The correct way to colour

concrete and mortar materials

Image of Geelong Library, Geelong, VIctoria. Architects: ARM Architecure Pty Ltd

www.abilityproducts.com.au
Introduction
Consistent, striking, and unfading—these are the pivotal measures of any coloured concrete or mortar project whether
it’s achieved with an oxide pigmentation, coating or staining process.

However, achieving uniform and permanent colouration for concrete and mortar isn’t as simple as specifying an oxide,
coating or chemical stain and then hoping the contractors do use correct mixing, application and curing procedures.
Consistency and uniformity of all procedures, proportions and processes is essential, and when it comes to colouring
concrete or mortar it is probably best that an architect or designer considers these at the material specification stage.

Make it permanent
Coatings and stains can provide a great coloured concrete finish, but they are more
generally an after-pour thought and for those wishing to refresh their concrete years
after it was laid or for those requiring a “quick fix”. Mineral oxide pigments on the
other hand are added to concrete either at the mixing stage as a ‘through-mix’ or in a
‘dry shake’ surface colouring method after the concrete is placed and screeded.

By its very nature, the dry-shake method, which sees oxide pigment powders
thrown onto the surface after compaction, screeding and bleeding, leaves
more room for contractor-error as it requires trade skills such as floating,
edge-tooling and trowelling i. Additionally, because it is a superficial finish, it is
also more likely to need repairing after imminent surface wear.

As the name suggests, the advantage of through colouring to full depth is that the
colour extends throughout the entire material, so even if surface abrasion occurs, the
colour will not wear awayii. But while they may not fade there are a few things that affect
the endurance and “look” of through-coloured concrete and concrete products:

1. Time of colour assessment: It takes 28 days for Portland cement to

achieve its final, true colour – with or without pigmentation

2. Formation of laitance: For effective integral colouration - particularly at

the surface, it is mandatory to specify, use, and place, only non-bleeding
concrete - so that after hardening a weak surface of laitance does not occur.

3. Formation of efflorescence: The white ‘frosty’ looking salt bloom of

efflorescence masks the true colouring effect of oxide pigmentation. It is
difficult to remove so be sure to use a suitable strength grade of pre-mixed
concrete with a relatively low water/cement ratio.

4. Poor abrasion resistance: An under-strength hardened concrete batch will have

low wear and abrasion resistance and could see the removal by wear of the
pigmented hardened cementitious paste binder ‘glue’ and the pigment particles
with it, at the surface. High wear resistance is obtained by using concrete of
an adequate strength grade containing the optimum amount of cementitious
binding material per m³ of concrete, and the use of correct site processing
procedures and practices of – particularly the procedure of curing – is also
considered essential so kindly seek assistance from the pigment supplier.

Achieving desirable through-colour or full-depth colouring is therefore less

dependent on trade-skills than other methods and more dependent on the quality of
products used and an ability to follow instructions provided by the specifier.

Companies such as Ability Building Colours, who supply the industry leading
abilox® mineral oxide colours can provide knowledge and recommendations
on proper mixing techniques and the processing of concrete and mortars from
qualified industry sources, especially the all-important curing process.

They can also recommend ways of wording architects and engineers specifications
for contractors so that penalties could apply if important processes such as curing
and correct mixing times are not carried out properly.
Make it striking
Consistent and permanent concrete colouration is built on Even the highest quality oxide colouring pigments such
a “cement foundation”, literally and figuratively, and when as abilox® must be thoroughly mixed and dispersed in the
looking to specify full depth coloured concrete products, the material being coloured.
effect different mixes and their consistencies or “slumps”
can have on colouring agents should not be understated. All brands and types of inorganic mineral oxide colouring
pigments are exceptionally UV resistant but some inferior
A particular brand, type and colour of cement will result in varieties may not be uniform in colour from batch to batch.
different colours and therefore enforces the need to specify They may also be very dull in the shade, difficult to disperse
colouring admixture doses specific to a concrete batch. or they may not be of satisfactory colouring strength for a
Whatever the cement colour – grey, off-white or white—chosen, particular colouring purpose in relationship to their costiii.
it is wise to ensure that it comes from a single source of
manufacture and that you speak with your pigment manufacturer Ability Building Colours provides free consultation on
to ensure you get the right colour with the right cement. technical issues and can provide free hardened mortar/
concrete sample “biscuits” for each of their abilox® mineral
oxide colours at different dose rates.

Make it vibrant
Chemically inorganic abilox® mineral oxide colour particles THE PERFECT MIX
are so fine they disperse readily in a cement-based mix or
in resin media used in paints/sealants etc. with the provision • A low mix water content with high cementitious binder mix
of adequate mixing. Correctly mixed and dispersed pigment
particles result in the maximum intensity of colouration which • Special Class 32MPa compressive strength @28 days
saves costs and results in non-varying, uniform colouration. (S32 grade) concrete

As the name suggests, full-depth colouring agents change • High quality synthetic oxide colouring agent
the colour of the whole mix meaning that even after
significant wear the concrete/mortar will remain the same • Eight minutes minimum mixing time at 20 rpm mixing
colour. Inorganic mineral oxide colour technology has come speed (pre-mixed concrete transit truck)
leaps and bounds of late and the choices to be made from
the colours available are truly astounding. abilox® oxide
colours are provided in a standard range of 60 colour
shades plus Ability can provide any custom colour required.

THE SCOPE OF OXIDE PIGMENTATION—THE COLOURING OF

• pre-mixed reinforced concrete • site-mixed reinforced concrete
• masonry and rendering mortars • pre-cast reinforced concrete wall panels
• FRC-fibre reinforced thin lightweight concrete panels
• concrete roofing tiles, masonry and pavers • and more

Conclusion
When used correctly, colouring oxide pigmentation
products are the most effective way to achieve consistent,
vibrant, and unfading coloured concrete and coloured
concrete products, but as much as we wish it wasn’t the
case, even reputable products like abilox® from Ability
Building Colours can be used incorrectly.

Once you’ve chosen the correct product, controlling all the

procedures, proportions and processes is the difficult part
of colouring concrete and mortar products and should be
considered by the architect or his/her engineer at the very
beginning of the project. Consider also putting in place
clauses in contractor specifications so that the cost burdens
associated with incorrect procedure does not fall on you.
REFERENCES
i
http://www.elvingroup.com.au/wp-content/uploads/2014/07/concrete_basics.pdf
ii
http://www.concretenetwork.com/products-integral-color/advantages.html
iii
http://www.abilityproducts.com.au/pdfs/abilox_Fortuitous_Facts.pdf