Analysis of thermal conductivity of porous concrete using laboratory measurements and microstructure models

Abstract

Porous concrete pavement has been used to alleviate urban heat island (UHI) effect in the near-surface temperature field. Due to high porosity and heterogeneity, thermal properties of porous concrete may vary depending on the microstructure of aggregates and air voids. This paper developed an innovative method to calculate the effective thermal conductivity of porous concrete considering two-dimensional (2-D) heterogeneous microstructure. An image-aided approach was used to randomly generate the three-phase (aggregates, cement paste, and air) microstructure model of porous concrete. Finite-element (FE) models were developed to calculate thermal conductivity of porous concrete by simulating the steady heat transfer process. Laboratory experiments were conducted to measure thermal conductivity of porous concrete and its components. The prediction results were compared to experimental measurements and close agreements without statistical differences were observed. The effects of microstructure feature on thermal conductivity of porous concrete were studied. Although the thermal conductivity of porous concrete decreases as the porosity increases in general, the variation of thermal conductivity is affected by the tortuosity and orientation of air void and aggregate contacts. The study findings clearly indicate that the heterogeneous microstructure of porous concrete need be considered for accurate prediction of thermal transport behavior.