Smart Aggregate With Dual Sensitivity Enhancement for Strain Sensing

A smart aggregate can provide the health state of a structural member for the next generation of intelligent infrastructures. This article proposes an innovative passive aggregate with dual sensitivity enhancement for strain sensing, which has an augmented sensing unit and a compliant displacement amplification mechanism. The sensing unit is composed of a sensor based on a combined patch antenna with an air gap coupling feed to realize the sensitization enhancing. Compliant displacement amplification mechanism is used as the sensor sensitizing mechanism to further enhance the sensitivity. The packaging shell and displacement amplification mechanism of the smart aggregate are integrating 3-D printed with VERO high toughness resin and embedded in concrete for experiment. Through sensor modeling and optimization, the effects of various parameters were analyzed to determine the optimal sensor configuration. Experimental results demonstrated the feasibility of the smart aggregate for monitoring internal concrete strain, achieving a maximum sensitivity of 110 MHz/ $\mu \varepsilon $ using quadratic curve fitting and 59 MHz/ $\mu \varepsilon $ with linear fitting. This innovative design provides an effective passive solution for structural health monitoring in complex concrete environments.