Abstract
Water-foamed asphalt is capable of improving the workability of asphalt mixture. It has been extensively used for its energy-saving and emission-reducing features. Water plays an essential part in improving the workability of water-foamed asphalt mixture. However, there is still lack in profound studies of moisture dissipation of the water-foamed asphalt over time and its influence on workability. In this study, the evolutions of residual water content and rotational viscosity of the water-foamed asphalt with time were respectively measured by the analytical balance and modified rotational viscometer (RV). The atomic force microscopy (AFM) analysis was conducted to discuss the mechanism of viscosity reduction of water-foamed asphalt. The results showed that moisture evaporation is significantly influenced by the foaming water content and ambient temperature, which results in the different stabilizing time of water-foamed asphalt. When water-foamed asphalt was stabilized, the residual water inside the asphalt was less than 0.01% relative to the asphalt mass. The AFM analysis showed that the foaming process changed the distribution of wax in the water-foamed asphalt resulting in reduction of viscosity. The viscosity reduction of asphalt is highly related to the initial foaming water content. After the foaming process, the viscosity keeps stable and is independent of moisture dissipation.
Highlights
Warm-mix asphalt (WMA) mixtures, compared to the conventional asphalt (HMA) mixtures, have gained worldwide popularity recently due to the energy-saving and emission-reducing benefits [1,2]
The results showed that the foaming process reduced the frictional resistance, which is beneficial for coating during the mixing and sliding ability between aggregates during the compaction of asphalt mixtures
The results showed that during the process of moisture dissipation, the viscosity of foamed asphalt kept during the moisture dissipation, the dissipation, viscosity of foamed asphalt constant basically showed thatprocess duringofthe process of moisture the viscosity of kept foamed asphalt kept constant basically and was independent of its residual water content
Summary
Warm-mix asphalt (WMA) mixtures, compared to the conventional asphalt (HMA) mixtures, have gained worldwide popularity recently due to the energy-saving and emission-reducing benefits [1,2]. Only a little water is used as a foaming agent in producing water-foamed asphalt. This is beneficial for environmental protection, and for the reduction of production costs, compared to other WMA technologies using additives [3,6]. Any asphalt, such as the Trinidad Lake asphalt, crumb rubber modified asphalt, and even epoxy asphalt, can be foamed under a suitable foaming condition [7,8,9,10]
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