Testing Concrete or test of concrete
The concrete at the time of preparation is very weak . this strength increase with the passage of time . Various factors affect the strength of these material . these include the ration of the ingredient s of the concrete quality of the component temperature of the environment and the curing after the placing of concrete. Any change in these factors affect very much the strength of the concrete .Therefore,due attention needs to be paid from selection of its elements to very stage for 28 days after its preparation.By not doing so the decrease in the strength of the concrete is possible .The concrete is tested at any stage t o estimate its strength.If the concrete is not found up to the marks then the stages are revised to get the required standard. The result of the tests are not valid if proper attention is not given to the .And the work done by the concrete will not be satisfactory.Therefore, care should be taken in collection thee sample of concrete and testing it for this purpose the environment of the laboratory should bear similarly with that of he field. To test a concrete the cube or cylinder test is performed to find its compressive strength and sp\lit cylinder test is done to find its Tensile Strength .The extramural strength is also tested through the test. the slump of the concrete is also found out to find the standard of consistency of the concrete before these tests.For this purpose slump cone test,compaction factor test or Vee-Bee test are performed .In addition to this tests are also performed after the completion of concrete work .These tests do not deform the structure and these tests tell about the strength of the concrete.The test performed without deformation the structure is known as the Non-Destructive Test.Mostly performed these non destructive tests are Rebound Hammer test penetrating resistance test break off test and ultrasonic pulse velocity test.
Different type of Testing Concrete or test of concrete
Tests are performed to find out the quality and the strength of concrete . The tests generally used are the following :
- Slump Test for Workability / Consistency
- Compaction Factor Test For Workability/Consistency
- Vee-Bee Test for Workability/Consistency
- Cube Test for Compressive Strength
- Split Cylinder Test for Tensile Strength.
- Modulus of Ruputer test
- Non-Destructive Test.
Tensile Test
Concrete is weak in tension. That is why generally the tension of concrete is neglected in a design.in RCC steel is used withstand tension .Even thin it is necessary to fine out tensile strength of the concrete.Because this is the only force they saves a construction from shrinkage and other such forces .In addition to R.C.C ,the tensil strength cannot be neglected in plain concrete .As for example this fores is important even in construction of dams ,highways and runways.In such construction ther is no need of direct tensile strength but instead Flexural strength is needed .this is called then indirect Tensile Strength .
TO FIND THIS STRENGTH OF CONCRETE , FOLLOWING Testing Concrete or test of concrete ARE PERFORMED :
- Spilt Cylinder Test
- Modulus of Rupture Test
- Spilt Cylinder Test
In this tests, the strips of plywood are placed above and below the cylinder .These are 25 mm(1 inch) wide and 3 mm (1/8'') thick.Instead of these the strips of Hard Board can also be used .In this case these are 15 mm( 5/8 inch) wide and 4 (3/16'') thick .
The specimen is placed in the compression testing machine .And a compressive force is applied.This force is to be increased gradually.In this way the cylinder breaks into two parts along the length .This is due to this compression is found by the following formula
Horizontal Tensile Strength =2P / 3.14 DL
where
P = Compressive load on the cylinder
L = Length of cylinder
D = Diameter of cylinder .
The stress obtained in this way is compared to the required stress .About 6 cylinder are tested at a tie .The their average value is calculated which is then considered as the actual strength of the concrete.Split Cylinder Test is easy.The results obtained in this test are reliable .The value of stress obtained in this test is in excess by 5 to 12% of direct tensile test which is considered as 10%.
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