Fosroc Nitobond SBR 300
Single-component styrene-butadiene rubber (SBR) latex bonding aid and gauging liquid that turns site-batched sand-cement into a tough, low-permeability, well-bonded repair mortar, screed or slurry coat.
What is it?
A modified styrene-butadiene rubber (SBR) emulsion supplied as a ready-to-use white liquid. It is a single-component bonding aid and gauging liquid for cementitious systems, resistant to hydrolysis so it works for external as well as internal exposure.
Where is it used?
Concrete repair and rehabilitation across India – polymer-modified patch and repair mortars, floor screeds and toppings, bonding bridges between old and new concrete, waterproof renders and plasters, and slurry base coats ahead of waterproofing.
Why use it?
It gives a strong bond to concrete, masonry and stonework, sharply cuts permeability to water and chlorides, and improves the tensile and flexural behaviour of the mortar so repairs resist cracking and last longer – all from one easy-to-gauge liquid.
How is it applied?
Used two ways: scrubbed into a primed substrate as an SBR:water:cement bonding slurry, and gauged into the sand-cement mix as a partial replacement for mixing water at roughly 5-9 litres per 50 kg cement (or 10 L/50 kg for high-performance mortar). The repair is applied wet-on-wet onto the still-wet slurry.
About Fosroc Nitobond SBR 300
Fosroc Nitobond SBR 300 is a styrene-butadiene rubber (SBR) latex – a milky-white polymer emulsion that contractors add to ordinary sand-cement mixes to upgrade them into engineered repair mortars, screeds and bonding coats. It belongs to Fosroc’s long-established Nitobond family of bonding agents and is positioned as the workhorse, economical SBR latex within that range. In a typical Indian concrete-repair scenario – a spalled column, a delaminated slab soffit, a worn industrial floor, or a leaking terrace junction – a freshly mixed sand-cement mortar bonds poorly to the hardened substrate and stays porous. Nitobond SBR 300 solves both problems at once: brushed in as a slurry, it acts as a bonding bridge that grips the old concrete; gauged into the mortar, the polymer film cures within the matrix to reduce permeability, raise flexural and tensile strength, and reduce shrinkage cracking. Because the emulsion is resistant to hydrolysis (chemical breakdown by water), it does not soften or wash out in damp and external conditions, which is why it is specified for terraces, external plaster, plinth protection and water-retaining repairs as well as interior work. It is supplied as a single component that the applicator simply gauges as required – there is no separate hardener or activator to weigh, which keeps it forgiving on site. The product is compatible with all common hydraulic cements (OPC and PPC), is non-flammable, and contains no added chloride, so it will not introduce corrosion risk to embedded reinforcement. For a Delhi-NCR or pan-India contractor, it is one of the most familiar and widely stocked items in the construction-chemicals cupboard, used daily for everything from minor patch repairs to full screed laying.
The technical insight
The chemistry that matters is the SBR co-polymer film. When the gauged mortar is placed, cement hydration consumes the mixing water while the SBR particles coalesce into a continuous, flexible polymer network that interpenetrates the cement matrix and lines the capillary pores. Two practical outcomes follow. First, the pore network is partly blocked and made discontinuous, which is why an SBR-modified mortar is markedly less permeable to water and to chloride and carbon-dioxide ingress – the same mechanism that protects embedded steel and slows carbonation. Second, the polymer bridges micro-cracks and adds tensile and flexural capacity, so the brittle cement matrix behaves more like a tough composite; Fosroc’s own characterisation of a 3:1 sand:cement mortar gauged at 10 litres SBR per 50 kg cement, tested to BS 6319 and air-cured at 28 days, reports compressive strength of about 62 MPa, tensile strength about 3.3 MPa, flexural strength about 9 MPa and slant-shear bond around 53 MPa – figures that illustrate the order-of-magnitude uplift the polymer provides over an unmodified control. The single most common site error is letting the bonding slurry skin over before the topping goes on: once the slurry dries it loses its bonding action and must be removed and the substrate re-primed. Everything in the system depends on the wet-on-wet rule, on minimising added water (excess water dilutes the polymer film and the strength gain), and on proper curing of the finished mortar to stop the polymer from drying too fast.
