Uniform, striking, and unfading colour is the ultimate goal anyone attempting to colour their concrete, whether they’re using an oxide pigmentation, coating or stain to do so.
While coatings and stains can provide a great coloured concrete finish, they are more generally an after-pour thought or for those refreshing their concrete years after it was laid. Mineral oxide pigments on the other hand are a more permanent option and are added to concrete either at the mixing stage or on top of the concrete after it is placed and screeded.
While becoming an increasingly available option, not all oxide pigments are the same and there are a number of considerations an architect or designer should mull over before specifying them.
INTEGRAL COLOUR OR DRY-SHAKE?
As mentioned, mineral oxide pigments are added to concrete either at the mixing stage as a ‘through-mix’ or in a ‘dry shake’ method, which sees oxide pigment powders thrown onto the surface after compaction, screeding and bleeding before final finishing by trowelling.
By its very nature, the dry-shake method leaves more room for contractor-error as it requires trade skills such as floating, edge-tooling and trowelling[i]. Additionally, because it’s a superficial finish, is also more likely to need repairing after imminent surface wear.
Through colouring on the other hand is added into the total concrete mix and achieves full depth colouring throughout the entire material, so even if surface abrasion occurs, the colour will not wear away[ii].
Achieving desirable through-colour full-depth colouring is therefore less dependent on trade-skills than other methods and more dependent on the quality of products used and a contractor’s ability to follow instructions provided by the specifier.
CHOOSING AND MIXING THE CEMENT
Consistent and permanent concrete colouration is built on a “cement foundation”, literally and figuratively, and a particular brand, type and colour of cement will result in a different finish.
Whatever the cement colour chosen – grey, off-white or white, it is wise to ensure that it comes from a single source of manufacture and that you speak with your pigment manufacturer to ensure you get the right colour with the right cement chosen.
Even the highest quality oxide colouring pigments such as abilox® from Ability Building Colours must be thoroughly mixed and dispersed in the material being coloured.
ABILITY’S GUIDE TO THE PERFECT MIX
A low water content with a high cementitious binder mix
Special class 32MP(S32 grade), compressive strength concrete
High quality fine synthetic oxide colouring agent
Eight minutes minimum mixing time at 20 rpm mixing speed (pre-mixed concrete transit truck or at the supplier’s mixing plant)
abilox® chemically inorganic mineral oxide colour particles are so fine they disperse readily in a cement-based mix or in resin media used to bind paints/colouring sealers etc. with the provision of adequate mixing. Correctly mixed and dispersed pigment particles result in the maximum intensity of colouration which saves costs and results in non-varying, uniform colouration.
Inorganic mineral oxide colour technology has come 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.
For more information on how to achieve the best coloured concrete and mortar finish click here to download this free white paper “The correct way to colour concrete and mortar materials”