Penkal Realkalization Solution
Passive Realkalization to Address Carbonation-Induced Corrosion
Passive Realkalization is a repair method for addressing carbonation-induced corrosion through the restoration of high alkalinity within carbonated concrete. The use of a simple temporary surface-applied, as in the case of Penkal Realkalization Solution, allows for a low cost, low complexity solution to the issue.
Outlined below is an introduction to the issue and repair method, along with further details on the success of Penkal as a field viable passive realkalization solution with consistent performance and long-term durability.
What is Carbonation-Induced Corrosion?
Carbonation-induced corrosion is one of the leading causes of concrete failure, causing the corrosion of steel reinforcement within concrete
It occurs as a reaction of the cementitious matrix with atmospheric CO2, resulting in the loss of a high alkalinity within the concrete which otherwise protects steel reinforcement from forming expansive corrosive product.
Carbonation progresses gradually into concrete starting from the surface, forming a ‘front’ which progresses deeper into concrete at a slowing rate. Eventually, the carbonation front will reach the depth of steel reinforcement, changing the surrounding pH and allowing the formation of expansive corrosive products to form and rapidly progress.
Without intervention and remediation, this is an inevitable fate of all steel-reinforced concrete structures.
Further Reading
What is Passive Realkalization
Passive Realkalization works to address carbonation-induced corrosion through restoring a high internal alkalinity within carbonated concrete, thus allowing steel to maintain its passive oxide layer and avoid corroding.
It uses passive transportation mechanisms such as diffusion and capillary action for the migration of alkalis through the concrete carbonation front. In practice, it can be a simple surface-applied coating to carbonated concrete.
The introduced alkalis can then maintain sufficiently high alkalinity within carbonated concrete while being theoretically immune to alkalinity loss through carbonation.
The simplicity of the method provides advantages in the cost and low complexity of its application, potentially widening accessibility of realkalization to many more asset managers when compared to the traditionally higher cost and complexity of electrochemical realkalization.
Further Reading
Over a Decade of Use
Penkal has been used in field applications for over 10 years,
One of our oldest field applications was recently revisited to investigate the long-term durability of the solution following a decade of field exposure and identify if any deleterious reactions took place.
Having obtained core samples and undertaken testing, we found that a high alkalinity throughout the core sample was still maintained 10 years later, with only a minor potential drop of alkalinity from initial application in-line with expectations. Further, no deleterious effects were observed, particularly no increase in microcracking compared to adjacent control culvert cell, nor of alkali-silica reaction product despite the presence of reactive aggregate.
This report was presented at Corrosion & Prevention 2024, which you can find in the link below or under the publications section of the page.
Independently Tested by Transport for NSW
Our formulation was assessed as one of several passive realkalization solutions put forward for trials undertaken by Transport for New South Wales from 2011 and published in 2019.
These trials assessed the performance of the solutions in field applications across multiple sites. The criteria was for the formulation to migrate through to carbonation front depth and demonstrate a high alkalinity increase as determined by quantified and indicator spray methods.
The result was that of all the solutions tested, only Penkal was able to demonstrate successful realkalization to the performance metrics in field applications across all field sites.
A summary report was presented at Concrete 2019, which you can learn more about in the link below.
Procurement
We provide Penkal as a supply-and-apply service, where we both manufacture the material as well as apply it. This provides greater certainty over the success of passive realkalization applications, both in ensuring that the material performs without applicator error alongside ensuring appropriate safety measures are used for application of the corrosive material.
As such, we recommend that Alkyon be specified as specialist contractors for the application of Penkal Realkalization Solution, with us providing advice on procurement including the contracting arrangements that can be undertaken.
Specifying Passive Realkalization
If you’re unable to engage named contractors in your procurement, then we also offer advice on how to specify effective passive realkalization solutions through requiring solutions to demonstrate achievement of basic performance metrics. These performance metrics are based off past literature and understanding of the limitations of solutions in passive realkalization.
All this information is available on our procurement page, linked below.
Limited Warranty
Penkal Realkalization Solution comes with a 10 year limited warranty, where we guarantee that the formulation will both maintain high alkalinity throughout the realkalized concrete, as well as migrate to the carbonation front depth.
In the event that our application fails the guarantee, we’ll provide a new application of Penkal Realkalization Solution to the structure.
For the full terms and conditions of the limited warranty, please contact us.