Evaluación de las propiedades mecánicas de concretos modificados con microesferas de vidrio y residuos de llantas

The combined effect of recycled tires and microspheres as substitutes of raw material to produce modified concrete as of raw materials used in the manufacture of traditional concrete was explored in this work. Traditional and mix concrete were designed and modified concrete mixes with 15% by mass of fine aggregate were replaced in a 0:1, 1:1, 1:3, 3:1 and 1:0 were designed and prepared. With the prepared concrete mixes cylindrical specimens of 5mmx300mm in diameter were made. The evaluation of mechanical and physical properties of the cylindrical specimens showed that the materials with the highest content of tire residues exhibited the lower density, while those with higher microsphere content have a higher compressive strength; in fact, this is similar to the traditional concrete. As a result, the concrete mix design with glass microspheres and the mix design in 1:3 ratios showed greater mechanical properties then the other mixtures with compressive strengths of 22.4 and 19.1 MPa respectively. The results demonstrate that the combinations of microspheres and tire residues have a synergistic effect with a potential use in the construction industry as a replacement of traditional materials in the manufacture of concrete. In particular, it is expected that the use of these materials in the production of concrete, will become an alternative for the use of these wastes, which do not currently have a disposal plan.El efecto combinado de residuos de llantas y microesferas como sustitutos de la materia prima utilizada en la elaboración convencional de concretos fue explorada en este trabajo. Se diseñaron y prepararon mezclas de concreto tradicional, con modificaciones del 15% en masa de los agregados finos con relaciones de residuos de llantas, microesferas de vidrio de 0:1, 1:1, 1:3, 3:1 y 1:0. A partir de las mezclas preparadas se elaboraron especímenes cilíndricos de 150 mm x 300 mm. La evaluación de las propiedades mecánicas y físicas de los especímenes cilíndricos mostró que los materiales con mayor contenido de residuos de llantas presentaron una menor densidad, mientras que los de mayor contenido de microesferas presentaron la mayor resistencia a la compresión; de hecho, las mezclas 0:1 y 1:3 presentaron resistencias a la compresión de 22.4 y 19.1 MPa, respectivamente. Los resultados encontrados muestran que la adición conjunta de microesferas y residuos de llantas presentan un efecto sinérgico combinado entre los dos materiales con potencial uso en la industria de la construcción, en reemplazo de los materiales tradicionales utilizados en la elaboración de concretos, en particular, se espera que el uso de estos materiales se convierta en una alternativa para la utilización de estos residuos, los cuales no cuentan actualmente con un plan de disposición

Production of acetins (fuel additives) from glycerol

La elevada producción de glicerol, un subproducto de bajo costo proveniente de la industria del biodiésel, ha supuesto una amenaza tanto para el medio ambiente como para la economía. La transformación de glicerol en productos de valor agregado contribuiría positivamente a la economía del biodiésel. En este artículo de revisión se describen las rutas de valorización del glicerol y se presenta la esterificación como una de las más prometedoras para la transformación de glicerol en aditivos para combustibles; igualmente, se describen los resultados más relevantes entre 2010 y 2020 relacionados con las condiciones experimentales (temperatura, relación molar y tiempo de reacción), los catalizadores heterogéneos y la actividad catalítica (en términos de la conversión del glicerol y la selectividad) para la transformación de glicerol en acetinas (monoacetina, diacetina y triacetina). Se espera que esta revisión permita abordar esta técnica de valorización de manera rentable y ambientalmente sostenible.The high production of glycerol, a low-cost by-product, from the biodiesel industry, has posed a threat to both the environment and the economy. The transformation of glycerol into value-added products would contribute positively to the biodiesel economy. In this review article, the valorization routes of glycerol are described; esterification is presented as one of the most promising routes for the transformation of glycerol in additive fuels. This review describes the most relevant results between 2010 and 2020 related to experimental conditions (temperature, molar ratio, and reaction time), heterogeneous catalysts, and catalytic activity (in terms of glycerol conversion and acetins selectivity) for the transformation of glycerol into acetins. (monoacetin, diacetin and triacetin). It is hoped that this review will allow this valuation technique to be addressed in a profitable and environmentally sustainable manner

Introducción a la tecnología de membranas para la purificación de biogas y algunos desarrollos recientes

