Dispersing silica fume in cementitious materials by silane copolymerized polycarboxylate Superplasticizer: On the role of dispersion effectiveness as a function of silane concentration

In this paper, a commonly used vinyl based silane coupling agent (SC), namely gamma-methacryloxy propyl trimethoxyl silane (MAPTMS) was designed to co-polymerize with polycarboxylate superplasticizer (PCE) to increase the compatibility of PCE with silica fume (SF). The role of dispersion effectiveness as a function of silane concentration was systematically analyzed. It was found that at lower MAPTMS concentration, the prepared SC-PCE showed better SF dispersion capability than the control PCE with increasing MAPTMS concentration. The increased particle dispersion effectiveness was confirmed by minimized volume average particle size of SF by two orders of magnitude (from 27.507 mu m to 0.275 mu m), as well as a much slower SF particles settlement speed in a model cement solution. Increment of cement compressive strength reconfirmed the positive effect of SC-PCE on particle dispersion. When the mole substitution of AA by MAPTMS overran to 40%, however, SC-PCE behaved like polymeric silane silica sol and gelled as indicated by increase of viscosity overtime. The dispersion ability of SC-PCE ceased to be in effect. A maximum substitution ratio of MAPTMS was therefore need to be considered when designing a more effective SC-PCE for SF, as well as for other siliceous SCM.

Automated summary

In this study, a commonly used vinyl-based silane coupling agent, MAPTMS, was designed to co-polymerize with PCE in order to improve the compatibility of PCE with SF. The results showed that SC-PCE prepared at lower MAPTMS concentrations exhibited better SF dispersion capability compared to the control PCE. However, when the mole substitution of AA by MAPTMS exceeded 40%, SC-PCE behaved like polymeric silane silica sol and gelled over time.