Formulation and Characterization of a Low-Carbon Impact Cementitious Ink for 3D Printing (2022-06)¶

3D printing is considered to be the most innovative construction technique. A challenge encountered with this technique is the ecological impact of the used mortar (ink). Indeed, due to the small particle size of the used sand, inks contain large amounts of Portland cement, which increases the carbon footprint of the material. This study is carried out in a partnership with Constructions 3D company, it concerns the design and characterization of a cementitious ink with a high cement substitution rate in order to reduce its environmental impact. This mortar is made from a reference ink composed of cement. We chose to work with constant workability based on the slump flow test and an equivalent Water/Binder ratio for the two mortars by adapting the admixture. A fresh state characterization allows evaluating the influence of the materials on the buildability of the mortars (fall cone test) and a hardened state characterization allows evaluating their influence on the mechanical aspect (compressive strength at 2, 7, 28 and 90 days, and shrinkage). Finally, full-scale prints are made in order to confirm the printability of this low carbon impact ink. Although 70% of the cement is replaced bymetakaolin and ground granulated blast-furnace slag, the mortar produced is not less effective than the reference mixture and fully meets the specifications imposed by the 3D printing technique. The ternary ink formulated in this way will be tested on site to assess its properties in real conditions.