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<p>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&#xa0;s<sup>−1</sup>) and low shear (0.001–10&#xa0;s<sup>−1</sup>) over 30&#xa0;min, capturing structural breakdown and recovery under realistic, time-resolved conditions. Structuration was quantified using the polynomial-based build-up rate parameter (<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41062_2025_2273_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="37" /> </InlineMediaObject> <EquationSource Format="TEX">\({A}_{thix}\)</EquationSource> </InlineEquation>) and thixotropic recovery by the recovery rate constant (<InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41062_2025_2273_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(k\)</EquationSource> </InlineEquation>), 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&#xa0;s<sup>−1</sup>, where sustained shear enhanced particle contact, alignment, and hydration product nucleation. SEM, EDS and XRD analyses confirmed the depletion of C<sub>3</sub>S, C<sub>3</sub>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&#xa0;min, providing a framework linking rheology, microstructure, and process parameters for early-age cementitious systems.</p>

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

  • 期刊论文

  • 发表日期：

    2025年9月30日

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  • Astha Sharma,
  • Sandeep Chaudhary

摘要

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 ( \({A}_{thix}\) ) and thixotropic recovery by the recovery rate constant ( \(k\) ), 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 C3S, C3A, 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.