1'Tis document
contains
pages] ARCHITECTURAL IN-SITUCONCRETE - PART 2
Architectural Hardscape
Coloured surface hardeners
and imprinting concrete
David Bennett, Director, David Bennett Associates
A application there should be no bleed mendedfor increasing any colour intensi-
rchitectural hardscape is a generic
term for paved frontages, drive- water on the concrete surface. The final ty. When used on toppings of 50 miii or
ways, car park zones, pedestrian shake is then applied and the surface float- less, the timing and finishing techniques
ways, in fact any area which is not part of ed before trowelling. Excessive trowelling will be very sensitiveto ambient tempera-
the soft landscape of a project - plants, of the surface must be avoided to prevent tures and air humidity. For exposed
trees, shrubs and grassed areas. Architec- colourburns and surfaceblemishes. aggregate finishes and deep broom finish-
tural hardscape is brick payers, stone flags, A small quantity of material should be es, dry- shake is not recommended.
marble slabs and slate tiles, precast con- withheld for touching up any non-uni-
crete blocks and more recently imprinting form or patchy area as necessary. Water Plain coloured surfaces
and textured in-situ concrete. It is an must not be added or sprinkled onto the After the dry-shake colour has been
option that offering greater versatility and surface at any stage ofthe work. applied, it should be covered with a cur-
economy of construction than traditional Dry-shake materials can be specified for ing coat ofcolour wax acrylic emulsion as
hardscape materials. both large and small areas. They are avail- soon as the concrete surface has begun to
As building developers and home own- able in 16 standard colours, eight designer set. There should be no bleed water or
ers become increasinglyaware of the val- colours and special colours matched to sheen on the surface and the concrete
ue of attractive landscaping, more of the customer requirements. Because they arc should be firm enough to walk on (but
building budget will be spent on architec- applied to the surface ofthe concrete they not actually walked on).
tural hardscape. Not only will it help to are more intense in colourand shade than The curing coat is matched to the final
increaseproperty value, it enhances build- integrally coloured concrete. For most colour of the concrete and is spray-
ing quality and helps to create a better liv- commercial, industrial and residential applied undiluted, in one even coat. The
ing and working environment. applications, a minimum dosage of curing coat will appear to be lighter than
This article explores the range of 3 kg/m2 provides a durable and hardwear- the fresh concrete colour at first, because
colours and finishes that can be applied to ing surface. Lighter colours may need it is matched to the lighter colour of the
in-situ concrete using dry-shake colour 4 kg/m2, a dose which is also recom— hardened concrete.
hardeners and imprintingtechniques.
luteusave colour ofdry shake 'tile red' usedfor a car shou'roau,floor contrasts well u'ith the pain tn'oek on the car
Dry-shake
Dry-shake colour hardeners are ready-to-
use products for colouringand hardening
the surface of plain concretes.., be they
roads, patios, pavements or drives. They
are dry-batched in 30 kg bags, and should
contain a blend of light-fast colour pig-
ment, Portland cement, surface hardener
and fine aggregate.
Dry—shake colour is applied to the sur-
face of freshly cast concrete, after com-
pacting and floating the concrete to level.
The first application or shake will con-
sume about two-thirdsof the dosage with
the remainder held back for the final
shake and touch up.
The material is broadcast over the fresh
concrete surface and then floated into the
concrete surface in a circular motion
using hand tools or mechanical methods.
It must not be trowelled. At the time of
September/October /992 CONCRETE
On no account must water, polythene
sheets, covering paper or damp hessian be
used to cure the concrete. These will
impair the colourand maylead to perma-
nent surface blemishes.
The cured surface should not be
walked on for at least eight hours. A sec-
ond and final coat is sometimes applied,
to seal thesurface completely.
For retail stores which require a glossy
non—slip surface finish, a final coat of
colour wax emulsion is recommended in
place of the acrylic coat. After the first
coat of colour wax has dried, the final
coat is applied and then huffed with a
floor polisher to leave a clean, non-slip
surface.
