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CONCRETE TESTING

• WHY WE HAVE TO TEST CONSTRUCTION MATERIAL????

• a) To ensure the QUALITY of the materialb) To minimize the maintenance costc) To spare or reduce the involved parties in the construction from facing problem at later stage

2 TYPES OF CONCRETE TEST

• Destructive Test

• Non Destructive Test

DESTRUCTIVE TEST

• Can be done for testing :a) Compression strength concrete - Cube testb) Tensile strength of concrete - Direct Tension Test - Split-Cylinder Test - Flexural Testc) Flexural Strength

Cube Test• Concrete cube testing is a primary quality

compliance check on the specified design characteristic compressive strength of concrete mix supplied to the site.

• Concrete cube is prepared by placing 3 layer of concrete in the mould

• Each layer is compacted using rod for 35 times• Then it is cured in a tank of water for 7, 14 and

28 days.• On the 7th day, cube will be taken out for

compressive strength test.

• Cube must be oiled before placing the concrete

                      

• Cube test cured for 7, 14 , 28 days before testing for compressive strength is carried out

• Cube is placed in a compression test machine to ascertain the compressive strength

                                                                                  

Tensile Strength

• Tensile strength of concrete should be high enough to resist cracking from shrinkage and temperature changes.

• It can be measured using the following testa) Direct Tension Testb) Split-Cylinder Testc) Flexural Test

• Normally tensile strength is assessed using flexural or split-cylinder test.

• SPLIT CYLINDER TEST (ASTM 496)

1. A cylinder specimen of minimum 2-in. (50mm) dia, placed with it’s axis in a horizontal plane.

2.Then it is subjected to a uniform load along the length of the specimen.

LOADSide Elevation Of The CylinderFront Elevation

3.Logically, the load will split to 2 parts (P), so the tensile strength can be calculated as

ft = 2P / Πld l = length of the cylinderd = diameter of the cylinder

4. The type and shape of coarse aggregate particles also affect the tensile strength.

5. Split Cylinder Test to determine the tensile strength of concrete by splitting cylinders of the concrete in a compression testing machine.

• Cylinder before testing

• Split Cylinder Test

• After Split Cylinder Test

FLEXURAL TEST

1. Most common method for measuring the

tensile strength of concrete

2. A concrete beam with span length equal to 3

times the beam depth ( the length of the beam

should be at least 2 in. (50mm) larger than the

span) is subjected to 3rd point loading (ASTM

C78).

3. This produces tensile stresses at the bottom of

the beam and compressive stresses at the top.

• Since concrete is weaker in tension than compression, the specimen fails where it breaks into 2 following the formation of a nearly vertical crack called a flexural crack, near the section of maximum moment.

• From the failure load, the tensile strength called the modulus of rupture (MOR) is then calculated as follows bending stress = Mc = strength in tension

I

• Flexural Test

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