USE OF TIRE CHIP/SOIL MIXTURES TO LIMIT FROST HEAVE AND PAVEMENT DAMAGE OF PAVED ROADS

This study consisted of two parts: (1) laboratory measurement of the thermal conductivity and permeability of tire chips and mixtures of tire chips and soil; and (2) constructing a field trial to investigate the use of tire chips to reduce frost penetration and improve drainage beneath paved roads. In the laboratory study, the samples were compressed under surcharges up to 18 kPa. Five types of tire chips, six tire chip/gravel mixtures, and one gravel sample were tested. The apparent thermal conductivity (K) of steel belted tire chips decreased from 0.32 to 0.20 W/m. degrees C as the density increased. The K of glass belted tire chips was slightly lower. The effect of moisture was small, increasing K by between 0.01 and 0.05 W/m. degrees C. K increased as the temperature gradient increased. The K of mixtures increased as the gravel content increased. The measured K of tire chips was very close to the value backcalculated from a field trial constructed in Richmond, Maine. The permeability of tire chips ranged from 26.3 cm/s for an uncompressed sample to 6.5 cm/s for a compressed sample. The permeability of mixtures decreased significantly as gravel content increased. The NETC field trial showed that tire chips reduced frost penetration by up to 47% and frost heave was reduced by up to 74%. The values of K measured in the laboratory were slightly higher than those backcalculated from the NETC field trial. Pavement performance measurements showed that 330 mm of soil cover over the tire chip layer would lead to premature cracking but that 483 mm of soil cover could be used with only a small effect on pavement life.