In continuation with the previous article on DURABROADS – Life Cycle Costing Analysis of Road System, this is the final paper to present the results obtained for the life cycle assessment and life cycle costing analysis of the DURABROADS asphalt mixes. BSRIA has been primarily involved in conducting the life cycle assessment (LCA) and life cycle costing (LCC) analysis of the potential new road layer mixtures formulated by the DURABROADS project partners to compare their environmental impacts and life cycle costs with the traditional materials. BSRIA presented the final results at the conference on – ‘Enhancing Research and Innovation in Europe: the Road Sector Experience’ held in Madrid on 12th September, 2017.
In the analysis, three pavement mixtures - AC (Asphalt Concrete), BBTM (Béton Bitumineux Mince), and PA (Porous Asphalt) were considered. A bitumen mixture for DURABROADS - referred as Durabroads Bitumen here - was designed to be used with all three cases, following which the overall mixtures were also modified with different additives such as evotherm, carbon black and SBS (Styrene Butadiene Styrene); and steel slag, basalt as aggregates. This analysis was carried out for six cases where the base case was the asphalt concrete road named AC Base. The other five pavement alternatives namely AC Alt, BBTM Base, BBTM Alt, PA Base and PA Alt were compared against the AC Base case to select the one that has the lowest environmental impacts and maximizes net savings. The functional unit that the study reports on is: “The impact assessment of a road cross- section of 7.4 m*1000 m (width*length) for a life cycle of 50 years”.
A lifecycle of 50 years has been chosen for the study because the service life of a typical well-maintained road subjected to high-traffic load is between 9-15 years before its surface layer is relayed and its average lifetime is 24 years before any major roadwork repair is done. Hence, a study period of 50 years would provide the optimum number of iterative cycles of road maintenance, surface relay and total road recycling across the lifecycle to generate well-informed, reliable results.This study has focused on a method in which the road construction, road maintenance and road relaying processes have been broken down into small process units. These process units have been used to build up a dynamic LCA and LCC model for each scenario.