Quantification of amorphous cementitious materials based on CPL using ARL X’TRA Companion Benchtop XRD

Importance of the Topic

Amorphous phases in cementitious materials significantly influence the performance, durability, and sustainability of concrete formulations. Accurate measurement of non-crystalline components such as those present in supplementary cementitious materials (SCMs)—including fly ash, slag, and pozzolans—is essential for optimizing mechanical properties and reducing the environmental footprint of cement production.

Objectives and Study Overview

This application study evaluates a benchtop X-ray diffraction (XRD) workflow employing the partially or not known crystal structures (PONKCS) or calibrated peak list (CPL) approach to quantify amorphous content in clinker–slag mixtures. The goal is to demonstrate accuracy and practicality for routine analysis of decarbonized cement products.

Methodology

Powdered samples of clinker blended with varying levels of amorphous blast furnace slag (20, 30, 50, 70, and 80 wt%) were prepared. Reflection mode XRD data were collected on each mixture using Cu Kα radiation over 10 minutes. The sample containing 48.5% amorphous content served as the calibration reference for the CPL method. Quantitative phase analysis was conducted through Rietveld refinement using the BGMN algorithm and a fundamental parameters approach in the Profex software.

Instrumentation

The Thermo Scientific ARL X’TRA Companion benchtop XRD system was used, featuring:

• θ/θ goniometer in Bragg–Brentano geometry (160 mm radius)
• 600 W Cu or Co X-ray source
• Radial and axial collimators with divergence and Soller slits
• Variable beam knife to minimize air scattering
• Optional integrated water chiller
• Solid state pixel detector (55 × 55 µm pitch) for rapid data collection
• One-click Rietveld quantification and automated LIMS transfer

Main Results and Discussion

The CPL approach yielded amorphous content estimates within an absolute error of 1% compared to nominal values across all mixtures. A linear correlation coefficient of 0.999 was observed, confirming the method’s accuracy and reproducibility. Rietveld fits showed consistent modeling of both crystalline and amorphous phases without requiring an internal standard.

Benefits and Practical Applications

• High accuracy and precision in amorphous phase quantification
• Elimination of internal standards simplifies sample preparation
• Rapid data acquisition and automated processing support high-throughput workflows
• Suitable for routine quality control in decarbonized cement and SCM analysis

Future Trends and Potential Applications

Advancements may include deeper integration with process control systems, expansion of the CPL method to other amorphous phases, and application of machine learning algorithms to enhance phase identification. The approach supports the cement industry’s shift toward greener formulations by enabling precise monitoring of sustainable SCMs.

Conclusion

The combination of the PONKCS/CPL methodology with the Thermo Scientific ARL X’TRA Companion benchtop XRD offers a robust, rapid, and user-friendly solution for quantifying amorphous content in cementitious materials. Its high accuracy and ease of use make it ideal for supporting sustainability initiatives in the cement sector.

References

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