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Copyright of Revista Foco (Interdisciplinary Studies Journal) is the property of Revista Foco and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effects of adding zircon and synthesized TiO2 nanoparticles (NPs) to standard porcelain tiles on mechanical and optical properties were studied. The obtained TiO2 nanoparticles had an average particle size of 7.47 nm. The optical properties of TiO2 NPs were characterized by using UV–visible spectrophotometer. The synthesized TiO2 NPs and commercial zircon were added to standard porcelain tile composition at a rate of 1%, 2% and 4% by weight. Phase analyzes of the samples were made with XRD, and microstructure analyzes were made with SEM/EDS. Optical dilatometer test was used for sintering studies and densification behaviour was observed with water absorption test. The optical behaviour of the samples was analyzed using spectrophotometric measurements (CIELab method). As a result of this test, it was observed that nano-sized titanium oxide can be used as a whitening agent in porcelain tiles. In addition, the additives made to porcelain tiles also contributed to the increase in mechanical properties. Resumen: Se estudiaron los efectos de añadir circón y nanopartículas (NP) de TiO2 sintetizadas a baldosas de gres porcelánico estándar sobre las propiedades mecánicas y ópticas. Las nanopartículas de TiO2 obtenidas tenían un tamaño medio de partícula de 7,47 nm. Las propiedades ópticas de las NP de TiO2 se caracterizaron utilizando un espectrofotómetro UV-visible. Las NP de TiO2 sintetizadas y el zircón comercial se agregaron a la composición estándar de baldosas de porcelana a razón de del 1, el 2 y el 4 en peso. Los análisis de fase de las muestras se realizaron con XRD y los análisis de microestructura se realizaron con SEM/EDS. Se utilizó la prueba del dilatómetro óptico para los estudios de sinterización y se observó el comportamiento de densificación con la prueba de absorción de agua. El comportamiento óptico de las muestras se analizó mediante medidas espectrofotométricas (método CIELab). Como resultado de esta prueba, se observó que el óxido de titanio de tamaño nanométrico se puede utilizar como agente blanqueador en gres porcelánico. Además, los aditivos realizados en el gres porcelánico también contribuyeron al aumento de las propiedades mecánicas.

Se determinaron las tolerancias dimensionales y la evaluación de la resistencia mecánica de una rueda dentada de dientes recto ubicada en el mando final de un Bulldozer Komatsu D85A-18 la cual presenta problemas de cálculo y redimensionamiento. Al emplear los procedimientos del cálculo se obtuvieron resultados que satisfacen la condición de resistencia y el buen funcionamiento de la pieza en la transmisión.

La madera es un material biológico con aplicaciones en ingeniería y arquitectura. Su módulo de rigidez es útil para el cálculo de vigas que trabajan en flexión y en torsión. El objetivo de la investigación fue determinar los módulos de rigidez y los índices materiales de Pinuspseudostrobus, Tabebuiaroseay Quercusscytophylla.Se realizaron pruebas dinámicas de torsión en 35probetas de pequeñas dimensiones decada una de las especies. Se calcularon las correlaciones lineales y sus coeficientes de determinación de los módulos de rigidez en función de la densidad y de la frecuencia. Los principales resultados son: Las magnitudes de las densidades de las maderas de P. pseudostrobus, T. roseay Q. scytophyllase ubican al interior del intervalo:587 kg m-3, 735 kg m-3. El coeficiente de variación de las frecuencias para Q. scytophyllaes 50% menor comparativamente con los coeficientes de P. pseudostrobusy T. rosea. El coeficiente de variación para P. pseudostrobuses 23% mayor que el de T. roseay 146% mayor que el de Q. scytophylla. Se concluye que los valores reportados en esta investigación pueden ser útiles si estas especies de maderas se utilizan con fines estructurales.

