Using Fine Grained Niobium Micro-Alloyed Rebar in Concrete Bridge Application

摘要

In the USA, over 40% of the functional bridges in 2014 were made from reinforced concrete, making it the largest material used for bridge construction. Reinforced concrete is a composite material comprised of concrete and steel. Concrete is strong in compression, but weak in tension. Reinforcing bar, or "rebar", compensates for the lack of tensile strength in the concrete.The strengths of concrete used in these bridges has been increasing, however rebar has not experienced the same improvements. This mismatch in concrete development vs. reinforcing bar is being addressed to create a composite structural member with optimum mechanical properties.Although there are several routes available to produce higher strength rebar, certain approaches are more favourable in developing key microstructural characteristics that impart optimum mechanical property performance. The use of niobium micro-alloying to develop a finer grained microstructure during rolling will give higher strengths and improved ductility. Discussion is extended to the process metallurgy, the role of niobium in conditioning the austenite and subsequent microstructural transformation.This paper will explore the benefits of a fine grained niobium microalloyed rebar in reinforced concrete for bridges, including: Design improvements reducing the weight of the bridgeImproved ductility at higher strength Reduced concrete congestion Improved weathering properties