Progress in Nanotechnology and Nanomaterials Oct. 2013, Vol. 2 Iss. 4, PP. 117-129 - 117 - Can Carbon Nanotubes Make Wonders in Civil/Structural Engineering? Saptarshi Sasmal *1 , B. Bhuvaneshwari 2 , Nagesh R. Iyer 3 1, 2, 3 CSIR-Structural Engineering Research Centre, CSIR Complex, Taramani, Chennai- 600113, India *1 saptarshi@serc.res.in; 2 bhuvana@serc.res.in; 3 nriyer@serc.res.in Abstract- Nanoscience and nanotechnology provide enormous opportunities to engineers the properties of materials by working in atomic or molecular level. It has not only facilitated to overcome many limitations of conventional materials, but also tremendously improved the mechanical, physical and chemical properties of the materials as well. To develop high performance, multifunctional, ideal (high strength, ductile, crack free, durable) construction material, carbon nanotubes (CNTs) show promising role to modify/enhance the characteristics of the conventional construction materials such as concrete and steel. In the paper, a brief on geometry and mechanical properties, synthesis processes, possibilities and findings of different researchers on CNT reinforced composites is presented. It is also brought out that a crack free durable concrete is possible if certain issues such as uniform distribution of CNT in composite and bond behavior of CNT modified concrete can be addressed. Finally, few pre-proof of concepts are mentioned where CNTs can play the pivotal role to redefine the scope and ability of civil engineering, in general, and structural engineering, in particular. Keywords- Carbon Nanotubes; Concrete Composite; Durability; High Strength; Synthesis; Challenges I. INTRODUCTION Nanoscience has paved the way to tailor the properties of materials based on particular requirement by working in atomic or molecular level. In general, nanotechnology is not an isolated technology for certain purposes, but it is an enabling technology to achieve many goals by engineering a material at nano level. Similar to the fields like energy, medicine, electronics, etc., nanotechnology shows remarkable potentiality of its role to play by opening a new way to solve many of the perennial problems civil engineers do face every day. Aggressive development of infrastructures using conventional constructional materials will be responsible for approx. one-third of global warming. It is estimated that per ton production of cement approximately produces one ton of CO 2 . Hence, there is an alarming need for developing new construction material which is smart, efficient and sustainable. The countries like India, where growth of infrastructure plays a significant role in the growth of the country, engineering of green and smart construction material will enormously help to generate public, private, strategic and societal goods. Among all the nano forms of metals and non-metals, carbon nanotubes (CNTs) seem to have the most promising role towards developing an ideal (high strength, ductile, crack free, durable) construction material like concrete. The carbon nanotubes (CNTs) attract the researchers since their discovery, because of their higher strength and relatively low weight. These nanotubes are useful for any application where robustness and flexibility are necessary. Further, nanotubes are also stable under extreme chemical environments, high temperatures and moisture as well. Use of nano engineered concrete would lead to considerable reduction in the dimensions of the structural members which could result in much less consumption of cement and thereby reduction of CO 2 release and make the world sustainable through eco-friendly products. Further, carbon nanotubes can also be used to make nano composite steel. Initial research findings reveal that they are about 50 times stronger and 10 times lighter than conventional steel. Apart from technical intricacies and lack of information, one of the main obstacles in using CNTs in construction is cost of CNTs as construction materials need to be produced in mass and should be reasonably cheap. Exorbitant cost implications in production of CNTs are diminishing very fast. For example, cost of industrial CNT was $27,000/lb in 1992, $550/lb in 2006 and $120/lb in 2011. It is also predicted that the price would be as low as $0.5/lb in 2013- 14 [1]. To bring out the best from carbon nanotubes to the construction industry, specifically, in usage of construction materials, the extraordinary geometrical shape, unparallel mechanical properties, complex but challenging synthesis processes, and probable areas of applications are essential to be known. Therefore, an overview of these aspects of carbon nanotubes with the current state of knowledge is brought out in the present paper. II. GENERAL DESCRIPTION AND GEOMETRY Carbon nanotubes can be idealized as rolled form of graphite sheets where carbon atoms are arranged in a hexagonal array. The ends are capped by a dome shaped half fullerene molecules. Normally, the elastic properties of CNTs are assumed to be independent of the chirality due to the regular isotropic nature of hexagonal two-dimensional crystal. But, dislocation theory states that the strength mechanism is a function of the tube chirality [2]. Therefore, the mechanical properties of nanotubes greatly depend on the atomic arrangement of the nano structure. The atomic structure of nanotubes is defined by the tube chirality. Two limiting cases exist, i.e. ziz-zag shaped (chiral angle of 0 0 ) and armchair shaped (chiral angle of 30 0 ). The difference in armchair and zig-zag nanotube structures is shown in Figure 1.