Cementitious Print Head Steam CO2 Injection Protocol
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Solution Overview
Problem
Cementitious compositions used in 3D printing are fast-setting and have low slump, making them unsupported after extrusion, which poses challenges in maintaining structural integrity during printing.
Innovation Solution
A print head system that includes a feed barrel, nozzle, CO2 and steam supplies, and a selective valve assembly for the selective injection of CO2 and steam into the cementitious composition to enhance hydration and carbonation reactions, ensuring the extruded material is self-supporting by programming a protocol that prioritizes steam followed by CO2 injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cementitious compositions are made fast-setting with low slump to maintain structural integrity after extrusion, then the extruded material becomes self-supporting, but the material loses workability and becomes difficult to extrude smoothly
Solution Approach 1:
Steam is injected into the cementitious composition before CO2 to pre-heat the material and initiate hydration reactions in advance. This preliminary thermal and chemical action prepares the material structure, allowing it to maintain integrity while still being extrudable at the required speed
Solution Approach 2:
The patent changes the temperature and chemical state parameters of the cementitious composition by injecting steam and CO2. The steam raises the temperature and initiates hydration, while CO2 provides carbonation. These parameter changes occur in a controlled sequence that maintains extrudability while achieving self-supporting properties
2Reliability
If steam and CO2 are injected simultaneously into the cementitious composition, then both hydration and carbonation reactions are enhanced, but the control over reaction timing and material properties becomes difficult
Solution Approach 1:
The injection system is segmented into separate steam injection and CO2 injection pathways with independent control valves. This segmentation allows each gas to be injected at different times and rates, providing precise control over the hydration and carbonation reactions without requiring a complex integrated system
Solution Approach 2:
Steam injection is performed before CO2 injection as a preliminary action. This sequential approach allows the hydration reaction to be initiated and controlled first, followed by carbonation. The preliminary steam treatment prepares the material in a controlled manner, making the overall process more reliable
3Strength
If CO2 is injected into the cementitious composition to enhance carbonation reaction, then the material strength increases, but excessive CO2 injection can cause rapid setting and loss of extrudability
Solution Approach 1:
Steam is injected before CO2 to pre-heat and partially hydrate the cementitious composition. This preliminary action creates a more stable material structure that can tolerate CO2 injection without rapid setting, thereby maintaining extrusion speed while still achieving strength through carbonation
Solution Approach 2:
The patent carefully controls the temperature parameter through steam injection before CO2 injection. This temperature change modifies the reaction kinetics, allowing CO2 to enhance strength without causing such rapid carbonation that would eliminate extrudability
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 system achieves self-supporting extruded cementitious compositions that maintain at least 95% dimensional integrity, allowing for larger print beds and higher speeds, and can be configured for various printing architectures.
Implementation Method 1
steam may be exclusively selected for injection by the extrusion head injectors into a cementitious composition as it is extruded from the print head nozzle to enhance a hydration reaction and formation of hydroxide
Implementation Method 2
CO2 may be exclusively selected for injection by the extrusion head injectors into the cementitious composition as it is extruded from the print head nozzle to enhance a carbonation reaction
Data Source
AI summary
A cementitious print head and a cementitious printing methodology may include a feed barrel, a print head nozzle, a CO2 supply, a steam supply, a selective valve assembly in communication with the CO2 supply and the steam supply, a plurality of dual use extrusion head injectors, and a print head controller. The print head controller is operatively coupled to the selective valve assembly and is programmed to execute a CO2 and steam injection protocol where steam may be selected for injection by the extrusion head injectors into a cementitious composition as it is extruded from the print head nozzle to enhance a hydration reaction and formation of hydroxide in the cementitious composition before CO2 may be selected for injection by the extrusion head injectors into the cementitious composition as it is extruded from the print head nozzle to enhance a carbonation reaction in the cementitious composition.