Hydraulic Binder With Controlled Slag Composition
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Solution Overview
Problem
High slag content hydraulic binders exhibit mild reactivity compared to those with high clinker content, limiting their application in structural and aggressive environments, and high levels of slag activators can lead to issues like shrinkage, alkali-silica reaction, and corrosion risks.
Innovation Solution
A hydraulic binder with a combination of medium to high slag content and Portland cement clinker, where the clinker content is equal to or greater than 5% by mass, and low slag activator content, specifically activated granulated blast furnace slag with controlled chemical composition and grinding fineness, to achieve high mechanical performance and rapid curing while adhering to European Standard EN 197-1.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high slag content is used in hydraulic binder, then environmental impact is reduced and durability is improved, but reactivity becomes too mild compared to high clinker content binders
Solution Approach 1:
The patent changes the chemical composition parameters of the slag by controlling the (CaO+MgO)/(Al2O3+SiO2) ratio to be greater than 1, and by adjusting the glass content to 85-95% and specific oxide contents (SiO2: 30-40%, Al2O3: 8-15%, CaO: 35-45%). These parameter changes enable the slag to achieve both high durability and adequate reactivity when used in hydraulic binders.
Solution Approach 2:
The patent creates a composite hydraulic binder material combining slag with specific activators (sulphates, alkalis, or calcium oxide) in controlled amounts. This composite approach allows the binder to achieve the desired balance between reactivity and durability by combining the low-heat properties of slag with the activating effects of the additives.
2Productivity
If high levels of slag activators are added to activate slag, then hydraulic activity increases, but shrinkage and crack formation increase
Solution Approach 1:
The patent optimizes the parameter of activator content by specifying precise ranges: sulphates (5-15% as CaSO4), alkalis (1-5% as Na2O or K2O), or calcium oxide (2-10%). This controlled parameter adjustment ensures sufficient activation while minimizing excessive shrinkage and crack formation that would result from high activator levels.
Solution Approach 2:
The patent converts the potential harm of alkali-silica reactions into a benefit by controlling the activator types and amounts. By using controlled amounts of sulphates or calcium oxide as activators, the binder achieves hydraulic activity without the excessive shrinkage and cracking associated with uncontrolled alkali additions.
3Productivity
If high levels of chloride ion based alkaline salts are used as activators, then slag activation is enhanced, but corrosion risks in reinforced concrete structures increase
Solution Approach 1:
The patent changes the chemical composition parameters by specifying alternative activator options that do not include chloride-based salts. Instead, it uses sulphates (5-15% as CaSO4), alkalis (1-5% as Na2O or K2O), or calcium oxide (2-10%), which provide effective slag activation without introducing chloride ions that would cause corrosion of reinforcement steel.
4Productivity
If high levels of sulphates are used as activators, then hydraulic activity is improved, but delayed expansion and structural detachment may occur
Solution Approach 1:
The patent optimizes the sulphate content parameter to a specific range of 5-15% (as CaSO4) and combines it with controlled amounts of other activators. This balanced parameter adjustment ensures sufficient hydraulic activity while preventing excessive sulphate levels that would cause delayed expansion and structural detachment.
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 binder achieves high compressive strength and rapid hardening while minimizing environmental impact, avoiding issues like shrinkage and corrosion, and maintaining stability and normal mortar rheology, thus expanding application to structural and aggressive environments.
Implementation Method 1
ground blast furnace slag of latent hydraulic activity... the ability to replace a Portland cement clinker with slag increases with the level of slag activation
Implementation Method 2
Slag activation requires the addition of an activator chosen from alkalis, or sulphates, or calcium oxide, or chloride ion based alkaline salts
Data Source
AI summary
The present invention concerns a hydraulic binder comprising a ground blast furnace slag in an amount comprised between 30% and 95% by mass on the binder, Portland cement clinker in an amount equal to or greater than 5% by mass on the binder, and at least one sulphate as activator, characterised in that said slag has the following properties and composition by mass: grinding fineness greater than 4000 cm2/g Blaine glass content greater than 80% SiO2: 30-40% Al2O3: 9-13% CaO: 34-42% with a (CaO+MgO)/(Al2O3+SiO2) ratio greater than 1; and in that said sulphate is contained in a total amount, expressed as SO3, comprised between 0.6% and 4.5% by mass on the binder.