Optimizing Rubberized Open-graded Friction Course (RHMA-O) Mix Designs for Water Quality Benefits: Phase I: Literature Review

Historically, rubberized and non-rubberized open-graded friction courses (OGFCs) have been placed to provide three benefits: to increase traffic safety, to reduce urban highway noise, and to preserve the surface of the main pavement structural section. However, stringent environmental regulations on stormwater runoff management enacted recently have forced transportation agencies with limited right of ways in urban areas to search for creative methods to treat runoff and receive credits for preventing pollution from highways. This literature review was undertaken to explore ways to optimize current RHMA-O mix designs to provide multifunctional benefits, including water quality treatment. The literature review showed that permeability measurement is an essential parameter that influences a wide range of OG (both rubberized and non-rubberized) pavements’ performance. Further, current Caltrans aggregate gradations contain a larger fraction of fine aggregate sizes and this may also influence the permeability and functional performance of RHMA-O pavements. Part of this literature review includes an action plan recommending that the next phase of this work include optimizing current Caltrans mix designs and the mix design procedure in the laboratory and undertaking subsequent field investigations.