Rheological assessment of metakaolin-based geopolymer composites through squeeze flow

Geopolymer (GP) composites show great potential as a replacement for ordinary Portland cement (OPC) in construction material, extrusion-based, and additive manufacturing. The rheological properties of highly viscous and reinforced systems have not yet been well studied, due to limitations in the current state of the art rheometers and viscometers, such as size and torque limits. In this study, the basic rheological properties of highly reinforced, geopolymer composites with potential for 3D printing are innovatively investigated with “squeeze flow” and “flow table” tests commonly used in civil engineering. Squeeze-flow rates of 0.1, 1.0, and 3.0 mm/s were assessed with varying sand weight percentages or basalt fiber lengths and compared to a conventional OPC mixture to differentiate the flow properties and deformation resistance of both materials. It is shown that the deformation resistance as a result of jamming increases with increasing solid reinforcement percentages, but that the overall effect of fiber size is somewhat inconclusive. In addition, the effect of squeeze-flow rate exhibits an increase in load required to initiate flow at lower squeezing rates, but, upon reaching a certain ratio of solids to liquid in the matrix, the results become variable.