Improvement of Water Stability of Single-Component Polyurethane Mixture

AbstractPolyurethane mixtures (PUMs) exhibit excellent road performance and low energy consumption and emissions during construction and are expected to replace asphalt mixes in steel bridge deck paving and snow removal. However, their poor hydrolysis resistance leads to inferior water stability, limiting their applicability. Although researchers have attempted to use polyurethane with a suitable hydrolysis resistance or improve the grading, among other measures, the improvement is limited, and polyurethane can negatively impact other road performance indicators. In this study, polymerized carbodiimide (PCDI) was used to increase the hydrolysis resistance of PUMs. The effect of PCDI doping on the performance of polyurethane was examined through water-absorption, tensile, and contact-angle tests. Additionally, the effects on the high-temperature and low-temperature performance and water stability of the PCDI-doped PUM were investigated. The effects of hydrolysis and plasticization on the road performance of PCDI-doped PUMs were analyzed. The results indicated that the PCDI reduced the water absorption and tensile strength and increased the elongation at break of the polyurethane specimens, whereas it hardly affected the contact angle of the specimens. The recommended dosage of PCDI with regard to performance and economic cost is 1%. The addition of PCDI significantly improved the water stability of the PUM: the residual stability ratio and residual stability increased by 48.0% and 52.1%, respectively, and the tensile-strength ratio and post-freeze–thaw splitting strength increased by 137.5% and 151.2%, respectively, with less effect on the high-temperature and low-temperature performance, indicating that the addition of PCDI is a feasible method for enhancing the water stability of PUMs. The hydrolysis of polyurethane significantly degraded the high-temperature and low-temperature performance and water stability of the PUM. The recovery of the plasticizing effect restored the road performance to a certain extent; however, it was not restored to the state where no hydrolysis occurred.