Biochar-augmented climate-positive 3D printable concrete

Three-dimensional (3D) concrete printing is a revolutionary technology in the construction industry. Here we show that climate-positive biochar is a carbon-negative additive for decreasing the carbon footprint of 3D printable concrete, while enhancing its performance. As biochar enhanced the effective water-to-binder ratio and served as a substrate for hydrates, the polymerization of hydrates increased in biochar-augmented concrete. The incorporation of 2 wt% biochar enhanced the structural build-up rate of fresh mixtures by 22% at 40 min. The 3D printing tests demonstrated that biochar improved the pumpability and extrudability of mixtures at the initial 20 min, and enhanced the buildability of 3D printed concretes at the after 40 min. The carbon footprint of 3D printable concrete was reduced by 8.3% through incorporating 2 wt% biochar. Thus, we developed a desirable biochar-augmented mixture for 3D concrete printing. Future field-scale application will make substantial contribution to the attainment of carbon emission reduction. 3D printing of concrete is promising for the manufacture of bespoke structures, but the high cement component leads to large carbon dioxide emissions. Here, climate-positive biochar is shown to decrease the carbon footprint of 3D printed concrete, while improving its pumpability, extrudability, and buildability