How to check the compressive strength of cement

How to check the compressive strength of cement

AIM:
To find the compressive strength of given sample of cement.

APPARATUS:
7.07cm cube moulds (50cm2 c/s area), compression testing machine, vibrating machine, Balance, Weights and Trays.

PROCEDURE:
Measure the given cement and standard sand in the proportion 1:3 by weight.

1. Standard sand: It shall pass the 850 micron I.S. sieve and not more than 10% by weight shall pass the 600 micron I.S. sieve. Take 200 gms of cement and 600 gms of standard sand in a pan. Mix it dry with a trowel for one minute and then add water. The quantity of water shall be (0.25 P + 3) percent of combined weight of cement and sand, where P is the % of water required to produce a paste of standard consistency determined earlier. Add water and mix it until the mixture is of uniform colour. The time of mixing shall not be less than 3 minutes and not greater than 4 minutes.

2. Immediately after mixing the mortar place the mortar in the cube mould and tamp with the help of the tamping rod. The mortar shall be rodded 20times in about 8 seconds to ensure elimination of entrained air.

3. If vibrator is used the period of vibration shall be two minutes at the specified speed of 12000 vibration per minutes.

4. Then place the cube moulds in an atmosphere of 270  2 0c and 90% relative humidity, submerge in clear fresh water till testing.

5. Take out the cubes from water just before testing. Testing should be done on their sides with out any packing. The rate of loading should be uniform and of 350kg/cm2

6. Three cubes should be tested and their average should be taken as the test result. Report the result in Kg/cm2.

OBSERVATIONS:
Compressive load at three days = Compressive load at seven days

RESULT:
Compressive strength of cement at three days
Compressive strength of cement at seven days = IS Code Specification:
For ordinary Portland cement of grade 33 the crushing strength shall not be less then 16 MPa at 3 days, 22 MPa at 7 days and 33 MPa at 28 days.
 
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