Copyright of Brazilian Journal of Production Engineering / Revista Brasileira de Engenharia de Produção is the property of Brazilian Journal of Production Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

La dirección de proyectos de construcción, respetando el entorno y los parámetros ambientales es un tema ya abordado con anterioridad en multitud de trabajos científicos. Éste trabajo tiene como objetivo comparar y analizar los distintos parámetros ambientales derivados del análisis del ciclo de vida, concretamente en la etapa de producto, fases A1, A2 y A3 y los costes económicos incurridos en una estructura modelo, utilizando diferentes hormigones armados HA25, HA30, HA35, HA40, HA45 y HA50. Demostrando la utilidad que tiene para los directores de proyectos en el proceso de toma de decisiones, disponer de un análisis comparativo de parámetros medioambientales frente al coste económico. Éste estudio se ha realizado sobre una estructura en concreto, por lo que los resultados obtenidos son propios del edificio analizado. Sería muy interesante realizar éste estudio sobre una muestra de estructuras más amplia. Se podría, de ese modo, analizar cómo influyen en los parámetros ambientales otros factores como la geometría, la utilización de diferentes soluciones estructurales o diferentes datos de cálculo, como las cargas de viento o nieve. Abstract The management of construction projects, respecting the environment and environmental parameters, is a subject that has already been addressed in many scientific works. The aim of this work is to compare and analyse the different environmental parameters derived from the life cycle analysis, specifically in the product stage, phases A1, A2 and A3 and the economic costs incurred in a model structure, using different reinforced concretes HA25, HA30, HA35, HA40, HA45 and HA50, demonstrating how useful it is for project managers in the decision-making process to have a comparative analysis of environmental parameters versus economic cost. This study has been carried out on a specific structure, so the results obtained are specific to the building analysed. It would be very interesting to carry out this study on a larger sample of structures. In this way, it would be possible to analyse how other factors such as geometry, the use of different structural solutions or different calculation data, such as wind or snow loads, influence the environmental parameters.

Se analizó la influencia de la proporción de arena en morteros Tipo II según norma N-CMT-2-01-004/02 empleando tres tipos de áridos de la región de Morelia, Michoacán determinando su influencia en sus propiedades físico-mecánicas, contemplando el uso de diferentes materiales cementantes (MC): el cemento Portland más cal (B1), cemento Portland más cemento de albañilería (B2). Se elaboraron mezclas para B1 y B2 con relaciones en volumen arena/MC, desde 2.25 hasta 4, determinando la fluidez, resistencia a compresión uniaxial (UCS) y resistividad eléctrica húmeda (WER). Se estudió la relación entre la fluidez y la cantidad de agua/MC, concluyendo que el tipo de árido y proporciones modifican la fluidez y demanda de agua en estado fresco impactando en UCS y WER.

La cornamenta del toro de lidia es la parte anatómica más delicada de este animal, dado que su carácter ofensivo y estresable hace que sufra lesiones traumáticas durante el año previo a la lidia. Actualmente, se protege el cuerno con una funda de fibra de vidrio, con el objetivo de proteger su integridad. Con este trabajo, se pretende estudiar la resistencia mecánica del cuerno del toro de lidia; se analiza la posible influencia del enfundado. Para ello, se ha recogido cuernos de 50 toros de lidia de 4 a 5 años; 25 de ellos habían sido enfundados 6 meses antes de su lidia. Se ha analizado la resistencia mecánica del cuerno: cepa, pala y pitón; se utiliza el equipamiento Instron Electropulse E10000, siguiendo una metodología similar a la empleada por Horcajada et al. (2009). Se realiza tres pruebas de resistencia mecánica: compresión directa, tracción indirecta y flexo-tracción. Todas reflejaron una alta resistencia del cuerno, sin diferencias entre sus partes. Se observa un efecto beneficioso del enfundado, favorece el espesor del estuche de queratina en la cepa del cuerno; el cual fue mayor en los cuernos de los animales enfundados. Además, se comprueba una mayor resistencia de los cuernos enfundados en la prueba de tracción indirecta. Por otra parte, los cuernos de mayor longitud y diámetro resistieron presiones más altas, absorbiendo el hueso cornal, mayoritariamente, la presión ejercida.

