Common Issues of Discoloration in Colored Concrete and How to Avoid Them

While colored concrete can be a great option for your next project, there are a wide variety of factors that can cause issues of discoloration. The key to success when using colored concrete is consistency. Variations in cement color, sand, aggregates, weather, finishing techniques, water cement ratios, site conditions and curing techniques can all affect the final concrete color.

Consider that concrete uses natural materials that are finished by human hands.  What does that mean? Variations will exist. The causes of variations differ and some can be avoided with careful planning. Our goal is to have happy home owners who are excited about the results of their colored concrete. When completed correctly, the results can be fantastic.

The most common issues that can result in the discoloration of colored concrete:

Water Cement Ratios

The correct paste is the key to successful concrete behavior.  The hydration of cement can greatly affect the final product. For instance, if you have excess water it fills up space and evaporates as the concrete cures. The empty spaces left over after the concrete hardens are called pores. The more pores concrete has, the less strength and density it has.  In addition, if too much water is added to the concrete mix, it increases the potential for efflorescence and reduces the effectiveness of the pigment. Water added to the mixture or bleed water on the surface can then result in a lighter color of concrete versus what may be expected.  How do you avoid these issues? Make sure your water cement ratios are within specification on the delivery ticket prior to pouring out the concrete mix.  For help on how to read Folsom’s delivery tickets, feel free to contact us.  In addition, we recommend the use of admixtures to increase slump instead of using water.   Lastly, be sure to not use water as a curing agent for colored concrete.  This is not a proper technique and there are specific curing chemicals to be used especially when it comes to colored concrete.

Finishing Techniques

Common practices such as “blessing of the concrete” can actually have a negative impact on the finishing of colored concrete. For instance, the wet broom streak technique is used routinely to finish the surface of the concrete. This is a big mistake with integrally colored concrete as it will alter the surface color.  This is because the moisture of the wet broom changes with each stroke affecting the appearance of the different sections of concrete.  In addition, if “brooming” occurs in different directions on the surface of the concrete it can alter how natural sunlight reflects making it appear to be a slight shade different than the concrete right next to it.

Troweling techniques can also impact the appearance of integrated color concrete.  Troweling can significantly impact how bleed water evaporates from the concrete mix and ultimately how the concrete cures.  This process can impact the finished look of any concrete not just colored concrete.  Bleed water is the natural migration of water to the top surface of freshly placed concrete caused by the settlement of the solid materials (sand and stone) within the mass. This settlement is the consequence of the combined effect of vibration and gravity. Improper and/or inconsistent finish sequencing can have a lasting effect on the look of the colored concrete. Let’s consider troweling colored concrete for a moment.  Early troweling, late troweling and over troweling can all have lasting effects.

• Early Troweling – do not finish troweling before the bleed water rises to the surface and evaporates. This creates entrapment and is one of the principle causes of concrete surface defects. This can translate to a weakened surface, altered color and strength.
• Late Troweling – this practice causes dark areas and “seals” the surface. These are called trowel burns. Obviously, this will have lasting affects on the concrete including how sunlight hits the different textures on the surface creating an inconsistent look despite the concrete color being consistent throughout.
• Over Troweling – the colored concrete begins to fade before curing. The appearance of fading is caused by efflorescence. Efflorescence is a white, powdery residue on the surface of the concrete. It is dust or dirt and abrasions of the concrete surface and it hides the color of the concrete. This is often caused by over troweling and the evaporation of salts. You can avoid this color issue by minimizing soluble salts, water penetration, and migration of water. If you have efflorescence, you should remove it properly to showcase the real color of the concrete before it converts to calcium carbonate and becomes permanent.  Contact us should you need help with this process.

Weather and Site Conditions

Seasonal climate changes are also a big factor in the finishing and curing of concrete. Remember that hot or cold weather conditions can lead to the concrete surface looking light or bleached. Blotchy color can be caused by variation in concrete curing due to the jobsite environment. This can vary due to something as simple as concrete located in sunny areas vs. shady areas.  Many people see discoloration before concrete is fully cured in these instances. We advise our customers to always wait approximately 90 to 120 days before making any judgments on the color of their concrete as the final product isn’t truly revealed until then.  In addition, talk to your contractor about using retarders (for hot weather conditions) or accelerator (for cold weather conditions) as well as hot or chilled water in the mix to help control the curing process in spite of seasonal weather changes.

Is your existing cured colored concrete fading?

In this instance, power washing may be an effective way to clean the colored concrete surface. Power washing can remove debris, efflorescence and stains. Mild acid, Super Blue or other commercial concrete cleaners can also work well to gain more uniformity in appearance. Be sure to connect with an expert for specific advice on treating your existing concrete before taking any drastic steps. We’d be happy to help should you have any questions/concerns.

Many of these common issues associated with the discoloration in colored concrete can be avoided. Always be mindful of how you’re finishing the concrete and how the items mentioned above regarding the use of brooms, water, trowels/finishing and weather conditions can affect your job.

Our main goal is to make sure that our customers understand these issues associated with colored concrete and their potential causes.  However, should a customer believe that the concrete mix itself is the cause of the discoloration, Folsom Ready Mix has a procedure for checking to ensure the issue did or did not occur on our end.  This includes but is not limited to the following:

• Evaluating concrete mix batch weights to ensure the color pigments were added within specification
• Evaluate consistency in pigmentation across all loads of concrete delivered to that location
• Ensure loads all came out of the same location and plant to help rule out any differences in materials across different loads
• Visiting the job site with some of our quality representatives alongside your contractor to identify what may have gone wrong.

We take all of our customer complaints very seriously, especially discoloration complaints, given the application of such a product is to improve the appearance of someone’s property.

Have any questions about using integrated color in your next project? Ready to get started?

Contact us today! (916) 851-8300