| 摘要 |
PROBLEM TO BE SOLVED: To provide a non-combustible building material, even if polyvinyl alcohol is added largely as possible for improving its workability on cutting, which has improved mechanical strength corresponding to the addition efficiency thereof, further has a smooth surface of a formed body, and has good appearance. SOLUTION: A formed body essentially consisting of cement, and containing 5.5 to 10.0 wt.% polyvinyl alcohol, and further containing a hydroxide such as magnesium hydroxide and aluminum hydroxide releasing water on thermal decomposition is provided. This formed body is impregnated with an aqueous solution of boric acid or an aqueous solution of borate, and is further thermally hardened to obtain the cement based non-combustible building material. The formed body is heated while infiltrating an aqueous solution of 0.1 to 3.0 wt.% boric acid or borate into the surface layer of the formed body, so that polyvinyl alcohol is not eluted, and its appearance is made satisfactory. Further, since the formed body is hardened after the aqueous solution is sufficiently melted to the inside of the formed body, its mechanical strength sufficiently increases. |