Copyright of Ciência Florestal (01039954) is the property of Ciencia Florestal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista de la Asociación Geológica Argentina is the property of Asociacion Geologica Argentina and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

En el presente artículo, se realiza un estudio de la resistencia a la tracción de diferentes depósitos de soldadura sobre láminas de la aleación de aluminio AA2024-T3 AlClad. La soldabilidad de la aleación, bajo procesos de arco, se considera limitada por su sensibilidad al agrietamiento en caliente y, por ello, se encuentra ampliamente estudiada en procesos de estado sólido o láser, en los que la afectación térmica es menor. La investigación tiene como objetivo estudiar el comportamiento mecánico de dicho aluminio al soldarlo con tecnología local. Para la experimentación, se realizaron depósitos con combinaciones de electrodo no consumible punto violeta, electrodo no consumible punto verde, metal de aporte ER4043 y sin metal de aporte (soldadura autógena). Los ensayos mecánicos estuvieron bajo el estándar ASTM E8 y bajo las recomendaciones del estándar AWS D1.2. Adicionalmente, se realizó el respectivo estudio de las superficies de fractura de cada uno de los depósitos. Entre los resultados, se destaca la notable reducción tanto de resistencia mecánica como de ductilidad, lo cual se debió a la alta presencia de porosidad, que desencadenó grietas de diversos tamaños, ligados, también, a una fragilización por hidrógeno y por presencia de partículas de segunda fase en los límites de grano.

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.

Copyright of Revista de la Asociación Odontológica Argentina is the property of Asociacion Odontologica Argentina and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work aims to evaluate the effect of thermal modification on the physical and mechanical properties of species of wood, from an agroforestry system. The species evaluated were Parapiptadenia rigida (Benth.) Brenan, Peltophorum dubium (Spreng.) Taub., Eucalyptus grandis × Eucalyptus urophylla and Schizolobium parahyba (Vell.) Blake, aged nine. The specimens were submitted to thermal treatments (120, 150, 180 and 210 °C), in addition to the control samples. For the mechanical properties, the modules of elasticity and rupture, tension in the proportional limit and maximum force were evaluated according to ASTM D 143-94. For the physical properties of basic density and shrinkage, the evaluation took place according to NBR 7190. The thermal treatment modified the mechanical properties of the wood in a positive way up to 180 °C, with the highest values being observed for E. grandis × E. urophylla and P. rigida. Likewise, the heat treatment has modified the physical properties of wood retractability in a positive way up to 210 °C, with the anisotropic coefficient decreasing with increasing temperature. Thus, it is concluded that the thermal modification alters the physical and mechanical properties of the four analyzed species. Furthermore, it is perceived that for the case of mechanical characteristics these changes are positive up to a temperature of 180 °C, while for the physical ones the best results are found at a temperature of 210 °C. [ABSTRACT FROM AUTHOR]

