Self-Sensing Concrete Nanocomposites for Smart Structures
In the field of civil engineering, Structural Health Monitoring is a topic of growing interest. Effective monitoring instruments permit the control of the working conditions of structures and infrastructures, through the identification of behavioral anomalies due to incipient damages, especially in areas of high environmental hazards as earthquakes. While traditional sensors can be applied only in a limited number of points, providing a partial information for a structural diagnosis, novel transducers may allow a diffuse sensing. Thanks to the new tools and materials provided by nanotechnology, new types of multifunctional sensors are developing in the scientific panorama. In particular, cement-matrix composite materials capable of diagnosing their own state of strain and tension, could be originated by the addition of specific conductive nanofillers. Because of the nature of the material they are made of, these new cementitious nano-modified transducers can be inserted within the concrete elements, transforming the same structures in sets of widespread sensors. This paper is aimed at presenting the results of a research about a new self-sensing nanocomposite and about the implementation of smart sensors for Structural Health Monitoring. The developed nanocomposite has been obtained by inserting multi walled carbon nanotubes within a cementitious matrix. The insertion of such conductive carbon nanofillers provides the base material with piezoresistive characteristics and peculiar sensitivity to mechanical modifications. The self-sensing ability is achieved by correlating the variation of the external stress or strain with the variation of some electrical properties, such as the electrical resistance or conductivity. Through the measurement of such electrical characteristics, the performance and the working conditions of an element or a structure can be monitored. Among conductive carbon nanofillers, carbon nanotubes seem to be particularly promising for the realization of self-sensing cement-matrix materials. Some issues related to the nanofiller dispersion or to the influence of the nano-inclusions amount in the cement matrix need to be carefully investigated: the strain sensitivity of the resulting sensors is influenced by such factors. This work analyzes the dispersion of the carbon nanofillers, the physical properties of the fresh dough, the electrical properties of the hardened composites and the sensing properties of the realized sensors. The experimental campaign focuses specifically on their dynamic characterization and their applicability to the monitoring of full-scale elements. The results of the electromechanical tests with both slow varying and dynamic loads show that the developed nanocomposite sensors can be effectively used for the health monitoring of structures.
Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1124185Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF
 N. Muto, H. Yanagida, T. Nakatsuji, M. Sugita, Y. Ohtsuka, Y Arai "Design of intelligent materials with self-diagnosing function for preventing fatal fracture" Smart Mater. Struct. vol. 1, no. 4, pp. 324-329, 1992.
 P-W. Chen, D.D.L. Chung, "Carbon fiber reinforced Concrete for smart structures capable of non-destructive flaw detection" Smart Mater. Struct, vol. 2, pp. 22-30, 1993.
 P. Mondal, S.P. Shah, L.D. Marks, "Nanoscale characterization of cementitious materials", ACI Mat. J. vol. 105, pp. 174-179, 2008.
 S.P. Shah, M.S. Konsta-Gdoutos, Z.S. Metexa, P. Mondal, "Nanoscale Modification of Cementitious Materials", In: Nanotechnology in Construction 3, Z. Bittnar et al Eds. Springer, 2009, pp 125-130.
 B. Han, Y. Wang, S. Dong, L. Zhang, S. Ding, X. Yu, J. Ou, "Smart concretes and structures: A review", J. Intell. Mater. Syst. Struct. vol. 26, no. 11, pp. 1303-1345, 2005
 J. Makar, J. Beaudoin, "Carbon nanotubes and their application in the construction industry", In: Proceedings of the 1st international symposium on nanotechnology in construction (NICOM 2003), P. Bartos, et al., Eds., 2003, pp. 331–341.
 M.S. Konsta-Gdoutos, C.A. Aza, "Self sensing carbon nanotube (CNT) and nanofiber (CNF) cementitious composites for real time damage assessment in smart structures", Cem. Conc. Comp. vol. 53, pp. 110-128, 2014.
 H. Li, H. Xiao, J. Ou, "Effect of compressive strain on electrical resistivity of carbon black-filled cement-based composites", Cem. Concr. Comp., vol. 28, pp. 824-828, 2006.
