scholarly journals Development of Multi-Scale Carbon Nanofiber and Nanotube-Based Cementitious Composites for Reliable Sensing of Tensile Stresses

Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 74
Author(s):  
Shama Parveen ◽  
Bruno Vilela ◽  
Olinda Lagido ◽  
Sohel Rana ◽  
Raul Fangueiro
Keyword(s):  
Electrical Resistivity ◽  
Cement Paste ◽  
Linear Correlation ◽  
Carbon Nanofiber ◽  
Tensile Load ◽  
Stress Sensitivity ◽  
Cementitious Composites ◽  
Multi Scale ◽  
Multi Walled Carbon Nanotubes ◽  
Stress Sensing

In this work, multi-scale cementitious composites containing short carbon fibers (CFs) and carbon nanofibers (CNFs)/multi-walled carbon nanotubes (MWCNTs) were studied for their tensile stress sensing properties. CF-based composites were prepared by mixing 0.25, 0.5 and 0.75 wt.% CFs (of cement) with water using magnetic stirring and Pluronic F-127 surfactant and adding the mixture to the cement paste. In multi-scale composites, CNFs/MWCNTs (0.1 and 0.15 wt.% of cement) were dispersed in water using Pluronic F-127 and ultrasonication and CFs were then added before mixing with the cement paste. All composites showed a reversible change in the electrical resistivity with tensile loading; the electrical resistivity increased and decreased with the increase and decrease in the tensile load/stress, respectively. Although CF-based composites showed the highest stress sensitivity among all specimens at 0.25% CF content, the fractional change in resistivity (FCR) did not show a linear correlation with the tensile load/stress. On the contrary, multi-scale composites containing CNFs (0.15% CNFs with 0.75% CFs) and MWCNTs (0.1% MWCNTs with 0.5% CFs) showed good stress sensitivity, along with a linear correlation between FCR and tensile load/stress. Stress sensitivities of 6.36 and 11.82%/MPa were obtained for the best CNF and MWCNT-based multi-scale composite sensors, respectively.

scholarly journals Stabilizing effect of methylcellulose on the dispersion of multi-walled carbon nanotubes in cementitious composites

2020 ◽  
Vol 9 (1) ◽  
pp. 93-104
Author(s):  
Mingrui Du ◽  
Yuan Gao ◽  
Guansheng Han ◽  
Luan Li ◽  
Hongwen Jing
Keyword(s):  
Carbon Nanotubes ◽  
Pore Solution ◽  
Cementitious Materials ◽  
High Ionic Strength ◽  
Cementitious Composites ◽  
Uniform Distributions ◽  
Stabilizing Effect ◽  
Multi Walled Carbon Nanotubes ◽  
The Stability ◽  
Walled Carbon Nanotubes

AbstractMulti-walled carbon nanotubes (MWCNTs) have been added in the plain cementitious materials to manufacture composites with the higher mechanical properties and smart behavior. The uniform distributions of MWCNTs is critical to obtain the desired enhancing effect, which, however, is challenged by the high ionic strength of the cement pore solution. Here, the effects of methylcellulose (MC) on stabilizing the dispersion of MWCNTs in the simulated cement pore solution and the viscosity of MWCNT suspensions werestudied. Further observations on the distributions of MWCNTs in the ternary cementitious composites were conducted. The results showed that MC forms a membranous envelope surrounding MWCNTs, which inhibits the adsorption of cations and maintains the steric repulsion between MWCNTs; thus, the stability of MWCNT dispersion in cement-based composites is improved. MC can also work as a viscosity adjuster that retards the Brownian mobility of MWCNTs, reducing their re-agglomerate within a period. MC with an addition ratio of 0.018 wt.% is suggested to achieve the optimum dispersion stabilizing effect. The findings here provide a way for stabilizing the other dispersed nano-additives in the cementitious composites.

Study on Conductive Mechanism of Carbon Fiber Filled Cement-Based Composites

2011 ◽  
Vol 415-417 ◽  
pp. 1435-1438
Author(s):  
Xue Li Nan ◽  
Xiao Min Li
Keyword(s):  
Electrical Resistivity ◽  
Carbon Fiber ◽  
Cement Paste ◽  
Ionic Conduction ◽  
Strong Electrolyte ◽  
Pull Out ◽  
Fiber Bridging ◽  
Interface Contact ◽  
Conductive Mechanism ◽  
Conductive Properties

In order to investigate conductive mechanism of carbon fiber filled cement-based composites, the conductive properties of cement paste, carbon fiber filled cement-based composites containing different contents of carbon fibers or aggregates were studied. Experimental results indicate that the electrical resistance of the plain cement paste obviously increases with hydration time, which results from the ionic conduction in strong electrolyte solution. The electrical resistivity of the carbon fiber filled cement-based composites decreases with the increase of fiber content. Both contacting conduction and ionic conduction are in charge of the electrical conduction in these composites. The electrical resistivity of the carbon fiber filled cement-based composites decreases under compression, which is due to the improvement of interface contact between matrix and fibers and the increase of fiber bridging probability. The fiber pull-out and breaking under tension lead to an increase in electrical resistivity of these composites. Aggregates block fiber dispersion and contact. This causes an increase in electrical resistivity of the composites.

