Decorative Concrete Presentation by Dennis Ahal Ahal Contracting Co., Inc.
<ul><li>There are many methods and uses of decorative concrete, for both exterior and interior applications. </li></ul><ul><li>Concrete has come a long way from when it was used as a pathway to keep you out of the dirt. </li></ul>
One of the oldest methods used was scored joints, to not only control cracks but also to create a design.
Exposed aggregate is a method that has been around for a long time. The best, most durable method is to use a high proportion of aggregate in the mix rather than seeding the surface.
<ul><li>This mix looks extremely dry but is actually a 4” slump concrete that has a high aggregate content. The concrete is struck off. Any surface voids are filled in with concrete, not with paste. </li></ul>
The surface is bull-floated and closed up with a hand float. Again, any void areas are filled in with concrete and not paste.
A surface retarder containing dye is sprayed on the surface to ensure complete coverage. The slab is then covered with a polyethylene sheet to prevent air contact with the surface.
Either later that day or the next day, depending on temperature, the surface is broomed and washed to remove the surface cementitious coating and expose the aggregate.
The view when approaching the walk appears as a gravel path. The smaller the aggregate, the denser the amount at the surface.
One of the ways of disguising expansion joints is through the use of brick borders or imprinted concrete strips.
One of the ways of decorating concrete is through the use of integral color. Bag material has been used for many years but some coloring systems now use a liquid color agent.
The color always appears darker while the concrete is wet.
This integrally colored concrete is being used to grout rocks in a small decorative stream bed.
This walkway was designed to resemble a dirt pathway which would be handicap accessible even after a rain.
This walkway consists of traprock aggregate and charcoal gray integral color. It is being given a light acid wash to remove any film residue before being sealed with a penetrating sealer.
Notice the high aggregate content at the surface.
When dry the walkway appears much lighter, even though is has been sealed.
<ul><li>You can use a glossy surface sealer, but this must be maintained since it will deteriorate through wear and UV breakdown. </li></ul>
This area received a light colored integral color to blend with the aggregate so it appears as a gravel path. The area where sprinklers have wet the walk appear darker. This is what a glossy surface sealer would look like.
This project used the same aggregate but two different integral colors to highlight the main walk area and the borders.
Expansion joints are used for crack control and to show a pattern. Control joints are somewhat difficult to install in exposed aggregate since the joint tool tends to push the aggregate down and leave an area of plain grout.
This walk received areas of integrally colored concrete along with plain gray concrete to create a contrast. Integral colors give the concrete a tone but not an intense color.
This amusement park entrance used integrally colored concrete with diamonds of surface applied color hardener, which created interest and hid drains that occurred at some of these areas.
These adjacent areas used two different integral colors. The bench wall that separates them is also concrete.
The second method of coloring concrete is through the use of dry shake surface applied color hardener. This method gives a deeper, more intense color.
The material which is broadcast onto the surface adds to the durability of the surface.
<ul><li>The color hardener consists of color, cement, and silica quartz aggregate. </li></ul><ul><li>A more durable emery aggregate can be used for high traffic areas. </li></ul>
The correct application for this color hardener is two coats, usually at 90 degree angles from each other when possible, to assure adequate coverage.
As you can tell from the lack of hard hats and the model of the truck, this photo was taken a number of years ago. However, the process is still pretty much the same. The color is worked into the surface with a bull float.
The edges are run with a tool to create a nice clean edge.
In this photo, a stamping plastic is laid on the surface and imprinting tools are placed.
The tools are tapped into the concrete surface to create a pattern.
The finished areas show a pattern with expansion joints used to control cracking. These joints are imprinted deeper to receive a grout in the joints.
The grouting makes the cobblestone pattern look more authentic. The advantage of using concrete is that the slab is reinforced with rebar and stays together as one unit.
This close-up of the grout shows the loafing of the cobblestone pattern, created by stamping plastic and deeper joints. Since the slab works as a unit, there is no stress on the individual grout joints.
