Fosroc Nitomortar S
Solvent-free, three-component epoxy reinstatement mortar that patches concrete twice as strong as the parent slab and shrugs off acids, fuels and heavy traffic.
What is it?
A three-component, solvent-free epoxy repair mortar (base, hardener and graded silica aggregate) that cures to roughly 70 N/mm2 compressive strength and resists a broad spread of industrial chemicals.
Where is it used?
Horizontal patch and reinstatement work on industrial floors, chemical and effluent tanks, sea walls, loading bays and bedding applications where abrasion and chemical attack are the real enemies.
Why use it?
You get structural-grade strength that develops in days rather than weeks, near-zero water absorption and genuine acid/fuel resistance in a single trowel-applied product carrying an EN 1504-3 declaration.
How is it applied?
Break out to at least 5 mm, grit-blast and prime with Nitoprime 25 (horizontal) or Nitoprime 28 (vertical), then trowel the mixed mortar 5-50 mm thick per layer onto the tacky primer and close with a steel trowel.
About Fosroc Nitomortar S
Nitomortar S is Fosroc’s high-strength epoxy reinstatement mortar, built for the parts of a structure that take a beating. It arrives as three pre-weighed components: an epoxy resin base, a hardener and a bag of specially graded silica aggregate. On site you combine them into a stiff, trowellable mortar that goes down like a screed but behaves like engineered stone once cured. Because everything is pre-batched, you avoid the guesswork of measuring resins and fillers by eye, which is where a lot of field epoxy work quietly goes wrong. The product is solvent-free, so there is no shrinkage from evaporating carriers and no flammable fumes to manage in a confined tank or basement.
What sets it apart from an ordinary polymer-modified cement patch is the combination of strength, impermeability and chemical resistance. Fully compacted and tight-trowelled, Nitomortar S reaches around 70 N/mm2 in compression, roughly twice the strength of good structural concrete, while its water absorption sits near 0.2 percent against 2-5 percent for the surrounding slab. That density is exactly why it holds up in acid dosing bunds, sugar and effluent tanks, and heavily trafficked plant floors. It is a horizontal-first material: up to 50 mm thick in one pass on floors, but only 6-12 mm on vertical faces, and it should never be used overhead. For those situations Fosroc makes a dedicated high-build sister product, which we cover under positioning below.
The technical insight
The performance comes down to a densely packed, solvent-free epoxy matrix. The base and hardener crosslink into a continuous polymer with almost no interconnected pore structure, and the graded silica aggregate fills the bulk volume so the cured mortar behaves more like a filled composite than a resin. Two things follow. First, load transfers efficiently through the aggregate skeleton, which is why compressive strength lands near 70 N/mm2 and the material carries structural repair methods under EN 1504-3. Second, with so few capillary pathways, aggressive liquids simply have nowhere to travel; the sub-0.2 percent water absorption is the number that predicts real-world chemical durability, because acids, fuels and alkali solutions attack concrete by soaking in and reacting. Strength also arrives fast because epoxy cure is chemical, not hydration-driven, so full cure is reached in about 7 days at 20 C rather than the 28 days a cement system needs, and a floor can be back in service within a working day or two. The trade-off is exotherm and pot life: the same reactivity that gives early strength also means a 45-minute pot life at 20 C, dropping to 20 minutes at 35 C, so Indian site conditions demand disciplined batching and shade.
