MC-Bauchemie MC-Crete 620
A monomolecular-film evaporation retarder from MC-Bauchemie that shields freshly placed concrete against rapid surface drying, buying finishers the working window that hot, windy Indian sites so often steal.
What is it?
A ready-to-use liquid evaporation retarder that lays down a thin, temporary monomolecular film over fresh concrete to slow surface water loss during the plastic stage.
Where is it used?
Large floor slabs, bridge decks, pavements, rooftops and any flatwork poured in hot, dry or windy conditions across Delhi NCR and Pan-India.
Why use it?
It reduces surface evaporation by roughly 50 to 70 percent, holding off plastic shrinkage cracking and crazing without touching strength, bond or permeability.
How is it applied?
Misted on with a hand-pump or power sprayer at 0.05 to 0.1 litres per square metre immediately after strike-off, and reapplied if the film dries before floating and trowelling are finished.
About MC-Bauchemie MC-Crete 620
MC-Crete 620 tackles a problem every site engineer in an Indian summer knows too well: concrete that looks fine at strike-off but starts crazing and cracking within the hour. The culprit is not the mix, it is the weather. When ambient temperature, low humidity and wind combine, water leaves the concrete surface faster than bleed water can rise to replace it. The surface skin dries, shrinks and tears while the slab below is still plastic and has almost no tensile capacity to resist it. MC-Crete 620 is an MC-Bauchemie evaporation retarder engineered specifically for this narrow but critical window, from screeding through to the last trowel pass.
It is not a curing compound and should not be confused with one. Sprayed as a fine mist, MC-Crete 620 forms an extremely thin monomolecular film across the fresh surface. That film acts as a physical barrier that slows the escape of moisture, cutting evaporation by around 50 to 70 percent at the recommended rate. Because the film is temporary and worked into the surface during finishing, it leaves no residue that would compromise the bond of toppings, hardeners or curing membranes applied afterwards. The result is a longer, more forgiving finishing window and a denser, crack-resistant surface, with no measured effect on the concrete’s compressive strength or permeability.
The technical insight
The mechanism is straightforward physics rather than chemistry. Plastic shrinkage cracking is driven by the rate at which surface moisture evaporates, and ACI guidance flags trouble once that rate climbs past roughly 1.0 kg per square metre per hour. On a hot, breezy day that threshold is crossed easily. MC-Crete 620 works by depositing a monomolecular film, a layer effectively one molecule thick, that sits on the water at the concrete surface and interrupts the free exchange of moisture into the air. Cutting evaporation by 50 to 70 percent keeps the surface moist enough that the drying stress never builds to the point where the tender plastic concrete tears. Crucially, the film dries in only one to two minutes and is consumed during floating and trowelling, so it neither seals the surface prematurely nor blocks the curing that must follow. It buys time during the plastic phase; it does not replace proper curing once the concrete has set.
Where it is used
- Large industrial and warehouse floor slabs poured in hot-weather conditions
- Bridge deck concrete exposed to wind and direct sun
- Highway, road and airport pavement construction
- Rooftop and terrace slab casting during peak summer
- Sports courts, plazas and other exposed architectural flatwork
- Power-floated slabs where a long, controlled finishing window is essential
- Emergency use on ready-mix pours delayed in transit or during placement
- Any flatwork where the calculated evaporation rate approaches or exceeds 1.0 kg/m2/hr
Key advantages
- Cuts surface evaporation by roughly 50 to 70 percent at the recommended rate
- Directly reduces the risk of plastic shrinkage cracking and surface crazing
- Extends the finishing window so floating and trowelling can be done properly
- No adverse effect on compressive strength, bond or concrete permeability
- Leaves no residue that would interfere with toppings, hardeners or curing membranes
- Fast film formation, drying in just one to two minutes after misting
- Simple to apply with standard hand-pump or power spray equipment
- Compatible with MC-Bauchemie curing compounds and downstream surface treatments
Limitations & considerations
- It is an evaporation retarder for the plastic phase, not a curing compound; the slab still needs full curing after finishing
- Effectiveness depends on correct, uniform misting; over-application or working it into the surface as a finishing aid can weaken the top skin
- The film is temporary and needs reapplication if the surface dries before finishing is complete
- It reduces but does not eliminate evaporation, so severe hot-weather concreting still needs shading, wind breaks or fog spraying alongside
- Benefit is limited to exposed flatwork; it offers little for formed vertical or enclosed elements
Selection & best practice
Apply MC-Crete 620 as a light, uniform mist immediately after strike-off and screeding, before bull-floating and trowelling, using a clean hand-pump garden sprayer for smaller pours or a power sprayer on large decks. Target 0.05 to 0.1 litres per square metre and keep the coat even; the goal is a fine film, not a puddle. Never trowel the retarder into the concrete to lubricate the surface, as that traps excess water at the top and weakens the skin. If the film dries and finishing is still in progress, simply reapply. Treat it strictly as a plastic-stage aid and follow up with a proper curing regime, curing compound, wet hessian or water ponding, once finishing is complete. In extreme conditions, pair it with shading and wind protection rather than relying on the retarder alone.
Specifications
| Product type | Liquid evaporation retarder (monomolecular film former) |
| Brand | MC-Bauchemie |
| Function | Reduces surface water evaporation from fresh concrete during the plastic phase |
| Evaporation reduction | Approximately 50 to 70 percent at the recommended rate |
| Application rate | 0.05 to 0.1 litres per square metre as a fine mist |
| Application method | Hand-pump garden sprayer or power sprayer |
| Film drying time | 1 to 2 minutes |
| Effect on concrete | No effect on compressive strength, bond or permeability |
| Pack sizes | 25-litre cans and 200-litre drums |
Industry use cases
Industrial Flooring
On large warehouse and factory slabs poured in summer, it holds the surface moist long enough for power-floating crews to achieve a flat, crack-free finish before the concrete goes off.
Infrastructure & Bridges
Bridge decks and elevated slabs sit fully exposed to sun and wind; a mist of MC-Crete 620 after screeding keeps the deck surface from crazing during the vulnerable first hours.
Roads & Pavements
Highway and airport pavement pours cover huge areas with long finishing sequences, where controlling evaporation across the whole slab prevents plastic shrinkage map-cracking.
Commercial & Rooftop Construction
Terrace and rooftop slabs cast during peak summer benefit from the retarder buying finishers time, cutting the surface cracking that later becomes a leakage path.
Ready-Mix & Emergency Pours
When a ready-mix pour is delayed in transit or placement stretches out, it protects the exposed concrete surface until the finishing team can catch up.
Frequently asked questions
Is MC-Crete 620 a curing compound?
How much do I need per square metre?
Will it reduce the strength of my slab?
When exactly should I spray it?
Can I use it with a curing compound afterwards?
Do you supply MC-Crete 620 outside Delhi NCR?
How we position MC-Bauchemie MC-Crete 620
MC-Crete 620 sits at the very start of the concrete finishing sequence and is best specified alongside, not instead of, a curing product. Once finishing is complete, pair it with a proper curing regime; MC-Bauchemie’s own curing compounds are the natural companions, and MC-Crete 620 is fully compatible with them. It should not be confused with curing membranes such as Fosroc Concure, which are applied after finishing and serve a different purpose. Because a dedicated monomolecular evaporation retarder of this type has no direct Fosroc counterpart, engineers who prefer a single-brand Fosroc chain would use Concure for the curing stage rather than an equivalent anti-evaporant. For teams working across our other brands, comparable hot-weather protection can be found in the anti-evaporant and curing lines from Sika and Dr. Fixit, which our team can cross-reference on request to match project specifications and site conditions.
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