A monomolecular film sprayed right after screeding or floating that cuts surface evaporation on hot, windy or dry days, helping prevent plastic shrinkage cracks and a crusted top. Crews reach for it when the evaporation rate approaches 0.2 lb per sq ft per hour, and sooner on silica fume and SCM-rich mixes that barely bleed. It is neither a curing compound nor a finishing aid, and troweling it in like extra water weakens the surface.
Wind's picking up, hit the whole deck with evaporation retarder before you start floating.
Also heard as
- evap retarder
- monomolecular film
Do not mix it up with
- Curing compound: Curing compound goes on once finishing is done and stays for days; evaporation retarder is a temporary aid during finishing.
Related terms
Plastic shrinkage cracking
Cracks that open in fresh concrete before it sets, when the surface dries faster than bleed water replaces it.
Silica fume
Ultrafine silica dust from silicon smelting that makes concrete much denser, stronger and less permeable.
Curing compound
A sprayed liquid membrane that seals moisture into newly finished concrete.
Bleed water
Water that rises to the surface of fresh concrete as the heavier solids settle.