The Constructive Evaluation surveying team recently attended a site in Worthing, West Sussex to carry out a delamination survey to the screed of a warehouse building. Delamination surveys are nothing new for us, having undertaken numerous tap hammer & visual surveys in the past. This survey however, differed from the norm due to the vast ~6.7km² surface area that needed to be assessed. Tap hammer surveys on such a large area would be very time consuming and not at all cost effective. As such, we undertook a chain drag survey.

As the name would suggest, a chain drag survey involves dragging a folded length of chain over a concrete surface. Concrete has different audible qualities based on its condition. Defective concrete will produce a hollow sound compared to the much more solid, richer sounding timbre of good quality concrete. Dragging the chain across a surface picks up the changes in sound across the entire length of the area in question, and therefore enables us to mark up the defective regions with a fair degree of accuracy in a much shorter time frame.

Whilst previous third-party investigations deemed it unnecessary in this instance, it is recommended that the delamination is confirmed with a variety of other investigations including concrete core drilling. The concrete cores enable us to assess the bond between the layers of screed and concrete. It is also possible; with supplemental testing, to assess the compressive strength of the concrete, if so desired by the client.

Once back in the office, the data collected is plotted onto a scale CAD plan drawing. This enables us to calculate the total surface area affected in either metres squared or as a percentage. In turn the client is then able to work out a cost estimate for repairs.

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