Assessment of bonding strength of steel bar in recycled aggregate concrete containing ground palm oil fuel ash

This research aimed to investigate the behavior of bond strength of reinforcing bar in recycled concrete aggregate with and without ground palm oil fuel ash (GPOFA) as a supplementary cementitious material. Recycled concrete aggregate (RCA) was used as a coarse aggregate, and local river sand was used as a fine aggregate. Portland cement type I was replaced by GPOFA at the rates of 0, 15%, 25%, and 35% by weight of the binder to cast concrete. Compressive strength and bond strength of the concrete were determined at the ages of 7, 28, and 90 days. A 16-mm deformed bar was inserted at a center of the 200-mm concrete cube, with the bond length of the steel bar embedded in concrete being four times the bar diameter or 64 mm. Linear variable differential transformer (LVDT) was installed at the bottom and top of the steel bar to investigate the relationship between bond strength and the slip of the steel bar. The results indicated that the compressive and bond strengths of the concrete decreased with an increase in GPOFA replacement. Due to the lower compressive strength, the replacement of ordinary Portland cement (OPC) with a greater amount of GPOFA decreased the bonding strength of concrete containing natural coarse aggregate and recycled coarse aggregate. Moreover, the bond strength between the reinforcing bar and RCA concrete was similar to that of the normal concrete when the compressive strengths of both concretes were similar.