Cementitious Grout Composition for Controlled Shrinkage
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Solution Overview
Problem
Existing cementitious materials, particularly those with high replacement levels of Portland cement by pozzolanic and/or latent hydraulic materials like GGBFS, experience significant shrinkage issues leading to cracking, which conventional admixtures like aluminium powder fail to adequately address.
Innovation Solution
A synergistic combination of aluminium powder, calcium oxide or magnesium oxide, and an organic shrinkage reducing agent is added to cementitious compositions to reduce shrinkage, especially in materials with high slag content, achieving densities of at least 800 kg/m3 after hardening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminium powder is used as a gas-evolving admixture to compensate shrinkage, then shrinkage compensation is achieved, but excessive expansion and much reduced strength occur especially when Portland cement is replaced by GGBFS
Solution Approach 1:
The patent changes the chemical parameters of the system by replacing aluminium powder with a combination of calcium oxide/magnesium oxide and organic shrinkage reducing agents. This parameter change eliminates the harmful excessive expansion while maintaining shrinkage compensation, specifically addressing the issue where aluminium powder causes strength reduction in high-GGBFS formulations
Solution Approach 2:
The patent uses calcium oxide or magnesium oxide in combination with organic shrinkage reducing agents as a temporary, consumable system that reacts during early hardening to provide shrinkage compensation without the long-term negative effects of aluminium powder. The calcium oxide/magnesium oxide serves as a short-term mechanism that achieves the compensation function without compromising final strength
2Object-affected harmful factors
If Portland cement is replaced by pozzolanic and/or latent hydraulic materials like GGBFS to reduce CO2 footprint, then environmental sustainability is improved, but shrinkage increases leading to cracking
Solution Approach 1:
The patent introduces calcium oxide or magnesium oxide as an intermediary substance that mediates between the environmental benefits of high GGBFS replacement and the dimensional stability requirements. This intermediary reacts with water to form calcium hydroxide or magnesium hydroxide, which then interacts with the organic shrinkage reducing agent to provide shrinkage compensation, allowing high GGBFS replacement without cracking
Solution Approach 2:
The patent creates a composite shrinkage compensation system combining inorganic calcium oxide or magnesium oxide with organic shrinkage reducing agents. This composite approach leverages the benefits of both material types: the inorganic component provides volume expansion through hydration, while the organic component controls and modulates the shrinkage reduction mechanism, achieving dimensional stability in high-GGBFS formulations
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 method effectively reduces shrinkage and expansion in cementitious materials, improving their dimensional stability and reducing the risk of cracking, particularly in applications requiring high slag content.
Implementation Method 1
aluminium powder and calcium oxide or magnesium oxide act synergistically in reducing the shrinkage of cementitious materials
Implementation Method 2
adding a shrinkage reducing agent which is an organic molecule to said cementitious composition
Data Source
AI summary
A method for the control of the shrinkage of cementitious materials, the method comprising the steps of providing a cementitious material, adding aluminium powder to the cementitious material, adding calcium oxide or magnesium oxide to the cementitious material, and adding a shrinkage reducing agent which is an organic molecule to the cementitious material. Cementitious grouts including aluminium powder, calcium oxide or magnesium oxide, and a shrinkage reducing agent which is an organic molecule.