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

Corrosion rates of steel in cracked concrete

Cracks in concrete cover allow fast penetration of aggressive substances such as chlorides, leading to reinforcement corrosion. In the Figure 1, corrosion rates of embedded reinforcing bars in concrete with transverse cracks with widths ranging from 135 to 375 microns are shown. It seems that crack width has an effect on the  evolution of corrosion rate in laboratory conditions.

Figure 1. 

In Figure 2 corrosion potentials are shown, providing indication of the thermodynamical condition of the steel reinforcement. One interesting effect is found on crack width of 217 microns. Although potentials are significantly less noble than the rest, corrosion rates were found to be the lowest of all specimens. It is clear that the experimentation must go on, but so far interesting results have been obtained!

Figure 2. 

More results to be posted soon!