Assessment of Accelerators for 3D-Printed LC3-Based Cementitious Materials (2026-02)¶

This study evaluates the influence of three chemical accelerators—potassium sulfate (K2SO4), calcium chloride (CaCl2) and sodium hydroxide (NaOH)—at two dosage levels (1.5% and 3.0% by binder mass) on the performance of limestone calcined clay cement (LC3) mortars for 3D printing applications. CaCl2 and NaOH significantly accelerated setting times, with reductions of up to 66% and 57% in initial setting time, respectively, enhancing early-age workability and buildability. CaCl2 notably improved early mechanical properties, increasing tensile strength from 0 to ∼1.8 MPa and compressive strength by over 3,000% after 6 hours, while NaOH primarily enhanced fresh-state stiffness and load-bearing capacity with moderate strength gains at later ages. In contrast, K2SO4 functioned mainly as a hardening accelerator, increasing 1-day tensile and compressive strengths by 82% and 144%, respectively, without substantially affecting setting times or fresh-state properties. Microstructural characterization revealed that CaCl2 and NaOH accelerate hydration kinetics but may compromise long-term durability due to incomplete phase development and heterogeneous pore structures, whereas K2SO4 promotes stable ettringite formation and matrix integrity. These findings provide critical insights for selecting accelerator types and dosages to optimize the rheology, buildability, and mechanical performance of 3D-printed LC3 mortars in sustainable construction.