Characteristics of Water-Foamed Asphalt Mixture under Multiple Freeze-Thaw Cycles: Laboratory Evaluation

Abstract

A major concern with the application of water-foamed asphalt mixtures is the possible performance degradation caused by the presence of inclusion water during production. Inclusion water left in the asphalt mixture after compaction affects the performance of the asphalt mixture. The objectives of this study are to investigate the impact of different foaming conditions on the performance of water-foamed asphalt mixtures prepared using oven-dried aggregates, examine the freeze-thaw resistance of water-foamed asphalt mixtures, and assess the water-foamed asphalt mixture damage level after multiple freeze-thaw cycles through an ultrasonic direct test. The samples for this study were prepared in the laboratory based on the method of Superpave mix design. The control groups were mixed and compacted at 135°C and 148°C, respectively. The water-foamed asphalt binders were prepared at different foaming temperatures, i.e., 12°C and 135°C, and the amount of water agent used in this process was .%–2.% by mass of asphalt binder. The water-foamed asphalt samples were mixed at various foaming temperatures but compacted at 135°C. Based on the laboratory test results, the foaming temperature and the inclusion water from the foaming process significantly affected the air void and the tensile strength of the asphalt mixture and the void in the mineral aggregate. The freeze-thaw cycle accelerated the destruction of the internal structure of the asphalt mixture and resulted in an increase in porosity and decrease in cohesive strength between the asphalt binder and aggregate. The ultrasonic direct test method was found to be a feasible approach to assessing the potential damage in water-foamed asphalt mixtures.