Hybrid Additive Strategies for Sustainable 3D Concrete Printing (2025-11)¶

Three-dimensional (3D) printing of concrete faces critical challenges in balancing early-stage strength, printability, and sustainability for rapid construction. This study introduces a hybrid strategy that synergizes replacement and supplementation methods to optimize fiber-reinforced 3D printable concrete (3DPC), leveraging agro-industrial byproducts such as silica fume, fly ash (FA), rice husk ash, recycled concrete (RC), and recycled glass (RG). A custom-designed Cartesian printer equipped with a screw-based extrusion system (nozzle diameter: 32 mm) was employed to evaluate the rheological and mechanical properties. Results showed that replacing cement with 5 wt% RC and 5 wt% FA achieved exceptional compressive strength (28.9 MPa at 28 days), while supplementing with 5 wt% RG and 5 wt% FA boosted split tensile strength to 12.2 MPa, vital for resisting tensile stresses. These sustainable substitutions decrease cement consumption by 5%–10%, thereby repurposing construction waste and industrial byproducts to mitigate the carbon footprint of 3DPC. The optimized mixture, incorporating 5 wt% FA, cellulose-based viscosity modifying admixture, and polypropylene fibers (6 mm), ensures consistent extrusion (slump flow: 153 mm) with minimal deformation (0.8 mm/layer), overcoming scalability barriers in 3D concrete printing (3DCP). This research bridges material innovation with printer-specific design, establishing a systematic framework for eco-efficient 3DCP that advances rapid construction through sustainable solutions.