take-a-break unwind calm by nyut545e2





contents >

Public Domain Awards on again in 2009
Page 1 > Scenes from a mall Page 3 >
Scarborough Beach – the new jewel in
Perth’s crown Page 6 > Jacaranda
Square – more than just an everyday
experience Page 8 > A new life for
Barcom Park Page 10 > Formwork for
Off–form Concrete Page 12 >
                                                   Public Domain
                                                   Awards on again
                                                   in 2009 >

Entries are now being accepted for the             Designed around a triangular courtyard, the
2009 CCAA Public Domain Awards, the                Mausoleum features a series of semi-enclosed
pre-eminent awards for the innovative              galleries defined by dramatic black and white
use of concrete in the urban landscape.            precast concrete walls with cut-out profiles
The CCAA Public Domain Awards will again           that project light and shadows across the
shine a spotlight on Australia’s best examples     interior spaces.
of concrete design and construction in 2009.       The 2007 Awards Jury described the project
The Awards recognise outstanding and               as “a truly exciting example of the use of
innovative projects that feature concrete in any   standard precast concrete panels to maximum
of seven categories - Streets, Paths, Precincts,   dramatic effect - defining spaces, projecting
Walls, Bridges, Public Artworks and                shadows and inviting reflection while,
Sustainable Design.                                simultaneously, suggesting vitality.”

One project is also named the overall national     In 2005, the major award went to the National
winner, while the best project from each           Emergency Services Memorial, in Canberra,
State/Territory is also acknowledged.              designed by Aspect Melbourne Pty Ltd for the
                                                   National Capital Authority.
Over the past decade, the biennial Public
Domain Awards have grown in stature and are        The Memorial uses a mix of dramatic
today highly prized by Australia’s architectural   sculptural forms, images and words to express
fraternity.                                        the values and professionalism of Australia’s
                                                   emergency services personnel. It features a
This is confirmed by the quality of winning        raised and folded concrete ‘blanket’ wall to
entries from recent Awards.                        convey the sense of safety afforded by
In 2007, the overall national winner was the       emergency personnel.
Luciano Rossetti Mausoleum, at Springvale          The judging panel described the project as “an
near Melbourne, designed by Harmer                 almost perfect example of the flexibility of
Architecture and constructed by Galvin             (concrete) and its potential for integration with
Constructions.                                     any setting.”

page 1 the public domain November 2008
Going back to the 2003 Awards, the overall
winner was another ACT project, the public
precinct of Canberra’s acclaimed National
Museum of Australia.
Landscape architects for this winning project
were Room 4.1.3, and contractor Urban
Contractors. Project architects were Ashton
Raggatt McDougall and Robert Peck von
Hartel Trethowan.
The Museum’s outdoor precinct features the
Garden of Australian Dreams, a giant map of
European and indigenous boundaries and
place names ‘written’ in coloured and multi-
textured concrete, as well the Uluru Axis, a
huge red ‘line’ that rises out of the ground and
curls back on itself as a symbol of a maturing
country that is able to draw strength from
The wider precinct also showcases a range of
coloured and textured concrete surfaces
across its extensive paved and landscaped
The judges described the project as ‘an
extraordinary landscape work’.
Nominations for the 2009 Public Domain
Awards close on March 31, 2009. Projects
can be entered by anyone involved in the
project, including the architect, engineer,
contractor or asset owner.
To be eligible, nominated projects must have
been completed between June 1 2007 and
April 1 2009.
More information and/or nomination forms can
be downloaded at www.ccaa.com.au

page 2 the public domain November 2008
Scenes from
a mall >

Footscray’s Nicholson Street Mall is once
again a source of civic pride, thanks to a
unique and sensitive reworking of this
landmark community space.

