Shear behaviour of UHPC containing coarse aggregates– alkali-activated slag concrete interface considering the combined effect of dowel action and prefabricated groove

With superior mechanical performance and low carbon emission characteristics, ultra-high performance concrete containing coarse aggregates (UHPC(CA)) and alkali-activated slag-based concrete (AASC) are promising construction materials for future infrastructure and buildings. In view of the advantages of precast technology, UHPC(CA)–AASC composite structures can be proposed and applied in civil engineering . In composite structures, the shear performance at the composite interface is vital for the overall structural performance and safety. In this study, 54 UHPC(CA)–AASC specimens was investigated focusing on the effects of several factors on the shear performance of the composite interface, including the concrete strength of the AASC, characteristics of the interfacial shear reinforcement, interface treatment methods, and lateral pressure . The test results and comparative analysis showed that the UHPC(CA)–AASC specimens had ductile failure , except for specimens with an insufficient embedment depth of shear reinforcements or low lateral pressure. Improving the interface roughness and using interface agents significantly improved the ultimate shear capacity of the specimens. Moreover, the combined effect of dowel action and prefabricated groove on the interfacial shear resistance capacity were analyzed quantitatively. As the shear reinforcement ratio and strength grade increased from 0.52 % to 1.57 % and from HPB300 to HRB500, the ultimate shear capacities increased by 23.9–61.4 % and 121.2 %. While when diameter of shear reinforcements increased from 8 mm to 12 mm and the embedded depth decreased from 10 D to 3 D , the ultimate shear capacities reduced by 25.4 and 88.7 %, respectively. For the prefabricated groove composite interface, the ultimate shear capacity enhanced by 35.0–57.1 % with the AASC strength grade improved from C30 to C50. Based on the test results and theoretical analysis, a new equation was proposed to predict the shear resistance capacity of the UHPC(CA)–AASC interface, combining the interfacial cohesion, shear friction, dowel action of shear reinforcements, and shear contribution by the matrix in the groove joint . The results calculated using this equation showed good agreement with the experimental results, suggesting that this equation can reliably predict the ultimate shear capacity of the UHPC(CA)–AASC interface.