Imprinting and texturing
Imprinting and texturing are popular
methods of finishingthe fresh concrete
surface. There are a wide vanety of tex- Dry-shake colour-conditionedconcrete continued imaginatively to create apiazza ofoutstandingbeauty andquality
tures and finishes that can be given to in i/ic (iSA
coloured concrete surfaces - from simple ible, two tinker and two single block exact dosage rate can be deterniined after
broom and roller textures to intricate mats. conducted a trial on a sample area.
brick, stone and cobblestone simulations Disney Herringbone Brick, a 4 x 8 in. During impnnting work, a portion of
or customised pattern using imprinting brick with thin joints and an orange peel the colour in the antiquing agent
tools. finish, is ideal for pedestrian ways and becomes embedded in the surface of the
Imprinting tools consist ofa set ofngid paths. An average set comprises six double hardening concrete. When the surface is
or flexible patterned moulds, made from rigid mats, one flexible mat and three sin- washed the following morning to remove
steel or polyurethane, which are indented gle brick mats. excess release agent, a variegated and
into fresh concrete to create brick, stone, Yorkstone Slate has varying stone sizes mottledcolour is left on the concrete sur-
cobbles, tile and even wooden board fin- with a light stone texture and quarter- face. The final colour varies between the
ish. inch joints. An average set contains 16 colourofthe base concrete, the antiquing
Imprinting tools can be purchased for rectangular and square mats, each ranging colour, and a combination ofboth.
next to nothing or for a small fortune in size and slate textures. Since the antiquing agent is mechani-
depending on the quality of the material The concrete to be imprinted is first cally bonded to the concrete surface, it
and the sophistication of the pattern finished with a dry-shake colour and must be sealed and maintained to preserve
required. For domestic work in back gar- trowelled as for a plain finish. The surface its appearance. Usually, a clear acry]ic
dens and small areas, inexpensive moulds is usually given a single antiquing colour coating is applied after the excess has been
(which are usually machine-cut) would coat to give the surface a weathered or washed offby high-pressurejetting.
not show up many of the imperfections antique look to closely match the colour Timing of the imprintingoperation is
and limitations of their imprinted pat- of natural materials. The antiquing coat is critical. The surface can be imprinted as
terns. For quality work with the authentic sprinkled nn to the finished surface, but soon as it is finn enough to walk on. Plan
look of stone or brick, a full set of rigid not floated or trowelled in. The imprint- the work starting from the end that may
and flexible moulds patterned from the ing work begins immediately this is com- be more restricted for access. Co—ordinate
onginal material should be used. pleted. the sets of patterns in order ofimprinting
Some examples of imprinting tool sets The antiquing agent is a fine powder beforehand; there can be as many as ten
and popular stone patterns are described consisting of a colouringagent and bond pieces in the better quality sets.
below: breaker. The bond breaker helps prevent The lead imprinting pattern is placed
European Cobblestonein 3 x 6 in. and 4.5 the imprintingtools from sticking to and on the concrete surface and then tamped
x 7 in. stone sizes, in fan configuration disturbing the fragile concrete surface. to impress the pattern into the concrete.
with a lightly textured granite face, The average dosage rate for antiquing The next pattern is aligned adjacent to the
requires a set of seven ngid, two flexible agent is usually 4 to 6 kg/m2. A more first and then tamped. Imprinting contin-
and two tinker mats. A tinker mat is a ues until the surface area is fully covered.
small mould for filling in gaps, awkward Imprinted concrete in 'Old Belgium Block' Careful watch of the weather, drying sun
corners and so forth. and wind, and threat of rain is critical to
Fieldstone, moulded from large pitted success. If it rains during dry—shake or
rocks found in fields across mid-west imprinting operations, the surface colour
USA, is good for pool decks, embank- and finish may be impaired.
ments and bridle pathways. An average set
of tools comprises six rigid, one flexible Practical guidelines for
and two tinker mats. imprinting
Old Belgium Block is an authentic pat- Good concrete practice and preparation
tern of actual cobblestone streets in of the formation are the key to successful
Europe with heavy surface texture of imprintedhardscape.
fractured granite and wide joints. An Forslabs with vehicular access or which
average set consists of four rigid, two flex- support an industrial floor load, an engi-
CONCRETE September/October 1992
neering design would be required to
determine the depth of slab. Typical slab
depth would range from 150 to 250 mm,
reinforced or unremforced. Guidance giv-
en in TR.34 "Concreteindustrial ground
floors" and BS 8110 should be referred
to.
