concrete designs

Hanson Bokhara Exposed aggregate concrete.

Exposed aggregate concrete paths

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.

Preventing Cracks

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

Outdoor Furniture on Exposed aggregate concrete.

Durable Outdoor Garden Furniture on Exposed aggregate concrete. ACLA Consultants landscape architects.

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.)

Contrasting Exposed aggregate concrete

Creating some shade with a tree in the concreted area. The tree roots are protected with a slotted stainless steel grate. The lighter colour Hansen Galaxy forms a geometric pattern around the grate.(ACLA Consultants landscape architects.)

 

Drinking Fountain and exposed aggregate concrete.

Drinking Fountain and exposed aggregate concrete. Hanson Bokhara contrasts well with the natural concrete in-situ walls. (ACLA Consultants landscape architects.)

 

Hanson Bokhara Exposed aggregate concrete.

Exposed aggregate concrete is ideal for garden steps and stairs to help maintain grip. Recent sealing of the concrete makes it appear slightly darker. (ACLA Consultants landscape architects.)

 

Alternating exposed aggregate

Alternating exposed aggregate path.  Garden beds also break up the space. Sunbury Global Learning Centre.

 

Alternating decorative finish path

Alternating coloured path with centre native garden. Sunbury Global Learning Centre.

 

Entrance and Alternating decorative finish concrete path

Building entrance and Alternating exposed coloured path. Sunbury Global Learning Centre.

 

Concrete block garden retaining wall with coping next to the decorative finish concrete path.

Concrete block garden retaining wall with coping next to the alternating exposed coloured path. Sunbury Global Learning Centre. Hanson Bruthen and Hanson Galaxy.

 

Alternating colours of the concrete decorative finish entrance way.

The decorative finish of the alternating decorative finish of the entranceway looks striking when compared to the old concrete footpath in the foreground. Sunbury Global Learning Centre.

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.

Newly sealed paths at Balwyn Community Centre

 

 

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.

Exposed Aggregate Concrete Melbourne

Concrete Designs, textures and colours

Outwest Concrete have a great range of  aggregate colours available.

Colours and Textures available.

 

More information on decorative concretes

 

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In-situ concrete retaining wall and garden steps.

In-situ Concrete

In-situ Concrete, also known as insitu concrete, is an outstanding landscaping construction technique. In terms of long terms long term quality, robustness and longevity very few landscape construction techniques come close. To many people in-situ concrete is better know as landscaping architectural concrete and it is the point where landscaping, architecture and civil engineering all meet in landscape design.

For the landscape design of public spaces, architectural concrete or in-situ concrete is a great choice for the severe use of our landscaped parks, gardens or commercial buildings. For these reasons, insitu concrete is now widely used by commercial landscapers in Melbourne. 

Some other names for in-situ concrete include “poured in place” concrete or “cast in place”  concrete”.

What is in-situ concrete?

In-Situ Concrete cast in place.

In-situ is concrete that as poured into formwork at the building site. When compared to pre-cast concrete, in-situ requires no crane or forklift to get it into position.

In comparison with concrete block and rendered retaining walls, the very low porosity of sealed and vibed in-situ walls will ensure a quality finish for decades of use. With concrete block retaining walls, the blocks themselves will have some porosity which will allow moisture to creep under the rendered surface and may cause it to lift in a few years. In-situ concrete has the colour mixed in and the texture is provided by the formwork but it can be rendered if required.

In-situ Concrete pumped into the formwork.

In-situ Concrete pumped into the formwork through a boom.

In-Situ Concrete – strong connection to footings.

An additional advantage with in-situ  is it has a very strong and stable attachment to the very solid footings underneath. This is due to the reinforcement bars coming up from the footings and overlapping with the in-situ concrete steel reinforcement.  When compared with concrete block retaining walls, although the steel reinforcement runs up through the centre of the blocks, any voids in the concrete around the reinforcement can lead to corrosion of the reinforcement bars and concrete cancer. The homogeneity of the of the vibed in-situ walls also ensures a good attachment to the steel reinforcing bars and does not suffer the risk of a poor attachment of the core concrete to the inner void of the concrete blocks.

Pre-cast concrete will usually require mechanical fixings to the footing. These fixings can corrode over time or can be ground off by vandals. Being securely attached to the footings is a big advantage of in-situ concrete. Newly constructed public spaces such as parks and gardens will often rely on these quality advantages of in-situ concrete.

Retaining wall footings.

Retaining wall footings with steel reinforcement protruding to give the retaining wall a strong connection to the footing. The reinforcement bars must be accurately placed.

Precast concrete versus in-situ in landscaping concrete architecture.

