Performance of Recycled Materials in Pavement Subbase After 4 Years in a Hot Desert Climate

The paper presents a field investigation on the use of alternative subbase materials from excavation and demolition waste in subbase applications in a desert area. A road trial was constructed with three subbase sections, comprising excavation waste (EW) and crushed concrete aggregate (RCA) plus a control section of EW with 20% dune sand (control). Visual inspection after 4 years in service revealed excellent performance with no surface defects or obvious differences between the different sections. The subbase surface was exposed and field-testing using lightweight deflectometer indicated very similar values for the unbound subbases of EW and the control section. The RCA subbase exhibited excellent performance due to self-hardening, providing much higher stiffness than the unbound subbases. The extracted unbound subbase materials satisfied the physical and mechanical requirements of the Qatar Construction Specifications with the exception of liquid limit, plastic limit, and sand equivalent, which are of less significance where the material is placed above the water table. The paper demonstrates that recycled aggregate can perform as well as conventional subbase materials and promotes their wider use to support sustainable development. Key words: alternative aggregates, construction & demolition waste, excavation waste, field investigation, natural resources