The Viscosity Properties of Sodium Silicate Solutions

Using a NDJ-1 rotational viscometer and an AR500 rheometer, both static and dynamic viscosities of sodium silicate solutions were measured with changes of concentration, temperature, modulus (molar ratio of SiO₂ to Na₂O), shear rate and chemical additives. Static results show that viscosity increases monotonously with concentration varying from 15 to 55%, decreases with temperature rising from 15 to 70 °C, and has a minimum value at a modulus of about 1.8. Measured data can be fitted quantitatively either by the Krieger-Dougherty expression or the Arrhenius equation with good agreement. This fact suggests that the sodium silicate solutions exhibit the properties of a suspension, in which the silicate anions, mainly constructed of Q ¹ and Q ² groups, act as a binder; the colloidal particles mainly constructed of Q ³ and Q ⁴ groups and small cations, act as effective rigid particles. Dynamic results show a shear thickening property in the high shear-rate regime, and a Newtonian property in the low shear-rate regime.