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

Recycling of eps foam and demolition wastes in the preparation of ecofriendly render mortars with thermal-acoustic insulation properties

The design of render-mortars from construction and demolition waste (CDW) was evaluated. Fine aggregates from red-clay-brick waste, mortar and concrete waste were used, together with recycled expanded-polystyrene (EPS) as lightweight filler. Mixes composed of 70%-recycled aggregates, and 30% consisting of a matrix of Portland cement were produced. Characterization tests were conducted on the physical, mechanical, thermal, and acoustic properties. The render-mortar A4, A7 and A9 can be classified according to compressive strength results as CSI-W0 for interior use under standard UNE-EN-998-1. The A7 mortar, with the best physical and mechanical results, contained 21% EPS, 17.5% brick waste and 17.5% mortar waste. Mix A4 obtained the lowest thermal conductivity, 0.12 W/m·K - a reduction of 79% compared to the commercial-mortar AC1. The acoustic absorption properties were also enhanced by the incorporation of EPS, such that the A4, A7, and A9 mixes were identified as Absorbent for the frequencies of 2000 Hz and 4000 Hz

Materiales vitrocerámicos obtenidos a partir de residuos sólidos tales como cenizas, escorias y vidrio: revisión

El uso de residuos y subproductos industriales como reemplazo parcial o total de materias primas vírgenes para la producción de materiales se ha convertido en una parte vital de la gestión de desechos, lo cual ha dado lugar a tecnologías innovadoras que permiten extender su aplicación al desarrollo de nuevos productos, contribuyendo así a la menor contaminación ambiental y a los conceptos de la economía circular. En los últimos años, la tecnología de vitrificación de residuos se ha considerado un procedimiento atractivo para el tratamiento de diferentes tipos y mezclas de residuos para la obtención de vidrios y vitrocerámicas. El presente artículo hace una revisión de las investigaciones relacionadas con la producción de vitrocerámicas densas realizadas entre 1994 y 2019, específicamente las que han utilizado cenizas, escorias y residuos de vidrio. La revisión revela que se han acumulado considerables conocimientos y experiencia en el proceso de transformación de los desechos base silicatos en productos útiles de vidrio y vitrocerámicas con propiedades similares e incluso superiores a los de materiales convencionales, abriendo nuevos campos de aplicación en ceramicas avanzadas

Production of low-silica zeolites from colombian kaolin

En este artículo se presenta un estudio de la producción de zeolita sintética A de baja sílice por medio de la síntesis hidrotermal a partir de un caolín colombiano. La técnica Metodología de Superficie de Respuesta se emplea con el fin de encontrar las condiciones óptimas de proceso (como las relaciones molares Na2O/SiO2 y H2O/Al2O3, tiempo y temperatura) que garanticen la calidad de las zeolitas obtenidas. El grado de cristalinidad y la capacidad de intercambio catiónico, se usaron como variables de respuesta. La capacidad de intercambio catiónico se determinó a partir de la Norma NTC 5167. La composición mineralógica y la microestructura de las zeolitas producidas se caracterizaron a través de técnicas como microscopía electrónica de barrido, difracción de rayos X y resonancia magnética nuclear. Los resultados indican que sí es posible la obtención de zeolitas sintéticas a partir del caolín colombiano evaluado. Zeolita tipo A con capacidad de intercambio catiónico 442 cmol/Kg (valor mayor al obtenido con una zeolita comercial importada empleada en la industria colombiana, 408 cmol/Kg) se obtuvo bajo las siguientes condiciones óptimas de procesamiento: relaciones molares Na2O/SiO2 de 2.7, H2O/Al2O3 de 150, temperatura de 66 °C y tiempo de procesamiento de 8 horasThis paper presents a study of the production of a synthetic zeolite of low-silica content by hydrothermal synthesis from Colombian kaolin. The statistical technique Response-Surface Methodology was used to find the optimum process conditions (i.e., molar ratios Na2O/SiO2 and H2O/Al2O3, time and temperature) and to ensure the quality of the zeolites obtained. The cation exchange capacity and the degree of crystallinity were used as response variables. The cation exchange capacity was determined following Standard NTC 5167. The mineralogical composition and microstructure of the zeolites produced were characterized through the application of scanning electron microscopy, X-ray diffraction and nuclear magnetic resonance. The results indicate that it is possible to obtain a good quality synthetic zeolite from the Colombian kaolin evaluated. A zeolite type A with a cation exchange capacity of 442 cmol/Kg, a value higher than that exhibited by the same type of zeolite imported for applications in the Colombian industry (i.e., 408 cmol/Kg), was obtained with the following processing conditions: molar ratios Na2O/SiO2 of 2.7, H2O/Al2O3 of 150, at temperature 66 °C and processing time of 8 hours; yielde

