Both an essential substance and a potential menace, sulphates pose a specific risk to concrete structures around the world, yet many are not aware of this.
Let’s start at the beginning! What are sulphates?
Ever wondered what sulphates are? You’ve probably heard the term thrown around in chemistry class and it’s more a part of our daily lives than you realize.
Firstly, sulphates and sulfates are the same thing, depending on whether you use UK or US spelling, respectively.
Sulphates are reactive ions (part-molecules) consisting of Sulphur and Oxygen (-SO4). You can find out more here, but they are part of our everyday lives, in products as diverse as batteries, fertilizer, and plasterboard. That word ‘reactive’ is key to this discussion – that is why we need to talk about them in the context of concrete.
What is the threat to concrete?
| “Sulfate attack of concrete is a complex process, which includes physical salt attack due to salt crystallization and chemical sulfate attack by sulfates from soil, groundwater, or seawater.” – Developments in the Formulation and Reinforcement of Concrete |
| “External sulfate attack is a chemical breakdown mechanism where sulfate ions from an external source (underground water, sea water, some earthworks) attack components of the cement paste. Such attack can occur when concrete is in contact with sulfate-containing water, e.g. seawater, swamp water, ground water or sewage water. The often massive formation of gypsum and ettringite formed during the external sulfate attack may cause concrete to crack and scale. For external sulfate attack, the reaction propagates from the surface towards the concrete core.” – Science Direct – Sulfate Attack |
| You must admit, that covers a broad array of places where concrete might be at risk. Bridges, culverts, wharves, sewerage infrastructure – the list of at-risk structures goes on. The burning question is, how can they be protected? |
So, why should you be worried about sulphates? Mechanics of sulphate attacks are complex, but suffice it to say, they’re a real threat to concrete structures exposed to sulfate-containing water and the damages can be massive.
What is the answer?
The solution? It’s all about blocking the carrier of those aggressive salts: water. Concrete, essentially, is like a sponge. Without the right precautions, it will soak up moisture – and with it, the sulphates.
Think about this comment: “Proper placement, compaction, finishing, and curing of concrete are essential to minimise the ingress and movement of water, which is the carrier of the aggressive salts.” – ibid
Did you spot that phrase “… water, which is the carrier of the aggressive salts“? There’s our clue.
Block the Carrier
Concrete is not perfectly waterproof in and of itself. Bleedwater veins will develop during curing. Those veins guarantee the concrete will still accept moisture ingress. That moisture, as noted, is the carrier of the aggressive salts – in this case, sulphates.
Combat this issue by using the innovative AQURON 300 waterproofing admixture. AQURON 300 protects against sulphate attack from within the concrete itself – the internal matrix is protected.
Along with this, we recommend AQURON 7000 as a curing and durability hydrogel treatment. AQURON 7000 enhances curing, improving the concrete’s durability from day one; and permanently protects against external attack.
Project Examples
Wondering where this approach has been applied successfully? Some examples include:
- Fertilizer sheds in Balance and Ravensdown, NZ
- Acid tanks in Tasmania
- Waste water tanks and structures for various councils around Australasia.
Interestingly, a study by UNSW in 2000, which examined a comprehensive number of benefits of AQURON hydrogel treatment, confirmed that the hydrogel stops the reaction of sulphate ions. A copy of this study is available on request.
But that doesn’t help us with existing concrete … or does it?
As a matter of fact …
No, of course an admixture won’t assist for existing concrete (unless you’re doing cementitious repairs).
But AQURON 7000 is a real friend for even aged concrete. The treatment penetrates around 150mm into the substrate, regardless of gravity, effectively protecting the reinforcing steel.
Real projects, real answers
Ready to protect your concrete structures from sulphates? These treatments offer several advantages:
- Minimal downtime
- No need to re-apply
- Cost effective
- Ecolabelled, nil VOC, and potable water certified
Let’s discuss how these solutions can be implemented in your projects. Contact us and let’s get started!
