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Concrete Patio Stamped with Style

Hardscape, Patios, Stone and Concrete July 1, 2009 Sonia



 

By Monte Burch

 

Build a Patio with Decorative Concrete.

 

 

 

Concrete is one of mankind’s most useful inventions, and also one of the oldest. Highways, sidewalks, bridges, buildings, all are made of this utilitarian and often unglamorous product. Concrete, however, doesn’t have to be mundane. With a variety of techniques concrete can be made extremely decorative. Stained and stamped with a variety of patterns, concrete can look like bricks, cobblestone, flagstone, even wood, or a variety of unusual artistic patterns. Stained and stamped concrete can turn a ho-hum slab into a beautiful patio or sidewalk. It is also a great way of redoing an old, deteriorated walk or patio—simply pour fresh concrete over the old.

As with any concrete project, the proper form must be constructed to hold the concrete until it sets.

As with any concrete project, the proper form must be constructed to hold the concrete until it sets.

 

Prep the Site

The first step, as in any concrete project, is proper preparation of the site and building a form to hold the concrete in the desired shape. The sub-grade must be uniformly graded and evenly compacted. If pouring in hot weather, it is recommended to soak the ground prior to the pour. The sub-base material, however, must be dry at the time of the pour.

For an exterior project, the form must have a grade of at least 2 percent to allow for water runoff.

For an exterior project, the form must have a grade of at least 2 percent to allow for water runoff.

If pouring a patio or walk, the mix and reinforcing should meet the strengths of the project needs and be suitable for external paving. The formwork should be set to establish proper drainage of the area and to be used for screeding and layout. A minimum of 2-percent slope should be allowed for exterior paving sections. All grade pins should be set below grade to prevent interfering with the texturing process. All formwork should be properly squared, and also squared to any existing structures. This is especially important if using a patterned texturing tool.

If using pattern stamps and a square or rectangular pour, make sure the form is assembled square. The form can, however, incorporate rounded or irregular edges, with the stamps simply extending past the form boards.

If using pattern stamps and a square or rectangular pour, make sure the form is assembled square. The form can, however, incorporate rounded or irregular edges, with the stamps simply extending past the form boards.

 

Colorful Concrete

Two methods are used for coloring concrete, a spread-on color hardener or an integral colorant. Both can be used with ready-mixed or bagged materials. Color hardener has some dust and health hazards in application due to the content of the silica sand involved. The technique shown involves integral coloring products from Matcrete (www.Matcrete.com).

The simplest method of coloring the concrete is with and integral coloring agent, such as Matcrete Integral Color. The coloring agent can be mixed at the job site in ready-mix deliveries, or in small batches using bagged concrete.

The simplest method of coloring the concrete is with and integral coloring agent, such as Matcrete Integral Color. The coloring agent can be mixed at the job site in ready-mix deliveries, or in small batches using bagged concrete.

The Matcrete Integral Color is a pre-measured admixture for coloring ready-mixed concrete during batching. The pigments are lime-proof, pure synthetic mineral oxides for all concrete flat-work installations, interior floors and exterior hardscapes. The system also works for precast, tilt-up and cast-in-place applications. Packaged in 25-pound disintegrating bags, the product is available in a wide range of colors. The dosage rate found with the color swatch is the amount of color needed to tint 94 pounds of concrete. Typical dosage rates range from 1/4 to 4 pounds of Matcrete Integral Color per sack (94 pounds of cement). Exceeding 10-percent color content can have an adverse affect on the strength of the concrete. If a more vibrant color is desired, consider using Matcrete Dustone Color Hardener which, due to its application, is not limited to these same restrictions and in fact can increase surface strength. But you must follow all safety regulations.

Due to a wet area, as well as a sewer drain line near the pour, the concrete was delivered to the form from the ready-mix truck with a tractor bucket.

Due to a wet area, as well as a sewer drain line near the pour, the concrete was delivered to the form from the ready-mix truck with a tractor bucket.

Integral Color is added to the concrete in the mixing drum. If mixed at the plant, the drum must be cleaned, and approximately two-thirds of the mix water and one-half of the aggregates needed should be added to the drum. Do not use slurry water or reclaimed aggregates. Add the correct amount of Matcrete Integral Color to the drum and mix at full charging speed for three to five minutes or until all bags break apart and the pigment is distributed evenly. Add the balance of the ingredients (water, aggregates, cement and admixtures) and mix at full charging speed for 8 to 10 minutes (80 to 100 revolutions). It is the ready-mix supplier’s responsibility to make sure the bags have fully disintegrated. Note: A ready-mix company will probably charge a small fee for extra cleaning of the drum.

