A Guide to Pattern Imprint Concrete for your Driveway

Step By Step Guide To: How To Sucessfully Imprint Concrete

There are several of steps involved in imprinting concrete, and only a small time frame within which to get them done. This is not like when applying a decorative coating or stain to concrete paving, those who perform the work need to complete the entire pattern imprinted method before the fresh concrete sets. To do the job well, contractors must be experienced, organized, and very prepared. For large projects in particular, that means diagraming the imprinting layout in advance, having the imprinting tools lined up and ready to go, and making sure enough labor is available for the job at hand.

Adding Colour Hardener

After the concrete reaches the right stage of plasticity (generally when no bleedwater is on the surface), broadcast the color hardener by throwing it onto the surface from waist level or a bit lower to minimize the amount of material that drifts into the air. Work from the middle of the concreted area and back toward the edge forms to avoid a heavy buildup of color hardener on the edges. After the first shake of color hardener has been applied to the surface, give it five to 10 minutes to absorb water from the concrete and then float it into the surface. Right after bull floating the first application of color hardener, follow the same steps and apply a second layer of hardener to ensure complete coverage.

Adding The Release Agent

Powdered or liquid release agents serve two important purposes: They impart subtle color contrast while acting as a bond breaker to prevent the imprinting mats or skins from sticking to the concrete and disturbing the imprint texture. The best way to apply a powdered release is with a dry tampico brush about 8 inches wide. Dip the brush into the pail of release and fluff it to load the bristles and coat them evenly. Then take the brush by the handle, holding it below belt level, and use your wrist to flick the release onto the surface in a light, uniform layer.

To apply a liquid release agent, use a pump-type sprayer to apply the release in a uniform layer onto the surface of the concrete right before you stamp. If you plan to use a tinted liquid release agent, add the tint a day or two beforehand if possible. This will allow the pigment particles to fully dissolve.

Checking If The Concrete Is Ready?

Before you start imprinting, check to see that the concrete has reached the right stage of plasticity. If you start imprinting too soon, the concrete won’t be firm enough to support the weight of workers or hold a well-defined imprint. If you start imprinting too late, not only will imprinting require more work, you’ll produce little or no texture with the imprint stamps, especially as you reach the end of the job. Press your fingers into the concrete surface at several locations on the concreted area. If you leave a clean imprint about 3/16 to 1/4 inch deep, you can generally start imprinting. Another test is to place a stamp on the concrete and step on it. The stamp should hold your weight and not slide around or sink too deeply into the surface.

Before imprinting, pretexture along the perimeter of the concreted area with a texturing skin or flex mat.

Pretexture The Concreted Area Perimeter

Pretexture along the perimeter edges of the concreted area about 6 to 12 inches inward with a texturing skin or flex mat. This step is important because when you’re working with a nonflexible stamp, the tool will overlap the edge of the form and you won’t be able to fully depress it into the concrete surface. By pretexturing the perimeter first, you’ll get the texture you need and the full color from the release.

The First Row Of Imprint Stamps

Once the edges are pretextured, the crew can start imprinting the rest of the concreted area with the mat tools. Generally, you should stamp in the same sequence that you placed and finished the concrete. For example, if you started placing the concrete in the top left-hand corner of the concreted area and ended on the bottom right corner, this would be the preferred sequence to use for finishing and imprinting operations, working row by row from the starting point to the end point. Most stamp sets are labeled with letters or numbers. Always arrange the imprint stamps in the sequence recommended by the manufacturer, such as ‘A’, ‘B’, ‘C’ or ‘1’, ‘2’, ‘3’.

It’s important to place the first row of imprint stamps on a straight line because that will serve as the benchmark for the rest of the job. If it’s not perfectly straight, the rest of the rows will be out of alignment as well. Use a string line as a guide, especially for aligning stamp patterns that are square or rectangular. For notched or irregular stamp patterns, you can check alignment by using the edge form as a reference point (assuming that it’s square). Use a string line or tape measure and run it from the edge of the form to the top and bottom edges of the stamp mat to make sure the tool is running square relative to the form.

