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Old Posted Aug 25, 2017, 6:56 PM
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How Mushrooms Could Repair Our Crumbling Infrastructure

How Mushrooms Could Repair Our Crumbling Infrastructure

August 24, 2017

Read More: https://www.technologyreview.com/s/6...nfrastructure/


A better, cheaper way to repair concrete is desperately needed. Enter Ning Zhang at Rutgers University in New Jersey and few pals, who say they have discovered a secret ingredient that could one day keep the nation moving by repairing crumbling concrete automatically. This new ingredient? Mushrooms.

- Materials scientists have long hoped to find a secret sauce that helps concrete repair itself. One idea is to fill concrete with polymer fibers containing resin that leaks out to fills cracks. That looked promising for a while, but it turns out that concrete and resin have different thermal expansion properties, among others, which can sometimes make cracks worse. A better filler for cracks is calcium carbonate, because it bonds well with concrete and has similar structural properties. Various bacteria produce minerals of this kind but also release other by-products, including copious amounts of nitrogen products like ammonia. And this can damage roads and the environment.

- So materials scientists need another option, and today Zhang and co say they’ve found it in the form of a fungus called Trichoderma reesei. It can germinate in a wide range of conditions, forming a fibrous fungus that promotes the formation of calcium carbonate. Their idea is that fungal spores are added to the concrete when it is mixed and then lie dormant until the concrete cracks. Water flowing into the cracks causes the spores to germinate, filling the cracks with fungal fibers that trigger the formation of calcium carbonate—which eventually fills the void. That’s the theory, but the crucial question is whether it would work in practice. So Zhang and co set out to find out.

- The team poured concrete into petri dishes and allowed it to set. They then poured a growth medium onto each slab and added various kinds of fungi. They waited to see which of the fungi would grow in the highly alkaline conditions that concrete promotes. The results were revealing. Of all the fungi tested, only Trichoderma reesei flourished even when the pH rose to 13. Zhang and co then studied its fibrous structure under a microscope and used x-ray diffraction to analyze the deposits it left behind. “The data strongly suggested that T. reesei hyphae can promote calcium carbonate precipitation,” they say.

- Of course, none of that proves that Trichoderma reesei spores can survive if added to concrete when it is mixed. Indeed, at first sight, that seems unlikely. The spores would have to sit in pores within the concrete. Zhang and co measured the pores in the concrete they made and found that they were about one micrometer in diameter on average. But Trichoderma reesei spores are bigger—about four micrometers in diameter. That suggests they would be crushed as the concrete sets. Zhang and co say the problem could be solved by adding air bubbles to the mix, but this needs to be investigated further.


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