the rod with a sawing and rolling motion to strike the concrete level with the top of the cone.

Step 7

• Carefully clean off spillage from sides and base plate whilst maintaining foot pressure.

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Step 8

• Carefully lift the cone straight up and clear, to a count of between 5 and 10 seconds.

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Step 9

• Lay the rod across the upturned slump cone

• Measure the distance between the underside of the rod and the highest point of the concrete – the true slump

• Record the distance to the nearest 10 mm

• Check and record the kind of slump

• If the slump isn’t true, take a new sample and repeat the test

• If the second slump isn’t true, get advice

• Complete the sampling and testing certificates

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(2-1) Description of workability based on slump

Very dry; slump 0-25mm are used in road construction

Low workability; 10-40mm are used for foundations with

light re-bar

Medium workability; 50-90mm for normal

re-bar placed with vibration

High workability concrete; >100mm

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Description of

workability

Slump (mm)

No slump 0

Very low 5-10

Low 15-30

Medium 35-75

High 80-155

Very high 160 to collapse

Classification of

workability

(EN 206-1 :2000)

Slump (mm)

S1 10-40

S2 50-90

S3 100-150

S4 160-210

S5 >220

(3) The flow test (BS EN 12350-5) Pre

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(3) The flow test (BS EN 12350-5)

First find a suitable location for the flow table.

It must be placed on a firm, flat and level

surface. It may be necessary to prepare an

area for the table.

Step 1

• Empty the sampling buckets onto the mixing tray.

• Scrape each bucket clean.

Step 2

• Thoroughly remix the sample as described

for the slump test.

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Step 3

• Ensure the mould and

table are clean and damp.

• Place the mould on the

centre of the table and

stand on the foot-pieces.

• Fill the mould in two

layers, tamping each

layer ten times with the tamping bar

• If necessary add more concrete to fill the top layer.

• Use the tamping bar to strike the top layer level with the top of the mould.

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Step 4

• Carefully clean off spillage from around the mould and table top.

Step 5

• Wait 30 seconds from striking off

• Carefully lift the mould straight up and clear to a count of between 3 and 6 seconds.

Step 6

• Stabilise the flow table by standing on the toe board at the front of the table.

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Step 7

• Slowly lift the table top by the handle until it reaches the upper stop.

• Allow the table to fall freely.

• Repeat this cycle to give a total of 15 drops.

• Each cycle should take about 4 seconds.

Step 8

• Measure the largest dimension of concrete spread in two directions, parallel to the table edges.

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• Record the flow value as d1 + d2 divided by 2.

• Report any segregation which may have occurred around the sample edge.

• Complete the sampling and testing certificates.

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(3-1) Classification of workability based on Flow Pre

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Consistance Class

(EN 206-1 :2000)

Class Range (mm)

F1 340

F2 350 - 410

F3 420 - 480

F4 490 - 550

F5 560 - 620

F6 630

•Suitable for Very High consistency concretes

•400 mm flow for medium consistency

•> 500 mm flow for high consistency

(3-2) Suggested Valued of Workability of Fresh

Concrete for Different Placing Conditions

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(4) Air Content Test

Pressure Method (ASTM C231)

• Most common method used in the field.

Principle : change in concrete volume when subjected to given pressure.

Assumption : volume change is caused by compression of air.

Principle of Boyle’s law to calculate air content

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(4) Air Content Test

Pressure Method : Procedure

•Add water through petcocks.

•Pump air into air chamber until gauge needle is stabilized on initial pressure line.

•Open valve between air chamber and measuring bowl.

•Read out percentage of air content indicated on gauge.

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(5) Making cubes(BS EN 12390-2) Pre

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(5) Making cubes(BS EN 12390-2)

Collect a composite sample to the standard

method described above Topic (1).

Step 1

• Check that the moulds are clean and lightly oiled with all bolts tightened so that there will be no leakage.

• Ensure that the correct halves of the moulds are used and that the corner lifting pins are correctly located.

• Thoroughly remix the sample as described for the slump test.

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Step 2

• Fill the mould with concrete in 50 mm layers using the tamping bar, compact the concrete with no fewer than 25 tamps for each of the two layers in a 100 mm mould and no fewer than 35 tamps for each of the three layers in a 150 mm mould.

• For very high workability concrete you may not need the minimum number of tamps.

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Step 3

• After tamping of each layer, tap the sides of the mould with the hide hammer until large bubbles of air cease to appear on the surface and the holes left by the tamping bar are closed.

Step 4

• Remove surplus concrete and smooth over with a float.

• Wipe clean the mould edges.

• Number the moulds for

identification and record details.

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Step 5

• Cover each mould with a damp cloth and plastic sheet.

• Store inside at room temperature (15-25C) e.g. on top of the curing tank.

• Protect the cube moulds at all times from high and low temperature (especially sub-zero temperatures) and drying winds.

• Complete the sampling and cube making certificates.

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(5-1) Storing cubes(BS EN 12390-2)

The cubes should be removed from the moulds at between 16 and 72 hours after casting.

Step 1

• Record the maximum/minimum overnight storage temperatures on the certificate.

Step 2

• Slacken all nuts.

• Part the sides of the mould, tapping gently with the hide hammer.

• Lift off carefully.

• Remember new cubes are easily damaged unless handled carefully.

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(5-1) Storing cubes(BS EN 12390-2) Step 3

• Mark each cube with its identification number on two of its cast sides.

