Study on Interfacial Shear Bond Behavior Between Ceramsite Foam Concrete and Normal Concrete Under Direct Shear Loading

Ceramsite foam concrete (CFC), recognized for its lightweight, thermal insulation, and eco-friendly properties, is a promising material for composite structures. The interfacial shear bond behavior between CFC and normal concrete (NC) critically governs the structural integrity of CFC-NC systems. This study investigates the interfacial shear bond strength through direct double shear tests on twelve cubic specimens with controlled interface roughness and casting intervals. Quantitative analysis reveals that increased roughness enhances shear strength by up to 28.6~59.5%, while prolonged casting intervals reduce strength by 22.3~34.6%. Notably, excessive roughness shifts failure modes from interfacial debonding to material failure within CFC, where shear bond strength becomes governed by CFC’s compressive strength. A rigid–plastic model is developed to characterize the shear bond behavior of CFC-NC interface and demonstrates 96% accuracy in predicting experimental results. The findings provide useful insights for improving CFC-NC composite design in engineering applications.