Where it is used
- Polymer-modified patch and repair mortars for worn, damaged and spalled concrete – columns, beams, slab soffits and plinths
- Floor screeds and toppings (10-25 mm) with improved abrasion resistance and reduced dusting
- Bonding bridge / slurry coat between old hardened concrete and new repair mortar or fresh concrete
- Waterproof and cohesive renders and plasters on masonry, internal and external
- Impermeable slurry base coat as a substrate preparation step ahead of waterproofing membranes
- Polymer-modified cement grout for crack injection at a dosage in the region of 4 litres per bag of cement
- Repair and rendering on brick, stone and block masonry where low permeability is needed
- Tanking-style protective screeds for plinths, sunken areas and water-contact surfaces (consult Fosroc for permanently immersed conditions)
Key advantages
- Single component – simply gauged as required, no separate hardener to weigh or proportion
- Excellent bond to concrete, masonry, stonework and plaster, used both as a slurry primer and a mortar additive
- Substantially reduces permeability to water and to chlorides and other aggressive agents, protecting embedded reinforcement
- Improves tensile and flexural properties, reducing shrinkage and cracking in the cured mortar
- Resistant to hydrolysis, so suitable for external and damp exposure as well as internal work
- Contains no added chloride and is non-flammable, with low handling risk on site
- Compatible with all common hydraulic cements (OPC/PPC) and standard site mixing equipment
- Economical, widely stocked SBR latex – cost-effective for high-volume screeding and repair work
Limitations & considerations
- Not a structural adhesive on its own – it is a mortar modifier and bonding aid; for permanently damp or immersed bonding, Fosroc directs users to an epoxy bonding aid (Nitobond EP) and to consult the local Fosroc office
- Performance is wet-on-wet dependent: if the bonding slurry dries before the topping is applied it must be removed and the surface re-primed
- Strength and impermeability gains are lost if too much gauging water is added – water must be kept to the practical minimum
- Minimum application temperature is around 10 C; uncured mortar must be protected from frost and not re-tempered after initial set
- Requires proper surface preparation – a clean, sound, mechanically keyed substrate free of laitance, dust, oil and corrosion deposits
- Finished mortar still needs conventional curing (e.g. a curing compound such as Concure WB) to develop full properties
- Being SBR-based, it does not match the chemical resistance or bond of an epoxy system for aggressive-chemical or heavy-duty bonding duties
Selection & best practice
Prepare the substrate to a clean, sound, mechanically roughened surface free of laitance, dust, oil and corrosion; expose and clean any corroded steel and prime it (e.g. Nitozinc / zinc-rich primer) before bonding. Pre-soak the concrete with clean water and remove standing water. Brush in a bonding slurry of roughly 1 part Nitobond SBR 300 : 1 part water : 3 parts fresh cement, blending cement slowly into the liquids and stirring to prevent settlement; avoid puddling. Apply the gauged repair mortar wet-on-wet onto the still-wet slurry – never let the slurry skin over. Use a typical patch/plaster mix of 50 kg cement : 150 kg Zone II sand : 5-9 litres SBR 300 with 11-15 litres water (8-20 mm thickness), or a screed mix of 50 kg cement : 75 kg 3-6 mm chips : 75 kg sand : 5-9 litres SBR 300 (10-25 mm), keeping the screed to a semi-dry cohesive consistency. Keep added water to the minimum needed and reduce it further if the sand is wet. Toe-in at edges to avoid feather-edging, cure the finished mortar (e.g. with Concure WB), protect from frost, and do not re-temper after initial set.
