Underwater Concrete

Underwater concrete is specifically designed for underwater port and harbor installation, bridge piers in rivers, water industry, and metro structures. Concrete needs to be resistant to washout, segregation, and to bleeding. The concrete mix design, shape, and gradation of the aggregates, choice of admixtures, vibration, and placement conditions are all factors that impact concrete performance in a water environment. Concrete laid underwater should not be compacted. Contractors use what is a funnel-shaped hopper commonly known by the French word “tremie” to pour the concrete by gravity feed, through a vertical steel pipe of about 25 cm diameter pipe extending from the surface above the water to the underwater floor, with the lower end continuously submerged in fresh concrete. The lower end of the pipe is closed with a check valve before inserting it into the water. Concrete is poured, displacing air and water present in the pipe to reach the bed.

The tremie is continuously lifted as work proceeds, with the lower of the pipe kept covered by the concrete that is being poured. Concrete gets automatically compacted by the hydrostatic pressure of water.

Holderchem supplies a range of products for underwater concreting, including high range water reducers, and anti-washout admixtures, which are designed to prevent washing out and segregation of concrete during underwater placement. These products can be supplied from concrete plants with monitoring and control and delivered in mixer trucks with options for chute discharge, conveyor belts, or concrete pumps.