scholarly journals Reinforcing Effect of Carbon Nanotubes/Surfactant Dispersions in Portland Cement Pastes

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Oscar A. Mendoza Reales ◽  
Caterin Ocampo ◽  
Yhan Paul Arias Jaramillo ◽  
Juan Carlos Ochoa Botero ◽  
Jorge Hernán Quintero ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Cement Matrix ◽  
Multiwalled Carbon ◽  
Element Analysis ◽  
Cement Pastes ◽  
Reinforcing Effect ◽  
Linear Elastic ◽  
Crack Propagation Process ◽  
Negative Effect ◽  
The Individual

Decoupling the individual effects of multiwalled carbon nanotubes (MWCNTs) and surfactants when used as reinforcement materials in cement-based composites is aimed in this study. Powder MWCNTs were dispersed in deionized water using different types of surfactants as chemical dispersing agents and an ultrasonic tip processor. Cement pastes with carbon nanotubes additions of 0.15% by mass of cement were produced in two steps: first, the MWCNT/surfactant dispersions were combined with the mixing water, and then, cement was added and mixed until a homogeneous paste was obtained. Mechanical properties of the pastes cured at 7 days were measured, and their fracture behavior was characterized using the linear elastic finite element analysis. It was found that the reinforcing effect of MWCNT was masked by the negative effect of surfactants in the cement matrix; nevertheless, nanotubes were capable of increasing both stress and strain capacity of the composite by controlling the crack propagation process at the tip of the crack.

scholarly journals Dispersion of Carbon Nanotubes with Different Types of Superplasticizer as a Dispersing Agent for Self-Sensing Cementitious Materials

2021 ◽  
Vol 11 (18) ◽  
pp. 8452
Author(s):  
Pedro de Almeida Carísio ◽  
Yasmim Gabriela dos Santos Mendonça ◽  
Carlos Fernando Teodósio Soares ◽  
Oscar Aurelio Mendoza Reales ◽  
Eduardo de Moraes Rego Fairbairn ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Cementitious Materials ◽  
Cement Matrix ◽  
Cement Pastes ◽  
Sensing Applications ◽  
Dispersing Agent ◽  
Vis Spectroscopy ◽  
Different Types ◽  
Conductive Fillers ◽  
Dispersing Agents

Due to their exceptional electrical properties, carbon nanotubes (CNTs) can be applied as conductive fillers to develop self-sensing cement-based matrices. In order to obtain an adequate self-sensing response, CNTs must be evenly dispersed through the cement matrix in a volume sufficient enough to create an electric percolation network. This is challenged by the difficulty of dispersing CNTs; therefore, there is a demand for an efficient dispersing agent that can be filled by superplasticiezers, which are products of known compatibility with cement and high availability. This research explores the use of four commercial superplasticizers available in Brazil, both naphthalene and ether polycarboxylate-based, as dispersing agents for CNTs in water. Ultrasonic energy was applied to aqueous solutions containing CNTs and superplasticizers. UV–Vis spectroscopy and ξ-potential measurements were used to investigate which superplasticizer was more effective to disperse the CNTs. Cement pastes were produced with the CNT dispersions and their electrical resistivity was measured. It was found that only superplasticizers without aliphatic groups in their structure were capable of dispersing CNTs in water. It was concluded that second-generation naphthalene-based superplasticizers were more efficient dispersing agents for CNTs than third-generation ether polycarboxylate-based ones for self-sensing applications.

