Minimisation de la sensibilité à l'eau de composites cimentaires argile-schistes-bois

2000 ◽  
Vol 27 (1) ◽  
pp. 101-111 ◽  
Author(s):  
A Ledhem ◽  
R M Dheilly ◽  
M Benmalek ◽  
M Queneudec
Keyword(s):  
Liquid Water ◽  
Construction Materials ◽  
Thermal Characteristics ◽  
Boiling Water ◽  
Mechanical Resistance ◽  
Low Density ◽  
Wood Particles ◽  
The Matrix ◽  
Dimensional Variation ◽  
Sufficient Reduction

The use of clay and wood waste in construction materials points out to a sensitivity to water, which is susceptible to reduce their durability. This work has first been interested in the influence of different constituents on the extreme dimensional variations (EDV) of such cementing composites. A formulation allowing the conciliation of environmental imperatives, interesting mechanical and thermal characteristics, and low density has been proposed. However, the EDVs remain above the required objective. In order to reach this value, different treatments have been examined. The addition of alkali-resistant fiberglass in the matrix did not lead to satisfactory results. Not only is the reduction of the EDVs insufficient for reasonable proportions of fibers, but this treatment also increases the proportion of absorbed water in presence of liquid water. Taken separately, both types of treatments used for wood particles - neutralization with hydraulic binders and extraction with boiling water of hydro-soluble compounds - also do not allow a sufficient reduction of EDVs. However, the combination of these two treatments allows the achievement of EDV [Formula: see text] 1 mm/m. Such a treatment improves the mechanical resistance without significantly altering the thermal performances.Key words: wood concrete, extreme dimensional variation, fiberglass, neutralization, hydrolysis.[Journal translation]

ALCHEMI of B2-Ordered Fe50Al45Me5 alloys

1996 ◽  
Vol 54 ◽  
pp. 548-549
Author(s):  
Ian M. Anderson
Keyword(s):  
Room Temperature ◽  
Iron Aluminide ◽  
Low Density ◽  
Intermetallic Alloys ◽  
Practical Applications ◽  
Alloying Additions ◽  
Site Distribution ◽  
Good Corrosion Resistance ◽  
Room Temperature Ductility ◽  
The Matrix

B2-ordered iron aluminide intermetallic alloys exhibit a combination of attractive properties such as low density and good corrosion resistance. However, the practical applications of these alloys are limited by their poor fracture toughness and low room temperature ductility. One current strategy for overcoming these undesirable properties is to attempt to modify the basic chemistry of the materials with alloying additions. These changes in the chemistry of the material cannot be fully understood without a knowledge of the site-distribution of the alloying elements. In this paper, the site-distributions of a series of 3d-transition metal alloying additions in B2-ordered iron aluminides are studied with ALCHEMI.A series of seven alloys of stoichiometry Fe50AL45Me5, with Me = {Ti, V, Cr, Mn, Co, Ni, Cu}, were prepared with identical heating cycles. Microalloying additions of 0.2% B and 0.1% Zr were also incorporated to strengthen the grain boundaries, but these alloying additions have little influence on the matrix chemistry and are incidental to this study.

scholarly journals The Influence of Mixing Methods of Epoxy Composition Ingredients on Selected Mechanical Properties of Modified Epoxy Construction Materials

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 411
Author(s):  
Izabela Miturska ◽  
Anna Rudawska ◽  
Miroslav Müller ◽  
Monika Hromasová
Keyword(s):  
Tensile Strength ◽  
Epoxy Resin ◽  
Construction Materials ◽  
Preliminary Heating ◽  
Epoxy Composition ◽  
Mixing Speed ◽  
Adhesive Composition ◽  
Adhesive Compositions ◽  
The Matrix ◽  
Level Of Significance

