Concrete Tests

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Table of ContentsChapter 1...............................................................................................................................................4

Premix Design........................................................................................................................................4

Preface...............................................................................................................................................4

Standard Mix.....................................................................................................................................4

Chapter 2, Soft Concrete Tests..............................................................................................................6

Slump Test.............................................................................................................................................6

Introduction.......................................................................................................................................6

Objective...........................................................................................................................................6

Theory...............................................................................................................................................6

Equipment.........................................................................................................................................7

Procedure..........................................................................................................................................7

Result.................................................................................................................................................8

Discussion and conclusion.................................................................................................................8

Appendix............................................................................................................................................8

Compacting Factor Test.........................................................................................................................9

Introduction.......................................................................................................................................9

Objectives..........................................................................................................................................9

Theory...............................................................................................................................................9

Apparatus..........................................................................................................................................9

Procedure........................................................................................................................................10

Result and Calculation.....................................................................................................................11

Discussion........................................................................................................................................11

Advantages:.................................................................................................................................12

Disadvantages:.............................................................................................................................12

Conclusion.......................................................................................................................................13

Appendix..........................................................................................................................................13

Vebe Time Test....................................................................................................................................14

Introduction.....................................................................................................................................14

Objectives........................................................................................................................................14

Theory.............................................................................................................................................14

Apparatus........................................................................................................................................15

Procedure........................................................................................................................................16

Discussions......................................................................................................................................16

SAYED ASADULLAHUNISEL, FACULTY OF ENGINEERING, CIVIL DIVISION

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Advantages:.................................................................................................................................16

Disadvantages:.............................................................................................................................17

Conclusion.......................................................................................................................................17

Appendix..........................................................................................................................................17

Chapter 3.............................................................................................................................................18

Destructive Concrete Test...................................................................................................................18

Compressive Strength Test..................................................................................................................19

Introduction.....................................................................................................................................19

Objectives........................................................................................................................................19

Theory.............................................................................................................................................19

Apparatus........................................................................................................................................19

Procedure........................................................................................................................................20

Rate of Loading................................................................................................................................20

Result...............................................................................................................................................21

Precautions......................................................................................................................................21

Discussion........................................................................................................................................21

Conclusion.......................................................................................................................................22

Appendix..........................................................................................................................................22

Flexural Test........................................................................................................................................23

Introduction.....................................................................................................................................23

Objective..........................................................................................................................................23

Theory.............................................................................................................................................23

Apparatus:.......................................................................................................................................24

Procedures.......................................................................................................................................24

Result...............................................................................................................................................25

Discussion........................................................................................................................................25

Conclusion.......................................................................................................................................25

Appendix..........................................................................................................................................25

Chapter 4.............................................................................................................................................26

Non-Destructive test...........................................................................................................................26

Rebound Hammer Test........................................................................................................................27

Introduction.....................................................................................................................................27

Objectives........................................................................................................................................27

Theory.............................................................................................................................................27


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Apparatus........................................................................................................................................27

Procedure........................................................................................................................................28

Result and calculation......................................................................................................................29

General Discussion..........................................................................................................................30

Conclusion.......................................................................................................................................30

Appendix..........................................................................................................................................31

Micro Cover Meter..............................................................................................................................32

Introduction.....................................................................................................................................32

Objective..........................................................................................................................................32

Apparatus........................................................................................................................................32

Procedure........................................................................................................................................33


Discussion........................................................................................................................................33

Conciliation......................................................................................................................................34

Appendix..........................................................................................................................................34

PUNDIT Plus Test.................................................................................................................................35

Introduction.....................................................................................................................................35

Objective..........................................................................................................................................35

Theory.............................................................................................................................................35

Apparatus:.......................................................................................................................................35

Procedure........................................................................................................................................36


Discussion........................................................................................................................................37

Conclusion.......................................................................................................................................37

Appendix.........................................................................................................................................38

Conclusion...........................................................................................................................................39

References...........................................................................................................................................39


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Chapter 1

Premix Design

PrefaceFor the concrete laboratory under the Laboratory 3, we have Slump test, Vebe Time Test, Compacting Factor Test for soften concrete and destructive and non-distractive tests of harden concrete. We started our testing session with the mix design of the concrete proportions. As bellow calculations.

Standard MixG 25 – ST5

1. C= 340kgTA= 1830kg

2. Fine Aggregate= 30100

×1830=549Kg

3. Coars Aggregate=1830−549=1281Kg

4. Water cement ratio=WC

=( 0.45−0.65 )=0.55

5. Water=0.55×3400=187Kg

Our samples:

Total volume=V Cylinder+3×V Cube+V Beam

TotalVolume=(π ×752×300 )+(3×3×100 )+(100×100×500 )=0.013m3

Cement=0.013×340=4.42Kg

Fine Aggregate=0.013×549=7.14Kg

Coarse Aggregate=0.013×1281=16.65Kg

Water=0.013×187=2.43Kg


H=300 mm d=150mm

H=100 mm b=100mm t=100mm

H=100 mm b=100mm L=500mm

X3

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Since we need to consider the wastage of 1.2% so we multiply all the above values to 1.2, thus we have:

Cement=0.013×340=4.42×1.2=5.3KG

Fine Aggregate=0.013×549=7.14×1.2=8.6Kg

Coarse Aggregate=0.013×1281=16.65×1.2=20Kg

Water=0.013×187=2.43×1.2=2.9Kg

We weight the proportions and mixed them well.

