Efflorescence, also known as humidity patches, are a common occurrence on paving stones that have just been laid. The stains seem like white powdery deposits that are spread throughout the surface of the pavers. These spots are salts that have leached out of the pavers when the brickwork dries and the water that was in the stones evaporates. When there are no more salts to leach from the brickwork and when the salt deposits are worn away by usage and rinsed away by rain, efflorescence patches will finally disappear on their own. According to Concrete Network, another option is to remove the spots manually whenever they occur; however, you should keep in mind that they will keep reappearing until the pavers have finished curing.
When washing pavers containing Portland cement, it is very vital to do a test on a small area beforehand. After the pavers have been washed, the acid wash should not be allowed to sit on them. Because sealers cause the efflorescence to get trapped within the sealing layer, they should not be applied until after the pavers have completed the curing process.
According to advice from Paving Expert, salt deposits should be scrubbed with a dry wire brush until they are broken up and become loose from the pavers. When the pavers are dry, proceed with this step.
Use a broom to remove the salt deposits that have become loose from the pavers, and try to get as much of the white powder off of the stones as you can.
Use a hose to remove any trace of powder that may still be on the stones. If you want to use a power washer, you should not use it more often than twice per year to prevent the surface of the pavers from being damaged.
If brushing and water alone are not sufficient to clean the stones, you should try using an acid wash. Calcium carbonate and calcium sulphate deposits are the types of deposits that may need an acid wash since these chemicals are more likely to adhere to the masonry than alkali salt deposits are. Because acid washes may be rough on the surface of pavers, their usage should be limited as much as possible. Always do a test on a tiny, unnoticeable area first to guarantee that the acid wash will not have an effect on the colour of the paving stone.