It is essential to check the quality of cement at site at the time of initial inspection. It is not possible to test all engineering properties of cement on site, but some field tests exist which give us a rough idea of cement quality. While on site we can conduct these field tests to assess the quality of cement. These field tests are as follows:
- date of packing
- hand insertion
- float test
- smell test
- presence of knots
- size test
- strength test
field test on cement
The date of manufacture should appear on the bag. This is important because the strength of cement decreases with age.
The color of the cement should be uniform. In general the color of cement is gray with a light green shade. The color of the cement indicates excess lime or clay and the degree of burning.
Take a pinch of cement between the fingers and rub it. It should feel smooth while rubbing. If it is rough, it means sand adulteration.
4. Hand Insertion
Put your hand in the cement bag and it should feel cool. This indicates that no hydration reaction is taking place in the bag.
5. Float Test
Put a small amount of cement in a bucket of water. It should sink and not float on the surface.
6. Smell Test
Take a pinch of cement and smell it. If the cement has a lot of ground clay and silt as an adulterant, the paste will give off an earthy smell.
7. Appearance of lumps
Open the bag and see that there should be no lumps in the bag. This will ensure that no setting has occurred.
8. Size Testing
Take 100 grams of cement and make a hard paste. Prepare a cake with pointed edges and place on a glass plate. Immerse this plate in water. Take care not to disturb the shape while setting. It should be able to set up and gain strength. Cement is capable of solidification even under water and that is why it is also called ‘hydraulic cement’.
9. Strength Test
A block of cement 25 mm * 25 mm and 200 mm long is prepared and immersed in water for 7 days. It is then placed on supports 15000 mm apart and is loaded with a weight of 340 N. The block should not show any signs of failure.