Abstract
Chloride threshold value is an important input parameter in service life predictions. There has been a need for a reliable method for testing this value in order to improve the understanding of basic factors influencing the corrosion initiation. For this reason RILEM technical committee (TC) 235-CTC was formed with the ultimate aim to recommend a suitable test method capable of delivering data with acceptable measurement uncertainty. During the TC’s life, a test method was proposed and a Round-Robin Test (RRT) was organised to evaluate it. Due to the unexpected results from the RRT, the ultimate aim of the TC was not reached. There were some experiences obtained from the TC’s work especially in designing the test method which are worthy for supporting future researchers continuing to search for a reliable test method for it. This technical letter presents the TC’s experiences.
Highlights
The chloride concentration in concrete at which corrosion of reinforcement is initiated is an important parameter, called the critical chloride concentration (Ccrit), or chloride threshold value, which is relevant for service life prediction of reinforced concrete
According to the results from these three laboratories, the measured chloride threshold values for the reference concrete varied from 0.6% to 1.6% with an average 1.05% by mass of cement
For the laboratories without observation of corrosion initiation after 290 to 800 days exposure in chloride solutions, the measured chloride content at the steel depth varied from 0.5% to 2.8% by mass of cement
Summary
The chloride concentration in concrete at which corrosion of reinforcement is initiated is an important parameter, called the critical chloride concentration (Ccrit), or chloride threshold value, which is relevant for service life prediction of reinforced concrete It has been well known for many years that this parameter is vital, but the scatter of data in the literature is huge [1,2,3,4,5]. Because the ultimate aim was to deliver repeatable and reproducible measurements of Ccrit, The TC agreed to ensure a “reproducible and realistic surface condition” This means that procedures such as sandblasting, polishing, etc., were disregarded. After standard moist curing each specimen was cut to a cover of 10 mm with a possibility for variation if needed
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