Nearly all concrete will crack sometime during its service life. Can you imagine concrete that will heal itself after it cracks? A research team consisting of Dr. M. R. Hansen, professor, civil engineering, and Rebecca Vandine and Cassy West, recent graduates of the master's program in civil engineering, has recently completed the first phase of a research project to study and develop self-healing concrete with the ability to regain strength and eliminate permeability caused by the cracking. The concrete under study has regained its original strength by 50-140 percent and results look very promising for further development. After studying the complicated chemistry of cement hydration, two methods were tried. The first method, led by Vandine, consisted of making conventional concrete with carefully selected mixture proportions to promote healing in a controlled temperature and humidity environment. This method would emphasize critical residual ingredients inside the concrete that would be activated upon cracking. The second method, led by West, consisted of making high performance concrete and then soaking it in a water bath. This would provide water from the outside to combine with residual ingredients to promote the internal healing.
The concrete test specimens were first carefully cracked and the strength measured. The concrete was then healed for 28 days and tested again for strength. Additional factors that affect the healing were discovered and will be investigated in phase II of the project.
This type of basic concrete research is not currently funded because this is a new approach and many agencies wish to obtain useful results immediately from research. With these exciting results, the team hopes to obtain funding from research agencies such as the National Science Foundation.
The scientific report will be submitted for presentation and publication at the International Conferences in Japan and Singapore in 2008.
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