It is an ordinary Portland Cement having pure white colour . it is very costly cement since lot of precautions have to be taken in its manufacture . It is use for terrazzo flooring , face plasters , traffic curbs , aerodrome markings and other ornamental works .Snow crete , silvi -crete , Atlas etc . are the patented forms of white cement . Strength of this cement is slightly less than that of ordinary cement but it is 4 to 5 times costlier than ordinary cement .
Grey colour of the cement is due to the presence of iron oxide . In the manufacture of white Portland cement , iron oxide is limited to less than 1 percent . Also superior raw materials such as china clay and pure lime stone are choosen in its manufacture . For clinkering or klining process , oil is used in place of powdered coal to avoid adulteration by coal ash . In the absence of iron oxide sodium aluminium fluoride ( cryolite ) is added to act as a fluxing agent .
Coloured cement are produced by adding suitable minerals pigments to ordinary , or white cements . Oigments 5 to 10 percent , free from soluble slats are added to the cement during grinding . Following pigments are commonly used :
Red , Yellow , Brown , Black - iron oxide
Black , Brown - manganese dioxide
Green - Chromium dioxide
Blue - cobalt blue , ultra -marine blue
Black - carbon pigments .
Colourd cement are sold in the market under the patented names of colour-crete , rain bow ' , 'snow em' etc . They are mostly used for giving decorative finishes to buildings , swimmings pools floors , fountains etc .
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