Copyright of DYNA - Ingeniería e Industria is the property of Publicaciones Dyna SL and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Resumen Objetivo: Describir las fallas en diferentes sistemas de implantes al ser sometidos a fuerzas de torsión creciente, determinar el torque en el cual aparece un daño medible en el implante o alguno de sus componentes y especificar la falla más frecuente. Materiales y métodos: Se realizó un estudio experimental in vitro. Se utilizaron 88 implantes agrupados según diseño y marca comercial (Federa, Rosterdent, Biomet 3i, Tree-Oss, B&W, ML) en 11 grupos de 8 implantes cada uno. Éstos fueron inmovilizados en acrílico y fijados en una prensa. Se aplicó una fuerza de torsión creciente con torquímetro de precisión digital hasta la aparición de alguna falla en el implante o sus componentes. Se registró el torque en el que se produjo la falla. Se realizó estadística descriptiva para el análisis de datos. Resultados: El 100% de los implantes o alguno de sus componentes mostraron una falla detectable al ser sometidos a fuerzas de torsión creciente (rango de torque: 83,5 Ncm –implante con conexión cono morse 8 grados– a 384 Ncm –implante de conexión interna sin montar–). El torque promedio más bajo en el que aparecieron los daños fue 103,75 (±8,08) Ncm para implantes de conexión interna tipo cono morse, mientras que el más alto fue 279,87 (±89,73) Ncm para implantes de conexión interna sin montar. La falla más frecuente (28,4%) fue la fractura del tornillo del portaimplante y falseo del hexágono externo simultáneamente. Conclusión: Las fallas detectables a fuerzas de torsión creciente ocurrieron entre 83,5 Ncm y 384 Ncm. La falla reiterada fue la fractura del tornillo del portaimplante y falseo del hexágono simultáneamente. Palabras clave: daños mecánicos, fractura por sobrecarga, implantes dentales, resistencia mecánica, torque de inserción// Abstract Aim: To describe the failures in different implant systems when subjected to increasing torsional forces, determine the torque at which measurable damage occurs to the implant or one of its components, and determine the most frequent failure. Materials and methods: This was an experimental in vitro study. A total 88 implants were used, grouped according to design and trademark (Federa, Rosterdent, Biomet 3i, Tree-Oss, B&W, ML) into 11 groups of 8 implants each. The implants were immobilized in Duralay acrylic and fixed in a vice. Increasing torsional force was applied with a digital precision torque wrench until the occurrence of any failure in the implants or their components. The torque at which the failure occurred was recorded. Descriptive statistics were performed for data analysis. Results: 100% of the implants or any of their components showed a detectable failure when subjected to increasing torsional forces (force range: 83.5 Ncm in an implant with 8-degree Morse taper connection to 384 Ncm in an implant with unmounted internal connection). The lowest average torque at which damage occurred was 103.75 (±8.08) Ncm for conical implants with Morse internal connection, while the highest was 279.87 (±89.73) Ncm for implant with unmounted internal connection. The most frequent failure (28.4%) was fracture of the implant retaining screw and distortion of the external hexagon simultaneously. Conclusion: Detectable failures at increasing torsional forces occurred between 83.5 Ncm and 384 Ncm. The repeated failure was the fracture of the implant retaining screw and simultaneous distortion of the hexagon. Key words: dental implants, insertion torque, mechanical damage

Copyright of Revista Ciencia y Poder Aéreo is the property of Escuela de Postgrados de la Fuerza Aerea Colombiana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Se establecieron los parámetros de diseño de los componentes de un aerogenerador rápido de baja potencia, compuesto por rotor, palas, palas suplementarias y el árbol, combinando materiales de madera, aluminio al 13 % silicio y acero AISI 1045; para generar una potencia eólica de 305,75 W obtenida de una potencia del viento de 120,102 W donde el equipo será capaz de entrega 305,75 W/h con un rendimiento eólico del 32 %. Los componentes mecánicos, debido al momento torsor ocasionado por la fuerza centrífuga del viento, podrán girar hasta 477 r/min y transmitir un par torsional igual a 2 294 Nm. El cálculo de las condiciones de resistencia arroja a tracción es de 68,75 MPa y el esfuerzo admisible, teniendo en cuenta el coeficiente de seguridad y la resistencia a la rotura de 7,75x107 Pa, ambos parámetros inferiores a los valores permisibles. A través del análisis de los esfuerzos por el método de elementos finitos y aplicando los criterios de Von Mises se muestran las tensiones que se distribuyen a lo largo del árbol sometido a la torsión, valores máximos que soporta el árbol central de 1,577 MPa; el desplazamiento máximo de 6,62x10-6 MPa y mínimo 1,13x10-10 MPa en los elementos 7 063 y 3 128, respectivamente.

