Advanced 3D Concrete Printing (3DCP) with Low-Carbon Calcium Sulfoaluminate (CSA) Cement Blends

Abstract Ecological demands are driving clinker reduction in construction, which may adversely affect material properties and delay production. The partial replacement of clinker by calcium sulfoaluminate (CSA) cement in blended systems based on blast furnace or pozzolanic cement offers advantages such as accelerated setting while simultaneously reducing CO 2 emissions. Due to the use of the new binder composition in 3D concrete printing (3DCP), additional efficiency can be achieved. From a materials engineering perspective, a controlled retardation of setting is necessary to enable the integration of CSA cement-based mixtures into the 3DCP process. At high levels of clinker substitution with latent hydraulic or pozzolanic binders, low amounts of citric acid used as setting time retarder lead to losses in mechanical strength, as these binders develop little to no strength in the absence of Portlandite. Therefore, a partial clinker replacement of 51 wt.% through 30 wt.% CSA cement with 21 wt.% Supplementary Cementitious Materials, such as ground granulated blast furnace slag or metakaolin, along with 0.76 wt.% citric acid to achieve a 90 min processing window has proven technically viable with respect to strength development. The investigated ternary binder systems demonstrate a balanced interaction without adverse synergistic effects, even in the presence of setting time retarders. Furthermore, the developed mixture exhibits high compatibility with 3DCP processes and ensures stable and continuous extrusion. Mechanical strength is not negatively affected by the 3DCP process.