A study of the effects of saccharide retarders on Portland cement hydration using trimethylsilylation

Synopsis A structural and mechanistic study using trimethylsilylation to investigate the effects of saccharide retarders and starch on the formation of C-S-H gel showed that sucrose delayed hydration and setting. At a low concentration (1 m mol/li), however, an acceleration of initial set was observed. The onset of silicate anion condensation, calcium hydroxide precipitation, and final set occurred almost simultaneously once the poisoning effect of sucrose had been overcome. The superiority of cellobiose over sucrose as a retarder was attributed to its better calcium solubilizing ability, and the poor performance of starch was due to the low solubility of its alkaline degradation products. Although the kinetics of hydration are altered, the silicate anion distribution of C-S-H at a given degree of hydration is unaffected.