Efflorescence

WHAT IS EFFLORESCENCE?

There is a chance that after a few weeks or months pass, a white haze may appear on the surface of the pavers. This so-called white haze is known as efflorescence and is a natural phenomenon. It may appear randomly or in certain areas, and will be more pronounced on dark coloured pavers. The white haze may give the impression that the colour of the pavers is fading. When wet, the white disappears and the colour of the pavers is enhanced. When dry, the white haze reappears

EFFLORESCENCE DOES NOT LAST FOREVER

Rain usually washes the efflorescence away in about 1 to 2 years. If you do not want to wait that long, you can wash with diluted hydrochloric acid (1 part hydrochloric acid, 20 parts water) as a quick remedy. This has the additional advantage of washing out the lime in the upper layers of the concrete. However, the stone surface becomes rougher and the shade changes slightly. The acid should be washed off thoroughly with water afterwards.

THE CHEMISTRY OF EFFLORESCENCE

All concrete products contain cement, which produces lime or watersoluble calcium oxide. Lime can also be in the bedding sand, aggregate based materials or soil. Although concrete products are solid, strong and very dense, they contain millions of microscopic capillaries that run from the interior to the surface. Moisture from rain, sprinkler systems, underground sources, poor drainage or dew enters these microscopic capillaries and forms calcium oxide. Inside the concrete product this reacts with the water in the capillaries and forms calcium hydroxide. This rises to the surface, reacts with the carbon dioxide in the air and forms a white haze of calcium carbonate. When the moisture on the surface of the concrete product evaporates, the white haze of efflorescence becomes visible.

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