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3D Concrete Printing Materials
Material Palette and Mixture Design
Tim Robertson
August 31, 2024
3DCP Printing Materials
The selection of materials for 3D printed concrete is crucial, particularly because the nozzle extrusion process can lead to issues like premature collapsing. Significant research is focused on developing high-quality cementitious materials that meet both structural concrete codes and the specific requirements of 3D printing applications [1].
For instance, mixtures that include ordinary Portland Cement, fly ash, silica fume, and fine glass aggregates can achieve compressive strengths between 36 to 57 MPa, comparable to traditional concrete [1].
The phrase "36 to 57 MPa" refers to a range of pressure or stress measured in megapascals (MPa).
MPa (Megapascal): A unit of pressure or stress in the metric system. 1 MPa is equal to 1 million pascals (Pa).
Pascal (Pa): The standard unit of pressure in the International System of Units (SI), defined as one newton per square meter.
In this context, "36 to 57 MPa" describes the strength of a material, the pressure in a system, or the stress a material can withstand. For a material like concrete, it means the material can withstand compressive forces within this range before failing.
Extrudability and Buildability
For successful 3D printing of concrete, two critical design properties must be addressed: extrudability and buildability.
Extrudability refers to the mixture's ability to pass through the printer head's nozzles, while buildability denotes the mixture's capacity to support additional layers without collapsing. Achieving a balance between stiffness and workability is essential; a stiffer mix increases strength but may reduce flow rate and print speed, potentially clogging the printer head.
Conversely, a mix that is too workable may enhance flow and print speed but at the cost of reduced strength and buildability [1].
Use of Supplementary Cementitious Materials
The use of supplementary cementitious materials (SCMs) like metakaolin, fly ash, and silica fume is common in 3D printed concrete mixtures to enhance various mechanical properties.
These materials act as binders, undergoing chemical reactions with water to form a hardened structure. While the incorporation of these materials can improve rheology and strength, excessive use may lead to reduced early strength and other performance issues [8][1].
Innovations and Current Applications
Recent advancements in 3D printed concrete technology include the development of six-axis robotic 3D printing systems, which allows for the fabrication of freeform, non-planar beads using thermoplastic extrusion [2].
Additionally, innovations in using recycled sand and waste materials as supplementary cementitious components have been explored to improve sustainability and reduce costs [8].