Fracture resistance characterization of chemically modified crumb rubber asphalt pavement

The fracture resistance of chemically modified crumb rubber asphalt (CMCRA) pavement was evaluated based on the J-integral concept. The chemical modification process used was developed by the Federal Highway Administration and patented in 1998. The results were compared to that of crumb rubber asphalt (CRA) and control asphalt pavement. Four semi-circular core specimens (76 mm radius and 57 mm thickness) were cut from each gyratory compacted cylinder (GCC) for the fracture resistance tests. Notches with different depth to radius ratios were introduced at the middle of the flat surface of each specimen. Three point bend loading was used to allow the separation of the two surfaces due to tensile stresses at the crack tip. It was found that the CMCRA pavement, had the highest residual strength, at all notch depths tested. The fracture resistance of the CMCRA pavement, based on Jc was found to be about twice that of the CRA and control pavements. The CRA pavement was found to have a slightly higher fracture resistance than that of the control pavement. Scanning Electron Microscopic examination of the fracture surface of each mixture revealed the microstructural origin of the improved fracture resistance of the CMCRA pavement in comparison with the control pavement.