This page presents a general description on using Electrochemical Realkalisation.  Incorporated within the page is also a tool to calculate the total cost of applying Realkalisation.

Realkalisation is used for carbonated reinforced concrete structures and entails the re-establishment of alkalinity around the reinforcement and in the cover zone.

Certain factors have to be taken into consideration to check if Realkalisation is suitable for the structure in question.  

To find out if  Realkalisation is suitable, activate this tool Check List . 

The Check List tool presents a list of criteria which should not exist within the structure, if Realkalisation is to be used.  If any of the criteria is checked, then it is our recommendation that Realkalisation should not be applied.

Activate this tool, Realkalisation to calculate the cost of using Realkalisation.

The two main inputs expected are the 'Cost of Technique' and 'Area to be Treated'.   The cost relating to the technique can be found by activating the Costing links within the tool.

Multiplication of the two main inputs generates a total cost for the specified technique.  This cost is then added to the 'Fixed Cost' to produce a total cost for applying the technique from conception to finish.

The first and last three inputs which are the ‘Name of the Technique', 'Maintenance Cost' , 'Life of Technique'  and 'Life of Treatment' respectively is essential if the user requires the output generated by this tool for future reference.

The generated output is presented in a report format which contains the specified technique as well as other details relating to the calculation.

The output produced within the Total Cost text area can then be copied and pasted within a report or a document for future reference.

The Application of Realkalisation

The process involves making good the surface of the concrete without having to replace carbonated but otherwise sound concrete.  A typical set up would use a titanium anode, which is fixed to the concrete surface, and a potassium carbonate electrolyte applied.   Steel anodes may also be used and sodium carbonate as the electrolyte.   The electrolyte can be applied in several ways depending on the structure and the element being treated e.g.:

·         Cellulose fibres saturated with the electrolyte sprayed on to the mesh.

·         Ponding.

·         Use of a tank/shuttering cassette system filled with electrolyte.

The treatment is monitored by determining the voltage to current ratio (i.e. nominal resistance).  Once this reaches an approximately constant value the process is considered to be complete.

 
The process is normally verified by splitting cored samples and spraying the freshly exposed concrete with phenolphthalein.   It is also possible to remove dust samples before and after treatment and to analyse these for potassium or sodium content, as appropriate to the electrolyte used.

Following the removal of the anode and thorough cleaning of the concrete, a protective (anti carbonation) coating is often applied.  This will help to keep the concrete in a dry condition and to improve the aesthetics.  A meticulous cleaning process must be followed to prevent crystallisation of electrolyte compounds behind coatings since this will lead to durability problems and coating failure.  In line with good practice, integrity would benefit by the use of a fairing or scrape coat.

Further information on realkalisation can be obtained from the Guidance Document