Guidelines to prevent secondary efflorescence

Efflorescence found on concrete roof tiles can be classified in two categories: Primary and Secondary efflorescence. Primary efflorescence may occur during the curing of the concrete roof tiles, while secondary efflorescence can occur after the tiles have been exposed to atmospheric conditions.

Secondary efflorescence

The secondary efflorescence mechanism is a result of the initial time of exposure of the roof tiles to outdoor conditions. The maximum intensity is reached during the early life of the product and usually begins to clear about two years after the date of initial exposure.

Secondary efflorescence is a worldwide phenomenon which occurs in extremely low rainfall areas; in highly humid climates, or in high rainfall areas.

Efflorescence is purely superficial and does not affect the durability or strength of concrete, the original colour or the functional properties of the tile. However, it detracts from the uniformity of colour and can stand out against other roofs not suffering from efflorescence.

The limitation of secondary efflorescence

Since the exact causes of secondary efflorescence are unknown, only the symptoms can be treated. The following method is to be used in the production process to prevent secondary efflorescence.

Acid treatment

Cured concrete roof tiles are treated with a dilute solution of hydrochloric acid as part of the manufacturing process.
The objective of this treatment is to remove any efflorescence chemically.

Conclusion

The term efflorescence covers a number of very different phenomena. Although they all appear as a white haze of calcium carbonate on concrete roof tiles they are the result of very different causes. In the case of secondary efflorescence, a solution has not been achieved, as it is not possible to reproduce it in a laboratory.

Of the greatest importance is the fact that the natural removal of efflorescence does not affect the original colour of the product. In no way does it hinder the product's permeability, colour consistency or continuing strength growth with age.
These are all important factors which contribute towards making concrete tiles an exceptionally successful and cost-effective roofing medium.

Efflorescence is purely superficial and aesthetic. It does not affect the functional properties of the tiles or the physical performance of the roof in any way.