Mesoscale simulation of fatigue behavior of concrete materials damaged by freeze-thaw cycles

Frost damage is a common durability problem for concrete structures in cold and wet regions, and in many cases, the frost damage is coupled with fatigue loadings such as the traffic loads on bridge decks or pavements. In this paper, to investigate the basic fatigue behavior of concrete materials affected by frost damage, a mesoscale approach based on Rigid Body Spring Method (RBSM) has been developed, of which the concrete material can be divided into three parts: mortar, coarse aggregate and interfacial transition zone (ITZ) between them. First, the cyclic constitutive laws are developed at normal and shear directions for mortar and ITZ, and verified with the existing experimental data in compression and tension fatigue. Then, several levels of frost damage are introduced by different numbers of freeze-thaw cycles (FTCs), and finally, the static tests and fatigue tests are conducted using the frost damaged concrete. The simulation results on the static strength and fatigue life show a good agreement with experimental data, and found that as the frost damage level (irreversible plastic deformation) increases, not only the static strength, but also the fatigue life at each stress level will decrease. The S-N curves of frost damaged concrete still follow a linear relationship but with bigger slopes, and the frost damaged concrete will become more ductile under fatigue loadings.