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How can Sulphate Attacks be Prevented?

Sulphate attack in domestic building

This occurs when a concrete slab is in direct contact with demolition hardcore or shale fill with no damp proof membrane separating the layers.

Sulphate salts then migrate in the form of an aqueous  solution from the hardcore into the concrete.  The salt when reacts with the tri calcium aluminate in the cement paste causing new chrycotoline formations to be created.

This chemical reaction causes the concrete to expand and buckle pushing our the walls at DPC level and lifting the floor surface.

The only method of repair that removes the likelihood of additional damage and a return to saleability is to remove all of the concrete and provide new on  a new damp proof membrane.

Sulphate attack in the ground

There are occasions where there is a natural sulphate content in the ground in which the building is founded, a groundworker analysis should indicate the contamination level.

To lower levels the answer is to increase the portland cement contents but to higher levels the use of sulphate resisting cement is required.

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