Electric current used to track water in concrete

Water contributes to concrete degradation on its own, and can also carry chemicals such as salt that have an additional corroding effect. Monitoring how water penetrates concrete is, therefore, essential for overseeing the health of the built environment, and the material’s ubiquity makes this a significant task.

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

The electrical imaging technique developed by Pour-Ghaz and his colleagues involves placing electrodes around the perimeter of a structure. A computer program then runs a small current between two of the electrodes at a time, cycling through a number of possible electrode combinations.

Each time the current runs between two electrodes, a computer monitors and records the electrical potential at all of the electrodes on the structure. Custom software then computes the changes in conductivity and produces a three-dimensional image of the water in the concrete.