67 Proceedings of the Technical Sessions, 26 (2010) 67-74 Institute of Physics – Sri Lanka Study of elastic properties of reinforcing steel bars Study of Elastic Properties of Reinforcing Steel Bars J. A. Shayan R. Peiris and Ramal V. Coorey Department of Physics, University of Colombo, Colombo 3 ABSTRACT Reinforcing steel bars (rebars) are used for reinforcing concrete. The elastic properties of rebars affect the load bearing capacity of a structure. In this research, the ultimate strength, yield strength, percentage elongation at fracture, mass per meter length and stress ratio of four popular brands of steel rebars (whose names are not permitted to be disclosed) having diameters 10 mm, 12 mm, 16 mm and 20 mm were compared and contrasted against each brand under investigation. The research was conducted based upon the standards established by the SLS 375, SLS 978 and BS 4447 at the Material Research Laboratories of Sri Lanka Standards Institute and National Building Research Organization, Sri Lanka. 1. INTRODUCTION A rebar, or reinforcing bar, is a common steel bar, and is generally used in reinforced concrete structures. A wide range of rebars with different shapes and sizes are available in Sri Lanka and is given ridges for better mechanical anchoring into the concrete. Mild steel rebars are the most common, as its price is relatively low while it provides material properties that are acceptable for many applications. Low carbon steel contains approximately 0.05–0.15% carbon and mild steel contains 0.16–0.29% carbon, therefore it is neither brittle nor ductile. Mild steel rebars have a relatively low tensile strength, but it is cheap and malleable. The density of steel is varies from 7.6 to 8.0 g/cm 3 [1] and the Young's modulus is 210,000 MPa [2]. Concrete is reinforced with slender cylindrical steel rebars where the rebars are placed at structural locations where bending forces will produce internal tensile stresses and to transfer these forces from the concrete to the steel reinforcement, a good shear bond must be developed between the concrete and steel and for this reason rebars are manufactured with small surface deformations to enhance shear transfer [3]. The mechanical properties of steel rebars affect the load bearing capacity of a particular structure. The properties most commonly used for rebars as a basis for specification and design are the specified minimum yield strength and the specified minimum ultimate strength, both obtained from tensile tests on specimens of steel rebars. Rebars can be either smooth or deformed and they are produced by hot rolling or cold working processes [3]. Work hardening, strain hardening, or cold work is the strengthening of a material by, plastic deformation. Any material with a reasonably high melting point such as metals and alloys can be strengthened in this fashion. Metal alloys not agreeable to heat treatment, including low-carbon steel, are often work-hardened. Thus, cold working generally results in higher yield strength as a result of the increased number of dislocations and a decrease in ductility [4]. Hot rolling is a hot working metalworking process where large pieces of metal, such as slabs or billets, are heated above their recrystallization temperature and then deformed between rollers to form thinner cross sections [5].