Sulfate Resistant Cement Composition
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Solution Overview
Problem
Existing cement compositions using high alumina ground granulated blast furnace slag and Portland cement face challenges in sulfate resistance and initial setting speed, leading to issues like concrete expansion and delayed setting, which limits their application in structures exposed to sulfate-containing soils or seawater.
Innovation Solution
A mixed cement composition with a ratio of 10 to 60% ground granulated blast furnace slag and 2 to 4% plaster, having a specific surface area of 7000 cm2/g or more, is used, along with Portland cement with controlled calcium aluminate content, to enhance sulfate resistance and setting performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high alumina ground granulated blast furnace slag is used to improve final strength, then final strength is improved, but initial setting speed decreases and sulfate resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the alumina content of ground granulated blast furnace slag within 12-17 mass% and the mixture ratio within 20-60 mass%, along with controlling calcium aluminate content in Portland cement to 8 mass% or less. These parameter optimizations enable the cement to achieve both adequate initial setting speed and high final strength, resolving the contradiction between early strength development and later strength potential.
2Strength
If high alumina ground granulated blast furnace slag is used to improve final strength, then final strength is improved, but sulfate resistance deteriorates
Solution Approach 1:
The patent resolves the sulfate resistance issue through parameter changes by limiting alumina content to 12-17 mass% (avoiding excessive alumina that forms expansive ettringite), controlling the blast furnace slag ratio to 20-60 mass%, and limiting calcium aluminate in Portland cement to 8 mass% or less. These controlled parameters prevent sulfate attack while preserving the high final strength characteristics.
Solution Approach 2:
The patent creates a composite cement system combining Portland cement with controlled calcium aluminate content and ground granulated blast furnace slag with optimized alumina content. This composite material approach balances the high strength benefits of high alumina slag with the sulfate resistance requirements by carefully controlling the composition and ratios of constituent materials.
3Reliability
If Portland cement with low calcium aluminate content is used to improve sulfate resistance, then sulfate resistance is improved, but initial strength decreases
Solution Approach 1:
The patent merges Portland cement with controlled low calcium aluminate content (8 mass% or less) with ground granulated blast furnace slag containing 12-17 mass% alumina in a 40-80 mass% to 20-60 mass% ratio. This combination allows the system to achieve sulfate resistance through low calcium aluminate content while compensating for reduced initial strength through the synergistic contribution of the optimized blast furnace slag, maintaining both sulfate resistance and adequate initial strength.
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 solution effectively prevents abnormal concrete expansion and ensures suitable setting characteristics, achieving sulfate resistance performance comparable to high sulfate resistance Portland cement while maintaining initial and final strength equivalent to conventional cement.
Implementation Method 1
If the water mixed in is alkali, the CaO and Al2O3 contained in the ground granulated blast furnace slag leach out from the powder into the water causing a hydration reaction contributing to the curing of the cement structure.
Implementation Method 2
If the water mixed in is alkali, the CaO and Al2O3 contained in the ground granulated blast furnace slag leach out from the powder into the water causing a hydration reaction contributing to the curing of the cement structure.
Data Source
AI summary
Mixed cement containing mainly ground granulated blast furnace slag with an alumina ratio of 12 to 17.5 mass % and Portland cement, wherein a ratio of mixture of the ground granulated blast furnace slag is made 10 to 60 mass % and wherein plaster having a specific surface area of 7000 cm2/g or more is mixed in by a ratio of 2 to 4 mass % converted to SO3 mass. By using this mixed cement as a concrete material, it is possible to suppress expansion of the concrete even if in contact with soil containing residual sulfates over a long period.