Improving the quantitative analysis of cementitious materials by solid state NMR

• Applicants: Privatdozent Dr.-Ing. Frank Bellmann; Dr. Harald Hilbig; Professor Dr. Dietmar Stephan
• Subject Area: Construction Material Sciences, Chemistry, Building Physics
• Term: from 2021 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 440340258

Traditionally, cementitious materials are analyzed X-ray diffraction (XRD) to obtain qualitative and quantitative information about the individual phases contained in the sample. The use of this method is routine in most labs and based on long-term experience. It is highly useful for crystalline materials whereas analysis of amorphous materials is complicated. Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy has been proven to be a suitable tool to analyze cementitious materials containing amorphous and crystalline materials. Such analytical capabilities are demanded by the increasing use of non-crystalline materials by the cement industry such as slags, calcined clays and fly ashes. The qualitative identification in the NMR spectra is based on the chemical shift data for the individual substances and the quantitative information is associated to the relative intensity of those resonances. While the basic ideas for the acquisition and evaluation of NMR spectra are very well known, a number of details must be addressed that seriously complicates the extraction of reliable quantitative data. The analysis is often based on individual experience and varies between the laboratories. To address this situation, a group of academic institutions intends to focus on this problem. This refers to the complete analytical procedure including the production of suitable samples, adoption of best acquisition parameters, recommendation for the deconvolution procedures and the post treatment of the data to extract the concentration of the individual phases in the sample. We intend to provide test samples and improved routines also to other partners beyond our network for further practice and education. The cooperation will also allow identification of systematic and random errors and provide information about the standard deviation of the results. It is expected that this work will foster the application of NMR for quantitative analysis of cementitious materials in the anhydrous and hydrated state. NMR spectroscopy is a rather complicated analytical method and such efforts demand a number of efforts beyond a simple data acquisition and this includes: improved strategies to account for the different relaxation times, selective dissolution methods to extract the individual resonance shapes and other details. This work will mainly focus on 29Si NMR. Other NMR isotopes that will be studied are 27Al and 1H.The efforts are conducted in close cooperation with Prof. Jorgen Skibsted from Aarhus University in Denmark, the leading expert in the field of NMR spectroscopy of cementitious materials.

• DFG Programme: Research Grants
• International Connection: Denmark
• Cooperation Partner: Professor Dr. Jorgen Skibsted