Conformity control of concrete durability parameters and its filtering effect on the design service life

Abstract

Conformity control is applied in order to safeguard the quality of produced lots. Conformity criteria are characterized by an operating characteristic curve, quantifying the probability of acceptance in relation to a concrete lot with a specific quality. By applying conformity control, certain lots of concrete are accepted or rejected. This induces a filtering effect, which in case of conformity control of durability parameters leads to an effect on the design service life. For durability, limiting values for durability-related properties can be proposed. Specifying conformity criteria for the durability parameters of concrete can enable to safeguard the quality of concrete products in relation to durability. This conformity control has a filtering effect on the distribution of these durability parameters. When, for example, considering the diffusion coefficient of concrete, this filtering effect results in a lower mean value and standard deviation, consequently (positively) influencing the service life. In this paper, conformity criteria for durability parameters are developed, and their effect on the design service life of reinforced concrete elements is quantified.

Development of conformity criteria for durability and its influence on service life predictions

“…For this purpose, a sample of limited size is used and from this sample inferences are made with regard to the whole population. As stated in [7], for the diffusion coefficient, the mean value D m , corresponding to the 50%-fractile of the theoretical distribution can be considered as the specified value, or the characteristic value D k corresponding to the 90% fractile [7,8].…”

“…In practice, the fraction above the specified value (corresponding to an undesired situation of a high diffusion coefficient) will be smaller or higher than 50% or 10% respectively. When θ is the fraction of test results higher than D m or D k in the offered distribution, equations ( 1) and ( 2) are valid [7] (where X is the diffusion coefficient, considered as a random variable). This value θ will be further denoted as the fraction defectiveness.…”

“…In such situations, a numerical algorithm can be applied, such as the one developed in [11], which has its basis in Bayesian statistics and applies numerical integration. The method applied in this work is also described in [7]. Similar as in [7], in the following, the batches offered for conformity control, i.e.…”

“…The method applied in this work is also described in [7]. Similar as in [7], in the following, the batches offered for conformity control, i.e. the incoming concrete batches, are represented by the index 'i'.…”

“…In this section, conformity control is considered for the diffusion coefficient and the filter effect on its distribution is investigated. Since there are no standards yet providing conformity criteria for the diffusion coefficient, in this work, some assumptions are made in relation to the format of the conformity criteria, which are similar to those in [7].…”