Sensitivity of the LCA allocation procedure for BFS recycled into pavement structures

The purpose of this paper is twofold: to investigate the problems involved when performing an environmental assessment of various pavements structures and to establish the method applied to solutions proposed by official French guidelines. This assessment will be performed by employing the life cycle assessment (LCA) methodology specifically adapted to road pavements through a parametric environmental evaluation tool developed by LCPC: ERM (elementary road modulus). The paper will also detail the assessment methodology using this same ERM method. The issues of resources conservation and waste allocation will be examined for the case of blast furnace slag (BFS) recycling. Special focus will be placed on the sensitivity of environmental indicators as regards to the waste allocation procedure implemented in the ERM. Two distinct mass ratios (0% and 20%) of steel production have been assigned to BFS and tested on indicators results as hypotheses H1 and H2, respectively. Classical indicators have been calculated using a simplified model to allocate output flows into several impact categories. Results show that the structure using BFS contributes to saving binder extracted from natural resources, yet also consumes a larger mass of natural aggregates. All indicators except for toxicity were found to be very sensitive to the choice of H1 or H2 hypotheses.