Related topic>>Overview of Curing Concrete
If a decorative concrete finish is in your future, than it is important to take action early on in the planning stages even before the concrete slab has been poured.
The first thing to figure out is what type of decorative concrete finish you will be using? Is it an acid stained finish, decorative concrete overlay system, epoxy coating, acrylic, dye, stain color or polished concrete? While certain types of concrete coloration systems (mainly acid stains) require a chemical reaction to properly deposit color, other systems like acrylic dyes and stains must be able to absorb into the surface to leave their color. Epoxy colors and coating simply need to "attach" themselves to the surface by absorption or an actual physical bond or grip. It is important to understand your system as the curing and preparation of the concrete will be a major factor in the success of the project.
In most cases, a decorative concrete surface coloration treatment of any kind needs to absorb into or attach itself to the concrete's surface. Many spray curing agents can leave a residue or completely seal off the surface of the concrete slab. It is important to use a spray curing agent that will eventually dissolve or perhaps use more conventional methods including burlap or Curing Paper to maintain the moisture and cure the concrete. For Decorative concrete resurfacing systems it's not as important as the surface should be abraded, shot blasted or ground prior to a topping installation therefore a spray cure will eventually be removed and probably work fine.
When acid staining, dying, or adding any type of translucent surface color treatment, the substrates color and pattern will play a big part of the end result. It is therefore necessary to finish and cure the concrete in a way that will leave it natural and mottled and ready for color application.
When concrete cures it will have a tendency to dry in different colors depending on the rate of its cure. This is evident in concrete that has been cured at an uneven rate due to improper or incomplete coverage or with the use of plastic sheets as a curing method. Plastic sheets when used for curing a concrete slab to be decorated with translucent stains can leave undesirable marking and patterns where the plastic was touching the surface vs where it wasn't and where the concrete was left exposed. The end result is a highly irregular pattern and mottled surface that will not stain properly. (See figure 1.)
If it is too late and a concrete surface has been cured and is irregular and marred, even a surface grinding won't always remove the blemishes, although an on-site test area will better determine the results. In this case a resurfacing system may be used to create a fresh new canvass that can then be decorated.
So then what is the best way to cure concrete for a successful decorative concrete application?
1. Burlap is an absorbent cover for curing concrete, which allows periodic lapses in the sprinkling method of curing. Burlap should be rinsed thoroughly before placing. Care should be taken to ensure proper lapping and that all concrete edges are covered. Keep continuously wet.
2. Using just water and surface misting works great and will leave no markings.
3. Curing paper provides a residue-free curing process, allowing a paintable or stainable surface once finished. Curing Paper combines two layers of high quality Kraft paper with tri-directional reinforcing fibers completely embedded in high grade asphalt to provide superior strength. It is wet strength treated to resist scuffing, dry rot, mildew, and shrinkage. Protects against sun and frost damage. Once the concrete has set sufficiently to permit application without marring the surface, Curing Paper should be unrolled upon the entire surface, laps of no less than 4" should be sealed with Moistop Tape.
4. After an initial uncovered cure with water mist the concrete is left to dry until it has no apparent water on its surface, then two layers of kraft paper are applied in perpendicular directions completely covering the surface. OSB (oriented strand board) is then used to completely cover the concrete slab. This not only slows the water evaporation it also protects the concrete from stains, glues, paints, spills and scratched during construction leaving a beautiful palette for the professional decorative concrete contractor to apply their finishes.
Related topic>>Overview of Curing Concrete
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