Compressive strength test of concrete -step by step procedure as per Indian standard code

Apparatus

compressive testing machine should be reliable, of sufficient capacity and able to apply the load at approx 140 kg/ sqcm per minute. The permitted error should be limited to maximum +/- 2 % of maximum load.

Age at test

compressive strength testing shall be done at definite age the most common being 7,15 and 28 days. In case of urgency to calculate strength, the test may be done after 24 hours (+ / – 1/2 hours) and 72 hours ( + / – 2 hours). It is to be noted that the age of specimen is calculated from the time of adding water to concrete ingredient.

Number of Specimens — At least three specimens, preferably from different batches, shall be made for testing for each selected age.

Procedure for determining compressive strength test of concrete

1. Test specimen shall be immediately removed and tested while it is in wet condition. Excess water shall be wiped off. If test specimen is received in dry condition from outside, it shall be immerse in water for 24 hours before testing. The dimension with accuracy nearest to 0.2 mm and weight shall be noted.
2. Wipe clean both the bearing plates of machine and place the test specimen at the center such a manner that load shall be applied to the face opposite to top face while casting of test specimen.
3. The load shall be applied gradually at a rate of approximately 140 kg/sqcm per minute. When test specimen fails, maximum load applied shall be noted.
4. Calculate compressive strength of concert as per following
   compressive strength = load applied / cross sectional area
5. Average of three samples are taken as compressive strength for particular batch If variation with individual test result with average strength is more than 15 %, the whole test shall be repeated.
6. Compressive test report shall be prepared which shall include following data:

   a) identification mark
   b) date of test
   c) age of specimen
   d) curing conditions, including date of manufacture of specimen in the field
   e) weight of specimen
   f) dimensions of specimen
   g) cross-sectional area
   h) maximum load
   j) compressive strength
   k) appearance of fractured faces of concrete and type of fracture, if these are unusual.

Category: Plain and reinforced concrete Tags: compressive strength of concrete, compressive strength test, compressive strength test of concrete, compressive strength test of concrete cubes, compressive strength test of concrete procedure, concrete compressive strength test

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