Accumulated plastic strain of asphalt mixtures under freeze-thaw-load coupling: An experimental study based on the high-speed railway load characteristics

This study examined the dynamic behavior and evolutionary characteristics of accumulated plastic strain in the asphalt mixture reinforcement layer on the high-speed railway subgrade in seasonally frozen ground under cyclic loads imposed by high-speed trains. Cyclic loading tests were performed based on the load characteristics of high-speed railways using asphalt mixture samples modified by different methods, namely, co-modified with styrene-butadiene-styrene block copolymer (SBS)/rubber powder, modified by rubber powder alone (dry and wet methods), and unmodified (base asphalt mixture). The evolutionary law of accumulated plastic strain in the asphalt mixtures under freeze-thaw-load coupling was analyzed. Besides, judgment criteria for different morphologies of curves were defined based on the plastic shakedown theory for a varying number of freeze-thaw cycles (FTCs). Further, the computational model for the accumulated plastic strain of asphalt mixtures under actual service conditions was proposed. The results showed that at all dynamic stress levels (150, 100, and 50 kPa), the asphalt mixture co-modified with SBS/rubber powder consistently exhibited the best fatigue performance under FTCs. Compared with the unmodified asphalt mixture, the asphalt mixture co-modified with SBS/rubber powder exhibited a reduction in accumulated plastic strain of 37.1 %, 42.8 %, and 26.9 % at the three stress levels (150, 100, and 50 kPa), respectively, after 10 FTCs coupled with cyclic dynamic loading. Based on the plastic stability theory, plastic creep zoning was performed under freeze-thaw-load coupling conditions. Combined with the experimental data, an accumulated plastic strain prediction model incorporating FTC and load parameters was established, with a clear definition of each parameter’s physical meaning. The proposed model accurately described the plastic strain evolution trends in asphalt mixtures under freeze-thaw-load coupling. The results obtained are considered instrumental in improving the serviceability and durability of the asphalt mixture reinforcement layer on the high-speed railway subgrades in seasonally frozen ground. • According to the characteristics of high-speed railway, the law of cumulative plastic strain of asphalt mixture is revealed. • Under the coupled effects of FTCs and loading, the evolution law between pores, particles and skeletons is revealed. • Based on the plastic stability theory under FTC, the judgment criteria of different curve shapes are defined. • Based on the plastic shakedown theory under FTL coupling, the calculation model of plastic creep behavior partition.