Environmental Benefits of Cold-in-Place Recycling

The United States uses approximately 1.3 billion tons of aggregate every year, 58% of which is for road construction. Furthermore, 90% of aggregate used in road construction is virgin aggregate. With the increasing cost of virgin material sand the growing pressure to build more sustainably, the use of recycled materials in roads is becoming increasingly widespread. The triple bottom line of sustainability requires that a project is economically, socially, and environmentally beneficial relative to conventional methods. Cold-in-In-Place Recycling (CIR) is a method for highway resurfacing that has become more widely used in the past decade for its demonstrated benefits to the triple bottom line.

The project objective was to quantify the environmental life cycle benefits associated with using Cold-in-Place Recycling (CIR) for highway resurfacing instead of the conventional Mill and Overlay process. Equipment used and the quantity of materials used for both the CIR process and what would have been used in the Mill and Overlay process for the same project were collected for nine highway projects in Wisconsin. With this information, a life cycle assessment (LCA) tool, Pavement Life-cycle Assessment tool for Environment and Economic Effects (PaLATE) was used to analyze and compare each project’s data.

More information may be found in the following file:

Environmental Benefits of CIR TRB Report


Chemical Characterization of Leachate Produced from RCA

The proposed NPDES regulations in the State of Washington, requiring a pH below 8.5 at the point of discharge from recycled concrete aggregate (RCA), may have the unintended consequence of prohibiting the use of recycled concrete materials in commonly accepted concrete recycling applications; e.g., as unbound base course or fill material or aggregate in ready-mix concrete. A more appropriate method to determine compliance with pH regulations would be to determine a “point of compliance” and enforce pH regulations at that point. However, selection of an appropriate point of compliance is hindered by disagreement in previous studies on the pH of leachate as well as its acid neutralizing capacity (alkalinity). Most laboratory studies and many field studies suggest that the leachate pH should be very high (e.g., >9) for extended periods of time; however, the NAICS data presented in Figure 1 and results of our own field studies (Chen et al., 2012; Chen et al., 2013) suggest that leachate pH values above 8.5 are actually infrequent.   Here we propose to couple laboratory leaching studies, utilizing representative saturation and geochemical conditions, with results from a forensic examination of an RCA base course located at the MnROAD test facility to determine mechanisms that may limit the production of high pH of leachate.

For more information:

RMRC Proposal – RCA Leachate pH