Frequently Asked Questions

How does Conbextra EUW cure underwater and what is the mechanism that allows it to bond to wet concrete?

Standard epoxy resins require a dry substrate surface for the polar epoxy molecules to form chemical bonds with the substrate material. Water on the surface of concrete or steel forms a competing polar layer that displaces epoxy molecules from the substrate, preventing bond formation. Conbextra EUW incorporates a specially formulated epoxy base and hardener system with surface-active components that can displace adsorbed water from the concrete and steel surface and form a direct epoxy-substrate bond even in the presence of water. The curing reaction between the epoxy base and the hardener proceeds reliably in the presence of water and does not require oxygen — epoxy cure is a purely chemical (amine-epoxide) reaction that is not inhibited by water in the way that cement hydration can be affected by water dilution. The result is a grout that achieves reliable adhesion and strength development in fully submerged and tidal conditions where conventional products fail.

Can Conbextra EUW be used for underwater injection grouting of cracked submerged concrete structures?

Conbextra EUW is primarily formulated as a filling and bearing grout for void and gap filling in submerged conditions rather than as an injection resin for crack injection. For underwater crack injection, the crack width and the water pressure (head of water driving flow through the crack) are the key parameters determining the appropriate approach. Narrow cracks (less than 0.5 mm) under water pressure are typically addressed with polyurethane injection resins that can be injected under pressure and expand to seal the crack against active water flow. Wider cracks and voids (above 5 mm) in submerged structures where a structural repair is needed are within the range of Conbextra EUW application by injection. For a specific underwater injection grouting query, contact Space Arc Engineering to provide the crack width, depth, water pressure, and structural requirement so the appropriate Fosroc underwater injection or grouting product can be recommended.

What are the logistical requirements for underwater grouting operations using Conbextra EUW?

Underwater grouting operations using Conbextra EUW require specialist diving contractor support, surface mixing and injection equipment, and careful pre-planning of the grouting sequence and quality control. For bagged placement (the diver squeezes pre-filled grout bags into the void), the grout must be mixed on the surface to the correct consistency, transferred into the placement bags, and lowered to the diver within the available pot life before the grout begins to gel. For injection grouting (pumping grout from the surface through a delivery hose to an injection point held by the diver), the pump and hose must be compatible with the epoxy grout viscosity and the injection pressure must be controlled to avoid bursting the formwork or void boundaries. Quality control for submerged grouting is more difficult than for surface operations — visual confirmation of complete void filling requires diver inspection and probing, and post-grouting core sampling through the grouted section is the most reliable confirmation of grout quality.