PURPOSE: To settle various building problems with the rusting of reinforcement, the cracking caused thereby, the destruction caused by the incursion of acid rain, and the weight of iron and to easily construct a concrete structural body without requiring any skill by reinforcing the concrete structural body with lightweight and non-corrosive fiber-reinforced resin.

CONSTITUTION: Fiber-reinforced composite materials 3 instead of reinforcements are provided in concrete 2. As the composite materials, glass fibers are cut in proper length and are mixed. Since its specific gravity is the approximately same as that of cement, the cement and glass fibers 3 are uniformly mixed with each other when they are stirred with water, the glass fibers are not settled even in the course of solidifying the cement gradually, and the glass fibers exist in the concrete 2 at the uniform ratio. By the constitution, the weight of reinforcing material is greatly reduced, and the corrosion of the reinforcing material caused by salt can be prevented.