Time-resolved rheological characterization of cement paste using a distinct shear protocol: quantifying thixotropic and hydration-driven structuration

Abstract

The time-dependent rheological behavior of cement paste is critical to modern construction processes. The present study investigates the simultaneous development of irreversible structuration and reversible thixotropic rebuilding in cement pastes with w/c ratios from 0.40 to 0.55 using a cyclic shear protocol. The method alternated between high shear (100 s−1) and low shear (0.001–10 s−1) over 30 min, capturing structural breakdown and recovery under realistic, time-resolved conditions. Structuration was quantified using the polynomial-based build-up rate parameter () and thixotropic recovery by the recovery rate constant (), both serving as practical indicators for mix optimization in applications such as 3D printing, self-compacting concrete, and pumping. Lower w/c ratios (0.40 and 0.45) exhibited faster, stronger rebuilding due to denser particle packing and accelerated hydration product networking, while w/c = 0.40 showed nonlinear trends linked to particle jamming during early hydration. Structuration rates peaked at 10 s−1, where sustained shear enhanced particle contact, alignment, and hydration product nucleation. SEM, EDS and XRD analyses confirmed the depletion of C<inf>3</inf>S, C<inf>3</inf>A, and gypsum, as well as the formation of ettringite, C-S-H gel, and portlandite, which correlated with the observed rheological changes. The results define optimal w/c ratios, shear conditions, and processing windows within the first 30 min, providing a framework linking rheology, microstructure, and process parameters for early-age cementitious systems. © 2025 Elsevier B.V., All rights reserved.