While the slab will harden and lighten in color before 28 days, don't be fooled into thinking it's done hydrating. If you plan to stain or paint the concrete, doing so before the process is complete can result in changes in the stain color or the paint peeling off. This content has been brought to you by Quikrete.
Curing times for concrete
Technically, concrete never stops curing. In fact, concrete gets stronger and stronger as time goes on. But, as far as we're concerned, to reach a practical strength, most industrial concrete mixes have a 28 day curing period.
Concrete doesn't turn white. If you're seeing white powder on the face, that is water driving out the salts as the concrete dries from the warm side. This might happen once in the curing process and then should not happen again. The timing is dependent on weather, temperature, humidity and salt content.
If water is used to cure, a lighter color is likely. Be certain to use curing, sealing, and cure-and-seal products approved for use with colored concrete and follow manufacturer's recommendations for application. Concrete will continue to lighten until it is fully cured.
Fresh concrete takes about 28 days to achieve standard strength. Young concrete / green concrete is in the curing phase during these four weeks. Hardened concrete is called the building material after 28 days, on / with it the construction can proceed.
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.
For each gallon of water, mix a cup of bleach. Use a scrub brush to scrub the mixture into any algae stains. Wait for 10 to 15 minutes before continuing. Rinse the concrete clean with a hose.
Usually this white or off-white discoloration to concrete and masonry forms when soluble salts and other water dispersible materials come to the surface through capillary voids as a result of temperature changes, moist migration, condensation, rain, dew, and/or too much water in the mix.
The concrete sets, and still looks acceptable…but only for a short period of time. The dark gray discoloration is caused by varying degrees of hydration of the cement in the concrete, caused by the varying moisture contents in the localized areas of the total concrete.
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.
Pressure washing is one of the fastest, most effective ways to get your concrete white again. Concrete can change color over time due to pollen, algae, or dirt buildup, but a good pressure wash can easily remove dirt and stains and make your concrete look new again.
In many cases, this is because of efflorescence. Efflorescence is that white powdery substance on the surface of your concrete that can appear over time. It can occur on anything containing portland cement and is commonly seen on concrete floors.
The product's major asset, aside form its striking architectural beauty, is its ability to remain white throughout its life. White concrete, obviously, is not a surface treatment that can deteriorate with age.
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.
The hardening, or curing, continues as long as moisture remains in the concrete. If too much water is lost from the concrete through evaporation, the hardening process slows down or ceases.
Excess Water
As the water evaporates to the surface and soaks into the cement that is an ingredient of concrete, it leaves behind darker spots where the cement contains more moisture. These will fade over time as the water eventually soaks into or evaporates out of the slab.
Factors influencing discoloration in concrete include inconsistent mixture, adding water to the mixture at a project site, changing cement color, using cement replacements, poor workmanship, etc. Discoloration due to these factors appears soon after concrete placement.
For mild discoloration, flush the hardened surface with hot water and scrub with a stiff brush to even out some of the variability in the concrete's moisture and mineral build-up. It may be necessary to carry out this process until the discoloration disappears.
White concrete requires chemical modification during manufacturing to create its colour. This means that white cement will cost more, so it is not economical for structural projects such as foundations.
Use Bleach
You already know that bleach is a trusty household product for brightening up stains on garments. But that's not all; chlorine bleach can also be used for cleaning the concrete driveway. Of course, you should dilute it with equal parts of water or a 1:1 ratio.
Sources of main differences between grey and white cement are raw materials, fineness, cost, uses, kiln fuel, energy consumption etc. Raw materials contain a high amount of Iron Oxide and Manganese Oxide. Raw materials contain a very little amount of Iron Oxide and Manganese Oxide. Usually less fine than white cement.
We have been told that cement people claim the greenish/blue discoloration is a phenomenon and of common occurrence with slag cement. It was reportedly caused by sulphide sulphers in the slag, with the discoloration occurring when no air reaches the surface or interface between concrete and form panel during the pour.
Yes, vinegar is an excellent concrete cleaner. This solution can strip surface-level messes from concrete. Due to its acidic properties, vinegar can be a powerful tool for breaking down offensive materials such as dirt, stains, and bacteria.
Green deposits, algae and moss can build up on patios, fencing and walls, in shady areas which don't get a lot of sunlight. This creates moist spots where algae and moss can grow, on concrete, wood and stone. This build up is also more common on soft and irregular surfaces, rather than straight, harder ones.