Impact of pore solution composition and superplasticizers on the interparticle forces and rheology of metakaolin suspensions

This study focuses on the influence of pH, aqueous phase composition and superplasticizers on the particle interactions in pure metakaolin suspensions. It was found increasing pH up to 11 led to the decrease of the particle agglomeration due to the higher OH − adsorption onto metakaolin particles, which increased the absolute zeta potential and generates higher electrostatic repulsive forces. Above pH = 11, a slight increase in zeta potential was observed and colloidal stability was retained. Metakaolin suspensions prepared in Na 2 SO 4 or Ca(OH) 2 at pH = 13 did not agglomerate. However, the simultaneous presence of Ca 2+ and SO 4 2− , led to particle agglomeration, which was enhanced as Ca 2+ concentration increased. The rise of Ca 2+ concentration in suspensions containing Ca 2+ and SO 4 2− also induced higher yield stress values in metakaolin suspensions. The addition of polycarboxylate ether (PCE) superplasticizers deagglomerated metakaolin particles and decreased yield stress values in agreement with interparticle force modelling.