what is efflorescence and how to treat it

What is Efflorescence and How To Treat It

Marshalls Plc Marshalls Plc Monday 31st August, 2015

Hello and welcome to the final post of our four part series which offers advice and help on how to maintain and maximise the longevity of your driveway or patio. Why not read some of our other blog posts on Driveway/Patio maintenance?
Blog 1: How to Clean Block Paving

Blog 2: Handling Stains & Spillages

Blog 3: Use of Chemicals & Acids

Blog 4: Efflorescence

Efflorescence is a naturally occurring phenomenon that sometimes appears on the surface of cement based building materials and clay products. Efflorescence is a transient phenomenon on Ordinary Portland cement. As the cement and weather chemically react together, calcium hydroxide is produced. As the concrete dries, the calcium hydroxide reacts with the carbon dioxide in the atmosphere to produce calcium carbonate, which manifests as a white solid.

The occurrence of efflorescence in the pores of the concrete can lead to the appearance of white patches on the surface or an overall lightening of the product which is often mistaken for the product fading. Although the appearance can be worrying the effects of efflorescence are purely aesthetic, and does not alter the strength or durability of concrete.

The best means of treating an affected area is by allowing natural weathering to take place. It is possible to accelerate its removal by washing the affected area with a propriety biodegradable citric acid based cleaner.

Efflorescence on clay products results when soluble salts go into solution in the body of a saturated brick or block. As the clay dries out, the water constraining the salts within it migrates to the surface of the clay face and evaporates away, leaving a light grey or white powdery deposit which will weather away naturally over the subsequent months. Chemical methods should never be used for the removal of efflorescence from clay products and under no circumstances should wire brushes be used for cleaning the surface of clay paving.

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