Sampling

Cement may be subjected to some quality variations. Hence sampling of cement from various parts of the bulk is to be taken. Which must be sufficiently represents the whole. A sample meant for testing shall be taken from 12 different bags, from one batch. The fine sample must be weigh at least 5 kg.

Chemical composition

1)     Ignition loss. One gram of the sample is taken and heated in a porcelain crucible for 1 hour 900C to 1000C. After heating the sample is cooled and again weighed, the percentage of loss of weight should not exceed 4%.

2)     Insoluble residue. On gram of cement is taken and 40cc of water is added and stirred. Then 10cc of HCl of specific gravity 1.18 should be added and stirred. Lumps present shall be carefully broken and is boiled for 10 minutes. The mixture now shall be filtered. Using hot water the container should be rinsed 5 times and filter should be washed 10 times. Now the residue should be washed in 30cc of hot distilled water. This is boiled for 10 minutes with 30cc of sodium carbonate solution of twice the normal strength. The solution obtained is again filtered the same filter paper. The filter paper is washed five times with water. Now it is washed with HCl solution of twice the normal strength and then with water so that it is free from chlorides. The filter paper is now dried and ignited and weighed. The insoluble residue shall not exceed 1.5%.

3)     Lime and Alumina. The ratio of percentage alumina to the percentage of iron oxide shall not be less than 0.66

4)     Magnesia. Free magnesia shall not be present at more than 5%.

5)     Sulphur. This shall not exceed 2.75%

Fineness. Sieve Test. 100gms of cement is weighed and placed on IS Sieve no.9. Any air set lumps are broken using fingers. Now gentle sieving is done for 15 minutes. The residue shall not be 10 % by weight.