Safety issues relating to nanomaterials for construction applications - Nanotechnology in Eco-efficient Construction - page 128

7.1.1 Naturally occurring nanomaterials
Nanomaterials are not necessarily manmade; many are created naturally
through a variety of weather and geological phenomena. These include
volcanic ash, ocean spray, forest fi re smoke, and clouds (Goldman and Cous-
sens, 2005). Some of these naturally occurring nanomaterials, such as nano-
clays, are mined and have applications in composite building materials
(Faruk and Matuana, 2008; Basak et al. , 2010). Many nanoparticles (NPs)
can also be found in biological systems such as lipoprotein particles (German
et al. , 2006) and biogenic magnetite in the human brain (Kirschvink et al. ,
1992). Generally, these nanomaterials are created incidentally, like in the
case of volcanic ash, or for an evolutionary purpose, such as the transport
of fat molecules by lipoproteins.

7.1.2 Engineered nanomaterials and their use
in construction

Unlike naturally occurring nanomaterials, engineered nanomaterials are
typically manufactured for specifi c properties. MNMs can be tailored for
application to a wide range of products including personal care products,
medical devices, and electrical conductors (Derno et al. , 1995). For example,
nano-TiO 2 has been used in sunscreens and lotions as a UV absorber
(Contado and Pagnoni, 2008). Other consumer products such as toys and
clothing use Ag NPs as an antimicrobial agent (Benn et al. , 2010). In the
medical fi eld, numerous advances in imaging and drug-delivery systems
have been made using MNMs (Sosnik et al. , 2010; Parveen et al. , 2012).
Quantum dots (QDs) are unique metallic nanomaterials with advanced
electronic properties used in transistors and solar cells (Leobandung et al. ,
1995; Nozik, 2002).
In the construction industry, MNMs have been used to improve the
mechanical strength of concrete and steel, fi reproofi ng of windows, electric-
ity generation, and corrosion resistance (Zhu et al. , 2004; Mann, 2006;
Abraham et al. , 2008). Manufactured nanomaterials are used in a wide
range of construction applications from concrete and steel to glass windows
and paint (Irie et al. , 2004; Sobolev and Gutierrez, 2005; Ge and Gao, 2008;
Kumar et al. , 2008; Rana et al. , 2009; Raki et al. , 2010). There are several
distinct categories of potential benefi ts that may be gained from the use of
these materials such as improved safety, user convenience, enhanced life-
time of the structure, and increased ease of construction. It is also possible
for one nanomaterial to provide various benefi ts spanning multiple benefi t
categories. For example, SiO 2 -NPs incorporated in window glass confer
fl ame resistance, anti-refl ection, and self-cleaning, thus improving both
safety and auxiliary properties (Mann, 2006; Rana et al. , 2009).

￿ ￿ ￿ ￿ ￿ ￿