Calcium Aluminate Cements

Calcium aluminate cements are used in special applications for early strength gain (design strength in one day); resistance to high temperatures; and resistance to sulphates, weak acids, and seawater. Portland cement and calcium aluminate cement combinations have been used to make rapid-setting concretes and mortars. Typical applications for calcium aluminate cements and concrete include industrial floors that are chemically resistant, heat resistant and corrosion resistant; as well as refractory castables and repair applications. The hydrates in calcium aluminate cements are responsible for the rapid hardening and early strength gain change over time, resulting in a loss of strength. The conversion process always occurs. With time and particular moisture conditions and temperatures, this conversion causes a 53% decrease in volume of hydrated material; however, this internal volume change occurs without a dramatic alteration of the overall dimensions of a concrete element, resulting in increased paste porosity and decreased compressive strength.

The design of using calcium aluminate must therefore be based on long term performance, not on the high but transient strengths that can occur initially. Long-term compressive strengths of 40 MPa are typical for properly designed calcium aluminate cement concrete. Higher strengths can be obtained with limestone coarse aggregate, as compared with some other aggregates, which do not perform as well. For this reason it is recommended that calcium aluminate cement not be used for certain types of construction, such as pre-stressed concrete or other structural applications.