Experimental and Numerical Investigations on an Organic Phase Change Material Incorporated Cool Concrete Pavement

Abstract

Traditionally, cool pavements have been designed as reflective pavements and evaporative pavements etc. Though the reflective pavements reduce the pavement surface temperature significantly, they increase glare, thermal burden on pedestrian traffic, and temperature of nearby buildings. In case of evaporative pavements, absence of water, reduced thermal inertia and solar reflection result in a higher pavement temperature. As a result, there has been a pressing need to investigate on new low side-effect cool pavement options. The aim of the study is to analyze the effect of phase change material (PCM) incorporation on the thermal performance of concrete pavements and to develop a total enthalpy-based numerical heat transfer model for such cool pavements. A paraffin-based organic PCM with a melting point of 42 to 45 °C was used in this work and expanded clay aggregate (ECA) was used as encapsulation medium. Concrete slabs without and with incorporation of PCM impregnated ECAs were cast and thermocouples were implanted in the concrete to monitor the pavement temperature continuously. A total enthalpy-based numerical heat transfer model was developed to predict the thermal performance of such cool concrete pavements. The PCM incorporation resulted in a reduction of 2.24 °C in the annual average pavement surface temperature with a maximum reduction of 4.12 °C. PCM incorporation is an effective method to reduce pavement surface temperature during daytime making the pavements cooler. Increasing the porosity of the encapsulating medium and also increasing the thermal conductivity of the concrete slab enhances the cooling potential. However, the thermal characteristics of the encapsulating material may be neglected as their impact is less on the cooling potential.