Some major cement ingredients and their uses

Cement is considered as strong binding material for building construction. So, there should be proper knowledge on the composition of cement. The functionality of cement constituents plays a major role for cement composition. To attain the superior quality of cement, the amount of constituents should be modified at the time of producing cement.

Formation of Cement - The following constituents are part and parcel of cement. Given below, the common percentage of these constituents in cement:

Constituents : Percentage in cement

Lime 60-65
Silica 17-25
Alumina 3-8
Magnesia 1-3
Iron oxide 0.5-6
Calcium Sulfate 0.1-0.5
Sulfur Trioxide 1-3
Alkaline 0-1

Functions of Cement Constituents - Given below, the detail characteristics of these constituents :

Lime: Lime stands for calcium oxide or calcium hydroxide.
The existence of lime should be adequate to develop silicates and aluminates of calcium.
Inadequacy in lime minimizes the strength of property to the cement.
Inadequacy in lime leads to quick setting of cement.
Surplus in lime quantity makes cement weak.
With the existence of lime excessively, cement will be inflated and decomposed.
Silica: Silicon dioxide is called as silica, chemical formula SiO2.
There should be adequate quantity of silica in cement to dicalcium and tricalcium silicate.
Silica contributes strength to cement.

Normally, the percentage of silica is about 30 percent in cement.

1. Alumina: Alumina is Aluminium oxide. The chemical formula is Al2O3.
a. Alumina contributes rapid setting property to the cement.
b. Clinkering temperature is reduced with the existence of the necessary quantity of alumina.
c. Excess alumina makes the cement weak.

2. Magnesia: Magnesium Oxide. Chemical formula is MgO.
a. Existence of Magnesia should not be in excess of 2% in cement.
b. The strength of the cement will be decreased significantly with excessive magnesia.

3. Iron oxide: Chemical formula is Fe2O2.
a. Iron oxide assigns color to cement.
b. It functions as a flux.
c. At a very high temperature, it imparts into the chemical reaction with calcium and aluminum to develop tricalcium alumino-ferrite.
d. Tricalcium alumino-ferrite brings hardness and strength to cement.

4. Calcium Sulfate: Chemical formula is CaSO4
a. It exists in cement in the form of gypsum(CaSO4.2H2O)
b. It delays or retards the setting action of cement.

5. Sulfur Trioxide: Chemical formula is SO3
a. It should not exist in excess of 2%.
b. Excess Sulfur Trioxide makes cement to become weak.

6. Alkaline:
a. It should not exist in excess of 1%.
b. Excess Alkaline matter leads to efflorescence.



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Published By
Rajib Dey
www.constructioncost.co
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Brief explanation of Cement Hydration Process

This construction video tutorial provides useful information for the students who will appear in SSC and JE exam. The video is presented by the renowned civil engineer Mr. Parag Pal and it sheds light on cement hydration process. Mr. Pal briefly explains the term rate of heat liberation throughout pouring of concrete.

Before delve into the video, first learn the definition of hydration :-

When series of unchangeable exothermic chemical reactions occur among cement and water, it is defined as hydration.

With existence of water, the silicates and aluminates develop the products of hydration which in due course form a rigid (solid) and hard mass i.e. the hydrated cement paste.

Production of hydration products ultimately results in stiffening (loss of adaptability), setting (consolidation), hardening (strength gain).

Hydration process is ceaseless still the heat and moisture exist in the cement.

To gather sufficient knowledge on the fundamentals of hydration is very important for the following reason :-

Assure the strength and longevity of concrete.

Identify and alleviate the stresses to resist cracking.

Recognize the significance of superior curing and construction practices.

Go through the following video tutorial to learn the detail hydration process.

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Published By

Rajib Dey

www.constructioncost.co

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Some handy tips to examine the quality of cement in the construction site

Cement is considered as the most vital component in any construction. The cement plays the role of a binder that unites aggregate and sand jointly in concrete.

Though it is difficult to examine all the properties of cement, but there are some elementary field tests which provide a rough idea about the quality of cement.

Given below, the detailed lists of simple tests which can be easily accomplished devoid any equipment to determine the cement quality. These elementary tests involve examining the properties of cement upon which the strength and quality of Cement depend.

1. Date of Packing (MFG Date): It is found that the strength of the cement decreases as time passes. According to IS Specifications, cement should be reexamined if it is preserved in excess of three months in the mill.

The percentage of strength loss for various time gapping is provided below.

From the above mentioned table, it is found that the strength of cement is reduced over a period of time.

2. Colour of Cement: The color of cement should have been consistent. Grey containing a light greenish shade is considered as a standard color of cement. The quantity of surplus clay or line is determined with cement color.

3. Check for lumps: If moisture exists in cement, lumps may develop. Cement endures a chemical reaction if it gets in touch with the atmospheric moisture and it is called as hydration. Moisture is very harmful for cement. Cement becomes ineffective as soon as it is hydrated with water (liquid form or vapour form)

4. Rubbing Test: Choose a bit of cement rub within your fingers, if it remains smooth at the time of rubbing, the quality of cement is good. But if it is rough, it signifies that cement is blended with sand.

5. Float test of cement: Choose a bit of cement and put it in water, a good quality of Cement should be submerged and should not float on water.

6. Hand insertion: Put your hand into the cement bag. It you get cool feeling, then there is no hydration reaction in cement bag.

For more information, go through the following link civilread.com




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Published By
Rajib Dey
www.constructioncost.co
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