Un geopolímero a base de metacaolin fue fabricado con 5 proporciones de dos nanomateriales diferentes. Por un lado, nanowhiskers de carburo de silicio y, por otro lado, nanopartículas de dióxido de titanio. Ambos fueron colocados en agua y recibieron energía ultrasónica para ser dispersados. Fueron analizadas los efectos sobre las propiedades mecánicas y la cinética de reacción. Comparados con la matriz de referencia, los resultados evidenciaron una tendencia al incremento de la resistencia a la flexión. Probablemente por la geometría de los nanowhiskers de SiC y el refinamiento de poros por las partículas de nano-TiO2. Las curvas de calorimetría mostraron que al incorporar nanopartículas de TiO2 se obtuvo una reducción del 92 % en el calor total, mientras que, los nanowhiskers de SiC produjeron una reducción del 25 % en el calor total.

The necessity of environmental preservation of natural stone materials, the high costs that involves paving works and environmental liabilities generated by Reclaimed Asphalt Pavement (RAP), turns essential the search for alternative inputs to enhance the sustainability of the road environment. The research is based on laboratory tests in mixtures of RAP, powdered rock and Portland cement, with the objective of determining possible traits with different RAP contents to be used in base and sub-base of pavements. To develop the study, RAP was collected from highway BR-287, while the powdered rock is of basaltic origin of Serra Geral Formation. For chemical stabilization, due to its availability in the region, was chosen the use of the pozzolanic cement, CP IV-32. The granulometric ranges were used as reference of specification DNIT-ES 141/2010, adopting six blends of materials estabilized granulometrically and chemically. The samples were subjected to four specific tests: particle size distribution, Proctor compaction, compressive strength and compressive strength by diametral tensile. The tests for the determination of mechanical properties had healing time of 7, 14 and 28 days. By analyzing the results, it was observed that all mixture obtained satisfactory results in relation to NBR 12253 (ABNT, 1992), evidencing the potential use of RAP as an aggregate for mixtures to be used in floor support layers of pavement.

En este artículo se plantea la fabricación de ladrillos de plástico fundido con virutas producto del mecanizado como un elemento constructivo. En este trabajo el material utilizado es el polietileno de tereftalato, mejor conocido como PET. Los ladrillos fabricados permitieron comprobar y obtener una buena resistencia mecánica a la compresión, en comparación con ladrillos convencionales. Por otra parte, ayudan a reducir la contaminación ambiental. Es una propuesta autosustentable debido a que se utilizan como materia prima materiales reciclados (PET y virutas metálicas), promoviendo el uso de los recursos disponibles, en lugar de quemarlos o desecharlos.

In recent decades, the search for raw from renewable resources to produce polymers, elastomers, resins, foams, etc., has intensified; these materials would reduce the industrial use of petrochemical compounds. In this work, the oil extracted from the castor oil seed (Ricinus communis) was used because of ricinoleic acid content (92.3%), it is of easy production and non-edible vegetable origin. The polyurethane adhesive was synthesized through transesterification and polymerization reactions. Using the corresponding standards, this adhesive was applied to sheets of Guadua angustifolia Kunth for determining its mechanical characteristics, the compressive strength parallel to the fiber was 43±3 (MPa), and shear parallel to the fiber was 5.9±0.9 (MPa). Fourier transform infrared spectroscopy was used for determining the appropriate molar ratio and monitoring the reaction during the synthesis and final product structure was analyzed with X-ray diffraction. Through differential scanning calorimetry, the glass transition temperature of the product was estimated on -24.6 °C; the thermal relaxation technique was used to measure its specific heat, while its thermal diffusivity and thermal expansion coefficient were estimated with the photoacoustic technique. [ABSTRACT FROM AUTHOR]

Efecto de las condiciones de atomización electrohidrodinámica sobre las características morfométricas y la resistencia mecánica de las partículas de mucílago de chía y alginato Electrohydrodynamic atomization (EHDA) is a technique which produces monodispersed particles and can employ food grade biopolymers as wall materials, such as chia mucilage. The aim of this work was to study the changes on the morphometric characteristics (Feret, roundness) and mechanical resistance of chia mucilage-sodium alginate microparticles obtained at different process conditions (voltage: 11–14 kV; distance to collector 5.5–8.5 cm). The diameter of particles was ≤1 mm, being more deformed (roundness, RD < 0.61), with higher mechanical strength (MS: 7–7.5 N) and Weber numbers (9.9 x 10−5 – 3.7 × 10−4) than those processed without voltage. A descriptive model relating We and process parameters was developed, being corroborated by Pearson analysis, and observing correlations larger than 0.8 between We with Feret and MS (0.817, 0.807), and Feret with MS and voltage (0.837, 0.826). These results confirmed the feasibility of applying EHDA to produce chia mucilage-sodium alginate particles with different morphologies and mechanical characteristics depending on process conditions. [ABSTRACT FROM AUTHOR]

