Corrosion protection & rehab of PTcables

[jcraig]

I am researching the use and specification of polyurethane grouts for corrosion protection and rehabilitation of post-tensioned cables in bridge beams, as well as stay cables. I have the following questions:

I am aware of electrochemical (rusting), stress-corrosion cracking and hydrogen embrittlement as three types of cable corrosion, but to what extent can microorganisms and fungus cause damage or affect the durability of the cables. Should any antibiotic or antifungal additives be added to the grout as a precaution?

Are there case histories where polyurethane grouts have been used successfully in lieu of cement grout encapsulation?

Where can I find more information and a good case study of cable rehabilitation techniques such removal of old grout and new grout injection methods?

I appreciate any information or ideas.

 

[Ingenuity]

jcraig,

Polyurethane (PU) grouting to UNbonded (greased and sheathed) PT tendons to older building structures has been undertaken in Canada and the USA on a few projects. It is a patented technology by JAMOR Engineering of Calgary.

I have a corrosion and metalurgical report from a lab in Canada that studied corrosion rates with PU grouted steel tendons with results/data of probably 5+ years.

FYI - I am not associated with the JAMOR Company in any way, I am just aware of the technology because I get involved with repair and replacemnt of PT tendons.

I am not aware of PU being used on PT tendons for bridges nor cable stays.

A good document on corrosion related issues to prestressing is ACI 222.2 Corrosion of Prestressing Steels. It ddiscusses HE and SCC.

Seems that your post is more related to regrouting (with PU) to existing cement grouted tendons/stays that possibly have voids, defective grout, etc. I am aware of some very very low viscosity epoxy resins being used successfully to fill grout voids in tendons BUT you first have to locate the voids possible using Impact Echo or other NDT techniques.

I think it will be quite a challenge to remove the old grout in a BONDED internal tendon, especially if it was cementitiously grouted.

If you can give me a bit more info I may be able to assist a bit more than the above.

 

[jcraig]

Thank you for your response. I have been busy in our labs and not able to respond until now.

We have actually been supplying a two-part component polyurethane chemical grout for years in ecapsulated post-tension cable rehab and installations. It appears to provide a more watertight seal against corrosion than traditional cementatious grout.

I have also recently found an article about fungal and microbe corrosion of PT cable that was very enlightening, which has now lead to testting of our products with anti-microbal/fungal additives such as Ultrafresh and Microban.

Here are the links if you would like I found:

http://www.electrochem.org/publications/interface/winter2001/IF12-01-Pages44-48.pdf

http://www.ultra-fresh.com/tra/

http://www.microban.com/