Durability of Ultra Silent Pavements

Abstract

Ultra-silent pavements (USP) are developed as surface layers with excellent noise reducing proper- ties, mainly due to their high air void content. However, the open structure of USP facilitates water intrusion and makes them vulnerable to moisture damage. Past experience has shown that USP mix- tures often exhibited ravelling, and poor adhesion with the underlying layer due to moisture. This study aims to quantify the effects of moisture on the strength of USP mixtures and on their adhesion to the base course. Three different mixtures were tested and their strength degradation due to moisture was evaluated through indirect tensile tests, whereas the interlaying bonding between the USP and the underlying layer was investigated using tensile adhesion tests. Both tests were performed at dry and wet conditions, on fresh and aged materials. The results showed that moisture does not necessarily decrease the strength of USP mixtures. However, the results revealed the adverse effect of moisture on interlayer bonding. Furthermore, moisture diffusion simulations were performed using the finite element method to in- vestigate how different values of the moisture diffusion coefficient of the binder affects the saturation of the mixture. For this, very fine meshes of each USP mixture were made using 2D images obtained by means of CT-scanner. The analysis revealed that mixture design influences the rate in which saturation takes place. Other properties of the USP like the dynamic stiffness modulus and the cohesive strengths are determined in the laboratory to be used for structural finite element analysis. Via a moving wheel load model, the tensile stresses at the bottom of the USP layer were compared to the adhesion strengths measured in the lab.