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Thursday, 4 October 2018

CEMENT


       “A cement is a binder, a substance that sets and hardens and can bind other materials together. It principal constituents for constructional purpose are compounds of Ca(calcareous) and Al + Si (argillaceous)”
       Chemical Composition of Cement        
       Lime                                   63%
Silica                                  22%
Alumina                             06%
Iron oxide                          03%

Gypsum                             01 to 04%

Portland Cement
       “An extremely finely ground product by calcinising together , at above 1500oC , an intimate and properly proportioned mixture of argillaceous (clay) and calcareous (lime) raw materials, without the addition of anything subsequent to calcination , excepting the retarder gypsum”   


Raw materials of Portland cement
       Calcareous materials, CaO [eg. Limestone ]
       Principal Constituent and its proportion can be regulated
       Excess of lime reduces the strength and makes the cement expand & disintegrate
       Lesser amount of lime also reduces the strength by quick setting
       Argillaceous materials, Al2O3 and SiO2 [eg. Clay ]
       Imparts strength
       Makes quick setting
       Excess of alumina weakens the cement
       Powdered Coal or fuel oil
       For burning

       Gypsum (CaSO4 2H2O)