Self-Heal­ing Con­crete

Popular Science - - BUILT TO OUTLAST: POPSCI 2018 -

CHAL­LENGE: CRUM­BLING IN­FRA­STRUC­TURE LO­CA­TION: WORLD­WIDE

Higher con­cen­tra­tions of car­bon diox­ide in our at­mos­phere ac­tu­ally ac­cel­er­ate de­te­ri­o­ra­tion of con­crete. As CO2 pen­e­trates a struc­ture, it re­acts with al­ready present mois­ture and cal­cium hy­drox­ide, pro­gres­sively eat­ing away at the layer of ce­ment cov­er­ing steel re­in­force­ments, leav­ing them vul­ner­a­ble to rust. For­tu­nately, Henk Jonkers, an en­vi­ron­men­tal sci­en­tist at TU Delft in the Nether­lands, has in­vented a self-heal­ing ver­sion. Jonkers em­beds con­crete with ni­tro­gen, phos­pho­rus, cal­cium lac­tate, and a lime­stone-pro­duc­ing bac­te­ria. The ad­di­tives lie dor­mant un­til a fis­sure emerges, ad­mit­ting air and mois­ture. Then the bac­te­ria ac­ti­vate, feed­ing on the cal­cium lac­tate, con­vert­ing it into lime­stone, and seal­ing the split.

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