MODERN CONCRETE AND DURABILITY ISSUES
There’s a lot of research on ancient Roman concrete, with solid examples standing to this day. In 2017, there was a good deal of excitement over the recently published discovery that Roman concrete actually grows stronger as it ages and naturally withstands seawater. These effects are apparently caused by specific volcanic materials included in the mix – substances which are not commercially available to most of us.
The other rare commodity in the modern world of construction is time. Time is money, so schedules are squeezed to a minimum wherever possible. For concrete, this often means a minimal curing time. Unfortunately, it also means placement may be rushed, leading to uneven coverage and other issues.
(Low cover is something the Romans never needed to worry about … steel hadn’t been invented, and their concrete did not use internal reinforcing)
KEY POINT: There’s a clear link between concrete cracks and the deterioration cycle.
More on this later – but here’s something to think about.
One major Australian premix company lists four main factors as causes of concrete cracking at construction:
“
- Construction and supervision problems – approx. 36%.
- Design defects – approx. 27%.
- Ambient conditions (temperature, humidity, etc.) – approx. 21%.
- Quality of materials – approx 17%.
”
Is it any wonder modern concrete isn’t lasting as long as the Roman experience?!
WHAT CAN WE DO ABOUT IT?
Concrete needs protection.
For risk mitigation and to preserve the intended service life, concrete needs treatment over and above its mix design.
Early hairline cracking is commonplace and can serve as a gateway to reactive contaminants.
Exposure to the weather can also allow contaminants to enter the concrete due to its porosity.
There’s a lot of valid discussion on impermeability in this connection, but the bottom line is that it’s impossible for commonly used mix elements to provide total impermeability. The curing process itself will open bleedlines in the slab as excess moisture rises. These leave cavities that later become avenues for moisture ingress.
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These contaminants can cause deterioration of the concrete itself, but more commonly invade the reinforcing zone and create conditions for steel corrosion. Corrosion is expensive and causes greatly increased cracking. This, in turn, becomes a cycle of deterioration, with more contamination entering the concrete. Delamination and spalling result in structural weakness or failure.
KEY POINT: Reactive contaminants are carried by moisture.
Chlorides, nitrates and other contaminants cannot ‘travel’ in dry form – they are transported when dissolved in water (including water vapour).
IMMOBILISE THE MOISTURE – PROTECT THE CONCRETE
The solution is so simple, it’s hard to believe. If you can stop moisture from entering the concrete or moving about within it, you rob it of any deterioration of the elements it feeds on.
This touches on the point of permeability, as noted above. To truly make the concrete impermeable, its internal porosity matrix must be blocked.
ENTER HYDROGELS
The moisture immobilisation stars … concrete hydrogel treatments! Hydrogel formation can be induced in concrete by introducing colloidal nanoparticle silicate.
This reacts with free lime and moisture within the concrete to form a gel which occupies the porosity and closes the bleedlines.
The most effective way to incorporate this technology is to add it directly to the mix as an admixture.
Immobilising moisture prevents contamination from moving about in the reinforcing zone, protecting the steel.
MEET AQURON 300 ADMIXTURE
- PROTECTION FROM DAY ONE
- INTERNAL WATERPROOFING
- ENHANCED SELF-HEALING
- REDUCED SHRINKAGE CRACKING
AQURON 300 is an environmentally friendly, liquid concrete additive which enhances workability for a better placement experience and provides integral waterproofing and corrosion protection.
Hydrogel technology is the advanced choice for protecting modern concrete.
CONCRETE NEEDS PROTECTION!
Looking at the long-term maintenance costs of a given structure, hydrogel treatments are extremely cost-effective, helping reduce maintenance that would otherwise be required due to deterioration and maximising the planned service life of the structure.
With apologies to all engineers and mix designers upfront – unprotected concrete is unlikely to achieve its planned service life by itself. The dice are loaded against it.
Cost-effective long-term protection is possible – and should be included!
For more learning on this topic, try our on-demand webinar “Concrete – Waterproofing – Durability“.
