Commonly referred to as cement, it is widely used all over the world as one of the basic ingredients of concrete, mortar, and stucco. There are 5 basic Types of cements: Type I, II, III, IV and V. Production of Types IV and V have been limited at most plants in the US; very few plants manufacture them and thus expensive.
There are four principal constituents/phases of Portland cements and each influence the property of resulting concrete. Upon hydration – reaction with water- two of the four phases, – calcium silicates – produce strength-enhancing product – calcium silicate hydrate – and calcium hydroxide. The other two are mostly calcium aluminate and a calcium aluminate-iron bearing component.
In current usage are Types I, II and III and the choice of each depends on both the short- and long-term desired property of the resulting concrete. Environmental conditions is also important in the choice of cement. For example, Type III cement is used in applications where high early compressive strength is desired; is not suitable in areas with polluted air. Type II is used, often with supplementary materials, in applications where the concrete encounters sulfate ions or in sewerage systems.
Type III cement was used in an urgent high early compressive strength situation for a taxiway at a major airport on the Gulf of Mexico in the US. Six years later, the concrete had to be removed due to sulfate attack on the concrete. Sulfur dioxide from polluting chemical plants in the environment, high humidity and temperatures were external causes which facilitated the degradation of the placed concrete runway.
Type I cement is often referred to as general purpose cement but for use in sensitive projects it must be tested to determine the calcium aluminate content. If the latter is high the cement must not be used in structures where concrete will be in contact in sulfate environments.
The four principal phases in Portland cements are Tricalcium silicate, (C3S), Dicalcium silicate, (C2S), Tricalcium aluminate (C3A) & Tetra calcium-alumino ferrite phase (C4AF)
The final product in the production of cement, from the kiln, is called Clinker. It is ground with suitable amount of gypsum to produce Portland cement