Defferent Type of Cement || Type of Cement || types of cement and their uses

Defferent Type of Cement

-TYPES OF CEMENT-

(Different Types of Cements, Situations of their Use and Precautions)

The cement used in general construction works is called ordinary cortland cement. The common person understands the meaning of cement as Portland cement and his understanding is also correct from one point of view because in most of the works = more than 95%) this cement is used.

 But certain types of construction work may have their own special requirements, which this cement is often able to meet. Keeping these special requirements in mind, some special types of mants are manufactured. Due to their limited use, their production is also very economical and they are also relatively expensive. Following are the different types of cement

1. Ordinary portiand cement, O.P.C.)

2. Rapid hardening cement)

3. Low heat cement)

4. High alumina cement)

5. Blast furnace slag cement)

6. Quick setting cement)

7. White and coloured cement)

8. Pozzolana cement)

9.  Sulphate resisting cement )

10. Expanding cement)

11. Hydrophobic or water repelling cement)

12. Oil well cement)

13. Natural Cement)

A brief description of the above varieties of cement is given below

1. Ordinary Portiand Cement (O.P.C.)

    This cement is the most commonly used. Only “cement” refers to this cement. This cement is used for all types of general work. Other types of cement are special cements, and they are used only under special circumstances while ordinary Portland cement Portland cement is not to be used in works such as heavy concrete structures (dams etc.), presence of sulfates in soil or water, presence of chemicals and acids, works of urgent or emergency nature.

            A special precaution in its use is that it should be used before the initial setting in the cement and it should be properly leveled.

            Nowadays Portland cement is being manufactured in different grades like 33 grade, 43 MPa and 53 MPa. Grade refers to the strength of concrete. The higher the grade, the higher the strength of the concrete. Cement of 33 grade, 43 MPa and 53 MPa has peak compressive strength of 33N/m2, 43 N/mm2, 53N/mm2 respectively. The strength of 33 grade cement is 33 N/mm2 on 28 days. The peak strength of 43 MPa and 53 MPa cement is 43N/mm2 and 53N/mm2 respectively but there is no fixed time after how many days this strength will be achieved. More heat is released in the deposition of 53 MPa cement in which it is more prone to cracking. Therefore, use of 53 MPa cement is not desirable in normal works.

2. Pozzolana Cement

            This cement is prepared by adding 10% to 25% pozzolana substance to ordinary cement. Special types of soil, ash emanating from volcanoes, ash emanating from thermal power stations and succulents etc. are Pozzolana substances. The use of ash from thermal power stations not only reduces the cost of cement but also solves the problem of ash disposal. Pozzolana is a silicate or a material containing silica and alumina. 

It does not have bonding properties of its own, but in the fine state at normal temperature, it reacts with calcium hydroxide (lime) to form compounds that have bonding properties. Some amount of lime is in the free state when the Portland Soment freezes. Pozzolana substances react with this free lime to form a strong bonding compound. Pozzolana is grinded and mixed with cement. In addition, these substances can also be added before the clicker grinding.

            Pozzolana cement has good ductility and the workability of concrete and concrete made from this cement is also good. Leaching can occur in water structures such as dams, bridges, woes, etc., due to the free lime present in ordinary Portland cement. Pozzolana cement does not contain free lime, so water structures made from it have high water permeability. But when the amount of pozzolana substances is high, the compaction of concrete and concrete is more and its strength also decreases.

            The calcined* (calcined) rock at Bhakra dam was used as pozzolana. Raw rock stone was available at a distance of 3 km from the dam site. It is mixed with cement from 15% to 20%.

3. Rapid Hardening or Early Strength Cement

            As the name suggests, this cement hardens faster than ordinary cement. This cement is very suitable for works of urgent and emergency nature such as construction of roads and bridges during times of war or repair of bridges and important buildings etc. This cement is more finely ground than ordinary cement, due to which the process of hydration is quick. In its solidification, heat reactants are released, due to which this cement is not suitable for heavy works. The heat in its hydration makes this cement suitable for concreting in cold regions.