The Imprinting Sequence

If the concrete is at the ideal stage for imprinting, you should be able to impress the imprint stamps into the surface by simply walking on the tools, possibly followed by a light tamping. The imprinting crew should complete the first row before moving on to the second one. Typically, one person will place the starter tools and stand on them while grabbing imprint stamps from the first row and leapfrogging them into the next row. While this person is moving and advancing the tools, another person can do the tamping. Depending on the stamp pattern, a third person may be needed to detail the grout joints.

Required Detailing Work

Even if you have pretextured the edges and used a flex mat against walls, you will often find it necessary to do some detailing with a hand chisel, roller, or texture skin to remove displaced cement paste that comes up through the joints between imprint stamps, to fix any blurred pattern lines, and to correct grout joints where the stamp wasn’t tamped down with sufficient pressure. With most stamp patterns, you’ll achieve better results if you detail the same day, either as the imprint stamps are being advanced or before going home at the end of the day. For touching up or fixing minor surface flaws, you can use a texture skin as an eraser to correct unevenness or nonuniformity by patting it into the area until it’s level and then reimprinting with the appropriate mat tool.

Removal Of Excess Release Agent And Addition Of Curing Compound

If you’ve applied a colored release powder to the concrete surface, you can’t apply a curing compound until you wash off the residual release agent-a minimum of one day and in some cases two or three days later, depending on weather conditions. Once the surface is sufficiently cleaned and allowed to dry, you can then spray on a liquid membrane-forming curing compound or a cure and seal to retain moisture in the concrete. If you’re using a clear or tinted liquid release, you can usually apply the curing membrane to the concreted area the same day. Check the release manufacturer’s recommendations for curing.

Adding Joints

Cutting contraction joints (also called control joints) at the proper depth and spacing in the concreted area soon after placement provides stress relief at planned locations and prevents uncontrolled random cracking. You can form joints in the concrete as it starts to set using a groover or you can wait to cut the joint until after the concrete has set using a saw equipped with a diamond or abrasive blade. Generally, a sawed joint is less noticeable than grooving.

Adding Sealant

Once the concreted area has cured sufficiently, you should apply a finish coat of sealant. Most manufacturers recommend applying the sealant several weeks later, after a light surface cleaning. Be careful not to apply the sealant too heavily, which could trap moisture in the concreted area. One of the most efficient techniques for applying sealant is to combine both spraying and rolling, especially when the stamped pattern has deep grout lines. Going back over the surface with a roller where necessary helps to distribute the sealant uniformly.

Pattern Imprinted Paving Tips

Here are some useful tips:

  • If you’re using a new stamp pattern for the first time, practice with the tools on compacted sand before using them in concrete;
  • Avoid pattern repetition, especially with patterns that mimic natural materials such as stone or slate. A random composition will look much more realistic;
  • You’ll get better results if you precondition, or coat, your stamp mats with some of the release agent. This will provide additional bond breaking to help ensure a clean imprint;
  • To obtain a random antiquing effect, apply a very small amount of powdered release to the surface of the concrete and then spray the liquid release over the top of it. The liquid dissolves the light layer of powder to leave subtle accents after the surface is stamped;
  • Be sure the release agent gets well-compressed into the concrete by the stamp. Otherwise, it will simply wash off the surface without leaving the desired colour;
  • Periodically check the alignment of the imprint stamps every couple of rows using a string line. It’s not uncommon for imprint stamps to shift as much as 1/4 inch per row, especially on sloped areas;
  • On many jobs, you’ll be faced with having to stamp up against a vertical surface, such as a wall or a column. Use a floppy mat and texturing to bend or flex up against these surfaces;
  • Be sure that the person walking on and moving the imprint stamps is wearing clean boots or work shoes, free of any pebbles, mud, or other debris. Inevitably, these contaminants will end up on top of the imprint stamps and fall onto the fresh concrete surface as the imprint stamps are being lifted;
  • If you’re using a powdered release, you can save time by sawcutting the contraction joints before removing the release. This allows you to remove the release residue and the dust created from sawing in one step.
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