Tremie Method - Innovative Method in Concrete Construction

Concrete (Links to an external site) is a material that is widely used in various building structures making it a very important in construction industry. It is inexpensive and strong. It is easy to make, it is made by using all natural ingredients and because it is also recyclable, this material is considered environment-friendly. Concrete is composed of aggregates, rocks, and paste, a mixture of Portland cement and water, which hardens when hydration begins. The reduced cost and construction time, and making the concrete application possible under certain construction condition and environment are the results from the huge developments in materials and equipment, and new concepts in innovating construction techniques. Because construction has been continually innovating, there are many new methods in concrete construction that have been lately rising and one of them is Tremie Method.

Tremie Method uses a watertight pipe called Tremie to pour concrete underwater. It is often supported by a working platform above water level. Underwater concrete plays an important role in the construction of offshore structures, Tremie concrete may be used to tie together various elements in composite action. The lower end of the pipe is kept immersed in fresh concrete so that the rising concrete from the bottom displaces the water without washing out the cement content. A Tremie concrete mix is a special mix with plasticizer, has a high slump concrete with set retarders. It has smaller aggregate sizes, has a four-hour workability, and it is designed for placement under water via Tremie pipe.

The placement of Tremie concrete is carried out through a tube, usually 10- to 12-in. pipe. The pipe may be sectional but joints should be flanged and bolted, with soft rubber gasket, so as to prevent any in-leakage of water. The Tremie pipe must have sufficient wall thickness so that it negatively buoyant when empty. A steel plate is installed on the bottom end with a soft rubber gasket then the plate is tied with twine to the pipe. The placement is started by placing the sealed pipe on the bottom and then partially filling it with the Tremie concrete mix. When Tremie has been filled to a reasonable distance above the balancing head of fresh concrete versus surrounding liquid, the pipe is raised 150 mm, allowing the concrete to flow out. The lower end of the pipe is kept embedded in fresh concrete, but no deeper than where the concrete has taken the initial set.

The tip of the Tremie pipe should always be immersed about 1 m as a minimum so as to prevent water inflow into the pipe. The flow of concrete should be smooth, consistent with the rate at which concrete can be delivered into the hopper at the top. The method of delivery should provide relatively even feed to the hopper rather than large batches being suddenly dumped. When large areas are to be covered, multiple Tremie pipes should be used. The distance Tremie can flow without excessive segregation is between 6 and 20 m.