Development of a capacitive sensor for concrete structure health monitoring

Abstract

Considering the limitations of the current structure health monitoring techniques, a novel low-cost capacitive transducer (CT) using capacitance signals, which has the potential to provide accurate health assessment and damage prediction for reinforcement concrete structures, is firstly developed in this study. Four major works including the development of the capacitive sensor, the optimization work of CT sensor design, the application of the CT in rebar size/depth/position and rebar corrosion tests using the developed CT are mainly introduced. In the sensor development process, two designs of capacitive transducers are discussed for condition assessment of rebar and concrete, respectively. In order to verify the effectiveness of the designed capacitive sensor, five preliminary experiments are conducted and the experiments results also showed that CT signals could be applied to predict rebar positions inside the concrete. Finally, FEM simulations were implemented for the last experiment, and comparison results have well verified the effectiveness of the developed capacitive sensor. In the sensor optimization work, performances of different parameters in terms of electrodes size/shape, concrete length, electrodes spacing and rebar size are compared in order to get an optimized sensitivity in the rebar depth testing. In the rebar size/depth/position test, both numerical simulations and experiments have been carried out to verify the effectiveness of the developed capacitive sensor. Results have shown that the developed CT with innovative capacitance measuring method has great accuracy in predicting the rebar size and position, which is the foundation of the reinforcement corrosion detection. In the corrosion testing part, a novel corrosion development model according to the increase of rust layer thickness is firstly proposed and direct quantitative relationship between the capacitance outputs and the rust layer thickness is built to measure the corrosion degree. Apart from uniform corrosion testing, localized corrosion testing including half-rebar corrosion, side corrosion and various banding layer corrosion have been implemented to verify the function of the CT technique. It can be concluded that the developed capacitive transducer is applicable in the condition tests of reinforced concrete structures and it paves the way for quantitatively evaluate the corrosion degree of the reinforced rebar.

Date of Award	2017
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology