Performance of Drained and Undrained Flexible Pavement Structures in Accelerated Loading Under Wet Conditions – Summary Report Goal 5 Partnered Pavement Performance Program

The California Department of Transportation (Caltrans) requires that all new flexible pavements include a 75-mm layer of asphalt treated permeable base (ATPB) between the asphalt concrete and the aggregate base layers. The purpose of the ATPB layer is to intercept water entering the pavement because of high permeability resulting from insufficient compaction or through cracks in the asphalt concrete layer and transport it away from the pavement before it reaches the unbound materials.This reports summarizes the results of a study using Heavy Vehicle Simulator (HVS) trafficking to evaluate the performance of drained and undrained flexible pavements under wet (saturated base) conditions. A drained structure is a pavement section that contains an ATPB layer between the asphalt concrete and the aggregate base. An undrained structure is a pavement section that does not contain an ATPB layer. Wet conditions used in this study were intended to simulate approximate surface infiltration rates for a badly cracked asphalt concrete layer that would occur along the northwest coast of California during a wet month.