**5. Nano-toxicity**

Among all nanomaterials, the toxicity of carbon nanotubes (CNTs) draws most attention due to their fiber structure and insolubility in lungs, thus significant similarity to asbestos [83]. Evaluation of carbon nanotubes (CNTs) toxicity is an extremely challenging task, since the reactivity of CNTs is influenced by many factors, such as surface area, size and shape, structural defects, purity, chemical composition, solubilization, surface chemistry, and charge [14, 83]. CNTs may cause inflammatory, genotoxic, and fibrotic effects in the lungs, thus contributing to lung cancer [84]. In addition, exposure to CNTs may also lead to skin irritation [84]. When CNTs ingress human cells, they can accumulate in cytoplasm and contribute to cell death [14].

Graphene oxide (GO) and graphene family nanomaterials (GFNs) have a strong antibacterial and antifungal activity. However, they may also negatively affect the biological structures of cells and cause side effects. First of all, the oxidative stress is detrimental to cellular macromolecules: proteins, DNA, or lipids, just to name a few [85]. Moreover, due to sharp edges of graphene, it may damage cell membranes, thus causing the membrane destabilization [85, 86]. It is worth noting that graphene nanomaterial accumulations may be potentially toxic for certain organs, including lungs and liver [85]. Importantly, the toxicity of graphene and derivatives thereof depends strongly on the type of nanomaterial, its shape and size, purity, surface properties, synthesis method and post-producing treatment, dispersion degree, concentration, oxidative state, and functional groups [86, 87].

## **6. Conclusion**

Nanotechnology has a high potential for applications in civil engineering. Nanomaterials such as nano-alumina, nano-titania, nano-silica, nano-magnesium oxide, nano-zinc oxide, silver nanoparticles, carbon nanotubes, or graphene derivatives may have enhanced hydration, microstructure, porosity, and thus mechanical properties and transport-related properties of cementitious composites (**Table 1**). Moreover, nanoparticles can also ensure completely new capabilities of structural composites, namely self-cleaning, self-sensing, and antimicrobial activities. Recent nanotechnological developments in civil engineering open up new avenues for the technological applications of nanomaterials in high-performance cement composites


absence of UV irradiation. It is worth noting that the effect of various forms of TiO<sup>2</sup>

has emerged as a commercially attractive material with optimal photoactivity [79].

mortars [80]. Mortar with the addition of 3% of anatase powder and 2% of anatase suspension

Nanomaterials as conductive materials have also the potential for energy harvesting. Tests on this issue are conducted in many research centers, not connected with structural engineering. Some of them, especially those connected with obtaining energy from mechanical actions [81] and solar [82] activity, have the potential, which could also be considered in large engineering

Among all nanomaterials, the toxicity of carbon nanotubes (CNTs) draws most attention due to their fiber structure and insolubility in lungs, thus significant similarity to asbestos [83]. Evaluation of carbon nanotubes (CNTs) toxicity is an extremely challenging task, since the reactivity of CNTs is influenced by many factors, such as surface area, size and shape, structural defects, purity, chemical composition, solubilization, surface chemistry, and charge [14, 83]. CNTs may cause inflammatory, genotoxic, and fibrotic effects in the lungs, thus contributing to lung cancer [84]. In addition, exposure to CNTs may also lead to skin irritation [84]. When CNTs ingress human cells, they can accumulate in cytoplasm and contribute to cell death [14]. Graphene oxide (GO) and graphene family nanomaterials (GFNs) have a strong antibacterial and antifungal activity. However, they may also negatively affect the biological structures of cells and cause side effects. First of all, the oxidative stress is detrimental to cellular macromolecules: proteins, DNA, or lipids, just to name a few [85]. Moreover, due to sharp edges of graphene, it may damage cell membranes, thus causing the membrane destabilization [85, 86]. It is worth noting that graphene nanomaterial accumulations may be potentially toxic for certain organs, including lungs and liver [85]. Importantly, the toxicity of graphene and derivatives thereof depends strongly on the type of nanomaterial, its shape and size, purity, surface properties, synthesis method and post-producing treatment, dispersion degree, concentra-