Where it is used
- Deep patch repair of spalled and delaminated industrial concrete floors up to 50 mm thick in a single pass
- Chemical-resistant reinstatement of acid dosing bunds, effluent tanks and process floors in chemical and pharma plants
- Repair of sea walls, jetties and marine concrete exposed to salts and abrasion
- Arris, edge and joint-nib reinstatement on slabs, loading docks and expansion-joint shoulders
- Bedding mortar for heavy machine bases, rail chairs and steel section fixings
- Reinstatement of sugar-mill, distillery and food-processing floors subject to organic acids
- Emergency running repairs where a plant needs concrete back in service within a day
- Localised strengthening of thin-section concrete where high strength is required over a small footprint
Key advantages
- High ultimate strength around 70 N/mm2, suitable for structural repair use
- Rapid strength gain that minimises plant downtime and lets floors return to service quickly
- Excellent abrasion resistance for forklift and steel-wheel traffic
- Broad chemical resistance to dilute acids, alkalis, sugar solutions, diesel and hydrocarbons
- Very low water absorption near 0.2 percent, giving a dense, near-impermeable repair
- Pre-weighed three-part packs remove site batching error and keep quality consistent
- Solvent-free and non-flammable, safer for tanks, bunds and confined spaces
- Carries an EN 1504-3 declaration covering structural and non-structural repair methods 3, 4 and 7
Limitations & considerations
- Horizontal-biased: single-pass limit is up to 50 mm on floors but only 6-12 mm on vertical faces, and it must not be used overhead
- Short working window, with pot life dropping from about 45 minutes at 20 C to around 20 minutes at 35 C
- Minimum applied thickness is 5 mm, so it is not a skim or feather-edge material
- Requires a primed substrate (Nitoprime 25 or Nitoprime 28) and cannot be trowelled straight onto bare concrete
- Must not be applied below 5 C and falling, or exposed to moving water or heavy rain before final set
- As an epoxy system it is costlier per litre than cementitious repair mortars, so it is best reserved for high-strength or chemically aggressive locations
Selection & best practice
Success is decided at the substrate. Saw-cut the repair perimeter at least 5 mm deep to give a square edge, break out to a minimum 5 mm depth, and grit-blast to remove laitance, oil and corrosion; verify decontamination with a pull-off test. Prime with Nitoprime 25 on horizontal or damp substrates and Nitoprime 28 on vertical or metal ones, then place the mortar while the primer is gelled but still tacky, normally within 30 minutes to 4 hours, re-priming if it cures hard. Mix full packs only, never part packs, using a forced-action mixer for the 16 kg industrial pack. Trowel firmly to fully compact around any exposed steel and close the surface with a steel trowel without overworking it. On large floors work in a chequerboard sequence, and for lifts beyond a single pass scratch-key the intermediate layer and re-prime, applying the next layer between 8 and 24 hours later. In the Delhi NCR summer, store components in shade and batch small quantities to stay inside the shortened pot life; protect fresh work from rain for the first 24 hours.
Specifications
| Composition | Three-component solvent-free epoxy resin, hardener and graded silica aggregate |
| Compressive strength | 70 N/mm2 at 7 days (EN 12190 / BS 6319 Pt 2) |
| Flexural strength | 20 N/mm2 at 7 days (BS 6319 Pt 3) |
| Tensile strength | 10 N/mm2 at 7 days (ASTM C 307) |
| Water absorption | 0.2% (surrounding concrete typically 2-5%) |
| Pot life | 45 minutes at 20 C / 20 minutes at 35 C |
| Applied thickness | 5 mm minimum; up to 50 mm horizontal, 6-12 mm vertical per pass |
| Standard / packs | EN 1504-3 (Class R4, methods 3, 4, 7); 5 kg Standard (2.5 L yield) and 16 kg Industrial (8.0 L yield) packs |
| Shelf life | 12-18 months at 20 C in unopened packs (reduced to 4-6 months at high temperature) |
Industry use cases
Chemical & Pharma Plants
Reinstating acid bunds, dosing areas and process floors where dilute acids, alkalis and solvents would eat through ordinary cement repairs.
Industrial & Warehouse Floors
Deep patching of spalled slabs and joint arrises in forklift-trafficked bays, restoring an abrasion-resistant surface that returns to service in a day or two.
Marine & Coastal Structures
Repairing sea walls, jetties and splash-zone concrete exposed to chloride attack and constant abrasion from waves and grit.
Food, Sugar & Distillery
Rebuilding floors and channels attacked by organic acids and sugar solutions, where a dense, easily cleaned, impermeable surface is essential.
Infrastructure & Precast
High-strength localised repair and bedding of machine bases, rail chairs and heavy fixings where the repair must out-perform the parent concrete.
Frequently asked questions
Is Nitomortar S a structural repair mortar?
Can I use it on vertical faces or overhead?
Do I have to prime the concrete first?
What is the pot life and how does Indian heat affect it?
What pack sizes and coverage should I plan for?
Which chemicals does it actually resist?
How we position Fosroc Nitomortar S
Nitomortar S is our go-to for high-strength, chemical-resistant horizontal repairs. Where the work is vertical or overhead, or needs higher build per pass, specify its sister product Fosroc Nitomortar HB, the lightweight high-build epoxy mortar designed for exactly those locations. For everyday, cost-effective thin-section and large-area patching that is not under aggressive chemical attack, Fosroc Nitomortar FC (fine cementitious mortar) is usually the more economical choice. The system also relies on Fosroc Nitoprime 25 or Nitoprime 28 as the mandatory primer, and Nitocote or Dekguard coatings to protect surrounding areas. Across our other brands, comparable epoxy repair systems from Sika (Sikadur range) and MC-Bauchemie can be matched to a specifier’s approved-vendor list; our team can cross-reference an equivalent on request.
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