Characterization of Water Retention and Unsaturated Hydraulic Conductivity for Recycled Road-Base Materials

Abstract

Not only characterization of saturated hydraulic property but also unsaturated hydraulic properties such as water retention and unsaturated hydraulic conductivity are necessary to evaluate an accurate water movement process and the design of water drainage in the road pavement system. Till now, only limited data is available for the unsaturated hydraulic properties for unbound roadbed materials due to the difficulty of measurement. This study carried out the measurements of water retention capacity (WRC) and unsaturated hydraulic conductivity for recycled concrete aggregates (RCA) that typically used for the road base and subbase materials. After grading particle size distribution of RCA adjusted to Japanese technical specification, the tested sample was compacted in a cylindrical mould following the modified Proctor method and then used to measure WRCs and unsaturated hydraulic conductivity. The WRC was measured under the main drying process by a combinational technique with a hanging water, pressure chamber, and a dew-point potentiometer and the unsaturated hydraulic conductivity was measured by an evaporation method. Besides, Toyoura sand was used as a reference material. Results showed the graded RCA gave a smaller water retention capacity compared to Toyoura sand at saturation, however, its water retention became higher than Toyoura sand at the suction range exceeding 10 kPa. As well as water retention property, the saturated hydraulic conductivity of graded RCA became smaller than Toyoura sand at saturation, however, the measured unsaturated hydraulic conductivities of graded RCA at the suction range of 10–100 kPa ranged in the orders of 10^–6–10^–8 cm/s and became higher than those of Toyoura sand.