scholarly journals An Experimental Study on Static and Dynamic Strain Sensitivity of Smart Concrete Sensors Doped with Carbon Nanotubes for SHM of Large Structures

2018 ◽  
Author(s):  
Andrea Meoni ◽  
Antonella D'Alessandro ◽  
Austin Downey ◽  
Enrique García-Macías ◽  
Marco Rallini ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Reinforced Concrete ◽  
Experimental Testing ◽  
Dynamic Strain ◽  
Cement Matrix ◽  
Strain Sensitivity ◽  
Strain Sensing ◽  
Multi Walled Carbon Nanotubes ◽  
Material Fabrication ◽  
Smart Concrete

The availability of new self-sensing cement-based strain sensors allows the development of dense sensor networks for Structural Health Monitoring (SHM) of reinforced concrete structures. These sensors are fabricated by doping cement-matrix materials with conductive fillers, such as Multi Walled Carbon Nanotubes (MWCNTs), and can be embedded into structural elements made of reinforced concrete prior to casting. The strain sensing principle is based on the multifunctional composites outputting a measurable change in their electrical properties when subjected to a deformation. Previous work by the authors was devoted to material fabrication, modeling and applications in SHM. In this paper, we investigate the behavior of several sensors fabricated with and without aggregates and with different MWCNTs content. The strain sensitivity of the sensors, in terms of fractional change in electrical resistivity for unit strain, as well as their linearity are investigated through experimental testing under both static and dynamically varying compressive loadings. Moreover, the responses of the sensors when subjected to destructive compressive tests are evaluated. Overall, the presented results contribute to improving the scientific knowledge on the behavior of smart concrete sensors and to furthering their understanding for SHM applications.

scholarly journals An Experimental Study on Static and Dynamic Strain Sensitivity of Embeddable Smart Concrete Sensors Doped with Carbon Nanotubes for SHM of Large Structures

Sensors ◽  
2018 ◽  
Vol 18 (3) ◽  
pp. 831 ◽  
Author(s):  
Andrea Meoni ◽  
Antonella D’Alessandro ◽  
Austin Downey ◽  
Enrique García-Macías ◽  
Marco Rallini ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Experimental Study ◽  
Dynamic Strain ◽  
Strain Sensitivity ◽  
Large Structures ◽  
Smart Concrete

Dispersion of Multi-Walled Carbon Nanotubes in Portland Cement Concrete Using Ultra-Sonication and Polycarboxylic Based Superplasticizer

2015 ◽  
Vol 802 ◽  
pp. 112-117 ◽  
Author(s):  
Ali Yousefi ◽  
Norazura Muhamad Bunnori ◽  
Mehrnoush Khavarian ◽  
Taksiah A. Majid
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Portland Cement ◽  
Cement Matrix ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Uniform Dispersion ◽  
Multi Walled Carbon Nanotubes ◽  
Sonication Technique ◽  
Walled Carbon Nanotubes

The potential properties of carbon nanotube-cement based materials strongly depend on the dispersion of carbon nanotubes (CNTs) within the cement matrix and the bonding between CNTs and the hydrated cement. The homogeneous dispersion of CNTs in the cement matrix yet is one of the main challenges due to strong van der Waals forces between nanotubes. In this study, a polycarboxylic ether based superplasticizer and ultra-sonication technique was used for dispersion of multi-walled carbon nanotubes (MWCNTs). Portland cement concrete specimens with different concentrations of MWCNTs (0.04 and 0.1 % by the weight of cement), with and without the presence of superplasticizer were investigated. Compressive strength test results revealed a significant improvement in mechanical properties of sample containing 0.1 % MWCNTs and 0.2 % superplasticizer. Moreover, field emission scanning electron microscopy (FESEM) images of fractured surfaces of hardened specimens showed a good dispersion of MWCNTs within the cement matrix. This method was developed to facilitate the uniform dispersion of MWCNTs in the cementitious concrete for better reinforcement in nanoscale and mechanical properties enhancement by transfer of load between the nanotubes and matrix.

