Emulsion-Based Cold Central Plant Recycling as a Sustainable Pavement Rehabilitation Alternative: Discussions from Life Cycle Assessment

Abstract: Pavement rehabilitation remains a critical aspect of pavement engineering. The choice of which pavement rehabilitation technique to adopt for a particular project is oftentimes not trivial. Traditionally, factors such as economic cost, and expected service life are key to choice making. Mill and fill with conventional Hot Mix Asphalt (HMA) is a commonly adopted technique for rehabilitating asphalt pavements. With concerns for environmental impact becoming more prevalent in the asphalt pavement industry, there is a great need for more environmentally sustainable alternatives to the typical HMA mill and fill for pavement rehabilitation. Emulsion-based Cold Central Plant Recycling (CCPR) is a technique that has been hypothesized to present this opportunity due to its ability to use 100% recycled materials and produce asphalt mixes cold. A recent study at Oklahoma State University used Life Cycle Assessment (LCA) to test this hypothesis. A comparative LCA study was carried out to compare the environmental impacts of a typical HMA mill and fill operation to those of emulsion-based CCPR. As CCPR is oftentimes complemented with an HMA overlay as its wearing course, the LCA study also investigated the environmental benefits that could be obtained from replacing an HMA overlay of CCPR with a Warm Mix Asphalt (WMA) overlay. Cradle-to-laid analysis was carried out for the LCA study. From the results, CCPR with HMA overlay was found to have much lower Global Warming Potential (GWP) compared to typical HMA mill-and-fill. Replacement of the HMA overlay on the CCPR layer with WMA was found to further reduce the GWP.