Abstract
The exciting features of carbon nanotubes (CNTs), such as high elastic modulus, high thermal and electrical conductivities, robustness, and nanoscopic surface properties make them attractive candidates for the cement industry. They have the potential to significantly enhanceengineering properties. CNTs play an important and critical role as nano-anchors in concrete, which enhance the strength by bridging pores in the composite matrix, thereby ensuring robust mechanical strength. The diameter, dispersion, aspect ratio, and interfacial surface interaction of CNTs affect the physical and mechanical properties of concrete, if due care is not taken. In this paper, the usable amount of CNT is scaled down considerably from 0.5% to 0.025% by weight of the cement and the fluctuation caused by these phenomena is assessed. It is observed that the properties and exact quantities of incorporated CNTs influence the hydration and consistency of the composites. In order to address these issues, the surface functionalization of CNTs and rheological studies of the composites are performed. The hydration products and functional groups are carefully optimized and characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and a Zeta potential analyzer. For Mixes 6 and 7, the compressive and tensile strength of CNTs incorporated in mortar specimens caused77% and 48% increases in split tensile strength, respectively, and 17% and 35% increases in compressive strength, respectively, after 28 days of curing and compared withthe control Mix.
Highlights
The first awareness about carbon nanotubes (CNTs) was brought to the scientific community in 1991 by Iijima [1], and, two years later, a single-wall CNT was discovered [2]
Transmission Electron Microscopy (TEM) images of functionalized CNTs (f-CNTs) and the Zeta potential distributions of f-CNTs and nf-CNTs are shown in Figure 1a,b, respectively
In the case of nf-CNTs, surface potential is reduced by increasing CNT content, which is indicative of the agglomeration of nanotube bundles
Summary
The first awareness about carbon nanotubes (CNTs) was brought to the scientific community in 1991 by Iijima [1], and, two years later, a single-wall CNT was discovered [2]. Many studies in the recent past have demonstrated the compatible dispersion, surface functionalization, andchanges in surface energy of the nanotube with the goal oftapping the tremendous potential of CNTs as a reinforcing material for high performance cementitious composites [11,22,23,24,25]. As reported in previous studies, it is described that surface treatment of CNTs via chemical modifications to create the carboxyl surface increases the mechanical strength, some studies have proved anegative impact on the strength properties [26]. Reports available on the use of PC-based functionalizing agents to create f-CNTs for enhancing the mechanical properties of mortar/concrete are very scanty. It is proven that the use of polycarboxylic-based superplasticizer as a functionalizing agent for CNT/cement composites enhances the mechanical strength through uniform dispersion with negligible agglomeration. The effect of highly dispersed functionalized CNTs on the mechanical properties of cement mortar composites is demonstrated in this study
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