The I-V Characteristics and Percolation Threshold of the Cement-Based Materials Filled with Multi-Walled Carbon Nanotubes

2009 ◽  
Vol 60-61 ◽  
pp. 36-39
Author(s):  
Jian Lin Luo ◽  
Zhong Dong Duan
Keyword(s):  
Carbon Nanotubes ◽  
Percolation Threshold ◽  
Near Field ◽  
Cement Matrix ◽  
Ultrasonic Dispersion ◽  
Integrated Network ◽  
Cement Based Materials ◽  
Multi Walled Carbon Nanotubes ◽  
Electrode Method ◽  
Walled Carbon Nanotubes

Some multi-walled carbon nanotubes (NMWTs) were firstly dispersed in aqueous solution with surfactant ultrasonic dispersion process, then mixed into cement matrix, casting six groups cement-based materials filled with varying NMWTs additions (nwt) (NFCMs), and as comparison, the plain referential cement paste was fabricated. The ampere-volt (I-V) characteristics and percolation threshold of this type of nanocomposites were focused by four-electrode method. Results show that, the I-V features of the reference has obvious nonlinearity due to polarized reaction within cement hydrated electrolytes after being induced by passing 0~±30 V voltages, those of the NFCMs with six different nwt still have somewhat nonlinear traits, which mainly attribute to the double-layer coatings between NMWTs and out-encapsulated cement hydration isolation. The resistivity (ρ) of the NFCM nanocomposite steadily decreases with the increment of nwt, which contributes to superior capabilities of charge transporter and near-field emission of NMWTs, and the overlapped chance of physical contacts between conducting aggregates of NMWTs and bulk matrix increases by nwt enhancing; although there is still some fluctuation on ρ, but it becomes weaker and weaker by nwt increasing. The percolation threshold of the NFCMs is nwt being 2.0%, and the integrated network pathways at micro-scale form between NMWTs each other through the correspondent NFCM, also revealed in microstructure.

scholarly journals Axial Compressive Behavior of Reinforced Concrete (RC) Columns Incorporating Multi-Walled Carbon Nanotubes and Marble Powder

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 247
Author(s):  
Abdul Jalil Khan ◽  
Liaqat Ali Qureshi ◽  
Muhammad Nasir Ayaz Khan ◽  
Akhtar Gul ◽  
Muhammad Umar ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Compressive Strength ◽  
Reinforced Concrete ◽  
Main Property ◽  
Concrete Columns ◽  
Sem Analysis ◽  
Multiwalled Carbon ◽  
Reinforced Concrete Columns ◽  
Multi Walled Carbon Nanotubes ◽  
Marble Powder

In this study, Multiwalled Carbon Nanotubes (MWCNTs) and Marble Powder (MP) have been utilized in reinforced concrete columns to assess their structural behavior. The nanotubes from 0.025% to 0.20% and 5% MP by weight of cement were used. The compressive strength of reinforced concrete columns and cubes was analyzed as the main property. The incorporation of MWCNTs and marble powder was able to increase the compressive strength of columns by 72.69% and mortar by 42.45% as compared to reference concrete. The ductility was noted to be improved by 42.04%. The load-deformation and stress-strain behaviors were also analyzed. The Scanning Electron Microscopy (SEM) analysis revealed the formation of a strong compact bridge (90–100 layers), Calcium Silicate Hydrate (C-S-H) gel, evenly dispersion, and bridging effect caused by MWCNTs. The incorporation of 0.20% MWCNTs by weight of cement was recommended to be effectively used as a reinforcing agent in concrete.

The Experimental Determination of One-Axial Tensile Strength of the Textile Reinforced Concrete

2016 ◽  
Vol 827 ◽  
pp. 271-274
Author(s):  
Filip Vogel ◽  
Jan Machovec ◽  
Petr Konvalinka
Keyword(s):  
Tensile Strength ◽  
Reinforced Concrete ◽  
Experimental Testing ◽  
Testing Machine ◽  
Experimental Tests ◽  
Experimental Program ◽  
Cement Matrix ◽  
Textile Reinforced Concrete ◽  
Axial Tensile ◽  
Special Attachment

This article deals with experimental testing of the textile reinforced concrete samples. The main topic of this article is determination ultimate tensile strength of the textile reinforced concrete. The testing samples were in form “dogbone” for good fixing in testing machine. There are 12 samples totally in experimental program. One type cement matrix and three types (difference in their weight 125 g/m2, 275 g/m2 and 500 g/m2) glass textile reinforcement were used for the production of samples. The textile reinforcement is made of alkali-resistant glass fibres. Three samples were made of cement matrix and nine samples were made of cement matrix reinforced textile reinforcement (three of each type of reinforcement). The samples were tested in special attachment in one-axial tensile. Experimental tests were controlled by speed of rate of deformation (0.0005 m/min). The textile reinforcement has very good influence to behaviour of the textile reinforced concrete in tensile stress.