page 3 the public domain November 2008
   It’s mid-morning in Nicholson Street Mall. A      aggregate, providing texture and helping to

   group of elderly Italian men stake their claim    disguise day-to-day dirt and grime. All the
   to a bench, settling in to dissect and debate     pavers have a milled finish.
   the state of the world around them.               Snaking through the centre of the mall is a
   This scene, played out almost every day, is       broken ‘ribbon’ of yellow rubber pebbled
   evidence why the recent refurbishment of the      screed. This ‘line of intensity’ represents and
   Mall has been so important to Footscray           reflects the vibrancy of local cultural life. On a
   locals.                                           more practical scale, it also serves to group
   The Mall is a hub, a natural meeting place for    together the functional elements of the mall –
   a multi-cultural community that places great      the street furniture and fittings.
   value on having a central space where its         The modular precast concrete benches are, in
   individual members can come together.             their careful design and execution, as much
   Opened in 1971, the original Nicholson Street     artwork as seating. They were designed and
   pedestrian mall was the first of its kind in      cast as modules that could stand alone or be
   Australia.                                        interlocked. This cost-effective approach
                                                     enabled the design team to create a variety of
   Landscape architects Hassell have built on this   seating configurations from just a couple of
   legacy of innovation, designing a vibrant,        moulds.
   dynamic and robust civic space that responds
   to the current and future needs of the            The geometric complexity of the designs
   community. Indeed, the project is an integral     required careful planning and a close working
   part of the long-term strategy of Maribyrnong     relationship between Hassell and the
   City Council to transform Footscray into the      precaster, SVC Products. The success of this
   next transition suburb on the edge of the         partnership is self-evident.
   Melbourne CBD.                                    An almond-coloured concrete mix was used to
   Concrete pavers and precast furniture figure      distinguish the seating from the ground plane.
   prominently in the Mall makeover. Both dark       The seats were lightly sandblasted to provide
   and light grey coloured pavers have been used     a durable, textured finish and treated with an
   across the space – the darker ‘bluestone’         anti-graffiti sealant.
   contrasting with the lighter grey. The latter     The seats also feature sections of timber
   feature speckles of brown and quartz              slatwork, ‘floating’ on stainless steel framing

   page 4 the public domain November 2008
                                         fixed to the top of the concrete. These dark
                                         timber slats provide another layer of contrast
                                         to the overall tapestry of colour and texture in
                                         the Mall.
                                         The revitalised Nicholson Street Mall
                                         represents a community of ideas, a successful
                                         collaboration between the designers,
                                         contractors and fabricators, Council,
                                         engineers, artists and locals.
                                         To quote the design team: ‘It’s a clear
                                         example of how landscape architecture can
                                         provide direct benefits to a community
                                         through the enhancement of civic spaces at
                                         the local level.’

                                         Client – Maribyrnong City Council
                                         Landscape Architect – Hassell Ltd
                                         Collaborative Artist – Karen Casey
                                         Civil, Structural and Electrical
                                         Engineering – Irwin Consult
                                         Principal Construction Contractor –
                                         Multipro Civil (Stage 1), J A Dodd (Stage 2)
                                         Concrete Seating Precaster – SVC
                                         Specialist Lighting – NDY Light
                                         Photography – Dianna Snape Photography

page 5 the public domain November 2008
                            Scarborough Beach, current home to the            shade sail, provides a comfortable, shaded
         Scarborough        national Surf Lifesaving Championships, is        viewing platform for national and international

         Beach – the new    arguably as iconic to Perth residents as Bondi
                            is to Sydneysiders.
                                                                              sporting and cultural events hosted at the
         jewel in Perth’s   Befitting its status and reputation, the          The beachfront location, together with the
                            beachfront has in recent years undergone          anticipated high usage of the site, made
         crown >            something of a rejuvenation, with concrete        concrete the natural choice for many of the
                            playing a key role in the process.                structural elements of the project.
                            Stage One of the Scarborough Environ Area         Curvilinear, limestone-coloured off-form
                            Strategy was completed in January 2007,           concrete retaining walls form the structure of
                            rejuvenating the declining public open space to   the new amphitheatre seating, complemented
                            create a new destination and event precinct,      with exposed aggregate, grey-coloured insitu
                            the centrepiece of which is a large, multi-       concrete paving.
                            function amphitheatre.                            The colour palette for the amphitheatre was
                            The new amphitheatre, sheltered by an elegant     influenced by nearby retaining walls

                                                                                                                                Photograph Blackwell & Associates
                                                                              Perth’s landmark Scarborough Beach is
                                                                              being reinvigorated and transformed
                                                                              under a new Urban Design Plan, the first
                                                                              stage of which successfully harnesses
                                                                              the plasticity of concrete in the creation
                                                                              of a magnificent public amphitheatre.

