Extrusion and rheology characterization of geopolymer nanocomposites used in 3D printing

Abstract

This study focused on the suitability of geopolymer mixes for extrusion-based additive manufacturing applications. Geopolymer mixes including alkaline potassium silicate activator with different molar ratios were prepared and evaluated for their rheological responses (e.g. yield stress, viscosity and thixotropy) that influenced their extrudability and buildability. Due to the low yield stress of geopolymers, nanoclay was introduced to enhance their thixotropy, which was assessed by structural breakdown and viscosity recovery tests. An activator-to-binder ratio of 0.35 and water-to-solid ratio of 0.30 were found to work well with a clay addition of 0.5% (i.e. by mass of total binder component). The addition of nanoclay led to an improvement in the rheological properties of geopolymer nanocomposites, which was attributed to the flocculation characteristic of the clay particles. A small-scale bathroom unit was printed by using the developed geopolymer nanocomposite, indicating the suitability of the proposed mix design to be used in 3D printing applications.