(261b) Use of MULTI-Wall Carbon Nanotubes in Cement-Based Materials for the REAL-Time Monitoring of SMART Structures

USE OF MULTI-WALL CARBON NANOTUBES IN CEMENT-BASED MATERIALS FOR THE REAL-TIME MONITORING OF SMART STRUCTURES

Stephanos F. Nitodas^1,*,Stavros K. Kourkoulis², Zoi Metaxa², Nikolaos D. Alexopoulos³, Spyridoula Boutsioukou³ and Paraskevi Mimigianni¹

¹ Glonatech S.A. TE.S.P.A “Lefkippos” Ag. Paraskevi, 15310, Attica, Greece & 14 West 23^rd St. New York, NY 10010, USA

² National Technical University of Athens, Section of Mechanics, Laboratory of Testing and Materials, 5 Heroes of Polytechnion Ave., 15773 Athens, Greece

³ Department of Financial Engineering, University of the Aegean, 41 Kountouriotou str. Chios, Greece

*e-mail: snitodas@glonatech.com

ABSTRACT

During the last decade, researchers focus their efforts in producing multi-functional materials. The driving design parameters are their improved mechanical properties as well as their ability to monitor their structural health. The latter seems to be the case for the cement-based materials studied in the present work; the production of carbon nanotubes enhanced the production of ‘modified’ materials that would serve multi-functional purposes. Exploiting their electrical conductivity they could be used to non-conductive materials in order to enhance their monitoring capabilities. The addition of several percentages of multi-wall carbon nanotubes (MWCNTs) to the cementitious matrix enabled the structural health monitoring of the material and to establish correlations between internal damage and change in electrical resistance. Therefore, the real-time monitoring of the multifunctional characteristics of the material enables the prediction of the level of damage and/or the potential failure of the smart structure.

In the present study, the material’s mechanical and electrical properties are explored via the utilization of Glonatech’s multi-wall carbon nanotubes (MWCNTs, Favvas et al.) of extremely low bulk density as reinforcement in cementitious materials, which are commonly employed for the restoration of monuments of cultural heritage. The target is the quantification of the influence of different types of surfactants, various concentrations of MWCNTs and processing procedures (e.g. ultrasonication parameters) on the flexural and compressive strength of both, cement paste and mortar matrices.

It is well known from the literature that the addition of carbon nanotubes in cementitious materials leads to improvement of the mechanical performance of the matrix (Konsta-Gdoutos et al. 2010, Metaxa et al. 2012). This increase depends on the effectiveness of the nanotubes dispersion. Our experiments (Alexopoulos et al. 2015) showed that the optimum dispersion of the carbon nanotubes at percentages as low as 0.1-0.2% is directly related to the observed enhancement of the modulus of elasticity as well as to the increased strength properties of the cementitious matrix.

The addition of these nano-inclusions at concentrations above the percolation threshold, besides the improvement of the mechanical performance, also resulted in the enhancement of the material’s monitoring ability via the electrical resistance change method (Boutsioukou and Metaxa 2015). This is a key concept for their widespread use, as currently the traditional approaches for structural health monitoring of Historical Monument components is largely based on strain gauges and other techniques that do not permit quantitative description of strain changes or induced damage inside the material / structure.

Keywords: carbon nanotubes, cementitious materials, mechanical properties, smart materials, mortar

REFERENCES

• Favvas E, Stefanopoulos K, Stefopoulos A, Nitodas S, Mitropoulos A and Lairez D, Dispersion study of functionalized MWCNTs in solution by SANS, 7th International Workshop 'Characterization of Porous Materials: from Angstroms to Millimeters' (CPM-7), May 2015, Delray Beach FL, USA.
• Alexopoulos ND, Boutsioukou S, Giannakopoulou F, Metaxa ZS, Kourkoulis SK, Reinforcement at the nanoscale of cementitious materials made from white cement with multiwall carbon nanotubes, 6^th International Conference on Mechanics and Materials in Design, 26-30 July 2015, Ponta Delgada/Azores, Portugal.
• Boutsioukou S and Metaxa ZS, Structural health monitoring of cement-based materials reinforced with carbon nanotubes, 8^th National Conference on NDT of the Hellenic Society of NDT (HSNT), 8-9 May 2015, National Hellenic Research Foundation, Athens, Greece
• Konsta-Gdoutos MS, Metaxa ZS, Shah SP (2010). Multi-scale mechanical and fracture characteristics and early-age strain capacity of high performance carbon nanotube/cement nanocomposites, Cement and Concrete Composites, 32 (2), pp.110-115.
• Metaxa ZS, Seo JWT, Konsta-Gdoutos MS, Hersam MC, Shah SP (2012). Highly concentrated carbon nanotube admixture for nano-fiber reinforced cementitious materials. Cement and Concrete Composites, 34, pp. 612-617.