An Integrated Hydration and Property Evaluation Model for Coral Powder–Cement Binary Blends

With the rise in the marine industry and marine tourism, coral powder is increasingly used to make concrete for marine islands. This study proposes a three-parameter hydration model and a hydration kinetic model to predict the performance of coral powder concrete based on previous experimental data. The process of the proposed prediction model is as follows: 1. The input parameters of the three-parameter hydration model are calibrated for the first 7 days using the cumulative hydration heat per gram of cement. The maximum cumulative hydration heat (455.87 J/g cement) and the shape coefficient (−0.87) remain constant. In this study, the hydration rate coefficients for 0%, 10%, and 20% coral powder were 6.91, 6.19, and 5.55, respectively, showing decreases of 10.41% and 19.68% compared with the specimens without coral powder. 2. At 28 days, the cumulative heat release values per gram of cement for 0%, 10%, and 20% coral powder were 389.77, 395.69, and 401.62 J/g, showing increases of 1.52% and 3.04% for the specimens containing 10% and 20% coral powder, respectively. Meanwhile, the hydration degrees for 0%, 10%, and 20% coral powder were 0.855, 0.868, and 0.881, respectively, showing increases of 1.52% and 3.04%. Furthermore, the cumulative heat release values per gram of binder were 389.77, 356.12, and 321.29 J/g, showing decreases of 8.63% and 17.56% for specimens containing 10% and 20% coral powder, respectively. 3. Properties such as compressive strength, ultrasonic pulse velocity (UPV), and surface electrical resistivity were evaluated using the power function and the cumulative hydration heat per gram of binder. 4. At 28 days, the chemically bound water contents for samples with 0%, 10%, and 20% coral powder were 0.2402, 0.2197, and 0.1981 g/g binder, respectively. Moreover, the calcium hydroxide contents were 0.1848, 0.1690, and 0.1524 g/g binder, showing reductions of 8.53% and 17.52% in bound water and 8.54% and 17.53% in calcium hydroxide. 5. A hydration kinetic model is proposed, which can distinguish between the dilution effect and the nucleation effect of coral powder, unlike the three-parameter model, which cannot distinguish between the two effects. Furthermore, the input parameters of the hydration kinetic model remain unchanged for different mixtures, while the input parameters of the three-parameter model must be varied among mixtures. Parameter analysis of the hydration kinetic model indicated that a low water–binder ratio and a high coral powder substitution rate significantly improve the relative reaction level of cement.

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