Concrete production involves the use of small aggregates that must be ground via an energy-intensive process. By creating concrete from mining waste, industries can tackle both CO2 emissions and waste disposal.
The mining industry is based in the unsustainable extraction of natural resources, as mining operations pollute the environment, destroy natural habitats, and generate massive amounts of potentially hazardous waste.
2 main types of mining operations:
1 UNDERGROUND
• Tunneling underground
2 OPEN PIT
• Requires the stripping away of earth and rock to expose mineral resources
• Particularly fraught as it leads to significant land degradation, air pollution, and creation of rock wastes
• Waste from an open pit mine most typically placed in a dump
• Can occupy a significant amount of land
• Waste dumps must be maintained to avoid the leakage of materials
Waste, pollution and sustainability are also a major issue for the concrete industry. CO2 production is a particularly troubling issue, but research has shown that replacing traditional ingredients of concrete with waste materials could lead to significant environmental benefits.
… Negative Impacts of Mining and Concrete Production, but …
The Positive Impact:
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Currently, there are several efforts around the world focused on
• Developing more sustainable forms of concrete that could be made with waste materials
• Waste from mining operations is a particularly attractive option
• Mining waste is economically viable, as research has shown
• Its availability would help to meet the concrete production industry’s growing appetite for raw materials
Making Ultra-High-Performance Fiber-Reinforced Concrete from Mining Waste
Made through the inclusion of small steel fibers, Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) provides a high compressive strength and resistance to flexural stresses. A new study from a team of European-based researchers has revealed UHPFRC could be produced using sand waste from fluoride mining operations. The study team said they were able to reach these main conclusions:
Inclusion of sand wastes:
1—Leads to a more continuous distribution of particle size, ultimatlely
2—Reduced water requirements
Quality of sand waste was lower than that of the natural sand it’s meant to replace, but
3—Translated to superior mechanical performance in replacement ratios up to 70%
4—Boosted the consistency of fresh concrete, due to the inclusion of sand waste
5—Made mixing easier
6—Superior consistency led to
7—Greater compactness
8—Superior compressive strength
The research team noted that there was significant variability in their results. They theorized that this variability could be due to the varied distribution of reinforcing steel fibers.
A Study on General Feasibility
While UHPFRC study focused on a specific type of concrete, another recent study took a more general look at the viability of mining wastes in industrial concrete production.
New research from the Technical University of Denmark (DTU) has shown that up to 10% of the cement component in concrete can be effectively substituted with waste remnants of crushed mining ore—or, “mine tailings”. To reach their conclusion, the researchers conducted mechanical tests of mine tailings gathered from different operations all around the world. The study team found that:
• Substituting main tailings up to 10% in conventional concrete would not compromise the strength of the finished product.
• (Using calculations) using mine tailings would have a net positive impact on carbon emissions, even if wastes had to be shipped long distances for processing
• Further study would have to be done before mine tailings could be considered safe for use in concrete. Specifically, the chemical qualities of finished products need to be studied to ensure the substitution is safe over the course of the finished product’s full lifecycle.
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Sometimes, concrete structures fall into disrepair and are subsequently demolished. This waste concrete is then often reused in the creation of new structures and roadways.
Looking Ahead
The DTU research team said they are currently performing chemical analysis to determine if mine tailings can be used in an unprocessed form, or if they need to be treated. Mine tailings often include heavy metals and other potentially hazardous substances. If concrete made from mine tailings were to come in contact with water, it could potentially cause hazardous substances to leach out. If mine tailings do need to be treated prior to use, the researchers said there are a number of potential options, including the use of an electrochemical bath or electrochemical cleaning methods. The DTU scientists said they are analyzing various treatment methods to determine the most effective and most economical approach to processing mining wastes.
For the AZOBuild article titled “How Mining Waste Can be Utilized for Concrete Production”, please go to: https://www.azobuild.com/article.aspx?ArticleID=8427
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