XRD with Aeris Cement and 1Der: Redefining analytical resilience for the cements of tomorrow

Toward a more sustainable and 1Der(full) life

While the production of new cements presents many obstacles, challenge turns into opportunity with the compact Aeris Cement Edition: made to empower cement producers in setting new standards of excellence, resilience, and innovation. This whitepaper explores how the compact Aeris Cement Edition meets both present and future needs for automated mineralogical analysis with a unique reduced cost of ownership.

1. PRODUCTION OF NEW CEMENTS

Cement materials are complex and everchanging. There are many cement types, but the most widespread are Portland Cement type I and Portland-Limestone Cement type II/A-LL. Markets and regulatory bodies are increasingly advocating for sustainability, and cement producers face a triple challenge: compliance, profitability, and differentiation in the marketplace.

The sustainable way forward involves the reduction of clinker in the cement in favor of newer and larger quantities of Supplementary Cementitious Materials (SCMs), and innovation in the production of clinker itself. Greenhouse emissions are reduced thanks to the use of alternative fuels, and raw materials are increasingly replaced by upcycling waste and by-products from other industrial processes. Through these innovations, the cement industry plays a pivotal role in realizing a truly sustainable and circular economy on a global scale.

A key driver in sustainability innovation is the increase in production costs linked to carbon pricing. It’s become increasingly cost-effective to use new materials, and source materials from more distant locations. However, more varied sources for raw materials lead to more variability in input quality and composition. The result: new risks for kiln operations and for the quality and compliance of novel green cements.

The Aeris Cement Edition and its latest innovation – the 1Der detector – operate in this high-stakes environment. Aeris Cement is a robust industrial diffractometer designed to meet the need for automatic mineralogical analysis in quality and process control. The Aeris is a future-proof solution as any cement materials – old or new – can be fully characterized, including complex cement blends of calcined clays and slags (Figure 1 and Figure 11). 

Figure 1: The outstanding sensitivity of Aeris for SCMs allows a clear quantification of calcined clays in blended cements. Calibrated Rietveld routines with the PONKCS method automatically perform the analysis. Data collected with Aeris 1Der in 10 minutes. Image does not show the full intensities, approximately 10,000.

2. AERIS AND 1Der DETECTOR SPECIFICATION

2.1. AERIS CEMENT EDITION

• The world’s first industrial compact diffractometer
• Truly uncoupled theta-theta 145 mm goniometer with Direct Optical Encoding Systems and Path Tracking Technology
• Minimal ownership costs and required infrastructure are made possible thanks to the 600W X-ray generator. It boasts a long-lasting stable X-ray tube, low energy/water consumption, and eliminates the need for an external chiller. Empyrean X-ray tube with patented CRISP technology to avoid corrosion
• Easy to use thanks to the internal computer, large touchscreen, and intuitive user interface
• Automatic Rietveld analyses performed by control files and RoboRiet
• External sample loader for 51.5 and 40 mm samples for increased safety and quick integration in automated laboratories
• PIXcel1D detector option for accurate analysis of most common blended cements
• 1Der detector for ultimate analysis of any type of material: make your Aeris future-proof
• Prepared for automation with the Universal Automation Interface

2.2. 1Der DETECTOR IN AERIS 

The 1Der is a silicon strip detector with energy resolution below 340 eV and charge-sharing suppression capabilities (Figure 2). 

With an improved signal-to-noise ratio and better quantification of SMCs in blended cements, the Aeris with 1Der provides peace of mind. The radiation Kα and Kβ of iron (fluorescent with copper radiation) is at 6.4 keV and 7.06 keV, and is fully separable from the Kα of copper at 8.05 keV. This ensures the background data is always the same, with any sample. 

Following the same principle, the 1Der detector boosts signal intensities: as the energy difference of the Kα and Kβ radiation for copper is 0.850 keV, it suppresses the Kβ radiation of copper, making the beta filter redundant. Removing this filter increases the speed of high-intensity data collection, further assisted by the large angular coverage of the 1Der detector (3.51°). In this way, the Aeris Cement Edition delivers shorter measurement times, more precise results, and quantification limits that push the boundaries of XRD technology.

Figure 2: The 1Der detector in Aeris provides the ultimate spectral purity and signal-to-noise thanks to its superior energy resolution.

Figure 3: Comparison of diffractograms of a non-fluorescent sample (pure corundum Al2O3) and fluorescent sample (pure hematite Fe2O3) with copper radiation. The scan in green was collected with a detector with poor energy resolution, the other scans were collected with Aeris with 1Der.

