The
ASTM definition for Portland Cement:
A product obtained by finely
pulverizing clinker by
calcining to
incipient fusion an intimate and properly proportioned mixture of
argillaceous and
calcareous materials, with no additions subsequent to
calcination except water and
calcined or
uncalcined gypsum.
There are five types of Portland cement:
- I Normal
- II Modified (sets slower, has some sulfate resistance)
- III High Early Strength
- IV Low Heat of Hydration (sets slowly, usually used for dams or other large concrete structures)
- V High Sulfate Resistance
Type I cement is the most commonly used type of
cement for making
concrete.
Type II cement is used most often where concrete will be exposed to high levels of sulfates, such as waterways, depending on local conditions.
Type III cement is used when strength of the concrete must be developed quickly, for instance to bear the loads of further construction.
Type IV cement was developed early in the 20th century for building dams. When concrete sets, it lets off heat from the chemical reaction. This can be a problem when placing large amounts of concrete at one time. For instance, if the concrete for
Hoover Dam had been placed all at one time, it still would not have returned to ambient temperature. Type IV cement is one solution to this problem.
Type V cement is used where the concrete will be exposed to very high levels of sulfates. Kind of a beefed up version of Type II cement.