Developing an appropriate concrete mix for 3D concrete printing

In recent years, 3D printed concrete (3DPC) has gained significant attention as a means to advance construction industry industrialization. 3D printing construction technology can accelerate construction, reduce manual labour and raw materials, and enhance design flexibility by eliminating formworks. A primary challenge in 3DPC is the disparity in composition and efficacy compared to conventional concrete. Digital construction offers numerous opportunities but requires addressing complex issues like green strength, buildability, and extrudability. This study investigates the characteristics of 3D printable concrete using Bentonite clay as a rheological modifier. Tests on various mixes reveal that adding 3% Bentonite increases compressive strength by up to 15% and initial shear strength by 60% compared to mixes without Bentonite. Additionally, Bentonite increases mix consistency but decreases flow by more than 50%. Long-term strength is reduced with higher Bentonite percentages due to its non-cementitious nature. Optimal results are achieved with 3% Bentonite, a sand-to-binder ratio of 1, and a water-to-cement ratio of 0.3.