Precautions - The content of lime in the raw materials of this cement is high, due to which there is a possibility of the presence of free lime in the cement. In addition, tricalcium silicate also contains free lime whose presence is objectionable. To neutralize their effect, a little sugar is added to the cement.

4. Low Heat Cement

            The process of hydration of the somate (the process of hardening) releases a lot of heat and causes contraction. In heavy work, there is a great difference in the temperature of the inner and outer surfaces because due to the outer side being open in the atmosphere, they get dissipated quickly while the inner side remains there for a long time. This leads to unequal expansion in both the surfaces which leads to cracks in the structure. When ordinary cement is used in heavy concrete works, an expensive cooling arrangement is required to keep the interior under control of the heat. To avoid this, low rise cement is used in heavy concrete works. As the name suggests, very little heat is released in the hydration of this cement.

In this cement, the amount of tri-calcium silicate, whose hydration is rapid, is low and the amount of di-calcium silicate, whose rate of hydration is slow, is high. In this way the rate of deposition of low age cement remains very slow and controlled. It also has a low tri-calcium aluminate content because its hydration releases more heat.

5. High Alumina Cement

            As the name suggests, the raw material of this cement contains high amounts of alumina, due to which the amount of tri-calcium aluminate CA in this cement is very high, ranging from 35% to 55% (only 10% in ordinary cement). Hydration of aluminate occurs first in the process of cementing. Therefore it acquires potency very quickly. As much strength as ordinary cement attains in 7 days, this cement attains that strength in 1 day.

Due to the more rapid hydration process, heat is also released in the deposition of cement which is not desired at normal temperature. In fact, in cement (1), the rate of hydration, (2) the development of strength over time, (3) the rate of oozing in the deposition and (4) the dispersion of humus in the valley, etc., should be balanced in such a way that the cement has Do not compress or else cracks will occur in it.

 But due to the presence of tri-calcium aluminate, the rate of hydration of high alumina cement is more rapid. And the volume change of aluminate is also high, due to which the chances of cracks in the structure are high due to the use of this cement. This cement is prepared by calcining a mixture of bauxite (it has high alumina content) and limestone. These are finely ground in a tube mill.

6. Blast Furnace Slag Cement

           In the production of pig iron, a large amount of slag is released from the furnace. The slag released from the furnace has cementing properties. Generally, in making 1 ton of cast iron, only 1 ton of slag is produced. This slag is considered a waste material but it contains all the basic elements of cement such as silica, alumina and lime. Their ratio depends on whether the slag is acidic or alkaline. As soon as the slag comes out of the furnace, water is sprayed on it and cooled.

 By doing this the slag breaks down and turns into a granulated form. Let it dry. Now it is grinded by mixing it in a certain proportion with a clicker. It is mixed in the ratio of 35% to 65%. The general characteristics and properties of this cement are similar to that of ordinary cement. It can be used in all those works for which ordinary cement is suitable.

The use of slag makes this cement cheaper, and the problem of disposal of slag is also solved. Along with this, the discharge of Amma from this cement is less, due to which it can also be used in heavy works like dam, retaining wall etc.

7. Quick Setting Cement

            When any construction or repair work has to be done in running or standing water, then it is necessary that the cement should settle as soon as possible so that the cement gets minimum time to dissolve in the water. Quick setting cement is very suitable for such situation. The special feature of this cement is that it solidifies quickly. The initial setting time of this cement is less than 5 minutes and the final setting time is less than 30 minutes. Due to the rapid settling of cement, the amount of cement which is destroyed by dissolving in water is greatly reduced.

The settling time of cement depends on the amount of gypsum (CaSOa). If gypsum is not added to cement, it sets quicfkly, so gypsum is not added to this cement at the time of clicker grinding, due to which the property o quick setting comes in it.

