1. Research Assistant, Dept. of Civil and Environmental Engineering, Michigan Technological Univ., 1400 Townsend Dr., Houghton, MI 49931.
2. Donald and Rose Ann Tomasini Associate Professor, Transportation Engineering and Director of the Transportation Materials Research Center, Dept. of Civil and Environmental Engineering, Michigan Technological Univ., 1400 Townsend Dr., Houghton, MI 49931 (corresponding author).