Nanofibrillar Cellulose Stabilizer for Cementitious Gas Pore Structure
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Solution Overview
Problem
Existing methods for gas-entrainment in cementitious materials, such as air-entrainment, face challenges in maintaining stable and robust gas pore structures, especially under varying water content conditions, leading to potential freeze-thaw damage and inhomogeneous pore distribution.
Innovation Solution
The use of nanofibrillar cellulose (NFC) as a gas-entraining stabilizer in cementitious materials, combined with gas-entraining agents, to enhance the quality and stability of gas pore structures, ensuring consistent air content and density regardless of water content variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gas-entraining agents are used to create air voids in concrete, then workability and freeze-thaw durability are improved, but the gas pore structure becomes unstable and inhomogeneous when water content varies
Solution Approach 1:
The patent introduces a surfactant as an intermediary substance that mediates between the air-entraining agent and the cementitious material. The surfactant forms a stable interface between air bubbles and the liquid cement paste, preventing bubble coalescence and maintaining homogeneous air void distribution even when water content varies. This intermediary mechanism resolves the contradiction by providing additional stability to the gas pore structure without compromising freeze-thaw durability.
Solution Approach 2:
The patent modifies the chemical and physical parameters of the cementitious mixture by adding specific surfactants that change the surface tension and interfacial properties of the mixture. This parameter change enables the air voids to remain stable and homogeneous across varying water content conditions, while maintaining the beneficial freeze-thaw resistance properties of air-entrained concrete.
2Manufacturing precision
If air content is increased to compensate for gas pore separation, then surface quality is improved, but the complexity of controlling air content and quality increases
Solution Approach 1:
The surfactant acts as a control mechanism that simplifies the air content control process. By providing a stable interface that prevents bubble coalescence and migration, the surfactant allows for more predictable and consistent air void distribution, reducing the complexity of controlling air content while achieving uniform surface quality.
Solution Approach 2:
The addition of surfactants changes the interfacial parameters of the cementitious mixture, creating a more stable air-liquid interface. This parameter change makes the air content more predictable and easier to control during mixing, reducing the operational complexity while maintaining high surface quality through uniform air void distribution.
3Ease of operation
If water content is varied to adjust workability, then ease of operation is improved, but gas pore structure homogeneity deteriorates
Solution Approach 1:
The surfactant serves as a buffer that allows water content to be varied for workability adjustment without compromising gas pore homogeneity. The surfactant's interface-stabilizing action prevents bubble coalescence even when water content changes, maintaining homogeneous air void distribution while allowing operational flexibility in water content adjustment.
Solution Approach 2:
The surfactant changes the interfacial properties of the mixture, creating a more robust air-liquid interface that is less sensitive to water content variations. This parameter change enables water content to be adjusted for workability while maintaining gas pore structure homogeneity, as the modified interfacial properties prevent bubble coalescence during mixing and placement.
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
NFC improves the robustness and stability of gas-entrained cementitious materials by maintaining consistent air content and density, reducing the impact of water content variations and enhancing the durability against freeze-thaw cycles.
Implementation Method 1
Gas-entrainment, in particular air-entrainment, of concrete increases the durability of the hardened concrete in climates subject to freeze-thaw. Furthermore, it increases workability of the concrete while in a plastic state. In air-entrained concrete, air voids are formed in a way that they intersect the capillaries at regular intervals.
Implementation Method 2
Freeze-thaw cycles may cause damage to concrete and other hardened cementitious materials due to freezing and expanding of water. When the water in the capillaries starts to freeze, the pressure in the capillary system rises. Before the pressure reaches to a level where it could cause cracking, the water is forced into the air voids and the pressure drops.
Implementation Method 3
The shearing action of mixer blades breaks up the air into a fine system of bubbles and the AEA acts like surfactants and helps to create smaller air bubbles.
Implementation Method 4
When the concrete becomes wet, water will end up to the capillary system by capillary suction and for the most part the air voids remain empty.
Data Source
AI summary
The invention relates to use of nano-fibrillar cellulose as an gas-entrainment stabilizer, which when used in cementitious materials, provides improved gas pore structure quality and/or stability and/or robustness with regard to water content variation. The invention further relates to a method for stabilizing gasentrainment of cementitious materials and to a method for providing cementitious material with improved air pore structure quality and/or stability and/or robustness with regard to water content variation.