Geopolímeros de tipo binario basados en una puzolana natural y escoria siderúrgica de alto horno

This study describes the synthesis at ambient temperature (25±3 °C) of binary geopolymer systems based on natural volcanic pozzolan and granulated blast furnace slag. Na2SiO3 and NaOH were used as alkaline activators. The effects of the SiO2/Al2O3, Na2O/Al2O3 ratio and the amount of slag added (from 0 to 30%) on the reaction kinetics, compressive strength and microstructure of the final product were studied. To characterise the geopolymer pastes, techniques such as X-ray diffraction (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used. The results indicate the possibility of obtaining a geopolymer cement with a compressive strength of up to 48.11 MPa after 28 days of curing at ambient temperature whose characteristics are comparable to those of commercial portland cement.Este trabajo describe la síntesis a temperatura ambiente (25±3 °C) de sistemas geopoliméricos de tipo binario basados en una puzolana natural de origen volcánico y escoria siderúrgica de alto horno usando activadores alcalinos basados en la combinación de Na2SiO3 y NaOH. Se estudió el efecto de la relación SiO2/Al2O3, Na2O/Al2O3 y la cantidad de escoria adicionada en niveles entre el 0 y 30% sobre la cinética de reacción, la resistencia a la compresión y la microestructura del producto final. Para la caracterización de las pastas geopoliméricas se utilizaron técnicas como difracción de rayos X (DRX), espectroscopia infrarroja (FTIR) y microscopia electrónica de barrido (MEB). Los resultados conseguidos revelan la posibilidad de obtener un cementante geopolimérico con una resistencia a la compresión de hasta 48,11 MPa a los 28 días de curado a temperatura ambiente cuyas características son comparables a las de un cemento portland comercial

Ceniza de cascarilla de arroz como fuente de sílice en sistemas cementicios de ceniza volante y escoria activados alcalinamente

This study assesses the viability of using an agro-industrial by-product, rice husk ash (RHA) from a Colombian rice company’s combustion facility, as a total replacement for the commercial sodium silicate ordinarily used in alkaliactivated binders. Fly ash (FA), granulated blast furnace slag (GBFS) and binary 50FA:50GBFS blended pastes were activated with a mix of sodium hydroxide and either sodium silicate or one of two types of RHA. The pastes were characterised for strength, mineralogy and microstructure. The findings showed that the agro-industrial by-product can be used to yield alkali-activated materials with 7-day mechanical strengths on the order of 42 MPa. The study confirmed that both amorphous silica and part of the crystalline silica present in RHA participate in the alkaline activation process, providing the alkalinity is suitably adjusted.Este estudio evalúa la viabilidad de utilizar un subproducto agroindustrial, la ceniza de cascarilla de arroz (RHA) proveniente de un equipo combustor de una empresa Arrocera en Colombia, como reemplazo total de la sílice aportada por el silicato de sodio comercial en sistemas cementicios activados alcalinamente. Se prepararon pastas de ceniza volante (FA), de escoria de alto horno (GBFS) y un sistema binario 50FA:50GBFS, que fueron activadas por una mezcla de silicato de sodio e hidróxido de sodio, y por dos tipos de RHA. Las mezclas se caracterizaron mecánica, mineralógica y microestructuralmente. Los resultados demuestran que es posible obtener materiales activados alcalinamente con resistencias mecánicas del orden de 42 MPa, a 7 días de curado, utilizando el subproducto agroindustrial. Este estudio corrobora que tanto la sílice amorfa como parte de la sílice cristalina presente en RHA tienen la posibilidad de participar en el proceso de activación alcalina, siempre y cuando las condiciones de alcalinidad estén adecuadamente ajustadas

Nuevo material compuesto de matriz geopolimérica activado con ceniza de cascarilla de arroz y KOH: Desempeño a alta temperatura

Geopolymers were produced using an environmentally friendly alkali activator (based on Rice Husk Ash and potassium hydroxide). Aluminosilicates particles, carbon and ceramic fibres were used as reinforcement materials. The effects of reinforcement materials on the flexural strength, linear-shrinkage, thermophysical properties and microstructure of the geopolymers at room and high temperature (1200 ÅãC) were studied. The results indicated that the toughness of the composites is increased 110.4% for geopolymer reinforced by ceramic fibres (G-AF) at room temperature. The presence of particles improved the flexural behaviour 265% for geopolymer reinforced by carbon fibres and particles after exposure to 1200 .C. Linear-shrinkage for geopolymer reinforced by ceramic fibres and particles and the geopolymer G-AF compared with reference sample (without fibres and particles) is improved by 27.88% and 7.88% respectively at 900 ÅãC. The geopolymer materials developed in this work are porous materials with low thermal conductivity and good mechanical properties with potential thermal insulation applications for building applications.Compuestos geopoliméricos fueron producidos usando un activador alcalino alternativo (basado en ceniza de cascarilla de arroz e hidróxido de potasio), partículas aluminosilicatos, fibras de carbono y cerámicas. Se estudió el efecto de fibras y partículas en la resistencia a la flexión, contracción lineal, propiedades termofísicas y microestructura de los geopolímeros a temperatura ambiente y 1200 °C. Los resultados indican que la tenacidad se incrementó 110.4% para el geopolímero reforzado con fibras cerámicas (G-AF) a temperatura ambiente. La presencia de partículas mejora el comportamiento a la flexión 265% para el geopolímero reforzado con fibras de carbono y partículas después de la exposición a 1200 °C. La contracción lineal para el geopolímero reforzado con fibras cerámicas y partículas y el geopolímero G-AF es mejorada 27.88% y 7.88% respectivamente a 900 ºC con respecto al material sin refuerzo. Los materiales geopoliméricos desarrollados en este estudio son materiales porosos de baja conductividad térmica y buenas propiedades mecánicas con potencial aplicación en la industria de la construcción como aislantes térmicos

