Colloidal concrete is concrete placed underwater using special admixtures that prevent cement washout and maintain cohesion.
How does colloidal concrete work?
When ordinary concrete is poured into water, the cement paste washes out and disperses, leading to severe strength loss and environmental contamination. Colloidal concrete solves this problem through anti-washout admixtures (AWAs) — typically cellulose ethers or polyacrylamide-based polymers — that increase the viscosity of the mix and bind the cement particles together.
The result is a highly cohesive concrete that resists segregation even when flowing through water. The mix maintains its integrity during placement, achieving compressive strengths comparable to concrete cast in dry conditions. The admixtures do not significantly affect the hydration process, so long-term durability remains uncompromised.
Placement methods
Colloidal concrete is typically placed using a tremie pipe that delivers the mix below the water surface, minimising turbulence. In some applications it is pumped directly into submerged formwork. The self-compacting properties of modern colloidal mixes reduce or eliminate the need for vibration underwater.
Applications
- Underwater foundation repairs and sealing
- Construction of bridge piers and caissons
- Filling of cofferdams and sheet-pile enclosures
- Seabed protection layers around offshore structures
- Repair of quay walls and harbour infrastructure
- Plugging of excavation pits below the water table
Related terms
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