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Leaching from granular cement-based materials during infiltration/wetting coupled with freezing and thawing
F Sanchez1, M K Langley White, A Hoang
1Department of Civil & Environmental Engineering, Vanderbilt University, Nashville, TN 37235, USA. florence.sanchez@vanderbilt.edu
Journal of Environmental Management
|April 29, 2008
Summary
Recycled materials in highways face freeze/thaw cycles, impacting constituent leaching. Self-cementing effects reduce leaching over time, especially in flow-around scenarios, but moisture content is key in flow-through conditions.
Area of Science:
- Environmental Science
- Geotechnical Engineering
- Materials Science
Background:
- Secondary materials are increasingly used as substitutes for natural aggregates in highway construction due to economic and engineering benefits.
- Recycled materials in infrastructure are subjected to environmental stressors like freeze/thaw cycles and wetting, leading to potential constituent leaching and environmental impact.
- Understanding leaching behavior is crucial for assessing the long-term environmental performance of secondary materials in highway applications.
Purpose of the Study:
- To investigate the effects of freeze/thaw (F/T) cycles on the leaching behavior of constituents from laboratory-formulated granular cement-based materials.
- To evaluate leaching under different environmental conditions, including flow-through and flow-around scenarios, simulating highway environments.
- To determine the influence of moisture content at freezing, number of F/T cycles, and material size on leaching.
Main Methods:
- Laboratory formulation of granular cement-based materials.
- Exposure of materials to controlled freeze/thaw cycles under both flow-through and flow-around conditions.
- Analysis of major and minor constituent leaching, considering variations in moisture content, F/T cycles, and material size.
Main Results:
- Freeze/thaw exposure and subsequent wetting led to material consolidation and self-cementing.
- In flow-around scenarios, constituent release decreased with increased F/T cycles and time.
- In flow-through scenarios, moisture content at freezing significantly influenced leaching, with initial increases due to cracks/redistribution followed by decreases from self-cementing.
Conclusions:
- Freeze/thaw cycles and wetting promote self-cementing in granular cement-based materials, influencing constituent leaching.
- Leaching behavior is dependent on the specific environmental pathway (flow-through vs. flow-around) and material properties.
- Optimizing moisture content during freezing is critical for managing constituent release in flow-through leaching scenarios involving recycled highway materials.
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