                                                                                                                                    Photograph Rob Frith (Acorn Photo Agency)
constructed from reconstituted limestone          continues along the beachfront in both             The success of the Stage One works at
blocks. On the surface, these limestone blocks    directions. The special premixed concrete used     Scarborough Beach is as much in the design
might have seemed an obvious choice to use        in the construction of this promenade,             as in the delivery. The new amphitheatre is a
for the amphitheatre. But according to Craig      incorporated 16-mm quartz aggregate,               popular and successful piece of public
Carpenter, of landscape architects Blackwell      ‘Cockburn Crème’ coloured cement and               infrastructure that perfectly meets the function
and Associates, the blocks couldn’t deliver the   sandstone oxide to give it its distinctive         for which it was built.
exacting, smooth radius for the curvilinear       limestone colouring.                               The use of concrete as the primary
seating walls as demanded by the design           This special exposed aggregate paving is           construction material ensures that this
team.                                             contrasted with areas of standard grey             functionality is matched by a durability and
The formwork was critical to the execution and    exposed aggregate paving, primarily within the     quality of finish that does absolute justice to
delivery of these precise concrete curves. It     amphitheatre, to provide variation and             the design team’s vision.
was Works Infrastructure that recommended         differentiate the role of these paths within the
the fabrication of custom-rolled mild steel       access hierarchy. Adjoining these paved areas      Client – City of Stirling, WA
reinforcement to produce the consistent radii     is a red asphalt bicycle path. The use of          Landscape Architect – Blackwell and
required across the project.                      different materials and colours delineates         Associates Pty Ltd
                                                  these areas and helps to give the promenade        Engineering Consultants – GHD Pty Ltd
“The steel formwork was a great success. We
                                                  a human scale.                                     Consulting Engineers
got a very clean, crisp off-form finish,”
                                                                                                     Principal Contractor – Works Infrastructure
Carpenter says.                                   The paving areas have been constructed with
                                                                                                     Concrete Seating Wall – Pinnacle Builders
The 400-mm-thick retaining walls are topped       a 32-Mpa concrete to allow for large vehicle       Concrete Paving – Westcon
with granite capping which injects another        access. The exposed aggregate finish of the
colour contrast to the overall design. The        paving particularly suits the sandy beachside
capping abuts the grey-coloured insitu            location, providing a durable, non-slip surface
concrete paving that is laid behind each          for beachgoers, the small aggregate size being
seating wall.                                     specifically chosen to be comfortable to bare
Behind and immediately adjoining the
amphitheatre is a public promenade that                                                              Photographs this page Blackwell & Associates

page 7 the public domain November 2008
Jacaranda Square – more
than just an everyday
experience >

Modular precast concrete furniture, in
combination with precast and insitu
walling, have helped create a stylish
yet functional space in the heart of
Sydney’s famous Olympic precinct.

