Corrosion pits in steel bars embedded in cracked concrete

Here is a short update on what I've found on inspecting the bars after extracting them from the specimens. The first image shows the size of pits found in a specimen with a 'smaller' crack width'.

The second image shows what happens when the crack width in increased. Both specimens were subject to the same amount of salt-dry cycles.

In both cases, the original image dimensions were 5600x4200 microns approx. However, these images have been resized for posting purposes.

There are very interesting findings that will be published in the near future.

Until next time,

Corrosion of steel in concrete

Figuring out what is really going on during corrosion of steel in concrete is no easy task That's why we use advanced experimental techniques to characterize the process. Here's an example:

 

On the left, we see the concrete at the steel concrete interface (dark), in the middle, corrosion products are visible (gray), and on the right, we see the sound steel (white). Characterizing their mechanical properties is our task! Stay tuned for updates! 

Update 1:

How corrosion induced cracking takes place:

Also, different cross sections of the same beam can be observed (top - with PVA fibers; bottom - no fibers):

Visual analysis of corroded bars

I've been working on the analysis of corroded reinforcing steel embedded in cracked concrete. The cubes were mechanically split so the reinforcement can be assessed. All images are taken with the stereomicroscope.

A layer of orange rust can be observed on the steel surface. However, there are still some corrosion free spots. The original image size was aprox. 17000 x 1300 microns*.

This last image shows the thickness of the oxide layer on the steel surface. 

Next step will involve the removal of the rust layers and assessing the size if pits, if any.

Until next time,

* Note: Images were resized for this post.

REPOST: I've just added two images of bars embedded on concrete samples with different crack widths. See the effect of the crack width on the deterioration.

Cheers