This is the appearance of unsightly white deposits or stains of the surface of the paving blocks. This is neither a manufacturing defect, materials defect nor an installation fault, but a natural occurring phenomenon in the concrete caused by calcium hydroxide (lime deposits) reacting with carbon dioxide in the air. It may seem to disappear when the paving is wet, but the efflorescence salts temporarily vanishes but will return again when the paving dries.
Be reassured, efflorescence has no detrimental effect on the paving and will generally disappear with time. Depending on climate conditions and location, it can take 6 months to two years to disappear. Once it does disappear naturally it usually does not reoccur.
If it is really bothering you, to improve the appearance short time, you can use a efflorescence remover but be sure to follow the manufacturer’s instructions.
Avoid sealing your paving until the problem has cleared up.