Warm-Mix Asphalt Containing Reclaimed Asphalt Pavement: A Case Study in Switzerland

Abstract

Among the technologies proposed for achieving carbon neutralization in asphalt road pavements, warm-mix asphalt (WMA) has garnered increasing attention in recent years. While WMA holds the potential for various environmental and technical benefits, a comprehensive understanding of its implementation, technology selection, and additives is essential for successful application. This study presents a case where a bio-based chemical additive was employed to produce WMA containing 50% reclaimed asphalt pavement (RAP) for a surface course in Bern, Switzerland. To minimize additional variables during testing and analysis, no other additive or rejuvenator was introduced into the mixtures. The testing plan encompassed laboratory tests on samples collected during material placement and recompacted at varying temperatures in the laboratory, as well as cores extracted from the job site. As anticipated, the presence of the chemical WMA additive did not alter the rheological properties of the reference bitumen. Although in the mixture-scale tests, the WMA mixture exhibited comparable properties to the control hot-mix asphalt (HMA), it is not expected that the small dosage of the chemical additive functions the same grade after reheating and compaction. Nevertheless, the cores extracted from the job site proved the efficiency of the applied WMA technology. In addition, consistent with existing literature, the cracking tolerance (CT) index values of 62 for HMA and 114 and 104.9 for WMA mixtures indicated that the latter is less susceptible to cracking. Consequently, this characteristic could contribute to the enhanced durability of asphalt pavements.