Investigation on the Applicability of Bauxite-Tailings as Fine Aggregate to Prepare 3D Printing Mortar (2022-12)¶

Using tailings to replace natural resources to prepare building materials is not only effectively alleviate the pressure of natural resource shortage, but also has important significance for environmental protection. This study aims to explore the applicability of bauxite tailings as fine aggregate instead of natural sand to prepare 3D printing mortar. The workability, rheological properties, buildability, hydration properties and mechanical properties of 3D printing mortar using bauxite tailings instead of 15%, 25%, 35% and 45% of natural sand were determined. The results show that the incorporation of tailings reduces the fluidity, slump and setting time of the 3D printing mortar, but delays the hydration process of the cementitious material. The rheological analysis reveals that the incorporation of tailings can significantly improve the static yield stress, dynamic yield stress, plastic viscosity and thixotropy of 3D printing mortar. With increasing tailings content, the macroscopic deformation and structural deformation rate of 3D printed components are gradually decreased. The compressive strength and flexural strength of 3D printing mortar are increased first and then decreased with increasing tailings content. Based on the test results, it is determined that the optimal ratio is that the mass ratio of tailings to replace natural sand is 35%, which can make the 3D printing mortar obtain good workability and high mechanical strength. Overall, it is feasible to use bauxite tailings to prepare 3D printing mortar, which optimizes both buildability and mechanical properties.