Stamped Concrete is a skilled trade. It requires a whole different set of knowledge and skills aside from normal placing and finishing of concrete. In the construction industry, concrete is one of the few perishable materials. Once you add the water, there is a small window in which to place and finish concrete. This window ranges from several minutes to several hours. But when it hardens, there's no reversing it and any mistakes made during the process are usually costly to fix.

Having the knowledge and "know how" to place and pour regular concrete is a crucial prerequisite for doing quality stamp work on a large scale. It is possible to get by without it on a small slab. The smaller the amount of concrete pour means the quicker you can place it, which allows more time work with it and finish it.

Knowing how to stamp concrete is a "learn as you go" process. The key to a successful job is planning and preparation. Try a small slab first. If you're doing a patio, break it down into smaller sections and do it one piece at a time. Have plenty of help. Find the quickest way to get the concrete where in needs to go, whether it's pouring right from the truck, using a buggy, or wheelbarrow, etc. The faster you get the concrete down, the easier it will be to make a nice finish.

GETTING STARTED Make sure the sub grade is prepared right. The sub grade should be compact and well drained. For better drainage use B gravel as your sub grade and be sure to compact it with a tamper. Also wet the gravel before you pour the concrete so it doesn't suck the water out of the concrete.

CONCRETE MIX Make sure that your slab will have at least 4" and be uniform. You don't want it to be 3" in some spots and 5" in others. You will want a slump of 4 or 5 when pouring. You don't want it too wet because it will reduce the strength, but you don't want it too dry or it will be too hard to work with.

COLORING After the concrete has been placed and bull floated once, color hardener is applied after excess bleed water has evaporated. One unit of color hardener will cover approximately 100 square feet. It is applied using the dry shake method and bull floated once again. Allow color hardener to wet out/wet up prior to bull floating. When floating, make sure you have a nice smooth finish before you start to stamp. If  you leave lines from the the float it will show when you are done stamping. Also make sure you edge the concrete well you don't want a beautiful job with bad edges.

DRY SHAKE METHOD

RELEASE AGENT After the color hardener has been applied and slick (fresno) finished, antique powder release agent is applied prior to stamping using the dry shake method. The release agent will keep the stamp tools from pulling up concrete and impart another color shade to the work. Seamless texture skins are used to texture to the edge of the form boards to ensure complete texturing to the perimeter of the slab.

STAMPING Begin the stamping process as soon as the sheen has left the top of the concrete. You may not have to press as hard on the stamps but you don't want to wait too long. Just make sure the concrete isn't coming up between the stamps. And never stand on a stamp that does not have a stamp next to it.

Texturing continues down the edge of the form boards as a crew begins to run the patterned concrete stamps. The first mat laid is critical to the layout of the job as all other mats will be placed square to the first mat.

An impact tamper (impact tool) is used to firmly imprint the texture and pattern of the stamp into the plastic concrete. Keeping the stamps fitted tightly together is important to create neat grout lines.

Saw cut expansion joints as soon as you can to prevent cracks from forming (usually cut the next day). Instead of saw cutting joints, you can groove joints into the placed concrete during the edging process and open them back up after the stamping process with a cutting bar or touch up chisels.

REMOVING RELEASE AGENT Leave the powdered release agent on the stamped concrete for 1-2 days before removing it by broom. This will help the concrete cure without being affected too much by the sun. After all you want it to cure slowly.

The concrete is allowed to set after stamping for 3-5 days, depending on climate, before the excess release agent is pressure washed (2000-3000 PSI is recommended) from the surface.

SEALING After the slab is allowed to cure completely, two thin coats of solvent-based sealer can be applied to the surface using a 3/8” nap roller. The sealer protects the slab from staining and enriches the final color by amplifying the colors in the hardener and release agent.

ADDITIONAL TIPS

• Always watch for the weather. Delay the project if rain is possible.
   

• Have enough stamping mats to cover 1½ times the width of the slab.
   

• Use a minimum of five sacks of cement per cubic yard, Coarse aggregate should not exceed 3/8", Aggregate must be non-reactive, Minimum practicable amount of water should be used, Slump should not exceed 4", and No high-range water reducing admixtures.
   

• Integral Colors are available in 25 lb. disintegrating bags. Generally, 1-2 lbs. of pigment  per 96 lbs. of cement produces subtle colors, while 2-4 lbs. of yields more medium shades. 5 or more lbs. of pigment  per 96 lbs. of cement yields the most intense shades of color. If using pigment , float and finish following normal finishing procedures. When using color hardener, finish concrete following normal procedures, using a tamper, screed and wood or magnesium float. The surface of the concrete must remain open. Do not steel trowel until after the final application of color hardener.
   

• Overall coverage requirements vary according to the color selected and the desired intensity. Generally, 60 lbs. per 100 square feet is sufficient, although lighter or pastel colors may require as much as 100 lbs. per 100 square feet. Two-thirds of the hardener should be applied at first and one-third should be withheld for the second application and final touch up.
   

• There should be no standing water on the concrete surface when applying any hardener. Do not over float or trowel. This will draw water to the surface and reduce color intensity. Do not sprinkle or fog water on the concrete. This will cause variations in color intensity. Do not cover with plastic. Color Hardener settles during shipment. Before beginning, fluff the contents of the pail with your hand to break up clumps and provide a consistent airy feel throughout the pail.
   

• Release agent settles during shipment. Before beginning, fluff the contents of the pail with your hand to break up clumps and provide a consistent airy feel throughout the pail.