Generally for domestic projects or
commercial projects with paths and
pedestrian areas and lightly trafficked
driveways, a 75-100 mm reinforced or
unreinforced concrete slab would be ade-
quate, providedthe sub-base was properly
prepared. Some practical guidance for the
construction ofdomestic projects is given
below:
1. For unreinforced slabs a minimum
cement content of 250 kg/rn3 is pre-
scribed.
2. For reinforced slabs a minimum
cement content of 300 kg/rn3 is
required.
3. If the slab is subject to freeze/thaw
cycles, an air—entrained concrete
should be considered.
4. Provide controljoints to permit dif-
ferential movement due to drying
shrinkage and thermal gradients, if
they are critical. Where the slab
dimension is less than 6m in either
direction, there will be little risk of
shrinkage cracking. lithe slab dimen-
sion in any direction is greater than
6 m, drying shrinkage cracks can be Tastefullyrestored streetin Holland, recreated with imprintedconcrete
controlled by incorporating a layer of
steel fabric or by introducing control judgment of the weather and other tracts, at competitive prices. To put a true
joints. site factors. Placing too large a mass perspective on the cost benefits and
5. Construct slabs in narrow bays to of concrete on a hot or windy day intrinsic quality of this method of work,
help maintain accurate levels and may cause the surface to set faster the example from Disney World in Flori-
contain the work in manageable than it can be finished. da is worth summarising. The "Magic
areas. Typical bay widths of up to Depending on the size and scope of a Kingdom" theme park with its miles of
5 m are acceptable. The coverage project, imprinting contracts should be roads and pathways presented an opportu-
area for imprinting for one man is awarded accordingly. For large areas, nity to Disney's architects to compare the
about 75 to 100 m2 per day. commercial work and domestic drive- cost and finished quality ofnatural materi-
6. to
Beginby applying dry-shake edges ways, it is recommended that established als, such as stone and brick payers, with
and finish these areas first as they companies like Architectural Hardscape of the imprinted concrete equivalent. The
tend to dry faster. Broadcast dry- Coalville, Leicester be approached. Their cost savings, quality of finish and ease of
shake and antiquing agentdownwind last major project was to manage the construction gave imprinting an over-
to avoid inhalation. Protect sur- imprinted work for Euro-Disney. whelming advantage over natural materi-
roundingareas from accidental stain- als. The final designs called in 27
ing or contamination by dry-shake or Disney in England? customised colours and as many imprint-
antiquing agent. Imprinted concrete is popular in the US ed patterns.
7. For hand-tamped concrete,a 75 mm because it is a durable, versatile, cost— To date it has still maintained its beauty
slump concrete is suitable. For con- effective product. Quite a number of and continues to enhance the appearance
crete that is to be vibrated by poker imprinting companies have burgeoned of such an imaginative enterprise. Confi-
and/or beam compactor, a slump of and establisheda successfulbusiness in the dent of the trackrecord ofconcrete hard-
50 mm is suitable. market. In the UK, imprinting companies scape in Florida, Euro-Disney specified
8. Maintain a low water/cementratio — and their licensees have been operating the same range of colours and imprinted
at orbelow 0.5. for a few years now, many working from work for the Paris themepark.
9. To prevent moisture and water a garage or garden shed offering imprint- Dry-shake colour hardeners and
vapour from condensing and accu- ed concrete to the domestic market. imprinted concrete are thus limited only
mulating in the slab for interiorfloors However, there are a growing number by a designer's imagination and the skills
and driveways, a polythene sheet or of well managed companies who can of the contractor: the process and end
damp-proofmembrane should be undertake large contracts for retail stores, product are proven. With architects
laid on the sub-base before concret- petrol stations, public authorities and working in close co-operation with the
ing. commercial developments. They offer the established imprinted contractors, what
10. Timing, finishing and imprinting of client the quality, integrity and perfor- can be seen in Florida and Euro-Disney
concrete require experience and mance standards required for such con- can now be realisedanywhere in England.
18 September/October 1992 CONCRETE