One of the advantages of precast concrete is that it is manufactured under controlled conditions in a factory. This ensures a consistent quality product. There can be a risk however of coloured concrete coming from different batches resulting in slightly different colours close together. The quality advantages of precast concrete can be matched by in-situ concrete with close attention to the details and quality control of the processes.

 

Quality in-situ concrete retaining walls, stairs and seating.

Commercial Retaining Walls Melbourne

Good quality in-situ concreting requires a lot of attention to the materials and the processes. In-situ concrete wall also need to consider the safety as well as the aesthetics of a public space or residential landscape construction project. A well constructed, quality, curved in-situ concrete wall will achieve both of these aims. For this reason always employ only skilled commercial concrete contractors.

 

Stripping the formwork off the walls.

Stripping the formwork off the walls. Extra effort and attention to detail will result in a quality finish on the retaining walls.

Quality In-situ concreting footings.

Concrete sets by a chemical reaction and not by drying. The chemical reaction is ecothermic and water is part of the reaction. If there is a difference in temperature within the concrete or if the water evaporates quickly from the top surface, then cracking can be the result. Concrete footings should not be poured in freezing conditions or below 5 degrees. Fortunately, in Melbourne there are very few days when it is too cold to pour. In hot weather the concrete should not be poured during the hottest part of the day or in extremely hot weather. The top part of the footing can be kept moist with hessian or a light sprinkling of water to prevent the top layer of the footing being weaker.

Concrete reinforcement bars in the footings.

It is essential that the vertical bars coming out of the footing are located accurately. When the in-situ walls are poured, these bars need to be closed to the centre of the retaining wall with good overlap with the wall reinforcement. The concrete reinforcement within the footing should be encased within the concrete as much as possible to minimise the paths for moisture to get into the reinforcement.

 

Concrete footing design

If designing for in-situ concrete retaining walls, the concrete footing should be a suitable size for the wall, keeping in mind all of the loads on the wall including hydrostatic and mass of the wall. The design of the footings must be to Australian Standards.

 

Formwork for in-situ concrete retaining walls.

Quality in-situ walls require formwork that is smooth, strong and flexible.  Any defect, imperfection of inaccuracy in the formwork will show up in the surface of the wall. The formwork for commercial concrete construction needs to be strong enough to resist the weight of the wet concrete without bulging or deforming. Deflections in timer formwork will show up as ripples in the finished wall. A bulge in the formwork due to the hydrostatic load of the concrete will be a disaster when removing the formwork from the wall. The wall should be designed with a slight draft angle to make the removal easy without causing any damage to the retaining wall.

Strong supports for the formwork.

Strong supports for the formwork keep the wall dimensionally correct.

 

Accurately positioned formwork under construction.

Accurately positioned formwork under construction.

 

Pouring the concrete retaining walls.

Pouring the concrete retaining walls. Using the concrete vibrator to get a quality finish and good adhesion to the reinforcement.

 

 

Commercial Concreting. Stripping the formwork after the concrete pour.

Stripping the formwork after the concrete pour. The top tip from commercial concreting is that the formwork should be left on as long as possible to prevent the concrete drying excessively during curing. Taking the formwork off too early can result in microcracks in the concrete.

 

Commercial Concreting Melbourne at our Balwyn North Construction site. Stripping the formwork after the concrete pour

Stripping the formwork after the concrete pour and curing to show a quality result.

 

In-situ concrete steel reinforcement

The steel reinforcement bars must have a good overlap with the footing reinforcement bars and well encased within the concrete wall. Reinforcement too close to the surface may result in water ingress and concrete cancer.

 

Pouring the in-situ concrete.

The concrete walls should be poured in one go and definitely from the same batch of concrete.  Any interruption of the pour may show up as a line in the finished wall.  The freshly poured concrete should be thoroughly vibed to ensure there are no voids within the concrete especially on the outer surfaces or at the interface with the reinforcement.

The steel reinforcement within tin-situ also helps to prevent surface cracking. To minimise the surface cracks, we leave the formwork in place a little longer to keep the moisture in during curing. The concrete should then be given a light sprinkle of water once the formwork is removed as it is still curing. The concrete will not be fully cured for a few weeks so consider this before applying any excessive loads.

Landscape and Concrete Design

Landscape Design with in-situ walls.

In-situ walls give the landscape designer or the landscape architect enormous freedom to design shapes for retaining walls, seating  or concrete stairs that would be very difficult, if not impossible, using precast of other landscape construction techniques. In-situ walls can be designed into three dimensional shapes that would be impossible or expensive to do as Pre-cast. Curved retaining walls on an uneven landscape would be very difficult to achieve with any other landscape construction technique. Another advantage is the wide range of colours available.

