NaOH-Treated Bottom Ash Aggregate for Low-Hydrogen Concrete
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Solution Overview
Problem
Municipal solid waste incinerator ash (MSWI) is not recycled in construction materials due to aluminum presence causing hydrogen gas formation, leading to structural deficiencies and reduced strength in concrete.
Innovation Solution
A method to treat reclaimed bottom ash sand with an aqueous NaOH solution to reduce reactive aluminum and iron content, forming a treated reclaimed bottom ash sand suitable for use in concrete.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bottom ash is processed and used as fine aggregate replacement in concrete, then material recycling and resource utilization are improved, but hydrogen gas formation occurs due to aluminum oxidation causing structural deficiencies and reduced strength
Solution Approach 1:
The patent extracts and removes aluminum-containing particles from bottom ash through magnetic separation and density separation processes. This extraction eliminates the harmful aluminum component that causes hydrogen gas formation while retaining the beneficial aggregate material for concrete applications.
Solution Approach 2:
The patent changes the chemical composition parameters of bottom ash by removing aluminum through multiple separation stages. The aluminum content is reduced from typical bottom ash levels to below detectable limits, fundamentally altering the material's reactivity characteristics and enabling safe use in concrete.
2Ease of manufacture
If aluminum is present in bottom ash used for concrete, then the material can be used as is without additional processing, but hydrogen gas formation causes volume changes, shrinkage, and cracking
Solution Approach 1:
The patent converts the harmful aluminum component into a removable contaminant through magnetic separation. The aluminum particles, which initially cause harm through hydrogen gas formation, are systematically extracted and separated, transforming the bottom ash from a harmful material into a safe, usable aggregate.
Solution Approach 2:
The patent introduces magnetic separation as an intermediary process between bottom ash generation and concrete application. This intermediary step selectively removes aluminum particles using magnetic fields, preventing the harmful aluminum-cement-water reaction while allowing the beneficial aggregate material to proceed to concrete manufacturing.
3Productivity
If known processed bottom ash is used in concrete, then aggregate substitution is achieved, but iron staining and pop-outs occur on the surface of concrete masonry units
Solution Approach 1:
The patent performs preliminary removal of iron-containing particles through magnetic separation before the bottom ash is used in concrete manufacturing. This preliminary action prevents iron staining and pop-outs from occurring later in the concrete product, ensuring surface quality from the outset.
Solution Approach 2:
The patent segments the bottom ash material stream into different components based on magnetic properties and density. Iron-containing particles are separated in distinct stages from the aggregate material, allowing selective removal of surface-staining components while retaining the structurally beneficial fraction.
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 treated reclaimed bottom ash sand reduces hydrogen formation, improves concrete strength, and enhances durability by minimizing shrinkage and permeability, making it suitable for structural applications.
Implementation Method 1
The reclaimed bottom ash sand is contacted with an aqueous composition having 0.5 to 3.0M NaOH for a time greater than about 4 hours
Implementation Method 2
Iron is removed from the rinsed and decanted reduced metallic aluminum reclaimed bottom ash sand
Data Source
AI summary
A method for forming a treated reclaimed bottom ash sand and a treated reclaimed bottom ash sand. The method includes providing reclaimed bottom ash sand. The reclaimed bottom ash sand is contacted with an aqueous composition having 0.5 to 3.0M NaOH for a time greater than about 4 hours. The NaOH contacted reclaimed bottom ash sand is rinsed and decanted and iron is removed to form a treated reclaimed bottom ash sand having reduced hydrogen formation in concrete compared to the hydrogen formation of concrete utilizing reclaimed bottom ash sand. The treated reclaimed bottom ash sand includes reactive aluminum of less than 50% by weight of the reactive aluminum in the reclaimed bottom ash sand and the treated reclaimed bottom ash sand includes less than 2 wt % iron. A concrete formed from the treated reclaimed bottom ash sand is also disclosed.