Abstract
This study investigates the effect of a complex modifying admixture on the capillary water absorption and setting times of cement stone. The experimental program included the determination of capillary water absorption intensity at both early and advanced stages of saturation, as well as the evaluation of the initial and final setting times of cementitious binder containing different dosages of the admixture. The results demonstrated that increasing the admixture content leads to a significant reduction in capillary water absorption intensity. This effect was observed both during the initial stage of testing and at longer saturation periods, indicating a decrease in capillary porosity and the formation of a denser cement stone structure. The improved microstructure is attributed to the microfilling action of silica fume and the hydrophobic effect of the organic components incorporated in the admixture. The setting time analysis showed that the application of the complex admixture has a negligible influence on the standard hardening characteristics of the cementitious binder. A slight tendency toward accelerated initial setting was observed with increasing admixture dosage, whereas the final setting time remained almost unchanged. Therefore, the use of the complex admixture contributes to reduced capillary water absorption and the development of a denser cement stone structure while maintaining acceptable technological setting parameters.