Once it ready we did the following tests:

1. Slump Test2. Compacting Factor Test3. Vebe Time Test


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Chapter 2, Soft Concrete Tests

Slump Test

IntroductionThe slump test is a method used to determine the consistency of concrete and to check its uniformity from batch to batch. The consistency, or stiffness, of the concrete shows the fluidity of the concrete indicating how much water has been used in the mix, and is often measured by concrete slump. The stiffness of the concrete mix is often matched to the requirements for the finished product. All concrete mixes are a combination of aggregate (gravel and/or sand), cement and water in varying proportions. The concrete mixture and the ratios of ingredients affect the workability of the end product and the concrete’s final strength (water/cement ratio). In terms of workability only, the higher the slump value, the higher the amount of water and as a result the mixture is more fluid for working the concrete and finishing. The construction industry perceives that higher slump values require less muscular effort to manipulate. The usefulness of the slump test as a predictor of concrete strength is controversial and the shrinkage has traditionally been perceived by the industry as affecting the integrity and quality of the concrete.

ObjectiveTo determine the workability of a sample from fresh concrete of given grate and proportions using the slump test.

TheoryThe apparatus consists of a mold in the shape of a frustum of a cone with a Base and top 8” and 4’ diameter respectively and a height of 12”. The mold is filled with concrete in three layers of equal volume. Each layer is compacted with 25 strokes of a tamping rod. The slump cone mold is lifted vertically upward and the change in height of the concrete is measured. There are four type of slump can be occurred [Figure 1]. And the only type of the slump permissible under ASTM C143 Standard is referring to the true slump. Where the concrete remains intact and retains a symmetric shape. A zero slump and a collapsed slump are both outside of the rang of workability. Specifically ASTM C143 advises caution in interpreting test results less that ½ “ and greater than 9”. If part of the concert shears from the mass the test must be repeated with a different sample of concrete. A concrete exhibits a shear slump in a second test is not sufficiently cohesive and should be rejected.


Figure 1 ; Type of Slump

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Equipment A wheelbarrow and shovel A metric ruler A scoop A steel tamping rod, 16mm diameter and 600mm long that has at least one end

rounded. A standard slump mold. The footplates should be positioned 5mm above the base of

the cone. A mixer

Procedure The mixing pan placed on the floor and moistest it with some water. Make sure it is

damp but no free water is left. The slump cone was hold firmly in place using the 2 foot holds. One-third of the cone filled with the concert mixture. Then the layer tamps 25 times

using the steel rod in a circular motion, making sure not to stir. More concert add mixture to the tow-third mark. Tamping for 25 times repeated

again. The whole cone was fill up to the top with some excess concrete coming out of top,

then tamping repeated 25 times. Excess concrete from the opening of the slump cone was remove by using tamping

rod in a rolling motion until flat. Slowly and carefully remove the cone by lifting it vertically, making sure that the

concrete sample dose not move. Wait for the concrete mixture as it slowly slumps. After the concrete stabilizes, the slump-height was measures by tuning the slump

cone upside down next to the sample, placing the tamping rod on the slump cone and measuring the distance from the rod to original displaced center.

[Figure 2] shows the complete process using pictures.


Figure 2 ; Slump Procedure

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Result Finally we have shear slump, and slump value equal to (9 cm).

Discussion and conclusion After we made the test, we get shear slump of value equal to: (9 cm).

From the experiment we conducted, we can determine the workability of a sample from fresh concrete of given grade and promotion using the slump test. The slump apparatus is not suitable for concrete in which the maximum aggregates size does not exceed 40mm. it should be noted that the value of slump changes with time after mixing owing to normal hydration processes and evaporation of some of the free water and it is desirable therefore that test are preformed within a fixed period of time. It is also advisable to delay testing for around 10miniutes after the addition of water to allow for the absorption of water by aggregates

This test varies easy to use in projects and in laboratory, but it is not a true determination of workability.

This test learnt us about mixing the concrete, and the amount used especially in big projects.

This test not use in lean mix because it is not the true determination for workability but is good in site.

Appendix


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Compacting Factor Test

IntroductionThese tests were developed in the UK by Glanville (1947 ) and it is measure the degree of compaction For the standard amount of work and thus offer a direct and reasonably reliable assessment of the workability of concrete . the test require measurement of the weight of the partially and fully compacted concrete and the ratio the partially compacted weight to the fully compacted weight, which is always less than one, is known as compacted factor . For the normal range of concrete the compacting factor lies between (0.8 - 0.92) .

ObjectivesTo measure the workability of concrete.The objective of compaction factor is the measure the degree of compaction resulting from the application of standard amount of work.

