As the name suggests, underwater concrete is installed below the water line, e.g. for:
- Port and harbour installations
- Bridge piers in rivers
- Water industry structures
- Metro systems
- Deep shafts in unstable ground
Special requirements
Standard method is pumping a suitably modified mix through a standard concrete pump. The end of the delivery pipe must be kept deep enough in the fresh concrete. Another method of placing underwater concrete with minimum loss is the tremie process (Contractor Method). The concrete is placed directly through a 20 – 40 cm diameter pipe into and through the concrete already installed. The pipe is raised continuously, but the bottom end must always remain sufficiently submerged in the concrete to prevent the water going back into the pipe.
Other important considerations:
- As the flow rate of water increases, more leaching can occur, it is possible to design the concrete to minimise washout at various water flow rates
- Avoid pressure differences on the pipe (such as water level differences in shafts)
