Prediction of yield stress and plastic viscosity of superabsorbent polymer modified cement pastes: YODEL model and Krieger-Dougherty equation

Abstract

This study aimed to predict the yield stress and plastic viscosity of Superabsorbent Polymer (SAP)-modified cement pastes using the Yield stress mODEL (YODEL) and the Krieger-Dougherty (K-D) equation. Predictions were made for cement pastes with SAP dosages of 0.2–0.5% (by weight of cement) and water-to-cement (w/c) ratios of 0.4–0.6, over 5–35 minutes, and were compared with experimental data. In the YODEL model, the percolation threshold (\(\phi _{0}\)) and surface-to-surface separation distance (H) were fitted. The \(\phi _{0}\) values (0.20–0.27) decreased over time, indicating paste stiffening and reduced percolation. The values of H (1.5–3 nm) declined with higher SAP dosages and over time due to water absorption and hydration, leading to increased flocculation and stiffening. In the K-D model, intrinsic viscosity [\(\eta \)] was adjusted; [\(\eta \)] increased with higher SAP dosages, greater w/c ratios, and time, consistent with thickening caused by SAP water uptake and hydration. For w/c = 0.4, predictions agreed with experiments from 5–15 min, with larger deviations occurring later. For w/c = 0.5 and 0.6, predictions aligned from 5–20 min, with slight overestimations and underestimations afterward. The K-D equation generally provided close agreement with experimental viscosities, showing only minor deviations. Overall, YODEL effectively captured early-age yield stress behavior, while the K-D equation successfully predicted viscosity trends, demonstrating the combined potential of these models for describing the rheology of SAP-modified cement paste.