In a recent article published in the journal Additive manufacturingThe researchers discussed the shape stability, rheological characteristics and compressive strength of 3D printed colored cement composites modified with needle-like pigments.
Study: Rheological properties, shape stability and compressive strength of colored 3D printed cement composites modified by needle-like pigment. Image Credit: Parmna/Shutterstock.com
As one of the fastest growing additive manufacturing products, 3D printed concrete (3DPC) has been widely researched as a construction material. In the case of 3D printed constructions, fresh cement pastes with exceptional extrudability and buildability are required for successful installation. Fresh paste should have appropriate plastic viscosity and dynamic yield strength during pumping and extrusion, as well as high static yield strength during stacking.
Recent research has suggested that the flow law of various printed cement pastes incorporating additional materials and rheological additives can be revealed by rheology control, which introduces the flow law of various printed cement pastes incorporating additional materials and rheological additives.
White Portland cement (WPC) is a cementitious material commonly used in the architectural decoration industry due to its consistent performance, high lightness and ease of staining. Research into 3D printed WPC composites, on the other hand, is still in its infancy. Additionally, preparing 3D-printed WPC composites so that they can display a wide color gamut and meet artistic modeling requirements for architectural components brings additional hurdles.
About the study
In this study, the authors investigated the impact of needle-shaped yellow pigment (YP) and sheet-shaped blue pigment (BP) as coloring components in 3D-printed WPC-based materials on rheological characteristics, colorability, shape stability and compressive strength.
The team demonstrated how different pigment dosages affected the color performance, buildability, extrudability, and mechanical strength of 3D printed WPC and determined what the best pigment dosage was. Sheet-shaped pigment blue (BP) and needle-shaped pigment yellow (YP) of the three primary colors were added to WPC to create 3D printed colored cement composites (3DPCCC). Using a precision colorimeter to confirm the color saturation point, the impact of various doses of YP/BP on the shading effect was described.
Researchers measured the dynamic and static yield strength of color-modified 3DPCCCs to manage structural deformation and printability. To analyze the mechanical property and hydration reaction, the heat of hydration and compressive strength of 3DPCCCs were also examined. In addition, the practicality of the ideal mixture was confirmed by the printing of a large pentagram component.
When the YP concentration approached 2%, huge micropores with a pore diameter greater than 2 mm were found, along with a considerable increase in the relative ratio of macropores. The compressive strength increased by 12.3% from 42.2 MPa to 47.4 MPa when the YP content increased from 0% to 2%.
When the BP content was increased from 0 to 2%, the strain of the structure increased from 10.38% to 14.3%, then decreased to 11.5% when the BP content was increased to 4 %. The static yield strength of 3DPCCCs was significantly reduced upon addition of BP, with a BP concentration of around 12%. The static yield strength of 3DPCCCs with 2% BP was 450 Pa, which was the lowest.
The addition of YP increased the static yield strength and thixotropy of 3DPCCCs, which resulted in a considerable reduction in the deformation of the structure. The compressive strength of 3DPCCCs with 2% YP was improved by 12.3% at 47.4 MPa, and structural deformation was reduced by almost 50% compared to the reference sample.
Although the inclusion of BP improved the extrudability of 3DPCCCs, it also reduced the shape stability and compressive strength. Furthermore, the paste exhibited good extrudability and buildability in a large-scale 3D-printed pentagram component with 2% YP, and 16 stacking layers were obtained without apparent deformation.
In conclusion, this study used needle-shaped YP and sheet-shaped BP to color WPC-based materials to create 3DPCCCs. The main objective was to see how they affected rheological behavior, colorability, printability and compressive strength. As the pigment content of 3DPCCCs increased, the colorability improved.
Both YP and BP reached saturation thresholds of 3%, with a small difference in total color. YP significantly improved the static yield strength of 3DPCCCs, which was helpful in improving buildability. To achieve the extrudability criterion, the YP content must not exceed 3% and the dynamic yield strength of 3DPCCC containing YP must be less than 414.17 Pa.
The inclusion of BP reduced the dynamic yield strength, allowing better extrudability, but at the expense of buildability and compressive strength. The compressive strength of 3DPCCCs having 2% YP increased by 12.3% compared to the reference sample. Moreover, as the YP content increased to 4%, the structural deformation of 3DPCCCs having YP decreased by 69.7%. 2% YP was added to the mortar to create a large 3D printed pentagram with up to 16 layers without significant deformation, based on excellent printability and compressive strength.
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Jin, Y., Xu, J., Li, Y., et al. Rheological properties, shape stability and compressive strength of 3D printed colored cement composites modified by a needle-like pigment. Additive manufacturing 102965 (2022). https://www.sciencedirect.com/science/article/abs/pii/S221486042200358X