TheoryThe apparatus which is commercially available, consist of a rigid frame that supports two conical hoppers vertically aligned above each other and mounted above cylinder, as shown in the figure, the top hopper is slightly larger the bottom hopper, while the cylinder is smaller in volume than both hoppers, to perform the test , the top hopper is filled with concrete but not compacted. The door on the bottom of the top hopper is opened and the concrete is allowed to drop into the lower hopper. Once all of the concrete has fallen from the top hopper, the door on the lower hopper is open to allow the concrete to fall to the bottom cylinder, a tamping rod can be sued to force especially cohesive concretes through the hoppers, the excess concrete is carefully struck off the top of the cylinder and the mass of the concrete in the cylinder is recorded, this mass is compared to the mass of fully compacted concrete in the same cylinder achieved with hand rodding or vibration. The compaction factor is defined as the ratio of the mass of the concrete compacted in the compaction factor apparatus to the mass of the fully compacted concrete. The standard test apparatus, described above is appropriate for maximum aggregate sizes of up to 20mm; a larger apparatus is available for concrete with maximum aggregate sizes of up to 40mm.

Compacting Factor=Weight of partially compacted concreteWeight of full compacted concreted

Apparatus1. A sample of freshly mixed concrete.2. A scoop 3. A wheelbarrow and shovel.4. a steel tamping rod which is 16mm diameter and 600 mm long that has at least one end

rounded 5. Compacting factor.6. Upper Hoper:

o Top internal diameter 25.4cmo Bottom internal diamere 12.7cm


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o Internal height 27.9cm7. Lower Hopper:

o Top internal diameter 22.9cmo Bottom internal diameter 12.7cmo Internal height 22.9cm

8. Cylinder:o Internal diameter 15.2cmo Internal height 30.5cm

As shown in [Figure 3]

Procedure

Keep the apparatus on the ground and apply grease on the inner surface of the cylinders.

Measure the mass as w1 kg by weighing the cylinder accurately and fix the cylinder on the base in such a way that the central points of hoppers and cylinder lie on one vertical line and cover the cylinder with a plate.

For each 5 kg of aggregate mixes are to be prepared with water-cement ratio by weight with 2.5 kg sand and 1.25 kg of cement and then add required amount of water thoroughly until and unless concrete appears to be homogeneous.


Figure 3 ; Compacting Factor Test ApparatusCh

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With the help of hand scoop without compacting fill the freshly mixed concrete in upper hopper part gently and carefully and within two minutes release the trap door so that the concrete may fall into the lower hopper such that it bring the concrete into standard compaction.

Fall the concrete to into the cylinder by bringing the concrete into standard Compaction immediately after the concrete has come to rest and open the trap door of lower hopper and then remove the excess concrete above the top of the cylinder by a pair of trowels, one in each hand will blades horizontal slide them from the opposite edges of the mold inward to the center with a sawing motion.

Clean the cylinder from all sides properly. Find the mass of partially compacted concrete thus filled in the cylinder and say it W2 kg. After this refill the cylinder with the same sample of concrete in approximately 50 mm layers, by vibrating each layer heavily so as to expel all the air and obtain full compaction of the Concrete.

Struck off level the concrete and weigh and cylinder filled with fully compacted concrete. Let the mass be W3 kg.

The top surface of fully compacted concrete is then carefully truck off level with the top of the cylinder and weighed to the nearest 10grams. This weight is known as “Weight of fully compacted concrete.

Result and Calculation

Weight of empty cylinder 3.75kg

Weight of cylinder with partially compacted concrete 13.45kg

Weight of cylinder with compacted concrete 15.55kg

Partially compact concrete 13.45-3.75=9.7kg

Fully compacted concrete 11.8kg

compacting factor=weighof partially compacted concreteweighof full compacted concreted

compacting factor= 9.7 kg11.8 kg

=0.82≤1(¿ is good workability )

DiscussionThe final value for the conducted experiment is 0.82. The higher value of the calculation the more workable the concrete. And for the normal range of concrete the compaction factor lies between (0.8 – 0.92 ) . This test is particularly useful for dryer mixes for which the slump test is not satisfactory. The sensitivity of the compaction factor is reduced outside the normal range of workability and is generally unsatisfactory for compacting factor Greater than 0.92. The test is sufficiently sensitive to enable difference in work ability arising from the initial process in the hydration of cement to be measured. Each test, there for should be carried out at a constant time


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LABORATORY 3

interval after the mixing is completed, if strictly comparable results are to be obtained, and some ranges are in bellow in table

Degree of

workability Slump( mm)

Compaction factor

applicationSmall apparatusLarger

apparatus

Very low 0-25 0.78 0.8Vibrated concrete in roads of other

large

Low 25-50 0.85 0.87

Mass concrete foundation without

vibration simple reinforced section

with vibration

Medium 50-100 0.92 0.93

Normal reinforced work without

vibration and heavily reinforced

sections with vibration.

High 100-180 0.95 0.96

Section with congested

reinforcement not normally suitable

for vibration

Advantages: The test a dynamic test and it is more appropriate then static tests for highly thixotropic

concrete mixtures

The compacting factor test give more information which is compatibility than the slump test.

