Checking cement quality is a very very important step before used in concrete, plastering or any other purpose at construction work site.
Cement preliminary inspection is necessary to check the quality. It is not possible to verify all the engineering qualities for using cement on site but there exist some field test which gives us a rough idea of quality of cement. While on site we can perform these field tests to judge the quality of cement.
Note: All these are physical tests that you can commonly perform at the construction site to find the quality of cement. But the major test should be performed at laboratories.
Field Tests to Check Cement Quality
1. Date of Packing Cement
Like other products, you check when you buy. You should take care date of manufacture seen on the cement bag. It is important because the strength of cement reduces with age.
The cement should be uniform in colour. In general the colour of cement is grey with a light greenish shade. The colour of cement gives an indication of excess lime or clay and the degree of burning.
Take a pinch of cement between fingers and rub it. It should feel smooth while rubbing. If it is rough, that means adulteration with sand.
4. Temperature Test of Cement
Thrust your hand into the cement bag and it should give cool feeling. It indicates that no hydration reaction is taking place in the bag.
5. Float Test
Throw a small quantity of cement in a bucket of water. It should sink and should not float on the surface.
6. Smell Test
Take a pinch of cement and smell it. If the cement contains too much of pounded clay and silt as an adulterant, the paste will give an earthy smell.
7. Presence of Lumps
Open the bag and see that lumps should not be present in the bag. It will ensure that no setting has taken place.
8. Shape Test
Take 100g of cement and make a stiff paste. Prepare a cake with sharp edges and put on the glass plate. Immerse this plate in water. Observe that the shape shouldn’t get disturbed while settling. It should be able to set and attain strength. Cement is capable of setting under water also and that is why it is also called ‘Hydraulic Cement’.
9. Strength of Cement Test
A block of cement 25 mm*25 mm and 200 mm long is prepared and it is immersed for 7 days in water. It is then placed on supports 15000 mm apart and it is loaded with a weight of 340 N. the block should not show any sign of failure.