Thursday, July 13, 2006
A test of strength on concrete
The concrete is made in the field under various conditions and hence testing its adequacy is vital. The property should be tested when concrete is fresh as well as hardened.
Testing in fresh state
The most common test for ascertaining the property of fresh concrete is the slump cone test to determine its workability and cohesiveness. A sample of about 20 kg of mixed concrete is taken and the slump cone mould is filled in four layers of approximately 75mm. Each layer is filled by taming 25 times using the tamping tool. The excess concrete on top is struck off. The cone mould is lifted and placed inverted by the side of the slumping fresh concrete and the difference
in level is measured. By the very nature of the fresh cone the quality of the fresh concrete is identified. A collapsing slump or a shear slump indicates that corrective measures are to be taken.
Tests on hardened state
The test on hardened concrete is conducted for ascertaining the compressive strength. The cubes should be cast on the project site under standard conditions and tested later after the elapse of specified number of days. The period allowed are usually 7 and 28 days. A sample test result consists of at least 3 specimens and the frequency of sampling should be at least 1 sample for 5 m3 of concrete. The variation of test result should not be more than 15 per cent of average. If more, the test results of the sample are to be treated as invalid.
Testing in fresh state
The most common test for ascertaining the property of fresh concrete is the slump cone test to determine its workability and cohesiveness. A sample of about 20 kg of mixed concrete is taken and the slump cone mould is filled in four layers of approximately 75mm. Each layer is filled by taming 25 times using the tamping tool. The excess concrete on top is struck off. The cone mould is lifted and placed inverted by the side of the slumping fresh concrete and the difference
in level is measured. By the very nature of the fresh cone the quality of the fresh concrete is identified. A collapsing slump or a shear slump indicates that corrective measures are to be taken.
Tests on hardened state
The test on hardened concrete is conducted for ascertaining the compressive strength. The cubes should be cast on the project site under standard conditions and tested later after the elapse of specified number of days. The period allowed are usually 7 and 28 days. A sample test result consists of at least 3 specimens and the frequency of sampling should be at least 1 sample for 5 m3 of concrete. The variation of test result should not be more than 15 per cent of average. If more, the test results of the sample are to be treated as invalid.
# posted by mashup @ 12:20 AM 
