PURPOSE: To improve adhesion of a concrete product to post-placed concrete without projecting reinforcing bars or the like, that may hinder a bar arranging operation in site, into a hollow part of a centrifugally molded concrete product.
CONSTITUTION: A reinforcing cage consisting of main reinforcing bars 2 and helical reinforcing bars 3 is arranged in a centrifugal molding form 1 made of a steel within the wall thickness of a concrete product. A concrete product body 4 is centrifugally molded into a cylindrical shape with the reinforcing cage provided in the center thereof. Coarse aggregate 6 is integrally provided on the inner-diameter surface of the concrete product body 4 opposed to a hollow part 5. The coarse aggregate 6 exposed to the hollow part 5 forms a rough surface as an integral part of the concrete product body 4, thereby improving adhesion properties to post-placed concrete placed in the hollow part 5 in site.
TOYODA YOSHIHIRO
TSUCHIDA SHINJI