Nanotechnology has a high potential for applications in civil engineering. Nanomaterials such as nano-alumina, nano-titania, nano-silica, nano-magnesium oxide, nano-zinc oxide, silver nanoparticles, carbon nanotubes, or graphene derivatives may have enhanced hydration, microstructure, porosity, and thus mechanical properties and transport-related properties of cementitious composites (**Table 1**). Moreover, nanoparticles can also ensure completely new capabilities of structural composites, namely self-cleaning, self-sensing, and antimicrobial activities. Recent nanotechnological developments in civil engineering open up new avenues for the technological applications of nanomaterials in high-performance cement composites

and pigments has been investigated in the case of cement

well as the interaction between TiO<sup>2</sup>

122 New Uses of Micro and Nanomaterials

**5. Nano-toxicity**

**6. Conclusion**

and special structures made out of smart nanomaterials.

tion, oxidative state, and functional groups [86, 87].

[79] as

**Table 1.** Effect of the incorporation of various nanomaterials into building materials.

as well as in structural health monitoring. However, of significant importance is to focus on new solutions, which will facilitate the use of nanotechnology in real industrial-scale applications. Moreover, a key focus for the nanotechnology of structural composites should be ensuring the comprehensive toxicological studies.

[6] Hanus MJ, Harris AT. Nanotechnology innovations for the construction industry. Progress in Materials Science. 2013;**58**:1056-1102. DOI: 10.1016/j.pmatsci.2013.04.001 [7] Sanchez F, Sobolev K. Nanotechnology in concrete—A review. Construction and Building Materials. 2010;**24**:2060-2071. DOI: 10.1016/J.CONBUILDMAT.2010.03.014

[9] Gaitero JJ, Campillo I, Guerrero A. Reduction of the calcium leaching rate of cement paste by addition of silica nanoparticles. Cement and Concrete Research. 2008;**38**:

[10] Farzadnia N, Abang Ali AA, Demirboga R. Characterization of high strength mortars with nano alumina at elevated temperatures. Cement and Concrete Research. 2013;**54**:

[11] Behfarnia K, Salemi N. The effects of nano-silica and nano-alumina on frost resistance of normal concrete. Construction and Building Materials. 2013;**48**:580-584. DOI: 10.1016/J.

[12] Zhang M, Li H. Pore structure and chloride permeability of concrete containing nanoparticles for pavement. Construction and Building Materials. 2011;**25**:608-616. DOI:

[13] Farzadnia N, Abang Ali AA, Demirboga R, Anwar MP. Characterization of high strength mortars with nano Titania at elevated temperatures. Construction and Building Materials.

[14] Siddique R, Mehta A. Effect of carbon nanotubes on properties of cement mortars. Construction and Building Materials. 2014;**50**:116-129. DOI: 10.1016/J.CONBUILDMAT.

[15] Liew KM, Kai MF, Zhang LW. Carbon nanotube reinforced cementitious composites: An overview. Composites. Part A, Applied Science and Manufacturing. 2016;**91**:301-323.

[16] Iijima S. Helical microtubules of graphitic carbon. Nature. 1991;**354**:56-58. DOI: 10.1038/

[17] Iijima S, Ichihashi T. Single-shell carbon nanotubes of 1-nm diameter. Nature. 1993;**363**:

[18] Sindu BS, Sasmal S. Properties of carbon nanotube reinforced cement composite synthesized using different types of surfactants. Construction and Building Materials.

[19] Du H, Pang SD. Enhancement of barrier properties of cement mortar with graphene nanoplatelet. Cement and Concrete Research. 2015;**76**:10-19. DOI: 10.1016/J.CEMCONRES.

2013;**43**:469-479. DOI: 10.1016/J.CONBUILDMAT.2013.02.044

2017;**155**:389-399. DOI: 10.1016/J.CONBUILDMAT.2017.08.059

nanoparticles in concrete and different curing media. Energy

Nanomaterials in Structural Engineering http://dx.doi.org/10.5772/intechopen.79995 125

[8] Nazari A, Riahi S. Al<sup>2</sup>

O3

1112-1118. DOI: 10.1016/J.CEMCONRES.2008.03.021

43-54. DOI: 10.1016/J.CEMCONRES.2013.08.003

CONBUILDMAT.2013.07.088

2013.09.019

354056a0

2015.05.007

10.1016/J.CONBUILDMAT.2010.07.032

DOI: 10.1016/J.COMPOSITESA.2016.10.020

603-605. DOI: 10.1038/363603a0

and Buildings. 2011;**43**:1480-1488. DOI: 10.1016/j.enbuild.2011.02.018
