Introduction of Fracture Resistance to the Design and Evaluation of Open Graded Friction Courses in Florida

摘要

A dog-bone direct tension test (DBDT) to accurately determine tensile properties of asphalt concrete, including OGFC, was conceived, developed and validated. Resilient modulus, creep, and strength tests were performed at multiple temperatures on dense-graded and OGFC mixtures produced two aggregates with both the newly developed DBDT and existing Superpave IDT. Excellent correspondence was observed between properties determined from each type of test, indicating that fundamental properties can be accurately determined using either test. Differences in strain rate between the two tests resulted in expected differences in strength and failure strain. Creep compliance was highly correlated between the two tests but was lower for IDT than for DBDT, which can be attributed to the higher confinement in IDT. It was concluded that DBDT compliance is more appropriate for uniaxial stress states, while IDT compliance is more appropriate for biaxial stress states. Continued use of Superpave IDT was recommended because it is much more practical. A composite specimen (OGFC on HMA) direct tension fracture test was developed to evaluate the effects of OGFC and interface conditions on top-down cracking performance. Results indicated that use of polymer modified bonding agents can significantly improve cracking resistance of pavements with OGFC. Continuum and micro-mechanics based FEM models developed to predict cracking performance of composite mixtures indicated that traditional OGFC accelerates development of top-down cracking and should not be assigned a structural benefit in pavement design. The modeling results also indicated the benefit of polymer-modified bonding agents. The benefits of using micro-mechanics to optimize OGFC design were illustrated. Recommendations were made for continued development and validation of testing and modeling of composite systems to optimize OGFC design.