Chloride Ion Content

Our surveyors, Alex and Liam, are currently involved with works at a London underground station on the District Line to undertake a number of tasks under two platforms.

These works include defect inspections & tap hammer surveys. However, the primary reason for our visit is to carry out drilling works to the underside of the platforms with a view to collect samples to determine the Chloride Ion content. Due to Alex & Liam’s previous confined access training, they are well prepared for working in the restricted spaces beneath a train platform.

Analysing the chloride ion content of concrete gives a good indication on the likelihood of corrosion & potential future corrosion within the concrete’s steel reinforcement. Prior to sampling, the test area is scanned with an electromagnetic cover meter to determine the location and depth of embedded reinforcement within the concrete element.

Once the location of reinforcement is determined, we drill to a depth of 5mm and discard the dust produced as it contains potential contaminants from the exposed surface of the concrete which could adversely affect results. We then drill to an extent that exceeds the depth of the reinforcement, to ensure that we collect a sample from around the potentially affected area. The dust produced is collected. A minimum of 25g of dust is required to guarantee an adequate sample size and therefore the accuracy of the lab testing.

Following site works, the extracted samples are forwarded onto and tested at a UKAS accredited laboratory to the standards outlined in British Standard BS 1881 Part 124: “Methods for Analysis of Hardened Concrete”. Results typically take 5-10 days dependent on number of samples taken. The results of which will then be assessed by our surveyors, and provided to the client in a factual report with some interpretation if required

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