Does Rebar Rust

[jar546]

Here is a great video that not only discusses the name of the thread but goes on to other rebar related issues.

 

[Mark K]

One reason that the codes do not recognize the non steel reinforcing is that they do not have the ductility of steel rebar. If rebar has proper anchorage it does not fail when the yield strength is reached. Instead the rebar continues to stretch.

The pictures of the failed test specimens show that the rebar was not properly anchored. In a properly anchored beam where the rebar was allowed to yield you would see a different cracking pattern.

Yielding serves several purposes.

A beam or slab that does not have ductile reinforcing is likely to fail suddenly when over loaded while ductile reinforcing will allow the member to deflect noticeably thus allowing people to take action before failure.

Ductile rebar and ties will allow compression members such as columns to resist severe overloads thus preventing catastrophic failures even if the member is severely damaged.

When designing to resist earthquake loads the yielding of the rebar is used to dissipate energy and allow the structure to survive without collapsing.

The point is that you should follow the code requirements that require the use of steel rebar.

Corrosion is a concern but experience has show that under normal circumstances corrosion can be managed and the members can have a long life.

Rebar with rust should not be rejected if the rust is tight and if there is no reduction in cross sectional area.

 

[jar546]

One reason that the codes do not recognize the non steel reinforcing is that they do not have the ductility of steel rebar. If rebar has proper anchorage it does not fail when the yield strength is reached. Instead the rebar continues to stretch.

The pictures of the failed test specimens show that the rebar was not properly anchored. In a properly anchored beam where the rebar was allowed to yield you would see a different cracking pattern.

Yielding serves several purposes.

A beam or slab that does not have ductile reinforcing is likely to fail suddenly when over loaded while ductile reinforcing will allow the member to deflect noticeably thus allowing people to take action before failure.

Ductile rebar and ties will allow compression members such as columns to resist severe overloads thus preventing catastrophic failures even if the member is severely damaged.

When designing to resist earthquake loads the yielding of the rebar is used to dissipate energy and allow the structure to survive without collapsing.

The point is that you should follow the code requirements that require the use of steel rebar.

Corrosion is a concern but experience has show that under normal circumstances corrosion can be managed and the members can have a long life.

Rebar with rust should not be rejected if the rust is tight and if there is no reduction in cross sectional area.

Thank you for your well thought out post. I appreciate it and hope others do too.

 

[ADAguy]

Yes, but be sure to check the manufacturter's coding to be sure it meets standards.
Also be careful with onsite storage before use.

 

[Mark K]

What is meant by "manufacturers coding"? Rebar is rolled with standard makings that indicate the grade.

Onsite storage should not be a problem as long as you do not run a truck over it and bend it. In most cases rebending rebar is not recommended unless specially heated. Check with the engineer.

Unless it is on site for a long time the rust will be minor and any loose rust can be removed with a wire brush.​

 

[ADAguy]

ok smarty, "grade stamps" memory failed me, duh!

 

[mark handler]

I would be more concerned with the growing global threat of radioactive scrap metal.
https://www.seattletimes.com/nation-world/the-growing-global-threat-of-radioactive-scrap-metal/
U.S. Environmental Protection Agency. A 2005 study of more than 6,000 Taiwanese who lived in apartments built with radioactive reinforcing steel from 1983 to 2005 showed a statistically significant increase in leukemia and breast cancer.
January 17, 1984, Los Alamos National Laboratory (LANL) had detected some radioactive reinforcing bars (rebar) in a shipment mistakenly delivered to LANL. The rebar was determined to have been inadvertently contaminated with cobalt-60 (Co-60) and that the shipment had come from a supplier in Mexico through a broker in Phoenix, Arizona.
Much of the rebar was also delivered to home builders in the southwest US.

 

[mtlogcabin]

That is a very interesting 7 year old story. I wonder if it has gotten better or worse for materials coming into the USA

 

[mark handler]

Hopefully better. The Customs people are installing Radiation detection systems at the points of entry to prevent "dirty Bomb" material from entry to the US.
But how much is here, installed, undetected?