Design and Evaluation of Ultra-Thin Overlay with High Viscosity and High Elasticity †

Ultra-thin asphalt overlay, which is considered one of the main pavement maintenance strategies, has been widely used to maintain and restore pavements. However, the structural properties of traditional ultra-thin overlay materials, such as anti-friction and anti-cracking pavement surfaces, do not last longer under the climate change and traffic loading conditions. This paper introduces an innovative design of ultra-thin asphalt overlays with high viscosity and high elasticity, which provide not only a long service life of anti-resistance and anti-cracking performance, but also lower traffic noise and smoother riding quality. The process of designing such ultra-thin lift overlays involves multi-objective optimization of the overlay’s structural and functional performances, including the quality and quantity of asphalt additives, gradation of coarse aggregates and materials’ engineering, and cohesive and adhesive properties of asphalt overlays. During the lab tests prepared for this study, the compound-modified asphalt was prepared by modifying base asphalt with the high viscosity and high elasticity modifier. The gradation design was performed to improve coarse aggregate voids’ filling and the density of the mixture, and the trackless tack coat emulsified asphalt was used as an adhesive layer material. Laboratory tests were conducted to evaluate the performance of the asphalt mixture and bonding effect of trackless tack coat emulsified asphalt. Results showed that the high viscosity and elasticity ultra-thin overlay exhibited excellent performance in terms of skid resistance and noise reduction. The interlocking effect of the coarse aggregate skeleton and the optimal asphalt film contribute to the resilient and durable properties of an ultra-thin asphalt overlay.