Cement as a thermoelectric material

2000 ◽  
Vol 15 (12) ◽  
pp. 2844-2848 ◽  
Author(s):  
Sihai Wen ◽  
D. D. L. Chung
Keyword(s):  
Thermoelectric Power ◽  
Cement Paste ◽  
Carbon Fibers ◽  
Cement Matrix ◽  
Electron Conduction ◽  
Cement Pastes ◽  
Hole Conduction ◽  
Reinforced Cement ◽  
The Absolute ◽  
Short Carbon

Cement pastes containing short steel fibers, which contribute to electron conduction, exhibit positive values (up to 68 μV/°C) of the absolute thermoelectric power. Cement pastes containing short carbon fibers, which contribute to hole conduction while the cement matrix contributes to electron conduction, exhibit negative or slightly positive values of the absolute thermoelectric power. The hole and electron contributions in carbon fiber reinforced cement paste are equal at the percolation threshold. Addition of either steel or carbon fibers to cement paste yields more reversibility and linearity in the variation of the Seebeck voltage with temperature difference (up to 65 °C).

scholarly journals Paper 1: “Cement as a Thermoelectric Material,” [J. Mater. Res. 15, 2844-2848 (2000)] And Paper 2: “Rectifying and Thermocouple Junctions Based on Portland Cement,” J. Mater. Res. 16, 1989-1993 (2001)]

2004 ◽  
Vol 19 (4) ◽  
pp. 1294-1294 ◽  
Author(s):  
Sihai Wen ◽  
D.D.L. Chung
Keyword(s):  
Portland Cement ◽  
Seebeck Coefficient ◽  
Thermoelectric Power ◽  
Carbon Fibers ◽  
Thermoelectric Material ◽  
Steel Fibers ◽  
Cement Pastes ◽  
The Absolute ◽  
P Type ◽  
Wrong Sign

In the two papers listed above, the conversion of the Seebeck coefficient (relative to copper) to the absolute thermoelectric power was done by using the wrong sign of the absolute thermoelectric power of copper (2.34 μV/°C). The corrected tables are shown below for both papers. The correction means that plain cement paste is slightly p-type rather than slightly n-type. In addition, it means that cement pastes with carbon fibers are more p-type and those with steel fibers are less n-type than reported. Note in Table III of Paper 2 that all cement pastes are p-type except for paste (ii). Note in Table IV of Paper 2 that all cement junctions are pn-junctions (rather than some being nn+-junctions).

Influence of Oxygen Plasma Surface Treatment of PET Micro Fibers on Flexural Strength of Reinforced Cement Pastes

2016 ◽  
Vol 825 ◽  
pp. 73-76
Author(s):  
Jan Trejbal ◽  
Jan Bartoš ◽  
Lubomír Kopecký ◽  
Pavla Ryparová ◽  
Štěpán Potocký
Keyword(s):  
Surface Treatment ◽  
Oxygen Plasma ◽  
Fiber Surface ◽  
Cement Matrix ◽  
Cement Pastes ◽  
Softening Behavior ◽  
Plasma Surface Treatment ◽  
Water To Cement Ratio ◽  
Reinforced Cement ◽  
Fiber Surface Treatment

Presented work deals with PET (polyethylene terephthalate) fiber-reinforced cement pastes and cool oxygen plasma fiber surface treatment used to attain the better adhesion between fibers surface and the cement matrix. Three sets of cement paste samples were made with the same matrix (CEM I 42.5R with water to cement ratio equal to 0.4). The two sample sets contained micro fiber reinforcement varying in surface properties. One set was reinforced with unmodified fibers, while in to the other set plasma treated fibers were used. As a comparative indicator to bending response of the composite materials, four-point destructive tests were carried out. The samples reinforced with unmodified fibers exhibited deflection-softening behavior during the post-cracking phase, while samples with plasma treated fibers exhibited deflection-hardening behavior.

scholarly journals Effect of Cellulose Nanocrystals on the Properties of Cement Paste

