Performance and interaction of sodium silicate activated slag with lignosulfonate superplasticiser added at different mixing stages

• Published in: Cement & concrete composites Vol. 136; p. 104900
• Main Authors: Ren, Jun, Zhou, Qi-Zhi, Yang, Chang-Hui, Bai, Yun
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2023
• Subjects: Adsorption; Alkali activated cement; Granulated blast-furnace slag; Rheology; Superplasticiser; Granulated blast-furnace slag; Alkali activated cement; Adsorption; Rheology; Superplasticiser
• ISSN: 0958-9465; 1873-393X
• DOI: 10.1016/j.cemconcomp.2022.104900

This paper investigated the effect of adding lignosulfonate (LS) superplasticiser at the different stages of mixing on the workability and rheological behaviour of sodium silicate activated slag (SSAS) in order to find a practically feasible approach to tackling the incompatibility issue between superplasticiser and alkaline activator. In addition to rheology and minislump tests, adsorption, zeta potential and environmental scanning electron microscopy tests were also undertaken to understand the interactions between the lignosulfonate and the fresh SSAS in order to reveal the mechanisms behind the observation. The results show that adding the LS and the activator separately at the different stages of mixing can significantly improve both the initial minislump and 60-min minislump retention due to the increased adsorption of LS and the improved dispersion of slag particles, with the prior addition of LS better than the delayed addition. However, a nonlinear rheological behaviour of SSAS was observed in the LS-superplasticised SSAS under separate addition and, consequently, modified Bingham model was found to be more suitable for describing this kind of rheological behaviour.