Fiber-reinforced concrete and reinforcing material for concrete

A fiber-reinforced, craze-resistant and high tensile strength concrete composite comprising a concrete matrix containing from 1 to 6% by volume of a mixture of short steel fibers (A) having a length of about 20 to 60 mm. and a Young's modulus higher than that of concrete and short polyethylene fibers (B) having a length of about 5 to 100 mm. and a Young's modulus lower than concrete, said fibers (B) further having surface protrusions along the longitudinal axis so that the fiber is firmly adhesive to the concrete matrix, with both of said fibers being dispersed in the concrete matrix in a volume ratio (B)/(A) ranging from about 0.5 to 6, the reinforcing amount of short steel fibers (A) ranging from about 0.5 to about 3% by volume and the reinforcing amount of short polyethylene fibers (B) ranging from about 0.5 to about 5% by volume.