Failure behavior of functionally graded roller compacted concrete pavement under mode I and III fracture

Today, the idea of functionally graded material (FGM), which refers to using different materials in multiple layers to improve overall system performance, is commonly used in various engineering sciences. The present study investigates the fracture behavior (modes I and III) of the functionally graded concrete pavement (FGCP) when the bottom layer is RCC (roller compacted concrete) and the top one is ordinary PCC (Portland cement concrete) or FPCC (fibrous Portland cement concrete). Results have shown that the FGC specimens’ flexural strength is similar to that of the full-depth ones and adding polypropylene fibers does not improve it; the main fiber effect is related to the specimens’ post-cracking behavior. While adding fibers highly improves the mode I fracture energy, its effect on mode III fracture toughness is negligible. The pull-off test results have also shown that more than 2 h time lag in pouring two layers will result cold joints between two layers.