Durabilidad del hormigón armado expuesto a condiciones agresivas

Reinforced concrete is the most widely used construction material in the world. The combination of high compressive strength, afforded by concrete and, and the excellent mechanical properties that characterise steel make it an ideal composite for all manner of structures. One of the main weaknesses of this material, however, is that when the concrete is exposed to aggressive environments, in particular high concentrations of chloride ions or carbon dioxide, reinforcing steel corrodes, shortening service life. This article reviews the state of the art on concrete durability, along with the conditions that affect its useful life by inducing reinforcing steel corrosion. It also discusses the prevention and control methods, in particular electrochemical prevention and rehabilitation techniques, that have been developed to mitigate the problem.El hormigón armado se ha convertido en el material más utilizado a nivel mundial en el sector de la construcción. La combinación de las altas prestaciones a resistencia a la compresión que ofrece el hormigón y las excelentes propiedades mecánicas del acero lo hacen el material compuesto ideal para aplicaciones estructurales. Sin embargo, uno de los mayores problemas que afecta la vida útil del hormigón es la corrosión del acero de refuerzo, la cual se presenta cuando el hormigón se encuentra expuesto a ambientes agresivos, en especial frente a la exposición a iones cloruros y/o dióxido de carbono. Este trabajo revisa el estado del conocimiento con respecto a la durabilidad del hormigón enfatizando en los fenómenos que afectan su durabilidad y generan la corrosión del acero de refuerzo, adicionalmente se incluyen los métodos de prevención y control que se han desarrollado para mitigar el problema, en particular los relacionados con las técnicas electroquímicas de prevención y rehabilitación

Trends in Nanoparticles for Leishmania Treatment: A Bibliometric and Network Analysis

Leishmaniasis is a neglected tropical illness with a wide variety of clinical signs ranging from visceral to cutaneous symptoms, resulting in millions of new cases and thousands of fatalities reported annually. This article provides a bibliometric analysis of the main authors’ contributions, institutions, and nations in terms of productivity, citations, and bibliographic linkages to the appli- cation of nanoparticles (NPs) for the treatment of leishmania. The study is based on a sample of 524 Scopus documents from 1991 to 2022. Utilising the Bibliometrix R-Tool version 4.0 and VOSviewer software, version 1.6.17 the analysis was developed. We identified crucial subjects associated with the application of NPs in the field of antileishmanial development (NPs and drug formulation for leishmaniasis treatment, animal models, and experiments). We selected research topics that were out of date and oversaturated. Simultaneously, we proposed developing subjects based on multiple analyses of the corpus of published scientific literature (title, abstract, and keywords). Finally, the technique used contributed to the development of a broader and more specific “big picture” of nanomedicine research in antileishmanial studies for future projects

Carbonatación de un hormigón hibrido con alto contenido de escoria siderurgica de alto horno y su impacto en la corrosión del acero estructural

The aim of this research was to study the carbonation resistance of a blast furnace slag concrete (80% GBFS/20%OPC), with and without alkaline activation, and its influence on the corrosion of structural reinforcement. An OPC-based concrete produced under the same specifications was used as a reference material. To do this, the material was subjected to an accelerated carbonation process under controlled conditions (65% relative humidity, 1% CO2, 25°C). The half-cell potential (Ecorr), linear polarization resistance (LPR) tests showed that both concretes based on GBFS led to depassivation of the reinforcing steel at approximately 99 days, which is the time required for full carbonation of the evaluated concretes.El objetivo de esta investigación fue estudiar la resistencia a la carbonatación de un hormigón a base de escoria granulada de alto horno (80% GBFS/20%OPC), con y sin activación alcalina, y su influencia sobre la corrosión del acero estructural. Un hormigón basado en cemento portland producido con las mismas especificaciones fue usado como material de referencia. Para ello, el material fue sometido a un proceso de carbonatación acelerada bajo condiciones controladas (Humedad Relativa 65 %, 1% CO2, 25 °C). Los ensayos de potencial de media celda (Ecorr) y Resistencia a la polarización lineal (LPR) mostraron que los aceros estructurales aproximadamente a los 99 días alcanzan la despasivación en los hormigones basados en escoria, coincide este tiempo con el requerido para la completa carbonatación de los hormigones evaluados

