Study on the Influence Factors of Dynamic Modulus and Phase Angle of Dense Gradation Polyurethane Mixture

Abstract

Polyurethane (PU) mixture is a new pavement material with excellent pavement performance, and most research was focused on the enhancement of pavement performance, but rarely on the dynamic property. This paper studied the factors including gradation, aggregate type, PU type, and PU content, which may influence the dynamic property of the PU mixture. Test results showed that the PU mixture is a kind of linear viscoelastic material, its dynamic modulus and phase angle changed with test temperature and loading frequency, the dynamic modulus would drop by 40%~50% with the temperature raised from 5 °C to 55 °C. All of the factors could affect the dynamic property of the PU mixture which was proved by the analysis of covariance. The effect of gradation did not change with the increase of the nominal maximum aggregate size (NMAS), the dynamic modulus of the PU mixture with limestone was higher than that of the PU mixture with basalt, and the curing speed of PU could affect the ultimate stiffness of the PU mixture, and the increase of the PU content did not help in the increase of the dynamic modulus of the PU mixture. So, more consideration about the selection of gradation, aggregate type, PU type, and PU content should be taken into the design of the PU mixture, which could produce the best pavement structure combination and save more investment.