Characterizing Components of Cements Using Morphologi G3-ID

Every year, approximately three billion tons of cement is produced. This huge volume accounts for 10% of global CO₂ production and 10-15% of global energy consumption in industry.

The demand for cement is growing with the increasing growth of developing nations, which results in increased CO₂ production and energy consumption. This creates environmental social responsibility concerns and inherent cost.

Approximately 50% of the CO₂ emissions caused by the production of cement is due to the calcination of limestone. Clinker produced from the calcination of limestone is mixed with gypsum to produce Portland cement, which is an important ingredient in most of the concrete and cement available in the market.

However, Portland cement has not always been a key ingredient of cement. Romans used Pozzolan-lime cements to build their structures, most of which still remain standing after 2000 years.

The Pantheon in Rome, Italy is an example of a Pozzolan-lime cement-built structure. Pozzolan cements are easier to work with when first poured as they are slow to set, however these cements develop strength over time and are much stronger than Portland cements.

Pozzolan materials, such as volcanic-ash and fly-ash are increasingly being used in industrial cement production as a replacement for the Portland cement. This not only reduces cost and CO₂ emissions, but also increases the longevity as proven by the Pantheon.

A better understanding of the cement at a particle level could help to increase the benefits and ultimately reduce the costs.

The shape and size of different components in a cement blend can be characterized individually through morphologically directed Raman analysis using the Morphologi G3- ID. The results of the Raman analysis can help to solve production issues, gain a better insight into product development, or compare products and batches.

Methodology

Five different cement samples from two different companies were selected to be tested using the Morphologi G3-ID.

An evaporative method that involves suspending a small aliquot of cement in a solvent and employing ultrasound for dispersion, can be used to disperse cement. Before the analysis, an aliquot of the suspension is spread and left to dry on a microscope slide. Figure 1 shows an example image of this dispersion.

Figure 1. 50x magnification image of dispersion of cement.

A morphologically directed Raman analysis involves conducting a morphological image analysis on the sample first, then information related to shape and size is acquired from the particle images. The positional data obtained from this investigation is employed to automatically return to the target particles from which Raman spectra have to be obtained.

The spectra from pure components are acquired to create a reference library. The particle spectra obtained, are evaluated against the reference spectra and a correlation calculation is subsequently made. A low correlation score indicates no match, while a high correlation score specifies a good match between the particle and reference spectrum.

In this fashion, the Raman spectroscopy results are used to classify the particles as separate components.

Conclusion

A 50x objective was used to perform morphological analysis. The images of touching particles were excluded from the analysis using a post analysis shape filter.

In this study, about 1000 to 2000 particles measuring greater than 3 µm were targeted for chemical analysis, using an acquisition time of 30 seconds per particle.

This information has been sourced, reviewed and adapted from materials provided by Malvern Panalytical.

For more information on this source, please visit Malvern Panalytical.