Disadvantages:

The test method does not use vibration, the main compaction method used in the field.

The amount of work applied to the concrete being tested is a function of the friction

between the concrete and the hopper which may not reflect field conditions.

Although the test is commercially available it is used infrequently.

The bulky nature of the device reduces its usefulness in the field, further the test method

requires a balance to measure the mass of the concrete in the cylinder.


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ConclusionForm test we can obtain that the Compacting factor of fresh concrete is done to determine the

workability of fresh concrete by compacting factor test as per IS: 1199 – 1959. The apparatus used is

Compacting factor apparatus. And it used to determine the Workability of a concrete signifies the

full compaction of concrete using a required or reasonable amount of work which helps to achieve

the desired possible density or void of fresh concrete resulting better strength and durable concrete

structure and helpful to maintain durability throughout the job.

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Vebe Time Test

Introduction It is based on measuring the time (Called VEBE time) needed to transfer the shape of a concrete mix from a frustum cone to a cylinder (these shapes are standardized by the apparatus of this test), by vibrating and compacting the mix. The more VEBE time needed the less workable the mix is. This method is very useful for stiff mixes. The required Vebe Time Test value may be entered in the ‘Vebe time’ field on a Mix Design Form. The Vebe time test is a more scientific test for workability than the Slump Test, in that it measures the work needed to compact the concrete. The freshly mixed concrete is packed into a similar cone to that used for the slump test. The cone stands within a special container on a platform, which is vibrated at a standard rate, after the cone has been lifted off the concrete. The time taken for the concrete to be compacted is measured. Vebe times range from 1 second for runny concrete to more than 12 seconds for stiff concrete. Unlike the slump test, the Vebe time test gives useful results for stiff concretes. The levels of workability defined in the DOE Method give both Slump values and Vebe times for each level, and these values are used in First mix for converting between Slump values and Vebe times. See Method of Specifying Workability for selecting to use the Slump or Vebe tests Range: 0 - 20 seconds.

Objectives

To measure the remolding ability of concrete under vibration.

To measure indirectly the workability of concrete.

To obtain the workability of concrete suing vebe time test.

Theory

The apparatus shown that the consists of a metal cylindrical container mounted on a

vibrating table, which produces a sinusoidal vibration, in the version of the test standardized

in Europe as EN 12350-3 a slump cone is placed in the center of the cylinder and filled in the

same manner as in the vebe table is started and the time for the concrete to remold from

the slump cone shape to the shape of the outer cylindrical container is recorded as a

measure of consistency , the sliding clear plastic disk facilitates the determination of the

end of the test.


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Apparatus

VEBE consistometer.

Description:

o It consists of: Cylindrical container with diameter = 240 mm, and height =

200 mm.

o Mould: the same mould used in the slump test.

o Disc: A transparent horizontal disc attached to a rod which slides

o Vertically. Vibrating Table: 380*260 mm, supported by four rubber shock

absorbers.

Tamping rod.

Stop watch.

Container.

A tamping rod.

Vibration rod.

As shown in [Figure 4]


Figure 4 ; Vebe Time Test Apparatus

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Procedure Slump test as described earlier is performed placing slump cone inside the sheet metal

cylindrical pot of the consistometer. The glass disc attached to the swived arm is turned and place on the top of concrete in

the pot. We placed the mold concentrically in the container.

It was filled with the concrete mix on four layers with tamping 25 times each layer. The mold then is left up, and the slump value was calculated. The transparent disk was placed on the concrete cone. The vibrator was started as the timing did. The timing shall stop when the transparent disc is totally covered with Concrete and all the cavities in the mix are disappeared. The electrical vibrator is then switched on and simultaneously a stop watch started. The vibration is continued till such a time as the conical shape of the concrete

disappears and the concrete assumes cylinder shape. This can be judged by observing the glass dics gram the top from disappearance of

transparency. Immediately when the concrete fully assumes a cylindrical shape, the stop watch is

switched off.

DiscussionsThe vebe test is the best method to calculate the workability, because it consist of slump value and vebe time. this test is different of compaction factor used the manual compacted. But this test is difficult to use in the project may be we need electricity . The workability of concrete, define in vebe seconds is the vibration time in seconds. And the remolding is assumed to be complete when the glass plate rider is completely covered with concrete and all cavities in the surface of the concrete have vanish, this judged visually, and the complexity of establishing the end point of the test may be a source of error, to avoid it an automatically operated device for recording the movement of the plate against time may be fitted, and The main advantage of this test is that it is a dynamic test and can be used on concretes that are too stiff for a slump test.

Advantages: Test results are obtained directly. The test device is standardized in ASTM and identified by ACI committee 211, in its

guide for proportioning low slump concrete.


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The vebe consistometer is a dynamic test and can be used on concrete that are too dry for the slump test.

Disadvantages: No analytical treatment of the test method has been developed, such treatment would

be complex because the shear rate declines during of the test the concrete specimen changes shape.

The test device only works low slump concretes. Due to the need to ensure that all vibration is kept within the test device , the size of the

test device makes the vebe consistometer generally unsuitable for field use.

ConclusionAccording the test results we obtained, concrete mix we used can be judged as follows:

Slump test: The mix has a medium workability. Compacted factor test: The mix has medium workability. VEBE test: The mix has low workability.

This variation in the workability between the first 2 tests and the last one (VEBE test) can be a result to losing the workability with time, the time between making the mix and doing the VEBE time test was larger than it to the other two tests. Other reason for that might be an error resulted from the determination of the end of the test.

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Chapter 3

Destructive Concrete TestAfter we done with the above tests we need to start molding the concrete into the chosen moulds, such as 3 cubes of 100x100, Beam of 100x100x500 and a cylinder of ɸ150x300. And we keep them on mold for 24 hours to gain the required strength.

After 24 hours, concrete element need to be dismantle and keep in water tank for 7 days or a week.

After 7 days when concrete gain there specific strength we have to start our destructive tests, such as Compression test for cubes and cylinder samples and flexural test for the beam.


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Compressive Strength Test

Introduction A compression test is a method for determining the behavior of materials under a compressive load. Compression tests are conducted by loading the test specimen between two plates and then applying a force to the specimen by moving the crossheads together. The compression test is used to determine elastic limit, proportionality limit, yield point, yield strength and compressive Strength. Compressive Strength, It is the maximum compressive stress that a material is capable of withstanding without fracture. Brittle materials fracture during testing and have a definite Compressive strength values. The compressive strength of ductile materials is determined by Their degree of distortion during testing.

ObjectivesTo, determine the compression strength of concrete test cube and cylinder according to BS 1881.

TheoryOne of the important properties of concrete is strength in compression; the strength in compression has a definite relationship with all other properties of concrete. The compressive strength is taken as the maximum load it can be carry on per unit area; BS 1881 and MS \7.1 specify the use of concrete cube to determining compressive strength. And Structure components such as columns and struts are subjected to compressive load in applications. These components are made of high compressive strength materials. Not all the materials are strong in compression. Several materials, which are good in tension are poor in compression. Many materials poor in tension are good in compression. Cast iron is one such example. This strength is determined by conducting a compression test. During the test, the specimen is compressed and deformation Vs. the applied is recorded.

Apparatus

ADR 2000 compression machine. Three cubes size 150x150x150mm. One cylinder ø150mm x300mm

[Figure 5] is the complete machine of compressive strength machine.


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Procedure

The cubes and cylinder removed from the curing tank after 7 days. Place the plain (lower) bearing block, with its hardened face up, on the table or platen of

the testing machine directly under the spherically seated (upper) bearing block. Wipe clean the bearing faces of the upper and lower bearing blocks and of the test

specimen. Place the test specimen on the lower bearing block. Carefully align the axis of the specimen with the center of thrust of the spherically

seated block. As the spherically seated block is brought to bear on the specimen, rotate its movable

portion gently by hand so that uniform seating is obtained. The cube and cylinder was center carefully. The type of failure and appearance cracks had been noted.

Rate of Loading Apply the load continuously and without shock. Apply the load at a constant rate within the

range of 20 to 50 psi per second. During the application of the first half of the estimated maximum load, a higher rate of loading may be permitted.

Do not make any adjustment in the controls of the testing machine while the specimen is yielding rapidly immediately before failure.

Increase the load until the specimen yields or fails and record the maximum load carried by the specimen during the test.

Note the type of failure and the appearance of the concrete if other than the usual cone type fracture.


Figure 5; Compressive Strength Test Apparatus

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Result

Cylinder result after compression test

Diameter 150mm

Sample peak load 151.7kn

Sample stress 8.585

Sample pace rate 5.3kN/s

Cube result after compression test

Sample peak load 115.4kn

Sample stress 11.54 MPa

Sample pace rate 3 kN/s

Precautions

The test does not apply on concrete whose nominal maximum aggregate size exceed 40mm first check the maximum aggregate size.

Cubes wouldn’t me replaced in the testing machine centrally on platens, before the load is applied.

Close door of the machine to avoid any crushed pieces of object being to your eyes.

DiscussionFrom the compression test we took some data that shows that our specimen is enough strong, according to the time which was less than 28 days our specimen was harden and able to carry on enough load, such as the cylinder sustain 151.7kN which was before the object failed. And as the same for cube the sustain load was 115.4 kN before the object fail, if we compare the stresses due to time were also enough strong as a 8.585MPa for cylinder and 11.54MPa for cube, this test show if the test carry on at the exact time 28 day the concrete would be able to sustained big amount of the load.

If the strength of our concrete is not fulfill the requirement, so the following can be the reasons: Concrete is not well mixed together.


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Water to cement is not in the right proportion, which can make the hydrations process not complete.

Constituent materials such as cement aggregate and water which were not according to the right proportions.

Hardening time less than 28 days concrete reach maximum strength at 28 days our specimen was harden In a week.

ConclusionFrom result that we took from the testing in the laboratory we conclude that, that the concrete we tested it in compression machine, and the design and proportion of it we wouldn’t be able to apply it at the work site, because of it doesn’t have the desirable strength, it’s may can cause the structure collapse. And as we seen that the restrictive effect of the platens of the testing machine over the entire high of cylinder but leaves unpretentious a part of test cubes, since both of the object are mad form the same concrete but their strength are different, we consider here human error as well and the moisture condition of the sampling at the time of testing also establish to be affect the ratio of strength of two types of specimen.

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Flexural Test

IntroductionThe experiment involves the use of a simply supported beam test to determine the elastic constants for a material. There are various aluminum and magnesium beams which may be used in the test. Each beam has an axial and transverse oriented strain gage on the top (or bottom) surface. And Concrete pavement carries load as a simple, plain, (non-reinforced) concrete beam. The strength of the concrete in flexure is the most important requirement. In previous labs then primary interest has been the compressive strength of concrete. This strength is used in the structural design of reinforced concrete, where tension, in which concrete is very weak, is assumed to be taken entirely by the reinforcing steel. And cracking problem occur when diagonal tension arising from shearing stresses develops, but the most frequent case of cracking is due to restrained shrinkage and temperature gradients. There are three types of test for strength in tension. Direct tension test, flexure test and splitting tension test. For our laboratory work we used flexural test.

Objective to determin the flexure strengh of test beam according to BS1881. To demonstrate the use of flexure test procedures and the flexure test stress state

theory. To demonstrate the use of a strain gauge rosette oriented on the top of an end-

supported beam loaded at its middle. To experimentally determine and compare results of the modulus of elasticity and

Poisson's ratio

TheoryFlexure test is intended to find the flexure strength of concrete in tension. Flexure strength of concrete gives the tensile strength of concrete in bending. In this test a simply supported plain concrete beam is loaded at it third point. The resulting bending moment induce compressive stresses in the top and tensile stresses in the bottom of the beam

FlexuralTest= PL

b d2

p = maximum load applied to the beam L = distance between the axis of the cuter pair roller b = width of the beam at the line of fracture d = depth from the beam at the line of fracture


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Apparatus: ADL 2000 Flexure Machine Beam (150mm x 150mm x 150mm)[Figure 6] shows the apparatus for flexural test of beam.

Procedures Remove the test beam from curing tank after 28 days Wipe off any grit and remove any fins from the beam Clean and adjust the lower supporting rollers in position Place centrally the specimen in the testing machine in such a manner that the load shall

be applied Lower the loading rollers. Carefully align the axis of the bending device Apply the load and increase it gradually until the specimen fails. Record the maximum load applied Note the appearance of cracks in the concrete and any unusual features in the type of

failure.[Figure 7], shows before and after the flexural test happens.


Figure 6 ; Flexural Test Apparatus

Figure 7; Before After

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Result

Beam, reaslut after flexure test

Sample peak load 6.66Kn

Sample stress 1.999 MPa

Sample pace rate 0.200kN/s

flexuraltest= PL

bd2

flexuraltest=6.66 x (500)

100¿¿

Discussion

Flexural test for the beam has done successfully and the maximum peak load that it sustain was 6.6kN and a stress of 1.999 Mpa.

Conclusion

In conclusion we can say that we did our compressive and flexural test, to find out whether our concrete has the required strength to sustain the applied load or not. In fact we check our mix design for our batch of concrete. If our members didn’t sustain the required load per unit area, so we need to redesign our mix proportions until it fulfill the requirement. In order to have a safe structure.

Appendix


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Chapter 4

Non-Destructive testIn this test the concrete is not going to be destroyed.


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Rebound Hammer Test

IntroductionThe Schmidt hammer test (rebound hammer) is a surface hardness tester for which an empirical correlation has been established between strength and rebound number. The only known instrument to make use of the rebound principle for concrete testing is the Schmidt hammer, which weighs about 4 lb (1.8 kg) and is suitable for both laboratory and field work.

Objectives

To find the strength of concrete Measuring the compressive strength of concrete using the Schmidt hammer

TheoryThe Schmidt Hammer Test is based on the principles that the rebound of an elastic mass depends on the hardness of the surface against which the mass impinges. However, despite its apparent simplicity, the rebound hammer test involves complex problems of impact. Loaded mass has a fixed amount of energy imparted to it by extending the spring to a fixed position; this is achieved by pressing the plunger against the surface of the concrete under test. Upon release, the mass rebounds from the plunger, still in contact with the concrete surface and the distance traveled by the mass, expressed as a percentage of the initial extension of the spring, is called the rebound number.

Apparatus

Schmidt Hammer. Ruler. White Chalk.[Figure 8] shows the Rebound Hammer


Figure 8; Rebound Hammer

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Procedure

Determine the structure to be tested. In this case, a column is selected. A 300 X 300 mm area is set and lines are marked. The area is then divided into 15 equal boxes as in figure. Each box is marked with 5 points. The test is conducted.


A

B

C

D

E

1 2 3

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Result and calculation

1 2 3 Average (kg/cm2¿

A

26 31 26

27.8727 28 2828 26 3023 30 2630 28 31

Average 26.8 28.6 28.2

B

27 32 26

28.13

38 29 2028 30 2628 28 2227 28 23

Average 29.6 29.4 25.4

C

26 28 26

25.67

26 29 2824 27 2628 25 2428 26 14

Average 26.4 27 23.6

D

30 26 22

24.8

24 26 2624 25 2428 20 2526 28 18

Average 26.4 25 23

E

31 30 23

26.8725 28 1627 30 2830 26 2420 26 30

Average 26.6 28 26

strengthof concret= A+B+C+D+E5


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strengthof concret=27.87+28.13+25.67+24.8+26.875

=26.688kg /cm2

¿ , strengthof concret=27.87+28.13+25.67+24.8+26.875

=27.19N /mm2

General Discussion

Testing the compressive strength of concrete using the Schmidt hammer (Also called: rebound hammer, impact hammer and accelerometer), is considered as a nondestructive test as no destroyed specimens takes place in it. The main principle of this test is that it measures the rebound of an elastic mass when it collides with the concrete surface under the test, this rebound depends on the hardness of concrete and on the energy it absorbs from the collision. The tested concrete has to be smooth and firmly supported. The hammer is pressed against the concrete, and then the

mass inside the hammer is rebounded from the plunger and gives a reading on the scale. This reading is called Rebound Number which is the distance traveled by the mass expressed as a percentage of the initial extension of the spring. Note that the rebound number is an arbitrary measure that means different device might give different rebound numbers in the same test. The rebound number depends on energy stored in the spring and on the size of the mass, consequently each device is combined with a graph contains calibrating curves relating the rebound number with the.

And from the our testing that we done in the laboratory we obtain that the value of the concrete strength is 27.19 kN/mm2, mean the hummer has to be used as the smooth surface. And it preferably a concrete, from instance, the presence of a large piece of aggregated instantaneously underneath the plunger will result in an abnormally high rebound number. And the results may be not constant at all because the Schmidt hammer is not 90 degree through the concrete column. Moreover that, the reading, from Schmidt hammer after transfer to the graph reading may be wrong.

Conclusion

All the reading where considered in calculations as the deviation of all the points from the average is less than 7 degrees, I think that can be related to the homogeneity of the mix. The gained compressive strength is satisfactory, but errors might be occurred in placing the hammer orthogonally on the concrete surface. The more the rebound number is the more compressive strength of the concrete. And there are a few errors that had occurred during the experiment that may change the result a little bit and make that result inaccurate. And


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that might be, such as the test is not a strength test and exaggerated claims of its use as a replacement for the compression test should not be an accepted.

Appendix


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Micro Cover Meter

Introduction The standard tests of strength of concrete are made on specially prepared specimens, which perforce are not true sample of the concrete in the actual structural. The Micro Covermeter is a microprocessor controlled unit weighing only 500 g, and is used for the non-destructive checking of steel reinforcement in concrete structures and components, such as precast lintels, staircases and reinforced panels. It accurately determines the position and direction of the reinforcing bars and the exact measurement of their concrete cover to BS 1881 Part 204. It can also be used for checking mesh reinforcement and concrete pipes. The instrument is available with either a maxi prob, with a range of up to 360 mm or a mini probe for cover depths of up to 75-100 mm. Unless measuring deep cover is a particular requirement, we recommend the mini probe, as it can differentiate closely spaced bars more readily, and is less prone to interference from other reinforcing bars or adjacent steelwork.

ObjectiveElectromagnetic cover devices can be used for determining the position and direction of steel reinforcement and depth of cover to the steel.

Apparatus

Micro Cover Meter. Ruler. White Chalk.[Figure 9] shows a Micro Cover Meter set.


Figure 9; Micro Cover Meter

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Procedure

A column is selected at the in front of the lab. Micro cover meter is laid at the surface of the column. Micro meter is laid from the left to right and we get the position of the main

reinforcement. The lowest of the result from the scanner will record. After the entire surface from the right to the left is consider then the position from

bottom to the up of the column will record in the following table.

Result and calculationDirection A= C (mm) B= D (mm)

Depth of reinforcement

Bars

26 28 40 4424 34 44 4431 30 42 2320 29 50 4626 36 44 4420 32 49 4426 41 46 4420 28 42 2919 32 41 3521 28 40 4622 31 39 49

Total 255 349 477 448Total average 392.25

Depth=ΣA+ΣC2

=255+3492

=302.0mm

Depth=ΣB+ΣD2

=477+4482

=462.5mm

Depth=ΣAC+ΣDB2

=604+9252

=764.5mm

DiscussionSince it is C37 Micro covermeter Standards, BS 1881:204 ¨C DIN 1045This hand held instrument with microprocessor provides digital direct readout of steel reinforcement bars in concrete structures determining their presence, position, direction, depth and diameter. Audio and visual bar location aids. Built-in data logger with software


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that can download to computer in MS Excel format. The unit with quick scanning facility as well. And according our experiment we conducted that the depth of the reinforcement bars and the depth between A and C is 302mm while the depth of B and D is 462.5mm. during the testing of concrete should rubbed smoothly use a carborundum stone to get the exact location. And the most common encountered concrete durability problem with the concrete structure is corrosion of steel due to the ingress of deleterious external agencies from the environment.

