Performance of Polyurethane Mixtures with Skeleton-Interlocking Structure

Asphalt is a kind of temperature-sensitive material, and the temperature stability of asphalt mixtures is not very good. The production of hot-mix asphalt mixtures consumes a substantial amount of energy and produces carbon dioxide (CO2) emissions. Polyurethane (PU) mixtures have better high-temperature stability and durability. Besides, the production of PU mixtures can save energy and reduce CO2 emissions because the materials can be prepared at room temperature. However, traditional mixture structures were not suitable for PU binders. In this work, the GB5 mix design was used to decrease the influence of boundary interactions and discrete interactions on the void ratio of aggregates; therefore, a PU mixture with a skeleton-interlocking structure (PUM) was prepared. Properties and functional groups of the PU were assessed by use of the Brookfield rotational viscosity test, Fourier transform infrared spectroscopy (FTIR), and dynamic mechanical analysis (DMA). The high- and low-temperature stability, water stability, and fatigue resistance of mixtures were evaluated by use of the wheel-tracking test, low-temperature bending test, freeze-thaw splitting test, and fatigue test. Results suggested that the PU material was the prepolymer of isocyanate and polyhydric alcohols, and the isocyanate group was present in excess. Higher construction temperatures were indicative of shorter operating times of PUM. Additionally, 3% retarder of PU can prolong the allowable operating time for 5–10 min, and 5% retarder can prolong for 10–20 min. Measurements of PUM met requirements for hot-mixed modified-asphalt mixtures. The low-temperature stability, water stability, and fatigue resistance of PUM were improved when compared with other mixtures. In addition, PUM demonstrated excellent high-temperature stability.