Types of Cements

I. Portland Cement

Akers (2001) further highlighted and explained the specification requirement of portland cement as specified by ASTM C150. ASTM C150 defines requirements for eight types of portland cement. The chemical composition of portland cement is expressed in a cement-chemistry shorthand based on four phase compounds: tricalcium silicate (Ca3S), dicalcium silicate (Ca2S), tricalcium aluminate (Ca3Al), and tetracalcium aluminum ferrite (Ca4AlFe).

The basic types of portland cement covered by ASTM C150 are as follows:

• Type I
General-purpose cement is the one commonly used for many structural purposes. Chemical requirements for this type of cement are limited to magnesia and sulfur-trioxide contents and loss on ignition, since the cement is adequately defined by its physical characteristics.

• Type II
Modified cement for use in general concrete where a moderate exposure to sulfate attack may be anticipated or where a moderate heat of hydration is required. These characteristics are attained by placing limitations on the Ca3S and Ca3Al content of the cement. Type II cement may also be specified as low-alkali cement for use where alkali reactive aggregates are present.

• Type III
This type of cement attains high early strength. In 7 days, strength of concrete made with it is practically equal to that made with Type I or Type II cement at 28 days. This high early strength is attained by finer grinding (although no minimum is placed on the fineness by specification) and by increasing the Ca3S and Ca3Al content of the cement. Type III cement, however has high heat evolution and therefore should not be used in large masses.

• Type IV
This is the low-heat cement which has been developed for mass concrete construction. The potential-phase compounds that make the largest contribution to the heat of hydration are Ca3S and Ca3Al. Therefore the amounts of these are permitted to be present are limited. Since these compounds also produce the early strength of cement, the limitation results in cement that gains strength relatively slowly.

• Type V
This type of portland cement intended for use when high sulfate resistance is required. Its resistance to sulfate attack is attained through the limitation on the Ca3Al content.

Hornbostel ( 1991), gave other types of portland cement as: White Portland cement, water proof white Portland cement, portland pozzolanic cement, portland blast furnace slag cement. Other types of cement available are aluminous cement, plastic cements, expansive cement, masonry cement, natural cement, pozzolanic cement, oxychloric (Sorel) cement and sulphur cement.