High-alumina cementitious materials for binder jetting 3D printing: Exploring suitable mixing ratio and curing solution for improving mechanical properties and hydration reaction

In recent years, binder jetting 3D printing (BJ3DP) technology has attracted growing attention in construction materials. Although ordinary Portland cement (OPC) is one of the most widely used building materials, its slow hydration reaction limits its effectiveness in BJ3DP. In contrast, calcium aluminate cement (CAC) undergoes a rapid hydration reaction, achieving sufficient strength at an early stage, which is advantageous for BJ3DP applications. Nevertheless, there is still limited research on the suitability of cementitious materials for BJ3DP. Therefore, this work aimed to identify the optimal material mixing proportions and suitable post-processing solutions for BJ3DP by comprehensively evaluating the flowability of the dry materials, print bed characteristics, print quality, and mechanical strength of the printed specimens. The results showed that replacing 40 % of ordinary Portland cement with calcium aluminate cement optimized the flowability of the dry mixture, allowing for the production of specimens with favorable print quality. Furthermore, at this optimal ratio, the printed specimen's compressive strength achieved 12.7 MPa after curing in Na2SiO3 solution for 28 d, representing a 42.6 % increase in compressive strength compared with the specimens cured in water. Simultaneously, the compressive strength of the printed samples increased by 57.7 % compared to our previous results and showed a further 10 % increase under the same curing condition (water curing). Based on these findings, we proposed a novel composition ratio for high-alumina cementitious materials in BJ3DP, consisting of a 60 % OPC and 40 % CAC mix, along with post-treatment of the printed samples using a Na2SiO3 solution. This study broadens the range of cementitious materials suitable for BJ3DP and demonstrates the feasibility of Na2SiO3 as an effective post-treatment solution, providing a theoretical foundation for future research and practical applications of high-alumina cementitious materials.