Damage Constitutive Model of Fly Ash Concrete under Freeze-Thaw Cycles

The mechanical deterioration of concrete exposed to freeze-thaw cycles is one of the most important durability problems under subzero temperature conditions. At present, studies on concrete behavior under freeze-thaw cycles primarily focus on the degradation of concrete properties, there are few reports on testing and modeling the stress-strain relationships of concrete undergoing repeated cycles of freeze-thaw. This paper investigated the stress-strain relationship of fly ash concrete under 0, 5, 15, 30, 50, 75, 100, and 125 freeze-thaw cycles by testing 24 prism specimens. The relative dynamic modulus, compressive strength, elastic modulus, and stress-strain relationship of specimens under freeze-thaw cycles were measured. In addition, a multiple sharp degradation point model for the degradation of mechanical properties of concrete was proposed. Finally, a damage constitutive model on the base of the damage mechanics and the multiple sharp degradation point model was presented. By comparing the results calculated by the damage constitutive model with the experimental data, the proposed model was proved to be effective for evaluating the stress-strain relationship of fly ash concrete under freeze-thaw cycles.

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