Abstract: A fiber-reinforced concrete comprising two kinds of short fibers, one being a short fiber having a Young's modulus higher than that of concrete, the other being a short fiber which has a Young's modulus lower than that of concrete and showing good adhesiveness to concrete. The both fibers are mixed in a predetermined ratio and dispersed in a concrete matrix. A reinforcing material for concrete is also disclosed which material consisting of such fibers as mentioned above.

Abstract: The present invention is concerned with a steel fiber for reinforcing concrete. The steel fiber according to the present invention is a needle-shaped chip resulting from directly machining a steel ingot material. The fiber has a wrinkled surface with a plurality of rugged waves along the length of the fiber. This new production employs a plain milling cutter having a plurality of cutting edges of negative rake angle and twist angle with respect to an axis of the cutter for machining the ingot material by a down-cut milling under conditions of high speed and short depth of cut.