Hydration plays a crucial role in cement composites, but the traditional methods for measuring hydration heat face several limitations. In this study, we propose a machine learning-based approach to predict hydration heat at specific time points for three types of cement composites: ordinary Portland cement pastes, fly ash cement pastes, and fly ash–metakaolin cement composites. By adjusting the model architecture and analyzing the datasets, we demonstrate that the optimized artificial neural network model not only performs well during the learning process but also accurately predicts hydration heat for various cement composites from an extra dataset. This approach offers a more efficient way to measure hydration heat for cement composites, reducing the need for labor- and time-intensive sample preparation and testing. Furthermore, it opens up possibilities for applying similar machine learning approaches to predict other properties of cement composites, contributing to efficient cement research and production.

Hydrophobic interactions are widely applied in diverse fields, yet the effect of the degree of hydrophobicity on the interactions between hydrophobic surfaces is still unaddressed, limiting the development of functional hydrophobic surfaces. In this study, the interfacial interactions and configuration of hydrophobic chains on surfaces with ranging hydrophobicity are surveyed by surface forces apparatus. Our findings revealed that with partial hydrophobicity, a long-range electrical double-layer repulsive force pertains between surfaces, while between fully hydrophobized surfaces, only steric hindrance is observed, and the hydrophobic chains maintain configuration even after long time compression. Our findings provide useful implications for understanding hydrophobic interactions.

This study proposes a multiscale prediction method that couples the DTW-CEMHYD3D hydration kinetics model with Mori–Tanaka homogenization theory to establish a quantitative relationship between hydration microstructure evolution and macroscopic heat and mass transport properties of cement-based materials. First, dynamic time warping (DTW) is introduced to correct the mapping relationship between the hydration cycle number in CEMHYD3D and the real hydration time. Then, cement-based materials are regarded as multiphase composites, and a unified calculation method for the effective diffusion coefficient and thermal conductivity is established. The results show that the DTW-CEMHYD3D model can markedly improve the prediction accuracy of early-age hydration heat. The average relative error between the predicted effective diffusion coefficient and the N-phase sphere model is 0.67%, while the coefficients of determination for thermal conductivity prediction and relative diffusion coefficient prediction during hydration reach 0.9812 and 0.987, respectively. Parametric analysis indicates that a higher water-to-binder ratio significantly increases the relative diffusion coefficient, and this effect exhibits nonlinear enhancement with hydration age. The influence of fly ash content is age-dependent. An increase in the degree of saturation reduces the chloride diffusion coefficient but only slightly increases the thermal conductivity. The proposed method provides a reference for durability analysis and parameter determination in multiphysics coupling models of cement-based materials.

The water-to-cement ratio and temperature are key factors governing ionic transport in cement-based materials. However, quantitative descriptions of their coupled effects on sulfate ion transport–reaction processes remain limited. In this study, a coupled transport–reaction model is developed to simulate sulfate ingress in cementitious materials subjected to external sulfate attack. The predictive capability of the model is validated through a series of well-designed experiments, and the distributions of sulfate ion concentration within the materials under different water-to-cement ratios and temperature conditions are systematically analyzed. The results demonstrate good agreement between model predictions and experimental measurements, indicating that increases in both water-to-cement ratio and temperature significantly accelerate sulfate diffusion and intensify chemical reactions between sulfate ions and cement hydration products, thereby promoting material degradation. These findings highlight that the coupled effects of water-to-cement ratio and temperature should be explicitly considered in durability assessment and numerical modeling of external sulfate attack in cement-based materials to improve predictive accuracy.

The relationship between rheological properties and printability in 3D-printed recycled concrete incorporating calcined oyster shell powder (COSP) remains insufficiently understood. The unstable rheological behavior and insufficient buildability of 3D-printed recycled concrete limit its application in digital construction. In this study, the COSP, a marine solid waste-derived functional powder, was incorporated into 3D-printed recycled concrete to improve rheological behavior and printability. The effects of different COSP contents on rheological properties and structure build-up were assessed. In addition, MIP, XRD, and SEM analyses were used to clarify the underlying regulation mechanism. The results showed that COSP significantly improved the rheological properties of fresh paste. As the COSP content increased from 0% to 5%, the static yield stress, dynamic yield stress, and thixotropic recovery degree increased from 1703 Pa to 4561 Pa, from 92 Pa to 375 Pa, and from 56% to 87%, respectively. Meanwhile, the structural deformation rate decreased from 12.3% to 6.37%, corresponding to a reduction of approximately 48%. An appropriate COSP content also improved the mechanical properties, with the flexural strengths in the X and Y directions increasing to 5.17 MPa and 4.99 MPa, respectively, and the compressive strengths increasing to 26.04 MPa and 25.48 MPa, respectively. The microscopic performance results indicated that COSP refined the pore structure, promoted the formation of hydration products, and improved compactness. This study offers preliminary evidence for improving the printability of 3D-printed recycled concrete, while addressing the urgent environmental challenge of marine solid waste utilization and enhancing the economic feasibility and production efficiency of 3D-printed concrete.