Reinforcement steel

Reinforcement steel Reinforcement of concrete with steel is being done for more than 100 years. It is the time proven match for reinforcing concrete structures. At the very beginning of technology simple rounds and squares were used. Sometimes later rails and profiles were also used. The production of specific reinforcement steel started sometimes in 1930s.It was realized that beside the tensile strength, bond between steel and concrete plays an important role in terms of load transfer. Presently the global annual production of reinforcement steel (Fig 1) is more than 210 million tons. Fig 1 Reinforcement steel Reinforced concrete structure is designed on the principle that steel and concrete act together to withstand induced forces. The properties of thermal expansion for both steel and concrete are approximately the same. This along with excellent bendability property makes steel the best material for reinforcement. It bonds well with concrete. Steel is strong in tension at the same time being ductile enough to be shaped or bent. Development process for reinforcement steel For a long time steel bars in as rolled condition were being used for reinforcement purpose. Yield strengths of 350 to 400 MPa were achieved in carbon manganese steels by keeping C to around 0.35 % and Mn in the range of 0.9 % to 1.45 %. But due to ingot casting there was segregation of manganese which was causing brittleness of the steel at the place of segregation. At this stage micro alloying of steel was introduced to achieve the yield strength of the steel by micro alloying it with vanadium, niobium and titanium. Since the carbon content also got reduced these rods were weldable. But the advantage was got negated due to higher cost of these steels. Sometime during 1940s ribs were introduced in...