Page 6 - report P Lemoine feb 2013c

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score the other samples mounted on the apparatus. Typical optical micrographs are

shown in figure 1 for the Y asrec and no Y asrec samples. The no Y asrec sample did
not get polish to the same level of surface smoothness as the other samples. This alone,
would indicate that the no Y asrec sample is more brittle and prone to fragment

dislodgment than the samples with the RoadCem additive.

2..2 Nanoindentation

These experiments were carried out with a MTS XP system using a XP head and

a continuous stiffness measurement (CSM) technique. The system is shown in annex
B. During CSM operation, the AC load was controlled to give 2 nm harmonic

displacement amplitude at 70 Hz. The samples were approached at 20 nm/s for 5000
nm and the contact criteria was for a stiffness of 1000 N/m (~ surface detected when

the indenter is only a few nm into the sample). The samples were allowed to
thermally equilibrate with the instrument until the drift rate was measured to be below

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0.4 nm/s. The indentations were carried out at a constant strain rate of 0.2 s up to
2000 nm depth. Both E and H are averaged from 850 nm to 950 nm depth and
obtained from the measurement of the contact stiffness S ( see annex B for the data

analysis method.

As these cement samples are heterogeneous, one expects these
nanoindentation measurements to give a range of E and H values, as previous

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studies have shown. Hence two batches of experiments were designed. Firstly, the
indents were positioned in 5x5 square arrays, 50 microns apart, so that the various
phases and crystallites were randomly selected (section 3.1). Secondly, using the

optical micrographs as shown in figure 1, the indents were individually positioned

either on the bright crystallites (crystal) or on the surrounding matrix (matrix) (section
3.2). Both experiments were repeated at least twice.

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