Management and valorisation of wastes through use in producing alkali-activated cement materials

There is a growing global interest in maximising the re-use and recycling of waste, to minimise the environmental impacts associated with waste treatment and disposal. Use of high-volume wastes in the production of blended or novel cements (including alkali-activated cements) is well known as a key pathway by which these wastes can be re-used. This paper presents a critical overview of the urban, agricultural, mining and industrial wastes that have been identified as potential precursors for the production of alkali-activated cement materials, or that can be effectively stabilised/solidified via alkali activation, to assure their safe disposal. The central aim of this review is to elucidate the potential advantages and pitfalls associated with the application of alkali-activation technology to a wide variety of wastes that have been claimed to be suitable for the production of construction materials. A brief overview of the generation and characteristics of each waste is reported, accompanied by identification of opportunities for the use of alkali-activation technology for their valorisation and/or management

Synthesis of ternary geopolymers based on metakaolin, boiler slag and rice husk ash

Ternary mixtures of geopolymers obtained from the alkaline activation of metakaolin (MK), boiler slag (BS), and rice husk ash (RHA) using a solution of potassium hydroxide were mechanically, thermally, and microstructurally characterized. The geopolymer properties and final microstructures indicate that the addition of BS, despite containing large amounts of unburned material (16.36%), allows for greater densification and greater homogeneity of the geopolymeric gel, which results in greater stability in strength at long curing ages. Substitution of 30% of MK by BS results in an increase in compressive strength of up to 21% and 122% after 28 and 180 days of curing, respectively. These results demonstrate the possibility of the construction sector using geopolymers based on MK and adding BS and RHA to obtain cementitious materials with a lower environmental impact

Synthesis of ternary geopolymers based on metakaolin, boiler slag and rice husk ash

Mezclas ternarias de geopolímeros fueron obtenidas a partir de la activación alcalina de metacaolín (MK), ceniza de parrilla (BS) usando como activador alcalino una mezcla de hidróxido de potasio con ceniza de cascarilla de arroz (RHA). Los materiales producidos fueron caracterizados mecánica, térmica y microestructuralmente. Las propiedades de los geopolímeros y microestructura final indica que la adición de la escoria de parrilla (con grandes cantidades de material sin quemar, 16.36%), permite un mayor grado densificación y una mayor homogeneidad del geopolímero, resultando en una mayor estabilidad de la resistencia para largas edades. La sustitución del 30% del MK por BS genera un incremento de la resistencia a compresión hasta del 21% y 122% después de 28 y 180 días de curado respectivamente. Los resultados aquí obtenidos demuestran la posibilidad de usar geopolímeros basados en MK son adición de BS y RHA en el sector de la construcción para obtener materiales cementicios con bajo impacto ambiental

Ecological light transmiting concrete made from glass waste and acrylic sheets

In this research, recycling of 100% glass waste was evaluated for the manufacture of self-compacting mortars for applications in translucent building systems. The glass waste (WG) was ground and used as a fine aggregate in mortar mixtures with cement:WG proportion of 1:1.5, 1:1,75 and 1:2.0 with different water/cement (W/C) ratios. Properties such as fluidity, compressive strength, density, porosity, absorption, thermal properties, and characterization of the microstructure by SEM were analyzed. The results showed that as the WG content increases from 1:1.5 to 1:2.0 the compressive strength of the mortar decreases a maximum of 2.8% in samples with W/C:0.47, and this is due to the formation of microcracks and porosities, which cause the formation of a weakened and sparse interfacial zone which could be identified in the SEM tests. Nevertheless, the compressive strengths were between 20.6 MPa − 32.07 MPa, water absorption for mortars was between 12,92–14,74% and porosities from 23.02% to 25.93%. The thermal conductivity of the mortars was between 0.64 and 0.71 W/m.K. Additionally, the results of the spectrophotometry test for light transmission and the simulation in MATLAB allowed to obtain the brightness in the samples, it was possible to observe that the brightness varies according to the shape of the openings of the blocks, being the A design which allowed a greater passage of light (16%), and the materials developed could be classified as green building materials