3D printable hemp concrete: Rheological, mechanical, and microstructural properties

Hemp concrete, as one variety of vegetal concretes, has been extensively studied as it holds promise as a sustainable, high-performing, and eco-conscious building materials by its carbon-sequestering characteristics, yet its potential and early stages of development for 3D Concrete Printing (3DCP) remains largely unexplored. While previous studies on 3D printing of hemp concrete are limited and mostly focus on feasibility using cylinder pumping, this study is the first to systematically investigate 3D-printed hemp concrete using a robotic 3D printing system. This study demonstrates the feasibility of incorporating hemp shivs into printable sustainable concrete for 3DCP. The effect of hemp shivs on printability, buildability, compressive strength and flexural strength are examined experimentally. Experimental results show that the addition of hemp shivs of 1–4 % by weight of sand improves the flowability by 16.7 % without significantly reducing the buildability (±1.7 % relative to control mix). Furthermore, in comparison with the control mixture, the flexural strength of 3D printable hemp concrete exhibits larger reduction (57–60.6 %) stacked up against their compressive strength (45.9–54.8 % depends on printing directions). Microstructural characterization indicates that pre-treatment of hemp and optimized particle grading can further improve interlayer bonding and pore distribution. Overall, the findings confirm that hemp-based mixtures can be adapted for 3DCP, offering a pathway to carbon-conscious construction materials while identifying key parameters for future optimization.