MC-Bauchemie MC-Contact
A polymer-modified cementitious bonding slurry from MC-Bauchemie, brushed onto prepared concrete so the patch mortar grips the parent surface instead of peeling away from it.
What is it?
A cement-and-polymer bonding slurry (bonding bridge) that is scrubbed into a repair area to create an adhesive interface between old concrete and fresh repair mortar.
Where is it used?
The intermediate coat in concrete patch-repair and rehabilitation work — spalled slabs, columns, beams, bridge soffits, precast units and screed overlays.
Why use it?
It stops the classic failure of repair mortar debonding, hollowing or dropping off vertical and overhead faces by giving the mortar a chemically active surface to hold onto.
How is it applied?
Site-mix the powder and polymer to a lump-free slurry, scrub it hard into a clean, saturated-surface-dry substrate, and place the repair mortar wet-on-wet before the slurry skins over.
About MC-Bauchemie MC-Contact
MC-Contact belongs to the family of bonding slurries that quietly decide whether a concrete repair lasts twenty years or fails in two monsoons. On paper a patch repair looks simple — cut out the damage, trowel in fresh mortar — but the weakest link is almost always the joint between the old concrete and the new material. A stiff, poorly bonded mortar shrinks as it cures and lets go of a smooth or dusty substrate, leaving a hollow patch that sounds drummy under a hammer and eventually spalls off. MC-Contact is the coat that engineers brush into that joint to make it disappear.
It is a two-component product: a cementitious powder blended with fine fillers, gauged on site with an SBR or acrylic polymer dispersion. Mixed together they form a rich, brushable slurry that is worked into the open pores of the prepared concrete. The cement fraction hydrates into the substrate the way any bonding mortar does, while the polymer film bridges the interface and keeps the slurry flexible and adhesive during the critical wet-on-wet window. Applied correctly as part of an MC-Bauchemie repair build-up, it lets the repair mortar behave as if it were cast monolithically with the parent structure. For Delhi NCR and pan-India projects, Space Arc supplies it alongside the compatible MC repair mortars so the whole system is sourced and specified as one.
The technical insight
A bonding slurry works on two mechanisms at once, which is why a simple brush coat outperforms placing mortar straight onto bare concrete. Mechanically, the freshly scrubbed slurry is forced into the surface porosity and micro-roughness of the prepared substrate, so once it sets it is keyed into the concrete rather than merely resting on it. Chemically, the polymer dispersion coalesces into a continuous film as the water leaves, and that film has genuine tack — it grips both the old concrete and the fresh mortar placed against it, and it stays slightly flexible so it can absorb the differential movement and shrinkage stress that would otherwise crack a rigid glue line. The reason application discipline matters so much is timing. The slurry only bonds the two layers if the repair mortar is placed while it is still wet and open; if it is allowed to dry and skin over, it becomes a debonding layer instead of a bonding one, and the mortar sits on top of a cured film with almost no grip. The other half of the equation is the substrate: the slurry can only transfer load into concrete that is sound, so the surface must be cut back to a strong, clean, saturated-surface-dry base with the pore water absorbed but no free water shining on top.
Where it is used
- Bonding coat between prepared concrete and MC-Bauchemie repair mortars in patch-repair work
- Spalled and delaminated cover concrete on slabs, beams and columns
- Bridge deck, soffit and pier repairs where debonding on overhead faces is the main risk
- Repair and reinstatement of precast and cast-in-situ concrete elements
- Priming and bonding of cementitious screeds and floor toppings to an existing concrete base
- Rehabilitation of RCC water-retaining and effluent structures as part of a lined repair system
- Reprofiling of honeycombed or form-marked concrete before a levelling mortar
- Interface coat under render and thick plaster on difficult, low-suction concrete substrates
Key advantages
- Turns the weakest part of a repair — the old-to-new joint — into a keyed, chemically active bond
- Sharply reduces debonding, drumminess and mortar drop-off on vertical and overhead surfaces
- Polymer film stays flexible, so it absorbs shrinkage and thermal movement instead of cracking
- Simple brush or scrub application with ordinary site tools — no specialist plant or heat
- Site-gauged two-part system gives a consistent, workable slurry every batch
- Formulated to sit within an MC-Bauchemie repair build-up, so the whole system is compatible and single-sourced
- Suitable across buildings, bridges, precast and water-retaining structures from one product
- Supplied with technical and application support by Space Arc across Delhi NCR and pan-India
Limitations & considerations
- It is a bonding aid, not a repair mortar or a waterproofing coat — it never replaces the patch material or a membrane
