Smart concrete : sensor system for durability monitoring

Abstract

Reinforced concrete is one of the most widely used building materials globally, and its deterioration leads to reduced performance of the structure or some of its elements. This happens due to concrete carbonation or when aggressive agents, such as chloride ions, attack the reinforcement embedded in the concrete itself. With adequate measures during construction stages, the corrosion of the steel bars can be reduced and hence, increase the service life of reinforced concrete structures. The penetration of chloride ions leads to the early degradation of the structure, which requires expensive repairs. The deterioration of reinforced concrete structures presents a significant problem in the built environment, leading to a late intervention with a high cost. However, by employing sensors, one can monitor the reinforcement of a structure to identify the onset of corrosion. The objective of this dissertation is to assess the relative performance of concrete elements through sensors embedded in concrete. Through this, the mechanical and durability parameters of the concrete shall be determined. Galvanic and resistivity sensors, developed at the University of Malta by the Faculty for the built environment, were produced and assembled. A test station for field monitoring was set up on the Maltese coast with six different concrete types, including different mix constituents, to assess relative durability performance. In addition, associated laboratory reinforced samples were prepared for the same mixes and equipped with these different sensors developed. The samples were exposed to different environments, including an aggressive environment with high chloride concentration and wet/dry cycles. The relative performance of the different sensors and their efficacy in monitoring the penetration of chlorides and onset of degradation is assessed over time. This dissertation presents the framework for the assessment of degradation in smart sensors, based on the sensor system for structural durability health monitoring.