Step 4

• Place the cubes in the curing tank.

• Clean and reassemble the moulds.

Step 5

• Check that the water temperature is controlled at 20C ± 2C and the cubes are covered by water.

• Make sure the power supply is not switched off day or night.

• Check the temperature range daily using the maximum/minimum thermometer.

• Keep a record of the readings.

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(5-1) Storing cubes(BS EN 12390-2)

Step 6

• For despatch to test laboratory, wrap the wet cubes in damp cloths, and then plastic bags and pack in trays.

• Attach the certificates for sampling, testing, cube making and storage to the package – along with the order for testing.

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(6) Compressive Test

ASTM British Standard

Specimen geometry Cylinder 150 mm dia.,

300 mm long

Cube 150 mm

Curing temperature 23 ± 2C 20 ± 2C

Loading rate 0.15 to 0.35 MPa/s 0.2 to 0.4 MPa/s

End preparation Required No need

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https://www.youtube.com/watch?v=dtvm7YNsSU0

(6) Compressive Test Pre

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Comparison between Cube Strength Vs Cylinder Strength

fc’ = 0.78 fcu’ For fc’ =2500 psi to 3500

psi

fc’ = 0.80 fcu’ For fc’ >3500 psi to 5000 psi

fc’ = 0.81 fcu’ For fc’ >5000 psi to 6000 psi

fc’ = 0.83 fcu’ For fc’ >6000 psi

CQHP Guide 3.1.4

(6) Compressive Test Pre

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Effect of Height to Diameter Ratio on Cylinder Strength

(7) Testing of Concrete Core

ASTM - C 42

The diameter of core specimens for the determination of concrete compressive strength should preferably be at least three times the nominal maximum size of the coarse aggregate used in the concrete.

It must be at least twice the maximum size of the coarse aggregate in the core sample.

The length of the specimen, when capped, should be nearly as practicable twice its diameter.

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The procedure:

Submerge the test specimens in lime-saturated water at 23.0 +/- 1.7° C for at least 40 h immediately prior to making the compression test.

Test the specimens promptly after removal from water storage.

During the period between removal from water storage and testing, keep the specimens moist by covering with a wet blanket of burlap or other suitable absorbent fabric. P

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The procedure: (Cont’d)

Submerge the test specimens in lime-saturated water at 23.0 +/- 1.7° C for at least 40 h immediately prior to making the compression test.

Test the specimens promptly after removal from water storage.

During the period between removal from water storage and testing, keep the specimens moist by covering with a wet blanket of burlap or other suitable absorbent fabric. P

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The procedure: (Cont’d)

If the ratio of the length to diameter of the specimen is less than 1.94 apply correction factors shown in the Table below;

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Ratio of length of cylinder

to diameter (L/D)

Strength correction

factor

1.75 0.98

1.50 0.96

1.25 0.93

1.00 0.87


The following guidelines are of particular importance in core sampling:

1. The number, size, and location of core samples should be carefully selected to permit all necessary laboratory tests. If possible, use virgin samples for all tests so that there will be no influence from prior tests.

2. For determination of strength the core must have a minimum diameter of greater of three times the maximum nominal size of the coarse aggregate, or 50 mm. P

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The following guidelines are of particular importance in core sampling: (Cont’d)

3. For strength tests, the cores must have a length of at least twice their diameter.

4. Reinforcing steel should not be included in a core to be tested for strength.

5. During drilling of cores, the electrical conduits or prestressing steel must not be disturbed.

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The following guidelines are of particular importance in core sampling: (Cont’d)

6. It is better to drill core through full depth of member to avoid the need of its breaking for extraction. An extra 50 mm is usually drilled to allow for possible damage at the base of the core.

7. At least three cores must be removed at each location in the structure for strength determination.

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(8) Re-bound hammer test

Fundamental principle: Rebound of elastic mass depends on surface hardness.

Surface hardness correlated to strength.

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https://www.youtube.com/watch?v=wZOuJ7L5ojI


Sensitive to local variations in concrete (i.e. presence of a large piece

of aggregate).

Immediately underneath the plunger ->abnormally high rebound

number.

Conversely, the presence of a void in similar position -> very low

results.

It is necessary to take up to 25 readings in an area up to 300 mm2 and

average the results.

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Operation of re-bound hammer

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(9) Ultrasonic Pulse Velocity Test

Fundamental principle: Velocity of sound in solid material

is a function of its elastic property.

Modulus of elasticity

Poisson’s ratio

Density

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https://www.youtube.com/watch?v=d_Fec2nyHEQ


Methods of Measuring Pulse Velocity through Concrete

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The ultrasonic pulse velocity test can give information about the interior of a concrete element and therefore useful to determine:

◦ The homogeneity of the concrete

◦ The presence of voids, cracks or other imperfections

◦ Changes in a given concrete element, e.g.

deterioration due to frost or fire

◦ The value of elastic modulus and dynamic Poisson’s

ratio of the concrete

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Voids in Concrete can be detected by ultrasonic measurement.

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https://www.youtube.com/watch?v=OYzyA5c7A24

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The End

Essential sampling and testing for Site Personnel...Mar 09, 2016 · (3) The flow test (BS EN...

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Transcript of Essential sampling and testing for Site Personnel...Mar 09, 2016 · (3) The flow test (BS EN...