Field Trial of Tire Shreds as Insulation for Paved Roads

摘要

This paper discusses the use of tire shreds and tire shred/soil mixtures to improve the performance of paved roads in seasonally cold regions. Tire shreds and tire shred/soil mixtures accomplish this by acting as an insulating layer and free-draining subbase. In addition, this application could use approximately 370,000 tires per kilometer (585,000 tires per mile) for a typical two-lane highway. This paper describes the construction of a field trial in Orono, Maine using tire shreds and tire shred/soil mixtures as insulation and a high permeability subbase as well as the performance of the field trial through the winter of 1996-97. The field trial incorporated 152-mm (6-in.) to 305-mm (12-in.) thick layers of tire shreds or tire shred/soil mixtures overlain by 330 mm (13 in.) to 483 mm (19 in.) of gravel base. Tire shreds generally had a 76-mm (3-in.) maximum size. The field trial showed that tire shreds reduced frost penetration by up to 47 percent and reduced frost heave by up to 74 percent. A mixture of 67percent tire shreds/33percent soil reduced frost penetration by 23 percent and frost heave by 23 percent. A mixture of 33percent tire shreds/67percent soil reduced frost penetration and frost heave only marginally. The values of thermal conductivity (K) measured in a compansion laboratory study were slightly higher than those backcalculated from the field trial. The backcalculated values were about 0.17 W/m.deg C (0.10 Btu/hr.ft.deg F) for tire shreds to 0.21 W/m.deg C (0.12 Btu/hr.ft.deg F) for a mixture containing 67percent tire shreds/33percent soil to 0.54 W/m.deg C (0.31 Btu/hr.ft.deg F) for a mixture containing 33percent tire shreds/67percent soil. For comparison, a value of 1.60 W/m.deg C (0.94 Btu/hr.ft.deg F) was measured in the companion laboratory study for the gravel base used in this field trial. Pavement performance measurements showed that 330 mm (13 in.) of soil cover over a 305-mm (12-in.) tire shred layer would lead to premature cracking but that 483 mm (19 in.) of soil cover could be used with only a small effect on pavement life.