Alkali-Silica Mitigation Admixture Using Alternative Salts
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Solution Overview
Problem
Current strategies for mitigating alkali-silica reaction (ASR) in concrete, such as lithium-based admixtures and supplementary cementitious materials like fly ash, are costly and face supply challenges, necessitating a more reliable and cost-effective ASR inhibiting admixture.
Innovation Solution
A cementitious composition incorporating organic or inorganic salts like magnesium acetate, magnesium bromide, and calcium nitrate, combined with a slowly dissolving source of aluminum, to maintain a specific pH range in the pore solution, thereby inhibiting ASR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium-based admixtures are used to mitigate ASR, then ASR mitigation effectiveness is improved, but cost increases significantly
Solution Approach 1:
The patent replaces expensive lithium-based admixtures with cheaper alternative salts (such as magnesium acetate, calcium nitrate, or potassium formate) that can be readily obtained and applied. These alternative admixtures provide sufficient ASR mitigation at a fraction of the cost of lithium compounds, making the solution economically viable for large-scale concrete applications.
Solution Approach 2:
The patent changes the chemical composition parameters of the admixture by substituting lithium compounds with other salts containing different cations (magnesium, calcium, potassium) and various anions (acetate, nitrate, formate). This parameter change maintains the pH-modifying function while dramatically reducing cost.
2Reliability
If fly ash is used as supplementary cementitious material to mitigate ASR, then ASR mitigation is achieved, but supply reliability deteriorates due to declining availability
Solution Approach 1:
The patent extracts the essential ASR-mitigating function from fly ash and achieves it through alternative chemical mechanisms. Instead of relying on the pozzolanic reaction and pH modification provided by fly ash, the patent uses directly applied salt admixtures that modify pore solution pH through simple dissolution, bypassing the need for fly ash entirely.
Solution Approach 2:
The patent develops a universal admixture formulation using common salts that can be applied across different concrete types and applications without requiring the specific properties of fly ash. These salts provide ASR mitigation through pH control while being readily available from multiple sources, ensuring supply reliability.
3Reliability
If ground granulated blast furnace slag is used to mitigate ASR, then some ASR protection is provided, but effectiveness is reduced and supply is limited
Solution Approach 1:
The patent replaces slag, which provides only partial ASR protection and has limited availability, with cheaper and more effective salt-based admixtures. These admixtures directly address the root cause of ASR by modifying pore solution pH, providing superior and more reliable protection at lower cost and with greater availability.
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 proposed solution effectively reduces the occurrence of ASR, extending the service life of concrete structures and reducing maintenance and replacement costs by maintaining a stable pH in the concrete's pore solution, thus preventing silica gel expansion and associated damage.
Implementation Method 1
the organic or inorganic salt provides an aluminum, calcium, magnesium, or iron cation... to maintain a specific pH range in the pore solution
Implementation Method 2
The aluminum, calcium, magnesium, or iron salt reduces the pore solution pH of the concrete to between about 12.0 and 13.65
Data Source
AI summary
The present invention relates in part to an alkali-silica reaction mitigation admixture comprising an organic or inorganic salt that provides an aluminum, calcium, magnesium, or iron cation. The present invention also relates to a method of mitigating the alkali-silica reaction in a concrete product. The invention is further related to kits comprising the alkali-silica mitigation admixture and an instruction booklet.