Cellulose nanofibers and limestone filler enable high-performance, sustainable, and cost-efficient printable concrete

3D-printed concrete requires carefully tuned rheological properties to ensure successful printing. Achieving a balance between printability, mechanical performance, sustainability and cost remains a challenge due to high cement content and extensive use of chemical admixtures typically required to meet rheological constraints. In this study, we develop a high-performance, low-carbon, cost-effective printable concrete using cellulose nanofibers and limestone filler. Incorporation of 0.3% cellulose nanofibers with 29% limestone filler replacement increases the static yield stress, storage modulus, and critical strain by 1213%, 255%, and 542%, respectively, with a moderate impact on viscosity compared to the reference mixture. Microstructural analyses indicate that the limestone filler accelerates hydration and enhances early-age stiffening, while the cellulose nanofibers increase static yield stress through colloidal interactions. Cellulose nanofibers enhance both compressive and flexural strength, allowing up to a 40% reduction in cement content while maintaining mechanical performance. Robotic 3D printing of a large-scale element demonstrates the scalability of the developed mixture and underscores its potential for large scale applications. Finally, techno-economic analysis and life-cycle assessment further demonstrate the environmental and economic benefits of the proposed mixtures. The study develops a printable concrete using cellulose nanofibers and limestone filler, enhancing rheological and mechanical properties while reducing cement content. It demonstrates improved buildability and sustainability, with potential for large-scale 3D printing applications in construction.