Cement is one of the most important materials used in construction. The strength of a structure depends upon several factors, cement quality is one of them. To check the quality of cement we need to pass some easy tests which are described below.
The following are the quality tests on cement at the construction site
1- Color test.
2- Presence of lumps.
3- Temperature test.
5- Strength test.
6- Date of packing.
7- Rubbing Test.
8- Shape Test.
1- Color test
The colour of the Portland cement should be uniform at the site. The best and preferable colour of cement is Grey and the colour looks like greenish type shade. The colour of cement give us a rough estimate of the cement quality means cement has excess lime or excess clay. If anyone cement composition quantity is more according to the design the cement colour doesn’t look like perfect in greenish shade.
2- Presence of lumps
The 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.
3- Temperature test
Simply insert your hand into the cement bag, it should give cool feeling if its quality is good. Otherwise, you may feel warm because of the hydration reaction.
4- Float test
In this float test, we took a small amount of cement in our hand and throw them into small water carrying bowl. If cement float on the water the quality of the cement is not good because cement substance is more in weight and they must sink into the water. If cement sink it indicates the cement quality is good.
5- Strength test
The strength test is performed on the crushing machine. In this test we take a cement cube having a dimension 25 mm x 25 mm x 200 mm. The cube is put into the water for at latest 7 days for curing purpose and then we check the strength of the cube. The good cement must resist the load at least 340 N without failure
6- Date of packing
Strength of cement reduces with time, so it is important to check the manufacturing date of the cement. Generally, the cement should be used before 3 months from the date of manufacturing.
The percentage of strength loss of cement is given in the below table.
7- Rubbing Test
The rubbing test is another physical test which performs at the site. In this rubbing test, we take a small amount of cement in our hand and we rub it by using our fingers. If the cement gives us a smooth texture while rubbing it means cement is good (Because cement substances size is too small and cement finesse) and if cement gives us a rough texture it means cement quality id not good
8- Shape Test
In this test, we took 100 gram of the cement and we add some amount of water into the cement and make a cement plastic paste. After mating the cement past we put them into the small glass water bowl and note the cement particles while cement is sitting. If the particles are disturbed during sitting. It indicates that cement is not good because cement has the ability to attain the desired strength in water.