Conciliation

According the British standard Conforms to BS.1881.204 The Micro Cover Meter is a microprocessor controlled unit weighing only 500g, used for non-destructive checking steel reinforcement in concrete structures and components such as pre-cast lintels, staircases and reinforced panels and also the BS standard 8110 no cover is below then 25mm which is the minimum requirement, overall from our report of testing we can accomplish that the result we appropriated form the main bar and the link are not dependable. Because the Micro Cover Meter accurately determines the position and direction of the reinforcing bars and the exact measurement of their concrete cover to BS1881:204. Determination of the position or direction of axis of a reinforcing bar is made by moving the search head on the surface of the structure

Appendix


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PUNDIT Plus Test

Introduction The PUNDIT plus is used to measure and determines the velocity of longitudinal waves. This determination consists of measurement of the time taken by a pulse, hence the name of the method – to travel a measure distance. The apparatus includes transducers, which are placed in contact with the concrete, a pulse generator with a frequency of between 10 and 150 Hz, an amplifier a time measuring circuit and a digital display of the time taken by the pulse of longitudinal waves between the transducers. And the ultrasonic pulse velocity is determined by the following application.

Evaluating the uniformity of concrete within a structural member

Evaluating effectiveness of cracks repairs

Estimating early age strength with correlation

Locating internal voids and cracks

Estimating depth of fire damaged concrete

Identifying anomalous regions for invasive sampling with drilled cores

Objective To determine the strength of concrete To checking crack

TheoryDetermine the strength of concrete by conduct a test using the value of the ultrasonic pulse

velocity.

Apparatus:

Pundit. Ruler. Liquid. White Chalk.[Figure 10] shows a PUNDIT apparatus.


Figure 10; PUNDIT

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Procedure

Make sure the surface of the area to be tested is smooth. Slab in lab to choose. One line is drawing on the surface of the slab (as figure below). Point are making with a distance of 10 cm on each. Transducers are first placed at point A and B. The result is from the monitor of Pundit is

taken. The other point result also been taken as a point 1 and 2. The result recorded at the following table.

Result and calculation

Point Results

Pundit Schimdt hammer

From To (m/s) (MPa)

1 2 4184 32

2 3 4056 40

3 4 5063 36

4 5 4576 38

5 6 5120 32


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Average of concrete strength using PNDIT:

Average strengthof concrete=4.4184+4.5056+5.063+4.576+5.1205

=4.6kN /s

Average strengthof concrete=37N /mm2

Average of Concrete Strength using Rebound Hammer:

Average strengthof concrete=32+40+36+38+325

=35.6N /mm2

DiscussionUltrasonic pulse velocity measurement has been found to be a valuable and reliable method of examining the interior of a body of concrete in a truly non- destructive manner. Modern equipment is robust, reasonably cheap and easy to operate, and reliable even under site conditions; however, from our experiment we determine the strength of the concrete and check whether the cracking is occurred or not, and the concrete strength we took from testing is 37N/mm2 the Schmidt hammer value we got 35.6N/mm2 it cannot be overemphasized that operators must be well trained and aware of the factors affecting the readings. It is similarly essential that results are properly evaluated and interpreted by experienced engineers who are familiar with the technique. For comparative purposes the method has few limitations, other than when two opposite faces of a member are not available. The method provides the only readily available method of determining the extent of cracking within concrete; however, the use for detection of flaws within the concrete is not reliable when the concrete is wet.

ConclusionSince the least dependable application is for strength estimation of concrete. The factors influencing regulations are so many that even under ideal conditions with a specific calibration it is unlikely that 95% confidence limits of better than ±20% can be achieved for an absolute strength. So from our result we got that no insignificant crack has occur inside the concrete structure because no low velocity record in our data while the crack has happened so the velocity of the waves is very slow.


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Appendix


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Conclusion

In conclusion we have soften and harden concrete tests.

A. Soften concrete tests are a. Slump Test, b. Vebe Time Test c. Compacting Factor Test.

B. Harden Concrete testsa. Destructive Tests

1. Compression Test 2. Flexural Test

C. Non Destructive testa. Rebound Hammer Testb. PUNTID Test c. micro cover meter

Since we are civil engineers we need to know the all above tests and we need to be update with the technology. In order to have a safe structure.

References

1. Rabitah Handan, Laboratory Sheets, 2014, Unisel, Civil Engineering Department.2. Rabitah Handan, Concrete Technology Hand Notes, 2012, Unisel, Civil Engineering

Department.3. Murari Lal Gambhir, Concrete Technology, Theory and Practice.

4. John Newman, B S Choo, Advanced Concrete Technology, Concrete Properties.5. M.S. Shetty, Concrete Technology (M.E.)


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