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CROSS Safety Report

High strength concrete incident

Report ID: 406 Published: 1 April 2014 Region: CROSS-UK

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Confusion on sites lead to the incorrect concrete grade being used for some structural elements.

Key Learning Outcomes

For construction professionals:

  • Quality control and competent supervision on site can help to ensure that the structure is built in accordance with the design

  • It is good practice to carry out a risk assessment and method statement (RAMS) for all construction activities. This can ensure the sequencing of work activities are properly considered and planned.

Full Report

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This relates to a project where the concrete in the walls was C40, and the in-line columns was C60 (Figure 1). The walls were in the same width as the columns so difficult to distinguish which was which from the top of the shutter. The contractor put concrete of the right mix in the wrong hole in the shutter. An easy mistake to make says the reporter but the designer could have thought about it.

Figure 1: construction drawing of concrete walls and columns

Expert Panel Comments

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Again, is the designer sure that what he thought was being built was actually built? One grade of concrete cannot be distinguished from another just by looking at it.  Different strengths of concrete in the same part of a structure can lead to problems if mistakes are made so in such cases there should be clear identification of the sequence of operations.

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