MCM worked in JV with Freyssinet to assist Wesfarmer Coal Ltd to repair and protect a 90m diameter concrete thickener tank at their Curragh coal mine near Blackwater, Qld.

The repair work was required to be done during a plant shutdown, as the removal of concrete from the walls of a full tank would have compromised their structural adequacy. The shutdown work was carried out by a team of 30 staff in 12-hour shifts over 2 weeks. It needed great communication and flexibility between all parties involved, particularly due to the torrential rain and flooding in Queensland in the time leading up to the plant shutdown.

The concrete repairs were completed in good time for the tank to be refilled on schedule. After this was done, attention turned to installing a corrosion prevention system involving hybrid anodes grouted into holes at set spacings over the entire launder wall and accessible soffit and lower wall areas. The system was designed by Infracorr Pty Ltd.

These anodes were provided with DC power from generators for several days before being terminated into junction boxes to operate galvanically for the rest of their design life. After all zones had reached galvanic mode an overlay of dry process gunite was applied to the launder wall.

The work during and after the shut down included:

• 700m of crack injection
• 460 of floor joint resealing
• 82m² of concrete repairs by hydrodemolition & gunite spraying by dry process
• 117m of replacement of top of concrete wall by hydrodemolition and form & pour.
• Installation & commissioning of 8,300 hybrid anodes
• 400m² of sprayed gunite overlay to anodes

Original contract period of 18 weeks completed 4 weeks early, under budget and with no safety or environmental incidents.