In-Sito Monitoring of Concrete Condition using Electric Field Sensors

Structural health of concrete-based structures in light water reactors (LWRs) is critical to safe operation of existing and future nuclear power plants. Degradation of concrete in these structures is caused by chemical and physical attacks that affect the cement-paste matrix or aggregate materials. There is a need for nondestructive evaluation technology to detect and monitor these attacks so that remedial actions can be taken to restore the concrete structure or impede further degradation. In this program JENTEK will evaluate the capability of the segmented field IDED capacitive sensing technology to detect and monitor debilitating damage to concrete using permanently mounted (in-situ) and scanning sensor configurations. Preliminary laboratory experiments have demonstrated that the electrical properties measured by these sensors correlate with important chemical and physical damage mechanisms. Advantageously, the IDED sensor technology only requires access to a single surface of the concrete to be inspected. Multiple sensor geometries are integrated into a single sensor footprint such that multiple penetration depths of the electric field can be achieved at each sensor location. Physics based models of the IDED sensors and the concrete provide a methodology for predicting the sensor responses and relating measured responses to estimated electrical properties (e.g., permittivity and conductivity) of the material. The electrical properties may then be correlated with specific damage modalities providing a depth profile of the concretes condition. Commercial Applications and Other Benefits: Nondestructive condition monitoring of structures has substantial commercial potential both for civilian applications and those of the US government. Concrete structures are key elements not only in the nations nuclear power industry, but also of its civil infrastructure. Effective life management of these structures could bring billions of dollars in savings while also improving operational safety. In addition to concrete structures associated with the nuclear power plants and transportation infrastructure, there is a need for improved moisture measurement in concrete structures used in general construction. Concrete slabs are commonly used in flooring system for a range of residential and commercial buildings. The use of concrete walling in these buildings whether in-situ or precast is also increasing. Current sensor technology does not provide an effective means of nondestructively monitoring the health of concrete structures. If this program is successful a non-destructive evaluation tool will become available to better assess the condition of such concrete structures.