Nanoscience and nanoengineering of cement-based materials - Nanotechnology in Eco-efficient Construction - page 15

ostensibly known E and H to determine this area as a function of A c A ( h c ).

Equations for M and H rely on the assumption of a semi-infi nite half-space
and therefore caution should be exercised when testing highly heterogene-
ous materials. In particular, the number of tests should be signifi cantly
increased and the choice of indentation depth should be carefully made
(Constantinides et al. , 2006; Ulm et al. , 2007). The two indentation properties
measured during a test ( M and H ) can then be linked to the elastic M

=

=

M ( E , v ) and plastic H ) properties of the indented materials,

through advanced continuum scale models (Ganneau et al. , 2006). The
extracted mechanical properties of the two types of C-S-H measured on
hundreds of specimens where found to be intrinsic to all cement-based
materials E

= H ( c , ϕ

400-1000 MPa, where the range relates
to the local density variations (nanoscale porosity) observed in cement-
based materials.
Instrumented indentation provides mechanical access to the C-S-H
phases and has been exploited apart from fundamental studies (Constan-
tinides et al. , 2003; Constantinides and Ulm, 2004, 2007; Mondal et al. , 2007,
2008; Vandamme and Ulm, 2009; Vandamme et al. 2010; Chen et al. , 2010;
Ulm et al. , 2010; Xu and Yao, 2011; Song et al. , 2011) but also for the evalu-
ation of chemical degradation phenomena (Constantinides and Ulm, 2004;
DeJong and Ulm, 2007), and the nanomechanical quality of various cement-
based systems like alkali activated aluminosilicates (Nemecek et al. , 2010),
ultra high performance concrete (Sorelli et al. , 2008), fi ber reinforced
systems (Wang et al. , 2009; Sakulich and Li, 2011), nanosilica concrete (Zyg-
anitidis et al. , 2011), and carbon nanotube reinforced concrete (Sáez de
Ibarra et al. , 2006; Konsta-Gdoutos et al. , 2010a). The technique can poten-
tially serve as a nanomechanical screening tool in the search for a more
durable and environmentally friendly material.

= 20-30 GPa and H =

￿ ￿ ￿ ￿ ￿ ￿

Small angle neutron and x-ray scattering (SANS/SAXS)

Small angle neutron and X-ray scattering (SANS/SAXS) are powerful tech-
niques for characterizing the micro- and nanostructures of disordered het-
erogeneous materials on the 1-100 nm length scale (Winslow and Diamond,
1974; Winslow et al. , 1994, 1995; Allen et al. , 1982, 1987; Volkl et al. , 1987;
Allen, 1991; Eichhorn et al. , 1993; Beddoe and Lang, 1994; Allen and Thomas,
2007). Macro structures like polymers, precipitates in metallurgical speci-
mens, biological molecules, micelles and magnetic systems like ferrofl uids
can be identifi ed. The drawback, however, is that SANS requires a neutron
source which is expensive and available only in a handful of laboratories
around the world associated with research nuclear reactors. Around 37
neutron sources exist, the majority of which ( 60%) are in Europe. Neutron

scattering has an advantage over X-ray scattering (SAXS) due to selective

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