Self-heating and electrical performance of carbon nanotube-enhanced cement composites
Introduction
Various technologies for designing and constructing large-scale concrete structures have been developed in recent years. Concrete materials are regularly used in various structures worldwide because of their excellent strength and durability. However, the use of concrete also leads to various problems related to the construction environment and global warming. Moreover, concrete structures can experience significant damage in the winter because of black ice caused by snow. Thus, multifunctional concrete with improved strength and durability that can melt snow and ice must be developed to address the aforementioned problems related to existing concrete structures.
Multifunctional concrete can potentially be synthesized by incorporating nanomaterials in existing construction materials [1], [2], [3]. Nanomaterials, which have particle sizes ranging from 0.1 to 100 nm, are attracting significant attention in various areas because of their high specific surface area per unit weight and excellent properties [4], [5], [6], [7]. Nanomaterials can be mixed with construction materials based on ordinary cement to improve the mechanical, electrical, and thermal performances of the materials. Carbon nanotubes (CNTs), whose thermal conductivity and electrical conductivity are 7.5 and 100 times higher, respectively, than those of copper, have been mixed successfully with cement-based materials [8], [9], [10], [11], [12]. Furthermore, there have been numerous studies on the mechanical and physical characteristics of cement composites formed using carbon nanomaterials to improve their strength, electrical conductivity, and heating performance [13], [14], [15], [16], [17], [18].
Li and Zhao [13] fabricated specimens of ordinary mortar and its composites with multi-walled CNTs (MWCNTs) and carbon nanofibers (CNFs) and studied their compressive strengths. The results showed that the compressive strength of the composite with MWCNTs at 28 days was 19% higher than that of the composite consisting of ordinary mortar and CNFs. Furthermore, the load transfer efficiency increased as more MWCNTs were added to the ordinary mortar, because this resulted in a greater number of chemical bonds between the cement hydrates (C-S-H and calcium hydroxide). Chaipanich et al. [14] analyzed the compressive strength of cement mortar in which CNTs and fly ash had been mixed. The CNTs were added in concentrations of 0.5 and 1.0 wt% (cement weight). The results indicated that, for the same fly ash content, the compressive strength of the mortar increased with an increase in the CNT concentration, because both the internal density and the extent of the CNT networks within the composite increased. Morsy et al. [15] fabricated mortar composites containing clay with nano-sized particles and MWCNTs and studied their compressive strengths. The clay content was fixed at 6% of the cement weight, while MWCNT concentration was varied, and composites with dimensions of 50 mm × 50 mm × 50 mm were fabricated. The composite with 0.02 wt% (by cement weight) MWCNTs exhibited a compressive strength 11% higher than that of ordinary mortar. On the other hand, the composite with 0.1 wt% MWCNTs showed a lower compressive strength. Hamzaoui et al. [16] studied the mechanical properties of mortar and concrete containing CNTs, measuring the compressive strength of the composites containing CNTs in different concentrations. The compressive strength was the highest when CNTs were added in amounts of 0.01 and 0.003% by cement weight. The compressive strength increased with the addition of the CNTs, because they served as bridges between the pores and cracks. Choi et al. [17] fabricated cement mortar by mixing dispersions of MWCNTs in distilled water and studied its compressive strength. It was found that the use of distilled water to form the MWCNT dispersions had little effect on the dispersibility of the CNTs. Kang et al. [18] studied the effects of the dispersibility of CNTs on the compressive and tensile strengths of cement composites. CNTs were dispersed using surfactants, high-performance plasticizers, and an ultrasonic treatment. The results showed that the use of both ultrasonic treatment and high-performance plasticizers improved the compressive and tensile strengths by 10% as compared to the other dispersion methods.
