Raman spectroscopy of cement - Class G oilwell cement
Oilwell cement is specially formulated for the extreme conditions required, i.e. high temperatures and pressures. It typically contains low quantities of C3A and free lime (CaO). Understanding the early stages of oilwell cement hydration is crucial to its application. Raman microscopy combines the spectroscopic capability with high spatial resolution, allowing us to study hydration processes in-situ. Figure 6 shows a Raman spectrum obtained from a fresh class G cement powder and from a paste hydrated for 1 day.
Figure 6 Raman spectra of fresh class G oilwell cement and a paste hydrated for one day.
Environmental Scanning Electron Microscopy is also very well suited for examination of these kinds of materials, allowing analysis without the necessary application of a conductive coating.
Figure 7 shows a feature (a), micrograph, and (b) its corresponding EDX mapping) on the surface of an oilwell cement after hydration by water vapour for three months. The 'star-like' feature was identified as ettringite.
a) 
b) 
Figure 7 Hydration products on an oilwell cement: fibrous ettringite (a) and an EDX mapping (b) on this feature.