Question:

We cannot seem to overcome surface crusting on our fresh concrete slabs. Our sites are almost always exposed to sun and wind. What can we do, it has become a real problem?

Answer:

Please examine ACI 305, suggested methods for hot weather concreting. You will read things telling you to avoid the hottest time of the day, cooling the concrete and besides that advice, you will read about using a monomolecular film liquid. It is the single thing your crew can do to minimize crusting and the follow on problems with durability and surface plastic shrinkage cracks.

You will need a supply of clean water. I am guessing 200 gallons of clean water would be enough for 40,000 square feet of area to be treated once with monomolecular film liquid. The good news is monomolecular film liquid is a concentrate. The dilution ratio I am familiar with is 9 parts of water and 1 part of monomolecular film liquid. This simple dilution formula would provide your crew 50 gallons of monomolecular film liquid out of 5 gallons of concentrate.

Spray the diluted monomolecular film liquid upon the very fresh concrete. The best experience I ever had using monomolecular film liquid was when my crew applied it right after the concrete was screeded. Finishing activities do not interfere with the function of monomolecular film liquids. A finishing tool or finishing machine can pass over the treated surface and not harm the monomolecular film liquid.

Monomolecular film liquids function by having molecules that are "water loving" and molecules that are "water hating." The stem of the water loving molecule attaches to the moist concrete surface and the water hating molecule repels its self from the same moist surface. This behavior creates a protective evaporation barrier for the fresh concrete surface.

L&M's monomolecular film liquid is called E-CON and it is the most dependable monomolecular film liquid I have ever used. Include E-CON in your concrete working regimen and you will overcome crusting and other problems associated with rapid surface drying of fresh concrete.