Specifications
| Chemical type / system | Modified styrene-butadiene rubber (SBR) emulsion / latex |
| Form & colour | Single-component ready-to-use liquid, white (milky) emulsion |
| Function | Bonding aid (slurry bridge) and gauging liquid / mortar & screed modifier |
| Bonding slurry mix | ~1 vol SBR 300 : 1 vol water : 3 vol fresh cement (by volume) |
| Patch / repair mortar mix | 50 kg cement : 150 kg Zone II sand : 5-9 L SBR 300 : 11-15 L water; thickness 8-20 mm |
| Screed mix | 50 kg cement : 75 kg 3-6 mm chips : 75 kg Zone II sand : 5-9 L SBR 300 : 8-12 L water; thickness 10-25 mm |
| Crack-injection grout dosage | Approx. 4 litres SBR 300 per bag of cement |
| Slurry primer coverage | Approx. 4-5 m² per litre (depending on substrate porosity) |
| Minimum application temperature | Approx. 10 C (protect uncured mortar from frost) |
| Chloride content | No added chloride admixtures |
| Reaction to fire | Non-flammable |
| Compressive strength (indicative, SBR-modified 3:1 mortar, BS 6319, 28-day air-cured) | ~62 MPa (N/mm²) |
| Flexural / tensile strength (indicative, same mortar) | ~9 MPa flexural / ~3.3 MPa tensile |
| Slant-shear bond (indicative, same mortar) | ~53 MPa |
| Pack sizes | 1, 5 and 20 litre containers |
| Shelf life | 12 months in a dry store, unopened |
| Manufacturer / TDS ref | Fosroc Chemicals (India) Pvt. Ltd. – INDIA/2020/0906/A |
Industry use cases
Concrete repair & rehabilitation
Patching spalled and delaminated RCC columns, beams and slab soffits in ageing buildings and bridges, using SBR 300 as both the bonding bridge and the mortar modifier to restore cover and cut chloride re-ingress.
Industrial & warehouse flooring
Laying and repairing 10-25 mm polymer-modified screeds and toppings that resist abrasion, reduce dusting and bond reliably to the existing slab in factories, godowns and logistics parks across NCR.
Waterproofing & terraces
Applying impermeable slurry base coats and waterproof renders on terraces, sunken slabs, plinth protection and water tanks as a preparatory layer before membrane or coating systems.
Masonry & plaster works
External and internal renders/plasters on brick and stone masonry where a tough, low-permeability, crack-resistant finish is required on residential and commercial facades.
Infrastructure & precast
Bonding new concrete or repair mortar to old in water-retaining structures, drains, channels and precast remediation, with SBR 300 improving durability and bond at junctions.
Frequently asked questions
Is Fosroc Nitobond SBR 300 a real Fosroc product?
What is the difference between Nitobond SBR 300 and Nitobond EP?
How much Nitobond SBR 300 do I add per bag of cement?
What coverage should I expect from the bonding slurry?
Can Nitobond SBR 300 be used outdoors and in wet areas?
What is the shelf life and pack size, and how should it be stored?
How we position Fosroc Nitobond SBR 300
Within the Fosroc system, Nitobond SBR 300 is the economical, everyday SBR latex for general-purpose bonding, screeding and rendering – it pairs naturally with Renderoc and other Fosroc repair mortars for patch repairs, with Nitozinc / zinc-rich primer for reinforcement protection, with Concure WB for curing the finished mortar, and with Nitobond EP where a stronger two-part epoxy bonding bridge is needed (permanently damp substrates, high-performance structural bonds) or Nitobond AR as an acrylic alternative for thin bonding and curing duties. Choosing between them is mainly a matter of duty: SBR 300 for cost-effective, high-volume mortar modification and bonding; epoxy where chemical resistance, immersion or maximum bond govern. In the wider Indian market it competes directly with Sika Latex / Sika Latex Power and SikaTop bonding products, with MYK/MBS (formerly MBS) SBR latexes, with Pidilite Dr. Fixit Pidicrete URP, and with STP / Sunanda construction-chemical SBR offerings – all credible alternatives with broadly similar SBR or acrylic-SBR chemistry. As an authorised Fosroc distributor and applicator serving Delhi NCR and pan-India, Space Arc Engineering recommends Nitobond SBR 300 where clients want the proven Fosroc Nitobond system and consistent supply, and we are happy to advise when an epoxy or specialist alternative is the better technical fit for a given repair.
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