Hydration phenomena of functionalized carbon nanotubes (CNT)/cement composites

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 caused 77% 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.