Effect of asphalt mixture gradation characteristics on long-term skid resistance under high temperature and heavy load.

Inadequate skid resistance (SR) performance will increase the risk and grade of traffic accidents. The structural stability related to the gradation may substantially affect the long-term skid resistance under the condition of high temperature and heavy load. This study characterized the mixture stability by coarse aggregate ratio (CA), coarse portion of fine aggregate (FA c), and fine portion of fine aggregate (FA f) in the Bailey method and the primary control sieve index and described the gradation integrity by Generalized Sigmodal model with five parameters. The 1/3 scale model mobile load simulator MMLS was used to simulate the unidirectional repeated heavy vehicle load at 60℃, then the effects of mixture gradation on the mean profile depth (MPD), texture level (L tx,0.5–20 mm), and evolution of friction coefficients were investigated. The evolution was explained from the perspective of mixture microstructure. It is found that although the gradation has little effect on the long-term friction measured by British Pendulum tester, the stronger skeleton formed by gradation can reduce the reduction ratio of the roughness and friction and has a significant positive effect on the long-term F 60 values. In addition, the Generalized Sigmodal model parameters for gradation are closely related to long-term skid resistance. The changing orientation and crushing of top layer aggregates causes the evolution of pavement roughness and friction under high temperature and heavy load conditions. This study will help actively intervene the SR performance of pavement during the mixture design to ensure driving safety during road service time. • The integrity and stability of gradation correlate with skid resistance. • Stronger aggregate skeleton reduces surface roughness and friction loss. • The rotation of aggregates and its breaking result in the friction evolution. • Generalized Sigmodal model fit the 0.45-power gradation curve well. [ABSTRACT FROM AUTHOR]