Hydraulic Composition Air Void Spacing Control
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Solution Overview
Problem
Hydraulic compositions with water-soluble cellulose ethers face challenges in achieving frost damage resistance and controlled bleeding due to excessive air content and difficulty in maintaining fine air bubbles, often requiring defoamers that inadvertently eliminate beneficial air bubbles.
Innovation Solution
A hydraulic composition combining a specific air-entraining agent with a fatty acid-based surfactant, a nonionic polyoxyethylene phenyl ether surfactant, and hydroxypropyl or hydroxyethyl methyl cellulose, optimized to maintain an air void spacing factor of 25 to 250 μm, thereby achieving frost resistance and reduced bleeding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water-soluble cellulose ether is added to hydraulic composition, then material segregation resistance and bleeding reduction are improved, but air content becomes excessive
Solution Approach 1:
The patent extracts and removes the harmful large air bubbles entrained by water-soluble cellulose ether using a defoamer, while preserving the beneficial fine air bubbles (25-250 μm) needed for frost damage resistance. This selective removal resolves the contradiction between reducing excessive air content and maintaining frost resistance.
Solution Approach 2:
The patent applies different quality requirements to different air bubbles: large air bubbles are removed as harmful, while fine air bubbles within 25-250 μm are retained as beneficial. This local differentiation of air bubble quality allows simultaneous achievement of controlled air content and frost damage resistance.
2Quantity of substance
If defoamer is used to remove coarse air bubbles, then air content is controlled, but fine air bubbles needed for frost damage resistance are also eliminated
Solution Approach 1:
The patent introduces an air-entraining agent as an intermediary substance that works in conjunction with the defoamer. The air-entraining agent continuously generates fine air bubbles (25-250 μm) that are protected from being removed by the defoamer, while the defoamer removes larger harmful bubbles. This intermediary mechanism allows simultaneous air content control and frost damage resistance.
3Reliability
If conventional AE agents are used to entrain fine air bubbles, then frost damage resistance is achieved, but air content becomes uncontrolled and bleeding increases
Solution Approach 1:
The patent uses a composite approach by combining the defoamer and air-entraining agent in a single hydraulic composition formulation. This composite system allows the defoamer to control overall air content while the air-entraining agent provides the necessary fine air bubbles for frost resistance, achieving both goals simultaneously without the drawbacks of using either agent alone.
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 effectively provides frost damage resistance and restrained bleeding while maintaining a controlled air content, outperforming previous solutions in terms of material segregation resistance, bleeding reduction, and fluidity.
Implementation Method 1
For imparting frost damage resistance to the hydraulic composition, fine air bubbles having a diameter of about 25 to about 250 μm must be entrained into the hydraulic composition. To this end, air entraining (AE) agents are typically used.
Implementation Method 2
The hydraulic composition to which a water-soluble cellulose ether is added, however, may have an excessive air content because the water-soluble cellulose ether has a surface-active effect to entrain more air bubbles during mixing of the hydraulic composition.
Implementation Method 3
It is thus a common practice to use a defoamer to remove coarse air bubbles.
Data Source
AI summary
A hydraulic composition comprising an AE agent, water-soluble cellulose ether, defoamer, cement, water, and aggregate is provided. The AE agent contains a fatty acid-based surfactant consisting of a fatty acid, alkali metal salt, lower alkylamine salt or lower alkanolamine salt thereof and a nonionic surfactant consisting of a polyoxyethylene phenyl ether. The hydraulic composition has frost damage resistance and experiences little bleeding.