Page 15 - report P Lemoine feb 2013c
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that the optical microscope is not able to distinguish the various phases comprising
the matrix, as shown in the SEM micrographs of figure 9.
The mean and standard deviations are shown in figure 15 to 18 and the statistical
analysis is presented in figure 19. Again, focusing on the statistically relevant
comparisons (p-value <0.05), a number of comments can be made.
Firstly, the E and H values for the no Y asrec are significantly lower than for all other
samples, confirming the efficacy of the RoadCem additive. For instance comparing to
Y asrec, the removal of the Y additive results in ~ a 20% drop in E and H values in
the crystal regions and a 60-70% drop of the E and H values in the matrix regions.
Hence the effect of the additive is mostly felt in the matrix regions. Again, here the
roughness of the no Yasrec sample may be a contributing factor.
Examining now the effect of the various treatments on the crystal regions, one
observes a small (~ 10%) but statistically significant drop of the mechanical
properties after N2 and acid treatments. However, the fire treatment does not affect
the E and H values of the crystal regions.
On the matrix regions, the situation is very different, the Y fired sample has higher H
value (~ 50% higher), the two others, Y N2 and Y acid, have the same mechanical
properties than the Y asrec sample.
Obviously, one should again stress that the regions crystals and matrix as identified
by optical microscopy, may not represent homogeneous regions and may correspond
to various crystal or amorphous phases, considering the many mineral constituents
of cement. This is more likely to be the case for the matrix regions as the COV values
are much higher there (34-161%) than in the crystal regions (3-41%). This is also
confirmed by the SEM micrographs of figure 9.
The results however suggest that the fire treatment does not change the mechanical
properties of the individual phases but improve the interfacial bonding and adhesion
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