Portland Cement has been defined as the product obtained by pulverizing clinker consisting essentially of hydraulic calcium silicates, usually containing one or more forms of calcium sulfate as an interground addition.
Hydraulic calcium silicates posses the ability to harden without drying or by reaction with atmospheric carbon dioxide, thus differentiating them from other inorganic binders such as plaster of paris. The reactions involved in the hardening of cement are hydration and hydrolysis.
Five types of Portland Cements
Type I. Regular portland cement are the unusual products for general construction. there are other types of this cements, such as white, which contains less ferric oxide, oil-well cement, quick-setting cement and others for special uses.
Type II. Moderate heat of hardening and sulfate resisting portland cements use where moderate heat of hydration is required or for general concrete construction exposed to moderate sulfate action. The heat evolved from these cements should not exceed 295 and 395 J/g after 7 and 28 days, respectively.
Type III. High early strength (HES) cements are made from raw material with a limestone silica ratio higher than that of type I cement and are ground finer than Type I cements. They contain a higher proportion of tricalcium silicate (C3S) than regular portland cements. This, with the finer grinding, causes quicker hardening and a faster evolution of heat. Roads constructed from HES cements can be put into service sooner than roads constructed from regular cement.