V International PhD Student Workshop on Durability of Reinforced Concrete: From Composition to Service Life Design

The proceedings of the PhD workshop in Finland are published! The whole book can be downloaded at: http://www.vtt.fi/inf/pdf/technology/2012/T65.pdf

Rumor has it that the next workshop will be held in Aachen, Germany, in 2013. We'll just have to wait and see if that's true. Till next time!

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

Betondag

Yesterday was the annual "Concrete day" (Betondag) in Rotterdam. The M3C4 presented their research. It was fun! See how Jose's enjoying it! Till next time!

Cracked concrete infrastructure

Betondag 2012 is coming next Thursday November 15th to Rotterdam. A brief, but interesting presentation regarding the influence of cracks on concrete durability will be given by two PhD candidates of the M3C4 project. If interested, don't hesitate to attend the presentations given by PhDs during Betondag.

Until Thursday!

Betondag 2012 + Birthday

M3C4 PhD candidates Branko Šavija and José Pacheco will be have a brief presentation of their work during Betondag 2012 in Rotterdam, The Netherlands. We will be glad to be there and want to meet, discuss or say hi to anybody who is interested in our project. For more information regarding Betondag 2012, please check the program:

http://www.betonvereniging.nl/?id=236

PS. The M3C4 group is happy to congratulate Branko on his 27th birthday. Many more of these to come!
See you

Erik Schlangen at TEDxDelft

For everyone who missed it, here is a link to Erik Schlangen's TEDxDelft talk: (starts about 02:28) http://collegerama.tudelft.nl/Mediasite/Play/082d74bbb0784c09854297f0e202d3671d

PAT-ASR Development of a Performance Assessment Tool for Alkali Silica Reaction: Erik Schlangen in TEDx Talks

PAT-ASR Development of a Performance Assessment Tool for Alkali Silica Reaction: Erik Schlangen in TEDx Talks

UCM3 in Eindhoven

On October 3rd the M3C4 project had its 3rd Users' Committee Meeting, held in TU/e in Eindhoven. Fruitful discussion and more importantly, a green light for the culmination of the project were achieved. Lots of interesting work to be done that will be posted soon!

TU Delft Library is cool!

According to CNN International website, TU Delft has one of the 7 coolest libraries in the world! For more information regarding the remaining six libraries, please visit:

http://www.cnngo.com/explorations/escape/7-coolest-libraries-world-934450

Other concrete blogs

There seems to be an increasing number of blogs dealing with concrete research on the internet. We don't know if we (Microlab) started it, but we like the trend!

For more info, check out the following:

1. www.cementscience.com  - This is a website on research of cement science, a world of cementitious materials by Tan Zhijun.
2. http://www.csla-project.blogspot.com - Concrete Service Life Assessment (The VTT/Tekes Research Project CSL)  will study the characteristics of chloride ion transport in concrete subject to frost attack (surface scaling and internal cracking), and develop models for more reliable service life design approach taking into account the interacted effect of degradation mechanisms. This blog was started by Dr. Miguel Ferreira of VTT, Finland.

Cheers!

Back to work!

The 3rd International Conference on Concrete Repair, Rehabilitation and Retrofitting was held in Cape Town, South Africa last week. The M3C4 team had the opportunity to visit the University of Cape Town and had interesting and successful meeting with colleagues all over the world. Until next ICCRRR,

In the course of our research, a lot of work is done in the lab. It is important to manage the time in relation with other people in the lab, to find space for all those specimens, and, finally, to keep the lab clean! How we do it - a picture is worth a thousand words!

M3C4 in ICCRRR

The M3C4 team is glad to participate in the coming 3rd International Conference on Concrete Repair, Rehabilitation and Retrofitting to be held on September 2-5 in Cape Town, South Africa. Some of the activities include:

• A Committee Meeting of RILEM TC-235-CTC

• A presentation of Modified Wedge Splitting Test, Digital Image Correlation and electrical resistance

• A presentation on using EDS to quantify chlorides in concrete

• Attending the post-conference NDT-Workshop

ICCRRR 2012 is one of the biggest conferences regarding concrete in the world, giving researchers in this field plenty of opportunities to meet colleagues from other countries for interesting discussions and networking. If you are attending ICCRRR 2012 and are interested in the work done by M3C4 don't hesitate to contact us!

Until then..

The Journey

Doing a PhD is no small deal and there are several theories about how to survive while doing it. Here is one. As always, there is still hope!
Have a nice day
:)

J

A day in the life...

The Delft part of the M3C4 team performed some interesting experiments today... The picture says it all, but more details will follow!

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!

