Thermal Conductivity of Sand–Tire Shred Mixtures

Sand–tire shred mixtures are useful as thermal backfills due to their lower unit weight and thermal conductivity than those of most soils. In this study, a series of thermal conductivity tests on sand–tire shred mixtures and pure sand were performed to investigate the effects of volumetric mixing ratio and tire shred particle size. A volumetric mixing ratio of 40% was found to yield the greatest decrease in thermal conductivity from that of pure sand, with a maximum percentage difference of 72%. Using tire shreds with a larger relative size ratio was found to result in higher thermal conductivity, and the maximum variation in the thermal conductivity percentage difference with the relative size ratio reached about 20% at a volumetric mixing ratio of 40%. An empirical model proposed to predict of the thermal conductivity of quartz sand–tire shred mixtures captured trends in the experimental data.