Evaluation of the tensile mechanical properties of coiled reinforcing bars

It is common practice to use small diameter such as No. 3, No. 4, No. 5, and No. 6 coiled reinforcing bars to fabricate the repetitive items such as stirrups and ties. The fabrication process requires uncoiling and mechanized straightening of the coiled reinforcing bars. These processes will be conducted in the room temperature, i.e. cold –working process. It has been known that cold working changes the mechanical properties of steel such as the yield and tensile strength, and elongation. Many research studies have investigated the cold-working effects on steel sections. However, research investigations on the effects of cold-work on the coiled reinforcing bars have not yet been conducted to date. Hence, it is not verified whether or not the tensile and mechanical properties of the coiled reinforcing bars meet requirements of the current standards such as ACI 318 and ASTM Standards. 335 specimens of No. 3, No. 4, and No. 5 bars were gathered with the help of the Concrete Reinforcing Steel Institute. Tension tests were conducted to measure the strength and ductility of cold-worked reinforcing bars. The main parameters investigated during this study were elongation, yield strength and deformation properties of reinforcing bars after cold-working process. The experimental results indicated an increase in yield strength as well as a decrease in elongation by increasing the amount of cold-working on the reinforcing bars. As a result, some test specimen appeared not meet the current ASTM standards.