This grouted walkway is a running bond brick pattern.
This basket weave patio has other colors broadcast onto the surface to create interest.
This walkway and step project was placed next to an old stone foundation. Imagine the hand work that would be required to fit pavers adjacent to the stone.
This restaurant area used an 18” x 18” tile with grouted joints.
This atrium area used surface applied color hardener with tooled joints, which were grouted.
This project used multiple colors and patterns to define areas and foot traffic patterns.
The areas of the landings were adjusted slightly to fit the steps.
This was a 2” topping over existing concrete which contained many joints. A ¼” rubber mat was used to separate the topping from the sub-slab.
Polypropylene fibers were used in a pea gravel mix, and dry shake color hardener was applied.
This area received imprinted color hardener as an accent, with a picture frame tooling of the joints. This is actually an extra step and needs to be defined in the specification.
This is an imprinted area adjacent to an integrally colored salt finish area. The banded areas are cut with hand tools.
The salt finish is achieved by broadcasting rock salt and troweling it into the surface. The salt is washed away a day or two later, leaving voids.
This area consists of an integrally colored field which received a broom finish. The borders have color hardener and are hand cut. This method, while expensive, is less costly than pavers or bricks cut to fit this circular pattern.
This area was also hand cut. These types of areas were used as accents so, although they cost more, they did not materially affect the entire project cost.
The darker borders were poured with the main areas in order to save labor on forming and finishing.
This sample area shows a tooled joint being installed in fresh concrete.
Strips of masonite are placed in the joint to separate different colors as they are applied to various areas of the surface.
Fields and borders can be placed at the same time, saving forming and placing costs while receiving different colors and finishes.
Separate colors are being applied to adjacent areas of the same slab.
The color hardener is floated and troweled into the surface.
Edgers are run on the separate colors before imprinting.
The final product, showing multiple colors and finishes:
This area received a highlight, or flashing, of other colors to add an accent.
This shows a fishscale pattern merged into a running bond pattern, but the slab was placed as one piece.
Notice the expansion joint separating two slabs and the herringbone pattern placed with the limestone border, which is a separate color and pattern.
The release agent is broadcast onto the surface.
The release agent most often is of a contrasting color to the color hardener.
Texture mats are placed on the surface of the slab. These mats impart not only a design or pattern, but also a texture.
This is an overhead view of dry shake color hardener on the surface, before and after being floated and troweled into the surface.
There is also a release agent on a portion of the surface (gray area), some of which has been imprinted with a texture mat.
Texture mats come in various sizes and textures.
They are tapped into the slab surface to impart both pattern and texture.
Texture mats are flexible, to allow imprinting next to vertical surfaces such as windows and walls.
Sometimes they are overlapped to eliminate excess pattern lines.
Notice the clefting on this 5’ x 5’ slate texture mat.
This is a 12” pattern with little contrast between the color hardener and the release agent. Some of the release agent remains on the slab surface, giving highlights and a feeling of depth to the texture.
This shows the use of two colors and three patterns. The border against the wall was placed with the main gray slate area.
This curbing is not limestone. It is concrete with white color hardener applied.
This area was imprinted and textured to resemble an old, used brick.
Chemicals were used to stain the surface and add color variation.
Here a thin coat of a high intensity overlay material is being applied.
<ul><li>Use a separate section to specify decorative concrete. </li></ul><ul><li>Don’t let someone do your decorative concrete work just because they were low bidder on the flatwork. </li></ul><ul><li>Don’t be afraid to negotiate your specialty work, or at least qualify your contractors prior to bid time. </li></ul>
<ul><li>This is a product that is manufactured in the field, not a factory. Approved samples are always a must before starting the actual work, so expectations are the same. </li></ul>
The use of decorative concrete is limited only by your imagination.
Decorative Concrete Presentation by Dennis Ahal Ahal Contracting Co., Inc.