Interlayer shear strength of Roller compacted concrete (RCC) with various interlayer treatments

Roller compacted concrete (RCC) is constructed in layers. It is a dry and lean concrete with the interlayer being generally weak. In this paper, the shear strength of RCC interlayer under different time intervals and interlayer treatments are studied, and the corresponding change laws of shear behaviors are analyzed. Through the comparison of the test results at different time intervals, it was found that the peak shear strength decreases with increases to the time interval. Before the initial setting, the influence of time interval is relatively small. Between the initial setting and before the final setting, the influence of time interval becomes evident, and after the final setting it is seen that the influence of the time interval is much greater. Three interlayer treatments are tested, namely, mortar, expansion agent with mortar, and nano SiO2 with mortar. It was seen that treatments with the expansion agent and the nano SiO2 improve shear strength more than that of mortar alone. The cohesive stress c and friction coefficient f of the RCC interlayer are calculated for each case. At peak stress, f keeps steady and c decreases with the increase of the time interval. For treatments with nano SiO2, values of c were observed to be improved while for treatments with the expansion agent, higher values of f were seen. The shear strength of RCC interlayer can be well explained by using test results of scanning electron microscope to provide a view of the structure on the mesoscopic scale. The results of this paper are helpful to understand the influence laws of shear strength of RCC interlayer, and it has significance for the improvement of interlayer construction technology of RCC.