Fosroc Nitomortar UA
A solvent-free, two-part epoxy repair putty that bonds and cures underwater, in tidal zones and on saturated concrete — engineered for marine, drainage and submerged structural repairs.
What is it?
A two-component, solvent-free epoxy resin mortar that mixes to a stiff, trowellable putty and cures underwater or on damp/saturated-surface-dry (SSD) concrete to a dense, impermeable solid stronger than 60 MPa.
Where is it used?
Underwater and splash-zone repairs to concrete and steel — sea walls, jetties, piles, intake structures, sewers, drains, precast assembly and starter-bar/bolt grouting where conditions are wet or submerged.
Why use it?
It is one of the few repair products that bonds and gains strength in the presence of water, eliminating the cofferdams, dewatering and downtime that conventional cementitious mortars demand in tidal or submerged work.
How is it applied?
Equal volumes of colour-coded base and hardener are hand- or trowel-mixed to a uniform grey, worked firmly into a prepared substrate as a thin keying smear then built up to thickness, and left to cure — even underwater.
About Fosroc Nitomortar UA
Fosroc Nitomortar UA is a multi-purpose epoxy repair putty formulated specifically for the situations that defeat ordinary repair mortars: water. Where cement-based and most resin systems need a dry, dewatered substrate to bond and cure, Nitomortar UA is designed to be applied, bonded and cured underwater, in splash and tidal zones, and directly onto saturated-surface-dry (SSD) concrete. That single property makes it a specialist tool for marine and water-retaining infrastructure across India’s coastline, ports, dams, water-treatment plants and sewerage networks.\n\nThe product is supplied as a two-pack, colour-coded system — a white base and a black hardener — pre-weighed in matched quantities for site mixing. The deliberate colour contrast is a built-in quality control: the contractor knows the mix is correct only when an even grey, putty-like consistency is achieved with no streaking. Once mixed, the material handles like a stiff filler that can be pressed and trowelled into spalls, cavities, pipe junctions and joints, and even transported to a submerged work face inside a polythene bag before being kneaded into place by a diver.\n\nOn cure, Nitomortar UA forms a hard, dense, low-permeability solid with compressive strength exceeding 60 MPa and strong adhesion to both concrete and steel. It resists abrasion and impact — important for sea walls and jetties subject to wave and debris battering — and withstands a wide range of acids, alkalis and industrial chemicals, suiting it to effluent channels and process drainage. For Space Arc Engineering’s contractor, consultant and procurement clients in Delhi NCR and across India, it sits in the toolbox alongside Fosroc’s broader Nitomortar and Renderoc repair ranges as the go-to answer whenever a repair cannot be kept dry.
The technical insight
Chemically, Nitomortar UA is an unfilled-to-lightly-filled two-component epoxy in which a moisture-tolerant amine-type curing agent (the black hardener) reacts with the epoxy base (white) to polymerise even when surfaces are wet or submerged. The key to underwater performance is that the resin displaces water from the substrate as it is worked in — the contractor first applies a thin wet-out smear that wets the surface and pushes water aside, then builds the bulk putty onto that keyed layer. Because the cure is a chemical addition reaction rather than hydration or solvent evaporation, no air drying or water loss is required, so strength develops while immersed. The 1:1-by-volume ratio with hard colour coding removes the most common site error (mis-proportioning), and the high mixed specific gravity of roughly 2.0 reflects the dense, void-free matrix that delivers the >60 MPa compressive strength and the chemical/abrasion resistance. The trade-off inherent to this chemistry is temperature sensitivity: below about 5°C the reaction effectively stalls, and the 30-minute pot life at 20°C shortens in warm Indian site conditions, so batches must be sized to what can be placed quickly.
Where it is used
- Permanent patching of spalled and damaged concrete in submerged and underwater locations
- Reinstatement of sea walls, jetties, breakwaters and other structures subject to wave and tidal battering
- Repair of submerged or splash-zone steelwork and reinforced concrete in marine environments
- Fabrication and repair of concrete pipe intersections and general drainage / underground work
- Assembly and repair of precast concrete units, especially where a fast initial cure is needed
- Grouting of starter bars and holding-down bolts, including horizontal and overhead fixings
- Fixing of slip bricks and facing units to concrete substrates
- Sealing and repair of water-retaining structures, intakes, channels and effluent drains exposed to chemical attack
Key advantages
- Bonds and cures underwater and on saturated-surface-dry (SSD) concrete, removing the need for dewatering or cofferdams
- High compressive strength exceeding 60 MPa at 7 days with strong adhesion to concrete and steel
- Two-pack colour coding (white + black to grey) gives an immediate visual confirmation of correct mixing
- Resistant to abrasion and impact for high-wear marine and drainage surfaces
- Withstands a wide range of acids, alkalis and industrial chemicals
- Solvent-free epoxy that can be hand mixed and worked into place without specialist plant
- Fast initial cure (hardens in about 2 hours at 20°C) speeds precast assembly and tidal-window repairs
- Forms a dense, impermeable repair unaffected by many forms of chemical attack
Limitations & considerations
- Will not cure below 5°C; curing time lengthens significantly as temperature falls toward this limit
- Short pot life of about 30 minutes at 20°C, further reduced in hot Indian site conditions, so only small workable batches should be mixed
- Substrate concrete must be at least 14 days old and properly prepared by scabbling or light bush-hammering
- Steel must be grit-blasted to white metal (and degreased if oil-contaminated) before application
- Grey colour may yellow or darken on exposure to sunlight or certain chemicals, so it is a functional repair rather than a colour-matched finish
- As an epoxy putty it is intended for localised patching, fixing and grouting — not for large-volume or flowable structural reinstatement (use a Renderoc or flowable micro-concrete instead)
- Requires correct PPE (gloves) and care that water does not contaminate the components during mixing
Selection & best practice
Prepare the substrate first: remove all grease, oil, chemical contamination, dust, laitance and loose concrete by scabbling or light bush-hammering to expose a sound, well-keyed surface, and ensure the concrete is at least 14 days old; grit-blast steel to white metal and degrease any oil-stained areas beforehand. Mix only what can be placed inside the 30-minute pot life — wearing gloves, blend equal volumes of the white base and black hardener for at least 3 minutes until a uniform, streak-free grey is achieved; in cold weather warm the unopened components in hot water (never letting water enter the mix). On application, always work in a thin wet-out smear first to displace water and wet the surface, then build up to the required thickness; when bonding, coat both faces and hold them rigidly together until set. A smooth finish can be struck off with a wet trowel or cloth before initial cure. For submerged work, carry the mixed putty to the work face in a polythene bag and knead it firmly into place. Always confirm the current product TDS and SDS for the India market and request a method statement from Space Arc Engineering for project-specific submerged or tidal applications.
