Unsaturated hydraulic properties of recycled concrete aggregates blended with autoclaved aerated concrete grains for unbound road base materials in Vietnam

Understanding of hydraulic properties is necessary to evaluate the water infiltration and balance in a road course. An easily available hydraulic model can contribute to the design of urban flooding countermeasures and mitigation of urban heat islands by covering roads with pavements. Many studies have evaluated saturated hydraulic conductivity, but few studies of measurements and modeling of unsaturated hydraulic properties such as water retention and unsaturated hydraulic conductivity for roadbase materials have been done. Therefore, this study measured the unsaturated hydraulic properties of typical roadbase materials of recycled concrete aggregates (RCA) using an evaporation method in the laboratory. To improve the water retention capacity, RCA blended with autoclaved aerated concrete (AAC) grains were also used. The results showed that the Gardner–Campbell (GC) model described the hydraulic properties of tested roadbed materials well, and the inclusion of AAC grains increased the water-holding capacity effectively. As a case study, the GC model was incorporated into the Green–Ampt infiltration model to simulate the change in the infiltration rate over time. The simulated results analyzed the water infiltration characteristics well, and this approach would be a good tool to make a quick assessment of the infiltration process of roadbed materials.