Geothermal Pavements: Experimental Testing, Prototype Testing, and Numerical Analysis of Recycled Demolition Wastes

Abstract

Geothermal pavements have the potential to reduce the pavement surface temperature by circulating fluid in pipes within the pavement structure. This research investigated an innovative geothermal pavement system with multiple benefits, such as reducing the surface temperature and harvesting heat energy for power generation. This research aimed to provide an understanding of the mechanical properties of geothermal pavements constructed with construction and demolition (C&D) waste materials through large-scale physical testing, experimental testing, small-scale prototype testing, and numerical simulation. The mechanical properties of the geothermal pavement system were assessed under long-term traffic loading conditions using a prototype test system. The repeated load triaxial and repeated-load California bearing ratio tests were also undertaken to evaluate the effect of pipe inclusion on the permanent deformation, stiffness, and strength of the pavement base. A numerical model was subsequently developed and calibrated using the data from small-scale prototype testing. In addition, the effects of the flow rate and pipe materials on the thermal performances of the geothermal pavements were also investigated in this research. The inclusion of pipes in the pavement base layer was found to have negligible detrimental effects on the deformation behavior of RCA. The resilient moduli of recycled concrete aggregate (RCA) samples slightly decreased with the inclusion of pipes. An HDPE pipe reduced the stiffness of the RCA + HDPE mix. On the other hand, a copper pipe’s high stiffness improved the mix’s strength. The numerical simulations indicated that for the HDPE pipe, increasing the flow rate from 500 mL/min to 2000 mL/min reduced the surface temperature by approximately 1.3%, while using the copper pipe resulted in an approximately 4% further decrease in the surface temperature compared to the HDPE pipe.