Enhancing the Printability and Mechanical Strength of 3D-Printed Geopolymers through Li2O-Al2O3-SiO2-H2O System Regulation (2026-02)¶

Achieving time-dependent thixotropic behavior in geopolymer 3D printing to meet extrudability and post-hardening mechanical performance remains a critical challenge. This research introduces a Li2O-Al2O3-SiO2-H2O (L-A-S-H) system through a three-stage experimental investigation, including characterizing the microstructural evolution of the L-A-S-H system, evaluating the workability and rheological properties of geopolymer mortars, and assessing their 3D printing performance. The results identified Li2SiO3, LiAl LDH, and Li-ABW zeolite as the main crystalline phases in the L-A-S-H system, with mass fractions of 7.2%, 18.3%, and 72.2%, respectively, after 3d of curing. With only 1 wt% addition, the system enhanced extrudability and buildability by 47.0% and 5.7%, respectively, while increasing mechanical strength by 20.0%. These improvements originate from a unique dynamic three-dimensional network formed between micron-sized LiAl LDH, Li-ABW zeolite, and the geopolymer matrix. Prior to extrusion, this structure exists as a weakly cross-linked colloidal network susceptible to shear disruption. After deposition, it spontaneously re-forms and undergoes progressive cross-linking, leading to structural recovery and strengthening. This mechanism also confers superior thixotropy, evidenced by a 52.9% increase in thixotropic area. In summary, the L-A-S-H system provides a viable strategy for enhancing the overall 3D printing performance of geopolymers.