Life cycle assessment of low temperature asphalt mixtures for road pavement surfaces: A comparative analysis

The increasing fuel consumption demand, the accelerated pressure imposed by the depletion of 5 scarce raw materials and the urgent environmental protection requirements are forcing the change of 6 pavement industry and academia community’s research endeavors towards the development of low 7 emissions road paving technologies able to significantly reduce mixing and compaction temperature as 8 well as the consumption of virgin raw materials. One set of relatively recent technologies in the field of 9 pavement materials that aims at addressing those concerns are the warm mix asphalt (WMA). In fact, 10 they have the potential to allow the reduction of energy consumption and airborne emissions during 11 their production and placement. Moreover, the incorporation of reclaimed asphalt pavement (RAP) in 12 these mixtures may further improve their potential environmental sustainability, both by reducing the 13 consumption of virgin raw materials, and by reducing the stockpiles and landfills of milled materials. 14 Which of these sustainable practices is greener and whether combining them is promising as it sounds, 15 it’s still not actually too well demonstrated in literature. 16 It’s within this context that this study presents a full process-based comparative life cycle 17 assessment (LCA) looking at understanding the environmental impact of reducing mixing temperature 18 , through the use of warm mix technologies, namely chemical additives-based and foamed-based, and 19 different rate of recycling (0% and 50% RAP). Furthermore, the investigation explores the effect of 20 combining the effects in the construction, maintenance and rehabilitation (M&R) of wearing courses 21 for flexible road pavements. The analysis assessed the functional units over a 30-year project analysis 22 period (PAP), considering all pavement life cycle phases: extraction of raw materials and production; 23 transportation of materials; construction, maintenance and rehabilitation; work zone traffic 24 management; usage and end-of-life. The results of this study showed that, for the conditions considered 25 and assumptions performed, a pavement construction and M&R scenario in which a foamed-based 26 WMA mixture with a RAP content of 50% is employed in the wearing course throughout the pavement 27 life cycle is the most environmentally friendly alternative among all the competing solutions. Moreover, 28 the results of a scenario analysis showed that the life cycle environmental impacts could be reduced if 29 the asphalt plant was fueled by natural gas, or if the pavement structure was dismantled at the end of its 30 lifetime and the debris recycled.