In this article we discuss about different types of cement. The artificial cement is obtained by burning at a very high temperature a mixture of calcareous and argillaceous the mixture of calcareous ingredients should be intimate and they should being correct proportion the cal se night product is known as clinker a small quantity of gypsum that is caso4 is added to the clinker and it is then pulverized into very fine particle which is known as cement. there are different types of cement we discuss in next paragraph.
1).RAPID HARDENING CEMENT
RAPID HARDENING CEMENT DEVELOP STRENGTH MORE RAPIDLY THAN STANDARD CLUB IN THIS CEMENT ALL THE AGE OF ONE DAY AND THREE DAY IS NEARLY EQUAL TO THE STRENGTH GAIN BY ORDINARY PORTLAND CEMENT AT THREE DAYS AND SEVEN DAYS RESPECTIVELY THE COMPOSITION OF THE SEMEN CONTAIN HIRE C3S THAT IS 50% AND LOWER SEAT TO AS THAT IS 21% AS COMPARED TO OFFICER CEMENT HAVING C3S 40% AND C2S 30%.
2). LOW HEAT CEMENT
Low heat cement has its chemical constituents proportional in such a way that the heat liberated due to the hydration is constantly reduced it is achieved by reducing the contents of c3s and c3a and increasing the content of c2s the specific surface of low heat cement must not be less than OPC. the next different types of cement is discussed in next paragraph.
3). POZZOLANA PORTLAND CEMENT
The pozzolana is a volcanic cement there is some believe suraikai which is prepared by burning bricks made from ordinary soil was pozzolana is a natural or artificial material containing silica and alumina in reactive form it evolves less heat during setting. The next different types of cement is discussed in next paragraph.
4). SULPHATE RESISTING CEMENT
sulphate resisting Portland cement is a type of Portland cement in which the quantity of tricalcium aluminate is less than 5% it can be used for the purpose of where abba Portland pozzolana cement slag cement or ordinary Portland cement are used the use of sulphur resisting Portland cement is particularly beneficial in such condition where the concrete exposed to the risks of damage due to sulphate attack. The next different types of cement is discussed in next paragraph.
5). WHITE CEMENT
the process of manufacturing white cement nearly the same but the amount of iron oxide and magnesium magnesium oxide which is responsible to grey colour is limited to the less than 1% the suitable raw material are chalk and high purity lam stones having 90% of calcium carbonate and less than 0.1 % of iron oxide contain and white clay white cement is very costly and only use for only decorative purpose. The next different types of cement is discussed in next paragraph.
6). BLAST FURNACE SLAG CEMENT
For this cement the slag as obtained from blast and blast furnace is used does leg is a waste product of in the manufacture of pig iron about 300 kg of slag being produced for Eastern of pig iron chemically is lead is a mixture of lime silica and alumina all slides are not suitable for manufacture of blast furnace slag cement only classic granulated slag can be used for the manufacture of blast furnace slag cement by sudden and immediate chilling of molten slag with jet of water at high pressure.
PROPERTIES OF CEMENT
The properties of cement-
1)Appreance-the cement should feel smooth when touch in between the finger if it is filled rough it indicates adulteration with sand if hand inserted in a bag or a heap of cement it should feel cool and not warm if a small quantity of cement is thrown in a bucket of water it should be sink and should not flow on the surface of earth in pest of cement with water should feel sticky between the fingers.
2)fineness-fineness of cement is measure of the size of the particle of cement the fineness of cement has a important bearing on the rate of hydrogen and hands on the rate of strength and also on the rate of gain of strength and also on the rate of evolution of heat the final the cement the higher is the rate of hydration, as more surface area is available for chemical reaction increase in the fineness of cement also found to increase the drying shrinkage of cement fineness of cement is tested either by saving or by air permeability apparatus.
3) consistency-the standard consistency of a cement based is defined has that consistency which will permit the Wicked plunger to penetrate to the point 5 to 7 mm from the bottom of the Wicked mould the purpose of this test is to determine the percentage of water is required for preparing cement paste for other test.
4)Setting time-cement when mixed with water form paste with gradually became list plastic and finally hardness is obtained in this process of setting asters is raised when the cement paste is rigid the time to reach this state is known as setting time this time is count from the instant when water is added on cement.
5)compressive strength-it is one of the important properties of cement in this test to determine the compressive strength of cement the average compressive strength of at at least three motor cube each area of the face 50 cm²,it is single most test which determine the quality of cement.
6)soundness-the purpose of this test is to detect the presence of reline and magnesia in the cement the free lime hydrate very slowly because it is covered by the thin film of cement which prevent direct contact between lime and water.
7) specific gravity-it is defined as the ratio of unit weight of solid to the unit weight of water the specific gravity of ordinary Portland cement is generally about 3.15.