Tailored Yield Stress for 3D Printing Using Low-Clinker Cement (2026-03)¶

This paper focuses on solutions for CO2 reduction in the construction sector. It explores the use of supplementary cementitious materials (SCMs) and the development of 3D-printable mortars as one- and two-component systems. The interaction between physical and chemical material properties is examined to understand better the crucial parameters controlling early rheological properties. New test methods, including a penetration test, uniaxial compression test, and slug test, are developed, validated, and presented to adequately assess the monitoring of these early physical properties. The insights from these interdisciplinary investigations are particularly significant for additive manufacturing, as they allow for controlling material properties according to more complex requirements. The formation of ettringite, in particular, plays a significant role in this context. Based on the acquired knowledge, the investigated cementitious systems for 3D printing are tailored using selected accelerators and formulated on the principle of “setting-on-demand.” For injection-based 3D printing, an accelerator containing aluminum sulfate, which accelerates early ettringite formation, is used. Additionally, a predominantly ettringite-forming two-component system (OPC-CSA-C$), consisting of two cementitious pastes, is developed. The two pastes, retarded for several hours, exhibit rapid strength development when mixed. The substitution of OPC with calcined clay and limestone, or slag, is another topic addressed in this paper. It is observed that mortars composed of such systems are indeed suitable for 3D printing.