Dispersion of High Concentrations of Carbon Nanofibers in Portland Cement Mortars

Abstract

This research focuses on creating and maintaining a stable dispersion of carbon nanofibers (CNFs) in portland cement based materials. A microfine cement is used in conjunction with an untraditional dispersion method to encourage and stabilize the dispersion of CNFs in concentrations up to 5% by mass of cement. A computational simulation was utilized to examine an effect called geometric clustering on the dispersion of CNFs among Type I/II and microfine cement grains. The geometric clustering simulation revealed a higher achievable dispersion for microfine cement than for Type I/II cement. Scanning electron microscopy (SEM) was used to quantify the dispersion of CNFs among Type I/II and microfine cement grains. SEM image analysis indicated excessive CNF clumping among Type I/II cement grains, while the dispersion of hybrid microfine cement mortar continued to improve as the concentration of CNFs increased up to 5% by mass of cement. Mortar cube elastic stiffness and mortar prism flexure tests revealed that high concentrations of CNFs had detrimental effects in hybrid Type I/II cement mortar, whereas similar concentrations of CNFs had negligible or beneficial effects in hybrid microfine cement mortar.

Early-Age Performance of 3D Printed Carbon Nanofiber and Carbon Microfiber Cement Composites

“…It was thought that the low slump of the tested cement inks mitigated the presence of bleed-water for both the cast and the printed cement composites, limiting the movement of the CNFs through the hydrating cement paste and thus their reagglomeration. CNF clustering has been shown in the literature to be influenced by bleed-water with an increasing gradient in cluster size in the direction of bleed-water migration ( 49 , 50 ) and to be reduced by hindering the movement of the CNFs in the fresh cement paste ( 40 , 51 ). Studies and methods of quantification of CNFs in cement pastes can be found elsewhere ( 40 , 50 ).…”

“…Most of the focus to date has been on steel, glass, and polymeric microfibers. However, 3D printing of cement-based materials with carbon nano and microfibers has received little attention, despite the demonstrated benefits of carbon fibers in traditional cast concrete, including strength improvements and smart property capabilities (34)(35)(36)(37)(38)(39)(40). In addition, while the mechanical behavior of short fiber reinforced 3D printed cement-based materials has been shown to be influenced by the printing process and fiber alignment along the print direction (1,26,27,33), there is limited information on the effect of the fibers during the extrusion process and the resulting microstructure of the printed material.…”

Antifungal Susceptibility Assessment of Innovative and Non-Conventional Lime Mortars Incorporating Almond-Shell Powder Bio-Waste Subjected to Particle-Dispersion Technique

“…In this framework, the nanotechnology sector is improving the green reputation of the building industry by reevaluating the raw materials required for construction and proposing the application of alternative techniques. The outstanding properties of carbon nanotubes, for instance, have already been explored for strength-enhancement and crack-prevention purposes in cement and concrete [ 3 ] and also for mechanical and thermal properties improvement in the case of ceramics [ 2 ]. In this context, nanotitanium dioxide (n-TiO 2 ) is a particularly attractive material given its rich physical–chemical properties, biocompatibility, and wide variety of morphologies.…”