Towards a durable and sustainable warm mix asphalt: techno-economic and environmental evaluation considering balanced mix design approach

Abstract

In response to the worldwide inclination towards sustainability and circular economy targets, there is a need to employ innovative and eco-friendly paving technologies. This research aims to investigate the mechanical performance (rutting and cracking resistance) and durability characteristics (resistance against moisture susceptibility) of long-term aged warm mix asphalt (WMA) mixtures containing reclaimed asphalt pavement (RAP), a WMA additive, an anti-stripping agent, and three chemically different recycling agents (RA) (an aromatic extract (A), a triglyceride/fatty acid (TF), and a tall oil (T)) through conducting the semi-circular bending (SCB) fracture, dynamic creep (DC), and indirect tensile strength (ITS) tests. Then, two-dimensional (2-D) and three-dimensional (3-D) performance interaction diagrams (PID) were used to identify asphalt mixtures with satisfactory performance in terms of moisture susceptibility, rutting failure, and fatigue cracking. Furthermore, an integrated environmental-economic comparison of the mixtures was conducted using a sustainability rating system developed by the authors. This system aims to identify cost-effective asphalt mix designs with lower CO2 equivalent emissions. The results of mechanical properties and Tukey’s honest significant difference (HSD) analysis indicated that the performance of RAP-blended mixtures is superior or equal to the performance of the mixtures without RAP when modified with RAs, WMA additive, and anti-stripping agent. Furthermore, the long-term aging performance of WMA mixtures containing RAP was significantly influenced by the RA' type. Results of economic and environmental analyses also indicated that virgin asphalt binder contributed the most to both cost burden and Greenhouse Gas (GHG) emissions, accounting for an average of 60% of the total cost and 45% of the total GHG emissions during the material and mixture production phase. Therefore, RAP recycling which decreases the need for virgin asphalt binder in addition to being replaced by a part of the required virgin aggregates is considered as one of the extremely environmentally friendly and cost-effective strategies. The environmental impacts of asphalt mixtures are significantly influenced by the choice of RAs, particularly when using a high RAP content. This study suggests that the utilization of tall oil and aromatic extract, as demonstrated, could be a better choice from an environmental perspective.