Lightweight, fiber-reinforced cementitious panels

A reinforced, lightweight, dimensionally stable building panel having a density of 60-85 pcf (961-1360 kg/m3) and a flexural strength of about 750 to 1180 psi consisting essentially of:

• a continuous phase resulting from the curing of an aqueous mixture of a cementitious composition, the cementitious composition consisting essentially of, on a dry basis, 35-70 wt. % reactive powder, 20-50 weight % lightweight filler, 0 weight % glass fibers, and 0.5-5.0 weight % polyvinyl alcohol fibers, the continuous phase being reinforced with the polyvinyl alcohol fibers and containing the lightweight filler having a particle specific gravity of from 0.02 to 1.00 and a mean particle diameter size from 50 to 250 microns and/or fall within a particle diameter size range of 10 to 500 microns, wherein the reactive powder comprises, on a dry basis, 35 to 75 wt. % calcium sulfate alpha hemihydrate, 20 to 55 wt. % hydraulic cement, 0.0 to 35 wt. % lime, and 5 to 25 wt. % of an active pozzolan, the continuous phase being uniformly reinforced with polyvinyl alcohol fibers and containing uniformly distributed ceramic microspheres, the spheres having an average diameter of about 10 to 500 microns (micrometers),
• wherein the polyvinyl alcohol fibers consist of monofilaments and/or multi-filament threads of polyvinyl alcohol optionally modified by a functional group selected from at least one member of the group consisting of carboxyl, amide, nitrile, phosphate, and sulfate, and an optional brightener in the polyvinylalcohol fiber, an optional brightener on the polyvinylalcohol fiber, an optional adhesive agent in the polyvinylalcohol fiber, and an optional adhesive agent on the polyvinyl alcohol fiber, wherein the fibers have a diameter of about 10 to 400 microns (micrometers) and a length of about 0.1 to 1 inches (2.5 to 25.4 mm), and a fiber elastic modulus of 20-50 GPa, and
• wherein the resulting lightweight building panel has a thickness of 0.25-1.0 in. (6.3-25.4 mm).