 

The colored concrete is poured in the form and shoveled or pulled into all portions of the form.

The colored concrete is poured in the form and shoveled or pulled into all portions of the form.

If coloring the concrete at the jobsite, open the bag and pour the pigment directly into the drum, then discard the bag. Again mix thoroughly before distribution. Mix color and pre-bagged concrete according to the manufacturer’s specific instructions.

A screed board is used to level the concrete to the form boards.

A screed board is used to level the concrete to the form boards.

 

Texture Options

The colored concrete can be finished in a variety of means. Use a bull float after striking off the slab. For most finishes, use wood bull floats and derbies, not magnesium. Wait for the bleed water sheen to disappear before you start floating and troweling. Do not over-trowel or start troweling late as this leads to burns and dark spots.

The edges should be smoothed using an edger, and then a float used to further smooth out the edges.

The edges should be smoothed using an edger, and then a float used to further smooth out the edges.

A bull float is used to smooth and float the concrete surface.

A bull float is used to smooth and float the concrete surface.

 

Following are some of the various textures that can be used with Matcrete Integral Color:

Broomed: Made by pulling special brooms across stiff, freshly floated or troweled concrete surface. For variety, broomed texture can be heavy or light, or in straight or wavy lines.

Exposed Aggregate: Aggregate is exposed by “seeding” the fresh concrete with aggregate, which can be colored, sparkling, fractured or smooth. Before the concrete sets thoroughly, a pressure washer is used to wash away some of the top surface and expose the aggregate. Set-retarding compounds are often used to slow the set, but make sure you follow the manufacturer’s instructions. The aggregate can also be exposed by removing the surface cement with acid etching, sand blasting, grinding or hammering. Exposure level can vary from barely revealing fine aggregate to up to 1/3 of the diameter of coarse aggregate exposed.

Stamping or Imprinting: Stamping tools are pressed into the concrete to create a pattern and then removed. A powder release agent or plastic sheet is placed on the concrete surface after floating and troweling.

Before stamping, a release agent such as Matcrete Release Powder should be applied. The product not only prevents the stamps from sticking, but also provides an additional color. The agent must be air-entrained before use.

Before stamping, a release agent such as Matcrete Release Powder should be applied. The product not only prevents the stamps from sticking, but also provides an additional color. The agent must be air-entrained before use.

 

Stamping in Detail

A wide variety of stamps are available ranging in design from brick, cobblestone, stone, and ashlar slate to patterns that resemble wooden planks. Matcrete has over 175 patterns to choose from. The concrete stamps are made from a high-quality urethane with fixed handles designed for quick and easy placement. Stamps are available as seamless imprinting or in set patterns. Seamless texture or non-directional patterns are the easiest and fastest way of stamping concrete as there is no set direction or lay-down pattern to follow. Regardless, a wide set of variables is involved in properly imprinting concrete including: temperature, sunlight or shade, wind, access and the depth of the stamping tool.

Once the concrete is sturdy enough to support a person and the stamps, the stapms are applied. In most instances you will need enough stamps to go across one end of the pour. Postion one stamp following the manufacturer's instructions.

Once the concrete is sturdy enough to support a person and the stamps, the stapms are applied. In most instances you will need enough stamps to go across one end of the pour. Postion one stamp following the manufacturer’s instructions.

The release powder is sprinkled uniformly on the surface.

The release powder is sprinkled uniformly on the surface.

 

 

 

Regardless of the design used, the concrete should be covered with either a plastic membrane or release powder to prevent the cement from sticking to the concrete stamp. Matcrete Release Powder, a fine talc-like powder, is not only quick and easy to use; it adds a secondary color to the Color Hardened concrete. Before application of the release powder, it should be air-entrained to beat air back into it. The fine powder settles during transportation. A portable electric drill and paddle mixer works quite well. Broadcast the powder over the surface by hand, brush or even the lid from the bucket. Broadcast as low to the surface as possible, tossing the powder across and not down on the surface. Avoid lumps on the surface, as this may create blank spots in the texture. The rate of application depends on the concrete set rate, depth of desired texture and wind speed. Do not apply this on a windy day. Approximately 3-1/2 pounds is required per 100 feet.

Make sure you correctly lift the stamps and do not drag or shift them on the concrete. Then simply repeat the process, applying the stamps according to the manufacturer's instructions for the specific stamps.

Make sure you correctly lift the stamps and do not drag or shift them on the concrete. Then simply repeat the process, applying the stamps according to the manufacturer’s instructions for the specific stamps.

