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Effects of starch-type polysaccharide on cement hydration and its mechanism

Zhang, Hao, Feng, Pan, Li, Lei, Wang, Wenbing
Thermochimica acta 2019 v.678 pp. 178307
cement, concrete, gels, molecular weight, polysaccharides, sodium hydroxide
Polysaccharides are widely used as chemical admixtures to modify the early age properties of mortars and concrete and a new starch-based chemical admixture pre-dissolved in NaOH and water was used to reveal the mechanism. The result shows that the induction period can be extended obviously. The impacts of dissolved TRI on surface state of cement particles, C-S-H nucleation and growth process in ion reaction and in cement suspension were investigated. It can be reported that TRI molecular would also adsorb on the surface of generated C-S-H globules which inhibits transforming C-S-H globules to the soil-like C-S-H, C-S-H (around 50 nm) continues to nucleate, transform and grow to large particles after that dissolved TRI are completely consumed by the generated C-S-H gel which causes the prolonged induction period. In addition, it has been shown that polysaccharide with larger average molecular sizes result in longer cement hydration induction times.