Effects of aqueous-phase speciation on Portland cement and supplementary cementitious materials as reflected using zeta potential of powder suspensions

Abstract

The zeta-potential of cementitious powder suspension is significant for its cement hydration and highly depends on its soluble components. In this work, the suspension zeta-potentials of Portland cement (PC), ground granulated blast-furnace slag (GGBS), fly ash (FA) and silica fume (SF) were examined in pure-water (PW) and saturated calcium-hydroxide (CH) along with 0 ∼ 24 h. The corresponding ion-concentration was examined for analyzing its effects on zeta-potential. The results manifested that the inchoative-charges of PC, GGBS, FA and SF in PW respectively were +1.50 mV, −0.28 mV, +0.48 mV and −0.27 mV while the inchoative charge-reversal occurred when their powders were dispersed in CH. The ion-strength magnitude of PC, GGBS, FA and SF in PW and CH were both in the decreasing order of PC > FA > SF > GGBS, and CH solvent improved their ion-strengths. The Zeta-potential of PC suspension reduced with the increasing ion-strength while the relationships between Zeta-potential and ion-strength of SCMs increased first and then decreased with the threshold of approximately 40 mmol/L.