Development of Microwave and Impedance Spectroscopy Methods for In-Situ Nondestructive Evaluation of Alkali Silica Reaction in Concrete

Aging concrete degradation due to alkali silica reaction (ASR) is a challenge to sustainability of critical infrastructure, such as nuclear power plants. Currently, there is no standard, nondestructive method for detecting ASR in concrete. We report on the progress in developing electromagnetic (EM) methods, consisting of microwave and impedance spectroscopy techniques, for nondestructive detection of ASR. The microwave and impedance spectroscopy methods are complementary since they provide information about material electrical properties in GHz and Hz to KHz EM spectral bands, respectively. Preliminary studies were conducted using accelerated testing concrete prism specimens developed according to ASTM C1293 standard. Microwave and impedance spectroscopy measurements were performed on ASR specimens at the first and the second month maturity level, as well as on age-matched controls. Microwave tests consisted of reflection and transmission measurements using dielectric-loaded antennas, with the focus on X-band spectrum. Impedance measurements were performed using flexible electrode patches. Measurement results by both microwave and impedance spectroscopy methods indicate observable differences in electrical properties between reactive and non-reactive specimens. In addition, trends in measurement data obtained with the two complementary EM techniques are consistent and correlate with ASR progression in specimens.