Development of cost-effective geopolymer mortars from low-grade metakaolin and bottom ash for 3D construction printing

As part of the pursuit for more cost-effective and sustainable building materials, geopolymers have been a promising substitute for traditional Portland cement with the capability of lowering both carbon footprint and material cost with high mechanical performance. In this work, we explore an economically feasible geopolymer mortar designed for construction 3D printing by assessing four locally sourced precursors: high-grade metakaolin, low-grade MK, bottom ash (BA), and ground granulated blast-furnace slag. When mixed with BA, experimental results show that calcined low-grade MK provides comparable or superior compressive strength, faster setting, and favorable rheological properties to high-grade MK mixtures at reduced cost. Rheology tests confirm that such mixtures still have good extrudability and buildability for 3D printing, while microstructural investigations (SEM and XRD) show good geopolymer gel formation. Through the utilization of local by-products, the process, as suggested, lowers carbon footprint as well as material cost, hence a promising pathway to sustainable additive manufacturing within the construction industry.