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,

Bending cracks in reinforced concrete cubes

During the course of the M3C4 research, a Modified Wedge Splitting Test (MWST) was employed as the main source of getting controlled cracks in reinforced concrete specimens. For this purpose, we used concrete cubes that contained a recess, where the action of the wedges is applied; and two reinforcing bars embedded in concrete.

After cracking, one can only measure the COD (Crack Opening Displacement) at the concrete surface by means of LVDTs. After some other procedures, we're now able to visualise the shape of the crack inside the concrete cubes.

More results are about to come.
Until next,

Concrete cracking Pt1.

Cracks in concrete cover are definitely a concern for concrete infrastructure. The figure shows cracks propagate not only vertically, i.e. towards the reinforcement, but also horizontally once it has reached the steel bar position.  It is clear that the internal cracked concrete area is far larger the surface crack width. Hopefully, this will be taken into account in future durability design approach.

Until next time,

Jose

Wedge splitting test

Wedge splitting test is a simple test often used in fracture mechanics. Some trial tests were perfomed in the Microlab last week. Here is the result:

Courtesy of our very own (official Microlab) photography maestro CA: