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Concrete Strengthened with 'Sewage-Enhanced' Steel Slag

Friday, May 15, 2020

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Engineering researchers from RMIT University have recently explored a zero-waste approach that both treats wastewater and makes stronger concrete.

The study, “Recycling steel slag from municipal wastewater treatment plants into concrete applications – A step towards circular economy” has since been published in Resources, Conservation and Recycling by co-authors Professor Sujeeva Setunge and Professor Kevin Zhang from RMIT’s School of Engineering.

The Research

In the study, researchers took steel slag used to absorb contaminants like phosphate, magnesium, iron, calcium, silica and aluminum, among others found in wastewater, and upcycled the remaining slag as an aggregate material for concrete.

RMIT University

Engineering researchers from RMIT University have recently explored a zero-waste approach that both treats wastewater and makes stronger concrete.

“The global steel making industry produces over 130 million tons of steel slag every year,” said water engineer Biplob Pramanik. “A lot of this by-product already goes into concrete, but we’re missing the opportunity to wring out the full benefits of this material."

In taking the steel slag used in wastewater treatment, civil and water engineers found that the new chemical properties caused that slag to perform better in concrete, making the new form stronger than its traditional steel slag counter-version.

“While there are technical challenges to overcome, we hope this research moves us one step closer to the ultimate goal of an integrated, no-waste approach to all our raw materials and by-products,” said Pramanik. He adds that the study is the first to investigate potential applications for “sewage-enhanced” slag in construction material.

Civil engineer Rajeev Roychand chimed in as well, saying that while the study is promising, a larger scale of the research needed to be conducted so long-term mechanical and durability properties of enhanced slag could be determined.

“Steel slag is currently not in widespread use in the wastewater treatment industry—just one plant based in New Zealand uses this by-product in its treatment approach,” he said.

“But there is great potential here for three industries to work together – steel making, wastewater treatment and construction—and reap the maximum benefits of this by-product.”

Other Recycled Concrete Studies

In 2016, researchers, led by Yahya “Gino” Kurama, a professor of civil and environmental engineering and earth sciences at the University of Notre Dame looked into the feasibility of recycling concrete from U.S. infrastructure projects into material for use in new buildings and bridges.

At the time, the team reported that the biggest challenge in using recycled concrete in construction was the uncertainty about quality. Variability in the recycled material’s properties would have an impact on the strength, stiffness and durability of reinforced concrete structures.

The following year, M.A.G. dos Anjos, A.T.C. Sales and N. Andrade, all of the Department of Civil Engineering at Federal University of Sergipe, in Brazil presented a paper consisting of experimental data that the authors say show blasted copper slag as a “technically viable” and safe material to use as fine aggregate in concretes made with Portland cement.

The research built on past work done by other researchers looking at copper slag—straight from the smelter or post-blasting—as a potential fine aggregate, while the new study looked specifically at slag that’s already been used as blasting abrasive media. In addition, the study also looked at the slags use as a substitute for a significant portion of the aggregate in concrete mixtures, evaluating a number of properties of the concrete that results.

In February 2019, researchers from the Department of Civil and Structural Engineering at The University of Sheffield (South Yorkshire, England) reportedly found a new way to protecting concrete from fire damage using recycled tires.

And in November, Drexel University researchers developed an additive out of coal ash that was reported to both help make concrete more durable and crack-free. According to the university, the additive can also shorten the time it takes for concrete to harden. In order for the building material to reach its greatest durability, the cement needs to mix thoroughly with water during the curing process.

The material the team developed, known as spherical porous reactive aggregate, or SPoRA for short, was produced by combining ash with chemicals that help with aggregate sintering and bonding, then forming the material into tiny spheres and baking them at 1,160 degrees Celsius for a short period. The end result can hold almost half its weight in water and can also release the liquid into the cementing mix at a regular rate. Testing also indicated that two types of SPoRA performed better than more traditional aggregates like shale, clay and slate and foamed glass, in terms of shape, porousness, relative weight and ability to absorb and release water.


Tagged categories: AF; Colleges and Universities; concrete; Project Management; Quality Control; Quality control; Research and development; Steel Slag; Wastewater Plants

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