Position the remaining stamps in the row and tamp as per the instructions. In some instances you can "walk" on the stamps for the imprint, but a tamper makes the chore more precise.

Position the remaining stamps in the row and tamp as per the instructions. In some instances you can “walk” on the stamps for the imprint, but a tamper makes the chore more precise.

 

 

Patterned Stamping

Patterned stamping requires careful layout and tool placement. Joint spacing must be considered. You will need stamping tools to span the entire slab in one direction and begin the second row. It’s a good idea to lay out the design and even lay out the stamping tools in the pattern desired next to the pour, so you’re sure of the tool positioning. Once you have determined the pattern, and that the concrete will hold up to the weight of the person and tool, you’re ready to place the first stamp.

The stamped concrete and release agent shoudl be allowed to cure for at least 48 hours.

The stamped concrete and release agent shoudl be allowed to cure for at least 48 hours.

At the edges, allow the stamping tool to hang off the edge.

At the edges, allow the stamping tool to hang off the edge.

 

Place the stamp flat on the surface of the concrete using the handles on the back. If possible, start against the structure or any straight edge that will permit the tool to remain square. Do not drag the stamp across the concrete as this will scuff and scratch the surface and mar the imprint. Continue to set the remaining stamping tools, following the instructions for that particular pattern. Patterned tools are color-coded to help reduce pattern repeat on the surface. Rotate the colors so the surface is randomly stamped.

 

Using a pressure washer with at least 2,000 psi, wash the remaining powder from the surface.

Using a pressure washer with at least 2,000 psi, wash the remaining powder from the surface.

Sweep off the excess powder. If possible, capture the excess powder for proper disposal.

Sweep off the excess powder. If possible, capture the excess powder for proper disposal.

Once all the tools are in place, use a pounder or tamping tool to create the imprint. If the concrete is too soft to continue stamping you should refrain from stamping until it has the same consistency and will properly support the weight of the person and tool. Continue to move and tamp the tools in the direction of the pour until the entire surface has been imprinted. Always set the next row tight to the first to keep the lines square. Using a small Seamless Texture Skin, work around hard-to-reach edges such as steps, walls and columns. Additional detailing can be done using a touch wheel and chisels.

An old, discolored sidewalk or patio can be brightened by pouring new concrete over the old and creating a colored and stamped design.

An old, discolored sidewalk or patio can be brightened by pouring new concrete over the old and creating a colored and stamped design.

You may also wish to use a soft-bristle push broom to remove stubborn areas.

You may also wish to use a soft-bristle push broom to remove stubborn areas.

 

 

Seamless Texturing

You will need a minimum of three large Seamless Texture Skins. Place the first flat on the surface using the handles. Then place the second and third, overlapping each by 4 to 6 inches. Once you have stamped the texture evenly into the concrete you must underlap the first skin from the other two before you can pick it up and move into the next position. Repeat the process until you have covered the complete area. When you move each stamp, rotate it 90 degrees to ensure there is no repeat of the design.

Small jobs can be poured using bagged concrete, which can be easily mixed and poured using a Crete-sheet mixing bag.

Small jobs can be poured using bagged concrete, which can be easily mixed and poured using a Crete-sheet mixing bag.

 

Curing and Cleanup

The next steps are curing and wash-down. The main purpose of curing is to increase durability and reduce early carbonation on the surface. Keeping the powdered release agent on the surface for a period of seven days will help prevent early carbonation by limiting the exposure to carbon dioxide in the atmosphere. Regardless, it is recommended the concrete has a minimum of 48 hours to harden before the wash-down procedure.

The first step is to remove all forms, then sweep excess release powder from the surface. Collect as much of the release powder as possible in a ditch or sump hole. Then dampen the concrete surface with water. Using a pressure washer with a minimum of 2,000 psi, clean off the release powder. Working the dampened surface with a soft-bristle push broom will also help. Matcrete Antique Release and Efflorescence remover can also be used to remove stubborn stains. Clean the concrete surface until the water runs clear and the overall appearance is desired.

The final step is to apply a sealer to protect the concrete and seal in the coloring. A number of sealers are available, and it’s extremely important to follow the directions for the specific sealer. The concrete should be sufficiently cured and moisture migration complete. The surface must be free of dust, debris, moisture and any other contaminants. The first coat of sealer should be applied evenly with a high-pressure sprayer. The second coat can be applied when the first coat has thoroughly dried (three hour re-coat time). Depending on the porosity of the concrete, you may need a third coat. Foot traffic is permitted within 24 hours and vehicular within 72 hours.

 


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