Cement 3D Printing Composition for Extrudability and Self-Support
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Solution Overview
Problem
Existing hydraulic compositions for 3D printing with cementitious materials face challenges in achieving both ease of extrusion from a nozzle and self-supportability following deposition, as these properties are inherently incompatible.
Innovation Solution
A hydraulic composition comprising water-soluble hydroxyalkyl alkyl cellulose with specific DS and aqueous-solution viscosity, a defoamer, cement, water, and diutan gum, optimized in specific proportions, to enhance extrudability and self-supportability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a cementitious material is formulated for ease of extrusion from a nozzle, then extrudability is improved, but self-supportability following deposition deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the degree of substitution (DS) of hydroxyalkyl groups in hydroxyalkyl alkyl cellulose to be within 1.4-2.0, and the aqueous-solution viscosity at 2 wt% to be within 50-1,000 mPa·s. These specific parameter ranges optimize the material's rheological properties to achieve both low extrusion pressure and adequate self-supportability. The controlled parameter changes allow the material to exhibit appropriate flow characteristics during extrusion while maintaining structural integrity after deposition.
Solution Approach 2:
The patent employs composite materials by combining cement with specific concentrations of hydroxyalkyl alkyl cellulose (0.1-0.6 part by weight per 100 parts by weight of cement) and diutan gum (0.01-0.3 part by weight per 100 parts by weight of cement). This composite formulation creates a material system where the cellulose derivative and gum work synergistically to modify the cement paste's rheological behavior, enabling simultaneous achievement of extrudability and self-supportability that neither component could provide alone.
2Strength
If the viscosity of the hydraulic composition is increased to improve self-supportability, then self-supportability is improved, but extrusion pressure increases
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing the viscosity of the aqueous solution of hydroxyalkyl alkyl cellulose to be within 50-1,000 mPa·s at 2 wt% concentration. This controlled viscosity range, combined with the specific degree of substitution (1.4-2.0), allows the material to provide adequate self-supportability while maintaining low enough viscosity for easy extrusion at reasonable pressures. The parameter optimization ensures the material exhibits shear-thinning behavior appropriate for extrusion while maintaining structural integrity afterward.
Solution Approach 2:
The hydroxyalkyl alkyl cellulose acts as an intermediary substance that mediates between the conflicting requirements of self-supportability and extrusion pressure. By adding this cellulose derivative at controlled concentrations (0.1-0.6 part by weight per 100 parts by weight of cement), it modifies the rheological properties of the cement paste to achieve a balance where the material is neither too viscous for extrusion nor too fluid to support itself after deposition.
3Strength
If silica fume is added to improve material properties, then material strength is improved, but thixotropy increases leading to poor dischargeability
Solution Approach 1:
The hydroxyalkyl alkyl cellulose serves as an intermediary that counteracts the harmful thixotropic effects of silica fume. By introducing this cellulose derivative with specific rheological properties (viscosity 50-1,000 mPa·s at 2 wt%, DS 1.4-2.0), it modifies the overall flow behavior of the cementitious material to compensate for the increased thixotropy caused by silica fume addition, thereby maintaining adequate dischargeability while preserving the strength benefits of silica fume.
Solution Approach 2:
The patent uses composite materials by combining silica fume with hydroxyalkyl alkyl cellulose and diutan gum in specific proportions. This composite approach creates a balanced material system where the cellulose and gum components offset the negative thixotropic effects of silica fume, allowing the material to simultaneously achieve high strength and good dischargeability that would be incompatible in a simpler formulation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition achieves low pressure extrusion and good self-supportability, making it suitable for additive manufacturing, particularly 3D printing by material extrusion.
Implementation Method 1
silica fume-containing hydraulic compositions are very thixotropic
Implementation Method 2
the 2 wt % aqueous-solution viscosity at 20° C. of from 50 to 1,000 mPa·s
Implementation Method 3
a defoamer
Data Source
AI summary
In a hydraulic composition for additive manufacturing which includes (A) at least one water-soluble hydroxyalkyl alkyl cellulose selected from hydroxypropyl methyl cellulose and hydroxyethyl methyl cellulose, (B) a defoamer, (C) cement, (D) water and (E) diutan gum, the water-soluble hydroxyalkyl alkyl cellulose has an alkoxy group degree of substitution of from 1.6 to 2.0 and a 2 wt % aqueous-solution viscosity at 20° C. of from 50 to 1,000 mPa·s and the water is added in an amount of from 25 to 70 parts by weight per 100 parts by weight of the cement. The composition has a good extrudability from a nozzle and a good self-supportability following deposition.