Eco-friendly treatment of carbon nanofibers in cementitious materials for better performance

Abstract

Extensive studies have been carried out to use carbon nanofibers/tubes (CNF/Ts) to reinforce cementitious materials because of their extraordinary properties (mechanical, electrical, energy storage). However, the high surface area of CNF/Ts makes them difficult to disperse in cementitious materials homogenously, leading to inefficient use of CNF/Ts. In this study, an eco-friendly method is proposed to functionalize CNFs so that they can be easily dispersed into cementitious materials. This method uses a plant-based biomolecule, tannic acid (TA), to modify CNFs. Compared with existing chemicals used to functionalize CNFs, TA is ubiquitous, renewable, and non-toxic. Experimental studies show that the TA can be successfully coated onto the surface of CNFs, making them stabilized in the water-based solution. SEM analysis suggests that a better dispersion of CNFs was achieved in the hydrated cement paste with TA functionalization compared to the one prepared with pristine CNFs. The homogenous dispersion also makes the nanofibers available to fill the nanopores, leading to a densified microstructure, as proved by MIP analysis. As a result, significant improvement in the mechanical properties of cement mortar has been achieved by using TA functionalization.