Field Tests to Check Quality of Cement

 

Every structure comprises of hundreds of building materials like sand, cement, aggregates, bricks, tiles, marble, etc. For creating a quality structure, building material quality plays an important role and needs to be checked frequently at different stages of construction. Cement is the most significant material used in construction and is responsible for the overall strength of the structure. Cement quality has to be ensured strictly for ensuring quality in construction.

WHY TESTING OF CEMENT IS IMPORTANT?

Cement plants are mainly located near limestone mines in remote locations. Cement companies produce clinker from a centralised clinkerization plant. Clinkers are ground at the clinkerization plant or conveyed to strategically located grinding units for grinding followed by packing of cement bags. Cement, manufactured and packed are conveyed and distributed to designated locations via road/rail.

During transporting there are chances of moisture absorption by the cement even after ensuring the best protection. The cement tends to harden after absorbing the moisture thereby hampering the quality. Because of these unforeseen issues, cement has to be checked for its quality before using it in works. The tests of cement are conducted in approved labs.

FIELD TESTS FOR CEMENT AT CONSTRUCTION SITE

The quality of cement can be confirmed with the help of some simple field tests. These tests do not require any sophisticated types of equipment and professional skills and get the results very quickly. By conducting these simple tests and analysing the results we will get an idea about the cement quality and can immediately decide on accepting or rejecting it. These are first look tests and quality of cement is ensured by its smoothness to touch, the colour of cement, etc.

It is necessary to check the quality of cement on site at the time of preliminary inspection. It is not possible to check all the engineering qualities of 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. These field tests are as follows:

Check the manufacturing date of cement

The cement has to be consumed within 90 days from the date of manufacturing when stored in ideal conditions. All cement bags have the manufacturing date and batch no printed on it. By confirming the manufacturing date we can have a fair idea about how old the cement is and can make a decision on using it.
Apart from this, all batches of cement bear a Manufacturers Test Certificate which can also be requested and checked to confirm the manufacturing dates.

Visual checking for Lumps

Cement can be checked for any visual lumps. The cement bag corners can also be pressed to confirm the possible presence of lumps. By this test, we can ensure the cement is hardened or not.

Rubbing

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. 

Hand Insertion

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.

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.

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.

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’.

Strength 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.

Feel test

Feel a pinch of cement between the figures. Cement has to feel smooth and not grainy. By this test, we can rule out the presence of any adulterated material like sand mixed with cement.

Heat of cement

Insert hand into an open bag of cement. The hand feels cool if the cement is of good quality and not yet started the hydration process.

Colour

Cement colour is usually greenish-grey. We can check the colour of the cement and confirm it at the site. But cement colour can vary with ingredient source and type.

Water float test

This test is done to determine the presence of impurities in cement. A hand full of cement is thrown to a bucket of water. If it is a good cement without impurities or any foreign bodies, the cement floats for a while before settling down. The presence of impurities can immediately settle the cement into the water.

Setting test

A thick paste of cement is placed on a glass piece and immerse slowly in water and kept there for 24 hours. The cement piece will retain its shape and sets without any cracks or changes in shape. This is considered as a good cement.