Improved environmental footprint & road durability using hydrated lime in hot mix asphalt
The evidence shows that adding hydrated lime to Hot Mix Asphalt (HMA) creates multiple benefits in the overall road performance (increased moisture sensitivity resistance, frost and rutting resistance, as well as an anti-aging agent for bitumen) and results in the extension of life span of asphalt pavements. A life cycle assessment (LCA) study comparing the environmental impact of the conventional Hot Mixed Asphalt (HMA) versus modified HMA (with 1.5% of hydrated lime) was carried out according to the ISO 14040-14044 standards and was validated by an external critical reviewer. The study shows that thanks to the use of hydrated lime in HMA the wearing course durability is extended by 25%, which leads to a decrease in the overall environmental footprint over the lifetime of a road (50 years) for all environmental impact categories.
If only road construction is considered, the conclusion would be that modified HMA has 19% higher GHG emissions compared to classical HMA. But once the full life cycle of the pavement is considered, with the improved durability also accounted for, then GHG are reduced by 23% in favour of modified HMA resulting in significant positive impacts. Therefore, it is very important that road pavements are evaluated over their whole life cycle if a holistic environmental picture is to be assessed. The modified HMA is the cheaper solution (by almost 30%) over 50 years. Moreover, it is worth reminding that each maintenance step avoided prevents the formation of traffic jams created by the maintenance works. This makes hydrated lime a sustainable and durable solution for better pavements. The conclusions of this study are in line with the recent EU initiatives on resource efficiency and sustainable construction, which require optimising the available financial and raw materials resources.
Life Cycle assessment (LCA); Hot Mix Asphalt (HMA); Road durability; Hydrated lime