How To Color Concrete Mix

There are several ways to color concrete mix and cement, it all depends on the final use of the artifact we are going to color.

How to color concrete

We often talk about coloring cement but, in reality, the material we are going to paint or create is almost always concrete or cement mortar.

Cement, on its own, risks being subject to excessive shrinkage and therefore cracks, so the composition always provides for the addition of sand and, often, of fibers, to control the shrinkage of the mixture.

When is it necessary to color the concrete?

There may be many cases in which it may be desirable to change the final coloration of the concrete mix. Gray, in fact, comes off as a bit monotonous, and color helps to make concrete products significantly more pleasing to the eye.

PIGMENT FOR CONCRETE

Mostly, it is used to color artifacts that we may have created ourselves, for decorative purposes, such as bottles, small vases, paperweights or bookends.

Another very common use of colored concrete is in the creation of decorative blocks for paved driveways in the garden.

This last use leads us to another very important consideration that we will develop later: the coloring techniques can (and in many cases must) be different depending on whether they are vertical coatings or walkable items to be laid on the ground.

In the second case, in fact, a simple superficial coloring could prove unsuitable.

But let's go step by step.

Difference between painting the surface of concrete and coloring the mix

The color that can be achieved by adding specific colorants to the concrete mix is very different from the color that can be achieved by simply painting its external surface.

In the latter case, the coloring of the surface is easily attacked by the weather (if the concrete is placed outdoors) and must be protected with a layer of transparent paint which limits degradation.

In the case of powders added to the concrete mix, together with cement, sand and fibers, what is obtained is a coloration that concerns the entire mix and therefore not only the external part.

Needless to say, this type of coloring is particularly suitable for those items that are subject to wear and tear, such as self-locking bricks or driveway slabs.

When the color is added to the mix, the end result will be a concrete having an opaque color, while when only the outer surface is painted, the colors that can be obtained are much more varied and can even be glossy and bright.

By painting, by brush or spray, the cement, however, the texture of the material is lost, that is, the cement may no longer appear as such, especially when viewed from a certain distance.

This may be desirable in many cases and in others a little less so: if we want to paint a concrete floor we could also use special resins that give the surface a smooth and shiny appearance that is particularly suitable for garage floors and that, in recent times, is also becoming popular in residential environments.

In case we want to color the concrete blocks with which we have made a driveway, however, it is necessary to resort to a more durable solution and less conspicuous colors and this can be achieved only by mixing special pigments within the mixture.

It goes without saying that this last operation only makes sense if we are going to make the blocks ourselves using molds that can be purchased online or that we will have self-made.

COLORING THE CONCRETE MIXTURE

As already written above, what you are going to color is actually the concrete mix, or a mixture of cement, sand, fibers and water.

Obviously, for coloring you will have to get pigments that can also be purchased online.

To understand what percentages of materials to use to get a good final result, I invite you to watch this video that explains quite well how to proceed.

To achieve the smoothest possible surface, the sand grains should be as small as possible. In the video a powder has been used but it doesn't necessarily have to come to this, in the case where we want to "print" bricks for an external driveway, some final roughness may even be desirable.

When we want to make a concrete top for the kitchen on the other hand, the smoother the surface the better.

As you can see from the video, to obtain an optimal colored mixture it is necessary to have a mixing paddle because, mixing with a trowel alone, it would otherwise be difficult to obtain a homogeneous coloration.

NB: since pigments for concrete have a certain cost, it can be convenient not to color all the mixture but to color only the surface layer.
This presupposes that you are going to create two mixtures: one colored to obtain a layer of one or two centimeters, which will remain visible, and then a remaining layer that can be composed of mortar not colored. The two layers must be applied in succession, when the mixture is still wet, so that they can bind perfectly and form a single body.

Painting the cement externally

Painting concrete is more difficult than painting most other surfaces: concrete is breathable, transports moisture and sucks up paint.

For all these reasons, the surface must be very carefully prepared to achieve a smooth, durable paint job.

The first thing to do is to wash the surface and fill in any cracks.

After the concrete surface has been sanded it must then be washed again to remove all residual dust.

A primer is then applied to make the surface less absorbent and better anchor subsequent coats of paint.

Concrete paint (also called elastomeric paint) is a good choice for painting concrete as it contains binders which contract and expand with the concrete.

There are paints that can be spread with a trowel, brush or roller.

If it is a walkable surface, the floor should then be protected with a protective top coat so that scratches and abrasions that may be created through use are limited.

If you need to paint concrete or cement blocks that have a decorative or furniture purpose, the advice is not to cover the entire surface but rather use stencils or create geometric shapes that allow you to leave visible part of the concrete surface of the artifact, this in order, as I said above, to make it clear that these are concrete blocks and not other material.

DIY Editor
Do-it-yourself enthusiast. I started with the renovation of my flat and then I changhed this passion into my job.