A Novel Way to Track Damage in Concrete

Water will seep into cracks in concrete, eroding the material from within, but can also carry other substances—like road salt—into a foundation, speeding up damage or corrosion to steel supports.

To combat this, researchers from North Carolina State University and the University of Eastern Finland have developed a new technique for tracking water in concrete using electricity.

By applying electrodes around the perimeter of a structure, a small current is run between two of the electrodes at a time as a computer monitors and records the electrical potential of all the electrodes on the structure. As the computer cycles through a number of possible electrode combinations, researchers are able to produce a three-dimensional image of the water in the concrete.

"When we think about construction—from bridges and skyscrapers to nuclear plants and dams— they all rely on concrete," said Mohammad Pour-Ghaz, an assistant professor of civil, construction and environmental engineering at North Carolina State University and lead investigator on the project.

Existing techniques for assessing water in concrete rely on X-rays which offer only limited penetration into the structure or neutron radiation which is more accurate, but also has limited penetration, is expensive and poses health and safety risks.

"We have developed a technology that allows us to identify and track water movement in concrete using a small current of electricity that is faster, safer and less expensive than existing technologies - and is also more accurate when monitoring large samples, such as structures," added Pour-Ghaz.

"The technology can not only determine where and whether water is infiltrating concrete, but how fast it is moving, how much water there is, and how existing cracks or damage are influencing the movement of the water."

Pour-Ghaz noted that the technology is ready to be packaged and commercialized for laboratory use, and sees the potential for scaled up versions in the private sector, as an on-site tool to assess structural integrity.

The research has been described in multiple papers, including "Can Electrical Impedance Tomography be used for imaging unsaturated moisture flow in cement-based materials with discrete cracks?" is published in the journal Cement and Concrete Research, "Quantitative electrical imaging of three-dimensional moisture flow in cement-based materials" published in the International Journal of Heat and Mass Transfer and "Three-Dimensional Electrical Impedance Tomography to Monitor Unsaturated Moisture Ingress in Cement-Based Materials" published in the journal Transport in Porous Media.