Specifications
| Product type | Two-component, solvent-free epoxy resin repair putty |
| Primary use | Underwater / damp-environment concrete and steel repair, fixing and grouting |
| Mix ratio | 1 part base : 1 part hardener, by volume |
| Mixed colour | Grey (white base + black hardener; may yellow/darken in sunlight) |
| Pot life | ~30 minutes at 20°C |
| Initial hardness | ~2 hours at 20°C; ~6 hours at 5°C |
| Full cure | 7 days (longer below 20°C) |
| Minimum application temperature | 5°C |
| Compressive strength | >60 MPa at 7 days |
| Specific gravity (mixed) | ~2.0 |
| Substrate condition | Sound concrete ≥14 days old; usable on SSD concrete and underwater; steel grit-blasted to white metal |
| Chemical resistance | Resistant to a wide range of acids, alkalis and industrial chemicals; abrasion and impact resistant |
| Mixing time | Minimum 3 minutes by trowel or hand |
| Pack sizes | Supplied as colour-coded kits; common sizes include 4 L, 6 L and 20 L (varies by market/distributor) |
Industry use cases
Ports, harbours & marine
Patching spalled concrete and reinstating sea walls, jetty beams, piles and breakwater units in the splash and tidal zones without dewatering, including diver-placed repairs to submerged elements.
Water & wastewater infrastructure
Repairing intake structures, channels, sewers and drainage pipe intersections, and sealing chemically attacked surfaces in effluent-handling assets that cannot be taken out of service and fully dried.
Dams, canals & hydraulic structures
Localised underwater patching and crack/cavity filling on permanently or seasonally submerged concrete faces where a moisture-tolerant, high-strength repair is required.
Precast concrete manufacture & erection
Bonding and assembling precast units and fabricating pipe junctions where a fast initial cure shortens the casting-yard or erection cycle.
Structural fixing & anchoring
Grouting starter bars, dowels and holding-down bolts — including horizontal and overhead positions — and fixing slip bricks and facing units to concrete.
Frequently asked questions
Can Fosroc Nitomortar UA really be applied and cured underwater?
What is the mixing ratio and how do I know the mix is correct?
How strong is it and how long does it take to cure?
How should the concrete and steel be prepared before application?
What is the pot life and how much should I mix at once?
How does Nitomortar UA differ from other Fosroc Nitomortar grades?
How we position Fosroc Nitomortar UA
Within the Fosroc concrete-repair portfolio that Space Arc Engineering supplies, Nitomortar UA occupies a narrow but important niche: the moisture-tolerant, underwater-curing epoxy putty. It is not a general patch mortar — for routine dry-substrate hand-applied repairs the cementitious Renderoc HB/S range or epoxy grades like Nitomortar FC and Nitomortar PE are more economical, and for large-volume or flowable reinstatement a Renderoc micro-concrete is the correct choice. Nitomortar UA earns its place only where water is unavoidable: tidal zones, submerged elements, wet sewers and saturated concrete. It pairs naturally with Fosroc’s wider system — Nitoprime / Nitozinc primers for reinforcement protection, Renderoc fairing coats for finishing, and Conbextra epoxy grouts for larger anchoring volumes. Among competitors available in India, the closest functional alternatives are Sika’s underwater/SSD-tolerant epoxy mortars (e.g. the Sikadur range), MBS (formerly MBT/BASF Master Builders) epoxy repair systems, STP (Shalimar Tar Products) and, in the broader waterproofing-and-repair retail space, Dr. Fixit. Specifiers should compare the relevant current TDS values — pot life, minimum temperature, compressive strength and, critically, the manufacturer’s explicit underwater-cure endorsement — rather than assume parity, since few products genuinely match Nitomortar UA’s ability to be placed and cured fully submerged. Space Arc Engineering, as an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India, can advise on grade selection and provide project-specific method statements.
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