The remotion of CO2 from CO2/CH4 mixes to increasing energy content in natural gas or biogas and to prevent corrosion problems, has driven the development of CO2 separation process through membranes.  The attractive features offered by this technology include high energy efficiency, reduced cost and highly flexible performance. This review provides an overview of the reported paper from 2010 to 2020 different types of membranes available: polymeric, inorganic and mixed matrix for CO2/CH4 separation process, experimental conditions and primary determinants of separation performance and efficiency (permeability of CO2 and CO2/CH4 selectivity).  This work would open up a new perspective of each membrane to facilitate a better appreciation of their role in the improvement of overall process performance.La remoción de CO2 en mezclas de CO2/CH4 para aumentar el contenido de energía en gas natural o biogás y prevenir problemas de corrosión, ha impulsado el desarrollo del proceso de separación de CO2 utilizando membranas.  Las características más relevantes que ofrece la tecnología basada en membranas incluyen la alta eficiencia energética, el costo reducido y el rendimiento altamente flexible. Esta revisión  proporciona una descripción de los trabajos reportados desde 2010 hasta 2020 sobre los diferentes tipos de membranas disponibles: poliméricas, inorgánicas y de matriz mixta para el proceso de separación de CO2/CH4;  se reportan las condiciones experimentales y los determinantes primarios del rendimiento y la eficiencia de la separación (permeabilidad de CO2 y selectividad CO2/CH4).  Este trabajo ofrece una nueva perspectiva de cada membrana para facilitar una mejor apreciación de su papel en la mejora del rendimiento general del proceso   The remotion of CO2 from CO2/CH4 mixes to increasing energy content in natural gas or biogas and to prevent corrosion problems, has driven the development of CO2 separation process through membranes.  The attractive features offered by this technology include high energy efficiency, reduced cost and highly flexible performance. This review provides an overview of the reported paper from 2010 to 2020 different types of membranes available: polymeric, inorganic and mixed matrix for CO2/CH4 separation process, experimental conditions and primary determinants of separation performance and efficiency (permeability of CO2 and CO2/CH4 selectivity).  This work would open up a new perspective of each membrane to facilitate a better appreciation of their role in the improvement of overall process performance

Ceniza de cáscara de coco como susituto del cemento: efecto de la temperatura de calcinación

 The disposal of coconut shell is a waste problem in countries where coconut production is in abundance. When coconut shell is calcinated produces ashes, which are a potential binder material to concrete preparation. In this work, coconut shell was calcinated at 400, 500 and 600 °C for 3 h. The ashes produced were employed as cement substitute. The characteristics of ashes were evaluated by surface area and XRD. The effect of replacing ashes as cement substitute was evaluated by workability and mechanical strength test. Experimental results demonstrated that 600 °C is the most suitable burning temperature for CSA calcination with amorphous SiO2 and low surface area. Results showed that, in contrast to control concrete, that burning temperature decrease concrete workability of concrete. Further, the increasing of burning temperature of coconut shell improves the mechanical strength. The compressive strength of mixture incorporating the ashes of coconut shell burned at 600 °C was higher than the others. Additionally, this temperature was found convincing considering cost to prepare the ashes.La disposición de la cáscara de coco es un problema de eliminación de desechos en países donde la producción de coco es abundante. Cuando la cáscara de coco se calcina produce cenizas, las cuales son un material aglutinante potencial para preparar hormigón. En este trabajo se calcinó cáscara de coco a 400°C, 500°C y 600 °C durante 3 h. Las cenizas producidas se emplearon como sustituto del cemento. Las características de las cenizas se evaluaron por área superficial y DRX. El efecto de la sustitución de las cenizas como sustituto del cemento se evaluó mediante ensayos de trabajabilidad y resistencia mecánica. Los resultados experimentales demostraron que 600 °C es la temperatura de combustión más adecuada para la calcinación de la cascara, con presencia de SiO2 amorfo y baja superficial alta. Los resultados mostraron que, en contraste con el hormigón de referencia, la temperatura de combustión disminuye la trabajabilidad del concreto. Además, el aumento de la temperatura de calcinación de la cáscara de coco mejora la resistencia mecánica. La resistencia a compresión de la mezcla que incorporó cenizas de cáscara de coco calcinadas a 600 °C fue superior a las demás. Se encontró adicionalmente que esta temperatura era convincente considerando el costo de preparar las cenizas. &nbsp

Propiedades mecánicas y térmicas de hormigones modificados con residuos plásticos triturados y pelletizados

