Expansive Cements

Products made with hydraulic cement are generally desirably possessed of the property of volume stability, i.e., after they have once been formed to the desired dimensions, they retain these dimensions. When the dimensions change significantly, the change is usually regarded as a deleterious effect. Cements are now being produced that take some of the same phenomena that are associated with harmful expansions and utilize these, under controlled conditions, to produce beneficial effects. Two kinds of such effects have been most studied. One is to provide a tendency to expand that may compensate for a tendency to shrink. Such cement is designated shrinkage-compensating expansive cement. The other is to provide a tendency to expand that, when restrained by reinforcing, places that reinforcing in tension. Such cement is designated self-stressing cement. This paper discusses the development and production of these cements.