Study on the Meso-Statistical Damage Constitutive Model of Coral Aggregate Seawater Concrete Incorporating Natural Aggregate Replacement Ratio Effects.

Coral aggregate seawater concrete (CASC) capitalizes on locally sourced aggregates in marine and reef engineering, enabling in situ material utilization and conferring marked benefits in curbing conventional resource consumption and construction expenditures-a combination that underpins its considerable promise for reef infrastructure development. To date, research efforts have largely been confined to macroscopic mechanical characterization and qualitative microstructural inspections, and quantitative assessments of mesoscopic damage evolution across the full loading-to-failure process remain relatively scarce. In response, to quantitatively characterize the mesoscopic damage evolution mechanism of CASC with different natural aggregates, the present study draws upon statistical damage theory and incorporates uniaxial compressive stress-strain responses from CASC mixtures formulated with four replacement ratios (0%, 33%, 67%, and 100%) of natural coarse and fine aggregates, thereby establishing a statistical damage constitutive model. The model is intentionally structured to decipher the intricate interplay that translates progressive mesoscopic deterioration into the eventual macroscopic mechanical signature, rather than merely describing phenomenological curves. The outcomes reveal favorable concordance between model-generated predictions and experimental measurements. Introducing natural aggregates appreciably modulates the cumulative damage trajectory at the mesoscale; with rising replacement ratios, the macroscopic mechanical performance of CASC is systematically fortified, concomitant with orderly shifts in characteristic damage indices (εa, εb, εh and H). Specifically, when the replacement ratio of natural fine aggregate is fixed at 0%, as the replacement ratio of natural coarse aggregate increases from 0% to 100%, the values of εa, εb, εh, and H increase by 35.8%, 36.9%, 32.2%, and 66.5%, respectively. Additionally, both the fracture damage variable DR and the integrated transverse strain area derived from digital image correlation (DIC) exhibit monotonic ascending trends as loading advances. Collectively, these contributions offer a theoretical foundation for performance optimization and a deeper mechanistic understanding of damage behavior in CASC.