Exposed aggregate concrete is a great design solution for public spaces. The attractive durable not slip surface makes it an ideal choice for landscape architects. High traffic areas around public buildings often use this type of concrete path.
Exposed Aggregate Colours
The aggregates are available in a wide range of colours to suit your landscape design. The available colours include red, brown, dark grey basalt, green quarts as well as black and white. In combination with this selection, the fine grain aggregates or sands are also available in a wide range of selections. The colour of these these fine aggregate will also be the more dominant when the surface is lightly abraded. However, more heavily abraded surfaces will result in more of the colour of the course aggregates showing. This will result in a different appearance for the exposed aggregate concrete path. Coupled with this, the cement matrix can also have colour added. Always take these factors into account when selecting the aggregates and especially during the process of exposing the aggregates.
Exposing the aggregate
In addition to this, exposing the aggregate at a different concrete curing time can lead to different appearance. Similarly, this can result in colour differences for the same site for the same aggregate concrete pathway. To maintain quality, the landscaper must use a consistent approach to exposing the aggregates. As a rule of thumb, no more than 1/3 of the aggregate should be exposed.
The suitability of Exposed Aggregate Pathways
The landscape architect needs to also consider the use of the exposed aggregate concrete path when selecting the aggregate. Use a fine rounded aggregate for areas near swimming pools. For exposed aggregate concrete paths where water drainage is important, 19mm aggregates should be used. Exposed aggregates of more than 20mm can be very difficult to transport using a concrete pump.
Exposed aggregate concrete strength
When rounded pebbles are used throughout the path, the path will be slightly less strong. This is because the matrix will not bond to the aggregate as tightly as it will with rough shaped aggregates. Generally, the path should be at least 100mm thick N25 concrete. N25 means that the concrete will achieve a compressive strength of 25 mPa after 28 days.
Even the strongest concrete will be weak in tension or bending and even properly cured concrete will have microcracks. Therefore, to minimise cracking steel reinforcement must be used. For pathways, this should be at least SL 72 using saddles to keep it in the top 1/3 of the concrete. SL72 means that the bars are each 7mm in diameter with grids of 200mm. The path should be laid on 100mm thick class 3 roadbase , if it is for public spaces. If there is any possibility of a vehicle driving on the path, then the path needs to be built like an exposed aggregate concrete driveway. This will be the case with any vehicle crossovers in the path design. In these cases the concrete needs to be at lease 125mm thick N32 (32mPa) concrete with SL92 mesh laid on at least 100mm of class 2 roadbase.
Landscape design with exposed aggregate concrete
Using alternating concrete colour to break up large areas of concrete.
When the customer requirements call for a large expanse of exposed concrete, alternating contrasting colours can help to break up the appearance. The public space at Balwyn Community Centre, Melbourne, used alternating exposed aggregate concrete of Hanson Bokhara with Hanson Galaxy. The artificial turf also helps to break the appearance of the large area of concrete and gives the area a more tranquil appearance. (ACLA Consultants landscape architects.)
Frequently asked questions about Exposed Aggregate Concrete
Is Exposed aggregate concrete expensive?
Exposed aggregate will be more expensive than normal concrete solutions. It will however, add more value and landscaping interest to your property. There is also extra labour in exposing the aggregate. Alternating colours is also great way to break up the large expanses of concrete. It will similarly add to the cost, but will add great value to your property.
Should you seal Exposed Aggregate Concrete?
Sealing is essential for these paths. The high quality sealer we use helps to maintain the appearance of the coloured concrete by preventing stains getting into the pores of the concrete. The sealer also helps to prevent dust coming off the concrete.
Is Exposed Aggregate Concrete Durable?
It is important not to exposed too much of the aggregate during the water pressure cleaning part of the process. This is because exposing the aggregate excessively will result in it breaking loose from the matrix. Do not expose them more than 30%. The concrete we use for pathways is N25 with SL72 reinforcement over a thick layer of roadbase.
Residential Concreting Solutions
For residential concreting solutions a smaller version of the commercial landscaping concepts can be applied. In some cases it will be necessary to cart the aggregate mix in by wheelbarrow.
Related Landscaping Ideas from Red’s Landscaping
Exposed Aggregate Concrete Melbourne
Concrete Designs, textures and colours
Outwest Concrete have a great range of aggregate colours available.