Electromagnetic monitoring of concrete structures

Non-destructive evaluation of reinforced concrete structures is an increasingly important field in the construction and civil engineering community. A large number of pathologies that affect both the concrete and the reinforced bar inside concrete are related to the presence of water and its spatial development. In this context, the quantification of both water content and bar diameter is an important phase for the diagnosis of concrete. The propagation of electromagnetic waves is controlled by its electromagnetic properties, mainly influenced by the presence of water in the case of concrete. The dielectric properties of concrete were studies as function of volumetric water content. To measure the dielectric properties of concrete as function of volumetric water content at high frequency, a HP-impedance analyser was used. More than 800 samples of concrete were analyzed and a new relationship between relative dielectric constant and volumetric water content was obtained. Furthermore the study was focused on the simulations for one centre frequency GPR applied to a range of rebar sizes common used as concrete reinforcement. This is compared with real measurements of different known rebar sizes inside concrete structures using 1GHz centre frequency antenna. Furthermore empirical relationship between rebar sizes and electromagnetic parameters was established and analytical functions were proposed.