If I have a thin section with chemically reactive components (for example concrete with reactive aggregates prone to Alkali Aggregate Reaction); will I able to draw any inferences from the images taken with certain intervals of time… let us say 6 months, 1year and 2 years etc.
First of all; is that possible to make such live thin sections.
Are there any other methodologies for similar studies?
In current practice, generally these types of studies are carried out on specimens sampled at specified intervals of time or from a structure of known age.
Dear Mohammed,
The idea of a living thin section, where you can read direct changes in the structure and the alteration of the substances involved is exciting, but not realizable in my experience, why? The alkali silica reactions are triggered by fluid transport and volume increase of the affected phases. For this purpose, a certain space, a certain volume (at least 1 decimeter) is required, which can then experimentally be traversed by the fluids along grain boundaries and cracks. This surrounding mass is completely missing in a thin section. Therefore significant changes of the original structure are not to be expected. A covered thin section forms a closed system. A thin section with freely accessible surface is influenced by the humidity, and is at least partially sealed by impregnation agents. Therefore, possible chemical reactions are significantly reduced and no longer quantifiable. For further information, I have attached a publication from our working group on this topic.
Best regards
Guenter
Dear Dr. Guenter Grundmann Thank you for the quick answer. Alkali Aggregate Reaction was just an example I quoted. As you correctly mentioned the volume of phases participating and other driving forces may play critical role in chemically evolving systems. Thank you for the attached manuscript as well.
Hey Mohammed,
Maybe this idea helps. You could use NMR for your purpose, a MOUSE instrument (MObile Universal Surface Explorer). It's portable, you can reach a thin section of your material, in situ. It's noninvasive, so it doesn't disturb your evolving system, and you can even use the system as is, with the ground water or whatever other liquid is in the pores of your material. I've been working with fresh cement paste, but I'm sure you can also do this on old cement based materials. Unfortunately, I can't send you any of my articles using the MOUSE, as I'm waiting for them to get published, but I can point you towards a nice review, B. Blümich, J. Perlo, F. Casanova, B. Blu, J. Perlo, F. Casanova, Mobile single-sided NMR, Prog. Nucl. Magn. Reson. Spectrosc. 52 (2008) 197–269. I hope it helps.
Kind regards,
Andrea
Dear Ms. Andrea Crețu, Thank you very much for the answer. It looks very interesting and promising. And I was able to go through one of the related article.
https://www.researchgate.net/publication/235921753_Mobile_NMR_for_surface_analysis
Could you please clarify the specimens you used (or generally to be used) for the analysis?
As discussed by Guenter Grundmann in the previous answer, can we use thin sections for the Mobile NMR. Or shall we use a relatively thick representative (chemically active section).
Since you worked with the technique, your suggestions may be highly useful.
And I hope your publication will come soon. All the very best.
Dear Ms. Andrea Crețu ,
I went through the review by Blümich et al.
Very informative.
However, still need to find a suitable methodology to use it for concrete materials.
Thank You.
Dear Mohammed, sorry for the late reply, I didn't get notified that you answered. My publication is still pending (yay for the publishing process), but of course I can tell you about my samples. It all depends on the settings you use for your machine. I'm not an expert in NMR, so I can't tell you how to set this up, but I know that you can change the maximum height you can reach with the sensitive area of the MOUSE if you want to. You can do such measurements on any material that contains water (especially cement). I used it to monitor samples set on top of the magnet/RF coil unit while they were hydrating. I only did CMPG measurements at set time intervals of one hour and then one day. If you have a piece of concrete that's in a controlled environment, you can do measurements every two weeks or so, at a specific depth or several depths, then compare the resulting curves or do more complex fitting of the data. I don't know how friendly you are with NMR methods, maybe ask around your university for people who do low-field NMR and might explain more.
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