Sources of uncertainties for total chloride profile measurements in concrete: quantization and impact on probability assessment of corrosion initiation

Abstract

Reliability methods have proved in the past that they were rational aid-tools for the safety assessment of existing structures, within which some uncertainties occurred. Condition assessment is usually carried out using on-site measurements, which are assumed perfect. However, it is now accepted that some significant uncertainties may affect the assessment of material properties using semi-destructive methods. The purpose of this paper is to present a method for the identification and evaluation of measurement uncertainties using a bias and a zero mean error modelled by a random variable. These uncertainties obtained are then modelled using a probabilistic model. In a marine environment, the main cause of reinforced concrete structure degradation is the corrosion due to chloride ingress. The chloride profiles are determined using a destructive method involving many steps where the experimenter plays a key role. In order to identify sources of errors, four researchers have performed repeatability tests. The total chloride content is expected to be the same for all the samples. The heterogeneity has been studied using statistical analysis. A value of the bias is provided and the model results are consistent with the original results. Finally, the impact of measurement errors on reliability and life-cycle assessment is discussed.

Statistical investigation of different analysis methods for chloride profiles within a real structure in a marine environment

“…It should also be noted that the standard deviation values are higher and more variable on the sheltered side ( Fig. 5a) and that they remain lower than 0.000156, the upper bound of the standard deviation of the error on chloride measurements calculated by Bonnet et al (2017). Moreover, the lower the chloride content, the smaller the standard deviation.…”

“…Recent studies have highlighted the spatial variability of chloride-induced reinforced concrete corrosion with an impact on infrastructure network maintenance optimization (O'Connor and Kenshel, 2013). In the following, the focus is on total chloride content because, firstly, measurement methodology is not subject to debate (Bonnet et al, 2017) and, secondly, because it is the key parameter for already available maintenance optimisation methods.…”

Determining chloride content profiles in concrete using an electrical resistivity tomography device

“…The vertical error bars for the destructive methods are based on a recent study by Bonnet et. al [59] where the vertical standard deviation for total chloride content is approximately equal to 6% (calculated from 42 measurements). Unfortunately, no studies are found about the sources of uncertainties for the free chloride profile measurements in concrete by destructive method.…”

“…Unfortunately, no studies are found about the sources of uncertainties for the free chloride profile measurements in concrete by destructive method. However, as explained in [59], the protocol for obtaining the total and free chloride profiles are similar. In general, and considering the horizontal error bars, the destructive profiles lie in the range of the non-destructive profiles.…”

Value of Information (VoI) for the Chloride Content in Reinforced Concrete Bridges

“…When considering destructive methods, such as the Volhard method, errors in measurement depend mainly on different steps of the protocol, such as grinding, preparation of powder, acid attack, dilution, and concentration measurements. Bonnet et al [57] analyzed 42 chloride content measurements in order to assess the total measurement error by considering three main errors (protocol error, sample error, and human error). The probability of the detection of corrosion initiation was expressed as a function of the margin between the critical concentration and the real concentration, i.e., C(t) − C crit .…”