In this work, a metacaolin-based geopolymer was fabricated with 5 proportions of two different nanomaterials. On the one hand, silicon carbide nanowhiskers and on the other hand, titanium dioxide nanoparticles. Both were placed into water and received ultrasonic energy to be dispersed. The effects on mechanical properties and reaction kinetics were analyzed. Compared to reference matrix, the results showed a tendency to increase on flexural strength. Probably due to the geometry of SiC nanowhiskers and the pores refinement caused by nano-TiO2 particles. Calorimetry curves showed that incorporating TiO2 nanoparticles was a reduction in total heat (92%) at 24 hours, while SiC nanowhiskers achieves a reduction less intense at total heat (25%) at the same time. [ABSTRACT FROM AUTHOR]

Copyright of Revista de Arquitectura (1657-0308) is the property of Universidad Catolica de Columbia, Facultad de Arquitectura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

O uso de nanomateriais em diversas campos da ciência vem crescendo nos últimos anos, sendo que na construção civil sua aplicação ainda se encontra em estágios iniciais. Como os nanotubos de carbono são um dos materiais mais resistentes conhecidos, possuem uma flexibilidade considerável e alta relação de aspecto, estes apresentam um grande potencial de utilização na construção civil. Diante disso, o objetivo deste trabalho foi investigar a influência da adição de 0,1% de nanotubos de carbono em pastas de cimento no que se refere ao comportamento mecânico. Para a avaliação das propriedades mecânicas foram realizados ensaios de resistência à compressão e resistência à tração por compressão diametral aos 7 dias. Para avaliação da microestrutura do material foram utilizados ensaios de microscopia eletrônica de varredura. Os resultados apontaram um ganho de resistência mecânica aos 7 nas pastas com 0,1% adição de nanotubos.

Este trabajo estudia las propiedades mecánicas y físicas de hormigones estructurales fabricados con áridos reciclados obtenidos de residuos de construcción y demolición. Se han seleccionado mezclas con una relación específica agua / cemento y una sustitución de agregados gruesos y finos similares. Se han comparado los resultados de la deformación, la resistencia a la compresión, la resistencia a la rotura por fraccionamiento, el módulo estático de elasticidad, la deformación por contracción, la densidad aparente y los ensayos de absorción de agua. Los datos muestran que las propiedades más afectadas debido a la sustitución de agregados naturales por agregados reciclados son la trabajabilidad, el módulo de elasticidad, la deformación por contracción y la absorción de agua. Abstract This work studies the mechanical and physical properties of structural concretes made by recycled aggregates obtained from construction and demolition waste. Mixes with a specific water/cement ratio and a similar coarse and fine aggregate substitution have been selected. Results from slump, compressive strength, splitting tensile strength, static modulus of elasticity, shrinkage strain, bulk density and water absorption tests have been compared. The data show that the most affected properties because of natural aggregate substitution for recycled aggregates are workability, modulus of elasticity, shrinkage strain and water absorption.

