Hard Calcium Carbonate deposits Calcium salts react with Carbon Dioxide in the air and form non soluble Calcium Carbonate. This is the hard white or yellow efflorescence seen on concrete and bricks. Because it is not soluble, Calcium Carbonate cannot be washed off the surface.
Calcium chloride in concrete is a primary cause of concrete discoloration. The chances for discoloration are much less if calcium chloride or chloride-bearing chemical admixtures are not used. The type, kind, and condition of formwork can influence surface color.
Discoloration Caused by Efflorescence
Efflorescence is water soluble so it often disappears when rinsed away with water. The efflorescence however really isn't gone and will re-form again quickly after. The best way to remove efflorescence is with an efflorescence cleaner, such as the Foundation Armor ER100.
Simply fill a spray bottle with equal parts water and vinegar (or water and baking soda), and add a little bit of liquid dish detergent. Spray the mixture on your concrete surface and let it sit for about 30 minutes. Then scrub and rinse your concrete.
If a foreign object retards the movement of moisture out of the concrete or traps moisture at the surface, a curing differential occurs, resulting in a color shift in the concrete surface. Case in point would be random plastic or lumber placed on a concrete slab 24 hours after installation.
Concrete discoloration is not a rare event
Laying concrete isn't an exact science, and there are a variety of factors that can contribute to concrete discoloration from the very beginning. These factors include: Variability in concrete mixtures. The use of too much or not enough water.
Water-based sealers do not change the color of the decorative concrete, but solvent-based sealers darken the color by several shades. This darkening effect is called color saturation. The color saturation remains as long as the seal coat is maintained.
Vinegar or baking soda: These natural cleaners work well to clean cement patios with stubborn charcoal or rust spots. Mix equal parts vinegar and water, scrub the patio with the mixture, then give it a good rinse. If stains don't dissolve, try undiluted vinegar.
If you don't have tea tree oil or don't want to use it, this homemade concrete cleaner will still be effective due to the addition of baking soda and peroxide. They work together as an anti-fungal, but also whiten and remove the stains from mildew.
White vinegar and a little scrubbing with a brush is a very effective, eco-friendly way to remove rust stains from concrete—even those that are decades old. Pour the white vinegar directly onto the stain, allow the liquid to penetrate the area for 20 minutes, and scrub with a stiff-bristled brush.
Cleansing — For mild discoloration, repeatedly flushing the hardened concrete surface with hot water, then scrubbing with a stiff brush, can reduce or remove discolored blotches. Acid treatment — If the discoloration is more severe, a mild acid solution of 1-3% muriatic acid to water can help remove the discoloration.
Bleach is commonly used to whiten concrete and is very effective at doing so if the initial stain is removed beforehand. Bleaching stained concrete white prepares it for any additional coloring treatments that you may wish to apply in the future.
In warm, sunny weather, concrete should be nearly its final color after about two weeks. In cooler, damp or overcast weather, the concrete will take at least a month or longer to reach its final color.
If you need to get rid of rust from concrete, your best bet is to use some WD-40 Multi-Use Product, and some elbow grease. WD-40 is specially formulated to be a penetrant, so when you spray it on a rusted surface, it gets to work right away by getting under the rust.
Vinegar is a natural and safe alternative to cleaning concrete with harsh chemicals. In the case of algae and mold, it does a better job than bleach, and it is better in the long term for killing these infestations. Oftentimes, vinegar can be found in your home or garage.
Coca Cola contains citric acid that breaks down the molecules in motor oil and unsightly grease, allowing the stains to be easily washed away. With the aid of a stiff brush, Coke can remove motor oil, grease and even rust stains from concrete surfaces like your garage floor with ease.
Unsealed concrete is porous and can absorb various types of liquids such as water and oil. Depending on the type of liquid, it can cause the concrete to become discolored and stained. The fluids will also cause unsealed concrete to gradually start to deteriorate and break down.
Heavy coats of sealer, or a buildup of sealer applied numerous times over the years, will cause moisture to become entrapped under the sealer and, in time, the sealer loses adhesion from the concrete.
Left unsealed, the colors will fade, water marks may be an issue, and stains can penetrate leaving ugly oil spots where the service guy left his old jalopy parked on the driveway. It's pure and simple, the job just won't last without a good sealer.
Earth tones that mimic natural materials are the most popular concrete colors among homeowners. But you can also color concrete blue, orange, green, black or other colors. Plus, many concrete contractors can blend custom colors exactly to your liking.
If there is any dry powder in your mix then you need more water. But if your mix looks and feels soupy then it's too wet. Remember, you want a thick oatmeal. You should be able to hole the concrete in your hand and form it like a snowball.
Why is my concrete turning white? Efflorescence is a white salty residue caused when too much moisture is moving through the concrete. As the concrete dries and its moisture rises upwards through the slab, it brings salts within the concrete to the surface as well.
Although causes of high moisture levels vary, research shows that the most common reasons are a high water table, water running off from heavy landscape, and underground water sources that cause hydrostatic pressure. All this makes the concrete appear white. Beauty and strength converge in decorative concrete.
Even if it starts raining after a concrete pour, the potential for damage may not be that serious. If you had time to complete the finishing process and the concrete has stiffened (typically 4 to 8 hours after mixing), rainwater may cause little if any damage.