 G.Y. Li, P.M. Wang, X. Zhao, "Pressure-sensitive properties and microstructure of carbon nanotube reinforced cement composites", Cem. Concr. Comp. vol. 29, pp. 377-382, 2007.
 X. Yu, E. Kwon, "A carbon nanotube/cement composite with piezoresistive properties", Smart Mater. Struct., vol. 18, 5pp, 2009.
 J. Luo, Z. Duan, T. Zhao, Q. Li, "Hybrid effect of carbon fiber on piezoresistivity of carbon nanotube cement-based composite", Adv. Mat. Res., vol. 143-144, pp. 639-643, 2011.
 S. Laflamme, F. Ubertini, H. Saleem, A. D'Alessandro, A. Downey, H. Ceylan, A.L. Materazz, "Dynamic Characterization of a Soft Elastomeric Capacitor for Structural Health Monitoring", J. Struct. Eng., vol. 141, no. 8, 04014186, 2015.
 F. Azhari, N. Banthia, "Cement-based sensors with carbon fibers and carbon nanotubes for piezoresistive sensing", Cem. Concr. Comp., vol. 34, pp. 866-73, 2012.
 Z. Xu, Z. Liu, "Fatigue Damage in Smart Carbon Fiber Concrete by Electrical Resistance Measurement", Key Engineering Materials, vol. 348-349, pp. 435-438, 2007.
 O. Galao, F.J. Baeza, E. Zornoza and P. Garcés, “Strain and damage sensing properties on multifunctional cement composites with CNF admixture” Cem. Conc. Comp., vol. 53, pp. 162-169, 2014.
 S. Wen, D.D.L. Chung, "Partial Replacement of Carbon Fiber by Carbon Black in Multifunctional Cement-Matrix Composites", Carbon vol. 45, no. 3, pp. 505-513, 2007.
 X. Fu, W. Lu, D.D.L. Chung, "Improving the strain-sensing ability of carbon fiber-reinforced cement by ozone treatment of the fibers", Cem. Concr. Res., vol. 28, no. 6, pp. 183-187, 1997
 B. Han, X. Yu, J. Ou, "Multifunctional and smart nanotube reinforced cement-based materials", In Nanotechnology in Civil Infrastructure. A Paradigm shift. Gipalakrishnan K., Birgisson B., Taylor P., Attoh-Okine N. Ed. – Springer 2011, pp. 1-48.
 A. D'Alessandro, F. Ubertini, A.L. Materazzi, M. Porfiri, S. Laflamme. "Electromechanical Modelling of New Nanocomposite Carbon Cement-based Sensors for Structural Health Monitoring", Struct. Health Monit., vol.14, no. 2, pp. 137-147, 2014.
 A.L. Materazzi, F. Ubertini and A. D’Alessandro, "Carbon nanotube cement-based transducers for dynamic sensing of strain", Cem. Concr. Comp., vol. 37, pp. 2-11, 2013.
 A. D'Alessandro, F. Ubertini, A.L. Materazzi, M. Porfiri, "Electrical Modelling of Carbon Nanotube Cement-based Sensors for Structural Dynamic Monitoring" - AIP Conf. Proc. Nanoforum 2014, vol. 1603, pp. 23-30, 2014.
 A. D'Alessandro, M. Rallini, F. Ubertini, A.L. Materazzi, J.M. Kenny, "Investigations on scalable fabrication procedures for self-sensing carbon nanotube cement-matrix composites for SHM applications", Cement Concrete Comp. vol. 65, pp. 200–213, 2016.
 F. Ubertini, "Active feedback control for cable vibrations", Smart Structures and Systems, vol. 4, n. 4, pp. 407-428, 2008.
 B. Han; H. Guan; J. Ou, "Electrode design, measuring method and data acquisition system of carbon fiber cement paste piezoresistive sensors" Sensors and Actuators A vol. 135, pp. 360-369, 2007
 B. Han, K. Zhang, X. Yu, E. Kwon, J. Ou, "Electrical characteristics and pressure-sensitive response measurements of careboxyl MWCNY/cement composites" Cem. Conc. Comp. vol. 34, pp. 794-800, 2012
 B. Han, S. Ding, X. Yu, "Intrinsic self-sensing concrete and structures: A review" Measurements vol. 59, pp. 110-128, 2015.