Copyright of 3C Tecnologia is the property of Area de Innovacion y Desarrollo, SL and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Solid waste is a reality of modern society, contributing to consequences in the planning and management of industries and urban centers. Thus, the reuse of these wastes for the production of various materials appears as an alternative. Mining is a sector of the economy that discards large volumes of material in tailings dams and sterile piles, making it important to search reuse of these materials in order to minimize environmental impacts. This study search to analyze the technical feasibility of soil substitution by magnetic tailings generated in phosphate rock processing in the production of soil-cement bricks. Tests of mechanical resistance to compression, absorption and density measurement were performed. The results indicate bricks with mechanical resistance and superior density and inferior absorption to the molded brick for control. Therefore, this preliminary study allows to conclude that it is possible the partial replacement of the soil by magnetic waste in the production of soil-cement bricks, obtaining similar or better characteristics. [ABSTRACT FROM AUTHOR]

This experimental research was carried out with the objective of implementing materials such as expanded clay (also known as arlite) and pumice stone, as a total replacement of conventional aggregates in the production of concrete. Mix designs were developed with expanded clay and pumice stone completely saturated and unsaturated. The mixture consisted of cement, water, pumice stone and expanded clay, in some cases additives were used such as polypropylene fibers, silica fume and superplasticizer, the latter was used to study the increase in the resistance to bending and compression of concrete. For this, cylinders, joists and panels were made; obtaining densities of 1300 to 1500 Kg / m3 and compressive strengths of 13 to 18 MPa. Accompanied by equilibrium density tests for lightweight concrete, percentage of voids, capillary absorption and scanning electron microscopy (SEM); in order to identify some properties of the aggregates and concrete. In this way it can be shown that expanded clay and pumice can be considered as an alternative to common aggregates in the production of concrete in the country. [ABSTRACT FROM AUTHOR]

Copyright of Bistua: Revista de la Facultad de Ciencias Básicas is the property of Facultad de Ciencias Basicas de la Universidad de Pamplona and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bone defects have been treated implanting autologous, allogeneic or tissues, however, the success of these procedures depends of biocompatibility, fixation with the tissue, physicochemical characteristics and the complications related to the extraction of autologous grafts, such as the limited amount of bone to be extracted, the morbidity in the place of extraction and the potential risks of infectious nature, therefore, arise the Tissue Engineering where the superficial and mechanical properties of the biomaterials used play an important role in material-tissue interaction. In this investigation, porous bodies of hydroxyapatite were developed by gel-casting and they were coated with chitosan at different concentrations to verify the influence of coating on the mechanical properties and stability of the manufactured porous bodies, comparing the properties obtained with of the bone for trying to improve the requirements for implants. For those, pore morphology, compressive strength and degradability the porous bodies were evaluated with and without coating, and the results showed that the porous bodies have properties of mechanical strength and adequate morphology for use in regeneration of bone tissue, confirming considerably improvements in these and demonstrating an effective and efficient shielding of the porous bodies of HA under physiological conditions. higher concentration of chitosan with respect to the porous bodies of uncoated HA. [ABSTRACT FROM AUTHOR]

The direct use of agricultural and forestry waste as energy source is not efficient since they generally have low calorific value and density, the resides compaction can be a solution to those problems. The compacted residues are denser than the unprocessed waste, because of that, it has higher energy per volume unit. The objective of this work was to evaluate the quality of pellets manufactured from coconut fiber and cotton residues; both collected in the state of Córdoba-Colombia. It was made twelve experimental pellets, testing three different binders (corn, cassava and banana) in two different percentages (10 and 30%) and two types of pellets were made without the addition of any binders. After two weeks, the PDI (durability) for all treatments was determined according to the ASABE 269.4 standard. The moisture content and particle size in the materials were also determined. The PDI of pellets produced without binders was compared with the PDI of pellets with binders. The results showed that both pellets had PDI higher than 97.95% and statistically there were no significant differences when the type of binder varied. It was therefore, possible to produce pellets with good quality without the use of binders, using coconut fiber and cotton residues only, with particle sizes of less than 2 mm (10 mesh) and moisture content between 10 and 15%. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Wood Science / Revista Ciência da Madeira is the property of Brazilian Journal of Wood Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents the development of the unconfined compressive (qu) and the splitting tensile strength (qt) of a chemically stabilized silt soil. For this, specimens with a volume of 196,35 cm3 were prepared using cement contents of 3%, 5%, 7% and 9% and then tested after 7 days of cure. The porosity/volumetric cement content (η/Civ) was used as the main parameter of the results analysis. The results show that with the decrease in the ratio η/Civ the values of qu and qt increase. Thus, the decrease in porosity meant an increase in qu and qt. A general estimation equation for qu and qt was developed to estimate the resistance of the mixtures with the use of η/Civ adjusted to a scalar equal to 0,45. The equations showed that it is possible to estimate the value of qu and qt of treated soil among the amounts of cement, η/Civ ratio and curing time employed in the present work. Finally, a constant ratio of qt/qu=0,15, which is independent of the voids and the volumetric content of cement, was calculated. [ABSTRACT FROM AUTHOR]

