Rheological property evolution in concentrated cement-polyelectrolyte suspensions

We have studied the rheological property evolution and hydration behavior of pure white portland cement (Type I) pastes and concentrated cement-polyelectrolyte suspensions. Polyelectrolyte species have a marked effect on the initial stability, elastic property evolution (G′(t)), and hydration behavior of this cement system. Pure cement pastes exhibited an initial G′ value of ∼10⁴ Pa and fully reversible G′(t) behavior until the onset of the acceleratory period (t ∼ 2 h), where the pastes stiffened irreversibly. In contrast, cement-polyelectrolyte suspensions exhibited initial G′ values of ∼1 Pa and G′(t) behavior comprised of both reversible and irreversible features. Their initial G′ values, measured after disrupting the particle network under high shear conditions, grew exponentially with hydration time, where G_i′ = G_i,0′ exp(t/τ_c) and τ_c corresponds to the characteristic hydration time determined from calorimetry measurements. Our observations of these cement-polyelectrolyte systems suggest that hydration phenomena impact interparticle forces during early stage hydration and, ultimately, lead to initial setting through the formation of solid bridges at the contact points between particles within the gelled network.