Water-cured concrete made with Portland cement is a unique material that can harden even when completely submerged in water. This is because the chemical composition of Portland cement limits the amount of water that can react with it. As a result, concrete made with Portland cement will harden even if it is completely underwater. The curing process (hardening) of concrete takes almost a month and causes the concrete to set.
Paying additional attention to the concrete mix during the curing period helps to increase the structural integrity of the concrete. Installing a boardwalk, dock, offshore platform, port wall, dam, bridge or road over water requires a complicated process for pouring concrete underwater. However, with new innovations, technology and techniques, underwater concrete placement solutions are constantly being redesigned. The type and properties of the materials used must be carefully defined in order to ensure quality concrete during mixing, conveying, laying and curing processes or to alter the characteristics of hardened concrete.
The addition of VMAs (Viscosity Modifying Agents) allows a reduction in the amount of fine powder materials in concrete while its stability, cohesion and robustness are substantially increased. Two special features of underwater concrete need to be carefully controlled; these are self-consolidation to eliminate vibration and rapid build-up of viscosity to control segregation and washing problem. Made from heated clay and lime, Portland cement is the secret of concrete's ability to set underwater. Keeping the end of the supply pipe submerged in concrete is a relatively easy task; however, it can be run incorrectly just as easily due to factors such as inattention, low visibility under water, rough sea, etc.
Most comparisons are based on immersion tests in which a concrete mass is known to be dropped through water several times into a wire cage, and the degree of washing is determined as the percentage of mass loss. Modern concrete, such as self-compacting concrete, underwater concrete or shotcrete, requires very specific rheological properties. Pouring concrete in the rain can compromise its strength, increasing the tendency to develop dust and scale. The technology of underwater concrete has developed dramatically in recent years, so that the mixture can be dosed to ensure high fluidity, as well as high resistance to washing and segregation.