Cement, is the most important material at construction site, working as binder in between fine aggregate and course aggregate. So it is always very important to check the quality of cement.
To check the physical quality of cement on site, following testing should be performed -
By viewing the packing date of cement bag we able to get the rough idea about the strength of the cement because cement reduces it's strength as time passes. Cement not stored for more than 3 months. If the cement was 3 months or more old then it should be tested first before use at site.
The colour of Portland cement should be uniform at site. The best and preferable colour of cement is grey and the colour look like greenish type shade. The colour of cement gives an indication of excess lime or clay and the degree of burning.
Rubbing test is another physical test which performs at site. In this rubbing test take a small quantity of cement in hand and rub it by using fingers. If the cement gives us a smooth texture while rubbing it means the quality of the cement is good (because cement substances size is too small and cement finesse) and if cement gives us rough texture it means cement quality is not good.
d. Hand Insertion:
Plunge your hand into the cement bag and if it gives cool feeling it indicates that no hydration reaction is taking place in the bag.
e. Floating test on Cement:
In the Float testing take a small amount of cement in hand and throw then into a small water carrying bowl. If the cement float on the water the quality of the cement is not good because cement particles are more in weight and they must sink into the water. If cement sinks the quality of the cement is good.
f. Shape Test:
In this test take a 100 gram of cement and add some amount of water into the cement and make a stiff paste. Prepare cake with sharp edge and put on the glass plate. Immerse this plate into a small glass water bowl and observe the shape should not get disturbed while settling. If the shape disturbed during the night settling, it indicate that the cement is not good, because cement has an ability to attain the desired strength. In water.
g. Presence of Lumps:
To perform, open the bag and check lumps should not be present in the bag. It ensure that no setting of the cement taken place inside the bag.
h. Smell Test:
To perform this test take small quantity of cement and smell it, if the cement contains too much of pounded clay and silt as an adulterant, the paste will give an earthly smell.
i. Cement Strength Test:
The strength test of cement is performed on the crushing machine. In this testing a cement cube of 25mm x 25mm x 200mm is casted and the cube is placed into water for at least 7 days for curing purpose and then checks the strength of the cement cube. A good cement must able to resist the load of at least 340 N without failure.