The proper process of preparing an adhesive composition has a significant impact on the degree of dispersion of the composition ingredients in the matrix, as well as on the degree of aeration of the resulting composition, which in turn directly affects the strength and functional properties of the obtained adhesive compositions. The paper presents the results of tensile strength tests and SEM microphotographs of the adhesive composition of Epidian 57 epoxy resin with Z-1 curing agent, which was modified using three fillers NanoBent ZR2 montmorillonite, CaCO3 calcium carbonate and CWZ-22 active carbon. For comparison purposes, samples made of unmodified composition were also tested. The compositions were prepared with the use of six mixing methods, with variable parameters such as type of mixer arm, deaeration and epoxy resin temperature. Then, three mixing speeds were applied: 460, 1170 and 2500 rpm. The analyses of the obtained results showed that the most effective tensile results were obtained in the case of mixing with the use of a dispersing disc mixer with preliminary heating of the epoxy resin to 50 °C and deaeration of the composition during mixing. The highest tensile strength of adhesive compositions was obtained at the highest mixing speed; however, the best repeatability of the results was observed at 1170 rpm mixing speed. Based on a comparison test of average values, it was observed that, in case of modified compositions, the values of average tensile strength obtained at mixing speeds at 1170 and 2500 rpm do not differ significantly with the assumed level of significance α = 0.05.

scholarly journals Thermal and Mechanical Behavior of Elastomers Incorporated with Thermoregulating Microcapsules

2021 ◽  
Vol 11 (12) ◽  
pp. 5370
Author(s):  
Ana M. Borreguero ◽  
Irene Izarra ◽  
Ignacio Garrido ◽  
Patrycja J. Trzebiatowska ◽  
Janusz Datta ◽  
...  
Keyword(s):  
Latent Heat ◽  
Continuous Improvement ◽  
Low Density Polyethylene ◽  
Molar Ratio ◽  
Low Density ◽  
Minimum Particle Size ◽  
Synergy Effects ◽  
Elastomeric Materials ◽  
The Matrix ◽  
Spherical Microparticles

Polyurethane (PU) is one of the principal polymers in the global plastic market thanks to its versatility and continuous improvement. In this work, PU elastomeric materials having thermoregulating properties through the incorporation of microcapsules (mSD-(LDPE·EVA-RT27)) from low-density polyethylene and vinyl acetate containing paraffin®RT27 as PCM were produced. Elastomers were synthesized while varying the molar ratio [NCO]/[OH] between 1.05 and 1.1 and the microcapsule (MC) content from 0.0 to 20.0 wt.%. The successful synthesis of the PUs was confirmed by IR analyses. All the synthesized elastomers presented a structure formed by a net of spherical microparticles and with a minimum particle size for those with 10 wt.% MC. The density and tensile strength decreased with the MC content, probably due to worse distribution into the matrix. Elastomer E-1.05 exhibited better structural and stability properties for MC contents up to 15 wt.%, whereas E-1.1, containing 20 wt.% MC, revealed mechanical and thermal synergy effects, demonstrating good structural stability and the largest latent heat. Hence, elastomers having a large latent heat (8.7 J/g) can be produced by using a molar ratio [NCO]/[OH] of 1.1 and containing 20 wt.% mSD-(LDPE·EVA-RT27).

scholarly journals Aportes para el análisis comparativo del comportamiento higrotérmico y mecánico de los materiales de construcción con tierra

2019 ◽  
Vol 22 (1) ◽  
Author(s):  
María Guadalupe Cuitiño-Rosales ◽  
Rodolfo Rotondaro ◽  
Alfredo Esteves
Keyword(s):  
Building Materials ◽  
Thermal Characteristics ◽  
Mechanical Resistance ◽  
Secondary Sources ◽  
Earth Construction ◽  
Palabras Clave ◽  
Concrete Blocks ◽  
Vernacular Building ◽  
Natural Building ◽  
Earth Block

Resumen Se analizan las características térmicas y de resistencias mecánicas de materiales y elementos constructivos elaborados con suelos naturales estabilizados. La metodología parte de la recopilación bibliográfica de fuentes primarias, secundarias e información de ensayos propios, sobre la densidad, la conductividad térmica y las resistencias a la compresión, a la flexión y al corte correspondientes al adobe, los bloques de tierra comprimida (BTC), la tapia y la quincha, según diferentes autores. Además, se consideraron los valores establecidos por normas argentinas IRAM referidas al acondicionamiento térmico de edificios. Se elaboraron comparaciones entre sí y con algunos materiales industrializados, tales como los bloques de hormigón, los ladrillos cerámicos huecos y los ladrillos cocidos macizos. A partir de este análisis, se concluyó que la revisión bibliográfica no es suficiente para obtener una estandarización de los valores de conductividad y transmitancia térmica de los materiales y los elementos constructivos naturales. Así mismo, a partir de las comparaciones de valores se pudo observar cómo se relacionan la densidad de los materiales y la de los morteros, según las distintas técnicas, con el comportamiento térmico y las resistencias mecánicas. Palabras clave: Adobe; arquitectura sostenible; bahareque; bloque de tierra comprimida-BTC; materiales vernáculos de construcción; propiedades térmicas; quincha; resistencia mecánica; tapial   Comparative analysis of the thermal aspects and mechanical resistances for materials and elements of earth construction Abstract The thermal characteristics and mechanical resistance of some materials and constructive elements elaborated with stabilized natural soils are analyzed. The methodology took into account the bibliographic compilation of primary and secondary sources and information from own tests, on density, thermal conductivity and resistance to compression, flexion and cutting, corresponding to adobe, BTC, tapia and wattle and daub, according to different authors. In addition, it was considered the values established by Argentine standards IRAM referring to the thermal conditioning of buildings. Comparisons were made with each other and with some industrialized materials such as concrete blocks, hollow ceramic bricks, and solid fired bricks. From this analysis, it was concluded that the literature review is not enough to obtain a standardization conductivity and thermal transmittance values of natural building materials and elements. Furthermore, from the comparisons of values it was possible to observe how the density of materials and mortars, according to the different techniques, are related to thermal behavior and mechanical resistance. Keywords: Adobe; sustainable architecture; bahareque; compressed earth block (BTC); vernacular building materials; thermal properties; quincha; mechanical strength; tapial; wattle; daub   Recibido: octubre 22 / 2018  Evaluado: septiembre 10 / 2019  Aceptado: octubre 15 / 2019 Publicado en línea: noviembre de 2019                               Actualizado: noviembre de 2019

scholarly journals New approach to the formation of organo-inorganic borosyloxane polymer structures

2019 ◽  
Vol 57 (2) ◽  
pp. 35-40
Author(s):  
Alexander B. Zachernyuk ◽  
◽  
Boris A. Zachernyuk ◽  
Ekaterina N. Solovyova ◽  
Vladimir I. Nedelkin ◽  
...  
Keyword(s):  
Boron Oxide ◽  
Sol Gel ◽  
Thermal Characteristics ◽  
Inorganic Materials ◽  
Organic Modifiers ◽  
Synthesis Time ◽  
Transparent Films ◽  
Boric Anhydride ◽  
The Matrix ◽  
Synthetic Approaches

Using sol-gel methods, new synthetic approaches to the preparation of boron-containing organic-inorganic hybrid polymers based on boron oxide (boric anhydride), which is a part of many inorganic materials, have been developed. Previously, such methods were used to obtain amorphous silicate glasses and their use allows introducing various inorganic and organic modifiers into the matrix of silicon dioxide and other compounds at temperatures up to 120 °C. Within the framework of this work: a) the conditions for obtaining saturated solutions of boron oxide in organic solvents were found and it was found that boric anhydride is most completely dissolved in triethyl orthoformiate (approximately 25%) at 110-110 °C retaining its structure; b) by the condensation of boric acid with 1,3-dichlorotetraphenyl disiloxane, functional borcyclosiloxanes were synthesized to further modify boron oxide. The reaction conditions, spectral and thermal characteristics of condensation products were investigated. It is shown the increasing in the synthesis time to 15-18 h, a bicyclic borsiloxane is formed; c) homophasic modification of boric anhydride with monofunctional cyclic borsiloxanes was carried out and it was shown that the formation of Si-O-B bonds at 110-120 °C occurs due to the use of anhydrous sol-gel process. Transparent films are obtained from modified boric anhydride solutions deposited on glass and stainless steel, followed by curing at a temperature of 160-280 °C, that are not subjected to hydrolysis under the action of air moisture and are stable in air up to 600 °C. As a result of the work, the possibility of obtaining a borsiloxane type polymeric structures having an inorganic molecular skeleton modified with organosilicon compounds has been investigated.

