Effect of polyurethane addition on the dynamic mechanical properties of cement emulsified asphalt

Abstract

As widely used in railway construction, cement emulsified asphalt (CA) is mainly composed of cement hydrate and emulsified asphalt, playing a key role in supporting structure and track vibration reduction. This work explored the effect of polyurethane (PU) addition on the dynamic mechanical properties of CA. It showed a nonmonotonic variation of 0 ∼ 20 wt% PU loading to the cement on the dynamic stiffness of CA, while 5% and 10% PU could improve both the dynamic stiffness and damping capacity. As for the fatigue life measured by dynamic mechanical analysis (DMA), it is found that the addition of PU can prolong the fatigue life of CA, and this effect is most prominent when the PU loading is 10 wt%. Microstructures and chemical composition were studied by scanning electron microscope (SEM) and Fourier Transform Infrared Spectrometer (FTIR) to explore the original reason for the enhanced dynamic mechanical properties of CA modified by PU. A core–shell structure composed of anionic PU covered on the surface of cationic emulsified asphalt was found, and this PU induced inorganic–organic transition layer between asphalt and cement may play an important role in the enhancement of dynamic mechanical properties of CA.