Research on fracture characteristic of gneiss prepared asphalt mixture with direct tensile test

Asphalt pavements are suffering from severe stress-related failures such as cracks, which are mainly caused by fractures in asphalt mixtures. Several evaluating and analyzing techniques are available on evaluating fracture characteristic of asphalt mixture. Among them, the direct tensile test (DTT) is frequently applied in laboratory research due to its benefits over indirect tensile test (IDT) for the increasing use of finer aggregate gradation and polymer modified asphalt in asphalt mixtures. The major objective of this study is to determine the effects of binder type, temperature and strain loading rate on fracture characteristics of gneiss prepared asphalt mixtures. Initially, specimens were prepared by Superpave gyratory compactor and subsequently processed carefully to required dimension. Then direct tensile tests were conducted with linear strain-increasing controlling mode at different temperatures (15 °C, 25 °C) in combined with various strain loading rates (0.1, 0.5, 1 and 18 mm/min). Test results indicated that the direct tensile strength (DTS) decreased as temperature increased at the same strain loading rate. Additionally it was shown that the DTS got larger at higher strain loading rate. Besides, the image analysis related to fracture mode at splitting cross section indicated that adhesive fracture was dominant at lower temperature, while at higher temperature the main fracture mode was cohesive fracture. Furthermore, relative higher stress loading rate could increase possibility of adhesive fracture.