Development of a microstructure-based numerical approach for analyzing heat transfer within the asphalt mixture

Computed Tomography technique has been commonly used to obtain the geometric model of asphalt mixture for the microstructure-based heat transfer numerical analysis. However, this technique relies on expansive equipment and has shortcomings related to limited sample size and difficulty in identifying the boundary of stones. This study proposes a cost and time-effective numerical method to compute the heat transfer within asphalt mixture from the microstructure point of view. The computer graphics technique is adopted to develop the geometric model of asphalt mixture, including coarse stones and asphalt matrix. The generated geometric model is imported into the finite element software to compute the thermal conductivity and specific heat capacity of asphalt mixture. To obtain input parameters of the newly developed numerical method, the thermal conductivity and specific heat capacity of coarse stones and asphalt matrix are measured through the heat plate exchanger. The above two parameters of asphalt mixture are also measured to verify the computed results by the newly developed numerical method. The differences between computed and measured thermal conductivity and specific heat capacity of asphalt mixture are 9.0% and 8.6% respectively, indicating a good performance of the newly proposed microstructure-based numerical approach. On the other hand, computed results show that asphalt mixtures with different sample sizes and aggregate size distributions have non-uniform distributions of heat flux and temperature, mainly due to the different thermo-physical properties between coarse stone and asphalt matrix. For asphalt mixtures, a knowledge of heat flux and temperature fluctuations from the microstructure point of view may shed light on the analysis of stress/strain distribution and crack propagation in asphalt mixture.