Thermal performance of geothermal pavements constructed with demolition wastes

This paper investigates the potential of harvesting heat energy from geothermal pavements constructed with construction and demolition (C&D) waste materials, by using experimental and numerical methods. The deformation, stiffness, and shear strength properties of two types of C&D materials used for the construction of geothermal pavements, namely crushed brick (CB) and recycled concrete aggregate (RCA), were evaluated by performing repeated load triaxial (RLT) and quick shear tests. A multistage RLT test was adopted to investigate the deformation behavior of CB and RCA over a wide range of stress levels. The stiffness of materials was evaluated in different stress combinations. A small-scale prototype pavement system with a serpentine-shaped copper pipe was placed in the C&D base layer for evaluating the potential of heat energy extraction. Comparisons were made between the performance of CB and RCA for construction of geothermal pavements. RCA was found to be considerably superior to CB in terms of strength and deformation properties. On the other hand, the geothermal pavement constructed with CB was found to have slightly more favorable thermal performance due to the higher thermal conductivity of CB compared to RCA. A numerical model was developed and validated based on the experimental results to investigate the effect of design parameters on the thermal performance of the geothermal pavements. The effect of base layer thermal conductivity, Reynolds number, solar irradiance, inlet water temperature, and pipe embedment depth, was investigated on the surface temperature reduction and heat gain of the system. Overall, the construction of geothermal pavement with C&D materials was found to be a feasible approach which further enhances the environmental sustainability of the system. (C) 2021 Elsevier Ltd. All rights reserved.