Modeling of spatial variability of concrete cover apparent resistivity and depth in a reinforced concrete wharf from onsite measurements

Concrete cover apparent resistivity and concrete cover depth are two key parameters in modelling the corrosion current density of rebars in reinforced concrete marine structures subject to chloride-induced corrosion. Due to the variability of construction and environmental conditions encountered within a single structure, these parameters exhibit spatial variability that may significantly influence the corrosion current density and, ultimately, the probability of failure at the ultimate limit state. The aim of this work is to provide spatial variability models that can be used to study this issue, based on an in-situ case study of a 28-year-old quay beam on the French Atlantic coast. To this end, a rigorous geostatistical analysis is carried out on a large database of 222 apparent resistivity and 366 cover depth measurements. Beginning with a preselected set of random field models, the geostatistical analysis estimates their parameters using a procedure that concurrently verifies the underlying assumptions of ergodicity, stationarity, and random field modelling, and accounts for measurement error. To the authors' knowledge, this provides the first random field model of apparent resistivity calibrated on in-situ measurements of an aged marine structure, together with an updated cover depth model that explicitly handles measurement noise. The resulting hyperparameter values are intended as prior values for the durability assessment of similar marine wharves.