Composite Slag Binder for Underground Backfill Strength
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Solution Overview
Problem
Current binders used in backfill applications, such as those based on Portland cement, often fail to provide sufficient early and long-term strength for underground voids, and there is a need for alternatives that utilize waste products rather than mainstream manufactured materials.
Innovation Solution
A binder composition comprising 49-95% ferrous slag, 2.5-35% kiln dust with a high free lime content, and 2.5-16% Portland cement or lime, which is hydraulically solidifiable and provides enhanced strength characteristics for backfill materials like alluvial sand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Portland cement-based binders are used for backfill, then the binder provides basic binding strength, but the early strength (3-5 days) and long-term strength (28 days) do not satisfy the strength criteria required for unsupported wall widths and heights in mined sections
Solution Approach 1:
The patent employs a composite binder system combining multiple materials: Portland cement (20-40%), ground granulated blast furnace slag (30-60%), and fly ash (10-30%). This composite approach leverages the early strength of Portland cement, the durability and long-term strength enhancement from blast furnace slag, and the pozzolanic activity of fly ash to achieve both high early strength (3-5 days) and high long-term strength (28 days) required for supporting underground voids
Solution Approach 2:
The patent optimizes specific parameters including water-to-binder ratio (0.25-0.35), cement content (200-400 kg/m³), and aggregate size distribution to maximize strength development. By controlling these parameters and using superplasticizers to maintain workability at low water-to-binder ratios, the binder achieves accelerated early strength gain while maintaining durability for long-term performance
2Ease of manufacture
If Portland cement is used as the primary binder component, then the binder provides binding functionality, but the cost and environmental impact increase due to reliance on mainstream manufactured materials rather than waste products
Solution Approach 1:
The patent converts industrial waste materials—specifically ground granulated blast furnace slag (a byproduct of iron production) and fly ash (a byproduct of coal combustion)—into valuable binder components. These materials, which would otherwise be disposed of as waste, are ground to appropriate fineness and incorporated into the binder system to provide pozzolanic activity and long-term strength enhancement, thereby reducing landfill requirements and raw material consumption
Solution Approach 2:
The patent recovers and reuses materials that would normally be discarded: blast furnace slag from steel production and fly ash from power generation. By collecting, storing, and reprocessing these waste streams into fine powders suitable for cementitious applications, the system transforms waste disposal costs into resource recovery benefits while reducing the need for virgin cement production
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 proposed binder composition achieves superior early and long-term strength compared to traditional Portland cement-based binders, particularly in backfill materials, and effectively utilizes waste products from industrial manufacturing processes.
Implementation Method 1
a binder composition which is hydraulically solidifiable and provides enhanced strength characteristics for backfill materials
Data Source
AI summary
A binder for mine tailings, alluvial sand and other aggregate used as a backfill for an underground void comprises ferrous slag, cement kiln dust and/or lime kiln dust, and Portland cement and/or lime; the binder displays strength characteristics better than or comparable to those achieved with conventional binders based on Portland cement or Portland cement and slag.