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Cure Thyself – The quest for self-healing concrete marches forward
John Caulfield / BUILDER / March 4, 2013
For the past several years, academies and laboratories have been trying to figure out how to reduce the damage to buildings caused by cracks in concrete.
There have been numerous approaches to this problem, including a form of concrete, developed in 2009 by the University of Michigan’s Advanced Civil Engineering-Materials Research Lab, which uses microfibers that allow the concrete to bend. The dry concrete absorbs moisture from the air and softens to fill tiny cracks (no wider than 150 micrometers) with calcium carbonate material.
In 2010, a student at the University of Rhode Island embedded a microencapsulated sodium silicate healing agent into concrete. When tiny cracks form, the capsules rupture and release the healing agent that reacts with calcium hydroxide naturally present in the concrete to form a compound to heal cracks and block pores. The drawback is that the gel created takes week to harden.
Last year it was reported that Dr. Alan Richardson of the University of Northumbria in Great Britain was using ground-borne bacteria—grown on a nutrient concoction of yeast, minerals, and urea and added to concrete—to create calcite, a crystalline form of natural calcium carbonate. The calcite blocked the concrete’s pores, keeping out water and other damaging substances to prolong the life of the concrete.