Sydney Olympic Park at Homebush Bay will            “It’s a bit of an ironic nod to the Olympic       Inside this wall, Jacaranda Square features a
always be remembered as the ‘home’ of the           legacy,” says Sacha Coles, Director of ASPECT     large grassed area, dotted with eucalypts
2000 Games. But over the last eight years a         Studios, lead consultants of the design           along its northern edge, and a paved area
bold vision has been at play to ensure this         consortium – also comprising McGregor             along the southern perimeter that sweeps
expansive, much-loved site continues to evolve      Westlake Architects and Deuce Design – that       around the eastern and western edges of the
to meet the needs of the community – both as        won the competition to design the space.          enclosed site.
a centre of commerce and a home to                  “At the same time it says a lot about the         These two areas are separated by a curved,
thousands of Sydneysiders.                          function of the space. We were trying to create   off-white precast concrete wall, 400 mm high.
Jacaranda Square is a new public park space         something for everyday experiences, such as       This wall provides not just definition, but acts
situated to the east of Sydney Olympic Park         simply having a coffee or sitting under a tree.   as an informal seating bench for visitors.
Railway Station that is very much in keeping        Such opportunities have previously been hard      The paved area uses locally sourced recycled
with this vision.                                   to find at Sydney Olympic Park because of the     bricks, set in a random radial pattern. The use
It is part of a ‘green finger’ corridor that will   overall scale of the place as an event venue.     of these recycled bricks creates a link to the
run through future residential and commercial       “Our vision from day one was a beautifully        old brickworks that used to occupy the
development on the site, in line with the           designed and built project that was inherently    Homebush industrial site.
Sydney Olympic Park Authority’s 2030 master         simple and accessible.”                           Along the southern edge of Jacaranda Square,
plan for a vibrant, active and sustainable town     Concrete, both precast and insitu, has            a five-metre-high, 80-metre-long, steel-
centre.                                             provided some of the refined finishing and        framed canopy provides shading. This canopy
Jacaranda Square draws from the history of          definition that gives the space much of its       is clad in expanded metal mesh, powder-
the Homebush industrial site, combining man-        distinctive character.                            coated in calibrated greens to mirror the hues
made and natural elements to create a public        The entire space is bounded by a low insitu       and tones of the trees and grass on the
domain that is as beautiful as it is functional.    concrete wall, broken by a series of openings     opposite side of the Square.
The space has an alternative name that              to allow public access. The outside of this       The sweep of the canopy also picks up on the
perfectly sums up both its inspiration and          concrete wall is clad in glazed, pixellated       familiar curving roofline of the Sydney Olympic
purpose – the Everyday Stadium.                     bricks.                                           Park Railway Station just beyond.

page 8 the public domain November 2008
Under this canopy is one of the outstanding
design features of the site – the off-white,
modular precast concrete benches
manufactured by Sydney Precast.
According to Coles, these elements were
designed to exude a casual, inviting feel – akin
to a favourite lounge.
 “The robust and precise nature of concrete
makes it ideal for this application. At the same
time, the benches feature these beautiful
curved, soft edges that give them a real
human scale,” he says.
Visitors walking in from the Station can grab a
coffee from the kiosk situated in the south-
west corner of the Square before relaxing into
any one of the line of concrete lounges, or
sitting on the precast wall that separates the
                                                   Client – Sydney Olympic Park Authority
paved and grassed areas.
                                                   Design – ASPECT Studios in collaboration
It makes for a warm, comfortable experience        with McGregor Westlake Architects and Deuce
in a space that has enriched this iconic           Design
precinct.                                          Specialist Concrete Contractor (benches)
                                                   – Sydney Precast
                                                   Builders – Kane Constructions
                                                   Photography – Simon Wood Photography

page 9 the public domain November 2008
                          Simple, elegant precast concrete forms
                          punctuating an open grassy space have
                          helped transform this rundown inner
                          city park into a successful community

                                                                                                                       Photograph Ian Hobbs
                          A new life for Barcom Park >             Barcom Park, in Sydney’s Darlinghurst, is a
                                                                   prime example of successful urban

take-a breath
                                                                   renewal.The ‘pocket park’ – once a tired and
                                                                   under-utilised space next to St Vincent’s
                                                                   Private Hospital – has been revitalised via a
                                                                   landscape design that engages the
                                                                   surrounding built elements and the natural
                                                                   contours of the site to create an inviting
                                                                   sanctuary for local residents, hospital staff and
                                                                   The rejuvenation of Barcom Park came about
                                                                   from the closure of two bounding roads,
                                                                   effectively doubling the park’s size. Landscape
                                                                   architects Sue Barnsley Design were
                                                                   commissioned to reinvent the space, working
                                                                   closely with the local community and council
                                                                   to ensure the new design ticked all the right
                                                                   The result is a public precinct that draws light,
                                                                   soft lawns, seats and meet spaces into a new
                                                                   and engaging composition.
                                                                   Ten-metre road reservations have shrunk to a
                                                                   four-metre path along West Street and a
                                                                   shareway on Barcom Avenue, the latter
                                                                   featuring honed, concrete pavers that pick up
                                                                   the lustre of the adjoining terrazzo-clad
                                                                   hospital wall.
                                                                   A diagonal pathway crosses the centre of the
                                                                   park, cutting through the broad and gently
                                                                   falling grassed area to connect the perimeter
                                                                   walkways. At the mid point of this diagonal
 Photograph Eric Sieren

