Experimental investigations on the interfacial bond strength of the adhered mortar paste to the new mortar paste in a recycled concrete matrix

Abstract

• The bond strength between adhered recycled mortar and natural mortars was studied experimentally using slanted shear tests. • The friction is affected by the roughness and ranges between 0.69-0.8796 and the cohesion was between 0.13-4.60 MPa. • Substitution ratios of 20% and 50% of recycled sands showstronger bond, due to the presence of unhydrated cement particles. The present study describes an experimental approach to the assessment of the bond strength in the interface between adhered mortar paste and new mortar paste in recycled concrete based on slanted shear tests. The mortar mixtures were made of recycled sand with 0%, 20%, 50% and 100% of substitution ratio and three different roughness of the interface were considered. The roughness affects the bond strength significantly, especially for substitution ratios of 20% and 50% which showed a higher strength compared to the control mixture. This increase can be linked to the presence of unhydrated cement and clay particles in the recycled sand. This effect is not visible for full substitution, where SEM analysis show a significant network of microstructural cracks. The friction coefficient ranged between 0.69 and 0.8796 and the cohesion between 0.13 MPa and 4.60 MPa.