Cementitious composites incorporating Multi-Walled Carbon Nanotubes (MWCNTs): effects of annealing and other dispersion methods on the electrical and mechanical properties

Abstract

This study focuses on different techniques for dispersing Multi-Walled Carbon Nanotubes (MWCNTs) in cementitious materials. The impact of dispersion is observed through electrical resistivity and mechanical properties of cementitious composites. Two contents (0.5 and 1% by mass of cement) of MWCNTs are investigated and three different techniques were used to disperse CNTs in water by sonication: (i) pristine, P-CNT, (ii) functionalized carbon nanotubes by classical approach (dispersive agent, D-CNT), and (iii) by an innovative approach (annealing, A-CNT). Self-sensing response of the material under cyclic compressive loading is measured with Wheatstone Bridge (WSB) circuit. Results showed a detrimental effect of dispersive agent on the resistivity and mechanical properties of cementitious composites irrespective of the content of CNTs. However, the impact of P-CNT and A-CNT on the reduction of mechanical properties is slight. With the use of 1% content of A-CNTs, a stable resistivity response of the material is observed irrespective of the saturation degree. This indicates that content higher than 1% of A-CNTs is not required for the development of smart cementitious composites for structural health monitoring (SHM). The test results of self sensing measurements indicate a poor repeatability of the electrical response for plain mortar under each loading cycle while, stable response is noticed with specimens incorporating 1% of A-CNTs. The maximum variation in fractional change in voltage (FCV) shown by plain mortar is 6.3% indicating high electrical resistance of plain mortar, while in case of mortar containing 1% A-CNTs, variation in FCV is 35% indicating lower electrical resistance and better sensitivity of the material.

Debonding of Thin Bonded Rubberised Fibre-Reinforced Cement-Based Repairs under Monotonic Loading: Experimental and Numerical Investigation

“…The chemical composition and physical properties of the Portland cement are shown in Table 1 . Similar findings have also been reported in other research study [ 20 ]. Master Glenium 27, a modified polycarboxylic ether polymer-based superplasticizer, and Rheomac were used as superplasticizer and viscosity-modifying agent (VMA), respectively.…”

Effects of Molarity and Storage Time of MWCNTs on the Properties of Cement Paste

“…In the literature, there are several works that report the enhancement of the mechanical properties of Portland cement by adding MWCNTs; for instance, Yousefi et al [57] present results showing that the addition of a surfactant employing the mild ultrasonication technique facilitates the homogeneous dispersion of MWCNTs in the cement matrix and enhances the mechanical properties of the hardened concrete. A more recent work by Shahzad et al [58] reported a study focused on different techniques for dispersing MWCNTs in cementitious materials and the impact on the mechanical properties. As MWCNTs are better dispersed, they tend to fill the micropores, thus increasing the density of the matrix and improving the mechanical properties.…”

Self-sensing GFRP-reinforced concrete beams containing carbon nanotube-nano carbon black composite fillers

“…However, conventional concrete, as a structural material, does not have the ability to achieve in-situ monitoring [6]. Strikingly, the advent and fast development of intrinsic self-sensing concrete composed of nonconductive concrete matrix and electrically conductive fillers such as carbon fibers (CFs), carbon nanotubes (CNTs), carbon nanofibers, steel fibers, carbon black (CB) and graphene, with the ability to monitor stress, strain, micro-crack, and damage, opens a vast range of possibilities for structural health monitoring (SHM) of infrastructures [7][8][9][10][11][12][13][14].…”