Clinker 8488 was expected to be the easiest to characterize using optical microscopy because of its more coarsly-grained texture (Figure 19). There were two distinct interstitial phase textures though: a coarse-grained texture exhibiting large lath-like aluminate and blocky ferrite crystals, and a fine-grained texture with extremely fine-grained aluminate crystals within a fine-grained dendritic ferrite. The latter poses difficulties in resolving differences between ferrite and aluminate for optical analyses.
The silicate phases appear to show an anticorrelation across the XRD and optical analyses with XRD values of alite (Figure 20) being slightly greater and belite (Figure 21) slightly lower than the corresponding values from the optical analyses. Optical data (OM-1) show a tighter spread (interquartile range) than XRD for both silicates. This may reflect the coarse-grained nature and relative ease of identification of the silicates in this clinker.
Aluminate and ferrite values (Figures 22 and 23) demonstrate good agreement among XRD and optical data with the exception of optical round robin sets two and three. Again, this may result from the fine crystal size and resulting difficulty in observing this phase and in the experimental approach (magnification) used in performing the optical point count.
Figure 20: SEM backscattered electron image of RM 8488 showing alite (A), belite (B), aluminate (AL), ferrite (F), and porosity (P).
Figure 21: Reflected light image (hydrofluoric acid vapor etch) of a finer-grained interstitial phase texture in some fragments of RM 8488 as well as small ferrite inclusions in alite crystals (white dot-like inclusions). The interstitial phase in this texture clinker will be more difficult to count in the microscope. Field width: 100 µm.
Figure 22: Boxplot for RM 8488 alite
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Figure 23: Boxplot for RM 8488 belite
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Figure 24: Boxplot for RM 8488 aluminate.
Figure 25: Boxplot for RM 8488 ferrite.