Synthesis and dispersing properties of organosilane-modified superplasticiser in cement–silica fume composite binder

The impacts of organosilane-modified polycarboxylate superplasticiser (OS-PCE) on the fluidity and hydration performance of a cement–silica fume (SF) composite binder were systematically analysed. It was found that the saturation adsorption amounts of OS-PCE on cement and SF were, respectively, 30.74% and 23.49% higher than those of ordinary PCE and the greater adsorption behaviour of OS-PCE contributed to higher fluidity of the cement–SF binder. The addition of OS-PCE retarded the hydration process of the cement–SF binder proportionally with the dosage of OS-PCE, but promoted the hydration kinetics of the composite binder. The enhancement in reactivity was attributed to well-dispersed SF by the OS-PCE, which provided more nucleation sites for the reaction of heterogeneous calcium silicate hydrates (C–S–H) and enhanced the contact with water to react with calcium hydroxide forming pozzolanic C–S–H. Well-distributed hydration products were identified in the hardened binder with added OS-PCE, with a large number of hydrated gels uniformly filling the pores and gaps, which densified the hardened structure.