Mechanical Characteristics of Precast Cracked Concrete under Freeze-Thaw-Load Action

Abstract

Four types of precast double-cracked concrete specimens and non-cracked control group were prepared, and the specimens were subjected to freezing and thawing cycles and uniaxial compression tests, with a total of five freezing and thawing cycles, namely 0, 25, 50, 75 and 100, in order to analyse the fracture phenomena and mechanical properties of the specimens after freezing and thawing in uniaxial compression, and to determine the damage variables of the precast cracked concrete under the action of freezing and thawing loads on the basis of strain energy and fracture mechanics theories. The test results show that: (1) the crack aggregation mode generated by the compression damage of precast cracked specimens is mainly influenced by the crack inclination angle, when the crack inclination angle is 30°, the specimen undergoes wing tension aggregation, and when the crack inclination angle is 60°/90°, the specimen undergoes a mixed tension-shear aggregation mode; (2) After the freeze-thaw cycle test, the degree of deterioration of the prefabricated cracked specimens is significantly higher than that of the non-cracked specimens, and the loss of compressive strength and Young’s modulus of the specimens with crack inclination angle of 60° and 90° is the most severe, and the decrease of the stress-strain curve is the most obvious; (3) Based on fracture mechanics and damage-strain energy to derive the damage variables of the prefabricated cracked loaded specimens, and based on the Weibull function and the principle of equivalent effect of Lemaitre effect, the damage variables under freeze-thaw loading are also derived based on the Weibull function and Lemaitre equivalent strain principle.