Investigation of thermal conductivity and prediction model of recycled tire rubber-sand mixtures as lightweight backfill

Abstract

Thermal conductivity is an important parameter in investigating the thermal properties of geotechnical materials. In this paper, a series of thermal needle tests were carried out on recycled rubber-sand mixtures. The effects of sand fraction, moisture content, dry density, and particle size on thermal conductivity were investigated in detail. The results showed that the thermal conductivity of rubber-sand mixtures was observed to be a parabolic increment at a low sand fraction and a linear increment at a high sand fraction with an increasing dry density. A value of 6% can be regarded as critical moisture content. The larger the sand particle size, the higher the thermal conductivity exhibited by the mixtures was. Additionally, based on a scanning electron microscopy (SEM), the heat transfer mechanism was investigated. Importantly, a simplified multiple linear regression (MLR) model for recycled tire rubber-sand mixtures was proposed, and significant test (correlation coefficient R2, F-test, and t-test) results presented a good regression effect for this model. This research will provide a more reasonable thermal parameter for recycled tire rubber-sand mixtures as a lightweight backfill in geothermally-related structures. Moreover, the effective utilization of scrap tires can reduce environmental pollution and promote sustainable infrastructure.