tremie

Tremie refers to a method and the equipment used to place concrete underwater in a controlled manner. The system centers on a tremie pipe that extends from above the water surface down to the placement zone. The pipe allows fresh concrete to be pumped or poured into the submerged area while remaining isolated from the surrounding water, which helps prevent washout and segregation. Tremie placement is commonly used for underwater foundations, caissons, cofferdams, piers, breakwaters, and offshore structures.

The key pieces of tremie equipment are the tremie pipe, a bottom seal or valve, and a surface pump or crane-mounted pump. A tremie hood or nozzle may be used at the surface to minimize splash and keep the concrete intact as it enters the pipe. The pipe is kept fully filled with concrete, and during the pour the tip remains submerged in the already placed concrete or in the fresh concrete inside the pipe. The operation proceeds as the pipe is raised or withdrawn, with concrete continuously pumped to maintain a continuous, water-free column.

Concrete for tremie placement is typically designed to minimize washout and segregation. This often means a low water-cement ratio with admixtures such as plasticizers or anti-washout agents, and sometimes a self-consolidating or high-workability mix that remains cohesive under water. Quality control includes slump testing, monitoring for segregation, and ensuring continuous operation to avoid gaps or exposure to water.

Advantages of the tremie method include greater control over placement, reduced segregation, and the ability to place concrete at depth. Limitations involve the need for specialized equipment, careful planning, and the risk of defects if pours are interrupted. Tremie methods have been widely used in offshore and harbor construction.