Hempcrete – CO2 Neutral Wall Solutions for 3D Printing

Abstract Hempcrete is a bio-based self-bearing envelope and thermal insulation building material that is becoming more popular nowadays and has a low environmental impact, especially CO2 emissions. This study looks for solutions for hempcrete printing using a custom-built gantry type 3D printer typically used for concrete 3D printing. Preliminary research shows that hempcrete can be printed at a relatively low density of 660 kg/m3 and achieve an adequate buildability and compressive strength for printing individual wall elements. At this density, hempcrete has a thermal conductivity of 0.133 W/(m·K), unable to provide the adequate thermal resistance at average wall thickness, so high-density hempcrete should be printed as an outer wall shell (similar to Contour Crafting) and the middle filled with lower density thermal insulation hempcrete. By calculating the CO2 emissions of such printed 400–620 mm thick walls, it was found that they absorb from 1.21 to 16.7 kg of CO2 per m2, thus, such material could reduce the negative environmental impact of the construction industry while improving its productivity through 3D printing.