Abstract
This paper is reports the physical properties of the concrete under higher temperature 100℃ to 1000℃, mainly on the reduction in strength and change of elasticity with the rising of temperatures. (A) The reduction in strength with the rising of heating temperature is comparatively slight. (B) The reduction in elasticity is remarkable. (C) The concrete heated to over 500℃ is difficult to use again. (D) For the concrete heated bellow 500℃, natural recovery of strength and elasticity are remarkable. Thus, if we settle the covering of fire prevention around the main steel bars in the section of members to keep bellow 500℃, it may be regarded that the reduction in durability of the concrete, composed the interior members, is to be comparatively slight. Moreover, it recovers the strength in nature as time goes by, and it is probable to use again. Considering the flow of steel at high temperatures, however, it is preferable that the temperature as a basis of calculation of the covering of fire prevention is 400℃ at the main steel bars.
