Mechanical, Alkali Excitation, Hydrothermal Enhancement of 3D Printed Concrete Incorporated with Antimony-Tailings (2024-08)¶

A multitude of antimony tailings (AT) solid wastes haphazardly accumulated in the open environment resulted in significant land resource occupation and serious ecological environment damage. AT as the fine aggregate additive in concrete is an effective approach for achieving solid waste resource utilization. Currently, 3D-printed AT concrete offers notable benefits in design flexibility, precision, material efficiency, productivity, and sustainability compared to conventional concrete. However, traditional AT-concrete is plagued by drawbacks including uneven strength distribution, protracted construction periods, and considerable resource consumption. Furthermore, the low reactivity and non-degradability of AT necessitate implementing modified activation techniques in AT concrete. This paper employs four modification methods (physical grinding, alkali excitation, hydrothermal activation, and combined activation) to activate AT. The modified AT is incorporated into concrete at five ratios (0 %,10 %, 20 %, 30 %, and 40 %) and integrated into a 3D printing system, manufacturing a total of 450 samples for mechanical property experiments. The result demonstrates that the combined modification method emerges as the optimal choice for enhancing the unconfined compressive strength (65.7 MPa) and flexural strength (12.9 MPa) in 3D printing. The SEM results revealed that the combined modification, alkali excitation, and hydrothermal activation led to AT depolymerization and sediment adsorption. Abundant C-S-H gel and a handful of Ca(OH)2 crystals were observed on the physically modified AT (30 μm) surface, indicating sufficient pozzolanic reaction on 3D printed fine AT.