                                                                   pathway are two small, shaded seating pods –
                                                                   one either side of the path – featuring off-
                                                                   white, arc-shaped precast concrete benches.
                                                                   These benches deliberately draw the curve of
                                                                   the nearby hospital into the composition and
                                                                   language of the park.
           Photograph Eric Sieren

                                                                                                                                                                                          Photograph Ian Hobbs
                                    According to Sue Barnsley, concrete was            used, giving the surface a distinctive sparkle.    into the precast planks illuminates the
                                    elemental to the project.                          Concealed lighting under the benches creates       underside of the wall.
                                    “Concrete features heavily in the surrounding      an ethereal atmosphere at night, with the          The adjoining shareway on Barcom Avenue
                                    urban palette and we wanted to work with           seats appearing to glow and hover.                 features interlocking permeable concrete
                                    that,” she says.                                   At the bottom of the park, a warping, 22-          pavers, designed to improve the flow of
                                    “Moreover, because it’s only a small park the      metre-long, 700-mm-high precast concrete           stormwater run-off into the bio purification
                                    few elements that are in there needed to be        wall – part retaining wall, part seating bench –   basin.
                                    really high quality, and concrete offered a high   combines with a boardwalk of precast               Along the western side of the shareway,
                                    quality, robust finish.                            concrete planks.                                   adjoining the hospital wall, a series of
                                    “And from a design perspective, because it’s       This wall/boardwalk delineates the edge of the     ‘mounded islands’ of bamboo have been
                                    such a plastic material we could sculpt it to      open, grassy space. Below it is a specially        established. A border of off-white, off-form
                                    the shapes we wanted.”                             designed bio purification basin – a gully of       concrete provides a simple, elegant edging to
                                                                                       tangled rushes and bracken that captures the       distinguish these bamboo islands from the
                                    The benches were made from two separate                                                               pavers.
                                    moulds, each mould accommodating a                 first flush of stormwater from the site.
                                    different radius. One of the moulds was            The wall is made from two inverted moulds,         The new Barcom Park has a decidedly ‘green’
                                    formed to accept a curved insert of timber         again using a special off-white concrete mix       bent in more ways than one. Aside from the
                                    battens so as to introduce a contrast of           with quartz aggregate. The western end of the      obvious grassy spaces, the park features an
                                    materials. The legs of each bench were cast        wall is protected and enhanced by a ‘hood’ of      important hidden environmental initiative - a
                                    with the seats in a single pour. A special off-    bead blasted stainless steel. At this same end,    water capture and transfer system that
                                    white concrete mix with quartz aggregate was       a constellation of small, white LED lights set     recycles stormwater from the hospital to
                                                                                                                                          irrigate the space.
                                                                                                                                          All these features combine to make Barcom
Photograph Ian Hobbs

                                                                                                                                          Park an urban treasure, a space that works at
                                                                                                                                          a number of levels to breathe new life into
                                                                                                                                          inner city Darlinghurst.

                                                                                                                                          Client – City of Sydney
                                                                                                                                          Landscape Architect – Sue Barnsley Design
                                                                                                                                          Engineering Consultants – TLB Engineers
                                                                                                                                          Principal Contractor – Regal Innovations
                                                                                                                                          Specialist Concrete Subcontractor –
                                                                                                                                          Hanson Precast

                                    page 11 the public domain November 2008
                                                                                         Figure 1                                         Figure 2
            for Off–form
            Concrete >

