Critical chloride content: realistic determination and application in practice

Background

The concept of the critical chloride content has been used since the 1950s to define a threshold value above which corrosion of steel in concrete occurs. Unfortunately, as reviewed in a external page comprehensive study, the reported literature value scatter widely and provide a poor basis for engineering practice, where input values for service life predictions are needed. A major drawback of the vast majority of laboratory studies can be found in the difficulties to mimic, in laboratory made samples, practice-related conditions at the steel-concrete interface.

Aims and objectives

This project aims to determine the critical chloride content by testing samples taken from engineering structures, rather than laboratory made samples. The aim is to deliver a database of the statistical distribution of critical chloride contents in a range of typical Swiss engineering structures. 

Methodology

Reinforced concrete cores are drilled from a number of different engineering structures (not yet corroding). These samples are then tested in the laboratory with a recently developed method. Detailed descriptions of this published “ETH-protocol” can be found external page here.

After corrosion initiation, the samples are split and the steel-concrete interface carefully inspected in order to gain insight in to the influence on corrosion initiation.

Online resources

All results of this study are systematically collected in an open access database on critical chloride contents.

The database and the related descriptions can be accessed here:

• Link to Ccrit Database (continuously updated)
• Link to external page documentation and external page explanations related to the database


If you wish to explore the database you may wish to visit the online interactive visualization of the collected data at the following webpage: Critical chloride visualization