Hydraulic Properties of Recycled Asphalt Pavement and Recycled Concrete Aggregate

摘要

The saturated hydraulic conductivity (k_(sat)) and water characteristic curves (WCCs) of three recycled asphalt pavements (RAPs) and three recycled concrete aggregates (RCAs) were measured. The k_(sat) was determined using a constant-head, rigid-wall, 152-mm-diameter permeameter. The specimens were prepared at 95% of maximum dry density based on modified Proctor testing. The k_(sat) of the RAPs varied from 3.8×10~(-5) to 3.7×10~(-4) m/s and from 1.6×10~(-5)to 2.6×10~(-5) m/s for the RCAs. Hazen's equation (1911) tends to over predict ksat for RAPs and RCAs. Hanging columns with large-scale testing cells (305-mm inner diameter and 76-mm height) fitted with air aspirators were used to determine the WCCs. The WCC of each recycled material was fitted using the Fredlund and Xing (1994) model because this model is used in the Mechanistic-Empirical Pavement Design Guide (MEPDG). A hanging column test can measure suction lower than 1 kPa with high accuracy (+0.02 kPa). The slopes of the WCCs of RAPs were steeper than those of RCAs, although RAPs have higher densities. Compared to Rahardjo et al. (2010), RAPs and RCAs used in this study provided higher air entry suction because the specimens were prepared at higher, compacted density to replicate field conditions. To develop a WCC for RAPs and RCAs over a larger range of suctions, a device such as a pressure plate extractor is recommended.