Estimating the thermal conductivity of asphalt binders

Nowadays, there is a common worldwide interest in environmental issues and pavements. How to save energy and mitigate the urban heat island (UHI) effect are topics that are drawing the attention of different researches and industrial organizations. In road infrastructure, one of the important properties addressing environmental and UHI aspects of pavements is the determination of the thermal conductivity. Asphalt concrete represents the third most widely used resource in the world, with asphalt-paved roads being its principal usage. One of the most important components of asphalt concrete is bitumen. Bitumen is a viscoelastic material susceptible to temperature changes. The determination of the bitumen's thermal conductivity becomes very important in understanding and improving its thermal performance. There are very few test methods and equipment to measure thermal conductivity of bitumen (asphalt binders). Some are expensive and require special equipment and instrumentation. This study developed and validated a simplified testing technique to measure thermal conductivity of asphalt binders. This test is a steady state-based method to estimate the thermal conductivity of asphalt binders using cylindrical samples poured into a silicon mold. The method was validated using material of known thermal conductivity. A total of 18 samples of different binder grades were tested, and the test results were repeatable and within known thermal conductivity values. Sensitivity analysis and accuracy of the proposed method were validated modifying the asphalt binder with a material with a very low thermal conductivity. This method to estimate thermal conductivity of bitumen samples was found to provide an affordable alternative test procedure with good accuracy and precision.