In-situ concrete curved seating part of our commercial concrete construction Melbourne portfolio.

In-situ concrete curved seating. Shapes like this are difficult with other landscape construction techniques.

 

Concrete stairs Cast in Place

Concrete stairs Cast in Place. This process is ideal for intricate or bespoke designs.

 

 

In-situ curved garden retaining wall.

Exposed aggregate path and in-situ curved garden retaining wall. Overflowing Australian native grasses in the garden bed soften the look of the concrete. The exposed aggregate path provides an attractive contrast to the wall and plants. It is also a safe non-slip cost-effective solution.

 

In-situ retaining wall and steps

In-situ retaining wall and steps

 

Curved In-Situ retaining wall.

Curved In-Situ retaining wall prior to the final touch up and surface treatment. The joins in the formwork will be visible until the concrete is ground back to an even join.

As the concrete is pumped in, damage to other landscaping structures can be avoided, making it  easier for the landscape project planner to  schedule the construction. These are important factors to consider when landscaping Melbourne public spaces.

In-Situ retaining wall.

A very straight In-Situ retaining wall.

 

In-situ retaining wall

Exposed aggregate pathway and in-situ retaining wall prior to filling and grinding by the concrete finisher. There will always be a few small voids to fill, but theses can be minimised with the vibe during the pour.

Related Commercial Landscaping information from Red’s Landscaping Melbourne

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© 2020 Reds Landscaping and Civil quality commercial landscaping Melbourne

More Information on Commercial Landscaping with In-Situ Concrete.

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See also Concrete Architecture in Landscaping

 

Concrete For Landscape Design & Construction

 

 

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Concrete Architecture

Concrete Architecture in Landscaping

Concrete architecture in landscaping is often seen of as a brutalist approach to landscape design. It is however possible to soften the design of concrete architecture with the use of landscape design techniques such as ponds or garden beds as well as using textiles such as cushions. The concrete architecture can also be softened with the use of naturalistic materials in the garden design such as timber or terracotta pots. The bringing together of cottage garden design with concrete architecture create a fusion of two very different garden design themes.

Garden Rocks

Naturalistic materials like these garden rocks help to soften the look of the in-situ concrete stairs.

Concrete Architecture design ideas

Concrete Designs

To see how to use concrete architecture in garden design, a visit to one of the bigger garden shows will help. Possibly the most famous of these shows is the annual Chelsea flower show held over 5 days in May each year. Unfortunately, there will be no show in 2020.  Due to the time constraints of a 5-day garden show, much of the concrete will be precast elsewhere and craned into place. To see examples of in-situ concrete, a visit to some of the recently constructed Melbourne public spaces such as Balwyn Community Centre or the Sunbury Global learning centre will provide some ideas.

Concrete Architecture

Concrete Architecture can be softened with garden plants and garden furniture. Sunken garden Chelsea Flower Show Gold Medal winner 2018. Kate Gould Gardens. Designed as a concept for a traditional square London West-End garden.

Concrete Designs

Precast Concrete Architecture

Formal blocks of stone and concrete with  foxgloves. Skin Deep. Garden designed by Robert Barker design. The blocks represent different human faces and skin conditions. Note the use of colour and texture in the concrete blocks. Plants were also chosen for form and texture.

 

Landscape design Ideas Urban Flow by Tonny Woods

An outdoor kitchen design using a concrete bench with cooktop, wooden paling fence and vertical kitchen garden. Urban Flow by Tony Woods combines bold landscape design with practical solutions.

 

Garden Pond. Landscape design idea

Garden Pond. Landscape design idea. A pond with overhanging flowers will soften the look of the garden.

 

Garden idea - Sunken Garden

Great colour coordination with the natural concrete colour with matching outdoor couches. Note how the cushions match the colours of the garden. Chelsea Flower Show 2018. Landscape design by Hay-Joung Hwang.

 

LG Eco-City Garden

The LG Eco-City Garden by Hay-Joung Hwang, represents one housing unit in a vertical forest. Note the use of coloured stone to provide a theme through the garden. The concrete has been softened with the use of soft furnishings, abundant lupins and a pond with concrete stepping stones.

 

Garden idea. Pond with concrete stepping stones.

Garden idea. Pond with concrete stepping stones. LG Eco-City Garden Chelsea Flower show 2018.

 

Curved Garden Seat garden design idea.

Curved garden seat with irregular stone paving. Design by Naomi Ferrett Cohen – Chelsea Flower show 2018.

Related Concrete Architecture and Landscaping Ideas from Red’s Landscaping

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5 Great Landscaping Ideas.

 

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Even More garden design ideas

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© 2020 Reds Landscaping and Civil quality commercial landscaping Melbourne

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