As for studies on the electrical and heating performance of composites formed using nanomaterials, Nan et al. [19] elucidated the relationship between CNT content and improvements in thermal conductivity for composites containing CNTs. Liu et al. [20] studied the thermal conductivity of nanofluids containing MWCNTs and found that the thermal conductivity of the nanofluids increased linearly with MWCNT concentration. Li et al. [21] used CNTs dispersed in sulfuric acid and nitric acid as well as unmixed CNTs to fabricate composite specimens with dimensions of 40 mm × 160 mm × 40 mm and measured their electrical resistances. Both the composite containing CNTs dispersed in sulfuric acid and nitric acid and those containing the unmixed CNTs exhibited significantly reduced electrical resistances, because CNTs were uniformly dispersed and formed networks within the composites. Zhang and Li [22] studied the road deicing performances of MWCNT-containing cement composites. The results showed that a composite with a thermal conductivity of 2.83 W/mK was formed when the MWCNTs were mixed in a concentration of 3% by cement weight. Thus, it is possible to melt ice formed on roads using MWCNT-cement composites. Kim et al. [23] studied the mechanical and electrical properties of cement composites containing silica fume and CNTs. It was found that the cement composites with low silica fume and CNT contents exhibited improved mechanical and electrical properties, owing to the decomposition of the aggregated CNTs into small clusters. Konst and Aza [24] analyzed the electrical properties and piezoresistive sensitivity of cement composites containing CNTs and CNFs. The cement composites formed using both CNTs and CNFs in concentrations of 0.1% by cement weight exhibited the highest piezoresistive sensitivity. Lee et al. [25] fabricated cement composites using MWCNTs and studied their electrical and thermal properties. The effects of the mixing method and MWCNT concentration were elucidated. The mixing methods used were forming a CNT coating on the fine aggregates and mixing the CNTs using a dispersion. MWCNTs were added in concentrations of 0.125 and 0.25 wt% by cement weight. The results showed that the composite formed using the former method exhibited better heating performance. Lee et al. [26] studied the heating performance of CNT-based cement composites. Different types of CNTs were used in varying concentrations, with the applied voltage also being a parameter. Specifically, single-walled carbon nanotubes (SWCNTs) and MWCNTs were used in combined concentrations of 0.0625 and 0.125% (by cement weight), while the voltages used were 50 and 100 V. The composite containing MWCNTs and SWCNTs with a total concentration of 0.125% exhibited better heating performance than those with 0.0625 wt% CNTs. Thus, the heating performance increased with the total CNT concentration. Moreover, when a voltage of 100 V was supplied to the 0.125 wt% composite, its temperature rose by 70.6 °C.
Finally, considering studies on nanomaterial-coated films, Hone et al. [27] fabricated an SWCNT film by filtration and desorption through a magnetic field and studied its heating performance. The SWCNT film exhibited a thermal conductivity of 200 W/m·K, which was similar to those of graphite and highly crystalline diamond. Haung et al. [28] studied the thermal conductivity of CNT films exhibiting different arrangements. For the same CNT concentration, the thermal conductivity was higher when the CNTs were arranged in the same direction. Kim et al. [29] fabricated CNT films with dimensions of 10 mm × 10 mm by electrostatic spray deposition without using any binders and studied their electrical conductivity. The CNT films showed good electrical conductivities. In addition, the capacitance of the films was linearly proportional to their CNT concentration. Pham et al. [30] analyzed the electrical resistances of films of conductive CNTs and polymers under tensile strains. The results showed that the electrical resistance increased with an increase in the tensile strain, owing to a decrease in the density of the conductive CNT network and an increase in the intertube distance. Park et al. [31] studied the heat diffusion performance of films of CNTs and polymers. The thermal diffusivity of the films was analyzed visually based on thermal images. Jang and Park [32] fabricated 25 mm × 25 mm films of composites with dispersed CNTs. The CNT concentration and film thickness were varied and the electrical conductivities and heating performances of the films were analyzed. The electrical resistance of the composite nanofilms decreased, because the CNT networks became denser with an increase in CNT concentration. Furthermore, the electrical conductivity increased as film thickness was increased. For temperatures of −5 to 5 °C, the films with lower thicknesses exhibited greater temperature sensitivity.
In this study, the heating performance and electrical properties of cement composites containing MWCNTs were analyzed. A widely employed method of incorporating MWCNTs into cement is to disperse MWCNTs in a solution and then mix them with cement [33], [34], [35], [36], [37], [38]. In this study, however, both an MWCNT-containing solution and MWCNT-coated films were added to cement, and their effects on the composite's heating performance and electrical resistance were measured. In particular, the effects of the mixing methods used, MWCNT concentrations, number of curing days, and applied voltages were investigated. As stated above, the mixing methods used included adding a solution containing the dispersed MWCNTs with ordinary mortar, adding MWCNT-coated films to ordinary mortar, and adding both the MWCNT solution and the MWCNT-coated films. The MWCNT concentrations used were 0.125, 0.25, and 0.5 wt% (by cement weight), and the mortar samples were cured for 7 and 28 days. The surface temperatures and thermal distributions of the composite samples were analyzed using thermal images. Finally, the internal microstructures of the MWCNT-cement composites were analyzed using field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analysis.
