Alkanolamine Accelerators for Slag Hydration
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Solution Overview
Problem
There is a need for alternative accelerators for steelmaking slags to enhance their hydraulic setting properties, particularly for Ground Granulated Blast Furnace Slag (GGBS) and Basic Oxygen Furnace (BOF) slag, that are safe to handle and effective in reducing environmental impact, as existing accelerators can be highly alkaline and lead to high dust emissions.
Innovation Solution
The use of alkanolamines, sugars, sugar acids, carboxylic acids, amino acids, sulfamic acid, glyoxal, acetylacetone, pyrocatechol, nitrilotri(methylphosphonic acid), etidronic acid, and mineral salts, or their mixtures, as accelerators for the reaction of steelmaking slag with water to increase compressive strength, improve rheology, and reduce water demand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional accelerators (very alkaline chemicals) are used to activate slag, then the hydraulic setting properties are improved, but safety and environmental performance deteriorate due to high alkalinity and dust emissions
Solution Approach 1:
The patent changes the chemical parameters of the accelerator from very alkaline chemicals to compounds with pH between 4-10, specifically using carboxylic acids, sulfonic acids, and their salts. This parameter change maintains the activation capability while dramatically reducing alkalinity and associated harmful effects like dust emissions and environmental impact
Solution Approach 2:
The patent employs readily available, low-cost compounds such as food industry by-products (lactic acid, citric acid) and common chemical salts that can be easily handled and applied. These substitutes replace expensive and hazardous traditional accelerators, making the process safer and more environmentally friendly without compromising performance
2Object-generated harmful factors
If slag is used as a cement replacement to reduce environmental footprint, then CO2 emissions are reduced, but the material requires activation which traditionally involves harmful chemicals
Solution Approach 1:
The patent introduces benign intermediary substances (carboxylic acids, sulfonic acids, and their salts) that mediate between the slag and water reaction. These intermediaries activate the slag's hydraulic properties through safe chemical mechanisms, replacing the need for harmful traditional accelerators and enabling slag to function as an effective cement substitute
Solution Approach 2:
The patent converts potentially harmful activation requirements into a benefit by using safe, environmentally friendly chemicals that can be readily handled. The activation process, which could have been a source of harm with traditional chemicals, becomes an opportunity to demonstrate sustainable construction chemistry using common, low-hazard substances
3Strength
If high alkaline accelerators are used to achieve rapid strength development, then early strength is improved, but handling safety and worker protection deteriorate
Solution Approach 1:
The patent changes the pH parameter range of accelerators from highly alkaline (pH > 12) to a safer range of pH 4-10, while maintaining effectiveness through alternative chemical mechanisms involving carboxylic acids, sulfonic acids, and their salts. This enables early strength development without the safety hazards of handling concentrated strong bases
4Reliability
If conventional activators are used for slag activation, then hydraulic activity is achieved, but the complexity of material selection and compatibility increases
Solution Approach 1:
The patent identifies a universal class of compounds (carboxylic acids, sulfonic acids, and their salts) that can activate multiple types of slag (GGBS, BOF slag, converter slag) with consistent performance. This universal approach simplifies material selection compared to traditional activators that require specific matching for different slag types, reducing complexity while maintaining reliable hydraulic activity
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
These accelerators significantly enhance the compressive strength, reduce viscosity, and lower water demand of steelmaking slag-based mixtures, while being safer and less alkaline, thus offering a more environmentally friendly alternative to traditional cement-based binders.
Implementation Method 1
WO 2020/188070 (Tata Steel) discloses a slag mixture with a chelating agent chosen from polycarboxylic acids, most preferably citrates to act as an activating agent
Implementation Method 2
WO 2019/110134 (Ecocem) discloses slag-based binders with an activator for the slag/water reaction selected from alkali metal carbonates, mineral wastes, silica fume, rice husk ash, and/or phosphoric acid. Additionally, chelating agents are disclosed which are chosen from phosphonates, phosphates, carboxylates, and amines.
Implementation Method 3
The present invention thus relates to the use of an accelerator for the reaction of steelmaking slag with water... to increase compressive strength, improve rheology, and reduce water demand.
Implementation Method 4
Accelerators for the reaction of steelmaking slag with water... binders comprising steelmaking slag and said accelerators and their use in construction materials.
Data Source
AI summary
Accelerators and binders including steelmaking slag and their use in construction materials, wherein the accelerators for the reaction of steelmaking slag with water are being selected from the group consisting of alkanolamines, reducing agents, sugars, sugar acids, carboxylic acids or their salts, amino acids or their salts, sulfamic acid, glyoxal, acetylacetone, pyrocatechol, nitrilotri(methylphosphonic acid), etidronic acid, mineral salts, or mixtures thereof.