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Created for fast, low-cost and on-site analysis of concrete structures, the material was developed by researchers at the University of São Paulo’s Physics Institute (IF-USP) in Brazil and the University of Leuven in Belgium.
Concrete is fundamental to the foundations and structures of buildings, roads, dams and bridges, but it has a limited service life of about 50 years. Constant absorption of water, salts and gases from the atmosphere causes acidification, leading to corrosion of steel reinforcing bars in slabs, columns and other structural elements, and drastically reducing their weight-bearing capacity.
The lifetime of concrete can be extended through preventive measures such as the addition of protective layers that hinder penetration of carbon dioxide into exposed surfaces. If this intervention is to be timely, however, workers need to be able to check the degree of deterioration.
The main challenge facing engineers who inspect concrete in buildings and other structures is that drilling to remove samples and analysis in a laboratory is labour-intensive and costly, as well as being complex in places that are hard to access. It can also be hazardous, since drilling can cause alterations in the structure and further weaken the concrete if it is already degraded, especially if the procedure is not carried out correctly.
In the new study, the researchers developed a catalyst based on layered double hydroxide (LDH), also known as anionic clay, to measure the degree of deterioration in concrete. They added trivalent europium (Eu3+) to produce orange-to-red luminescence.
Laboratory tests showed that when the material was exposed to ultraviolet light (UV), its luminescence changed colour according to the amount of carbonate it had absorbed. This effect can be used to detect deterioration in concrete, the researchers said – the greater the red shift, the more carbonate is present and the more degraded the concrete.
“The main advance is that the material can help determine in real time how the concrete present in a structure is deteriorating, and when the structure will require maintenance, without any need for drilling or waiting for laboratory analysis. This contributes to more agile decision-making, facilitates preventative maintenance, and helps avoid accidents that can cost lives and cause considerable economic damage,” said Alysson Ferreira Morais, first author of the article.
As well as a potential boost for building safety, the new method could offer cost and carbon reduction benefits.
“The longer buildings last, the less need to invest in new structures, and the more the construction industry contributes to the effort to cut greenhouse gas emissions, 8% of which come from the industry globally, owing to production of concrete and construction itself,” said Danilo Mustafa, an author of the article and professor at IF-USP.
According to the team, the next step will involve developing a sensor that detects the luminescent material, and testing it under real-world conditions to verify specific factors such as weatherability and stability.
Researchers at the University of Kiel in Germany also took part in the study, which was supported by the São Paulo Research Foundation (FAPESP), the Brazilian Ministry of Education’s Coordination for the Improvement of Higher Education Personnel, the European Research Council, and the European Union’s Horizon Europe Programme.
The work was published in Chemical Communications.
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