Experimental investigation into mode-I interfacial fracture behavior between rock and self-compacting concrete in rock-filled concrete

In recent decades, rock-filled concrete (RFC) has been widely adopted in the construction of massive concrete structures. RFC is similar to normal concrete materials and is commonly considered a composite material consisting of coarse rock aggregates, self-compacting concrete (SCC), and an interfacial layer in between. However, coarse aggregates larger than 300 mm in size normally occupy more than half the volume portion in RFC, forming a structural skeleton before the pouring of the SCC binder, and their interfaces with SCC may play a different role in the damage and fracture behavior as compared to that of the normal concrete. To investigate the mode-I fracture behavior of RFC along this type of interface, wedge splitting tensile (WST) tests were carried out in this study, and various influential factors were considered, including the SCC strength grade, rock surface roughness, and the purposeful covering of the interface by stone powder. Typical test results, including fracture loads, crack opening displacements, splitting failure characteristics, and their relationship with the considered factors were analyzed. Through comparison analyses, it was found that the surface fluctuation degree parameter shows the best positive correlation with the fracture properties from WST tests. Tension-softening curves (TSC) representing the interfacial cohesive behavior were determined, and a unified function was proposed for all test conditions. Following a comparative analysis of the strength and fracture properties from the interfaces of rock-SCC and those between rock and normal vibrated concrete, it was found that two ratio parameters (Rft and RGF) of the rock-SCC interface are approximately at the same level as those of the interface between rock and normal vibrated concrete.