scholarly journals PRODUCTION OF PARTICLE BOARDS USING POLYSTYRENE AND BAMBOO WASTES

2017 ◽  
Vol 36 (3) ◽  
pp. 788-793
Author(s):  
SA Abdulkareem ◽  
AG Adeniyi
Keyword(s):  
Physical Properties ◽  
National Standards ◽  
Low Density ◽  
Thickness Swelling ◽  
The Matrix ◽  
Curing Methods

This investigation was able to produce incredibly strong particleboards using bamboo and resinous material obtained from Polystyrene wastes. The particleboards were prepared by mixing the bamboo fibres and Polystyrene based resin (PBR) followed by flat press process at different ratio (v/v). Physical properties were measured, with reference to normal and oven curing methods, according to the ASTM D-1037 standard. Thickness Swelling (TS) of the samples were measured after 2 and 24 hours of immersion in water at 25oC temperature. It was found that the physical properties of particleboards with 20%, 30% and 40% PBR content were all in agreement with low density particleboard classification of American National Standards Institute (ANSI). TS increased as the PBR content decreased in the matrix. Obtained properties convincingly indicate superior bonding ability of the synthesised resinous polystyrene over known industrial adhesives typically used for particleboard production. http://dx.doi.org/10.4314/njt.v36i3.18 

scholarly journals Cyclodextrins and Cyclodextrin Derivatives as Green Char Promoters in Flame Retardants Formulations for Polymeric Materials. A Review

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 664 ◽  
Author(s):  
Maria Paola Luda ◽  
Marco Zanetti
Keyword(s):  
Flame Retardants ◽  
Environmental Concern ◽  
Fire Retardant ◽  
Polymeric Materials ◽  
Poly Lactic Acid ◽  
Mechanical Resistance ◽  
Self Healing ◽  
Cyclodextrin Derivatives ◽  
The Matrix ◽  
Fire Retardance

Polymers are intrinsically flammable materials; hence, fire retardance (FR) is required in their most common applications (i.e., electronic and construction, to mention some). Recently, it has been reported that cyclodextrin (CD) and cyclodextrin derivatives are beginning to be introduced into Intumescent Fire Retardant (IFR) formulations in place of pentaerythritol, which is used in IFRs that are currently on the market. Since IFRs are of less environmental concern than their hazardous halogen containing counterparts, the use of natural origin compounds in IFRs provides a way to comply with green chemistry issues. BCD and BCD derivatives presence in IFR mixtures promotes a higher yield of blowing gases and char when polymeric materials undergo combustion. Both processes play important roles in intumescence. The key rule to obtain in insulating compact char is the good dispersion of the nanoparticles in the matrix, which can be achieved by functionalizing nanoparticles with BCD derivatives. Moreover, CD derivatives are attractive because of their nanosized structure and their ability to form inclusion complexes with many compounds used as FR components, reducing their release to the environment during their shelf life of FR items. Often, fire retardance performed by BCD and BCD derivatives accompanies other relevant properties, such as improved mechanical resistance, washability resistance, self healing ability, thermal conductivity, etc. The application of CD fire retardant additives in many polymers, such as poly(lactic acid), poly(propylene), poly(vinyl acetate), poly(methyl methacrylate), linear low density poly(ethylene), polyamides, and polyesters are comprehensively reviewed here.

The synthesis of organically modified layered double hydroxide and its effect on the structure and physical properties of low-density polyethylene/ethylene–vinyl acetate blends

2019 ◽  
Vol 27 (5) ◽  
pp. 287-298
Author(s):  
Xincheng Guo ◽  
Mengqi Tang ◽  
Na Wang ◽  
Lingtong Li ◽  
Yifan Wu ◽  
...  
Keyword(s):  
Vinyl Acetate ◽  
Layered Double Hydroxide ◽  
Organic Anion ◽  
Ethylene Vinyl Acetate ◽  
Degree Of Crystallinity ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Organically Modified ◽  
The Matrix ◽  
Double Hydroxide

