Underwater concreting is achievable and often used globally for permanent repairs and structure installations. In fact, commercial diving services have poured thousands of cubic meters of concrete on many underwater projects since 1955.
The important points to remember with successful underwater concrete placement is to have a good quality non floating form work in place, relatively short screening distance between form work and the placement of the actual concrete is critical to a successful pour in as much at all times the discharge end of the tremytube or concrete pump discharge tube which in both cases are diver held and monitored should at all times be submerged in the concrete pour and not allowed to flow freely through any portion of the water column, as this will result in the concrete dilution.
Underwater concreting is widely used in today’s marine construction industry in the stabilisation of various foreshores and harbours among other erosions areas in and around the tidal zones. Typically this is achieved by filling with a concrete grout mixture into foreshore stabilisation mattresses (grout mattresses) of various sizes which ultimately act as a concrete blanket in and around tidal zones and to the harbour bed floor which might be exposed to propeller wash from tugs and ships thus preventing erosion and embankment slippage.
The technique of pouring concrete underwater and filling of grout mattresses requires sound pre-planning, the correct grout or concrete mix depending on the task is critical to successful outcome and often the divers visibility is severely reduced due to the pouring process and this requires sound planning to ensure the techniques which are being used can be used in both good and bad water clarity conditions to achieve a successful grout and concrete pour.
A well placed concrete pour carried out underwater can be equivalent to the same pour carried out topside in strength and longevity.
Examples of underwater concreting uses are:
- Structure foundations and slabs
- Embankment stabilisation
- Pier and Pylon footings and supplement
- Pipeline and cable encasement’s
- Boat Ramps