Investigation into strength properties of ribbed reinforcing mild steel bars produced by local companies in Ghana

Abstract

The construction of high-rise buildings has increased the production of ribbed mild steel bars in Ghana. This was motivated by the fact that, the use of substandard ribbed mild steel bars in construction industry causes collapse of structures in many developing countries. This study aimed at investigating the strength properties of ribbed mild steel bars manufactured in Ghana from scrap metals by subjecting the materials to laboratory tests such as tensile tests, chemical composition analysis, microstructure examination and micro hardness tests. Three (3) steel producing companies were considered for this study. A total of forty-five (45) ribbed mild steel bars of 12mm, 16mm and 20mm diameters of length 500mm were used for the tensile strength experiments. The results of analysis indicated that, tensile strength of ribbed mild steel bars produced in Ghana fulfilled the ASTM E8/E8M-16a with ultimate tensile strength of 460N/mm2. Angstrom V-950 Spectrometer was used for chemical composition analysis, fifteen (15) pieces of 16mm steel bars of length 50mm were used. Carbon equivalent values (CEV) were calculated from the results of the chemical composition According to ASTM A706/A706M-09b. The findings build on existing evidence of carbon, manganese, Chromium, silicon and copper being the major elements influencing the strength properties. Vickers hardness tests was also conducted on the Vickers hardness testing machine according to ASTM E92-17. The results showed that, all the three companies obtained higher Vickers hardness value between 194 HV to 403 HV which is above the recommended minimum value 150 HV. The study therefore, concludes that the proportion of chemical composition influenced the properties of ribbed mild steel bars. However, it is recommended to producers to control chemical composition contents especially the carbon, magnesium, Sulphur etc., during the production process and maintain its content in the range of the standards.