Abstract: An ettringite-producing hydraulic cement especially adapted to the high speed production of carbon dioxide resistant cement board produces essentially all of its potential ettringite within about 20 minutes after it is mixed with water. The cement is non-expansive and sets within about 25 minutes at a temperature of from about 65.degree. F. to about 150.degree. F.

Abstract: A rapid reaction of high alumina cement, gypsum, lime and water produces cementitious compositions in which the only significant factor contributing to strength during the very early stages of hydration (i.e., a few minutes to a few hours) is the formation of an amount of ettringite equal to from about 40% to about 60% of the weight the paste of water, the high alumina cement, the gypsum source, and the lime source. A substantially impermeable concrete having a 4-hour compressive strength of about 8000 p.s.i. may be produced from the cement powder of this invention.

Abstract: A combination of a hydroxy polycarboxylic acid and sucrose improves the water-demand, setting, and compressive strength properties of a calcium sulfoaluminate cement to a greater degree than would be the case if the hypothetical cumulative effect of two admixtures were operative.

Abstract: A combination of a hydroxy polycarboxylic acid and a starch hydrolyzate improves the compressive strength at early and late ages of a calcium sulfoaluminate cement.