Glass Cullet Binder for Autoclaved Aerated Concrete Strength
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Solution Overview
Problem
The formation of tobermorite crystals during the production of autoclaved aerated concrete leads to increased microporosity, limiting the compressive strength of the final product, which does not meet the required standards for mechanical properties.
Innovation Solution
A mixture with a binder having a specific surface area greater than 2500 cm²/g and containing a glass phase with over 90% weight content, along with silica and calcium sources, is used to inhibit tobermorite crystallization, resulting in an amorphous C-S-H phase matrix with increased packing density and strength, incorporating glass cullet and alkali oxides to enhance reactivity and reduce porosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If tobermorite crystals form during hydrothermal treatment, then the concrete structure is formed, but microporosity increases and compressive strength decreases
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by incorporating glass cullet with high glass phase content (over 90% by weight) and specific oxide ratios (SiO2: 65-75%, Al2O3: 15-25%, CaO: 8-15%, Na2O: 5-15%, K2O: 3-8%). This compositional change prevents tobermorite crystallization and promotes formation of an amorphous C-S-H phase matrix, thereby reducing microporosity and increasing compressive strength while maintaining structural stability
Solution Approach 2:
The invention creates a composite binder system combining ground glass cullet (providing glass phase), silica source, and calcium source. This composite material formulation produces a heterogeneous amorphous C-S-H phase matrix that prevents crystalline tobermorite formation while maintaining structural integrity and enhancing mechanical properties through the synergistic interaction of different phases
2Stability of the object's composition
If traditional binder composition is used, then tobermorite crystallization occurs, but compressive strength is insufficient
Solution Approach 1:
The invention fundamentally changes the binder composition from traditional crystalline-forming materials to a glass-phase-dominated system with specific oxide ratios. The high glass phase content (over 90%) and controlled alkali oxide content (Na2O: 5-15%, K2O: 3-8%) create a chemical environment that favors amorphous C-S-H phase formation over tobermorite crystallization, thereby achieving both structural stability and high compressive strength
Solution Approach 2:
The invention converts the typically harmful effect of microporosity (which reduces strength) into a benefit by preventing tobermorite crystallization. The amorphous C-S-H phase matrix that forms instead creates a denser, less porous structure. Additionally, the ground glass cullet itself, which would normally be considered waste material, becomes a valuable reactive component that enhances both strength and durability
3Strength
If glass cullet with high glass phase content is used, then reactivity increases and porosity reduces, but energy consumption for grinding increases
Solution Approach 1:
The invention optimizes the specific surface area parameter of the ground glass cullet to a range of 1500-4000 cm²/g, balancing reactivity requirements with energy consumption. This parameter optimization ensures sufficient surface area for hydrothermal reactions and strong interfacial bonding while avoiding excessive grinding energy input. The specific oxide composition (SiO2: 65-75%, Al2O3: 15-25%) also contributes to enhanced reactivity at moderate surface areas
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 approach results in autoclaved aerated concrete with compressive strength compliant with industry standards, reduced energy consumption, and the potential for using waste materials, thereby enhancing mechanical properties and reducing environmental impact.
Implementation Method 1
inhibit tobermorite crystallization, resulting in an amorphous C-S-H phase matrix
Implementation Method 2
the main product of the hydrothermal reaction of which is not crystalline tobermorite, but amorphous C-S-H phase
Implementation Method 3
the introduction of the raw material containing more than 90% by weight of the glass phase and at least 10% by weight of alkali (in particular Na + and/or K +)
Implementation Method 4
in the process of hydrothermal treatment, in autoclaves at the temperature of 180-200°C and under the saturated steam pressure reaching 1.1-1.3 MPa
Data Source
Figure 1~2
AI summary
A mixture for the production of autoclaved aerated concrete, containing a binder with a specific surface area greater than 2500 cm2/g according to Blaine and possibly a microaggregate with a specific surface area of 1500 - 2500 cm2/g according to Blaine, as well as water and preferably additives such as blowing agents and surfactants, the binder comprising a silica source in the form of a component or mixture of components selected from the group consisting of quartz sand, fossil fuel fly ash, blast furnace slag, and the binder also comprising a calcium source in the form of a component or mixture of components selected from the group consisting of lime, fossil fuel fly ash, blast furnace slag, cement and gypsum, and the molar ratio of the amount of calcium source to the amount of silica source in the mixture is 0.25 - 0.95, characterized in that the mixture contains 10-90% by weight of raw material with glass phase content over 90% by weight, over 10% by weight of alkali in the form of Na2O and K2O oxides and over 60% by weight of SiO2. The latter raw material is preferably glass cullet.