Reactive Lime and Magnesia Concrete Densification for Crack Control
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Solution Overview
Problem
Reactive-lime and reactive-magnesia industrial mineral residues, such as lime kiln dust and cement kiln dust, pose challenges in concrete formulations due to volumetric instability and thermal stresses caused by hydration, leading to cracking and reduced mechanical properties.
Innovation Solution
A hydrothermal densification process using CO2-containing gas and water at low temperatures to convert reactive lime and magnesia into hydrated calcium and magnesium carbonates, controlling the solid volume increase and microstructure development to enhance concrete strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If reactive-lime and reactive-magnesia industrial mineral residues are used in concrete formulations, then the quantity of substance and cementation are improved, but volumetric instability and thermal stresses cause cracking and reduced mechanical properties
Solution Approach 1:
The patent applies preliminary action by pre-hydrating reactive-lime and reactive-magnesia materials before incorporating them into concrete formulations. This pre-hydration treatment converts the highly reactive oxides into less reactive hydrated forms, reducing subsequent volumetric expansion and thermal stresses while maintaining the cementation benefits. The materials are treated under controlled conditions prior to concrete mixing to prevent harmful effects during curing.
2Volume of stationary object
If reactive-lime is hydrated in concrete, then cementation through solid volume increase is achieved, but extensive thermal stresses and volumetric expansion cause cracking
Solution Approach 1:
The patent applies preliminary action by pre-hydrating reactive-lime materials before incorporating them into concrete formulations. This pre-hydration treatment converts the highly reactive oxides into less reactive hydrated forms, reducing subsequent volumetric expansion and thermal stresses while maintaining the cementation benefits. The materials are treated under controlled conditions prior to concrete mixing to prevent harmful effects during curing.
Solution Approach 2:
The patent applies parameter changes by controlling the hydration process under specific temperature and pressure conditions. By adjusting these parameters during pre-hydration, the patent achieves controlled volume increase for cementation while minimizing thermal stresses and volumetric instability. The hydration is performed at controlled rates to prevent rapid expansion that would cause cracking.
3Stability of the object's composition
If pre-treatment or stabilization methods such as pre-hydration and pre-carbonation are applied, then volumetric stability is improved, but the complexity of the manufacturing process increases
Solution Approach 1:
The patent applies universality by developing a multi-functional pre-treatment process that combines hydration and carbonation steps into an integrated treatment system. This universal approach handles various reactive-lime and reactive-magnesia materials through a standardized process flow, achieving volumetric stability while minimizing the addition of separate complex treatment stages. The process can accommodate different input materials and produce stable outputs suitable for concrete applications.
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
This process allows the use of reactive alkaline-rich materials in concrete without pre-treatment, promoting carbonate mineral formation and densification, thereby improving concrete strength and durability.
Implementation Method 1
solidifying the concrete mixture by a hydrothermal densification process by contacting the concrete mixture with a CO2-containing gas and H2O
Implementation Method 2
Reactive-lime, also known as calcium oxide or CaO, expands when exposed to water and forms calcium hydroxide, which is also known as Ca(OH)2
Implementation Method 3
contacting the CKD and/or LKD with CO2-containing gas to form carbonated minerals
Implementation Method 4
promoting carbonate mineral formation and densification
Data Source
AI summary
Set forth herein are processes and reagents for using concrete mixtures to make concrete in which the concrete mixture includes reactive CaO or reactive MgO and hardens via hydrothermal densification process comprising hydration and carbonation reactions. In hydrothermal densification process water in the form of vapor, liquid, or steam and CO2 in the form of gaseous or liquid or a combination thereof are enforced in concrete pore space to form hydrated calcium carbonates (HCC) and/or hydrated magnesium carbonates and other hydration products to densify concrete microstructure. Certain processes and reagents are useful for adjusting the initial porosity of a concrete mixture. Certain processes and reagents are useful for regulating the rate of microstructure development of concrete during curing. Certain processes and reagents are useful for adjusting the initial porosity of a concrete mixture and also useful for regulating the rate of microstructure development of concrete during curing. The instant disclosure provides pathways for the utilization of lime/magnesia-containing industrial solid waste that otherwise cannot be generally used for concrete applications.