Mechanical properties and failure criteria of carbon fiber-reinforced coral concrete under biaxial compression

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Coral concrete is a vital construction material for advancing island and reef development, but its impact resistance and toughness are relatively poor, which can be enhanced by incorporating carbon fibers (CF). In practical engineering, concrete is often subjected to multiaxial stress, and its mechanical properties differ from those under uniaxial stress. To better understand the performance of CF reinforced coral concrete (CFRCC) under biaxial stress, this study designed and conducted biaxial constant stress ratio compression tests on CFRCCs with stress ratios α, CF dosages ρ, and coral concrete strength grades as the research parameters. The results indicate that the CFRCC failure mode gradually shifts from a columnar failure mode to a lamellar splitting failure mode with increasing α, with the fracture surface angle relative to the σ3 direction related to α, ρ, and the coral concrete strength grade. The biaxial compressive strength σ3c and peak strain ε3c of the CFRCC initially increase and then decrease with increasing α and ρ, reaching their maximum values at α = 0.25–0.50 and ρ = 1.5 %, respectively. The peak strain ε2c transitions from tensile strain to compressive strain betweenα of 0.25–0.40. Based on the experimental data, new biaxial strength failure criteria with high accuracy and universality were established. Unified biaxial strength failure criteria and strain failure criteria suitable for CFRCCs were developed in the principal stress and principal strain spaces, respectively, the calculated values of the failure criterion show high consistency with the experimental values.