SSCS 2012

On behalf of the M3C4 team, Branko took part in the first international conference "Sustainable Strategies for Concrete Structures", held in Aix-en-Provence, France. Dedicated mainly to numerical modelling and its impact on sustainable concrete structures and materials, the conference was a big success. Many significant researchers were there, and presented their work. As our team also presented a paper, usefull feedback from colleagues was obtained. On the other hand, this city has proven to be a very nice and pleasant place for such an event. Following the success of the conference, it is rumoured that the following one is going to take place in Rio de Janeiro, Brazil. The M3C4 team is looking forward to that!

Microdurability Conference, Amsterdam 2012

Results obtained on the course of tM3C4's research were presented and published in the latest Microstructural-related Durability of Cementitious Composites in Amsterdam. Interesting discussion with colleagues and friends ended up in fruitful feedback for the project. More about M3C4's research is going to be published in SSCS 2012 in Aix-en-Provence, France and ICCRRR 2012 in Cape Town, South Africa.
Until soon!

Corrosion induced crack patterns are influenced by many things. Rebar diameter, spacing, cover depth, and boundary conditions all play a role. In the videos, two different scenarios are compared: both specimens have 2 rebars of 10mm diameter, but one has a cover depth of 10 mm, while the other one has a cover depth of 20 mm. Crack growth in both specimens is shown. The difference is obvious.

However, in reality, corrosion rarely causes uniform expansion of the reinforcing steel. Therefore, it is possible that real pressure on the surrounding concrete acts in a different way (Ohtsu and Uddin, "Mechanisms of corrosion-induced cracks in concrete at meso- and macro-scales", Journal of Advanced Concrete Technology Vol.6 , No. 3, 419-429, October 2008):

The effect of different scenarios on the crack patterns in our model is visible in the following snapshots (at 5000 steps- yellow for visibility):

(top to bottom- radial, horizontal and vertical loading scheme, respectively)

It is clear that the loading condition makes a difference in the cracking behavior of the cover. Hope everyone is convinced! Enjoy the holidays!

When the reinforcing steel bar inside concrete corrodes, it starts expanding, since the volume of the oxides that form during the process is higher than the volume of the original steel. It, therefore, exerts pressure on the surrounding concrete, which eventually cracks. To study the mechanism, the lattice model can be used. Here is the result of the first simulation of corrosion induced cracking. Enjoy!

The "rebar effect"

It has been reported in the literature that the buildup of chloride ions occurs at the top of the rebar. This means that the higher chloride concentration can be observed at the top of the reinforcing steel, than at the same depth to the side. Since reinforcement is impermeable to chloride ions, this actually makes perfect sense. Therefore, sampling the chloride ions at the side of the rebar to study, for example, the chloride threshold concentration, can lead to serious errors. This has be proven experimentally by Yu et al. (2007) in their study. So, what is a simple way to check this hypothesis? Well, numerical simulation, of course!

First figure shows the setup. Part of the mesh was was made impermeable to simulate the effect of reinforcing steel, while the chloride can freely penetrate the other side of the sample. The specimen was then subjected to chloride penetration for a certain period.


And here is the result:

Clearly, the phenomenon does occur. And what are the implications for the Round Robin test of the CTC Rilem committee? I guess we'll just have to wait and see!

Reference: H. Yu, W.H. Hartt, Y.P. Virmani, "Effects of reinforcement and coarse aggregates on chloride ingress into concrete and time-to-corrosion: Part 1-Spatial Chloride Distribution and Implications", NACE Corrosion 2007 Conference & Expo

Chloride exposure of cracked concrete

Concrete specimens with controlled crack widths just started to be exposed to a chloride containing solution. This experiment will show how fast chlorides penetrate into concrete on the vicinity of the crack.
More results to be posted soon.

Photo by: B. Šavija

Chloride binding

As chlorides penetrate into the concrete, some of them are physically and chemically bound to the cement matrix. Therefore, only free chloride ions can promote the further penetration. Also, only free chloride ions are responsible for steel depassivation and initiation of the reinforcement corrosion. This effect needs, therefore, to be included in our predictions. The simplest way to do this is to consider binding as a linear phenomenon. Some authors suggested, however, that this assumption is not suitable for a wide range of chloride concentrations. Therefore, non-linear binding isotherms (mainly Freundlich and Langmuir) are often used. First trials with the both nonlinear and linear binding have been performed, and here are the results!

ESEM

Some interesting results were obtained on the ESEM on the past days. There is still a group of samples to be analyzed this week and results seem promising! Part of this work will be published soon. Keep in touch for more upcoming updates.
Adios

Click here to download the January 2012 Newsletter

January has come to an end. Now the M3C4 project is proud to announce the first monthly issue of the Newsletter. On January, some interesting results were found. More information regarding publications or presentations at Conferences will be published soon!

See ya,

Glowing concrete

It seems that concrete properties also include glowing under UV light! Cracks allow aggressive substances to reach into concrete. In this case, the crack pattern is visible when it has been filled with epoxy.


We would like to take this opportunity to wish you success in all your endeavors. Until next time!

Photo by: J. Pacheco