scholarly journals Electrical Properties of Carbon Nanotubes Cement Composites for Monitoring Stress Conditions in Concrete Structures

2011 ◽  
Vol 82 ◽  
pp. 118-123 ◽  
Author(s):  
Luigi Coppola ◽  
Alessandra Buoso ◽  
Fabio Corazza
Keyword(s):  
Carbon Nanotubes ◽  
Aqueous Solution ◽  
Reinforced Concrete ◽  
Compressive Stress ◽  
Smart Materials ◽  
Cement Matrix ◽  
Cementitious Composites ◽  
Impact Loads ◽  
Pressure Sensitivity ◽  
Cement Pastes

Cement pastes reinforced with Multi-Walled carbon NanoTubes (MWNTs) are smart materials with piezoresistivity properties. Adding carbon nanotubes to the cement matrix, in fact, the electrical resistivity of cementitious composites changes with the stress conditions under static and dynamic loads. This particular behaviour can be used to evaluate the stress level in reinforced concrete structures, to monitor the traffic flow, to weigh vehicles. In this paper data on pressure-sensitive behaviour under compressive stress of cement pastes and mortars containing different percentages (from 0.0% to 1.0% vs. cement mass) of MWNTs are presented.In order to form a conductive network and enhancethe piezoresistive properties of cementitious mixtures, Carbon NanoTubes (CNTs) need to be efficiently dispersed in the cement matrix. Two different methods to disperse CNTsin the cement matrix were used. The first one uses a surfactant (Sodium Linear Alkyl Benzene Sulphonate - LAS): MWNTs were dispersed in a LAS aqueous solution,and thenmixed with cement and a defoamer (tributyl phosphate) to decrease the air bubble in MWNT filled cement-based composites. The second method consists in mixing CNTs with about 50% of the mixing water in a becker by means of a glass wand. Then, the solution is sonicated by an ultrasonic generator for 10 minutes. Finally, the sonicatedCNT-aqueous solution ismixed with cement (and sand for the mortars). The piezoresistivity properties of the cementitious mixtures manufactured with the two above mentioned CNTs dispersing methods will be compared.Experimental results show that the electrical resistance changes synchronously with the compressive stress levelsfor the specimens manufactured with both methods. Therefore, CNTs improve the pressure-sensitivity of cementitious composites. Moreover, the piezoresistive response is better for cementitious composites manufactured by using the surfactant agent to disperse CNTs. Data indicate that – thanks to the better dispersion of nanotubes promoted by the surfactant - the pressure-sensitivity properties of cement pastes can be achieved even by using a very low percentage of CNTS (0.1% vs. cement mass). These findings seem to indicate that self-sensing CNTs/cement composite can be produced. These smart materials have great potential and they could be used in the next future in concrete field for practical applications to monitor the stress level of reinforced concrete elements subjected to static, dynamic and impact loads. In particular, informations on actual stress existing under dynamic and impact loads could be improve design procedures in protective structures.

The Experimental Testing of the Tensile Strength of the Steel Fibre Reinforced Cement Matrix

2015 ◽  
Vol 824 ◽  
pp. 197-200
Author(s):  
Jan Machovec ◽  
Filip Vogel ◽  
Petr Konvalinka
Keyword(s):  
Tensile Strength ◽  
Reinforced Concrete ◽  
Steel Fibre ◽  
Experimental Testing ◽  
Experimental Program ◽  
Cement Matrix ◽  
Textile Reinforced Concrete ◽  
Steel Reinforced Concrete ◽  
Test Steel ◽  
Reinforced Cement

This article is focused on state of knowledge about experimental testing of uniaxial tension strength of specimens from cement-based composites. We searched for various types of experimental testing of tensile strength, shapes of specimens or type of reinforcement. There is our own experimental program at the end of this article. Our aim is to find the best way to test steel fibre reinforced cement matrix for textile reinforced concrete in oneaxial tension. Textile reinforced concrete has many advantages (e.g.: no covering layer, higher ductility) and may be used instead of common steel reinforced concrete or as a method to repair old structures (e.g.: to bind columns).

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