El carácter no biodegradable de los residuos plásticos tiene un efecto negativo sobre el medio ambiente. La valorización del plástico en la producción de hormigón con menor conductividad térmica puede contribuir a la disminución de la energía consumida para mantener el confort térmico al interior de los edificios. El presente estudio reporta la preparación de mezclas y cilindros de hormigón con residuos plásticos triturados y pelletizados como reemplazo (1.7%, 3.4% y 5%) de los agregados finos. Se evaluó la densidad, la resistencia a compresión   y la conductividad térmica. Los resultados evidenciaron una disminución en la densidad y la conductividad térmica con el aumento del contenido de desechos plásticos triturados y pelletizados. Asimismo, los residuos plásticos triturados tienen un efecto negativo al disminuir la resistencia. El hormigón con 3,4% de residuos plásticos pelletizados presenta la mayor resistencia. La adición de plásticos pelletizados mejora las propiedades mecánicas y térmicas del hormigón modificado.The non-biodegradable character of plastic wastes has a negative effect on the environment. The valorization of plastic in the production of concrete with lower thermal conductivity may contribute to decreasing the energy consumed to maintain indoor thermal comfort in buildings. The present study reports the preparation of mixes and cylindrical specimens of concrete with shredded and pelletized plastic wastes as replacements (1.7%, 3.4%, and 5%) for fine aggregates. Density, compressive strength, and thermal conductivity were measured. The experimental results demonstrated a decrease in density and thermal conductivity with increasing quantity of shredded and pelletized plastic wastes. Additionally, shredded plastic wastes have a negative effect by decreasing compressive strength. Concrete with 3.4% pelletized plastic presents the highest compressive strength. The incorporation of pelletized plastic improves the mechanical and thermal properties of modified concrete

Propiedades mecánicas de concretos modificados con plástico marino reciclado en reemplazo de los agregados finos

Plastic waste and its low recycling rate contribute to environmental pollution, requiring valorization strategies This work presents the design and preparation of traditional and mix concrete with replacement of  2.5%, 5.0%, 7.5% and 10% of fine aggregates by recycled plastic of the ocean. With the prepared concrete mixes, cylindrical specimens of 15cmx30mm in diameterxheight, respectively, were made. Slump, density, compressive strength, and elasticity modulus were evaluated. The results exhibited that an increase in the content of recycled plastic generates a decrease in slump and density, as well as an increase in strength and elastic modulus. Specimens with 7.5% exhibited the highest strength (18.9 MPa) equivalent to 91% of the traditional one (20 MPa). The results gathered would form a part of useful information for recycling plastic waste in the preparation of concrete that requiring moderate strength.Los desechos plásticos marinos y su baja tasa de reutilización contribuyen a la contaminación ambiental, requiriéndose estrategias de valorización. Este trabajo presenta el diseño y la preparación de mezclas de concreto tradicional y con reemplazos del 2.5%, 5%, 7.5% y 10% de los agregados finos por plásticos reciclados del mar. A partir de las mezclas preparadas se elaboraron especímenes cilíndricos de 15cmx30cm de diámetroxaltura, respectivamente. Se evaluó el asentamiento, la densidad, la resistencia y el modulo elástico. Los resultados mostraron que un aumento del contenido de plástico reciclado genera una disminución del asentamiento y la densidad, así como un aumento de la resistencia y del módulo elástico. Los especímenes con sustituciones del 7.5% presentaron la mejor resistencia a compresión (18.19 MPa) equivalente al 90.5% del tradicional (20 MPa). Los resultados encontrados muestran información valiosa para la valorización de desechos plásticos marinos en la elaboración de concretos con resistencias moderadas.Los desechos plásticos marinos y su baja tasa de reutilización contribuyen a la contaminación ambiental, requiriéndose estrategias de valorización. Este trabajo presenta el diseño y la preparación de mezclas de concreto tradicional y con reemplazos del 2.5%, 5%, 7.5% y 10% de los agregados finos por plásticos reciclados del mar. A partir de las mezclas preparadas se elaboraron especímenes cilíndricos de 15cmx30cm de diámetroxaltura, respectivamente. Se evaluó el asentamiento, la densidad, la resistencia y el modulo elástico. Los resultados mostraron que un aumento del contenido de plástico reciclado genera una disminución del asentamiento y la densidad, así como un aumento de la resistencia y del módulo elástico. Los especímenes con sustituciones del 7.5% presentaron la mejor resistencia a compresión (18.19 MPa) equivalente al 90.5% del tradicional (20 MPa). Los resultados encontrados muestran información valiosa para la valorización de desechos plásticos marinos en la elaboración de concretos con resistencias moderadas.Plastic waste and its low recycling rate contribute to environmental pollution, requiring valorization strategies This work presents the design and preparation of traditional and mix concrete with replacement of  2.5%, 5.0%, 7.5% and 10% of fine aggregates by recycled plastic of the ocean. With the prepared concrete mixes, cylindrical specimens of 15cmx30mm in diameterxheight, respectively, were made. Slump, density, compressive strength, and elasticity modulus were evaluated. The results exhibited that an increase in the content of recycled plastic generates a decrease in slump and density, as well as an increase in strength and elastic modulus. Specimens with 7.5% exhibited the highest strength (18.9 MPa) equivalent to 91% of the traditional one (20 MPa). The results gathered would form a part of useful information for recycling plastic waste in the preparation of concrete that requiring moderate strength.

