Role of Dispersion Degree of Nanoclays In Controlling Viscoelastic Properties of Fresh Cement Pastes

Presented by Ala Eddin Douba, Columbia University

Nanoclays (NC) have been explored as a thixotropy modifier for many concrete applications, including reducing self-consolidating concrete formwork pressure, improving slipform paving, and reducing rebound during shotcreting. Given their ability to enhance structural build-up, they are also a strong candidate for achieving shape stability of deposited layers during extrusion-based 3D concrete printing. However, early studies have indicated that typical dosing of ~ 0.5 wt % is not sufficient to meet the high rheological demands of this technique. And with current processing methods, higher dosing while achieving sufficient dispersion is difficult to achieve. This study explores various NC processing techniques and examines their efficiency in altering yield stress and elasticity of cement pastes, as well as reaching higher dosages. Results show that with the new processing technique a 16x increase in yield stress and 6x increase in storage modulus is achieved with 4 wt % NC, with limited impact on steady-state viscosity. Insights into underlying mechanisms and connections to 3D printing performance will also be discussed.