Organically modified layered double hydroxide (OM-LDH) was synthesized via anion exchange reaction and potassium monolauryl phosphate (MAPK) was used as an intercalator. The OM-LDH nanofillers were embedded into low-density polyethylene/ethylene–vinyl acetate (LDPE/EVA) via melt blending process which provided LDPE/EVA/OM-LDH nanocomposites. The structure and properties of the fabricated samples were characterized through Fourier transform infrared spectroscopy, X-ray diffraction techniques, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, and tensile testing. The results showed that the organic anion was intercalated into the interlayer region of LDH and enlarged the interlayer distance. The TGA results of the nanocomposites showed significantly improved thermal stability at a higher temperature when containing 6 wt% OM-LDH due to the good dispersion of OM-LDH in the matrix. The DSC data indicated that the degree of crystallinity was increased obviously due to the incorporation of OM-LDH in the matrix. The formation of organic side chains on the OM-LDH surface also contributed to an improvement in the interfacial adhesion, resulting in enhanced tensile strength and elongation at break compared with LDH.

On the durability of low-density polyethylene nanocomposites

e-Polymers ◽  
2004 ◽  
Vol 4 (1) ◽  
Author(s):  
Jitendra K. Pandey ◽  
Raj Pal Singh
Keyword(s):  
Ir Spectroscopy ◽  
Morphological Changes ◽  
Diffusion Path ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Neat Polymer ◽  
The Matrix ◽  
Ft Ir ◽  
The Stability ◽  
Artificial Uv

Abstract Low-density polyethylene (PE) containing nano-particulate clay was prepared after functionalization with maleic anhydride (MA) by reactive grafting in the presence of peroxide followed by blending of maleated PE with neat polymer in different concentrations. Four classes of composites were obtained: (i) exfoliated, (ii) intercalated, (iii) microcomposites, and (iv) intermediate of intercalated and microcomposites, as evidenced by wide-angle X-ray diffraction. All samples were kept for artificial UV irradiation (λ ≥ 290 nm) and for composting to study their photo- and bio-durability. Fourier-transform IR spectroscopy (FT-IR) and scanning electron microscopy were used to monitor the functional group and morphological changes, respectively, whereas biodurability was evaluated by measuring the weight loss. MA functionalization and nature of composites have detrimental effects on the overall durability of composites. Nanocomposites showed higher resistance than microcomposites during initial weathering and composting with a long induction period. The stability of nanocomposites decreases with time and overall durability was worse than of pristine polymer in both environments. It was concluded that the initial protection is due to the filler-generated long diffusion path, which decreases the oxygen diffusion through the matrix. The bio-durability of composites decreased with oxo-degradation. Biodegradation of PE nanocomposites during composting follows the mechanism described by Albertsson et al. as evidenced by FT-IR spectroscopy.

Innovative Composites with Carbon Nanofillers for Self-Sensing Structural RC Beams

2018 ◽  
Vol 19 ◽  
pp. 12-22 ◽  
Author(s):  
A. D'Alessandro ◽  
A. Meoni ◽  
F. Ubertini
Keyword(s):  
Research Work ◽  
Construction Materials ◽  
Reinforced Concrete Beam ◽  
The Self ◽  
Electrical Performance ◽  
Structural Safety ◽  
Cement Pastes ◽  
The Matrix ◽  
Behavior Modifications ◽  
Carbon Nanofillers

The progress of nanotechnology resulted in the development of new instruments in the civil engineering and its applications. In particular, the use of carbon nanofillers into the matrix of construction materials can provide enhanced properties to the material in both of mechanical and electrical performance. In constructions, concrete is among the most used material. Due to the peculiarities of its components and its structure, it is suitable to modifications, at the nanometer level too. Moreover, to guarantee structural safety it is desirable to achieve a diffuse monitoring of structures in order to identify incipient situations of damages and possible risk for people. The ideal solution would be to realize structures able to identify easily and quickly their behavior modifications. This paper presents a research work about the characterization of the self-sensing abilities of novel cementitious composites with conductive carbon nanoinclusions and their application into a structural reinforced concrete beam. The self-sensing evidence is achieved through the correlation between the variation of strains and the variation of electrical resistance or resistivity. Nanomodified cement pastes with different carbon nanofillers has been tested. The experimental campaign shows the potentialities of this new types of sensors made of nanomodified concrete for diffuse Structural Health Monitoring.

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