Flexural behaviour of one-way concrete slabs reinforced with steel bars milled from scrap metals

Laboratory tests were performed on 12 simply-supported one-way concrete slabs reinforced with steel bars that were milled from scrap metals. The slabs were subjected to concentrated line loads at the third points. Two different failure modes of flexural yielding of the tension bar or flexural crushing of the concrete were predicted. The observed failure modes, however, were either one or a combination of modes of tension failure, concrete crushing, diagonal shear, or shear bond failures. On the average, for one-way slabs with span-to-effective depth ratios varying between 14 and 24.37, and shear span-to-effective depth ratios varying between 4.6 and 8.12, a short-term factor of safety of approximately 1.3 against cracking and 0.94 against collapse were obtained from the experimental results. Based on the analysis of the experimental results, it is proposed that an average steel strength of about 370 N/mm2 for steel bars milled in Ghana must be used in reinforced concrete design rather than the characteristic strength of 250 N/mm2 conventionally prescribed by BS8110 for mild steel.