Comprehensive performance characterization of warm mix asphalt containing steel slags: a laboratory study

Research and application concerning the use of environmentally friendly materials and technologies in road pavements have reached high relevance mainly due to the increasing public consciousness addressed to environmental protection and preservation. In regard to this, Warm Mix Asphalt (WMA) can be successfully used since it is an asphalt concrete modified with additives that can be compacted at lower temperatures than the traditional Hot Mix Asphalt (HMA). The environmental sustainability of WMA can be further enhanced thanks to the inclusion of recycled/waste materials. Given this background, the present paper illustrates the overall results of a wide research study aimed at verifying the utilization feasibility of steel slags in warm-modified asphalt concretes. This was accomplished by investigating in the laboratory the midrange and high-service temperature properties of warm bituminous binders, as well as mastics and mixtures containing steel slag aggregates. The warm modification was performed using a chemical tensioactive additive; steel slags were produced in a metallurgical plant by electric arc furnace (EAF) treatment. To evaluate the combined effect of manufactured EAF steel slags and warm chemical additive, a comparative analysis was carried out taking into account unmodified binders as well as mastics and mixtures prepared with only natural aggregates. The rheological study on unaged and long-term aged binders and mastics was performed with the dynamic shear rheometer (DSR), whereas cyclic tests on WMA mixes were conducted with the Nottingham Asphalt Tester (NAT). The results mainly showed that materials prepared combining chemical warm technology and EAF steel slag aggregates seem to assure equal or even enhanced performance than the corresponding traditional hot mixed materials, demonstrating promising field applicability.