Nanoparticles for high performance concrete (HPC) - Nanotechnology in Eco-efficient Construction - page 44

Table 3.1 Main physico-chemical properties of the commercial additions used
as stated by the manufacturer (Gaitero et al. , 2008)

Particle size
(nm)

Stabilizing
agent

SiO 2 content
(wt%) Name pH Presentation

CS1 30 10 Na 2 O 45 Colloid

CS2 20 10 Na 2 O 20 Colloid

CS3 120 9.5 NH 3 40 Colloid

ADS 1400 - - 95 Powder

All the colloids were dispersed in water, being the amount of the stabilizing
agents < 0.1 wt%.

28 days 28+9 days 28+21 days 28+42 days

4

3

2

1

0

REF CS1 CS2 CS3 ADS

3.4 Evolution of the average segment length. The results were
obtained from the relative areas of the 29 Si MAS-NMR spectra (Gaitero
et al. , 2008).

chains correspond to greater C-S-H stability. The authors concluded that
the addition of nano-silica to cement-based materials can control C-S-H
degradation induced by calcium leaching. However, the benefi ts depend on
the conditions under which nanoparticles are used. Colloidal dispersions
proved much more effective than dry powders in reducing the effects of
degradation.

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3.3 The problem of effi cient nanoparticle dispersion

The most signifi cant issue in the use of nanoparticles is that of effective
dispersion. Vera-Agullo et al. (2009) stated that the use of nanoparticles will
cause a higher degree of hydration in cementitious compounds if higher
nanoparticle dispersion can be achieved. Givi et al. (2010) recorded that a
proper dispersion of nano-SiO 2 particles was achieved by stirring with part
of the mixing water at high speed (120 rpm) for one minute and then adding