            Due to the initial setting time of this cement being less than 5 minutes, it has to be done very quickly in making and using this cement or concrete. For this reason, this cement is not used in works of general nature.

8. White and Coloured Cement

            The grayish color of ordinary cement is due to the presence of iron oxide in the raw materials. Raw materials that are free from iron, such as chalk and white clay, are used to make white cement. Cement of desired color can be prepared by mixing suitable pigment in white cement. Mineral pigments are used as color pigments. The amount of coloring pigment ranges from 5% to 10%. Mineral oxides are very expensive as coloring pigments. The color pigments used for some of the main colors are as follows-

Yellow, brown and red = iron oxide

green = commium oxide

blue = cobalt

black and brown = manganese dioxide

           White cement has all the other properties similar to ordinary cement except color. White and colored cements are very expensive and are used only for decorative purposes. The raw material of white cement is expensive, hence it is very expensive. It is about 3 times more expensive than ordinary Portland cement. It is available in the market in packing of 50 kg, 5 kg and 1 kg.

9. Sulphate Resisting Cement

Tri-calcium aluminate (3 CaO.Al2O3), a component of cement, reacts with sodium and magnesium sulfate to form calcium sulfo aluminate. In this process, there is a change in the volume of cement mortar and concrete, due to which cracks occur in the structure. Therefore, ordinary cement should not be used in such places where there is a possibility of the presence of sulphates, otherwise cracks occur in the structure. Sulfate salts can be present in water or soil

Anti-sulphate cement is very suitable for such situations. The proportion of tri-calcium silicate and di-calcium silicate components in this cement is high, whereas tri-calcium aluminate has a very low concentration as this compound reacts with sulphates. This cement is used in the construction of structures in sea water, alkaline soils and other conditions where sodium and magnesium sulfate are in large quantities.

10. Expanding Cement

          In ordinary cement, contraction occurs at the time of deposition, causing contraction cracks in the structure. Some expanders like sulfo aluminates are used in cement to prevent shrinkage. Diffusion can be controlled by making suitable changes in the diffusible substances and their quantity. This cement is very suitable for work like crack repair. After filling in the crack, it expands slightly, due to which the crack is properly sealed. This cement is not produced, but when required, expansive elements are added to the ordinary cement itself.

11. Hydrophobic or Water Repelling Cement

            It is a special type of cement whose main feature is repulsion against water. Due to this, this cement does not rot from moisture and it can be transported in rainy season also. While making this cement, some water repellent chemicals are added during clicker grinding. These chemicals form a mono-molecular layer around each grain of cement and thus prevent the cement from absorbing water from the atmosphere. While making concrete or masala, due to the rubbing in the mixer, the atomic layer formed around the particles gets dissolved and the action of hydration is similar to that of ordinary cement. A.C.C. The cement company manufactures this cement.

12. Oil-well Cement

           After excavation of oil wells, it is necessary to fill the gap between the wall of the well and the steel lining. The layer of porous soil also has to be grouted so that the wall of the well can be protected from collapse. The shaft of the well also needs protection from underground water. The depth of the oil-wells is high (1000 m to 5000 m) and the temperature at their bottom is very high. At this stage it is necessary that the cement solution should remain in the liquid state till it reaches the bottom. Ordinary cement solidifies very quickly at high temperatures. For such conditions, A.C.C. Cement Company has developed oil-well cement which can be used at temperatures up to 100°C.

13. Natural Cement

            It is a cementitious substance like aqueous lime, but the amount of dead matter in it is about 40%. Its natural stones are complex c
ompounds of calcium, aluminum and silicon, which on burning or calcination give a cohesive substance with high aqueous properties.

            The properties of this cement are of low grade and depend on the quality of the natural stone. This cement is cheap. Nowadays this cement is not in use because its properties are of low grade and they cannot be controlled.