MC-Bauchemie MC-Nafufill BF
A polymer-modified cementitious bonding slurry that locks fresh repair mortar onto prepared concrete for a monolithic, fully bonded patch.
What is it?
A single-component, polymer-modified cementitious bonding slurry and interface primer that you mix with water on site and scrub into a prepared concrete substrate before applying MC-RocTec and Nafufill repair mortars.
Where is it used?
On saw-cut, roughened repair patches in RCC structures, water-retaining and wastewater structures, bridge and flyover soffits, columns, beams and industrial floors ahead of a cementitious repair layer.
Why use it?
It converts the mortar-to-substrate interface from the weakest link in a repair into a high-strength bond, lifting pull-off values well past the EN 1504-3 requirement and forcing failure into the parent concrete rather than at the joint.
How is it applied?
Mix to a lump-free slurry, then scrub one thin coat firmly onto the saturated-surface-dry substrate with a stiff brush and place the repair mortar wet-on-wet while the slurry is still tacky.
About MC-Bauchemie MC-Nafufill BF
MC-Nafufill BF is the bonding coat that MC-Bauchemie designed to sit between a prepared concrete substrate and its RocTec and Nafufill repair mortars. It arrives as a factory-blended powder of cement, selected polymer and graded fillers, so the only site variable is the water you add. That single-component format matters on a busy site: there is no second liquid to gauge, no field ratio to get wrong, and no risk of a crew building a bond coat that is inconsistent from patch to patch. Once mixed to a smooth, brushable slurry, it is worked hard into the open pore structure of the substrate, where the polymer improves wetting and the cement fraction begins to co-hydrate with the fresh mortar placed over it.
For engineers and applicators, the appeal is simple. A concrete repair is only as durable as the plane where new material meets old, and that plane is where most patch failures begin, debonding, drumminess and eventual water tracking behind the repair. MC-Nafufill BF is engineered specifically to strengthen that plane. It is not a general-purpose latex or a waterproofing product; it is a purpose-made interface primer that ties a defined family of repair mortars to concrete so the finished repair behaves as one continuous element rather than a shell stuck onto a wall. On projects where a repair has to be signed off against EN 1504 principles, that predictable, testable bond is exactly what a consultant wants to see.
The technical insight
The bond in a mortar repair is governed by what happens in the first few millimetres at the interface. On a bare, even well-prepared, substrate the fresh mortar’s own mix water is drawn into the thirsty concrete, leaving a starved, porous, poorly hydrated skin exactly where strength is needed most; pull-off values on that plane typically sit around 0.5 to 0.8 MPa. MC-Nafufill BF changes the physics of that contact. Its polymer fraction lowers surface tension and keeps the slurry film continuous across the pore mouths, so it wets the substrate instead of being sucked flat, while the cement in the slurry hydrates into the same crystalline network as the mortar placed on top. The result is a continuous, co-hydrated bridge rather than two dry faces pressed together, and measured pull-off strengths rise into the 1.5 to 2.5 MPa range with failure occurring cohesively inside the parent concrete, the signature of a bond stronger than the substrate itself. This is also why the timing rule is non-negotiable: the slurry has to be tacky-wet when the mortar goes on. Let the film dry and it becomes a thin, weak, dusty layer that does the opposite of its job, so the mortar must follow the brush wet-on-wet.
