Not sure if this is any help, but whenever I need an adhesive I turn to Permabond. They seem to know what they are doing and you usually get a free sample of whatever they recomended to you so you can see if it actually works. I hope this pointed you in the right direction...
I dont know... I have never worked with them. I am not saying that Permabond is the only way to go but I can say that they have allways met my needs. And that free sample is a very good thing... you basically never know if the adhesive works until you try it. But Im not sure if they have something for an application like this - maybe its best if you ask them. Or try LORD...
One of the problems with bonding GI is the quality of the plating. If it's electroplated it's likely to be less of a problem than if hot dipped, but of course you may not be able to control that. The other problem is the porosity of concrete and the possibility of moisture migration. A sealant may be advisable. From there you can look at adhesives that are compatible with whatever sealant you choose, but look at thick film acrylics. There are some that are extremely aggressive without much tendency to corrode things. 3M is a good source.