Antimicrobial-producing Pseudoalteromonas from the marine environment of Panama shows a high phylogenetic diversity and clonal structure

Pseudoalteromonas is a genus of marine bacteria often found in association with other organisms. Although several studies have examined Pseudoalteromonas diversity and their antimicrobial activity, its diversity in tropical environments is largely unexplored. We investigated the diversity of Pseudoalteromonasin marine environments of Panama using a multilocus phylogenetic approach. Furthermore we tested their antimicrobial capacity and evaluated the effect of recombination and mutation in shaping their phylogenetic relationships. The reconstruction of clonal relationships among 78 strains including 15 reference Pseudoalteromonas species revealed 43 clonal lineages, divided in pigmented and non-pigmented strains. In total, 39 strains displayed moderate to high activity against Gram-positive and Gram-negative bacteria and fungi. Linkage disequilibrium analyses showed that the Pseudoalteromonas strains of Panama have a highly clonal structure and that, although present, recombination is not frequent enough to break the association among alleles. This clonal structure is in contrast to the high rates of recombination generally reported for aquatic and marine bacteria.We propose that this structure is likely due to the symbiotic association with marine invertebrates of most strains analyzed. Our results also show that there are several putative new species of Pseudoalteromonas in Panama to be described.Pseudoalteromonas is a genus of marine bacteria often found in association with other organisms. Although several studies have examined Pseudoalteromonas diversity and their antimicrobial activity, its diversity in tropical environments is largely unexplored. We investigated the diversity of Pseudoalteromonasin marine environments of Panama using a multilocus phylogenetic approach. Furthermore we tested their antimicrobial capacity and evaluated the effect of recombination and mutation in shaping their phylogenetic relationships. The reconstruction of clonal relationships among 78 strains including 15 reference Pseudoalteromonas species revealed 43 clonal lineages, divided in pigmented and non-pigmented strains. In total, 39 strains displayed moderate to high activity against Gram-positive and Gram-negative bacteria and fungi. Linkage disequilibrium analyses showed that the Pseudoalteromonas strains of Panama have a highly clonal structure and that, although present, recombination is not frequent enough to break the association among alleles. This clonal structure is in contrast to the high rates of recombination generally reported for aquatic and marine bacteria.We propose that this structure is likely due to the symbiotic association with marine invertebrates of most strains analyzed. Our results also show that there are several putative new species of Pseudoalteromonas in Panama to be described

Comparación de la percepción social en playas recreativas arenosas de dos bahías localizadas en el Pacífico Mexicano

En el presente trabajo se desarrollaron dos formatos de encuesta, para incorporar la percepción de los usuarios a la evaluación de la calidad de las playas (Cervantes, 2006 y Silva-Iñiguez, 2006); ambos basados en un modelo cuantitativo para revelar la percepción social de las playas localizadas en la bahía de Santiago, Manzanillo, Col (MZO) y en Acapulco, Gro (ACA). Se aplicaron un total de 790 encuestas (ACA: 390 y MZO: 400), que permitieron conocer el perfil de los usuarios, sus hábitos de recreación y sus opiniones sobre las condiciones biofísicas y de infraestructura de cada playa. En ambas playas la mayoría prefirieron asistir acompañados por sus familias; las principales actividades recreativas fueron nadar, descansar, comer y beber. En general las demandas en ambos sitios coincidieron con incrementar el número de botes de basura, la frecuencia en el servicio de recolección y limpieza, baños y regaderas. Las razones por la que los usuarios seleccionaron la playa a visitar fueron la seguridad y vigilancia, así como las características biofísicas de la misma. La incorporación de esta información a modelos y/o esquemas de evaluación y gestión de playa (a través de índices ambientales) permitió realizar la valoración integral de la playa.In this paper it was developed two survey formats, to include the perception of users on the assessment of the quality of the beaches (Cervantes, 2006 and Silva-Iñiguez, 2006), both based on a quantitative model to reveal the social perception of the beaches on Santiago Bay, Manzanillo, Col (MZO) and Acapulco, Guerrero (ACA). We did a total of 790 surveys (ACA: 390 and MZO: 400), which allowed the user profile, recreation habits and their views on the biophysical and infrastructure of each beach. In both beaches, most people, attended with their families, the main recreational activities were swimming, resting, eating and drinking. In general the demands on both sites agreed to increase the number of waste baskets, the frequency of collection service and cleaning bathrooms and showers. The reasons why the users selected to visit the beach were the safety and security, as well as the biophysical characteristics of the same. Incorporating this information to models and / or evaluation schemes and beach management (through environmental ratings) allowed the comprehensive assessment of the beach