            Formwork is critical to the final appearance of off-form                     The tolerance required may affect the selection of the material from
            concrete. This excerpt from CCAA’s publication, Guide to Off-                which the formwork is to be built, or govern its design. For example,
            form Concrete Finishes, looks at the key formwork factors that               steel formwork will enable tighter tolerances to be maintained.
            influence results.                                                           Absorbency. Variable absorbency of the form face will result in colour
            When it comes to the successful interpretation of a design idea in an        variation, possibly even dark staining of the surface. This is caused by
            off-form concrete finish, formwork is an important consideration.            changes in the water-cement ratio of the concrete at the surface.
            As fresh concrete is a plastic and malleable material that accurately        While this typically affects only the surface layer, a sufficient depth may
            reflects the shape, texture and finish of the surface against which it is    be affected such that subsequent surface treatments (eg tooling of the
            cast, it makes sense that the formwork is a key determinant in the final     concrete) may not remove the staining. The colour variations are usually
            appearance of the hardened surface.                                          most noticeable when adjacent form-face panels have different
            Any imperfection or inaccuracy in the formwork surface will be reflected     absorbency. Note that the absorbency of ‘new’ formwork changes after a
            in the off-form concrete finish. Form-face materials must therefore be       number of uses. This should be taken into consideration when replacing
            chosen both to achieve the required surface finish and, in conjunction       old or damaged formwork sheets with new ones. Also, the uniformity of
            with all the elements that support the form face, maintain tolerances and    the release agent coating can affect the absorbency of the form face.
            stability under all the loads imposed during erection and concreting, and    Watertightness. Loss of moisture and/or cement grout through lack of
            until the concrete has gained adequate strength.                             watertightness can lead not only to ragged edges and colour variations
            Failure to meet the required tolerance, stability and strength               from hydration staining, but also to other problems, notably
            requirements may lead to formwork failures such as bowing, warping           honeycombing.
            and misalignment, all of which will be reflected in the concrete finish.     Robustness. Formwork should be robust enough to withstand repeated
            As part of the formwork system, a number of materials can be used for        stripping, storing and erection to enable reuse.
            the form face against which the concrete is cast. In addition to its         Ease of stripping. Formwork should be easy to remove to avoid
            texture, the absorbency and watertightness of the form face will also        damage to the concrete surface and/or to the formwork itself.
            affect the appearance of the concrete cast against it.
                                                                                         Of the above properties, those with most impact on off-form finishes are
            Formwork qualities                                                           stiffness, absorbency and watertightness.
            The requirements for formwork include:                                       Many materials may be used for formwork. For small projects that
            Strength. All formwork components should be designed to carry the            involve a great deal of cutting and fitting, and therefore increased
            loads imposed on the formwork.                                               wastage, lower grade materials may be an option if the surface finish is
                                                                                         not critical.
            Stiffness. Formwork should not bow, bulge, sag or otherwise
            distort/deflect to an extent that the specified shape, tolerances or         For large projects, made-up elements such as table and wall forms
            appearance of the off-form surface cannot be achieved.                       could provide economies. The quality of the finish required and the
                                                                                         overall cost of the formwork are likely to be the principal determinants.
            While the metal support system shown in Figure 1 may provide a rigid
                                                                                         The following table provides a brief overview of the characteristics of the
            frame to restrain movement, the deflection (within tolerance) of the
                                                                                         most common formwork materials.
            more-flexible timber form-face material during concrete placement
            resulted in the off-form surface shown in Figure 2. Both the shape and       Figure 3                                         Figure 4
            tolerance requirements have been satisfied, but the visual quality of the
            surface has not met the expectation of a ‘flat’ surface. The deflection of
            the timber formwork system used for the walls in Figure 3 has resulted
            in the overall shape not being maintained.
            A lack of stiffness leading to deflection and movement during concrete
            placing and compaction may also contribute to a range of defects such
            as colour variation or a mottled appearance, sometimes referred to as
            aggregate transparency.
            Tolerance. The tolerances on formwork should generally be tighter than
            those desired in the finished concrete structure or element, and should
            ensure shape, size and cover to reinforcement.
            page 12 the public domain November 2008
Figure 5                       Figure 6                                        Figure 7                                         Figure 8

Common formwork materials                                                      appropriate release agent and application method may be critical to the
Timber              Form-face supports such as studs, bearers, joists          success of the project, affecting both the quality and colour of the
                    and whalers.                                               surface finish.

