Fungi to Be Used For Self-heal­ing Con­crete?

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Re­searchers from New York’s Bing­ham­ton Uni­ver­sity have been look­ing into how to help con­crete re­pair it­self us­ing a spe­cial kind of fungi.

While the 20th cen­tury brought with it some re­mark­able roads, bridges and ar­chi­tec­ture, many of those are now ag­ing and in dan­ger of fall­ing apart.

They may be doomed, but thanks to new re­search led by as­sis­tant pro­fes­sor Con­grui Jin of the State Uni­ver­sity of New York at Bing­ham­ton Uni­ver­sity, there may soon be hope for longer-last­ing struc­tures in the fu­ture.

What Jin con­sid­ered is the first known for­mal look at the use of fungi to make self-heal­ing con­crete.

As many have noted in the past, one of the main rea­sons for the slow de­cay in the struc­tural in­tegrity of con­crete struc­tures is the small cracks that ap­pear within it.

In ex­am­in­ing that, Jin noted, “With­out proper treat­ment, cracks tend to progress fur­ther and even­tu­ally re­quire costly re­pair.” He added that if this prob­lem is al­lowed to con­tinue and “if mi­cro-cracks ex­pand and reach the steel re­in­force­ment, not only will the con­crete be at­tacked but also the re­in­force­ment will be cor­roded, as it is exposed to wa­ter, oxy­gen, pos­si­bly CO2 and chlo­rides, lead­ing to struc­tural fail­ure.”

That could spell ma­jor prob­lems in any num­ber of build­ing ap­pli­ca­tions.

The con­ven­tional ap­proach to han­dling this is to in­spect the struc­ture, carve out the ag­ing con­crete and per­haps re­build ma­jor parts of it. But that only post­pones the even­tual need to re­place the whole thing. It also does not pro­tect the con­struc­tion against hid­den de­cay in the ar­eas that were not re­placed.

Jin saw this and took a dif­fer­ent ap­proach to find­ing a way to fix the con­crete in a more per­ma­nent way.

He took his in­spi­ra­tion from the way the hu­man body is able to heal it­self of ev­ery­thing from mi­nor bruises and cuts to bro­ken bones. Even more amaz­ing, the body also of­ten re­builds it­self to be even stronger after a prob­lem than it might have been in the first place. Jin won­dered if this might be pos­si­ble with con­crete.

Work­ing along­side Rut­gers Uni­ver­sity as­so­ciate pro­fes­sor Ning Zhang, plus both pro­fes­sor Guang­wen Zhou and as­so­ciate pro­fes­sor David Davies of his own in­sti­tu­tion, Bing­ham­ton Uni­ver­sity, Jin searched for a so­lu­tion.

What the team came up with was to mix a fun­gus called Tri­cho­derma ree­sei with the con­crete.

In the so­lu­tion they ex­plored, the fun­gus lay dor­mant un­til the first crack showed up in the fin­ished struc­ture. As Jin ex­plained, “The fun­gal spores, to­gether with nu­tri­ents, will be placed into the con­crete ma­trix dur­ing the mix­ing process. When crack­ing oc­curs, wa­ter and oxy­gen will find their way in. With enough wa­ter and oxy­gen, the dor­mant fun­gal spores will ger­mi­nate, grow and pre­cip­i­tate cal­cium car­bon­ate to heal the cracks.”

It turns out that when those cracks are com­pletely filled, strength­en­ing the con­crete, the fungi go back into a dor­mant state again, form­ing spores but not do­ing much else. When fur­ther cracks ap­pear, the cy­cle re­peats.

It should be pointed out that this is still a very early stage re­search project, with much work still re­main­ing to be done be­fore any con­sid­er­a­tion can be made to con­vert this into a mass-man­u­fac­turable so­lu­tion. One of the biggest chal­lenges, Jin ad­mits, is how to keep the fungi alive in the un­for­giv­ing and harsh en­vi­ron­ment of the fin­ished con­crete.

He and his team are con­tin­u­ing their re­search and hope to make fur­ther ma­jor strides on the com­mer­cial vi­a­bil­ity of the con­cept in the near fu­ture.

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