Concrete discoloration is not a rare event Variability in concrete mixtures. The use of too much or not enough water. The use of calcium chloride. Improper concrete laying techniques.
For subtle color correction, a pigmented sealer may be enough. Sealing or resealing one or both slabs with a pigmented sealer can provide a quick and easy fix while providing protection that is already necessary for decorative concrete.
If the concrete can cure consistently, the end result is usually a quality concrete product with consistent color and finish. 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.
Calcium chloride —This substance is often added to speed the drying process. And if it's not mixed in thoroughly, it will create blotches in the dried surface.
Fresh concrete is always much darker than when it is fully cured and dry. Even uncolored concrete. Wait at least 7 to 10 days until the new concrete has hardened and dried. If the concrete is on a wet subgrade or there's underground water, it may stay dark for as long as it's wet.
Concrete will continue to lighten until it is fully cured. Allow the concrete to cure at least 30 days before inspecting it for color match or appearance.
When a blemish appears on the surface of a concrete slab it will likely be one of these: blisters, cracking, crazing, curling, delamination, discol- oration, dusting, efflorescence, low spots, popouts, scaling, or spalling.
Factors influencing the discoloration are calcium chloride mixtures, cement alkalis, hard surfaces, inadequate or insufficient curing, wet subsurface, varying proportions of aqueous cement on the surface, and changes in the concrete mixture. Discoloration from these causes appears very soon after concreting.
When a concrete mixture is too wet, it causes a greater amount of shrinkage during the drying process than is needed. As a result, the concrete has a great likelihood of cracking and for those cracks are likely to be a fairly good size.
As moisture rises to the surface of the concrete, it carries with it the calcium salts from within the concrete. These react with CO2 at the surface, forming that white powdery dust. It can be worsened by exposure to moisture, such as rain. With no moisture movement, there is no efflorescence.
Concrete stains can be a great option for changing the color of your concrete without having to completely resurface it. EasyTint solvent-based tinted sealer is a semi-transparent stain that can add a new color to your already stained concrete.
Steps to recolor faded stamped concrete:
Apply additional coats of stain without waiting for the first coat to dry. Allow the final coat of antiquing stain to dry for at least 8 hours. Once the stain has fully dried, apply a solvent-based acrylic concrete sealer to protect the color from fading in the future.
When the sealer is applied too heavily, the air displaced through the surface can't escape, and it forms a bubble in the sealer surface. Bubbling of a sealer can also occur if application is done in hot weather, or if the concrete is in direct sun.
Acrylic sealers offer the most enhancement to dull and faded concrete. If you are looking for a dramatic color enhancement, or want a low to high gloss finish, acrylic sealers are the best sealers for enhancing color in dull and faded concrete.
DO spray new concrete with water. One of the most common methods for curing concrete is to hose it down frequently with water—five to 10 times per day, or as often as you can—for the first seven days. Known as “moist curing,” this allows the moisture in the concrete to evaporate slowly.
Moist curing is a common method of concrete curing. It involves wetting the concrete slab often with water (5-7 times per day) for the first 7 days. This method ensures your concrete slab will be extremely strong and durable, because it allows the moisture to evaporate slowly, preventing cracks and shrinks.
Concrete that is not moist-cured at all dries too rapidly, and reaches less than half its potential design strength. It will also have a greater number of shrinkage cracks.
Pigment selection, the type of cement, aggregate size and color, water content, mixing technique and finishing methods all have a role to play in the overall final appearance of the decorative concrete surface. Cement color is the starting point and the determining factor in what range of colors can be achieved.
Concrete typically takes 24 to 48 hours to dry enough for you to walk or drive on it. However, concrete drying is a continuous and fluid event, and usually reaches its full effective strength after about 28 days. Here are some of the basic facts regarding the question of concrete drying and curing time.
Scaling is one of the most common problems of concrete. In scaling, the surface layer of concrete gets deteriorated by getting peeled or by breaking off.
If you see darkened and discolored areas, there's a good chance your floors are being damaged by moisture intrusion. Over time, water can delaminate the commercial floor paint from the surface, meaning the paint will lose its adhesion and begin to peel, chip, or flake away.
Although the bulk of the hydration process takes place in the hours and days immediately after the pour, concrete needs 28 days to fully dry. While the slab will harden and lighten in color before 28 days, don't be fooled into thinking it's done hydrating.