Flexural Strength and Deformations Capacity of Structural Beams Reinforced with Steel Bars Milled from Recycled Metals in Ghana

Abstract

Steel is extensively used as a reinforcing material for concrete structures in Ghana. In order to meet this high demand, some local steel manufacturing companies use recycled scrap metals to manufacture steel bars to augment the quantity that is imported. However, the physical and mechanical properties of these reinforcing bars have recently been criticized by practitioners in the construction industry. This research assessed the strength and deformation behaviour of steel reinforcing bars locally manufactured in Ghana. Reinforcing steel bars from three local milling companies, randomly categorized herein as STSL, B5PL, and FBML were selected to evaluate their strength and deformation characteristics in structural concrete beams. Similar tests were also conducted on imported standard high yield bars categorized herein as AM. The results indicated that beams reinforced with AM bars under monotonic loading resisted the highest experimental failure loads (approximately 65 KN on average) as compared with beams reinforced with locally manufactured bars. This was attributed to the high tensile properties of AM reinforcing bars (497 N/mm2 strength and 763 N/mm2 maximum). The cracking loads of the AM-reinforced beams also averaged 10.5 KN and ranked high together with the FBML and B5PL-reinforced beams. The failure loads of B5PL-reinforced beams ranked next with an average of 56 KN, followed by FBML with 47 KN. The lowest value of 38.5 KN was recorded by STSL beams. The average cracking load was similar for AM, FBML, and B5PL- reinforced beams with a value of approximately 10.5 KN, but the STSL-reinforced beams had the lowest cracking load averaging 5.5 KN. The impressive performance of B5PL-reinforced beams among the three locally manufactured reinforcements could be attributed to their higher yield strength, higher rib height, and comparatively smaller rib spacing. This also showed in the strong resistance of B5PL to deflection as compared to the other two locally manufactured reinforcements. Under cyclic loading, AM reinforcements again recorded the highest cracking load (7.5 KN on average) and average failure load (93 KN) owing to its high tensile strength. Regarding the three locally manufactured reinforcing bars, the B5PL-reinforced beams again recorded the highest experimental failure load (55 KN average), followed by FBML-reinforced beams (54 KN on average) with beams reinforced with STSL again recording the least (41 KN).