Gallery, Projects and General > How do I??

Phospmoric acid.

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Will_D:
Reinforced concrete uses a twisted steel (rusted) steel bar hat may or may not be high tensile. The rust and the twist improve the tensile strength of the rebar in the concrete.

Steel rusts in conjunction with water and oxygen. Concrete is an oxygen deprived environment so as long as the steel is below a critical depth then it cannot rust any more.

Crtical depth is about 27 to 50 mm or so, see here:

https://www.concreteconstruction.net/how-to/construction/placing-reinforcing-steel_o

HTH Will

Malahide.ie

mattinker:
Thanks Will.

If this was a rebar problem, that would apply, but, this is the base of a steel "I" beam pillar, so it's more difficult. I have reinforced with welded and bolted plates and I intend to protect the feet with concrete, but, this will only be the first 5or6 inches, so above, there's nothing and a potential damp penetration. I have found out that Phosphoric acid is used as a concrete cleaner/etcher, so I'll need to do something to separate the phosphoric acid from the concrete. I am thinking either of neutralising the acidity or simply painting to  protect the concrete.

Regards, Matthew

awemawson:
Matthew I very much doubt that the phosphoric acid, once it has reacted  with the rust and dried out, will adversely affect the concrete to any significant degree.

PekkaNF:
This is interesting problem. I am aware remotely only three different structures that might be applicable to this on to a limited degree.

1. In very harsh conditions epoxy coated rebar is used. There are some paints to be used with structures that stick out of concrete. I have heard that there are different types of concrete and some of them (and partly reinfoce materials or expanders or such) can cause incompability problems.  Maybe local shop sells something like this and you can contact someone.
https://www.rustoleum.com/product-catalog/industrial-brands/industrial-choice/spray-paint/rb1600-system-rebar-epoxy-spray-paint

Once I had some problems with a testpiece and one particular one-mix two component epoxy and after a day the chemist on their development department called me and told that he thinks he knows what the problem was and told me how to avoid it.

2: Here in building industry hot galvanized mounts are used when something is attached onto concrete. hardware sores sell J-bolts and pilar brackets that the other end is stuck into concrete and then cast. There is screw that is used to level the pilar bracket.

4: machine building in industrial buildings inside: Long bolts are welded into bottom rebars and stays added. These bolts are covered with elastic material to prevent them from sticking into concrete 8that would be bad for tenssioning (torquing bolt), concrete is cast, then end of the bolt is painted and grouting is cast to level. Then baseplates are leveled and injection epoxy layer is injected between grouting and base plates. Finally bolts are torqued and then concrete will shrink 400 years and after that starts eroding.

* Typos due not using glasses

mattinker:

--- Quote from: awemawson on November 26, 2019, 12:36:41 PM ---Matthew I very much doubt that the phosphoric acid, once it has reacted  with the rust and dried out, will adversely affect the concrete to any significant degree.

--- End quote ---
Thanks Andrew
I think your right! I just don't want to take a risk!!

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