Este trabajo aporta una novedosa metodología para incrementar la resistencia mecánica de materiales porcelánicos. Para lograr este objetivo, se utilizó un polvo constituido por feldespato sódico y arcillas. El polvo fue humectado hasta un 8% en peso con agua. Posteriormente fueron conformadas probetas de sección rectangular por prensado uniaxial a 21 MPa. Las probetas secas se sinterizaron en un horno de laboratorio a una temperatura máxima de 1.218 °C. A continuación las probetas fueron sometidas a un tratamiento químico de intercambio iónico con el objetivo de incrementar sus propiedades mecánicas, también conocido por templado químico. La temperatura y el tiempo del tratamiento químico fueron variados según un diseño factorial. Los resultados mostraron un incremento de ∼74% en la resistencia a la rotura del material. Eso proporcionó una reducción del espesor del material de aproximadamente un 15%. Por consiguiente, este trabajo mostró que el proceso de templado químico puede ser usado para incrementar la fuerza de rotura de materiales porcelánicos, disminuyendo su espesor, ahorrando materias primas y energía en el proceso de producción.

O presente estudo teve como objetivo determinar a flexão estática e a massa específica aparente da madeira de Inga marginata em diferentes condições de umidade. Foram abatidos três indivíduos com, aproximadamente, seis anos de idade. Para a determinação das propriedades estudadas foram seguidas as recomendações da norma ASTM D143-94. Observou-se redução superior a 1,2 vezes do módulo de elasticidade, módulo de ruptura, tensão no limite proporcional e força máxima na flexão estática em função da saturação das fibras. De maneira geral, as amostras apresentaram valores de massa específica aparente menores e maior resistência mecânica conforme a dessorção até a umidade de equilíbrio de 12%, sendo a madeira, nessa condição, classificada como moderadamente pesada.

Foram avaliadas as propriedades físico-mecânicas da madeira de Hovenia dulcis Thumberg, proveniente de seis árvores e retiradas de três posições no fuste. A massa específica aparente média foi de 0,64 g cm-3 e a umidade de equilíbrio, após condicionamento a 20 oC e 65% de umidade relativa do ar, foi de 15,5%. Houve diferença das propriedades físicas da madeira entre árvores e posição no fuste. Os valores médios das propriedades mecânicas indicam enquadramento na classe C20 de classificação para madeiras de dicotiledôneas da Norma NBR 7190/97, exceto para módulo de elasticidade em compressão paralela.

ABSTRACT Growth in world demand for wood implies a search for new fast growing species with silvicultural potential, and in this scenario for native species such as Paricá . Thus, the objective of this study was determining the physical and mechanical wood properties of the Schizolobium amazonicum species (known as Paricá in Brazil). Trees were collected from commercial plantations located in the north of Brazil with ages of 5, 7, 9 and 11 years. Four logs from trees of each age in the longitudinal direction of the trees were obtained, and later a diametrical plank of each log was taken to manufacture the specimens which were used to evaluate some physical and mechanical properties of the wood. The basic density of Paricá was reduced in the basetop direction and no difference between the radial positions was observed, while the average basic density of this wood was characterized as low. The region close to the bark showed less longitudinal contraction and also greater homogeneity of this property along the trunk, while for tangential contraction the smallest variation was found in the region near the pith. Paricá wood contraction was characterized as low. Age influenced most of the mechanical properties, where logs from the base had the highest values of mechanical strength.