Road wearing layer type and age effect on pavement acoustic degradation

Long-term positive acoustic behavior as well as sufficient strength and durability is required for low noise road surfaces. However, combination of these properties in many cases is a challenging task, especially at the severe climate conditions. In such regions, optimized asphalt layers (SMA and AC) seem to be promising solution as they have similar structural conditions to traditional AC and SMA pavements but at the same time modified distribution of aggregates, increased air void content and optimized surface texture for noise reduction. Development of optimized surface layer asphalts in most cases relies on the good experience from different climate regions, however, acoustic degradation is different, faster than in milder regions. To analyze these effects, large number of road sections constructed of different asphalt mixtures (incl. low noise asphalt mixtures, traditional asphalt mixtures) and with different exploitation age were measured by Close Proximity (CPX) trailer. Collected noise level data was compared and linked with the pavement age, resulting acoustic degradation trends. After analyzing interrelations and similarities between traditional and optimized low noise asphalt surfaces and summarizing the results, recommendations for optimized low noise asphalt mixtures development are presented in the paper.