Shear friction response of lightweight concrete using bottom ash aggregates and air foams

ABSTRACT This study aimed to estimate the shear friction response of lightweight concrete made using bottom ash aggregates and air foam (LWC-BF) and determine the design parameters including shear transfer capacity, cohesion, and friction angle of such concrete at different interface conditions. The shear friction parameters were straightforwardly formulated from the extension version of the integrated mechanical models derived in our previous study based on the upper bound theorem of concrete plasticity. Eighteen non-reinforced push-off specimens (nine monolithic interfaces and nine interfaces with smooth construction joints) were tested under direct shear and the additional compressive stresses normally applied to the interfaces. The test parameters considered in different interface conditions were the compressive strength of concrete and the magnitude of compressive stresses. The experimental and analytical results showed that the addition of air foam slightly decreases the angle of friction of monolithic interfaces but insignificantly affects that of smooth construction joints. Thus, the effect of air foam added up to 20% by volume on the cohesion and friction angle of concrete was marginal. Therefore, the proposed shear friction parameters are promising to reasonably assess the shear friction strength of LWC-BF interfaces.