Where it is used
- Interface primer coat before MC-RocTec R2, R3 and R4 structural repair mortars on RCC
- Bonding coat ahead of MC-Nafufill FM micro-concrete and Nafufill repair mortars
- Bond promotion on bridge and flyover soffits, piers and crash barriers during rehabilitation
- Repair of columns, beams and slabs in commercial and industrial buildings
- Priming saw-cut and roughened patches on water-retaining and wastewater structures
- Substrate preparation on precast units and marine or coastal RCC before mortar patching
- Interface bonding on industrial floors and plinths prior to a cementitious repair layer
- Preparation coat on delaminated or spalled cover concrete flagged in a condition survey
Key advantages
- Single-component powder, water only on site, so there is no field mixing ratio to get wrong
- Lifts interface pull-off strength into the 1.5 to 2.5 MPa band with failure inside the parent concrete
- Formulated as a matched system with MC-RocTec and Nafufill mortars for predictable, testable bond
- Complies with the bonding requirements of EN 1504-3 and is verified by EN 1542 pull-off testing
- Brush-applied, needing only stiff brushes and standard mixing gear rather than specialist plant
- Works on vertical, overhead and horizontal patches, suiting soffit and column repairs
- Consistent factory blend removes the patch-to-patch variability of site-gauged latex slurries
- Low film thickness as a thin scrub coat means it adds negligible dimension to the repair build-up
Limitations & considerations
- It is a bond coat, not a repair mortar, so it does no filling or structural rebuilding on its own
- The tacky-wet window is short, so mortar must follow immediately; dried film must be removed and reapplied
- Performance depends entirely on correct substrate preparation to a sound, roughened, saturated-surface-dry face
- Pot life is only about 30 to 45 minutes at 25 degrees Celsius and shortens further in hot Indian summer conditions
- Best results are with the matched MC-RocTec and Nafufill mortars; pairing with unrelated systems is not its design intent
- It provides no standalone waterproofing or chemical-resistance function beyond promoting the bond
Selection & best practice
Preparation decides the outcome. Break out all unsound and delaminated concrete, expose corroded reinforcement, treat the steel, and roughen the substrate to a sound, open profile free of laitance, dust, oil and curing compound. Bring the substrate to a saturated-surface-dry condition, damp but with no standing water or glistening film, before priming. Mix MC-Nafufill BF with clean water to a smooth, lump-free brushable slurry, adding powder to water and mixing with a slow-speed drill and paddle; discard any batch that has stiffened past its roughly 30 to 45 minute pot life at 25 degrees Celsius rather than re-tempering it. Scrub a single thin coat firmly into the surface with a stiff brush so it is driven into the pores rather than laid over them, working an area you can overlay within the tacky-wet window. Place the MC-RocTec or Nafufill mortar wet-on-wet while the bond coat is still tacky; never let it skin or dry. In hot or windy conditions reduce the primed area per batch, shade the work and keep the substrate damp. Cure the completed repair per the mortar datasheet.
Specifications
| Product type | Single-component, polymer-modified cementitious bonding slurry / interface primer |
| Base | Portland cement, polymer and graded fillers (factory-blended powder) |
| Standard | Meets bonding requirements of EN 1504-3 |
| Bond verification | EN 1542 pull-off testing |
| Coverage | Approx. 1.0 to 1.5 kg/m2 as a single thin bonding coat |
| Interface pull-off (with BF) | Approx. 1.5 to 2.5 MPa, cohesive failure in substrate |
| Pot life | Approx. 30 to 45 minutes at 25 degrees Celsius |
| Mixing | Add clean water on site to a lump-free brushable slurry |
| Application | Stiff brush, one coat, mortar placed wet-on-wet while tacky |
Industry use cases
Bridges and Infrastructure
Priming soffits, piers and crash barriers before MC-RocTec patch repairs during flyover and bridge rehabilitation, giving a bond that survives traffic vibration and weather.
Water and Wastewater Structures
Bonding coat on saw-cut patches in tanks, STPs and treatment structures where a fully monolithic, non-delaminating repair is essential before the lining or repair mortar.
Commercial and Industrial Buildings
Interface priming for column, beam and slab repairs so cover-concrete patches stay bonded under load and thermal movement over the building’s life.
Precast and Marine RCC
Substrate priming on precast units and coastal structures before mortar patching, resisting the chloride-driven debonding common in aggressive environments.
Industrial Floors and Plinths
Bond promotion before cementitious repair layers on plant floors and machine plinths, keeping the repair keyed down under point loads and abrasion.
Frequently asked questions
What exactly is MC-Nafufill BF and what does it do?
Why not just apply the repair mortar directly onto the concrete?
How much MC-Nafufill BF do I need per square metre?
Can I let the bond coat dry before applying the mortar?
Is it compliant for standards-based concrete repair?
Does MC-Nafufill BF work with any repair mortar?
How we position MC-Bauchemie MC-Nafufill BF
MC-Nafufill BF is the interface primer within MC-Bauchemie’s concrete-repair system, so it is naturally specified alongside the repair mortars it is built for, MC-RocTec 20/30/50, MC-RocTec FFC for structural patching and MC-Nafufill FM micro-concrete for larger reinstatements, with MC-Nafufill TP where a matched mortar is needed. Pair it with a suitable MC-Bauchemie reinforcement primer where corroded steel is exposed, and with an MC-Bauchemie protective or anti-carbonation coating to finish the rehabilitated element. Where a project is standardised on Fosroc rather than MC-Bauchemie, Space Arc supplies the equivalent Fosroc repair line so the specifier gets a single-source, warranty-consistent system rather than mixing families across the interface.
Fosroc Nitobond SBR — Choose Nitobond SBR when the project is standardised on Fosroc or a crew prefers a ready-to-use liquid SBR that doubles as both a site-gauged bonding slurry and a mortar-gauging admixture, rather than a single-component powder tied to the MC-Bauchemie mortar family.
Related Concrete Repair products
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