Nanoparticles for high performance concrete (HPC) - Nanotechnology in Eco-efficient Construction - page 48

3.4 Conclusions

A review of the literature on the contribution of nanoparticles in HPC
shows the following.

• Nanoparticles may contribute to a dramatic increase in the mechanical

strength of cementitious composites, thus helping the production of
HPC. The related mechanisms are as follows:
- The fi lling of voids in the C-H-S structure, so enabling the production
of concrete of greater density.
- Acting as nucleation centres and contributing to the development of
hydration in Portland cement.

- Reaction with Ca(OH) 2 crystals to produce C-S-H gel. The nanopar-

ticles also act as kernels in the cement paste and reduce the size of
the Ca(OH) 2 crystals.

• The optimal quantity of nanoparticles will depend upon their type and

average dimension.

• Further investigations are needed to determine which nanoparticles are

most effective in enhancing concrete durability.

• Nano-silica appears to control calcium leaching. Colloidal dispersions

are more effective in reducing the effects of degradation than dry
dispersions.

• One of the most signifi cant issues in the use of nanoparticles is that of

effective dispersion. Different authors have used different methods in
order to achieve a high dispersion. However, there is still a need to
search for improved methods. The tools used to assess uniformity of
distribution are largely quantitative (optical microscopy, electron
microscopy and transmission electron microscopy). The validity of the
methods used to date must therefore be confi rmed using quantitative
characterization tools.

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3.5 References

Allwood J, Ashby M, Gutowski T, Worrell E (2011) Material effi ciency: a white
paper. Resources, Conservation and Recycling 55, 362-381.
Bentur A, Mitchell D (2008) Material performance lessons. Cement and Concrete
Research 38, 259-272.
Carde C, Franqois R, Torrenti J (1996) Leaching of both calcium hydroxide and
C-S-H from cement paste: modeling the mechanical behaviour. Cement and
Concrete Research 26, 1257-1268.
Chaipanich A, Nochaya T, Wongkeo W, Torkittikul P (2010) Compressive strength
and microstructure of carbon nanotubes-fl y ash cement composites. Materials
Science and Engineering A 527, 1063-1076.
Chen L, Lin D (2009) Applications of sewage sludge ash and nano-SiO 2 to manu-
facture tile as construction material. Construction and Building Materials 23,
3312-3320.