Traffic noise is a major setback to the life quality of residents living in the vicinity of highways. Over the past 40 years, much legislation has been passed to regulate the sound level with which residents are exposed to around the country. Among the many approaches adopted to alleviate the problem, crumb rubber modified asphalt has been proposed as a measure to reduce highway traffic noise. This research investigates the effects of crumb rubber particles on the ability of an asphalt pavement to absorb noise. Several types of mixtures were evaluated with and without the presence of crumb rubber with air void contents of 3.5%±0.5% and 16%±0.5% for dense and porous mixes, respectively. The effects of crumb rubber concentration and gradation were evaluated to better understand the factors that affect the sound absorption of mixtures. The results indicated that the effect of crumb rubber as an energy absorbent (damping) material is minimal and does not significantly increase the sound absorption. However, the presence of crumb rubber particles affected the volumetric properties of the mixtures,which consequently affected the sound absorption. In summary, crumb rubber was not shown to directly affect sound absorption, but it did indirectlyaffect it through other changes in mixtures properties such as permeability and binder content.
Abstract