3. INDUSTRIAL XRD FOR CEMENT ANALYSIS

3.1. INTRODUCTION TO XRD IN CEMENT PLANTS

XRD analysis is a form of mineralogical and crystalline phase analysis. X-rays probe the distances between atoms, as expressed by the Bragg law. XRD software then compares the measured distances with database values and identifies the various mineral components.

Proven algorithms such as Rietveld refinement can also quantify each mineral in the material by performing least-square regression between the measured and calculated data. Alongside crystalline phase quantification, XRD is the most common technique used in detecting and quantifying amorphous components, by using the PONKCS method and internal/external standard methods.

Most natural and synthetic materials are polycrystalline mixtures: they are made of different crystallographic phases, and the size of each crystal ranges from the nanometer to the micrometer range.

In cement making, the raw meal feed of the pre-calciner and the kiln, as well as the Portland clinker, are instances of such polycrystalline mixtures. The type and abundance of crystalline phases determine the properties of the material, from melting temperature and density to solubility and hydration kinetics. Each of these properties has an impact on every step of the production process. 

Each material and each mineral in it has a story to tell, a lesson to teach, an opportunity to be seized. For example, a large amount of free lime CaO in clinker indicates that the kiln temperature and/or residence time is too low, but it also tells us that making cement with this clinker will result in more heat and expansion. Mineralogical monitoring with XRD shows you what just occurred in the production step and can even predict what will happen in the next. XRD thus ensures that the most is made from every batch – a modern cement plant cannot operate without it.

3.2. NEED-TO-KNOW BACKGROUND ON XRD

While the first commercial X-ray diffractometer was produced by Phillips in 1948, their use in the cement industry became widespread when Panalytical introduced the linear detector X’Celerator in 2001. This detector reduced measurement times from days to under 10 minutes, and the improved speed could provide fast feedback for process control. Until then, mineralogy had to be roughly derived from Bogue calculation on chemical data.

Manual XRD and Rietveld analysis require highly trained personnel, likely working in central laboratories, far from the production environment. Instead, Aeris and Malvern Panalytical cement application specialists provide the know-how from the cement plant itself. 

• Black-box solution: Malvern Panalytical develops and implements the required analytical solution in consultation with the quality manager and laboratory manager. The solution includes an optimized measurement program, customized Rietveld analysis programs (also referred to as control files), and transmission of XRD results to a LIMS system. Black-box solutions are user-friendly, either fully automated or requiring only a few selections via touchscreen (Figure 4).
• Sample preparation: this is the only action the XRD user needs to perform. It is an important link of the analytical chain and it is essential for a good analysis. It needs to be optimized and maintained in consultation with the XRD supplier. Malvern Panalytical provides this support, in the form of SOP documentation and application support from the early stages of commissioning. 
• Analysis standardization: each control file performing automatic Rietveld analysis needs to be properly calibrated by the XRD supplier. Without calibration, the results are not accurate and the plant cannot trust the XRD results, impacting product quality and process efficiency. The calibration can be performed according to international reference materials and standards, as well as local standards. The default solutions for Aeris Cement are calibrated with a multitude of standards, and their accuracy has been verified through multiple test round robins (Figure 5).
• Fine-tuning: this is the process of improving the analysis results provided by the control files. The improvement consists of matching the results of control files with some expected values derived from synthetic mixtures or other analytical techniques (chemical analysis, DSC, synthetic mixtures…). As the Aeris is already calibrated, fine-tuning is only required when sample preparation has not been optimized for XRD or when unique materials are analyzed such as blended cement with supplementary cementitious materials.
• Repeatability: this is expressed as the standard deviation of the Rietveld results when measuring the same press pellets multiple times. It represents the repeatability of the data acquisition and data analysis of the diffractometer. It is different from reproducibility, which also assesses the sample heterogeneity and sample preparation consistency. Repeatability is improved by excellent data quality, robust Rietveld analysis, and longer scanning times (Figure 6). Better repeatability enables plant operators to detect smaller variations in the materials or processes, which allows for more stringent quality and efficiency criteria. 
• Automation: there are many simple, manual operations that can be automated in a cement plant. This includes sample preparation, most of the time sample transportation, and utilization of analytical instrumentation. Automation improves safety, result consistency, and instrument utilization and an accurate process monitoring with big data management, especially in large or remote plants. For an XRD to be automatable it needs an external sample loading mechanism – which can be fed by belt or robot – and proper communication protocols with the automation software. Aeris is fully automatable and can easily be integrated into new or pre-existing automated laboratories (Figure 7).

Figure 4: Mineralogical results of a clinker as visualized in the Aeris touchscreen. The automatic Rietveld routines generate the results without user intervention. Additional customizable outputs such as ‘displacement’ and ‘W alite’ indicate the quality of the sample preparation.

