Experimental Investigations and Development of a Comprehensive Rheological Model for Cement Paste: A Novel Integration of Thixotropic Behavior and Hydration Effects

The article presents an innovative approach to understanding cement paste rheology for advanced construction applications, particularly three-dimensional (3D) concrete printing. Through a systematic investigation combining experimental observations with predictive modeling, the present article examines the complex relationship between reversible thixotropic behavior and irreversible hydration-induced changes in cement paste. Our novel methodology integrates distinct and constant shear rate testing protocols, providing comprehensive insights into rheological changes. By analyzing cement pastes with water–cement ratios of 0.40–0.55 and employing advanced characterization techniques, including isothermal calorimetry, x-ray diffraction, and scanning electron microscopy, critical correlations between microstructural development and rheological performance during early hydration were established. Key findings revealed optimal performance at water–cement ratios of 0.40–0.45, with maximum structural evolution at very low shear rates (0.01 s−1), showing differential values of 1,200–2,000 Pa. A comprehensive rheological model was developed and validated, achieving exceptional accuracy with R2 values of 0.92–0.98 and RMSE values below 15%. This research bridges materials science and practical construction applications, providing crucial insights for emerging technologies such as 3D concrete printing.