What is the function of a tremie in concrete pouring?

The tremie is specifically designed for underwater concrete placement, and its primary function is to prevent the washout of cement during the pouring process. When concrete is poured into water, especially in deep or turbulent conditions, there is a risk that the finer components of the concrete mix, such as cement, could be washed away before they properly settle. The use of a tremie minimizes this risk by allowing the concrete to flow directly from the supply tube to the desired location underwater, thus maintaining the integrity of the mix.

By controlling the flow and ensuring that the concrete is placed as close as possible to the bottom, the tremie facilitates a more effective and cohesive bond with the surrounding substrate. This method is particularly important in marine construction, where maintaining the quality of freshly poured concrete is crucial for the structural integrity of underwater structures. So, the correct response highlights the tremie's role in ensuring that concrete maintains its composition and performance even in challenging environmental conditions.