MC-Bauchemie Primex 250
A water-based acrylic primer that seals concrete pores and gives acrylic waterproofing coatings something solid to grip.
What is it?
A ready-to-use, water-based acrylic copolymer dispersion primer that consolidates porous mineral substrates before acrylic-based protective or waterproofing topcoats go on.
Where is it used?
RCC terraces, sloped and podium roofs, parapet walls, and repaired concrete or masonry across Delhi NCR and pan-India sites that are about to receive an acrylic waterproofing or protective system.
Why use it?
Bare or freshly repaired concrete is full of surface pores and trapped air; coating straight over it invites pinholing and blistering. Primex 250 solidifies the surface and closes those pores, giving the topcoat a uniform base to bond to.
How is it applied?
Stir well, then apply one continuous coat by roller, brush or airless spray at around 75 gm per square metre. It’s touch-dry in about 30 minutes and can typically be overcoated within an hour on absorbent concrete, up to 4 hours on non-absorbent surfaces, within a 5-30°C, 85% RH window.
About MC-Bauchemie Primex 250
Primex 250 is MC-Bauchemie’s dedicated primer for its acrylic coating range — not a waterproofing membrane in its own right, but the layer that decides whether the membrane above it stays put. Delhi NCR terraces and podium decks often fail not because the acrylic topcoat was poor, but because it was rolled onto chalky, porous concrete that outgassed air through the wet film. Primex 250 is built to stop exactly that: a water-based acrylic copolymer dispersion that soaks into the substrate, solidifies loose surface material, and dries to a transparent, vapour-open film.
On site that means a straightforward one-coat, ready-to-use product with no batching or pot life to race against. It’s specified as the first layer in an acrylic system: prime with Primex 250, treat cracks or honeycombing with a compound such as MC-Bauchemie’s own Nafuquick, then follow with the acrylic waterproofing or protective coat once the primer has cured. It’s a low-drama, technically documented product with ASTM-tested adhesion data behind it, useful when a client or consultant wants proof rather than a claim.
The technical insight
The TDS backs its claims with real test numbers: 0.61 N/mm2 pull-off adhesion per ASTM D 7234, a 30-minute surface-dry time per ASTM D 1640, and 9.77% non-volatile content per ASTM D 1644. That dry time means crews can often prime and topcoat within the same shift on absorbent concrete, while the manufacturer’s dew-point margin — 3K above dew point with RH capped at 85% — is a hard constraint through Delhi’s humid monsoon and foggy winter mornings, when most coating failures actually trace back to priming in the wrong window rather than a bad topcoat.
Where it is used
- Priming RCC terraces and sloped roofs before an acrylic waterproofing topcoat
- Podium deck and basement-roof priming ahead of acrylic waterproof membranes
- Sealing parapet walls and masonry before decorative-cum-protective acrylic coatings
- Consolidating freshly repaired concrete (after Nafuquick-type patch repair) before recoating
- Priming stripped surfaces during re-waterproofing after an old membrane is removed
- Base priming on chalky, dusty or friable concrete that would otherwise starve the topcoat of adhesion
- Surface sealing on neutral and alkaline mineral substrates ahead of any MC-Bauchemie acrylic system
- Pre-treatment on exposed RCC facades before UV- and weather-resistant acrylic finishes
Key advantages
- Economical single-coat consumption at roughly 75 gm/m2
- Fast 30-minute surface-dry time lets many jobs move to topcoat the same day
- Documented 0.61 N/mm2 pull-off adhesion (ASTM D 7234) gives specifiers a verifiable number, not a claim
- Water-based formulation keeps VOC exposure low on occupied residential terraces
- Vapour-open film lets residual substrate moisture escape instead of blistering the topcoat
- Resistant to UV, weathering and alkali even before the topcoat goes on
- Ready-to-use, single-component — no mixing ratios to get wrong on site
- Works on both alkaline and neutral mineral substrates, covering most Indian concrete and masonry
Limitations & considerations
- It’s a primer, not a waterproofing system, and must always be followed by an acrylic topcoat
- Application is temperature- and humidity-gated, so Delhi’s monsoon and winter fog windows need planning around
- Chemistry-specific to acrylic topcoats — it isn’t the right primer ahead of epoxy, PU or bituminous systems
- The quoted 75 gm/m2 consumption assumes a reasonably sound substrate; rough or heavily patched concrete drinks more
- Dries transparent, so applicators get no visual cue for missed patches
- 12-month shelf life from manufacture, so batch age is worth checking on slow-moving stock
Selection & best practice
Mechanically clean off laitance, dust and unsound material, and strip any existing waterproofing coating to bare, sound concrete. Treat cracks and honeycombing with a compound such as Nafuquick, clear algae or vegetation with a suitable herbicide, then finish with a high-pressure water-jet clean. Let the surface dry, stir Primex 250 thoroughly, and apply one continuous, streak-free coat, never in rain, high humidity or frost. Keep temperature between 5-30°C, relative humidity under 85%, and at least 3K above dew point, and protect the fresh film from dew, rain and frost until cured.
Specifications
| Chemistry / System | Water-based acrylic copolymer dispersion primer |
| Specific Gravity | 1.00 gm/cc |
| Consumption | 75 gm/m2/coat |
| Surface Dry Time | 30 minutes (ASTM D 1640 @ 30°C) |
| Non-Volatile Content | 9.77% (ASTM D 1644) |
| Pull-off Adhesion Strength | 0.61 N/mm2 (ASTM D 7234) |
| Rain-proof Time | 4-6 hours |
| Overcoating Time | Approx. 1 hr (absorbent substrates); approx. 4 hr (non-absorbent substrates) |
| Pack Sizes | 5 kg, 20 kg, 30 kg |
Industry use cases
Residential terrace waterproofing, Delhi NCR
Priming an exposed RCC terrace on a South Delhi apartment block before an acrylic waterproof topcoat, after patch-repairing hairline cracks.
Podium deck, Gurugram residential complex
Sealing a podium-level basement roof slab ahead of an acrylic waterproofing membrane, where vapour-open behaviour matters over occupied parking below.
Facade and parapet refurbishment
Priming plastered parapet walls and facade bands before a UV- and weather-resistant acrylic coating on a commercial building.
Re-waterproofing after membrane failure
Consolidating bare concrete on a terrace where an old, failed waterproofing coat has been fully stripped, ahead of a fresh acrylic system.
Frequently asked questions
Is Primex 250 a waterproofing coating on its own?
Can Primex 250 be used under epoxy or PU flooring systems?
How soon can the acrylic topcoat go on after priming?
Does it work over old painted or previously coated surfaces?
How much Primex 250 do I need for a given area?
Can it be applied during Delhi’s humid monsoon season?
How we position MC-Bauchemie Primex 250
Primex 250 slots in as the first layer of MC-Bauchemie’s acrylic coating systems, typically specified alongside Nafuquick for crack and honeycomb repair before priming. It isn’t interchangeable with primers built for other chemistries: Fosroc, for instance, pairs its Dekguard protective coatings with a solvent-borne silane-siloxane primer rather than a water-based acrylic one, so specifiers should match primer chemistry to the topcoat system rather than substitute on price alone.
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