Bond stress between steel deformed bars confined with steel fiber reinforced concrete

Abstract

Bond interaction between steel bars and concrete plays important role in providing good performance of reinforced concrete structures. Bond stress-slip relationship was used to evaluate the performance of Steel Fibre Reinforced Concrete (SFRC) with respect to steel bar diameter and concrete strength. Although the relationship between deformed steel bars and SFRC has been studied, the bond-stress slip relationship between deformed steel bars and SFRC considering the effect of bar diameter and concrete strength is still lacking. The objective of this research was to explore the effects of SFRC with different concrete strength in controlling the bond stress behaviour. The deformed steel bars with herringbone ribs were used to investigate the mechanical interlocking and friction between the steel bar and SFRC. Series of pull-out test were conducted to investigate the behaviour of bond stress between deformed steel bars and confined with SFRC. The pull-out test was used to determine the ultimate load and bond stress-slip of steel-concrete specimens. The effects of steel bar diameters and concrete strengths were investigated by means of 24 pull-out tests comprising plain and confined concrete specimens. Concrete in grades of 30 MPa and 60 MPa and steel bar diameters of 12, 16 and 20 mm were considered for this investigation. Hooked-end steel fibres with optimum volume fraction of 1.5% from the cement proportion were used as the confinement concrete. Specimens comprising 100 mm x 100 mm cubes were tested for compressive strength and 110 mm x 220 mm cylinders were tested for pull-out specimens at 14 days. The highest bond strength values were observed in SFRC specimens in grade 60 (C60-F-12). The results showed that there were significant strength improvement in SFRC. The bond strength between deformed steel bars and confined SFRC concrete increases with smaller bar diameters. The addition of steel fiber leads to reduction of crack width in reinforced concrete specimens.