Discoloration of Concrete: Causes, Preventions, and Treatment?
What do you mean by Concrete Discoloration?
Contractors who have placed concrete that turns out to be discoloured know what a hassle and disappointment of concrete discolouration. A concrete discolouration occurs when the original colour is altered.
The concrete discolouration is caused by calcium chloride mixtures, cement alkalis, hard surfaces, inadequate or inadequate curing, wet subsurfaces, and varying proportions of aqueous cement on the surface. The discolouration caused by these causes appears very soon after the concrete has been poured.
A contractor can, however, mitigate the effects of dark patches, strips, and blotchy concrete by taking a few steps. Based on the root of the discolouration, the appropriate treatment method can be selected after the concrete has cured.
Why does concrete to discolour?
The concrete discolouration is caused by a variety of factors, some of which are as follows:
In order to avoid unfavorable colour issues throughout a project, mixing proportions consistently is crucial. It can be challenging to produce a concrete surface with a consistent hardness when there are differences in the mix delivery from batch to batch.
You should receive a concrete mixture that is homogeneous from your ready-mix supplier. Yet, it is tougher than it seems since each of the several components that make up concrete has a different set of characteristics. interactions between the various components of a batch of concrete, such as cement, additional cementitious materials, sand, stone, water, admixtures, and sometimes fibres, in a consistent manner.
There must be compliance with ASTM standards by all constituent parts of the concrete. The use of high-quality aggregates in concrete is crucial. Sand and stone moisture levels will determine how much-mixed water is needed. The industry may suffer serious repercussions if this is not done.
Change in the colour of the cement
During cement production, cement may change in colour slightly depending on the burning or grinding conditions. If a cement substitution occurs during an ongoing placement or this modified mix is put down right next to concrete made with cement from a different source, a concrete colour shift caused by a change in cement colour can be evident.
If a cement substitution occurs during an ongoing placement or this modified mix is put down right next to concrete made with cement from a different source, a concrete colour shift caused by a change in cement colour can be evident.
Addition of water on the job sites
Adding water on the job site to the concrete makes it easier to work with the concrete. But if the proportion of water becomes more or less there might be a chance of the discolouration of the concrete.
Addition of Calcium Chloride
It is possible for calcium chloride to cause the concrete to take on darker hues when it is used to speed up concrete's setting time, especially at concentrations of 2% or more by weight. A lack of adequate mixing after adding calcium chloride can exacerbate colour irregularities in concrete.
How can you prevent concrete from getting discoloured?
There are some steps that you can take to prevent concrete from getting discoloured, these steps are:
1. In order for concrete to cure evenly, it must be mixed evenly. Sheets can dry unevenly if they are placed on moist surfaces, curing unevenly if they touch in some spots and not in others.
2. A concrete pouring mould you use might also impact the result. The water may either be absorbed or pushed away if you switch them in the middle of the procedure. The colour and moisture content may change as a result.
3. If metal shards are left in the concrete after the trowel burning, it may corrode or discolour it in a different way.
4. The consistency of drying could also be improved by eliminating calcium chloride.
What is the best way to treat discoloured concrete?
1. Acid Treatment
For severe discolouration, a moderate acid solution should be used, such as 1% to 3% muriatic acid. Using the right percentage of muriatic acid is crucial since too much of it weakens concrete and causes stains.
A smart technique to control how deeply the acid permeates the concrete is to flood the area first, let it dry and then applies the acid solution. If the corrosive solution is given more time to cure, it can seep further into the concrete.
As a result, it is advised to work on a concrete surface that is controllable and to control acid penetration based on how quickly the area dries after flooding. You have 15 minutes to wash any acid solution off of you after applying it.
2. Concrete Resurfacing
If the stains and discolouration are severe and cannot be completely repaired, you can hide the incorrect hue by pouring concrete over the entire area.
The hardened surface should be flushed with hot water and scrubbed with a fine brush to remove any light discolouration caused by differences in moisture content and mineral accumulation. This process may need to be repeated several times depending on the severity of the discoloration. Apply a fresh, thin coat of concrete sealer once the concrete has dried and any stains have faded away.
To learn more, watch the following video tutorial.
Video Source: DIY Concrete
4. Colour Tinted Sealer
In the event that washing the concrete surface is unsuccessful and acid solutions are not desired, the discolouration can be concealed with a tinted colour sealer. In contrast to acid solutions and acrylic sealers, a sealer would not compromise the material's aesthetics if it seeps into the concrete.
Using acid, the surface takes on a marble-like appearance, while using an acrylic sealer, the surface is darkened and leaves a glossy finish. To ensure a consistent sheen, test a small area with a solvent-based acrylic sealer. The concrete surface can be covered completely with an acrylic sealer by tinting it.
5. Polymer Coating
Using a polymer-modified coating, it is possible to conceal the discolouration and stain. This type of coating is typically used to cover graffiti.