CEMENT

The terms cement and concrete are not synonymous. Concrete is artificial stone made from a carefully controlled mixture of cement, water, and fine and coarse aggregate (usually sand and coarse rock).

Portland cement is the product obtained by pulverizing clinker consisting essentially of calcium silicate, usually containing one or more forms of calcium sulfate, and there are five types of portland cement:

Type I. Regular portland cements are the usual products for general construction.

Type II. Moderate-heat-of-hardening and sulfate-resisting portland cements are for use where moderate heat of hydration is required or for general concrete construction exposed to moderate sulfate action.

Type III. High-early-strength (HES) cements are made from raw materials with a lime-to-silica ratio higher than that of Type I cement and are ground finer than Type I cements. They contain a higher proportion of calcium silicate than regular portland cements.

Type IV. Low-heat portland cements contain a lower percentage of calcium silicate and calcium aluminate, thus lowering the heat evolution.

Type V. Sulfate-resisting portland cements are those that, by their composition or processing, resist sulfates better than the other four types. Type V is used when high sulfate resistance is required.

Two types of materials are necessary for the production of portland cement: one rich in calcium (calcareous), such as limestone or chalk, and one rich in silica (argillaceous) such as clay. These raw materials are finely ground, mixed, and heated (burned) in a rotary kiln to...