The Impressed Concrete Process
This is an overview of the process of concrete stamping or pattern impressed concrete.
Stamped Concrete
This system involves colouring ready-mixed concrete and imprinting authentic looking patterns of brick, stone, slate, wood or other natural textures into partially set concrete. Stamped concrete looks great around pools, patios, driveways and walkways. It can also be a good alternative to internal tiled areas such as giving your kitchen that authentic country style flagstone floor look. Stamped concrete is a very cost effective alternative to installing natural materials and is usually around 1/3 of the cost with almost zero maintenace.
The process
Prepare the terrain
Pour the concrete
Prepare the concrete
Colour the concrete
Apply the release agent and Imprint the texture
Washing off the release agent
Sealing the finished article
The finished article
Before beginning any job the correct preperation needs to be done. All designs, colours and finishes need to be worked out and agreed with the owner before any work is commenced. Once the designs have been agreed we will begin excavating or infilling the areas with hardcore so that the correct levels are established prior to the concrete being poured.
The owner can choose to do this stage of the preperation them self's if cost is an issue.
After the initial preparation skids are laid out around the area to be concrete stamped in the agreed design. Hard core is then compacted into these areas so that a minimun of 100 mm of concrete is needed to bring the finished job to the correct height. On driveways we like to use a minimum of 150 mm to allow for the extra traffic weight in these areas.
Once the hard core has been compacted we use a thin layer of sand to allow slight movement of the concrete during natural contraction while drying. This produces a surface that allows the concrete to move slightly and reduces the risk of stress cracks appearing latter on. Expansion joints cut later in the process should completely eliminate the chances of any cracking due to contraction being visible.
The concrete is a specially formulated mix that allows for a certain working time after pouring. This allows for the time needed to prepare the area for stamping. Special fibers are mixed with the concrete which force it to bind giving it a high tensile strength reducing the risk of any cracking.
Depending on the size of the area to be stamped, the concrete will be delivered ready mixed or we will mix it on site. If the concrete is delivered ready mixed, access to the delivery point will need to be assessed. If a mixer is unable to access the immediate area a special pump will need to be arranged so that the mix can be delivered directly to the work area.
Once the concrete has been poured into the immediate working area it needs to be racked evenly to remove any high or low points and ensure it is spread as evenly as possible. A special tamping roller is then used to force the top layer of aggregate in the concrete down to a working depth which will allow the colour hardener to be properly applied and evenly mixed.
The surface is then floated with special floats in preparation for the colour to be applied.
After the excess bleed water has evaporated the colour is ready to be applied to the concrete surface.
The required colour is applied to the exposed concrete surface using a dry shake method. Depending on the affect required for the finished surface more than one colour can be applied at this time in a random fashion that covers the surface evenly. The colour is then worked into the concrete leaving a slick finish.
A release agent is then applied evenly across the surface. The release agent stops the stamping tools from sticking too and pulling up the surface of the concrete. It can also be used to impart another colour shade to the finished work for affects such as antiquing.
Special textured skins are placed on the surface to imprint the desired pattern. The initial placing of the skins is important as the pattern will be extended from this initial point right across the slab surface and to the edge of the skids as well to as any other obstacles such as walls. The pattern should be worked out such that the design can be broken up or deviated at varying intervals with the likes of borders or drainage so that expansion joints can later be cut and hidden in an unobtrusive way.
A tamper is used on the skins to firmly imprint the pattern into the concrete. The skins are moved after tamping and placed in a position that keeps the pattern tight. Awkward areas are worked out using more flexible skins that allow us to get right up to the edge of walls or allow for the pattern to deviate in slopped areas.
The concrete should be left to stand and harden for 1 or more days depending on the weather and climate conditions before the release agent is pressure washed away from the surface. By leaving varying amounts of release agent on the surface an aged affect can be achieved making the finished effect look older than it is.
After the slab has been left to dry completely, a sealer is applied to permanently seal the surface. This sealer can be used to achieve a mat or gloss finish and is non-slip for areas such as pool surrounds. The sealer enhances the finished colour and will protect the concrete for many years, providing an easy clean durable surface that will resist staining including engine oil on driveways.
Once the sealer has dried it can be cleaned when required using a detergent mixed with water. The finished item will not sink or part like block paving and will not allow weeds to grow through providing you with a virtually maintenance free area.
Q & A
Does stamped concrete crack?
Will the colours fade?
Is stamped concrete durable?
Any concrete MAY crack. To minimise the risk it should be installed by an expert trained in stamping concrete. An expert will know the sub-grade must be structuarly sound before the work is carried out. They will know that the mix of the concrete is important and that steal reinforcement may need to be used for strength in places as well as the fact that the fibers provide excellent bonding. They will know where to place proper control and expansion joints to minimise the possibility of cracking occuring. In the end, should your concrete crack it should only be hair-line cracks that form and most of your friends and family will never notice them unless you point them out.
The colours used in the concrete stamping process are the same as those used to manufacture bricks. They are a sythetic metal oxide pigment which does not fade noticably over time, even after many years. It is advisable that you have the surface re-sealed every 2 or 3 years to ensure you do not notice any significant colour fade. This is like rewaxing your wooden floor or the family car, once done the colours should be as clear as the day it was originally sealed.
If installed by an expert stamped concrete is more durable than any other type of installation. It does not suffer from extreams of hot and cold or move during freeze/thaw cycles like paved and tiled areas. It is reinforced with special fibers to enable excellent bonding that gives the concrete enough tensile strength to withstand almost any climate. Stamped concrete also does not have grout or sand joints that over time will deteriate and allowing grass and weeds to grow through. This product really is low maintenance. During the winter you should use sand only to melt ice and snow build up NEVER USE SALT. Salt will eat all types of masonry including concrete.
The same should be said of any acid based cleaners. Acids may deteriate the sealer applied to the concrete surface and should not be used as a cleaning agent.
