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Frequently Asked Questions
What decides whether it is needed?
The ground, not the structure.
A soil and groundwater investigation.
Sulfate concentration is measured.
The exposure is then classified.
Nothing about the building decides it.
What is sulfate attack?
A reaction inside hardened cement paste.
Sulfates in solution attack one compound.
A new mineral forms in its place.
That mineral occupies more space.
The expansion happens within the concrete.
What does the damage look like?
Softening, cracking and disintegration.
It progresses from the surface inward.
It develops over years, not months.
It happens below ground, out of sight.
By discovery the element may be lost.
How does the cement resist it?
It contains very little of the vulnerable compound.
The reaction then has little to work with.
Composition is controlled to achieve that.
It is a chemical answer, not a coating.
Protection is throughout the material.
Where do sulfates come from?
Naturally in some soils and groundwater.
Certain clays especially.
Made ground containing gypsum plaster.
Some industrial wastes and fill.
Brownfield sites need particular care.
Can you judge a site by eye?
No, and assuming so is the failure mode.
Ordinary-looking ground can be aggressive.
Made ground is the least safe assumption.
Testing is inexpensive by comparison.
The damage is not repairable.
Is CEM III an alternative?
Yes, by a different route.
High slag content resists sulfates too.
It is often specified in its place.
Especially where low heat also helps.
They are alternatives, not complements.