A review of design methods for cold in-place recycling asphalt mixtures: Design processes, key parameters, and evaluation

The use of cold in-place recycling (CIR) asphalt mixtures is a time-saving and environmentally-friendly technique for repairing aging and damaged asphalt pavements. The technique requires that a section of the layers that form the asphalt pavement is pulverized, mixed with a recycling agent, and repaved in place. This procedure offers the advantages of reducing greenhouse gas emissions and recycling pavement materials. Globally, a diversity of design methods for guiding cold in-place asphalt mixtures exists. Many of the methods are improvements on the design methods associated with hot mix asphalt mixtures. A universally recognized and accepted method is yet to be established, which inhibits the development of CIR. As a result, recycled asphalt pavement (RAP) has not yet reached adoption levels of 100%, and the performance of new pavements cannot be guaranteed. We present a detailed review of the major existing methods and analyze their prominent features, including their associated raw materials, design processes, and key control parameters. We compare various methods and conclude with a comprehensive summary. The content of this review provides valuable suggestions to contractors and researchers, with respect to the selection of design methods and the application of recycled aggregate. Finally, we propose pertinent topics for future study, based on the shortcomings of existing methods and the current state of the art.