Investigation of Lift Bonding for Roller-Compacted Concrete with Low Normal Loads at Variable Placement Times

A problem arises when roller-compacted concrete (RCC) is placed in lifts where the normal loads at the lift-joint interface are relatively low. A study was conducted to investigate the effects of lapses of time between lifts on shear, tensile, and bond strengths of an RCC structure. Three test sections were constructed, each including two 6-in.-thick lifts, with the second lift placed at either 4, 13, or 24 hr after the first lift was finished. Results of the study showed that if the second lift is placed within four hours of the first, the overall strength of the joint bond is increased. If the second lift is placed within 13 hr of the first, the strength of the joint bond varies between increased and decreased strength throughout the surface area of the joint indicating signs of differential set times over the surface of the first lift. When the second lift is placed after 24 hr, the overall strength of the bond is decreased. These findings resulted from the execution of four different shear tests on each test section, where each shear test uniquely quantified the bond strength of the joint interface. The most adequate test method to quantify the shear strength of the bond was found to be the procedure in ASTM D 5607-08.