Research on the constitutive relationship of concrete under uniaxial compression in freeze–thaw environment

• The quantitative method was used to analyze the stress–strain curve during freeze–thaw. • The quantitative relationship between freeze–thaw damage parameters and mechanical indices was determined. • The stress–strain curve model of concrete considering freeze–thaw damage variables was established. • The stress–strain curve model reflects the variation law of the curve during freeze–thaw. Through uniaxial compression tests of concrete prism specimens with strength grades ranging from C35 to C65 under without freezing–thawing (F–T) and with rapid F–T cycles, the damage form, stress–strain relationship, quasi-static mechanics performance, and deformation performance of the specimens were obtained. Further, the relationship between the F–T damage variable, and a model for the F–T damage variable stress–strain curves of the concrete were established. After F–T, the concrete prism specimen exhibited a typical split failure with the crack developed along the interface transition zone (ITZ), and severe damage. The F–T cycles reduced the mechanical properties and brittleness, and increased the ductility of concrete. The linear relationship between the peak stress, peak strain, and static elastic modulus of concrete under uniaxial compression and F–T damage was established. Finally, a unified constitutive model of the concrete stress–strain curve relationship considering the F–T damage variable was established. The resulting model can accurately reflect the stress–strain relationship of concrete under uniaxial compression during F–T, which can provide a reference for future research on the constitutive relationship of concrete F–T damage..