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Self-healing concrete

June 25, 2025 By EarthWise Leave a Comment

Concrete is the most widely used building material on Earth. It has a dangerous and costly flaw: it cracks easily. Cracks in concrete can lead to inconvenient damage or to catastrophic structural failures such as collapses of buildings, bridges, or highways.

Concrete is made by mixing crushed stone and sand with powdered clay and limestone and adding water. The mixture hardens and once set becomes extremely strong. However, natural forces like freeze-thaw cycles, drying shrinkage, and heavy loads can cause cracks. Even very tiny cracks can allow liquids and gases to seep into embedded steel reinforcements causing corrosion and weakness.

For over 30 years, researchers have investigated microbe-mediated self-healing concrete. It involves introducing microbial healing agents into cracks and injecting nutrients for the healing agents to produce repair materials. It is not a very practical solution.

Researchers at Texas A&M University have developed a technique inspired by the behavior of lichen systems. Their system, like lichen, uses a combination of cyanobacteria which turns air and sunlight into food, and filamentous fungi, which produces minerals that seal the cracks.

In lab tests, the paired microbes were able to grow and produce crack-filling minerals even in challenging environments such as concrete. If it is possible to produce concrete that can heal itself, it would significantly reduce maintenance costs, extend its longevity, and even protect lives through increased safety.

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Cracking the Code: Deciphering How Concrete Can Heal Itself

Photo, posted May 21, 2009, courtesy of DesignMag via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Carbon-Negative Concrete | Earth Wise

June 6, 2023 By EarthWise Leave a Comment

Concrete is a mainstay of modern civilization. The world produces more than 4 billion tons of it each year and the process requires high temperatures, mostly obtained by burning fossil fuels. The chemical reactions that produce concrete also produce large amounts of carbon dioxide. In all, cement production is responsible for about 8% of total global carbon emissions by human activities.

This situation is the impetus for a wide range of research activities aimed at reducing the environmental impact of concrete production. Researchers at Washington State University have recently developed a way of making carbon-negative concrete: a recipe for concrete that absorbs large amounts of carbon dioxide.

There have been attempts in the past to add biochar to concrete. Biochar is a type of charcoal made from organic waste that sucks up carbon dioxide from the air. In earlier attempts, even adding 3% of biochar would dramatically reduce the strength of the concrete.

The WSU researchers found that treating biochar with concrete washout wastewater makes it possible to add much more biochar to concrete without reducing its strength. Mixing it with biochar adds calcium, which induces the formation of the mineral calcite, which in turn strengthens the concrete.

The researchers were able to add up to 30% biochar to their cement mixture. Within a month, the resultant concrete was comparable in strength to ordinary concrete. But at the same time, the biochar was able to absorb up to 23% of its weight in carbon dioxide from the air. The new concrete is potentially the most environmentally friendly concrete ever developed.

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Researchers develop carbon-negative concrete

Photo, posted January 31, 2012, courtesy of Michael J. Nevins / U.S. Army Corps of Engineers via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

A Pesticide From Beer | Earth Wise

July 23, 2021 By EarthWise Leave a Comment

Researchers from the Neiker Basque Institute for Agricultural Research and Development in Spain have demonstrated that a combination of rapeseed cake and beer bagasse can be used to reduce populations of soil parasites and increase crop yields.

Beer bagasse is spent brewers’ grain – the stuff that is left over after the beer is made. Beer brewing generates substantial amounts of by-products, including large amounts of spent grain. It already has some practical uses, including as a feedstock for biofuel, as a food additive, and it even has some medical uses. But the new research has shown that the bagasse can be the basis for a biodisinfestation treatment to be used in agriculture. The aim is to disinfect soils, protect soil microorganisms, and increase crop yields.

The actual material studied was a mixture of beer bagasse, rapeseed cake, and a generous amount of fresh cow manure. The high nitrogen content of the mixture promotes the activity of beneficial microorganisms in the soil, which helps to break down organic matter and kill off nematodes and other parasites that damage crops.

Nematodes are common parasites that can penetrate plant roots to lay their eggs, which damages the root and prevents the plants from absorbing nutrients effectively. Application of the bagasse-based mixture over 12 months increased crop yields by 15% and boosted healthy soil microbes.

The study demonstrated that agricultural byproducts can be an effective treatment for root-knot nematodes and other soil parasites, increase crop yields, and help promote sustainable food systems to reduce waste from the agricultural industry. The researchers hope to identify other potential organic treatments for tackling soil parasite problems.

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Beer byproduct mixed with manure proves an excellent organic pesticide

Photo, posted July 1, 2011, courtesy of Quinn Dombrowski via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Getting Value From Plastic Waste | Earth Wise

November 30, 2020 By EarthWise Leave a Comment

To date, the world has produced more than five billion tons of plastic and is making more all the time. Based on the way things are currently done, most of that will end up in landfills or in the natural environment. By 2050, the amount of plastic is expected to exceed 13 billion tons. This is one of the world’s biggest environmental problems.

Recently, an international collaboration by universities and institutions in the UK, China, and Saudi Arabia has developed a method of converting plastic waste into hydrogen gas and high-value solid carbon.

The technique was achieved with a new type of catalysis that uses microwaves to activate catalyst particles that effectively strip hydrogen from plastic polymers. The work was recently published in the journal Nature Catalysis and details how the researchers mixed mechanically pulverized plastic particles with a microwave-susceptor catalyst of iron oxide and aluminum oxide. That mixture was then subjected to microwave treatment and yielded a large volume of hydrogen gas and a residue of carbonaceous material, most of which was identified as carbon nanotubes.

The process is more rapid than most methods for dealing with plastic waste and can extract over 97% of the hydrogen in plastic without producing any carbon dioxide emissions.

The new method represents an attractive potential solution to the problem of plastic waste. Instead of polluting the planet, plastics could become a valuable feedstock for producing clean hydrogen fuel as well as valuable carbon materials. Proponents of the so-called hydrogen economy have continued to seek a green and economical way to produce hydrogen. This new work might be just what they are looking for.

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Turning plastic waste into hydrogen and high-value carbons

Photo, posted April 21, 2007, courtesy of Redwin Law via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.