Civil Engineering Reference
In-Depth Information
Popular metallic MNMs used in construction include copper and silver.
The most common use for Cu NPs is incorporation into steel to improve
weldability and provide resistance to corrosion (Ge and Gao, 2008). Like
TiO
2
, Ag NPs are also strong antimicrobials and can be used in paints and
wall coatings to inactivate pathogenic microbes (Kumar
et al.
, 2008). Silver
NPs can also be utilized indoors since their antimicrobial activity is not
photo-assisted. This is particularly useful in hospitals and childcare facilities.
Copper and CuO have been shown to have antimicrobial properties as well,
but this may be a species-specifi c phenomenon (Ruparelia
et al.
, 2008).
Nonetheless, Cu and CuO are sometimes used as a biocide instead of silver.
Many MNM alloys also have a niche in construction. These materials
include metallic carbon or nitrogen compounds, QDs, and nanoclays. When
uniformly dispersed through a steel matrix, metallic carbonitrides increase
strength against creep by two orders of magnitude (Taneike
et al.
, 2003).
Similar to metal oxide NPs like TiO
2
and SiO
2
, QDs can also be used in
windows to control interior light by being translucent in the visible spec-
trum to increase intensity and being refl ective in the infrared spectrum to
impede thermal transfer (Anikeeva
et al.
, 2009). A variety of non-metal
polymeric NPs are used in matrices as constituents in windows, antibacterial
coatings, and nano-clay composites (Chauhan
et al.
, 2006). Incorporation of
polymeric MNMs can increase tensile strength and fl exibility of construc-
tion materials (Podsiadlo
et al.
, 2007). Nanoclays and polymer-clay nano-
composites are used as fi ller materials or to increase compressive strength
(Podsiadlo
et al.
, 2007). When nanoclays are incorporated into wood/plastic
composites, the resulting material gains enhanced mechanical properties
and improved rot-resistance (Faruk and Matuana, 2008).
7.2
Potential nano-hazards of manufactured
nanomaterials (MNMs) utilized in construction
The unique characteristics of MNMs that allow them to enhance construc-
tion are frequently the very source of their hazardous properties. Carbon-
based, metal-containing, and non-metallic MNMs, including carbon
fullerenes, metal oxide and metallic NPs, quantum dots, and nanoclays, have
been shown to have toxic effects in a variety of studies (Shiohara
et al.
, 2004;
Lam
et al.
, 2006; Buzea
et al.
, 2007; Hagens
et al.
, 2007; Karlsson
et al.
, 2008;
Xia
et al.
, 2009; Zolnik
et al.
, 2009). It has been further suggested that MNMs
have the potential to modulate the immune system in unpredictable ways
(Dobrovolskaia and McNeil, 2007; Dwivedi
et al.
, 2011). It is useful to know
that a given class of nanomaterials frequently shares its toxicological traits
with many of its members. Table 7.1 shows the properties of each MNM
class that are frequently associated with their toxic effects. Table 7.2 gives
the reverse view: shown are the nano-hazards of MNMs frequently utilized
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