Over time, regular concrete strengthens and is thus more resilient to possible damage. However, when concrete ages, carbonation lowers the ph balance of cement, making it more acidic. Higher acidity of the cement solution may result in corrosion of steel support reinforcement bars. With nano-enabled concrete, nano-polymer aggregates may release active compounds that trigger changes in ph when the concrete becomes too acidic. These nano-polymer aggregates do not remedy the problem directly but act as an intermediary in the self-healing process. With a self-maintaining ph level, there exists reduced potential for corrosion and subsequent (expensive) remediation work.
In addition to changing ph levels, cracks in concrete, which result in increased exposure to the elements, may activate the reproduction of latent bacteria spores. The bacteria, once reproducing, produce minerals as byproducts; these minerals in turn fill and seal the crack. It is important to note that the spores are not at the nano-scale per se, defined at 1 – 100 nm, but rather at the micrometer level (1 µm).
- . Nanotechnology in Building Materials. [Internet]. Submitted . Available from: http://www.engineering.uiowa.edu/~hraza/ENG29_Fall10/NanotechnologyBuildingMaterials.pdf
- Using Bacteria to Sefl-Heal Cracks in Concrete. [Internet]. 2010 . Available from: http://www.aggregateresearch.com/article.aspx?id=19043
- . SELF-HEALING MATERIAL CONCEPTS AS SOLUTION FOR AGING INFRASTRUCTURE. Delft University of Technology; 2012. Available from: http://www.cipremier.com/e107_files/downloads/Papers/100/37/100037009.pdf
The risks of the nanoparticles in this new self-healing concrete are uncertain. They can potentially pose a threat if they become airborne, but the likelihood of such an incident is unknown. The long-term structural integrity of these self-healing concretes have not been studied either, prompting the need for further research.