Measurement of the W gamma Production Cross Section in Proton-Proton Collisions at root s=13 TeV and Constraints on Effective Field Theory Coefficients

A fiducial cross section for W gamma production in proton-proton collisions is measured at a center-of-mass energy of 13 TeV in 137 fb(-1) of data collected using the CMS detector at the LHC. The W -> e nu and mu nu decay modes are used in a maximum-likelihood fit to the lepton-photon invariant mass distribution to extract the combined cross section. The measured cross section is compared with theoretical expectations at next-to-leading order in quantum chromodynamics. In addition, 95% confidence level intervals are reported for anomalous triple-gauge couplings within the framework of effective field theory.Peer reviewe

Search for long-lived particles decaying to jets with displaced vertices in proton-proton collisions at root s=13 Te V

A search is presented for long-lived particles produced in pairs in proton-proton collisions at the LHC operating at a center-of-mass energy of 13 TeV. The data were collected with the CMS detector during the period from 2015 through 2018, and correspond to a total integrated luminosity of 140 fb(-1). This search targets pairs of long-lived particles with mean proper decay lengths between 0.1 and 100 mm, each of which decays into at least two quarks that hadronize to jets, resulting in a final state with two displaced vertices. No significant excess of events with two displaced vertices is observed. In the context of R-parity violating supersymmetry models, the pair production of long-lived neutralinos, gluinos, and top squarks is excluded at 95% confidence level for cross sections larger than 0.08 fb, masses between 800 and 3000 GeV, and mean proper decay lengths between 1 and 25 mm.Peer reviewe

Search for top squark production in fully hadronic final states in proton-proton collisions at root s=13 TeV

A search for production of the supersymmetric partners of the top quark, top squarks, is presented. The search is based on proton-proton collision events containing multiple jets, no leptons, and large transverse momentum imbalance. The data were collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV, and correspond to an integrated luminosity of 137 fb(-1). The targeted signal production scenarios are direct and gluino-mediated top squark production, including scenarios in which the top squark and neutralino masses are nearly degenerate. The search utilizes novel algorithms based on deep neural networks that identify hadronically decaying top quarks and W bosons, which are expected in many of the targeted signal models. No statistically significant excess of events is observed relative to the expectation from the standard model, and limits on the top squark production cross section are obtained in the context of simplified supersymmetric models for various production and decay modes. Exclusion limits as high as 1310 GeVare established at the 95% confidence level on the mass of the top squark for direct top squark production models, and as high as 2260 GeV on the mass of the gluino for gluino-mediated top squark production models. These results represent a significant improvement over the results of previous searches for supersymmetry by CMS in the same final state.Peer reviewe

Search for a heavy resonance decaying to a top quark and a w boson at √s = 13 tev in the fully hadronic final state

A search for a heavy resonance decaying to a top quark and a W boson in the fully hadronic final state is presented. The analysis is performed using data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb−1 recorded by the CMS experiment at the LHC. The search is focused on heavy resonances, where the decay products of each top quark or W boson are expected to be reconstructed as a single, large-radius jet with a distinct substructure. The production of an excited bottom quark, b*, is used as a benchmark when setting limits on the cross section for a heavy resonance decaying to a top quark and a W boson. The hypotheses of b* quarks with left-handed, right-handed, and vector-like chiralities are excluded at 95% confidence level for masses below 2.6, 2.8, and 3.1 TeV, respectively. These are the most stringent limits on the b* quark mass to date, extending the previous best limits by almost a factor of two