Analysis of cement related materials

Importance of the Topic

Rapid and accurate determination of major and minor oxides in cement raw materials and products is essential for quality control, process optimization, and regulatory compliance in the cement industry. X-ray fluorescence (XRF) offers a non-destructive analytical route with minimal sample consumption, making it a cornerstone technique for routine and research-oriented analyses.

Objectives and Study Overview

This application note evaluates the performance of the Thermo Scientific ARL OPTIM’X wavelength-dispersive XRF spectrometer for cement and related materials. Key goals include:

• Comparing two sample preparation methods: pressed pellets versus lithium borate fused beads.
• Establishing calibration curves for major oxides (e.g., CaO, SiO₂, Al₂O₃) and minor constituents (e.g., Na₂O, MgO).
• Assessing limits of detection, accuracy (standard error of estimate), and repeatability/reproducibility over short and extended time frames.

Methodology and Instrumentation

Sample Preparation:

• Pressed Pellets: Powders milled to below 50 µm, then pressed at 20 tons for routine, fast analysis.
• Fusion Beads: Samples fused with lithium tetraborate/metaborate at a 1:3 sample-to-flux ratio to eliminate mineralogical and particle size effects.

Instrumentation:

• ARL OPTIM’X WDXRF with low-power Rh anode tube, no water cooling required.
• SmartGonio™ optical system covering Z=13 to Z=92, plus fixed channels for Mg and Na.
• OXSAS software for multi-variable regression calibration and data management.

Main Results and Discussion

Calibration and Detection Limits:

• Calibration ranges span major oxides (e.g., CaO 28–67 %, SiO₂ 20–23 %) and trace levels (e.g., Na₂O 0.04–0.32 %).
• Standard error of estimate typically below 0.2 % for major oxides; Na₂O SEE = 0.011 % using fused beads.
• Limits of detection for pressed pellets and fused beads are comparable; Na₂O LOD as low as 25 ppm (540 s).

Precision and Reproducibility:

• Short-term repeatability (11 runs) yields relative standard deviations below 0.05 % for major oxides.
• Long-term stability over 60 hours (120 runs) maintains deviations under 0.1 %.
• Three-day reproducibility on cement pressed pellets meets industry tolerances with total counting times of ~200 s.

Benefits and Practical Applications

• Pressed pellet preparation is rapid and cost-effective for routine QA/QC analyses.
• Fusion bead method ensures superior accuracy when dealing with diverse mineralogical matrices.
• Parallel use of SmartGonio and fixed channels reduces analysis time while preserving precision, ideal for high-throughput laboratories.

Future Trends and Potential Applications

• Integration of automated sample feeders and robotics for fully unattended operation.
• Advanced multivariate algorithms for improved interference correction and lower detection thresholds.
• Extension to in situ and portable XRF systems for field measurements of raw materials and clinker.

Conclusion

The ARL OPTIM’X WDXRF spectrometer delivers reliable, high-precision oxide analysis for cement-related materials. Pressed pellets offer rapid workflows and low detection limits, while fused beads eliminate sample heterogeneity effects for optimal accuracy. Consistent repeatability and reproducibility confirm suitability for routine and research applications within the cement industry.