Effect of carbon nanotubes sonication on mechanical properties of cement pastes

Abstract

The excellent mechanical properties of carbon nanotubes (CNTs) make them a highly attractive material for use as reinforcement in cement composites. However, it is established that this nanomaterial presents a severe dispersion problem in cement matrices owing to its high specific surface area. An alternative method for dispersing the CNTs is the use of sonication in the presence of a superplasticizer admixture. However, high energy sonication can severely damage CNTs, which can affect their behavior in cement pastes. Thus, it is necessary to optimize the CNTs sonication parameters to optimize the performance of CNT-cement pastes. After sonication with different energies of CNTs water suspensions, the CNTs dispersion was evaluated through UV-Vis spectroscopy and the eventual CNTs damage observed by TEM. Workability, compressive and flexural strengths of the CNTs-cement pastes were also measured. The results revealed that the sonication parameters can be optimized to enhance the effect of CNTs on cement paste behavior.

Influence of Ultrasonication of Functionalized Carbon Nanotubes on the Rheology, Hydration, and Compressive Strength of Portland Cement Pastes

“…Some authors have reported that CNT significantly increased the mechanical performance of cementitious composites. By contrast, other Siqueira and Gleize [12] analyzed the influence of amplitude (20%, 50% and 80%) and ultrasonication time (6, 30 and 60 min) on the dispersion of aqueous non-functionalized CNT dispersions and on mechanical properties of cementitious composites. The authors observed that the use of high energy combined with the short ultrasonication time (amplitude of 80% and duration of 6 min) generated the best mechanical performance when compared with the reference (i.e., plain cement paste).…”

“…It is also worth mentioning the lack of information regarding the parameters used in the CNT dispersion process via ultrasonication. This makes direct comparison of results complex and limits the reproduction of previously published studies [6,12]. Additionally, with the exception of the work from Isfahani et al [11], other previously mentioned works [10,12,13] evaluating the influence of ultrasonication energy on the mechanical properties of cementitious composites did not compare the effect of different ultrasonication times and amplitudes with composites with CNT that were not dispersed by ultrasonication.…”

“…Additionally, with the exception of the work from Isfahani et al [11], other previously mentioned works [10,12,13] evaluating the influence of ultrasonication energy on the mechanical properties of cementitious composites did not compare the effect of different ultrasonication times and amplitudes with composites with CNT that were not dispersed by ultrasonication. Furthermore, although some works [10][11][12][13] have evaluated the influence of CNT ultrasonication energy on the mechanical properties of cementitious composites, the effect of this dispersion process on aqueous CNT + SP solutions has not been thoroughly investigated. In that context, Assi et al [14] mentioned that the ultrasonication of water molecules produce hydrogen peroxide (H 2 O 2 ), which reacts with the calcium hydroxide [Ca(OH) 2 ].…”

“…Considering this gap in knowledge, the aim of this work is to elucidate the influence of the ultrasonication process on rheology, hydration kinetics, compressive strength, and microstructure of cementitious composites with functionalized CNT without ultrasonication and pastes with CNT that were previously ultrasonicated with two amplitudes (50% and 80%) [12]. For this purpose, CNT dispersions were characterized by UV-Vis spectroscopy, dynamic light scattering (DLS), and Fourier transform infrared spectroscopy (FTIR).…”

Improvement of thermal stability and gamma‐ray absorption in microwave absorbable poly(methyl methacrylate)/graphene nanoplatelets nanocomposite

“…The increase of the aggregation of carbon nanotubes in the dispersion affects the thermal properties due to smaller size particles 22 . The nanomaterial presents a considerable dispersion problem in matrix owing to its high specific surface area 23 . Besides, the sharp edges of GNP can cause the density changes to initiate lower physical properties 18 .…”