Abstract: A cement board of homogeneous composition from face to face and having a substantially uniform thickness is made continuously by distributing a sole cementitious composition on a moving carrier sheet and smoothing the surface by rotating a cylindrical roller in a direction counter to the movement of the carrier sheet. An upper reinforcing network is submerged under the surface by feeding it under the counter rotating roller.

Abstract: Mortar is deflected continuously onto a moving carrier sheet from a distributor belt which is moving transversely to the carrier sheet by a plow which shuttles across the length of the distributor belt. An uninterrupted flow of mortar is spread across the sheet. The layer of mortar on the carrier sheet is slightly undulatory in the machine direction but a lateral cross section has a substantially uniform thickness so that a flat broad ribbon of mortar emerges from under a screed downstream from the shuttle plow.

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 network of reinforcing fibers is pressed against the surface of an underlying carrier sheet by the weight of a concrete mix. A vertical gap between the sheet and the network is created so that the concrete mix may penetrate the voids of the network and spread out on the underlying sheet to embed the fibers.

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 a starch hydrolyzate improves the compressive strength at early and late ages of a calcium sulfoaluminate cement.

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.