Section snippets
Experimental
As stated above, the investigated parameters were the MWCNT mixing methods used, MWCNT concentrations, number of curing days, and applied voltages. Table 1 lists the values of these parameters. The specimens were initially divided into groups based on the mixing method used. The specimens in Group#1 were fabricated by mixing a solution of dispersed MWCNTs with cement mortar. Those in Group#2 were fabricated by inserting MWCNT-coated films into cement mortar. Finally, those in Group#3 were
Heating tests and thermal imaging analysis
The effects of the mixing methods, number of curing days, MWCNT concentrations, and applied voltages on the heating performance were investigated. Fig. 4(a) shows the maximum variations in temperature of the composites fabricated using the MWCNT solution and after 7 days of curing. Here, when a voltage of 60 V was applied, the temperature rose by 1.0 °C for the 0.0 wt% composites, by 1.3 °C for the 0.125 wt% composites, by 1.8 °C for the 0.25 wt% composites, and by 19.8 °C for the 0.5 wt%
Conclusions
In this study, MWCNT-cement composites were fabricated using MWCNTs, which were mixed in cement using three different methods. The heating performance and electrical properties of the fabricated composites were characterized. Based on the experimental results, the performances of the MWCNT-cement composites were analyzed, and the following conclusions were drawn:
- 1.
With respect to the methods used for incorporating MWCNTs, the composites formed by inserting MWCNT-coated films in a mortar exhibited
CRediT authorship contribution statement
Heeyoung Lee: Writing - original draft, Writing - review & editing. Wonjun Yu: Data curation. Kenneth J. Loh: Conceptualization, Writing - review & editing. Wonseok Chung: Conceptualization, Writing - original draft, Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2020R1C1C1005448). Professor K. Loh was supported by the U.S. Federal Aviation Administration (FAA) under cooperative agreement no. 13-G-017, which is a collaborative project with Dr. R. Wu of UC Davis and Professor J. Lynch of the University of Michigan. Mr. Sumit Gupta (UC San Diego) is acknowledged for his help in the preparation of the MWCNT-based thin films used in
References (47)
- et al.
Nanotechnology in concrete–a review
Constr. Build. Mater.
(2010) - et al.
Nanotechnology innovations for the construction industry
Prog. Materi. Sci.
(2013) - et al.
Preparation and characterization of manganese oxide/CNT composites as supercapacitive materials
Diam. Relat. Materi.
(2006) - et al.
Property enhancement of a carbon fiber/epoxy composite by using carbon nanotubes
Compos. Part B: Eng.
(2011) - et al.
Nano reinforced cement and concrete composites and new perspective from graphene oxide
Constr. Building Mater.
(2014) - et al.
Multilayered graphene-carbon nanotube-iron oxide three-dimensional heterostructure for flexible electromagnetic interference shielding film
Carbon
(2017) - et al.
Effect of carbon nanotubes on properties of cement mortars
Constr. Build. Mater.
(2014) - et al.
Highly dispersed carbon nanotube reinforced cement based materials
Cement Concr. Res.
(2010) - et al.
Micromechanics modeling of the electrical conductivity of carbon nanotube cement-matrix composites
Compos. Part B: Eng.
(2017) - et al.
Mechanical behavior and microstructure of cement composites incorporating surface-treated multi-walled carbon nanotubes
Carbon
(2005)
Compressive strength and microstructure of carbon nanotubes–fly ash cement composites
Mater. Sci. Eng. A
Hybrid effect of carbon nanotube and nano-clay on physico-mechanical properties of cement mortar
Constr. Build. Mater.
Enhancement of thermal conductivity with carbon nanotube for nanofluids
Int. Commun. Heat Mass Transf.
Pressure-sensitive properties and microstructure of carbon nanotube reinforced cement composites
Cement Concr. Compos.
Enhanced effect of carbon nanotube on mechanical and electrical properties of cement composites by incorporation of silica fume
Compos. Struct.
Self sensing carbon nanotube (CNT) and nanofiber (CNF) cementitious composites for real time damage assessment in smart structures
Cement Concr. Compos.
Thermal response characterization and comparison of carbon nanotube-enhanced cementitious composites
Compos. Struct.
Void detection of cementitious grout composite using single-walled and multi-walled carbon nanotubes
Cement Concr. Compos.
Fabrication and electrochemical properties of carbon nanotube film electrodes
Carbon
Processing and modeling of conductive thermoplastic/carbon nanotube films for strain sensing
Compos. Part B: Eng.
Electrical and thermal properties of PEDOT: PSS films doped with carbon nanotubes
Synth. Metals
Dispersion of carbon nanotubes and its influence on the mechanical properties of the cement matrix
Cement Concr. Compos.
Effect of mixing methods on the electrical properties of cementitious composites incorporating different carbon-based materials
Construc. Build. Mater.
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