Low-Temperature Fracture Characteristics of Selected Warm-Mix Asphalt Concretes

Warm-mix asphalt (WMA) technology is developed by lowering the binder melting point, which may cause WMA to be weak against rutting at high service temperatures. Much research has been done on the high-temperature characteristics of WMA mixtures, but the low-temperature fracture behavior that leads to cracking has not been well evaluated. Because WMA is produced at lower temperatures with a lower aggregate heating, the behavior at the interface where the binder is coating aggregate is in question at low temperatures. In this study, 13-mm, dense-grade WMA mixtures were produced by using WMA binders. Beam specimens were prepared for fracture toughness (K-IC) evaluation at -20 degrees C by a three-point bending test. The results and analyses revealed that the K-IC values of WMA mixtures at -20 degrees C were similar to or better than those of HMA mixtures, even though they were produced at temperatures 30 degrees C or 40 degrees C lower than HMA mixtures.