Fosroc Nitobond SBR50
SBR latex bonding aid and gauging admixture that creates a high-strength bond between fresh repair mortar and existing concrete, while improving waterproofing and durability.
What is it?
A single-component, water-based styrene butadiene rubber (SBR) latex used both as a bonding bridge between old and new concrete and as a gauging admixture mixed into site-batched cementitious mortars, screeds and renders.
Where is it used?
Concrete repair and rehabilitation, floor screeds and toppings, waterproof renders, and as a bonding slurry for slip bricks and tiles, on horizontal, vertical and overhead surfaces.
Why use it?
It improves adhesion of new mortar to existing substrates, raises tensile and flexural strength, reduces permeability for better waterproofing, and resists freeze-thaw and hydrolysis, all from a simple liquid that replaces part of the mixing water.
How is it applied?
Brushed or scrubbed in as an SBR:water:cement slurry primer (bonding bridge), and/or batched into mortar at roughly 10 litres per 50 kg of cement, then the repair mortar is trowel-applied onto the still-wet primer and cured.
About Fosroc Nitobond SBR50
Fosroc Nitobond SBR50 is part of Fosroc’s long-established Nitobond SBR range of styrene butadiene rubber (SBR) latex bonding aids and mortar admixtures. Supplied as a ready-to-use white liquid, it is a modified SBR emulsion designed to upgrade the performance of ordinary site-batched cementitious mortars, screeds, renders and slurries. In Indian repair and rehabilitation practice it is one of the most widely specified bonding agents on concrete repair drawings, used wherever fresh cementitious material must be reliably bonded to existing, hardened concrete.
The product works in two complementary ways. First, as a bonding bridge (or slurry primer), a Nitobond SBR slurry is scrubbed into a prepared, saturated-surface-dry substrate immediately before the repair mortar is placed wet-on-wet. Second, as a gauging liquid, Nitobond SBR partially replaces the normal mixing water inside the mortar itself, modifying the cement matrix so the hardened repair is tougher, less permeable and more flexible than a plain sand-cement mix. Because it is resistant to hydrolysis (re-emulsification in the presence of water), it suits both internal and permanently damp external conditions where ordinary PVA bonding agents would fail.
Within the wider Nitobond SBR family (which on Fosroc’s catalogue includes SBR, SBR20, SBR50, SBR 101/201/202/300 and SBR Latex), the SBR50 designation indicates the higher polymer-solids grade aimed at demanding bonding and waterproofing duties. For contractors, consultants and procurement teams in Delhi NCR and across India, Nitobond SBR50 is a dependable, chloride-free, single-component bonding and admixture solution that integrates cleanly into standard concrete repair systems.
The technical insight
The performance of Nitobond SBR50 comes from the SBR latex film that forms as the cementitious mix cures. The polymer particles coalesce into a continuous, flexible film woven through the cement hydrate matrix, bridging micro-cracks, sealing capillary pores and chemically keying the new mortar to the old substrate. Fosroc’s own BS 6319 testing of an SBR-modified 3:1 sand:cement mortar (10 litres SBR per 50 kg cement) records 62 MPa compressive strength, 3.3 MPa tensile strength, 9 MPa flexural strength and a 53 MPa slant shear bond at 28 days (air cured) – the slant shear figure being the critical proof of monolithic bonding. The reduced permeability that the latex film produces is what gives SBR-modified mortars their waterproofing and freeze-thaw durability, and the same pore-blocking effect limits ingress of aggressive chemicals, acid gases and chlorides. Crucially, the latex is alkali-stable and hydrolysis-resistant, so unlike re-wettable PVA bonding aids it holds up in immersed and permanently damp service.
Where it is used
- Bonding bridge (slurry primer) between hardened concrete substrate and fresh repair mortar in patch repairs
- Polymer modification of site-batched repair mortars for spalled and carbonation-damaged RCC members – beams, columns, slabs, soffits
- Heavy-duty floor screeds and toppings requiring abrasion resistance and good bond to the base slab
- Waterproof renders and plasters on retaining walls, basements, water tanks, sumps and wet areas
- Bonding mortar for fixing slip bricks, ceramic tiles and stone cladding
- Repairs to horizontal, vertical and overhead surfaces, including permanently immersed locations
- Skim and render coats where reduced permeability and freeze-thaw resistance are required
Key advantages
- Excellent bond to concrete, masonry, stonework, plaster and blockwork
- Single-component liquid – simply replaces part of the mixing water, easy to gauge on site
- Improves tensile and flexural strength, allowing thinner, crack-resistant applications
- Reduces permeability for waterproof repairs, renders and toppings
- Resistant to hydrolysis – suitable for internal, external and permanently damp/immersed use
- Highly resistant to freeze-thaw cycling
- Contains no chloride admixtures, protecting embedded reinforcement
- Water-based with no solvents or toxic odour, suitable for enclosed and occupied spaces
- Improves cohesion and workability of the wet mortar
Limitations & considerations
- Not a structural adhesive or standalone waterproof coating – it modifies and bonds cementitious mixes, it does not replace them
- The slurry-primer bonding bridge must still be wet when the mortar is applied; if it dries it must be removed and re-primed
- Should not be applied when temperature is 5 degrees C and falling, nor exposed to moving water or heavy rainfall before final set
- SBR-modified mortars are cement-based and require proper curing immediately after finishing
- For a true substrate/repair barrier or where the substrate stays permanently damp under hydrostatic pressure, an epoxy bonding aid (Nitobond EP) is recommended instead
- Performance depends on correct substrate preparation, dosage and mix design – results vary with site-stored sand moisture and workmanship
- Must be protected from frost in storage
Selection & best practice
Prepare the substrate properly: saw-cut repair edges at least 10 mm deep to avoid feather-edging, break out to a minimum 6 mm, remove all laitance, dust and contamination, and expose and clean any corroded reinforcement (priming exposed steel with Nitoprime Zincrich). Soak the substrate to a saturated-surface-dry (no standing water) condition. Mix a bonding slurry of 1 volume Nitobond SBR : 1 volume clean water : 3 volumes fresh cement, blending cement slowly into the pre-mixed liquid, and scrub it well into the surface without puddling. Apply the SBR-modified repair mortar wet-on-wet onto the still-wet primer – if the primer skins over, grind it off and re-prime. For the mortar, gauge at the recommended dosage (around 10 litres SBR per 50 kg cement), keep added water to a minimum, mix in a forced-action mixer for up to 5 minutes, and cure immediately after finishing with a Fosroc Concure curing compound or polythene sheeting. In Delhi NCR summers (above 35 degrees C), store the drum in shade and use cool mixing water.
