Double-Sided Metamaterial-Inspired Microwave Sensor for Monitoring of Alkali-Silica Reaction (ASR) in Cement-Based Mortar Samples

Ordinary Portland cement (OPC) structures are the simplest and oldest type of cement in use today. Their service lives, however, are largely limited by the alkali-silica reaction (ASR), which has the potential of producing microstructures throughout OPC structures. There is, therefore, a need for accurate detection of the ASR. In this study, we propose a double-sided metamaterial (MM)-inspired microwave sensor for the identification of the ASR occurring inside OPC mortar samples. Different from previous studies for ASR detection, our design heavily relies on a resonance phenomenon, resulting in a relatively highly accurate and sensitive detection. The resonator has designed cells operating over 2.6-3.95 GHz (S-band) in which microwave signals are very sensitive to water reactions, giving a high sensitivity for ASR detection. Simulations and experiments were performed for the S-band to validate our sensor. Expansion tests are conducted, and SEM micrographs are taken to support microwave measurements. Confidence interval (CI) analysis is conducted to assess the integrity of measurements.