Performance Evolution and Damage Constitutive Model of Thin Layer SCC under the Coupling Effect of Freeze–Thaw Cycles and Load

Self-compacting concrete (SCC) is widely used in the China Rail Track System (CRTS) III slab ballastless track filling-layer structure for high-speed railways (HSRs). In cold regions, the thin filling-layer SCC is subjected to the coupling effects of freeze–thaw cycles and load, shortening the service life of the track structure. This study focused on the performance evolution and damage constitutive model of thin flat plate SCC under the coupling effects of freeze–thaw cycles and load using a self-designed preloading device. Results showed that the increase of freeze–thaw cycles reduced the performance of SCC gradually. When SCC was exposed to 300 freeze–thaw cycles, the mass loss rate was 2.41%, peak stress (${\sigma }_p$) decreased by 23.1%, peak strain (${\epsilon }_p$) increased by 67.9%, and relative elastic modulus ($E_i/E_0$) decreased to 47.9%. However, when SCC was subjected to the coupled effect of 300 freeze–thaw cycles and $1/3$ peak stress, the mass loss rate was 2.95%, ${\sigma }_p$ decreased by 35.5%, ${\epsilon }_p$ increased by 79.9%, and $E_i/E_0$ decreased to 42.9%. Compared with freeze–thaw cycles alone, the coupled effect of freeze–thaw cycles and load accelerated deterioration of SCC. A damage constitutive model of SCC derived from the hypothesis of Lemaitre strain equivalent and Weibull statistical distribution could well describe the constitutive relation of SCC under the coupling of freeze–thaw cycles and load. As the number of freeze–thaw cycles increased, shape parameter $m$ exponentially decreased and scale parameter $a$ changed according to the cubic equation of one variable. Shape parameter $m$ decreased with the increase of the number of freeze–thaw cycles, and scale parameter $a$ in the Weibull statistical distribution was related to freeze–thaw cycles and load.