Steel protection against corrosion

[Navid.Nik]

Hello everyone,
I have a project in which the customer wants to pour extra concrete (300mm) later on for flooring etc. The structural columns are HSS sections and they have a galvanized coat on it, but I am still worried about the corrosion of steel especially in the first stages of concrete! Do you have any recommendations about how I can protect the column?

 

[jaskamakkara]

You could check these documents out for advice, they pertain to galvanised rebar but the advice should apply mostly to your case.

https://galvanizeit.org/uploads/publications/Galvanized_Rebar_Concrete_Investment.pdf

https://galvanizeit.org/uploads/publications/Specifying_Galvanized_Reinforcing_Steel.pdf

If this is indoors and not exposed to chlorides etc, then the only concern is probably the carbonation of the concrete as it ages. Zinc, however, has much better resistance to the pH lowering effects of carbonation that black steel and is likely not much of a concern.

My other concern would be the performance of the column once it has been cast-in - it looks like at the moment is has a nominally pinned base with a thin end plate, once it's cast-in are you worried that it will start to pick up some moment from the restraint the concrete provides?

 

[Navid.Nik]

Thank you very much jaskamakkara. Yes, exactly! That is also my other discussion with the customer. In the structural calculation report, it is clear that the columns are considered as hinge connection, however, the concrete layer definitely changes this assumption.

 

[liam1369]

Will you not isolate the column from the new concrete? Assume this is a ground concrete slab?

Typically the column will have an isolation joint around it (effectively an expansion joint), therefore, it will not restrain it in any capacity... Is it part of a sway frame or is it just a normal column?

 

[liam1369]

 

[dik]

Unless you are in a heavy corrosion area, the concrete will not detract from the HDG resistance... if that's the case, you have to look at some high build epoxies or something of that ilk... HDG is generally pretty good.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik