Fracture toughness and failure mechanism of high performance concrete incorporating carbon nanotubes (original) (raw)
Related papers
Mechanical Characterization of Concrete Reinforced with Different Types of Carbon Nanotubes
Arabian Journal for Science and Engineering, 2019
The main purpose of this study is to characterize the mechanical properties of concrete reinforced with carbon nanotubes (CNT). For this, an extensive experimental program was carried out involving the production and characterization of concrete mixes with five types of CNT, in terms of flexural, splitting tensile and compressive strength, ultrasonic pulse velocity, elastic modulus and fracture toughness. The dispersion ability of CNT in a wide range of pH aqueous suspensions was evaluated prior to their incorporation in concrete. It was found that 0.05-0.1% of CNT were effective to improve all tested properties, increasing the compressive, flexural and splitting tensile strength, as well as the fracture energy and elastic modulus up to 23%, 18%, 27%, 42% and 15%, respectively. The CNT showed great potential to improve the crack resistance and the fracture toughness of concrete, especially in the pre-peak performance of concrete. In relative to other types of CNT, concrete containing higher dosages of lower aspect ratio CNT had the highest improvement of mechanical strength. This is explained by the lower structural damage and higher dispersion capacity of this type of CNT in high pH environments. Nevertheless, higher aspect ratio CNT showed better contribution for the fracture energy, due to their more efficient bridging effect.
Carbon Nanotube Effect on the Ductility, Flexural Strength, and Permeability of Concrete
Journal of Nanomaterials
Recently, remarkable types of carbon nanofilaments called carbon nanotubes (CNTs) have raised the interest of many concrete and cementitious composite researchers due to their significant mechanical, electrical, thermal, kinetic, and chemical properties. These nanofilaments are considered promising applicants to use in producing high-performance cement-based composite materials. In this research, the effect of CNT use on the flexural strength, strain capacity, permeability, and microstructure of concrete was investigated. Concrete batches of 0, 0.03, 0.08, 0.15, and 0.25 wt.% CNTs were prepared using a mixing method that consisted of a 30-minute solution sonication and a 60-minute batch mixing. On the 28th day, the mechanical properties were determined. The results indicated that concrete prepared using high CNT contents of 0.15 and 0.25 wt.% increased the flexural strength by more than 100% in comparison with 0% CNT concrete. Furthermore, the results showed that CNTs would increase...
Proceedings of the 4th Brazilian Conference on Composite Materials
Due to the necessity to improve the mechanical properties of cement-based materials, carbon nanotubes (CNTs) have been studied to prepare cement composites. Once they present high tensile strength, if well dispersed and well adhered to the cement hydration products, they can improve the mechanical properties of a cement paste system. Because of that, an effective dispersion process is crucial. Studies involving CNTs dispersion in cement particles in presence of a non-aqueous media of isopropanol resulted in improvements in mechanical properties suggesting a good dispersion and strong bond between CNTs and cement particles. Considering that, the present paper analysed a cement paste reinforced with 0%, 0.05% and 0.10% of CNTs dispersed in a non-aqueous media of isopropanol through three-point bending tests in notched specimens and direct tensile tests. The influence of CNTs on the material fracture energy, flexural strength, and tensile strength was addressed. The results pointed out an improvement of 90% of fracture energy in composites with 0.05% of CNTs. The results of direct tensile tests indicate an improvement of about 20% tensile strength in cement paste with 0.05% of CNTs and images by scanning electron microscopy indicate a better dispersion by this proportion. These results suggest not only an effective dispersion of CNTs in cement matrix by the used dispersion methodology at a dosage of 0.05% of CNTs, but also that the cement composites properties may be improved by the presence of them.
A STUDY ON THE IMPACT OF CARBON NANOTUBES ON THE PROPERTIES OF CONCRETE
IAEME PUBLICATION, 2021
Ordinary concrete is widely used in construction engineering due to its high compressive strength, low cost and abundance in raw material. However, the main problem of plain concrete is weak in resistance to tensile loads; constituting a major restriction to its usage. Carbon Nanotubes (CNTs) tend to be most aspirational Nano material having favorable mechanical properties and developed aspect ratio, for reinforcing cementitious elements which are weak in tension. Nevertheless, CNTs may agglomerate within the cement matrix due to high Van der waals forces, resulting in low enhancement or even deterioration of concrete. Therefore, the objective of this literature survey is to summarize the past experimental data on the properties of concrete with carbon nanotubes. The prime objective is to identify the optimum content of CNT in concrete for improving the Compressive and Flexural strength of concrete. The Optimum Content of CNT in the concrete is the most important parameter that highly influences its mechanical properties, workability, durability and various other properties.
Variation of Concrete Strength with the Insertion of Carbon Nanotubes
AMR, 2013
Nanomaterials could change the face of modern construction because they are more resistant, more durable and have notable features. Concrete is a material widely used in construction industry worldwide. Carbon nanotube has been considered a new and outstanding material in nanoscience field with great potential application in the construction industry. The study presented in this paper, aims at assessing how carbon nanotubes can affect cement composites and so the concrete, in terms of microstructure and physical-mechanical properties. Three different ratios of carbon nanotubes have been searched: 0.20%, 0.40% and 0.60%. To evaluate the mechanical properties of the samples, destructive and non-destructive tests were carried out to obtain compressive strength, tensile strength by diametrical compression, dynamic modulus of elasticity as well as the determination of their deformation properties. This work also aims to motivate entrepreneurs and professionals in the sector of civil engineering on the advantages of the application of nanotechnology in construction, as well as providing information to the scientific and technological community in general.
2018
Cement has been largely used in the construction industry, specifically as a matrix for concrete. Recently, a new generation of cement-based composite that greatly increases mechanical properties is replacing conventional concrete. With periodic advances in the field, researchers considered particles with highaspect ratios such as Carbon Nanotubes (CNTs) to reinforce cement matrices. Although there is not much literature to draw upon in research, some research on improving tensile strength of cementitious composite incorporating with CNTs does exist. However, there had been no evidence of investigation into impact strength until this study. Most papers presented examined the effect of multi-walled carbon nanotubes, but very few investigated single-walled carbon nanotubes (SWCNTs), and none of the research compared SWCNTs with multiwalled carbon nanotubes (MWCNTs), and hybrid CNTs (50% of MWCNTs and 50% SWCNTs) in cementitious composites. The aim of this research is to assess and compare the effect on tensile and impact strength of cementitious composite of reinforcing cement with functionalized (-COOH) SWCNTs, MWCNTs, and hybrid CNTs. Additionally, the lack of standard mixing and test procedures for nanomaterials with cement is considered.
Studying the Incorporation of Multi-Walled Carbon Nanotubes in High-Performance Concrete
Sustainability
The current work aimed to study nanomodified HPC with multi-walled carbon nanotubes (MWCNT). The effect of MWCNT concentration, from 0% to 0.6% of cement weight, was evaluated on HPC multi-level output properties, namely, the flowability, mechanical strength, electrical resistivity, and microstructure. In addition, a tentative, simplified, and more cost-effective method based on dispersion of a high-pH solution of hydroxide was also adapted to disperse the MWCNT before incorporation in fresh HPC mixtures. Adding 0.2–0.6% MWCNT reduced HPC workability even with a higher superplasticiser dosage. The electrical resistivity was 484.58 Ω m for the HPC without MWCNT at 28 days of curing, while the samples with 0.2%, 0.4%, and 0.6% MWCNT presented 341.41 Ω m, 363.44 Ω m, and 360.34 Ω m, respectively. The use of 0.2–0.6% MWCNT in HPC decreased the flexural and compressive strength by 20% and 30%, respectively. The HPC performance decrease with MWCNT seemed to be related to relatively signif...
Effect of Single-Walled Carbon Nanotubes on Strength Properties of Cement Composites
Materials, 2020
This study aimed to investigate the effects of single-walled carbon nanotubes (SWCNTs) on strength the properties of cement composites when surfactant (SAA) was applied as the dispersion method. TritonX-100 (TX10) was used as the SAA to pretreat SWCNTs, which has been proved to perform well in dispersing the agglomerates of SWCNTs. In this study, four different concentration of SWCNTs, namely 0.00 wt%, 0.02 wt%, 0.04 wt%, and 0.06 wt% by the mass of cement, were used to prepare cement composite specimens. The compressive strength and flexural strength of specimens were tested and recorded. The results show that the compressive and flexural strengths of cement composites decreased with the increase in the concentration of SWCNTs without the addition of TX10. However, when SWCNT suspensions were pretreated with TX10, the strength variation pattern changed; the compressive and flexural strengths of cement composites increased as a function of the concentration of SWCNTs, although there...
Parametric Study of Durability Properties of Concrete Prepared Using Multi-Walled Carbon Nanotubes
2018
Nanotechnology and Nano materials have much more advantages compare to conventional materials and are also helpful to overcome certain limitations of conventional materials. Among some of the nano materials Carbon Nanotubes are found to be useful in Construction industries along with construction materials thereby increasing and improving concrete properties. This experiment is based on usage of Multi-walled carbon nanotubes (MWCNT) in (0.025%) proportions by weight of cement in preparation of M25 grade Concrete. For effectively using MWCNT in concrete Polycarboxyl ether Super plasticizer was used in (0.4) % proportion as a surfactant in water with MWCNT to disperse them. Sorptivity Test was conducted at 90 days. Cubes of (150 x 150 x 150) mm were used for testing. Cost comparison for 1m 3 of concrete was calculated for normal design mix concrete and for MWCNT containing concrete. Applications of MWCNT were discuss. Keyword: Nanomaterials, Multi-walled Carbon Nanotubes, Polycarboxyl...
Dispersion of carbon nanotubes and its influence on the mechanical properties of the cement matrix
Cement and Concrete Composites, 2012
An appropriate dispersion of carbon nanotubes (CNTs) is a prerequisite for their use in improving the mechanical properties of cement-based composites. In this study two types of carbon nanotubes (CNTs) having different morphologies were investigated. To obtain a uniform distribution of CNTs in the cement matrix, the effect of sonication on the deagglomeration of CNTs in combination with anionic and nonionic surfactants in varying concentrations was quantitatively investigated when preparing aqueous dispersions of CNTs for the subsequent use in cement paste. The relationships between the quality of CNT-dispersion on the one hand and the sonication time and surfactant concentration on the other were determined using UV-vis spectroscopy. After dispersion, nitrogen-doped CNTs were found mostly as individual, broken CNTs. In contrast, after the treatment of the mixture of single-, double-, and multiwalled CNTs, a net-like distribution was observed where destruction of the CNTs due to sonication could not be distinguished. Modification of the cement pastes with dispersions of CNTs led to a pronounced increase, up to 40%, in compressive strength and, in some cases, to a moderate increase in tensile strength under high strain-rate loading. However, no significant improvement in strength was observed for quasistatic loading. Microscopic examination revealed that the bridging of the C-S-H phases differed depending on the type of CNT. This explained, at least partly, the observed effects of CNT-addition on the mechanical properties of hardened cement pastes.