Construction Cost Estimating

      

Examination of The Quality of Cement on Site

Cement is the most used in construction. It acts as a binder. It binds bundles and sand together in concrete. Though it is not very easy to check all the elements of cement, there are some primary field tests available on the site.

In the cement production process, the cement is manufactured through the chemical combination of 8 elements. The elements are extracted from limestone, clay, marl, shale, chalk, sand, bauxite, and iron ore.

Types of cement

1. Ordinary Portland Cement (OPC)
2. Portland Pozzolana Cement (PPC)
3. Rapid Hardening Cement
4. Extra Rapid Hardening Cement
5. Low Heat Cement
6. Sulfates Resisting Cement
7. Quick Setting Cement
8. Blast Furnace Slag Cement

The Testing Process:

Date of Packaging (MFG Date)

As time passes on, the strength of the cement reduces. According to the IS specification, the quality of the cement should be tested if the cement is stored for more than 3 months in the mill.

Age of cement Percentage of Cement Strength reduction
3 months 20%-30%
6 months 30%-40%
12 months 40%-50%

Colour of the Cement

The perfect color of the cement is grey with a light greenish shade. The color indicates excessive clay or lime.

The Lump

The Lump

A lump is created if there is any moisture in the cement. A reaction would show if the cement interacts with the atmospheric moisture. The reaction is called hydration. Moisture is a big no for a good quality of cement. It becomes useless if it gets hydrated from the water.

Rubbing Test

Rubbing Test

If the cement feels smooth while rubbing then it is fine. But if the cement feels rough then the cement is mixed with the sand.

Floating Test

Floating Test

If a handful of cement sinks in water and does not float after throwing it in the water then it must be of good quality.

Insert Hand

Insert Hand

If the user feels a cool feeling after inserting hand in the cement bag then the cement is still of good quality.

Shaping Test

Shaping Test

Cement is also known as hydraulic cement. At first, users have to take 100 grams of cement and make a mixture by adding some water. After that prepare a cement cake and place it on a glass plate. Next users have to sink the plate in the water. Good quality cement should be able to set and gain strength in water.

Test of Strength

Test of Strength

Users have to create a block of cement 25 mm x 25 mm and 200 mm long. Then they have to sink the block in water for 7 days. After that, they have to place the immersed block on supports 15000 mm apart and then load with a weight of 340 N. If the block is made of good quality cement then it should not show any sign of failure.

Chemical Composition Test

The requirement is based on IS 269-199.

1. The ratio of the percentage of alumina and iron oxide should not be less than 0.66.
2. Lime Saturation Factor (LSF), the ratio of the percentage of alumina, iron oxide, and silica should not be less than 0.66 and not be greater than 1.02.
3. Total loss on ignition should not be greater than 4%.
4. Total sulfur content should not be greater than 2.75%.
5. The weight of insoluble residue should not be greater than 1.50%.
6. The weight of magnesia should not be greater than 5%.

The Specific Gravity of the Cement

Specific Gravity is the ratio of a Weight of Volume of material to the same Weight of Volume of water. If the cement is stored for more than 3 months then finding particular gravity of cement is the most important thing to do. Good quality cement should have Specific gravity (Sg) in between 3.1-3.6g/cc.

The Formula

The specific gravity of cement = Weight of volume of material / Weight of volume of water

Specific gravity test /Density of Cement test

According to Le Chatelier’s Principle, the Specific gravity of cement is determined by Le Chatelier’s Flask method. And the IS code for the Specific gravity test is IS 2720- Part 3.

Procedure

1. The Le Chatelier flask must be free from moisture, meaning the flask should be dried.
2. After that users have to weigh the empty flask and note it as W1.
3. After that users have to take 50gm of cement and add it to the flask. Now they have to weigh the Flask with the stopper as W2
4. Then they have to pour kerosene in the sample up to the neck of the bottle and mix thoroughly and should check that there are no air bubbles left in the flask. Then they have to note down the weight as W3
5. Finally, they have to empty the flask and fill the bottle with kerosene up to the tip of the bottle, and record the weight as W4.

Specific gravity of cement = (W2 - W1) / (W2 - W1) - (W3 - W4) * 0.79

where the Specific gravity of Kerosene is = 0.79 g/cc.
A good cement should have a Specific gravity of 3.1-3.6 g/cc.

Examination of The Quality of Cement on Site