The application potential of recycled aggregate concrete has been realized with the development and utilization of waste concrete. Fibers are added to concrete made with recycled coarse aggregate to enhance its mechanical properties and broaden its application possibilities. Additionally, in practical applications, parts of structural elements are frequently under compressionshear stress. As a result, the normal stress ratio k (k = σ/f cu , where σ is axial compressive stress, and f cu is concrete cube compressive strength), coarse aggregate replacement rate, and carbon fiber content are used as design parameters to examine the compressive-shear mechanical properties of carbon fiber recycled aggregate concrete in this paper. The results show that the normal stress ratio and fiber content affect the whole compression-shear process curve, shear strength, peak shear displacement, and damage evolution. A compressive shear damage model that takes into account the aggregate replacement rate, normal stress ratio, and fiber content is established. And there is good agreement between the experimental findings and the calculation model.

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This paper investigates the compression behavior and failure criteria of lightweight aggregate concrete (LAC) under triaxial loading. A total of 156 specimens were tested for three parameters: concrete strength, lateral confining pressure and aggregate immersion time, and their effects on the failure mode of LAC and the triaxial stress-strain relationship of LAC is studied. The research indicated that, as the lateral constraint of the specimen increases, the failure patterns change from vertical splitting failure to oblique shearing failure and then to indistinct traces of damage. The stress-strain curve of LAC specimens has an obvious stress plateau, and the curve no longer appears downward when the confining pressure exceeds 12 MPa. According to the experimental phenomenon and test data, the failure criterion was examined on the Mohr–Coulomb theory, octahedral shear stress theory and Rendulic plane stress theory, which well reflects the behavior of LAC under triaxial compression. For the convenience of analysis and application, the stress-strain constitutive models of LAC under triaxial compression are recommended, and these models correlate well with the test results.

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