Concrete requires a specific amount of water to form the microscopic crystals that are responsible for the strength of the material. Curing concrete requires the water content in the mixture to stay constant until it is finished. Contractors use a variety of methods to retain moisture while the concrete cures, and each has its own set of benefits and problems.
Water blankets are burlap or canvas sheets that are laid on top of fresh concrete where the surface has set. These trap moisture being released from the concrete as it cures, and can protect concrete from weather during the setting process, according to Concrete Network.
Contractors often spread the water blankets across a newly poured walkway or driveway, but the strategy is generally too time-consuming and difficult to spread on a large slab such as a house foundation. Wrinkles or air bubbles will cause the water to puddle, leading to stains in the concrete, so the blankets must be completely smooth before wetting.
Heating or Cooling Techniques
Curing concrete properly requires the right temperature range. When concrete is poured at temperatures near or below freezing, the curing process slows or stops because the moisture can't interact with the cement properly. The opposite happens in warm weather, according to ReadyMix, and evaporation is greatly sped up.
Water blankets and shade screens can be used to keep concrete cool. Some industrial heating pads are useful for keeping curing concrete warm in the winter, but they can be difficult to manage and may cause cracks or weakness by overheating the concrete if not monitored.
Applying fresh water to the top of curing concrete keeps its moisture levels constant, but it can be tricky to keep the water levels consistent without flooding the area. Sprinkler systems are commonly used to distribute a small amount of water over a concrete slab or driveway, according to the Portland Cement Association. These systems are easily controlled by a timer, preventing water waste or stains. Soaker hoses that leak small amounts of liquid over a period of many hours also work, but they can only be placed on top of concrete that has partially set or will leave indentations in the surface.
Spray or Roll-On Coatings
Curing compounds are liquids a homeowner or contractor can spray across the surface of wet concrete. The waxy or rubber-based compounds create a thin but impermeable layer that gradually wears off, according to Builder Bill's DIY Help website. Resin and PVC-based liquids last longer to protect concrete that requires an extended curing time. These materials do little to prevent curing problems from high or low temperatures, and if used on indoor floors, they may interfere with adhesives used to attach tile or vinyl flooring.