Development of 3D Printable Alkali-Activated Slag-Metakaolin Concrete (2024-08)¶

In the current landscape of 3D-printed construction, the extensive utilization of Portland cement has undeniably resulted in significant carbon dioxide emissions. This paper introduces an environmentally friendly 3D printing material, alkali-activated slag-metakaolin concrete, addressing the imperative for a cleaner and greener alternative in the realm of 3D-printed architecture. The findings indicate that incorporating metakaolin (MK) into alkali-activated slag mixtures markedly improves static yield stress due to its higher specific surface area, thereby promoting favorable conditions for the extrusion stage. Additionally, it only results in a marginal increase in dynamic yield stress, necessitating only modest pumping pressure during 3D printing. Higher content of Na2O in the activator also can lead to higher dynamic and static yield stress. Plastic cracking could occur for the samples containing a higher MK content of 20 %. A notable improvement in compressive strength is achieved with a 10 % addition of MK, with the principal gel conferring strength identified as calcium aluminosilicate hydrate and geopolymer as identified by XRD, FTIR, TGA and thermodynamic modeling. The carbon dioxide emissions from producing a 3D printable alkali-activated slag-MK mixture were estimated to be reduced by up to approximately 30 % compared to those from Portland cement production.