Abstract
Almost all plastic spacers for reinforcing bar using at construction sites are wheels in shape and play an important part in reinforced concrete structures. As the plastic is lower than the concrete in the strength and elastic modulus, and divide concrete partially, plastic spacers are weak points of reinforced concrete structures. What is worse, one column of thermal expansion coefficient is big and thereby they produce cracks in concrete. We devised the new star-shaped plastic spacers and inspected them by experiments. As a result, what we understood are as follows. (1) Cracks by thermal stress of the new star-shaped plastic spacers are reduced to half in comparison with that of wheel-shaped plastic spacers. (2) It may be said that wheel-shaped plastic spacers must be installed perpendicularly. However, in a good thing the new star-shaped plastic spacers can be installed horizontally.
