Valorizing recycled wind turbine blade fibers in printable mortar: Time-dependent dynamic yield stress evolution and predictive modeling

To promote the valorization of recycled wind turbine blade fibers in cementitious materials, this study investigated the time-dependent dynamic yield stress evolution of recycled wind turbine blade fiber-reinforced printable mortar containing 0–2.0 vol% recycled fibers over resting periods of 0–50 min. Rheological behavior was characterized using the Herschel–Bulkley model, which provided satisfactory fits for all mixtures. Based on the experimental results, a time-dependent dynamic yield stress model was developed to quantify both the fiber-induced increase in initial dynamic yield stress and the dosage-dependent variation in rheological build-up. Fiber incorporation significantly increased flow resistance and enhanced rheological structuration during resting. This effect was strongly dosage-dependent: low fiber contents produced build-up behavior close to that of the fiber-free mortar, whereas higher dosages markedly accelerated yield stress growth. The proposed model described the calibration dataset with an R² of 0.989, RMSE of 5.15 Pa, and MAPE of 6.06%. Validation at 0.75% and 1.25% fiber contents demonstrated strong interpolation performance, while a limited extrapolation test at 2.25% yielded an R² of 0.942. These findings provide a quantitative basis for the preliminary rheological design of sustainable printable cementitious materials, while extrudability, buildability, and printing quality require further validation. These results provide a quantitative basis for understanding the time-dependent rheological evolution of recycled wind turbine blade fiber-reinforced printable mortar. These findings provide a quantitative basis for the preliminary rheological design of sustainable printable cementitious materials, while extrudability, buildability, and printing quality require further validation.