Production and application of high strength concrete reinforcing bar

Niobium has been used to strengthen high carbon (0.40% C) reinforcing bar for a number of years. Industry demands for improved bendability, toughness and weldability have prompted investigation of steels having lower carbon contents similar to the ranges used in traditional HSLA products. The paper reviews specifications governing production of high-strength reinforcing bar and describes the important metallurgical considerations in applying niobium strengthening to bar-mill products. Results are presented of numerous investigations conducted by the authors which illustrate the interplay between steel composition, bar size, reheating rolling and cooling conditions and their effect on final mechanical properties. (AU)