Page 27 - report P Lemoine feb 2013c

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3. CONCLUSION

Nanoindentation measurements were performed on polished cement samples with

and without RoadCem additive. Two sets of experiments were carried out, with
randomly positioned indents and individually positioned indents on crystal and matrix

regions, as identified by the optical micrographs.

The samples without the additive consistently displays lower Young modulus (E) and
hardness (H) values, ~20% lower on the crystal regions and ~60-70% lower on the

matrix regions.

The effect of the three treatments (ie fire, N2 and acid) on the sample with additive Y

was also analysed. First of all, the N2 and acid treatments resulted in a small
decrease (~- 10%) of the E value in the crystal regions. The fire treatment resulted in

a significant increase (~ +50%) of the H value in the matrix regions and no changes
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in the crystal regions. A previous study used thermal analysis to identify the effect of
PowerCem additive’s as resulting from a pozzolanic reaction decreasing calcium

hydroxide concentration, which do not contribute to the cement strength. The present
results would suggest than the heat treatment improves the interfacial bonding

between phases, yielding to less cracking and toughening of the cement. This

interpretation is consistent with the different mean ratio obtained for the randomly
and individually positioned indents. However, more work, particularly SEM/EDX

analysis would be required to identify the mechanisms of this fire reinforcement.

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