scholarly journals Fabrication of carbon nanotube-reinforced mortar specimens: evaluation of mechanical and pressure-sensitive properties

2018 ◽  
Vol 188 ◽  
pp. 01019 ◽  
Author(s):  
Evangelia K. Karaxi ◽  
Irene A. Kanellopoulou ◽  
Anna Karatza ◽  
Ioannis A. Kartsonakis ◽  
Costas A. Charitidis
Keyword(s):  
Cementitious Composites ◽  
Mixing Process ◽  
Mechanical And Electrical Properties ◽  
Pressure Sensitive ◽  
Polar Media ◽  
Significant Research ◽  
Multi Walled Carbon Nanotubes ◽  
Carbon Based Nanomaterials ◽  
Walled Carbon Nanotubes ◽  
Carbon Based

Carbon-based nanomaterials are promising reinforcing elements for the development of “smart” self-sensing cementitious composites due to their exceptional mechanical and electrical properties. Significant research efforts have been committed on the synthesis of cement-based composite materials reinforced with carbonaceous nanostructures, covering every aspect of the production process (type of nanomaterial, mixing process, electrode type, measurement methods etc.). In this study, the aim is to develop a well-defined repeatable procedure for the fabrication as well as the evaluation of pressure-sensitive properties of intrinsically self-sensing cementitious composites incorporating carbon- based nanomaterials. Highly functionalized multi-walled carbon nanotubes with increased dispersibility in polar media were used in the development of advanced reinforced mortar specimens which increased their mechanical properties and provided repeatable pressure-sensitive properties.

scholarly journals Effect of Carbon Nanofiber Clustering on the Micromechanical Properties of a Cement Paste

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 223
Author(s):  
Lesa Brown ◽  
Catherine S. Stephens ◽  
Paul G. Allison ◽  
Florence Sanchez
Keyword(s):  
Cement Paste ◽  
Mechanical Response ◽  
Carbon Nanofiber ◽  
Homogenization Method ◽  
Indentation Modulus ◽  
Interfacial Zone ◽  
Micromechanical Properties ◽  
Significant Interest ◽  
Low Stiffness ◽  
Portland Cement Paste

The use of carbon nanofibers (CNFs) in cement systems has received significant interest over the last decade due to their nanoscale reinforcing potential. However, despite many reports on the formation of localized CNF clusters, their effect on the cement paste micromechanical properties and relation to the mechanical response at the macroscopic scale are still not fully understood. In this study, grid nanoindentation coupled with scanning electron microscopy and energy dispersive spectroscopy was used to determine the local elastic indentation modulus and hardness of a portland cement paste containing 0.2% CNFs with sub-micro and microscale CNF clusters. The presence of low stiffness and porous assemblage of phases (modulus of 15–25 GPa) was identified in the cement paste with CNFs and was attributed primarily to the interfacial zone surrounding the CNF clusters. The CNFs favored the formation of higher modulus C–S–H phases (>30 GPa) in the bulk paste at the expense of the lower stiffness C–S–H. Nanoindentation results combined with a microscale–macroscale upscaling homogenization method further revealed an elastic modulus of the CNF clusters in the range from 18 to 21 GPa, indicating that the CNF clusters acted as compliant inclusions relative to the cement paste.

A novel multi-scale model for predicting the thermal damage of hybrid fiber-reinforced concrete

2019 ◽  
Vol 29 (1) ◽  
pp. 19-44 ◽  
Author(s):  
Yao Zhang ◽  
J Woody Ju ◽  
Hehua Zhu ◽  
Zhiguo Yan
Keyword(s):  
Reinforced Concrete ◽  
Cement Paste ◽  
Thermal Damage ◽  
Fiber Reinforced Concrete ◽  
Scale Model ◽  
Fiber Reinforced ◽  
Interfacial Damage ◽  
Hybrid Fiber ◽  
Multi Scale ◽  
Damage Degree

A multi-scale micromechanical model is proposed to predict the damage degree of hybrid fiber-reinforced concrete under or after high temperatures. The thermal degradation of hybrid fiber-reinforced concrete is generally composed of the damage of the cement paste caused by thermal decomposition and thermal incompatibility, the deterioration of aggregates and fibers, and the interfacial damage between aggregates and the matrix. In this multi-scale model, four levels of hybrid fiber-reinforced concrete structures are considered when the thermal damage degree is derived; namely, the equivalent calcium silicate hydrate (C–S–H) product level, the cement paste level, the concrete level, and the hybrid fiber-reinforced concrete level. At the cement paste level, thermal decompositions of C–S–H product and calcium hydroxide are taken into account. In addition, a dimensionless parameter of the crack density is introduced to represent the thermal cracking of the matrix. At the concrete level, the interfacial damage of aggregates is simulated by a spring–interface model, in which the interfacial parameters are assumed to be functions of temperature. Moreover, at the cement paste level and the hybrid fiber-reinforced concrete level, a sub-stepping homogenization method is proposed to determine the effective properties. Comparisons between previously published experimental data and predictions and discussions illustrate the feasibility of the proposed multi-scale model in predicting thermal damage of concrete and hybrid fiber-reinforced concrete.

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