Dear Beatriz,

There is two types of C-S-H phase, the C-S-H of "first stage", which start to form just seconds after the contact between water and cement. This C-S-H of "first stage" behaves as a layer which slows down the migration of water to the non-hydrated cement. After the dormant period, i.e., during the setting period, the hydration of cement results on the precipitation of the portlandite and C-S-H of "second stage", responsible for the durability and thus the development of the mechanical resistance.

You have to specify which type of C-S-H you want to quantify using X-ray Diffraction

Which software you have used??..x'pert high score is one option; where you can identity the compounds with there respective peaks.

Dear Beatriz Goncalves ,

As amorphous, the analysis is done by subtraction of the crystalline phases.

You can extract the intensity of the peaks from your diffraction, so you need a crystallographic model to work on for any further calculation.

In general, you may associate the unknown phase to a similar structure, in the case of the cited paper, the b-C2S. You may get the CIF for that phase in the Capes crystal structure databank access, via your institution, or in the American Mineralogist website, in the minerals databank.

The calculation you intend to do is based on fitting your XRD with all known phases, subtracting the fitted ones from the experimental XRD. You may have, after all, the amorphous contribution to your diffraction.

That will give you an overview of the amorphous amount, since, for a full, reliable calculation, you need to know which phase is the amorphous one, to be able to calculate the area over the amorphous phase correctly, with the molecular weight of the corresponding mineral phase. Otherwise, you only have approximated values with low or no meaning.

To safely do the analysis, you need more information, let say from a petrographic expert, fluorescence data to give you insights over the unknown specie. If perhaps you know the amorphous phase has Si, Na, it is straight forward to imagine the amorphous is a sort of silicate. The next step is to test several sodium silicate polymorphs and see if you can get some similarities over the amorphous, similarities like 100% peaks are inside the amorphous signal after your subtraction.

In a completely different approach, you may get PDF (Pair Distribution Function) from your sample and treat your amorphous as a scattering phase. Unfortunately, this pathway needs a specific measurement, and the data treatment is not trivial.

Best regards,

WNM

Beatriz Goncalves I read about poor crystallinity for C-S-H-A phases. So, I think you need to consider all the cristalline phases. Like, "Amorphous + Crystalline = 100%". For example, if you know your sample has 50% its mass as crystalline phases it is possible all the other 50% is amorphous. The question is... Only C-S-H is amorphos (the other 50%) or there are other amorphous there too. Like amorphous silicon, for example.

You can calculate how much % of crystalline phase by Rietveld method, but you need all the cif of the crystalline phases. You can download the cif files in the Inorganic Crystal Structure Database (ICSD) in CAPES periodic.

Nilson Ferreira do you think is it possible to calculate the amorphous phase by determining the crystalline % mass?

Dear Beatriz,

There is two types of C-S-H phase, the C-S-H of "first stage", which start to form just seconds after the contact between water and cement. This C-S-H of "first stage" behaves as a layer which slows down the migration of water to the non-hydrated cement. After the dormant period, i.e., during the setting period, the hydration of cement results on the precipitation of the portlandite and C-S-H of "second stage", responsible for the durability and thus the development of the mechanical resistance.

You have to specify which type of C-S-H you want to quantify using X-ray Diffraction

Deep Tripathi yes, I use HighScore.

Dear Professor Wagner Da Nova Mussel,

Thank you so much for sharing your knowledge!

The first approach seemed very interesting to me. I will try to apply it on my cement.

Best Regards,

Beatriz

Jefferson Bezerra Bezerra I already have all the CIFs for the crystalline phases and I got very good Rwp and GOF values in the refinements. Using the external standard method and something like PONKCS I would like to estimate if the entire amorphous fraction is related to C-S-H (which I think it is!).

Dear Nabil Khatib, would it be possible to quantify the two separately? I would like to estimate the amount formed for either or both together (with no specific need for differentiation), but an ideal scenario would be to have an idea of both. I'm doing hydration stops at different ages, so that kind of information would be very good.

I contacted the authors of the two articles, and they shared very interesting information about the subject.

Bergold used the materials to create their patterns, as in PONKCS, but believes that it would not be possible to use the "hkl" reflections information to create a pattern in HighScore.

Suh reminded me that the analysis only indicated the presence of C-S-H, but did not quantify. This indicative analysis of C-S-H was performed in a different way, not in HighScore. He suggested other techniques like TG, 29Si MAS-NMR and thermodynamic modeling (GEMS).