To the average individual, the term “concrete” conjures up images of cold, sterile, and grey. It’s easy to see why. Typically, the concrete encountered is a utilitarian product for pathways or bridges, with function and expense taking precedence over aesthetics.

However, growing interest in decorative concrete is challenging this notion, turning it from a cold mass buried beneath the ground into enticing decorative surfaces to show off to visitors. As interest in personalized concrete increases, so does the demand for a wider range of colours.

Colouring Concrete

The colour of the pigment, the form of mortar, the amount and colour of the aggregate, the moisture content, the mixing process, and the finish methods all contribute to the overall look of the decorated concrete surface. Cement colour is the starting point and deciding factor in the colour spectrum that can be achieved.

Cement

White cement allows for a wider variety of colour options and should be used for bright and vivid colours. White cement also produces better colour reproducibility and quality. White cement and the lightest aggregates should be used for full brightness, especially in light pastel shades.

Grey cements can differ significantly between manufacturers and batch to batch, and green undertones can alter the desired colour’s final appearance. Since grey cement contains higher levels of iron and other impurities, the colour palette is limited to subdued earthy tones.

Aggregates

White cement allows for a wider variety when it comes to choosing different concrete shades. White cement also produces better colour reproducibility and quality. White cement and the lightest aggregates will be used for full brightness, especially in light pastel shades.

Grey cements can differ significantly between manufacturers and batch to batch, and green themes can alter the desired colour’s ultimate appearance. Since grey cement contains higher levels of iron and other impurities, the colour palette is limited to subdued earthy tones.

Water

Water not only renders a concrete mix workable, but it also forms a chemical bond with the cement. The amount of water included in a mix has a strong influence on the longevity, toughness, and water tightness of a concrete product. The lighter the colour, the higher the moisture content of the blend. Controlling the water/cement ratio is essential for achieving consistent colour between different batches.

There are variables other than the pigment that may influence the final look of the product. Pigments used in concrete may be used individually or blended to reach a perfect colour, but in order to produce a satisfactory match, one must understand how the pigments behave in specific mixes.

The Use of Colour in Cement

Trying to control the colour of concrete necessitates an appreciation of the cementitious material content of the mix. Total cementitious binder, or TCB, is made up of cement and pozzolans. The “loading rate” refers to the amount of pigment needed to produce a specific colour. The amount of pigment required for the job is calculated by multiplying the TCB by the loading rate.

As people become more interested in decorative concrete, they will become more interested in concrete colour. Understanding the available technologies will be critical to retaining consumer loyalty as colour becomes more important in the concrete industry.