Mechanical and Performance-related Properties of Asphalt Mixes Containing Expanded Clay Aggregate

The use of artificial aggregates such as expanded clay in the production of asphalt concrete makes it possible to reduce both natural aggregate extraction and the use of non-renewable raw resources, giving considerable environmental benefits. Moreover, the expanded clay production process allows non-dangerous waste materials to be reclaimed, thereby avoiding disposal as landfill or dumping, with consequent environmental and economic advantages. This paper reports on the results of laboratory and in situ tests carried out to evaluate the feasibility and advantages of using expanded clay in producing asphalt mixes for use in urban areas with the aim of reducing traffic noise. Some experimental low noise asphalt surfaces were laid, using 15 % of expanded clay by weight, and mechanical as well as performance properties were evaluated. The mechanical characteristics, friction and acoustic performance obtained, in comparison to results with traditional asphalt surfaces, showed that considerable benefits derive from use of expanded clay in asphalt mixes for surface layers. In particular, interesting results in terms of friction increase and noise spectrum reduction were observed.