- The bond only forms if the repair mortar is placed wet-on-wet; letting the slurry dry or skin over turns it into a debonding layer
- Performance is capped by the substrate — it cannot rescue weak, laitance-covered, oily or unsound concrete that has not been properly cut back
- Substrate must be saturated-surface-dry: standing free water dilutes the slurry, while a bone-dry surface sucks water out and burns the bond
- As a cementitious system it needs above-freezing temperatures and protection from rapid drying, direct sun and wind during cure
- Mixed slurry has a limited working life and cannot be re-tempered with extra water once it starts to stiffen
Selection & best practice
Preparation carries the job. Cut back all loose, cracked and delaminated concrete to a sound, mechanically-roughened base, expose and clean any corroded reinforcement, and remove dust, laitance, oil and curing compound. Pre-soak the substrate and bring it to a saturated-surface-dry condition — damp and dark, but with no water pooling on the surface. Gauge the powder into the polymer (not the other way round) and mix mechanically to a smooth, lump-free, brushable slurry with no dry pockets. Scrub the slurry firmly into the surface with a stiff brush so it is worked into the pores rather than laid on thinly, covering every face of the repair including the back and sides of the cut-out. Then place the repair mortar wet-on-wet, while the slurry is still glossy and tacky — never let it dry, film over or dust before the mortar goes on; if it does, remove it and reapply. Work to sensible batch sizes so nothing is mixed faster than it can be used and overcoated, avoid application in direct sun or drying wind, and cure the finished repair as the mortar system requires. Always confirm the current MC-Bauchemie product data sheet and repair-system build-up for the specific mortar being used, and let Space Arc’s technical team review the substrate and sequence for the actual structure.
Specifications
| Product type | Two-component polymer-modified cementitious bonding slurry (bonding bridge) |
| Components | Cementitious powder + SBR/acrylic polymer dispersion, gauged on site |
| Colour / form | Grey cementitious slurry after mixing |
| Application method | Stiff-brush / scrub coat, worked into the substrate |
| Substrate condition | Sound, clean, saturated-surface-dry concrete |
| Overcoating | Repair mortar placed wet-on-wet before the slurry skins over |
| System framework | Used within EN 1504 concrete-repair build-ups; adhesion assessed to EN 1542 |
| Application temperature | Above-freezing; protect from rapid drying, sun and wind during cure |
Industry use cases
Building repair & rehabilitation
Reinstating spalled cover concrete on slabs, beams and columns so patch mortars key into the structure and stop sounding hollow within a season.
Bridges & infrastructure
Soffit, pier and deck repairs where mortar debonding on overhead and vertical faces is the main durability risk and a reliable bonding coat is non-negotiable.
Precast concrete
Making good chipped edges, blowholes and form defects on precast units before a levelling or reprofiling mortar, so the repair does not shear off in handling.
Water-retaining & effluent structures
Bonding lined repairs in RCC tanks, sumps and STP/ETP structures as part of a full repair-and-protection system.
Industrial flooring & screeds
Priming and bonding new cementitious toppings and screeds to an existing concrete base to prevent hollow, drummy or lifting floors.
Frequently asked questions
What exactly is MC-Contact and what does it do?
Can I skip the bonding coat and just trowel mortar onto the concrete?
How soon do I have to place the mortar after brushing on the slurry?
How do I prepare the concrete surface first?
Is it compatible with any repair mortar?
Does MC-Contact make the repair waterproof?
How we position MC-Bauchemie MC-Contact
MC-Contact sits at the bonding-coat step of a concrete-repair system, so it is naturally specified alongside the MC-Bauchemie repair mortars, levelling and reprofiling compounds it is designed to key in — treat it as one part of a build-up, not a standalone fix. Where a project is already standardised on another brand, the direct counterparts are Sika’s cementitious bonding primers within the Sika MonoTop repair range and the bonding-slurry / bonding-bridge products in Dr. Fixit’s and STP’s repair systems; the right choice usually follows whichever repair-mortar family the specification already calls up. If the interface needs the higher structural bond of an epoxy rather than a polymer-cement slurry — for example bonding new structural concrete to old at a construction joint — that is a different tool, and we would point you to an epoxy bonding agent instead. Space Arc carries these across Fosroc, Sika, Dr. Fixit and STP so the bonding coat and the repair mortar can be matched as a compatible pair.
Fosroc Nitobond SBR — A specifier on a Fosroc-standardised job would choose Nitobond SBR as the equivalent SBR-polymer bonding aid and mortar gauging liquid, since it delivers the same old-to-new bond and pairs with the Renderoc repair range.
Related Concrete Repair products
Source MC-Bauchemie MC-Contact for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.