Hydraulic conductivity-based optimum efficiency frontiers for RAP aggregate utilization in subbase construction

Abstract

• A design chart based on the frontiers is developed to achieve an efficient design. • The efficient design range of RAP replacement ratio was determined to be 25–35% • Hydraulic conductivity and bearing performance related frontiers are developed. • The efficient global optima is determined based on the design parameters. Reclaimed Asphalt Pavement (RAP) aggregate with or without cement stabilization is currently used worldwide as a virgin-aggregate replacement material in subbase construction. Paper presents the multiobjective efficiency analysis conducted on the experimental results from the extensive parametric study in order to identify how the level of hydraulic conductivity and the cement addition affect the RAP utilization. The optimum efficiency frontiers have been identified considering the dual optimization based on a set of multi-objective analyses using the Response Surface Method (RSM). The factors of RAP aggregate replacement range (0–100 %) and cement addition variation (0–4%) were considered along with the responses of hydraulic conductivity, compaction, CBR (California Bearing Ratio) and UCS (Unconfined Compressive Strength). Paper reveals that a specific replacement limit of 25–35% provides an efficient RAP aggregate utilization in terms of the considered parameters. It presents a practical design chart to attain an optimum control on the efficient utilization of RAP aggregate in subbase construction considering the levels of targeted hydraulic conductivity and other considered parameters.