cracked concrete patio

We explain some potential problems with concrete.

Will my concrete crack?

Cracking can happen. As concrete hardens, excess water evaporates which causes the concrete to shrink, and this is what can cause cracking. The proper use of Construction Cuts, proper site preparation, and good concrete placing will significantly reduce the risk of any cracking. Even then, cracks can occur. Contact us to find out more or view information on cracking by the Cement and Concrete Association of New Zealand.

Will the colour of my concrete fade?

The iron oxide pigments we use for our colours are sourced from Bayferrox and so are of the highest quality and have the highest light fastness values of any iron oxide materials available in the world – even under NZ’s harsh UV conditions.

The colours don’t really fade as other materials do. Iron oxides are extremely colour stable, and any slight fading that will occur would be barely noticeable, even after 25 years or more.

What causes motley colour?

Concrete has a characteristic mottliness or cloudiness. PeterFell colours often highlight and extend this. It is unlikely to be uniform colour but this is part of the appeal. It gives your space a natural element – one of the key design features of concrete.

What is “Pinto concrete”?

Very occasionally irregular, dark blotching (or “Pinto”) may appear on the surface of your concrete. This can happen regardless of whether colour is used or not. It’s not known exactly what causes this but it seems to be related to the curing of the concrete ie how it dries and how moisture moves through the slab.

Ensuring consistency of placing and curing across the slab should help to prevent it.

If this does occur, sanding the surface then applying a light acid wash may reduce the effects.

For more information on pinto click here.

What is concrete ‘measling’?

Occasionally, after the concrete is sealed, dark patches may appear when the surface is wet and then disappear when the surface dries.

This is called ‘measling’. It’s caused by microscopic holes/cracks/high-points in the sealer that let small amounts of water into the concrete. It only happens from time to time and is the result of concrete being concrete, not because of bad workmanship or faulty materials.

The effect will occur less and less over time. To fix it, we suggest topically applying more coats of sealer. You need to be careful however, not too add too many coats over large areas as it may make the surface more slippery.


What is efflorescence?

Efflorescence is a crystalline deposit of salts, usually white, that forms on or near the surface of concrete.  It forms when salts are dissolved by water migrating through the concrete then precipitated at the surface.  Efflorescence is particularly noticeable on dark or coloured concrete where its effects are seen as colour differing in intensity and shade from that intended, varying over the surface and changing with time.

Efflorescence cannot be removed by traditional cleaning products, can often be treated with a mild acid wash.  In the PeterFell System, PFL Surface Preparation, PFL Surface Prep Lite or PFL Acid Gel can be used to treat efflorescence and sealing the concrete can prevent any reoccurrence of the salt deposits.

For more information on efflorescence click here. (IB 44)