We live in the building which made of concreat. If a fire break out in the building on a sudden, the heated concreat structual of the building were become very weak and bad poor. In this study, it was investigated by test for thermal expansibility and compressive strength of the highly heated concreat. The experiment was carried out in the temparature range of 150―75$0^{circ}C$. The obtained results are as follow. 1. The heated concreat has weaken in compressive strength from about at 30$0^{circ}C$. 2. The concreat heated over 45$0^{circ}C$ is not proper for structual material. 3. The concreat expanded remarkable when it was heated about at 450―$600^{circ}C$.