Toward the optimal use of local cementitious materials through novel admixture technology and a dedicated 2K printing system

Common products designed for the extrusion-based 3DCP method are often unappealing from both economic and environmental perspectives. This is due to their typically high cost as pre-mixed systems (1k-system), intricate formulations, and high cement content. To address this challenge and facilitate the utilization of locally sourced materials in 3DCP, we offer a solution based on admixtures (2k-system). The transition to 2k systems represents a paradigm shift, enabling better control over the individual steps involved in the printing process and increasing room for making the best use of the cement content. The proposed solution includes a retarder admixture to control fresh mortar/concrete rheological properties and a liquid accelerator injected into the extruding nozzle for structural formation regulation and early strength development. An essential aspect of this technology is its ability to enable the utilization of OPC-based and/or blended cement formulations, leading to a substantial reduction in raw material costs promoting cost-effectiveness. Additionally, it emphasizes the integration of locally available materials in 3DCP formulations, contributing to the sustainability of the construction process. Consequently, the technology offers a comprehensive solution to address existing technical and economic challenges hindering widespread 3DCP adoption. In this contribution, OPC cement was selected for its proximity to industrial printing trials, with sustainability in mind during dry mortar mix design. Cement content was reduced to 17% of the total dry mix weight by substituting it with a blend of three lime-stone powders, varying in particle size to optimize packing density. Printing trials at XtreeE facility confirmed the feasibility of the proposed solution in controlling workability, setting time, and strength development.