Published Online: 25 July 2008
Page Count: 8
Construction Engineer, Alberta Transportation, Stony Plain, AB
P. Eng., Associate Professor, Dept. of Civil Engineering, Univ. of New Brunswick, Fredericton, NB
(Received 7 February 2008; accepted 3 June 2008)
Lightweight aggregate (LWA) asphalt mix has been found to have lower thermal conductivity and thermal diffusivity compared to a conventional asphalt mix. Given these beneficial thermal properties, a LWA-asphalt mix can reduce frost penetration into the underlying pavement layers. It is therefore postulated that the LWA-asphalt mix can reduce damage associated with frost heave. This paper investigates the effects of binder grade and coarse aggregate content on the thermal properties of LWA-asphalt mixes. The effects of three asphalt binder grades (PG58-28, PG64-28, and PG70-28) and three aggregate gradations were investigated. The thermal conductivity was found to vary from 0.77 to 0.87 W/m°K for the LWA-asphalt mixes having bulk density in the range of 1585–1653 kg/m3 and air voids 3.5–4.5 %. Thermal diffusivity was determined to vary from 2.1 × 10−7 m2/s to 2.6 × 10−7 m2/s and a standard deviation of 0.18 × 10−7 m2/s. Specific heat capacity was found to be in the range of 1990 J/kg⋅°K to 2360 J/kg⋅°K, with a standard deviation of 130 J/kg⋅°K. Coefficients of variation for thermal conductivity, thermal diffusivity, and specific heat capacity were found to be 3.2, 6.1, and 7.6 %, respectively. These results show that the three thermal response variables vary in a very narrow range. It is concluded that the beneficial thermal properties of LWA-asphalt mixes appear to be insensitive to variation in asphalt binder grade and aggregate gradation.
Paper ID: JTE101687