Polyurethane, a novel binder, is increasingly used to stabilize crushed stones, forming a polyurethane mixture for highway pavement—presenting a promising alternative pavement material. Polyurethane-based porous mixtures exhibit excellent high-temperature stability, low-temperature crack resistance, and fatigue resistance. However, its performance under the influence of water requires further investigation. A one-component polyurethane open-graded friction course-13 (OGFC-13) mixture was selected as the research object to evaluate the water stability of polyurethane porous mixtures. Using a three-factor, three-level response surface methodology, immersion time, erosion cycles, and flush temperature were designated as independent variables, with the freeze-thaw splitting strength ratio and the raveling loss rate serving as response variables. The statistical significance of each factor’s impact on the responses was assessed, and three-dimensional response surface models were developed to characterize the relationships between variables. The evolution patterns of response values under coupled multifactor effects were analyzed, enabling a comprehensive evaluation of the water stability in large-pore polyurethane mixtures. The results indicate that the residual strength ratio from the freeze-thaw splitting test for the polyurethane mixture ranges from 45% to 65%, significantly lower than of 75% to 84% range observed for high-viscosity asphalt mixtures. This discrepancy is attributed to the combined effects of immersion time, erosion cycles, and flushing temperature. Moreover, the raveling loss rate for the polyurethane mixture ranges from 13% to 22%, which is considerably higher than of 6% to 12% observed for high-viscosity asphalt mixtures. These findings highlight the poor water stability of the polyurethane mixture. Further improvements in the polyurethane binder are necessary to enhance its water stability.
Zhang et al. (Sun,) studied this question.