Steel slag as valuable aggregate in eco–friendly mixtures for asphalt pavements

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 this sense, the possible use of steel slags for construction applications (including road pavements) has a strategic importance to convert a waste into a valuable resource, taking also into account that ferrous slag may have a lower potential to negatively impact the environment. The environmental sustainability of asphalt mixtures prepared with steel slags can be further enhanced adopting the so-called Warm Mix Asphalt (WMA) technology. In fact, WMA is an asphalt concrete modified with additives that can be produced and applied at lower temperatures than the traditional Hot Mix Asphalt (HMA), thus reducing energy consumption, gas and fume emissions. Given this background, the paper illustrates a part of a wide research study aimed at verifying the utilization feasibility of steel slags in warm asphalt concretes. In particular, midrange and high-service temperature properties as well as water susceptibility of warm mixtures containing steel slags were assessed in the laboratory. The warm modification was performed using a chemical tensoactive additive, whereas slags were taken from a metallurgical plant equipped with an electric arc furnace (EAF). A WMA prepared with only natural aggregates was also studied for comparison purpose. The performance characterization was carried out through both static and cyclic laboratory tests. The results mainly showed that asphalt mixtures prepared combining chemical warm technology and EAF steel slag aggregates demonstrate promising field applicability.