RM 8487, being the finest-grained of the three clinkers was expected to be the most difficult to analyze using microscopy. Typical microstructures showing a heterogeneous distribution of the silicates, alite and belite, with the belite crystals clustered, may result in the greater uncertainties observed in the optical analyses. The ferrite phase ranged from fine-grained to extremely fine- grained and may in some cases be difficult to distinguish visually from the aluminate. A backscattered electron scanning electron microscope image of the interstitial phases (Figure 13) shows the finely-intermixed aluminate and ferrite. This probably would not be recognized using optical microscopy. The fine-grained distribution doesn't pose difficulties for the X-ray analyses.
Alite (Figure 14) shows reasonable comparability among XRD, OM-1 and RR-1, with RR-2 and RR-3 being somewhat lower and higher, respectively. OM-1 with its 4 points has significantly greater spread (IQ-range) than the more tightly grouped XRD numbers. For belite (Figure 15), the optical points diverge from the XRD yet demonstrate reasonable agreement along themselves, although OM-1 again displays large variance.
Aluminate values (Figure 16) do not demonstrate good agreement among XRD and optical data with XRD values lower than the optical data. Ferrite values show a reverse trend (Figure 17), with XRD values slightly higher than optical. This may result from the fine crystal size and resulting difficulty in seeing this phase using the optical microscope. Alkali sulfate was identified by optical microscopy and was identified in the bulk XRD patterns as arcanite. The XRD and OM-1 data show reasonable agreement.
Figure 14: SEM backscattered electron image of the interstitial phase of RM 8487 shows the inter-mixing of ferrite (F, bright phase) and aluminate (AL, dark) not observable by optical microscopy. Other phases shown here are alite (A), and porosity (P). Field Width: 20 µ m.
Figure 15: Boxplot for RM 8487 alite.
Figure 16: Boxplot for RM 8487 belite.
Figure 17: Boxplot for RM 8487 aluminate
Figure 18: Boxplot for RM 8487 ferrite
Figure 19: Boxplot for RM 8487 arcanite.