Steel               Formwork framing and in precast factories,                 As concrete will bond to most form surfaces, release agents are
                    particularly for repetitive work. (While strong and        primarily used to allow the formwork to be cleanly released from the
                    robust, requires some standardisation and multiple         concrete. Equally important is their role in protecting and extending the
                    reuses to warrant the cost.)                               life of the formwork, enabling a good quality off-form finish to be
                                                                               maintained with each reuse of the formwork.
Coated plywood      Slabs, columns and beams. (Readily worked and
                    capable of multiple reuses.)                               Release agents can also affect the colour of the surface and the
                                                                               adhesion of subsequent finishes or coatings.
Cardboard           Column forms, edge forms.
                    Normally for one-off use only.                             There are two main categories of release agent: barrier and reactive.
                                                                               Barrier compounds form a physical barrier between the concrete and
Glass reinforced    Permanent formwork (where it provides a decorative
                                                                               formwork, while reactive compounds not only form a barrier, but also
cement (GRC)        finish) or as the mould for intricate shapes
                                                                               contain ingredients that react with the calcium hydroxide in the concrete
or plastic          (particularly precast elements).
                                                                               to form a chemically inert metallic soap that helps minimise adhesion of
Concrete            As permanent formwork for standard elements or             the form, keeps the form clean, and thus extends its life.
                    components produced in precast concrete factories.
                                                                               Barrier products commonly used include water-based or solvent-based
Rubber, silicone,   Formliners providing intricate effects and decorative      petroleum products, paraffin-based materials, or soap-type release
thermoplastic       finishes. (Most materials are capable of multiple          agents. They vary in ease of application and tend to build up on the form
and polystyrene     reuses.)                                                   surface, which will therefore require regular cleaning.

The use of permanent formwork (ie formwork which is left in place)             Reactive release agents generally contain a small percentage of fatty
could minimise subsequent finishing operations. While precast concrete         acids. They can be either vegetable oils, or more commonly, petroleum-
and GRC are commonly used for permanent formwork, materials such               based materials. They allow easy release of forms and assist with
as fibre cement sheet, polystyrene (Figure 4), and reinforced plaster          minimising blowholes. As they will react with metals such as brass,
(Figure 5) are also used in various concrete walling systems.                  bronze, aluminium and steel, the use of appropriate application
                                                                               (spraying) equipment is essential.
Recent developments have seen new materials used in formwork
systems and the incorporation of various surface textures ranging from         With the variety of products on the market, each contributing differently
rock faced to brick and block patterns Figure 6.                               to the off-form finish, care in the selection of a release agent is required.
                                                                               Manufacturers’ recommendations should be sought for specific projects.
For some elements in a structure, it will often not be necessary to
provide the same quality of finish on all faces. Critical faces should be      If colour control has been specified, once a release agent has been
identified and perhaps be specified as a higher class of finish, say Class     chosen, it should not be changed during the course of the work without
2, with other less critical parts of the structure that can not be viewed at   due consideration to the effects on colour and finish. Figure 7 shows the
close range having a Class 3 finish. In this way, formwork materials can       colour variation possible from a variety of different release agents, and
be reused for lower quality (less critical) faces.                             Figure 8 the effect of changing a release agent midway through a
                                                                               Test panels built prior to construction provide the best method for
All formwork design should comply with the provisions of AS 3610. The
                                                                               assessing the suitability of a release agent for the given application.
formwork drawings should show the pattern of the form face, if any, and
typical joints between formwork panels.                                        Like every aspect of construction, the successful execution of off-form
                                                                               concrete elements requires skill and care.
Careful detailing of such joints is critical to the success of off-form
finishes. For example, all control and construction joints on vertical         Understanding the nature of different formwork materials and systems,
surfaces should either be boldly expressed or disguised.                       their strengths and limitations, and the way they interact with the
                                                                               materials and environments with which they come into contact, will help
Release Agents                                                                 ensure you achieve the level of finish you expect.
While generally regarded as a minor item, the selection of an

page 13 the public domain November 2008
                        SYDNEY OFFICE:                   ADELAIDE OFFICE:                                 EDITOR:

                        Level 6, 504 Pacific Highway     Greenhill Executive Suites                       Carol Moir
                        St Leonards NSW Australia 2065   213 Greenhill Road                               CONTRIBUTORS
                        POSTAL ADDRESS:                  Eastwood SA 5063                                 Komal Krishna
                        Locked Bag 2010                  POSTAL ADDRESS:                                  John Nichols
                        St Leonards NSW 1590             PO Box 229
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                        TELEPHONE: (61 7) 3831 3288      Henley Beach SA 5022                             industries in Australia to provide information on the
                        FACSIMILE: (61 7) 3839 6005      TELEPHONE: (61 8) 8243 2505                      many uses of cement and concrete. This publication is
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                        repose                                                                            ISSN 1833-2870
issue 8 november 2008

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