Investigation on an Absorbing Layer Suitable for a Noise-Reducing Two-Layer Pavement

A polyurethane-based rubber-modified layer within a road superstructure leads to absorption of traffic emissions. Noise emissions have quite a negative effect on society, as they lead to high stress levels and health risks for people. Therefore, constructional methods of noise-reducing road layers have been developed before. This research paper focuses on the questions whether the existing noise-reducing road constructions, which have a low durability, can be optimized in terms of a longer duration while simultaneously maintaining the noise-reducing effects. Within this research, a large parametric study contributed to an optimal solution of a noise-reducing and durable layer. We found that noise absorption is mainly dependent of the void content of the pavement and its flexibility. Also, a result is that the durability of a road layer is based on the properties of the binder as well as the composition of the mixture, i.e., the grading curve. As we used polyurethane binders within our mixtures, which have a low dependency on regular environmental temperatures after their complete chemical reaction, we can imply a low temperature dependence of the entire polyurethane asphalt mixture. Based on these results, the construction of a noise-reducing and durable road layer is a great solution. The application of such road layers leads to lower traffic emissions at major hotspots. These might be urban highways, where the infrastructure is too tight to build noise barriers, enclosures or tunnels.