Abstract: Disclosed is a rust preventive composition for steel reinforcements for concrete, which comprises 100 parts by weight of Portland cement, 0.3 to 3 parts of a hydroxycarboxylic acid, 0.3 to 3 parts of a saccharide, 2 to 10 parts as a solid content of a polymer latex, 0 to 5 parts of an optional additive and 30 to 45 parts of water, all parts being by weight. In this composition, an excellent synergistic effect is attained by the combined use of the hydroxycarboxylic acid and saccharide. That is, hydration is almost completely suppressed in this composition under ordinary rust preventing treatment conditions, but hydration is effectively promoted under high-temperature high-pressure hydrothermal curing conditions. Gluconic acid and sorbitol are especially preferred as the hydroxycarboxylic acid and saccharide, respectively.

Abstract: A novel process is provided for producing prefoam type cellular concrete articles, which uses a foamed slurry (E) consisting essentially of an aqueous slurry (A) of a calcium silicate-based cement compound, an aqueous slurry (B) of a calcium aluminate-based cement compound, a specific setting retarder (C), and an aqueous foamed liquid (D). The process is further characterized in that: (i) the foamed slurry (E) is cast and provided with hardened strength sufficient for demolding in 20 to 120 minutes after it has been poured into a mold; (ii) the demolded article is subjected to precuring under specific conditions of humidity, temperature and precuring time; and (iii) the molded article is then subjected to hydrothermal curing under high pressure.