When Concrete Attacks Itself
How SURTREAT Technology Targets Alkali-Silica Reaction
from Inside the Concrete
Corrosion isn't the only deterioration mechanism that can attack concrete from within.
Sometimes, the concrete's own ingredients become the problem.
Alkali-silica reaction (ASR) occurs when reactive silica in certain aggregates reacts with alkalis in the concrete. The reaction produces an alkali-silica gel that absorbs water and swells, generating internal pressure that can cause cracking, aggregate popping and progressive deterioration.
And once the process begins, simply repairing what can be seen at the surface may not address what is happening inside the concrete.
The ASR Triangle
Three conditions are necessary for ASR:
REACTIVE SILICA + ALKALIS + MOISTURE
Remove or control one or more of those conditions and the deterioration mechanism can be addressed.
But existing ASR-affected concrete presents a particular challenge. The reactive aggregate is already inside the structure. The alkalis are already present. Cracking may already have occurred.
That's why SURTREAT approaches ASR as a concrete-system problem rather than simply a crack-repair problem.
The Surtreat ASR mitigation strategy is designed around five objectives:
Reduce the chemical reactivity of the aggregate surface.
Inhibit expansion of the alkali-silica gel.
Strengthen the concrete matrix and reduce porosity.
Seal ASR-related cracks.
Reduce moisture ingress needed to sustain the reaction.
Don't Just Repair the Crack. Address What Caused It.
For existing ASR-affected concrete, SURTREAT uses a sequenced treatment system that attacks the problem in several different ways.
1. TPS XVII — Target the ASR Reaction
TPS XVII is a surface-applied lithium-based ASR inhibitor designed to penetrate concrete and migrate toward the aggregate-cement interface where ASR occurs.
The product is designed to establish a lithium-ion concentration of 100 ppm within the cement phase to mitigate ASR expansion and crack formation.
In other words, the objective isn't simply to cover the evidence of ASR.
It is to reach the environment where the reaction is occurring.
2. TPS XVIII — Strengthen the Damaged Matrix
Stopping or reducing the reaction addresses only part of the problem. ASR may already have produced cracking and deterioration within the concrete.
TPS XVIII is a lithium-silicate treatment designed to penetrate hardened concrete, fill pores and seal cracks while increasing strength and reducing moisture ingress.
This gives the Surtreat approach a second objective:
Mitigate the reaction — then address the concrete it has damaged.
3. SurCoat — Address Larger Cracks
Where larger ASR-induced cracks require treatment, the Surtreat system incorporates SurCoat.
SurCoat is a polymer-modified Portland cement-based material that provides a water-resistant, breathable exterior surface.
In the ASR system, it can also provide something particularly useful: a uniform cementitious surface that allows future crack development to be visually monitored.
4. Repel WB — Take Away the Water
This may be one of the most important parts of the strategy.
ASR needs moisture.
Repel WB is a penetrating silane/siloxane water repellent designed to reduce liquid-water intrusion while allowing the concrete to remain breathable.
Testing reported in the product technical data shows:
91% reduction in water absorption
while retaining
90% breathability.
Rather than trapping moisture beneath an impermeable surface film, the objective is to reduce one of the conditions necessary for continued ASR activity while maintaining vapor transmission.
From the Laboratory to an Airport Tarmac
Theory is important.
Field performance is better.
A dramatic example comes from Sochi International Airport in Adler, Russia.
The airport's newly constructed tarmac developed widespread ASR. Testing by RJ Lee Group identified reactive volcanic porphyry aggregate and found ASR gel, secondary ettringite deposits and ASR-induced cracks extending deep into the concrete.
This wasn't decades-old concrete nearing the end of its expected life.
It was newly constructed pavement experiencing a destructive internal chemical reaction.
SURTREAT implemented a multi-step mitigation program using surface preparation followed by TPS XVII, TPS XVIII, Repel WB and SurCoat.
Then They Cored the Concrete.
The results provide an important demonstration of what a surface-applied treatment can accomplish inside concrete.
Core samples from treated areas measured:
216 ppm lithium at ½-inch depth
134 ppm lithium at 1-inch depth
Both exceeded the project's specified lithium concentration for ASR mitigation.
ASTM bar expansion testing reported expansion limited to:
0.05%
And because this was an operating airport, another question mattered:
Did the treatment adversely affect pavement friction?
Skid-resistance testing conducted by Sochi Airport found no change in surface friction after treatment.
ASR Is an Internal Problem.
The Solution Should Reach Inside the Concrete.
When ASR becomes visible as map cracking, the damage seen at the surface may be only the outward evidence of a reaction occurring throughout the concrete matrix.
Replacing deteriorated concrete may sometimes be necessary.
But where the concrete can be preserved, SURTREAT offers another strategy:
Target the reaction.
Strengthen the matrix.
Repair the cracks.
Control the moisture.
And do it with technologies designed to work within the concrete, not merely on top of it.
Don't just repair what ASR has done.
Address what ASR is doing.
SURTREAT®
Concrete Preservation • Strengthening • Corrosion & ASR Mitigation
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