A scientific study has revealed that lightweight volcanic aggregate can be used as a partial alternative to sand in concrete mixtures, helping to improve compressive, flexural, and tensile strength, while addressing the environmental issues of sand mining.
The study, which was recently published in Nature, reported that volcanic scoria is locally abundant in volcanic regions and offers favorable mechanical and thermal properties, making it a beneficial additive to the common building material.
The concrete industry accounts for around 8% of global planet-warming pollution, and it's the second-most-consumed material in the world behind water, the report explained.
At the same time, sand, which is a common aggregate used in concrete, is being overmined in many areas around the world where regulations don't constrain its removal.
According to the World Economic Forum, industrial sand mining and aggregate extraction – where the materials are being removed from riverbeds, lakes, oceans, and beaches for use in construction — are occurring faster than they can naturally be replenished.
When sand is mined from rivers and marine ecosystems, it "can lead to erosion, salination of aquifers, loss of protection against storm surges and impacts on biodiversity, which pose a threat to livelihoods through, among other things, water supply, food production, fisheries, or to the tourism industry," said the United Nations Environment Program.
Using the volcanic scoria alternative would reduce the demand for sand, while its use offers practical advantages, such as reducing the weight of the resulting concrete product.
The scientists tested volumetric substitution levels of scoria in sand mixtures at 35%, 50%, 70%, and 100% versus a control sample with just sand.
"The 35% replacement mix achieved the highest compressive strength at 43.6 MPa (megapascals), surpassing the control sample (39.6 MPa), while the 50% replacement yielded optimal flexural (4.88 MPa) and tensile strengths (3.36 MPa)," according to the study.
Levels higher than 50% resulted in diminishing returns, with reduced densities, making it workable only as a partial replacement for the volume of sand.
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Definitely 👍 Using scanning electron microscopy and X-ray diffractometry, the researchers confirmed that the glassy, porous structure of volcanic scoria also contributed to enhanced water resistance in concrete.
Given that the concrete industry has such a massive impact on the environment, whether through pollution generated by its production methods or the mining of raw materials used to make it, more sustainable methods and materials are urgently needed
Two of the world's major cement producers have begun investing in low-carbon alternatives, and green cement production is expanding through various avenues, including the addition of fly ash leftover from coal plants and carbon-capturing additives like olivine.
By 2050, the UN projects that up to 68% of the world's population will be living in cities, and construction will be needed to support that growth.
Through recycling and innovative material substitution, we have a chance at turning the notoriously pollution-heavy construction industry around so that we can provide more sustainable and resilient structures, while reducing the environmental costs involved.
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