Specifications
| Product type | Single-component SBR (styrene butadiene rubber) latex bonding aid and mortar admixture |
| Form / colour | Ready-to-use white liquid emulsion |
| Base | Modified styrene butadiene rubber emulsion, water-based (no solvents) |
| Chloride content | Contains no chloride admixtures |
| Bonding slurry primer mix | 1 vol Nitobond SBR : 1 vol clean water : 3 vol fresh cement (by volume) |
| Typical admixture dosage | Approx. 10 litres per 50 kg cement (repair/patch mortar) |
| Slurry primer coverage | Approx. 2 to 3 m2 per litre (theoretical) |
| Compressive strength (modified mortar, BS 6319, 28d air cured) | 62 MPa |
| Tensile strength (BS 6319, 28d) | 3.3 MPa |
| Flexural strength (BS 6319, 28d) | 9 MPa |
| Slant shear bond strength (BS 6319, 28d) | 53 MPa |
| Application thickness (mortar) | 6 mm min; up to 40 mm (horizontal), up to 15 mm (vertical) per layer |
| Application temperature | Down to 5 degrees C (not falling); warm water in cold, cool water above 35 degrees C |
| Reference standard | Tested to BS 6319 (mechanical properties of resin/polymer mortars) |
| Pack sizes | Commonly 1 L, 5 L, 20 L and 200 L drums (region dependent) |
| Shelf life / storage | 12 months in original unopened pack, dry store; protect from frost |
Industry use cases
Infrastructure / RCC repair
Bonding bridge and polymer-modified mortar for repairing spalled, carbonated or chloride-damaged beams, columns, soffits and slabs in bridges, flyovers and aging RCC structures across Delhi NCR.
Buildings & facades
Re-rendering and patch repairs on plastered walls and facades where a durable, low-permeability, freeze-thaw-resistant render is required.
Water-retaining & basement structures
Waterproof renders and repair mortars for water tanks, sumps, retaining walls and basements that remain permanently damp, where the hydrolysis-resistant SBR latex outperforms PVA bonding agents.
Industrial flooring
Heavy-duty bonded screeds and toppings on factory and warehouse floors needing strong adhesion to the base slab and good abrasion resistance.
Cladding & finishes
Bonding mortar for fixing slip bricks, ceramic tiles and stone to concrete and masonry backgrounds.
Frequently asked questions
Is Fosroc Nitobond SBR50 a real Fosroc product?
What chemical type is it – is SBR a latex?
How do I use it as a bonding agent between old and new concrete?
What dosage do I add to mortar?
When should I use Nitobond EP instead of Nitobond SBR50?
Is Nitobond SBR50 available in Delhi NCR and Pan-India?
How we position Fosroc Nitobond SBR50
Nitobond SBR50 sits in the SBR-latex tier of bonding agents – the everyday workhorse for cementitious repair bonding and waterproof renders, distinct from epoxy bonding aids used for higher-demand, permanently wet or barrier applications. Within Fosroc’s own range it pairs naturally with Nitobond EP (epoxy bonding aid for severe/damp conditions), Renderoc repair mortars, Nitoprime Zincrich (reinforcement primer), Nitobond AR / Concure curing compounds, and Dekguard anti-carbonation coatings to form a complete repair system. Against competitors, credible SBR-latex alternatives commonly specified in India include Sika Latex / SikaLatex Power and Sika’s bonding range, MYK Laticrete bonding agents, Dr. Fixit Pidicrete URP (a widely used SBR), and STP (Bondtite/Krishna Conchem) SBR latexes; for epoxy bonding the comparison would be Sikadur 32 or similar. Nitobond SBR50’s strengths are its proven Fosroc track record, hydrolysis resistance for damp/immersed service, chloride-free formulation and seamless integration with the rest of the Fosroc Renderoc/Nitobond repair system – which is why it remains a default specification on Indian concrete repair projects. Buyers should select the exact Nitobond SBR grade (SBR50 vs SBR20 vs SBR Latex) against the project’s required polymer content and the regional Fosroc datasheet, since pack sizes and minor property values vary by country.
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