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Qiaoling Liu ◽  
Yujiao Peng ◽  
Long Liang ◽  
Xiaobin Dong ◽  
Hancai Li
Keyword(s):  
Cement Paste ◽  
Cellulose Nanocrystals ◽  
Nitrogen Adsorption ◽  
Cement Matrix ◽  
Size Distributions ◽  
Cement Pastes ◽  
Curing Conditions ◽  
X Ray ◽  
Pore Size Distributions ◽  
X Ray Computed

The effect of the addition of cellulose nanocrystals (CNCs) on the properties of cement pastes is studied herein. The compressive strength of CNC/cement paste was investigated under the curing conditions defined in this study. Two-dimensional micrographs and pore size distributions were obtained by scanning electron microscopy, X-ray computed tomography (XCT), and nitrogen adsorption. The addition of CNCs was found to significantly enhance the mechanical properties of cement pastes with a rapid decrease in temperature and humidity. XCT and nitrogen adsorption analyses show that the addition of CNCs leads to a refinement of the pore structure in the cement matrix. Almost no hydration products, including C-S-H, are formed in the cement matrix without CNCs under extreme conditions. This is in contrast with the results for the cement paste with 0.5% CNCs.

Strain sensing using carbon fiber

1999 ◽  
Vol 14 (3) ◽  
pp. 790-802 ◽  
Author(s):  
Xiaojun Wang ◽  
Xuli Fu ◽  
D. D. L. Chung
Keyword(s):  
Carbon Fiber ◽  
Carbon Fibers ◽  
Matrix Composite ◽  
Epoxy Matrix ◽  
Strain Sensors ◽  
Cement Matrix ◽  
Strain Sensing ◽  
Fractional Change ◽  
Epoxy Matrix Composite ◽  
Short Carbon

Carbon fiber provides strain sensing through change in electrical resistance upon strain. Due to piezoresistivity of various origins, a single carbon fiber in epoxy, an epoxy-matrix composite with short carbon fibers (5.5 vol%), a cement-matrix composite with short carbon fibers (0.2–0.5 vol%), and an epoxy-matrix composite with continuous carbon fibers (58 vol%) are strain sensors with fractional change in resistance per unit strain up to 625. A single bare carbon fiber is not piezoresistive, but just resistive.

Measurements of Thermoelectric Behavior and Microstructure of Carbon Nanotubes/Carbon Fiber-Cement Based Composite

2011 ◽  
Vol 492 ◽  
pp. 242-245 ◽  
Author(s):  
Jun Qing Zuo ◽  
Wu Yao ◽  
Jun Jie Qin ◽  
Hai Yong Cao
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Fiber ◽  
Thermoelectric Power ◽  
Interfacial Adhesion ◽  
Calcium Silicate Hydrate ◽  
Sem Analysis ◽  
Cement Matrix ◽  
Experimental Setup ◽  
Porous Microstructure ◽  
The Absolute

Thermoelectric behavior and microstructure of carbon nanotubes/carbon fiber(CNTs/CF)- cement based composite have been measured in this study. An self-made experimental setup was applied to test the thermoelectric power (TEP) of the composites. The results show that the higher the CNTs content, the less positive the absolute thermoelectric power is. When CNTs addition incresed to 1.0% by weight of cement, the absolute thermoelectric power changed sign from positive to negative. Scanning electron microscopy (SEM) was used to characterize the morphology of CNTs, CF and the structure of Portland cement-CNTs-CF systems. SEM analysis of the results show that good interfacial adhesion between CNTs and cement matrix is seen with CNTs tightly wrapped by Calcium-Silicate-Hydrate (C-S-H). With the incorporation of CNTs/CF in cement based composite, the cement-CNTs-CF system exhibits a porous microstructure.

scholarly journals Mechanical Attributes of Uniaxial Compression for Calcium Carbonate Whisker Reinforced Oil Well Cement Pastes

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Yuanyi Yang ◽  
Shun Fu ◽  
Xingkui Li
Keyword(s):  
Uniaxial Compression ◽  
Cement Paste ◽  
Strain Curve ◽  
Oil Well ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Cement Pastes ◽  
Oil Well Cement ◽  
Reinforced Cement ◽  
Well Cement

It is crucial for design and safety of the cementing sheath to develop better understanding of the CaCO3 whisker reinforced oil well cement pastes. The uniaxial compression curve, mechanical constitutive relation, and reinforcing mechanism of the CaCO3 whisker reinforced oil well cement pastes are studied in this script. The results indicate that the CaCO3 whisker under the 10% dosage could improve the tensile strength of the cement paste significantly. The peak stress, elasticity modulus, and the energy at different stages of the stress-strain curve of the CaCO3 whisker reinforced cement paste are reinforced with the increasing of CaCO3 whisker. Afterward, the constitutive model of stress-strain curve, the toughness index, and capability coefficients index of the CaCO3 whisker reinforced cement paste are established. A physical model of the interface layer is also established and the micromechanical reinforcement is related to the double film layer between the CaCO3 whisker and cement matrix which could be bonded with much more fastness to the cement surface. The development of this script provides new ways to analyze the toughening mechanism of CaCO3 whisker and establishes a correlation between basic material structure and the physical properties.

Nanomechanical Performance of Interfacial Transition Zone in Fiber Reinforced Cement Matrix

2018 ◽  
Vol 760 ◽  
pp. 251-256 ◽  
Author(s):  
Vojtěch Zacharda ◽  
Petr Štemberk ◽  
Jiří Němeček
Keyword(s):  
Elastic Modulus ◽  
Transition Zone ◽  
Cement Paste ◽  
Steel Fiber ◽  
Mechanical Performance ◽  
Creep Compliance ◽  
Interfacial Transition Zone ◽  
Cement Matrix ◽  
Average Value ◽  
Reinforced Cement

This paper shows a micromechanical study of interfacial transition zone (ITZ) around steel fiber in cement paste. It investigates microstructure and mechanical performance of the ITZ by a combination of nanoindentation and scanning electron microscopy (SEM). The investigated specimens were made from cement CEM I 42.5R paste with dispersed reinforcement in the form of steel fiber TriTreg 50 mm. The SEM demonstrated larger porosity and smaller portion of clinkers in the ITZ. Nanoindentation delivered values of elastic modulus, hardness and creep parameters around the fiber. An average value of elastic modulus in ITZ was at the level of 67% in comparison with cement bulk and the width of ITZ was about 40 µm. The value of hardness was found to be 60% of the average hardness of the bulk cement paste. The measured load-displacement curves were used for calculation of creep indentation parameter (CIT) and the creep compliance function. An average value of the creep compliance in the ITZ was found to be two times higher than in the cement bulk.

scholarly journals Development and analysis of sponge gourd (Luffa cylindrica L.) fiber-reinforced cement composites

BioResources ◽  
2019 ◽  
Vol 14 (4) ◽  
pp. 9981-9993
Author(s):  
Victor A. Querido ◽  
José Roberto M. d’Almeida ◽  
Flávio A. Silva
Keyword(s):  
Cement Paste ◽  
Natural Fiber ◽  
Vascular System ◽  
Cement Matrix ◽  
Cement Composites ◽  
Fiber Reinforced ◽  
Luffa Cylindrica ◽  
3D Network ◽  
Sponge Gourd ◽  
Reinforced Cement

Sponge gourd (Luffa cylindrica L.) fiber-reinforced cement composites were developed and analyzed. Dried sponge gourd fruit’s fibrous vascular system forms a natural 3D network that can reinforce matrices in composite materials, diverting cracks along the complex array of 3D interfaces between the fibers and the cementitious matrix. To avoid fiber deterioration, the cement paste was modified by incorporating pozzolanic materials. The fibers were mechanically characterized by tensile testing of strips of the 3D natural fiber array and of single fibers extracted from the array. The fibers had an average tensile strength of 140 MPa and an average Young’s modulus up to 28 GPa. Image analysis showed that the fiber spatial distribution inside the 3D network was random. The modified cement paste was characterized by its workability (flow table test) and mechanical behavior (compression and three-point bending tests), with average results of 430 mm, 62.7 MPa, and 6.2 MPa, respectively. Under bending, the cement matrix collapsed after the first crack. The sponge gourd-cement composite manufactured with 1 wt% of fibers showed an average flexural strength of 9.2 MPa (approximately 50% greater than the unreinforced matrix). Importantly, the composite also presented a limited deflection-hardening behavior. These results support sponge gourd’s possible use as reinforcement in cement matrix composites.

scholarly journals The Effect of Fiber Geometry and Interfacial Properties on the Elastic Properties of Cementitious Nanocomposite Material

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Ala G. Abu Taqa ◽  
Rashid K. Abu Al-Rub ◽  
Ahmed Senouci ◽  
Nasser Al-Nuaimi ◽  
Khaldoon A. Bani-Hani
Keyword(s):  
Elastic Modulus ◽  
Cement Paste ◽  
Parametric Study ◽  
3D Model ◽  
3D Models ◽  
Cement Matrix ◽  
Fiber Waviness ◽  
Axisymmetric Model ◽  
Three Phase ◽  
Reinforced Cement

This paper investigates the elastic (Young’s) modulus of carbon Nanotube- (CNT-) reinforced cement paste using 3D and axisymmetric models using Abaqus software. The behavior of the CNT and the cement matrix was assumed to be fully elastic while the cohesive surface framework was used to model the interface. To investigate the effect of fiber waviness on the value of the elastic modulus, 3D models were developed assuming different distributions of fibers. The results obtained using the 3D model were compared to those obtained using the simplified three-phase axisymmetric model which consists of one single CNT aligned in the center of composite unit cell, an interface, and cement matrix. A parametric study was then carried out using the axisymmetric model to study the role of the interface in the composite elastic modulus without accounting for the presence of the interfacial transition zone (ITZ or interphase). The results showed that the CNTs waviness significantly reduced their reinforcing capability in the cement paste. On the other hand, the results obtained using the axisymmetric model were found to be in good agreement with those obtained using the 3D model. Moreover, the results of the parametric study showed that the interface properties significantly affect the composite elastic modulus and alter its behavior.

scholarly journals A Study on Improving the Mechanical Performance of Carbon-Fiber-Reinforced Cement

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2715 ◽  
Author(s):  
Yeou-Fong Li ◽  
Tzu-Hsien Yang ◽  
Chang-Yu Kuo ◽  
Ying-Kuan Tsai
Keyword(s):  
Carbon Fiber ◽  
Carbon Fibers ◽  
Pure Water ◽  
Fiber Bundles ◽  
Fiber Reinforced ◽  
Short Carbon Fiber ◽  
Reinforced Cement ◽  
Carbon Fiber Reinforced ◽  
Short Carbon ◽  
Carbon Fiber Bundles

This study investigated several approaches for silane-removal from the surface of short carbon fiber bundles, and short carbon fibers uniformly dispersed in cement to produce a novel compound of carbon-fiber-reinforced cement. In order to facilitate the uniform distribution of short carbon fibers in the carbon-fiber-reinforced cement, it is necessary to remove the silane from the carbon fiber’s surface. Short carbon fiber bundles were submerged into a pure water, sodium hydroxide solution, and acetic acid solution, and placed in high-temperature furnace used to remove silane from the carbon fiber surface. The results were observed under a scanning electron microscope to determine the level of silane removal from the surface, and an effective method for removing the silane was developed from among the several approaches. This method employed a pneumatic dispersion device to disperse carbon fibers then mixed in a high-early-strength cement which led to an excellent compressive and impact-resistance performance of carbon-fiber-reinforced cement. Final testing showed that the compressive strength and impact energy increased by 14.1% and 145%, respectively.

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