Laboratory Design of Quieter Asphalt Surfaces

Recently, increased concern about the influence of highways traffic noise in health and its negative financial effects has highlighted the need to design quieter pavement surfaces. This study evaluates different factors affecting noise generation properties in asphalt surfaces. Special attention was paid to the macrotexture influence in noise. The results of the statistical analysis of the noise data collected suggest that to reduce noise, the design should focus more on producing mixtures with reduced macrotexture. Adjusting the gradation of the mixture may have a significant positive effect on noise reduction, although, friction may be negatively affected. A laboratory noise test was implemented in order to assess the noise sensitivity of a determined mix to variation in gradation and asphalt binder content. This allows the laboratory design of quieter pavement surfaces. With the test implemented it was possible to accurately measure noise in different types of surfaces and provide a repeatable and standard procedure that can use laboratory compacted samples and field cores, which allows further field validation. Based on the results, it was found that thin overlay mixtures (TOM) produce a low noise surface. In contrast to porous friction course (PFC), a well-known low noise surface, the noise design of TOM is not overly sensitive to variations in aggregate gradation or asphalt content. Indications are that PFC mixtures do not maintain their porosity over time owing to clogging and this significantly deteriorates the noise attenuating properties of these mixtures. Conversely, TOM tend to maintain the attenuating properties over time.