Cement is a vital component in the construction industry and is used to make a wide range of products, including concrete, mortar, and grout. The quality and performance of these materials depend on the crystalline structure and chemical composition of the cement used. It is certain that optimizing the cement composition and structure can help in energy savings and benefit the environment.
X-ray diffraction (XRD) is a widely used analytical technique for analyzing the composition and structure of materials, including cement. It is a non-destructive technique that provides valuable information about the crystallographic phases present in cement-based materials, enabling engineers and scientists to optimize the production process and improve the cement’s performance.
X-Ray diffraction is a phenomenon in which the atoms of a crystal, by virtue of their uniform spacing, cause an interference pattern of the waves in an incident beam of X-rays. The crystal’s atomic planes act on the X-rays in the same way a uniformly ruled grating acts on a beam of light. The resulting interference pattern is specific to the atomic structure of a given substance and gives information on the arrangement of the atoms or molecules in the crystal.
In an XRD measurement, a sample is placed in an X-ray diffractometer and is irradiated with a beam of primary X-rays at an angle defined by the relevant diffraction geometry. The Bragg-Brentano geometry is among the most commonly used in powder XRD, otherwise known as XRPD. It relies on moving the X-Ray tube and detector on a circular path to detect the scattered X-rays from a sample and obtain a full diffraction pattern. Provided Bragg’s Law has been satisfied, when the primary X-ray beam interacts with the sample it will diffract and produce a secondary beam that can be acquired by a detector. This yields a diffraction pattern that is characteristic of the unique crystallographic structure of the sample.
Analyzing Cement Sample with XRD
We measured a cement powder sample in reflection using an X-ray diffractometer with Cu Kα radiation (Ni filter). The sample was measured in eleven repeats of 5 min to calculate the reproducibility. Phase quantification was then performed with Profex 1 (BGMN algorithm) using a fundamental parameters approach. Reference structures were selected according to Aranda et.al (2012).2
The sample contained no amorphous additives. Quantification of C3S M1 and M3 modifications was possible and resulted in a standard deviation of 1.2% (1σ). The composition agreed with specifications made in ASTM C150 norm on OPC Type 1.
ASTM C150/C150M-22 is the standard specification for Portland Cement. “The cement covered by this specification shall only contain the following ingredients: portland cement clinker; water or calcium sulfate, or both; limestone; processing additions; and air-entraining addition for air-entraining portland cement. Portland cement of each of the eight types must have the following chemical compositions: aluminum oxide, ferric oxide, magnesium oxide, sulfur trioxide, tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminofernite.”
It is noteworthy that C3S (73.5% and C4AF (10.0%) were high, with low C2S (2.2%) and C3A (6.4%), while the sum of calcium sulphates equaled 6.3%. All values were still in agreement with ASTM C150.
X-ray diffraction (XRD) proved to be an appropriate solution for any process control task in the cement industry, including helping to improve the performance of cement-based materials.
You can see the results, including tables, charts and spectra in the application note: Quantitative analysis of C3S M1/M3 in CEM Ι using ARL X’TRA Companion benchtop XRD.
References and Additional Resources
- 1. N. Döbelin, R. Kleeberg, J. Appl. Crystallogr. 2015, 48, 1573-1580.
- 2. M.A.G. Aranda, A.G. De la Torre, L. León-Reina, Rev. Mineral. Geochem. 2012, 74, 169-209.
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