Is it true that, because rapid-hardening cements are finer ground, concretes cast with them are more susceptible to shrinkage cracking than if other portland cements were used?
This is generally true. Rapid-hardening cements are ground more finely than other cements, do shrink more, and are therefore more likely to show cracking. However the chemical composition of the cement also affects the result: recent research has proved that although a paste made of finer cement may shrink more than one made with coarse cement, there may be no difference when they are used for comparable concretes. Shrinkage is still a complex and not fully understood phenomenon. Current research indicates that the amount of gypsum added during manufacture of the cement may be equally if not more important than fineness. Curing, mix proportions, and water content are usually far more significant in influencing the degree of shrinkage.