Mechanical assessment of steel rebar types milled from scrap metals and billets as used in Nigerian construction industries

This study investigated the mechanical properties of steel reinforcement bars from five local Nigerian steel industries—Prism Steel Mills, Ikirun (PR), Dust Steel Mills Ilorin (DT), Euro Therm Steel Mills Ife (ET), Top Steel Nigeria Ltd Ikorodu, (TOP) and Tiger TMT Steel Mills Ogijo (TMT) and two foreign brands, Star Steel Rebars from the UAE (ST) and PSL Steel Rebars from India (PSL), where four of the local companies (Prism, Dust, Euro Therm, and Tiger TMT) produced their rebars using recycled scrap metals, Top Steel (TOP) and the two (2) foreign brands (ST and PSL) used billets as raw materials. Tests were carried out following BS 4449 and ASTM A706M standards to assess hardness and tensile strength (Yield Strength (YS), ultimate tensile strength (UTS), and elongation) at ambient conditions, using the Mechanical Workshop of the National Centre for Agricultural Mechanization (NCAM) in Kwara State for tensile tests and Finlab Nigeria Ltd in Lagos for Vickers hardness testing, with results showing that imported rebars had yield strength between 432.5–495.6 N/mm², ultimate tensile strength between 610.8–622.4 N/mm², and elongation between 13.9–14.5%, while locally produced rebars showed yield strength between 345.8–497.8 N/mm², ultimate tensile strength between 575.3–623.3 N/mm², and elongation between 12.9–15.2%, and all rebars met the minimum required stress ratios of 1.08 (BS 4449) and 1.15 (ASTM A706M), with Vickers hardness values ranging from 352HV to 526HV for all samples except Prism Steel, which recorded a value of 662HV—slightly above the maximum limit of 650HV—demonstrating that although all tested rebars met Nigerian standards, regular testing is necessary, especially for scrap-based rebars, to ensure quality, consistency, and safe use in construction projects across the country.