Effects of polycarboxylate ether grafted silica fume on flowability, rheological behavior and mechanical properties of cement-silica fume paste with low water-binder ratio

Utilizing low water-binder ratio and high dosage of supplementary cementitious materials is the effective way to improve the performance of concrete, however, it is often accompanied by poor workability. Herein, two kinds of polycarboxylate ether grafted silica fume (VPCE-SF/KPCE-SF) were prepared by grafting comb-like PCE onto the surface of SF. The flowability, rheological behavior and mechanical properties of cement-SF paste with VPCE-SF/KPCE-SF were investigated at water-binder ratio was 0.18. The results indicated that VPCE-SF and KPCE-SF were both displayed more effective dispersibility than comb-like PCE in cement-SF paste. Rheological analysis showed that the yield stress and viscosity of cement-SF paste with KPCE-SF were lower than that of VPCE-SF. It is due to the adsorption ability of KPCE-SF on cement and SF particles were stronger than VPCE-SF. The flexural and compressive strength of cement-SF paste with KPCE-SF were lower than that of VPCE-SF at 3 d, since cement-SF paste with KPCE-SF represented stronger retardation effect on hydration than VPCE-SF. However, cement-SF paste with KPCE-SF has higher flexural and compressive strength compared with VPCE-SF at 7 d and 28 d. (C) 2020 Elsevier Ltd. All rights reserved.