Summer is here! That means a lot of hot, windy days ahead, which is bad news for concrete contractors. Concrete tends to crust and crack on hot, dry days because the water evaporates too quickly, leaving behind a dry, unworkable mix. If a contractor starts to finish concrete after the water has evaporated, it wears down his equipment and causes cracks and discoloration on the surface of the concrete.  The good news, however, is that there are solutions to this problem that allow concrete finishers to still create beautiful smooth concrete on even the hottest, driest days.

Finishing Aids and Surface Retarders

The two most common products used to combat the evaporation of surface water in concrete are finishing aids and surface retarders.  Surface retarders create a thin, hydrophobic layer on top of the concrete that holds the water in place.  This keeps the concrete moist until the layer evaporates after about 30 minutes or so.  Finishing aids cause a chemical reaction in the mix that suspends the water molecules in the concrete and prevents them from being evaporated by the heat.

How To Use the Products

While surface retarders and finish aids both keep the water in the concrete, they are not designed to be used in the same manner.  In fact, using a surface retarder the way you would a finishing aid will result in weakened and cracked concrete.  To properly use a surface retarder, first, mix it with water according to the dosage instructions on the product packaging, and then evenly apply a single coating to the concrete using a sprayer.  This will create a shiny film on the top of the concrete.  Now you can finish placing the rest of the concrete while you wait for the film to evaporate.  It is very important that you wait until the surface retarder has evaporated to start finishing the concrete.  Surface retarders were not formulated to be worked into the concrete mix and doing so can alter the water/cement ratio of the mix and damage the concrete.

Finishing aids, however, are formulated to be worked into the concrete.  The application process for a finishing aid is similar to that of a surface retarder.  Measure the right dosage of chemicals and water into a sprayer and apply a thin layer to the top of the concrete.  But once the finishing aid has been applied, you can immediately start troweling the concrete mix.  Finishing aids can be applied at any point during the finishing process, and can even be applied multiple times if needed to get the perfect finish.

Which One Should You Choose

While surface retardants are effective at preventing evaporation, they are not ideal to use on rush jobs. If you have a fast-paced project, a finishing aid – such as Control Finish– is going to be much more helpful. Surface Retardants can be very helpful on bigger jobs that require multiple pours.  For more information about keeping your concrete moist during the hot summer days, check out our product information pages or follow our social media pages.  Don’t forget, you can order your case of Control Finish through the website.