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.