Test: Cement, Mortar & Lime - 2

Following four field tests may be carried out to ascertain roughly the quality of cement:

(i) colour: Colour of cement should be uniform and greenish grey.
(ii) Physical Properties:

∙ Cement should feel smooth when touched or rubbed in between fingers. If it is felt rough, it indicates adulteration with sand.

∙ If hand is inserted in a bag or heap of cement, it should feel cool and not warm

∙ If a small quantity of cement is thrown in a bucket of water, it should float for some time before they sink.

∙ A thin paste of cement with water should feel sticky between the fingers.

∙ If the cement contains too much pounded clay and silt as an adulterant, the paste will give an earthy smell.

(iii) Presence of lumps: Cement should be free from any hard lumps. Such lumps are formed by the absorption of moisture from the atmosphere. Any bag of cement containing such lumps should be rejected.

A Portland cement with low C₃A and C₄A Fcontents is very effective against sulphate attack, such cement is called sulphate resisting cement. The use of sulphate resisting cement is recommended for concretes to be used in marine environment foundations in chemically aggressive soils.

If expansion is more than 10 mm, cement is said to be unsound.
In autoclave expansion should not be more than 0.8%

The initial setting time for OPC should not be less than 30 minutes. The final salting time should not be greater than 10 hours.