It is often found that a beautiful and painstakingly designed architectural project involving black coloured concrete fades away and loses its intended aesthetic.

This important issue is frequently occurring on a wide variety of architectural applications, whether it be an integral cool charcoal black finish effect for precast concrete wall panels on an exterior building, a deep strong black in a retaining wall or a subtle mid tone grey/black in concrete flooring, perhaps made with off-white cement to show colour subtlety, all of which are ‘on-trend’ in both commercial and residential projects.

Unfortunately, architects are at risk of discovering the truth about certain black colouring pigments for concrete far too late!  When their clients complain that concrete at their home or business premises is losing its pristine blackness…. as the ‘colouring is fading away.’  Their clients had not been forewarned about what they would rightly believe to have been a predictable permanent colour outcome their outrage can obviously be extreme.

If the architect on behalf of his/her client then seeks out rectification and restoration of the desired colour which can probably involve the complete removal and replacement of the problem concrete, the costs can be high.

A possible question by the client could then be put to the architect.  Shouldn’t you have known better?

What you need to know now!

The unfortunate circumstances mentioned above – along with potential damage to your professional reputation - can be avoided by arming yourself with the necessary knowledge regarding best practice of colouring technology for concrete and mortars.

Here are a few key basics:

For black shades in concretes, use only permanent mineral oxide black pigments NOT carbon black pigments. Why?

Carbon black coloured concrete leaves, disappears and fades when rained upon plus other natural weathering effects.

Carbon black, the pigment found in soot and charcoal, is an economical black colourant for vehicle tyres with high tinting strength. However it can leach out of concrete exposed to repeated wet/dry cycles unless the concrete is well sealed.  However clear sealers are NOT UV stable and permanent.  When they are eventually destroyed the pigment’s departing/fading action can take place.

Tests have proven carbon black is inferior to iron oxide mineral black pigments

World leading chemical manufacturers Lanxess Corporation and the Bayferrox® Group, Germany’s Federal Institute for Material Research and Testing, as well as Australia’s Ability Building Colours, have conducted tests of concrete samples coloured black using both carbon black and iron oxide black pigments.

The results of all the tests found that concrete samples pigmented with carbon black fade significantly on exposure to weathering, while only a very slight change in shade (usually atmospheric dirt) is observed in those samples coloured with Bayferrox® and abilox® iron oxide pigments.

Does the colouring pigment you have chosen conform to international standards and best practice?

Carbon blacks are made from crude oil and are therefore chemically organic, non-permanent (and that being so), do not meet ASTM E979, the International Standard Specification for Pigments for Making Integrally Coloured Concrete.  This standard covers the basic requirements for white and colouring pigments in powder form to be used as admixtures mixed into concrete for the purpose of producing integrally coloured concrete. 

Liquid Pigments:

It has also been suggested that some liquid colours on the market often imported and used to colour some brands of pre-mixed concrete may contain carbon black. 

Perhaps it’s safer to use and specify only proven mineral oxide powder colours.

A proven solution - abilox® Mineral Oxide Powder Colours:

With the facts outlined above, it’s clear to see carbon black pigments are definitely prone to fade and disappear. The best advice is to specify and use a permanent mineral iron oxide powder black.

That’s why for absolutely permanent, non-fading integrally coloured concrete, it’s always safest to specify only a trusted name for dispersible powder colours in Australia - abilox®.

Contact Ability Building Colours for more information.