About Fosroc Conbextra EUW

Conbextra EUW answers a question every dam, water-treatment and marine engineer eventually faces: how do you inject a structural crack when the structure cannot be taken out of service and the concrete cannot be dried? Ordinary epoxy injection resins lose adhesion the moment they meet moisture. Conbextra EUW is built the other way around — its base and hardener are formulated to be water insensitive, so the mixed resin wets and grips damp or submerged concrete instead of being repelled by it. The neat resin is thin enough to be pumped into cracks as fine as 0.25 mm and works in gaps up to 10 mm.

The same 1.5 litre pack stretches further than an injection resin normally would. Blended with clean graded quartz sand up to 1:3.5 by weight, it becomes a pourable grout for gaps beyond 10 mm; extended up to 1:7 with a heavy-duty mixer, it turns into an underwater epoxy repair mortar for reprofiling eroded or spalled sections. For contractors, that is one material covering injection, grouting and patch repair on wet structures — with the technical backing of Fosroc Chemicals (India) and supply through Space Arc Engineering across Delhi NCR and pan-India.

The technical insight

The chemistry that matters here is surface wetting. On damp concrete, a conventional epoxy emulsifies at the bond line — water occupies the substrate surface first, the amine hardener reacts with moisture, and adhesion collapses. Conbextra EUW’s resin-hardener pair is engineered so the mixed epoxy preferentially displaces the water film and makes direct contact with the crack walls. The proof sits in the test data: a 28 N/mm² bond strength at 7 days to ASTM C882 — a figure many epoxies cannot reach even on dry substrates. Low mixed viscosity (density 1.135-1.145 g/cc) lets pump pressure drive the resin deep into 0.25 mm cracks, while low creep keeps the cured section stable under sustained structural load. One caution: like all epoxies it generates heat as it cures, and the exotherm grows with pour volume — which is exactly why Fosroc specifies quartz extension for larger sections rather than mass-pouring neat resin.

Where it is used

• Pressure injection of structural cracks 0.25-10 mm wide in wet, damp or submerged concrete
• Crack injection in dams, spillways, stilling basins and inspection galleries under active seepage
• Underwater fillerised grouting of voids, gaps and honeycombed pockets using graded quartz filler
• Underwater epoxy repair mortar (quartz-extended up to 1:7) for eroded or spalled tidal-zone and submerged concrete
• Sealing leaking cracks in water-retaining structures – reservoirs, intake wells, ETP/STP tanks – without emptying them
• Repairs to jetties, wharves, quay walls and other marine structures exposed to seawater
• Gap filling beyond 10 mm as a quartz-sand-extended grout (up to 1:3.5 by weight)
• Crack injection in basements, sumps and tunnels where the substrate can never be fully dried

Key advantages

• Water insensitive – injects, bonds and cures on saturated and fully submerged concrete, eliminating dewatering costs
• Fast structural turnaround: 30 N/mm² compressive strength at 1 day (ASTM D695)
• High ultimate strengths – 80 N/mm² compressive, 42 N/mm² flexural and 21 N/mm² tensile at 7 days
• Outstanding 28 N/mm² bond strength to concrete at 7 days (ASTM C882)
• Low viscosity gives fast, convenient pumping and penetration into cracks as fine as 0.25 mm
• Low creep characteristics – suitable for cracks in structurally loaded members
• Resists oil, grease, fats, mild acids and alkalis, fresh water and seawater
• One pack, three uses – neat injection resin, quartz-filled grout, or underwater repair mortar

Limitations & considerations

• Pot life is only 20 minutes at 30°C – and shorter in peak Indian summer, so batch sizes and pump logistics must be planned tightly
• Neat resin suits 0.25-10 mm gaps only; wider sections must be extended with graded quartz sand, which adds a site-batching step
• Epoxy exotherm rises with pour volume – unfilled mass pours risk high peak temperatures and should be avoided
• Published values are from 20°C laboratory testing; hot substrates and site conditions will shift working time and strength-gain rates
• Resins can cause skin sensitisation, and the Nitoflor Sol cleaning solvent is flammable (flash point 33°C) – PPE and ventilation are mandatory
• Supplied in 1.5 litre packs, so large injection programmes need disciplined multi-pack batching

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Conbextra EUW

Conbextra EUW is the wet-condition specialist within Fosroc’s Conbextra grout family. For conventional dry-condition work, the same family covers the full spectrum: Conbextra EP and Conbextra EP10 for high-performance epoxy grouting under machine bases and dynamic loads, and Conbextra GP2 for general-purpose cementitious non-shrink grouting. For crack injection in dry or merely damp structures, Fosroc Nitofill LV is the lower-cost first choice — reserve EUW for genuinely wet and submerged substrates. Very fine live leaks below EUW’s 0.25 mm injection limit are usually better handled by polyurethane injection systems, which we supply from our MC-Bauchemie range. Space Arc Engineering stocks the complete Fosroc grouting and injection line alongside Sika, MC-Bauchemie and Dr. Fixit alternatives, and our applications team can help match the resin system to the crack survey before material is ordered.

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