The zeta potential of cement and additions in cementitious suspensions with high solid fraction

This paper considers the zeta potential of Portland cement and mineral additions in cementitious suspensions with high solid fractions and ionic strengths typical for fresh concrete. The zeta potentials of additions were measured for suspensions to which different salts were added. Furthermore, suspensions made with synthetic and real aqueous phases extracted from cement pastes were investigated. It is shown that the concentrations of divalent calcium and sulphate ions determine the zeta potential. Owing to the adsorption of these ions, the zeta potentials of the additions tend towards similar low absolute values. Furthermore, the effect of aqueous phase composition on the zeta potential of cementitious suspensions was quantified. It was found that the composition of the aqueous phase is of greater importance than the type of the addition. The zeta potential of highly concentrated cementitious suspensions is determined by the molar Ca/SO₄ concentration ratio and increases with this ratio.