1. Research Assistant, National Engineering Laboratory of Highway Maintenance Technology, Changsha Univ. of Science and Technology, Hunan 410004, PR China.
2. Professor, National Engineering Laboratory of Highway Maintenance Technology, Changsha Univ. of Science and Technology, Hunan 410004, PR China (corresponding author).
3. Research Assistant, Dept. of Civil and Environmental Engineering, Michigan Technological Univ., 1400 Townsend Dr., Houghton, MI 49931-1295.