Figure 5: The results accuracy of the Aeris automatic Rietveld routine is verified through round robin tests, and by analysis of reference materials. Each point represents a mineral component of cement. Both major and minor phases are within 2 sigma of the reference values. 

Figure 6: Repeatability values of the Aeris on a clinker sample. Longer measurement times provide better repeatability. The Aeris measurement time can therefore be adjusted based on material throughput and repeatability specifications. Excellent repeatability values are already obtained in 2-3 minutes

Figure 7: In automation, the samples are added to the Aeris external sample changer via belt or robot. The sensors and the Universal Automation Interface guarantee tracking and communication of sample location and position status to the automation software.

4. XRD APPLICATIONS AND SOLUTIONS

4.1. AERIS: IT DOES IT ALL

Thanks to recent innovations in data quality and the extensive know-how and application support of Malvern Panalytical, Aeris Cement Edition provides full mineralogical analysis for process and quality control on any material stream in the cement industry. 

For instance, all cements in EN-197-1 and EN-197-5 can be analyzed in 10 minutes max. Similarly, any new raw material can be analyzed, even when starting at low 2θ angles, as required for clays (Figure 8). All XRD applications in a plant can be performed by a single Aeris instrument. An overview of common XRD applications can be found in the paper “Industrial X-ray Diffraction Analysis of Building Materials”, Reviews in Mineralogy and Geochemistry (2012) 74, 147–165.

Besides quality control of raw clays, the Aeris 1Der can also control the pyro-processing of clays to guarantee proper calcination without the formation of high-temperature phases. To demonstrate the sensitivity of the technique, raw clays and calcined clays were mixed in different proportions (Figure 9). Other examples include quality control of slag and fly ash, where the amorphous amount is determined either by the PONKCS method or by external and internal standard methods.

Full mineralogical quantification of conventional and novel clinkers is the bread-and-butter of Aeris (Figure 4). The control files are validated by continuous round robins and the measurement time and repeatability can be adjusted based on plant requirements (Figure 6). Free lime values can be readily adjusted to the wet chemistry reference values provided by the local plant. Process control using Aeris is also extended to alternative binders such as calcium sulfoaluminate CSA, calcium aluminate CAC, geopolymers, magnesium-based binders, and many more.

It is easy to quantify even low proportions of SCMs in blended cement with Aeris and 1Der. Not only does it rapidly quantify slag and other additives in CEM II blends (Figure 10), but it can also be used for complex novel ternary blends. The low and flat background and improved signal-to-noise allow the simultaneous quantification of calcined clays, slag, and all other mineral components (Figure 11) in CEM II-CM(S-Q), including amorphous phases.

More importantly, the applications and control files are prepared by highly trained and experienced cement application specialists, who will support you with new routines creation, validation, and maintenance of the analytical solution. The solutions they provide are robust and upgradable – meaning no more headaches from supplier changes.

Figure 8: XRD patterns of different source clays (The Clay Mineral Society) collected with Aeris and 1Der. Not all clays are suitable for calcination as SCMs – but Aeris can easily separate the wheat from the chaff.

Figure 9: Aeris XRD patterns of pure clays and pure calcined clays, as well as 80-20 and 20-80 mixtures to simulate calcination with low and high yield. The degree of calcination can be automatically quantified using control files in Aeris.

Figure 10: XRD patterns of slag blended cement and its components. The slag broad contribution to the XRD pattern around 30° 2Θ is readily identifiable and quantifiable using Aeris control files.

Figure 11: XRD pattern of a CEM II/C-M(S-Q) collected in 10 minutes with Aeris 1Der. The pattern contributions of the calcined clays and slag are shown in red and green respectively, quantified using the PONKCS method in Aeris.

4.2. BIG DATA AND MACHINE LEARNING APPLICATIONS

The Aeris Cement Edition usually operates as an industrial black-box solution using Rietveld refinement. But its speed and data quality can also be adapted to laboratory R&D projects, such as failure analysis, development of new binders, and in-situ hydration studies. Furthermore, the huge amount of reliable mineralogical data provided by Aeris can be analyzed by algorithms different than Rietveld. Malvern Panalytical offers HighScore Plus software and training, giving you access to unsupervised and supervised machine learning techniques. These can be applied to the data Aeris collects using the same user interface, to complement and augment conventional phase identification and quantification analysis.

5. CONCLUSION

The Fourth Industrial Revolution is at cement producers’ fingertips with the Aeris Cement Edition. Through quick access to reliable data and mineralogical insights into materials and processes, it enables cement producers to improve quality, efficiency, and profitability. No matter the cement challenges of tomorrow, total mastery over mineralogical analysis is possible with Aeris, the world’s first compact XRD.