When Jude and Graham Dobson Renovated their Mt Eden Home, they wanted a hard-wearing and attractive floor to accommodate a growing family, two dogs and an often hectic lifestyle. They chose a tile cut and colour blended concrete floor which as well as being attractive and unique, performs to all their requirements. Contractors: Atlas Concrete Ltd, Holloway Builders and Oxide Distributing Co. Ltd.

45 Paul Mathews Ave, Albany shows innovative thinking by Dave Mc Alpine of the Kea Property Group and design by Ignite Architects to incorporate a stunning pre-colour tilt slab concrete wall as a feature of this office/warehouse development. Contractors: W. Stevenson & Sons, AVOCA construction, Oxide Distributing Co Ltd.

The Colouring of Concrete - Instructions for Processing

Tinting Strength of Pigments

One brand of pigment is not the same as another. Two pigments identical in appearance may have a completely different yield. The decisive property in the use of a pigment for colouring concrete is tinting strength. A sample mix prepared under practical conditions can provide reliable information on this.

Pigment Loading and Colour Effect

You certainly do not want to throw away money not even for such a good idea as decorating concrete by colouring it with inorganic pigments. Knowing the optimum pigment loading for concrete helps to save money because you can then be certain that no more pigment is being used than is absolutely necessary.

With increasing pigment loading, the colour intensity moves towards saturation point. Adding more pigment at this point does not significantly deepen the shade.

The saturation point lies between approximately 5% - 8% calculated on the weight of the cement in the mix. However a good depth of colour can be achieved at 4%.

The normal ready mix concrete strength is 6 x 40kg bags of cement per cubic metre of concrete. 4% of this equates to approximately 9kg of oxide. Mortar on the other hand with its higher cement content requires more pigment. It is important to remember that PIGMENT ADDITION RELATES TO THE AMOUNT OF CEMENT IN THE MIX AND NOTHING ELSE. A rough guide is to use approximately 1.5kg of oxide per 40kg bag of cement.

Natural Colour of the Cement and Colour Effect

Grey has a subduing effect on all colours, no matter where they are. This is why it is not possible to colour concrete made with normal grey cement as brightly as concrete containing white cement. The gain in colour purity obtained by using white cement depends, however, on which pigment is added. In the case of black there is virtually no difference between concrete made of white cement and one made of grey cement. With dark brown, red and burnt umber the difference is small while it is considerable with yellow, marigold, green and blue.

Water Addition and Strength of Concrete.

Darker, less bright colours will be obtained with concrete of lower water/cement ratio that has been compacted by compression than concrete of higher water/cement ratio such as vibrated concrete.

The lower the water/cement ratio of a concrete, the greater its strength, providing the concrete is not very dry indeed.

Also as the water/cement ratio increases, so the shade of the concrete where pigment has been added becomes lighter. It is important then to maintain a consistent water/cement ratio.

Fading of Coloured Concrete

Chemical reactions within concrete itself can reduce colour brightness. It is also important that the concrete is not allowed to dry too quickly. As the concrete cures, especially in hot summer weather, slow the hardening process down by keeping water on the surface. The inorganic pigments supplied by Bayer are manufactures for optimum resistance to the weathering effects of nature and will retain good colour stability during the normal life of concrete products that they are used for.

Efflorescene

Efflorescene is the scourge of all concrete manufacturing particularly when colour is involved and particularly high demands are made on the appearance of the concrete. It is, however, a normal, temporary problem in concrete. Basically it is the build up of lime (Calcium Carbonate) on the surface of the concrete as it cures, leaving a powdery whiteness in patches or uniformly overall.

Efflorescene will disappear in the course of time, normally 18 months to two years of weathered naturally.

The length of the process depends on the climatic conditions and on the amount of traffic the concrete has to bear.

If this natural process takes too long, remove the efflorescene by treating the surface with dilute acid in the following way:-
Soak the concrete surface thoroughly with water and then spray with a diluted acid solution (e.g. diluted Spirits of Salts - 1 part Spirits of Salts to 3 parts water). Use a common garden spray pump and wear protective clothes, acid-resistant shoes, protective gloves and safety goggles. Apply the treatment carefully to avoid a spotty result. Gently scrub with a soft broom during treatment to ensure good penetration and uniform coverage. After a short time rinse the concrete thoroughly with flowing water.

Blending of Oxides for Different Colour Shades

Oxides, like paints, can be mixed to provide a variety of colours, as seen in the photos throughout this website. We can supply 'shot blends', i.e. small pre-mixed blends of oxides to mortar and plaster contractors to standardise colours and eliminate the often difficult task of preparing blends on site.

Grout Bleed

Please note that floors which are tile cut for grouting SHOULD BE SEALED with concrete sealer before grouting to prevent grout bleed into the coloured concrete.

The Advantages of Measured Quantities of Oxides

We can supply measured quantities of Bayferrox Oxides to the readymix concrete industry in 20 litre plastic buckets. This applies to standard grades, G & C grades or blends. The advantage of the G & C grades is that they flow when being administered, causing less dust nuisance. There is also no need for plant staff to measure out quantities for dosage as this has already been carried out by us.