Nicholls Colton Chloride ion contamination

Chloride ion contamination

Chloride ion contamination, when combined with oxygen and water, can cause corrosion to reinforcement even in alkaline conditions, as the chloride contaminated pore water can cause breakdowns in the protective oxide layer present to the steel.

Chlorides in concrete are either considered fixed from being cast in during construction or free in pore water having ingressed from the concrete surface.  It is the latter form of chloride ion which can derive from road/pavement de-icing salts, seawater spray etc. that present the greater risk of corrosion to reinforcement.  To determine the risk of such corrosion, samples of concrete are taken, commonly in dust form and often at incremental depths, until the level of chloride ion contamination at the depth of reinforcement can be determined.

Standards exist which specify the level of chloride ion content (expressed by mass of the cement present in a sample) at which point a degree of risk of chloride induced corrosion is likely.  An assumed cement content can be used to express the chloride ion content, or the actual cement content can be determined by chemical testing or petrographic analysis, the former generally being used due to cost and time implications.

Results of chloride ion contamination are expressed in a tabular format.

The chloride content is determined in accordance with BS 1881: Part 124:2015 or by our in-house method using a discrete analyser, both methods are covered by our *UKAS accreditation.