Flexural Performance of Polyurethane/Multi Walled Carbon Nanotubes Foam Composites

2015 ◽  
Vol 754-755 ◽  
pp. 8-12 ◽  
Author(s):  
A.A. Sinar ◽  
Zainuddin Firuz ◽  
M.A. Nur Azni ◽  
M.A. Hazizan ◽  
H.A. Sahrim
Keyword(s):  
Carbon Nanotubes ◽  
Flexural Strength ◽  
Sandwich Composites ◽  
Multiwalled Carbon ◽  
Element Analysis ◽  
Test Analysis ◽  
Average Value ◽  
Pu Foam ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

Polyurethane (PU)/multiwalled carbon nanotubes (MWCNTs) foam composites were produced by reaction of based palm oil polyol (POP) with methylene diphenyl diisocyanate (MDI). The MWCNTs were added into PU foam with the percentages varied from 0 wt.% to 3 wt.%. Sandwich composites were prepared using hand lay-up method where Aluminium (Al) sheet as skin were stacked onto PU foam using Araldite adhesives. The PU/MWCNTs foam composites (PMFC) and PU/MWCNTs foam sandwich composites (PMFSC) were characterized using flexural test analysis. Observation showed higher value of flexural strength for PMFC and PMFSC at 0.5% incorporation of MWCNTs. The flexural strength of sandwich PU foam is higher with an average value of 159.38% than control PU foam, due to Al sheet act as ductile skin and prevents samples from rupture rapidly. The modeling using finite element analysis (NX Software-version 8.5) showed the displacement nodal magnitude for 0.5% PMFC (2.537 mm) are higher than 0.5% PMFSC (0.288 mm).

scholarly journals Cement Pastes and Mortars Containing Nitrogen-Doped and Oxygen-Functionalized Multiwalled Carbon Nanotubes

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Mauricio Martínez-Alanis ◽  
Florentino López-Urías
Keyword(s):  
Carbon Nanotubes ◽  
Compressive Strength ◽  
Multiwalled Carbon Nanotubes ◽  
Density Functional ◽  
Multiwalled Carbon ◽  
Cement Pastes ◽  
Hydrated Calcium Silicate ◽  
Nitrogen Doped ◽  
Cementitious Matrix ◽  
Functionalized Multiwalled Carbon Nanotubes

Cement pastes and mortars based on ordinary Portland cement containing nitrogen-doped multiwalled carbon nanotubes (MWCNT-Nx) or oxygen-functionalized multiwalled carbon nanotubes (MWCNT-Ox) are investigated. To incorporate MWCNTs into the cementitious matrix, the as-produced carpets are dispersed over periods of 1 and 2 hours in distilled water at pH levels of 1 and 7. The cement pastes are prepared by adding 0.1 wt% of MWCNTs to cement powder, followed by characterization with SEM and X-ray diffraction (XRD) at an early age (first hours of hydration). The mortars are mechanically characterized during the hydration process for a period of 28 days. SEM characterization of cement pastes revealed that the carbon nanotubes are well incorporated in the cementitious matrix, with the hydrated cement grains interconnected by long carbon nanotubes. XRD characterizations demonstrated that, during the hydration of cement pastes, different peaks emerged that were associated with ettringite, hydrated calcium silicate, and calcium hydroxide, among other structures. Results of the compressive strength measurements for mortars simultaneously mixed with MWCNT-Nx and MWCNT-Ox reached an increment of approximately 30% in compressive strength. In addition, density functional theory calculations were performed in nitrogen-doped and oxygen-functionalized carbon nanotubes interacting with a cement grain.

scholarly journals Rheological Properties of Cement Pastes with Multiwalled Carbon Nanotubes

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Gintautas Skripkiunas ◽  
Ekaterina Karpova ◽  
Irmantas Barauskas ◽  
Joana Bendoraitiene ◽  
Grigory Yakovlev
Keyword(s):  
Carbon Nanotubes ◽  
Rheological Properties ◽  
Yield Stress ◽  
Multiwalled Carbon Nanotubes ◽  
High Performance ◽  
High Performance Concrete ◽  
Plastic Viscosity ◽  
Multiwalled Carbon ◽  
Cement Pastes ◽  
Rheological Test

The evaluation of rheological properties of cement systems is getting more relevant with growing interest to self-consolidating concrete (SCC), high-performance concrete (HPC) and ultrahigh-performance concrete (UHPC). The rheology models are a perspective tool to predict and manage the properties of cement systems in the fresh and hardened state. The current research is focused on the rheological test of cement systems modified by multiwalled carbon nanotubes (MWCNT) dispersion with and without polycarboxylate ether (PCE). The content of dispersion with 1% concentration of MWCNT in cement pastes varied from 0.125 to 0.5% by weight of cement. The dosage of PCE was taken as 0.6% by weight of cement. The cement pastes were prepared based on Portland cement without mineral additives. The rheological test was carried out at 5, 30, 60, and 120 min after mixing of cement paste. The rheological test established that modification of cement pastes by MWCNT dispersion in dosage 0.25% leads to the decrease of yield stress by 30.7% and increase of plastic viscosity by 29.6%. The combined modification by PCE and MWCNT dispersion shows the decrease in plastic viscosity of cement pastes by 9.90% in dosage of MWCNT equal to 0.5% by weight of cement, reduction of water demand by 20% for the same workability, and decrease of yield stress till 0 Pa. It gives the ability to obtain the self-compacting mixtures. The cement pastes with and without MWCNT dispersion revealed the shear-thinning behavior during 120 min after mixing. The modification of cement pastes by PCE with and without MWCNT dispersion showed the shear-thickening behavior which remains during 120 min after mixing.

Limit loads for knuckle-encroaching nozzles in torispherical heads: Experimental verification of finite element predictions

2002 ◽  
Vol 37 (4) ◽  
pp. 313-326 ◽  
Author(s):  
M. F Hsieh ◽  
D N Moreton ◽  
J Mistry ◽  
D. G Moffat
Keyword(s):  
Finite Element ◽  
Pressure Vessels ◽  
Element Analysis ◽  
Limit Loads ◽  
Testing Procedures ◽  
Linear Elastic ◽  
Predicted Values ◽  
The Individual ◽  
Experimental Pressure

The manufacturing and testing procedures for two experimental pressure vessels with large nozzles encroaching into the knuckle region of the vessel head are described. Experimental linear elastic stress levels and plastic loads for pressure and combined axial and in-plane bending nozzle loads are compared with predicted values determined using non-linear finite element analysis. The quality of the results are considered to justify the procedures developed by the authors to conduct a parametric study of the individual limit loads and their interaction for these complex structures.

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.

Studies of Carboxyl-Functionalized Multi-Wall Carbon Nanotubes and Mechanical Properties of its MWCNTs-OPC Cement Composites

2013 ◽  
Vol 774-776 ◽  
pp. 499-502
Author(s):  
Jing Xin Yang ◽  
Yong Zhi Xu
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Cement Matrix ◽  
Acid Oxidation ◽  
Cement Composites ◽  
Multiwalled Carbon ◽  
Multi Wall Carbon Nanotubes ◽  
Pristine Mwcnts ◽  
Uniform Dispersion ◽  
Nitric Acid Oxidation

This study successfully grafted multiwalled carbon nanotubes (MWCNTs) with carboxyl group (MWCNTs-COOH) via concentrated nitric acid oxidation reaction. The morphologies of MWCNTs oxidized under various conditions and the extent of dispersion of the MWCNTs in the cement matrix were characterized using fourier transform infrared spectroscopy (FTIR). This investigation also optimized the mechanical properties of MWCNTs-OPC cement composites by utilizing pristine MWCNTs (P-MWCNTs) and modified MWCNTs (MWCNTs-COOH) through a combination of dispersion method. Micrographs of MWCNTs incorporated cement samples revealed uniform dispersion of MWCNTs in cement, good interfacial adhesion between MWCNTs and cement, and improved interfacial bonding between MWCNTs-OPC cement at 0.4 wt.% loading. An improved dispersion and hence an improved crosslink interaction between MWCNTs-COOH and cement lead to the stronger shift of the mechanical properties of the cement composites.

