Experimental study on interfacial shear strength of concrete construction joints with high <scp>GGBS</scp> replacement level

Abstract The high level partial replacement of ordinary Portland cement (OPC) with ground granulated blast‐furnace slag (GGBS) is being increasingly employed due to the heavy environmental burden of construction work. This study experimentally investigates the interfacial shear strength of concrete construction joints with high GGBS replacement levels. The experimental variables include type of joint (OPC‐OPC, GGBS‐GGBS, and GGBS‐OPC), concrete grade (C45 and C60) and GGBS replacement level (50% and 60%). The compressive strength and shear strength of concrete specimens were obtained for analysis. The morphology and porous zone (PZ) of the bonding interface between new and old concrete were examined by scanning electron microscopy. The experimental interfacial shear strength of concrete construction joints was compared with values calculated by the design equations of existing standards. The results indicate that the interfacial shear strength of GGBS‐OPC concrete construction joints can be 28% lower than their OPC counterparts. The thickness of PZ can be increased by introducing GGBS. The design of the interfacial shear strength of a plain concrete construction joint without normal stress can be determined using the AASHTO equation, provided the surface is roughened by an applied retarder.