A small Team, travelling and working to Construction Leadership Council Site Operating Procedures (CLC SOP) and with a Safe System of Work, successfully completed the site phase of a structural material condition assessment.

The structure, a redundant, in-situ reinforced concrete Activated Sludge Plant, constructed during Her Majesty’s Coronation Year, mothballed in 2004 and now proposed for re-activation (to handle all the extra toilet paper out there?). The Plant comprised 7 lanes, each with 2 channels, each divided longitudinally, with baffle walls, into 7, 10m x 3m x 4m deep cells, i.e. 98 cells total.

The cells had been cleaned when mothballed, but with ankle / calf deep water now ponded in the bottom. The water was analysed and confirmed to be rainwater, but regardless, the cells were treated as medium risk confined spaces, with an appropriate Safe System of Work developed.

CRL Surveys carried out:

1. A study of previous use and likely exposure to chemical dosing.
2. Visual Inspection, selecting 10 representative cells for more detailed diagnostic investigations, including:
1. Close quarters inspection, with defects recording and scheduling. The surfaces were also subjected to physical testing to assess surface chemical attack, degradation, erosion and weathering.
2. Assessments of Material Condition: covermeter survey, depth of carbonation and drilled dust sampling for chemical analysis for chloride and sulphate contents.
3. Scanning, using radar and Ferroscan, to evaluate reinforcement.
4. Schmidt / Rebound Hammer testing.

Now back at the office (working from home) we are processing data, whilst samples are at the Lab. Likely future exposure conditions, when the Plant is reactivated, will be reviewed and by the end of the week, 2 weeks from completion on site, we will Report and make recommendations for the repair and protection of the concrete, for a further 20-year life in service.