The Dispersivity of Multi-Walled Carbon Nanotubes (NMWTs) and Pressure-Sensitive Property of NMWTs Reinforced Cement Composite

2009 ◽  
Vol 60-61 ◽  
pp. 475-479 ◽  
Author(s):  
Jian Lin Luo ◽  
Zhong Dong Duan
Keyword(s):  
Carbon Nanotubes ◽  
Applied Pressure ◽  
Wheatstone Bridge ◽  
Cement Composite ◽  
Cement Matrix ◽  
Ultrasonic Dispersion ◽  
Multi Wall Carbon Nanotubes ◽  
Pressure Sensitive ◽  
Reinforced Cement ◽  
The Individual

The individual and/or combinatory impacts of two surfactants (polyoxyethylene nonyl phenyl ether 10 (Tx-100), Arabic gum powder (AG)) on the dispersivity of multi-wall carbon nanotubes (NMWTs) were firstly investigated and evaluated through naked and microstructures observation; hereafter, NMWTs with 1.0% loading were firstly dispersed in aqueous solution with surfactant ultrasonic dispersion process, and cast-mixed into cement matrix to fabricate 2 groups NMWTs reinforced cement composites (NMTRCs), associated with the plain reference. Wheatstone bridge configurations were simultaneously employed to obtain the resistances and the monoaxial stresses, to investigate the pressure-sensitive properties of these nanocomposites. Results with naked observation reveal that either Tx-100 or AG at some concentration has good dispersion effect on NMWTs, the blackness homogeneity and stability of NMWTs suspended solution could retain more than 15 d; yet microstructures results show that NMTRC with AG has more homogeneous dispersion impact and more compatible with cement hydration than that with Tx-100. Results related on the pressure-sensitive properties of NMTRCs demonstrate that, the fractional change in resistivity of NMTRC with AG linearly falls down by increment of applied pressure within elastic range, this good pressure-sensitive traits mainly contribute to the increasing chance of physical contacts, the denser of current chargers between NMWTs, and the shortened trend of the potential barrier widths between NMWTs and matrix by increment of pressure, after efficient dispersion with AG. Yet that of NMTRC with Tx-100 has not good linearity descending trend, but some exaggerate fluctuations, and that of the reference has also no any regular descending trend.

scholarly journals Piezoresistivity of Cement Matrix Composites Incorporating Multiwalled Carbon Nanotubes due to Moisture Variation

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Yanfeng Wang ◽  
Xiaohua Zhao ◽  
Yi Zhao
Keyword(s):  
Carbon Nanotubes ◽  
Moisture Content ◽  
Multiwalled Carbon Nanotubes ◽  
Volume Fraction ◽  
Ionic Conduction ◽  
Cement Matrix ◽  
Cementitious Composites ◽  
Multiwalled Carbon ◽  
Moisture Condition ◽  
Moisture Variation

Cementitious composites usually work under moisture condition. Presently, the piezoresistivity of cementitious composites incorporating multiwalled carbon nanotubes (MWCNTs) due to moisture variation was experimentally investigated. The variation of moisture content was controlled by drying specimens in an oven. In most cases of moisture content, the composites were observed to present positive piezoresistivity during the process of cyclic compression. While moisture content was in a specific range, the composites exhibited negative piezoresistivity. The whole transition from positive piezoresistivity to negative piezoresistivity and then positive piezoresistivity was obtained with moisture variation. Moreover, the amplitude of piezoresistivity changed in the process. These phenomena may be explained through the combination of ionic conduction and electronic conduction. A theoretical model of piezoresistivity, able to predict the effects of porosity, the volume fraction of MWCNTs, and the connectivity parameters, is proposed. Numerical results with the model show that the calculated piezoresistive responses of specimens agree reasonably well with testing data.

Sign in / Sign up

Export Citation Format

Share Document