The ingress of chlorides in concrete under compressive or tensile loads

One common aggressive mechanism acting in reinforced concrete is chloride attack which induces steel corrosion. Although it has mostly been studied and analyzed separately it has been observed that loads acting on concrete may modify the deteriorating effect. In this research the effect that combined attack provokes on concretes made of ordinary Portland cement (OPC), high sulfate-resistance cement (SR) and blast furnace slag (BFS) cement is investigated. Five mixes were made with these materials, 2 of them using a type 52.5 N (OPC) cement, 2 replacing OPC by 50 and 70 % of BFS and 1 made of 52.5 N (SR) cement type. Cubic samples made with all binder types were exposed to a 3% by weight sodium chloride solution while applying a permanent splitting tensile load corresponding to 50 % of their breaking capacity. Prismatic samples (100 x 100 x 400 mm) made of OPC binder were exposed to a 3% by weight sodium chloride solution while maintaining a compressive load equal to 30 % of their maximum capacity. After the exposure time, ground layers were obtained from the samples to determine the chloride ingress into the concrete by means of potentiometric titration. To define chloride transport in concrete an error function solution was applied to Fick’s second law. In terms of their diffusion coefficient and chloride surface concentration in decreasing order of performance were found: the concrete with 70 % replacement by BFS, followed by the concrete with 50 % BFS substitution, then pure OPC concrete and finally the sulfate resistant cement concrete. Load levels of 30 % in compression and 50 % in splitting tensile testing, improved the resistance of concrete to chloride attack

On the quantitative thermogravimetric analysis of calcite content in hydrated cementitious systems

Calcite is a compound that is present in hydrated cementitious materials when carbonation of portlandite occurs or when limestone constituents are used. The quantification of its content in cementitious systems is then frequently necessary. Thermogravimetry (TG) measures the change in mass of a material (as a function of time) over a temperature range using a predetermined heating rate. It can be applied to estimate calcite content in the hydrated cement system, considering the temperature range at which it decomposes and releases carbon dioxide. However, the quantification is not easy because the onset of this decomposition is a function of many variables. The tangential method over the TG signal or the integration method over the derivative TG curve (DTG) are usually used to discount the background over the temperature range at which calcite decomposes. However, consistent underestimation of compounds is frequently described. The reasons for this are unclear and some hypothesis are discussed in this paper. Additionally, experimental quantitative TG of cement paste and aggregate containing calcite and diluted with low contents of analytical calcite are compared with the expected contents, as a calibration method regarding calcite content in the samples is given to improve the reliability of the results

Chloride penetration in concrete under compression or splitting tensile load representing 60-65 per cent of the ultimate load

A critical loading ratio is reached at 50% of concrete ultimate load. Beyond this point the presence of micro cracks exerts a big influence on the chloride transport. For compression the strain distribution in the sample developed micro-cracking system that is more or less homogeneously distributed in the sample. Therefore it is expected the same chloride profile regardless of the position. When combined splitting tensile load and chloride attack are acting on concrete, the main micro-crack system is located on the loading plane. This contributes to regular and alike shaped chloride profiles if they are taken from planes that are kept parallel to the splitting one. Prismatic samples (100 x 100 x 400 mm) made of OPC binder were exposed to a 3% by weight sodium chloride solution while maintaining a loading ratio equal to 60 % of the maximum capacity. Cubic samples (side = 150 mm) made of OPC and 50% BFS had similar chemical exposure while applying a permanent splitting tensile load corresponding to 65 % of their breaking capacity. After the exposure, ground layers were obtained from the samples to determine the total chloride ingress into the concrete by means of potentiometric titration and the effect of the load on the chloride ingress was assessed

Situación actual de la mediana mineria en el Ecuador. cambio de sistema de producción en la mina bonanza

DETALLA TRABAJO REALIZADO EN LA COMPAÑIA EXPOBONANZA S.A. Y EL PROBLEMA QUE SE PLANTEA ES LA PUESTA EN FUNCIONAMIENTO DE UN NUEVO SISTEMA DE PROCESAMINETO DEL MATERIAL QUE SALE DE LA MINA, EN VISTA DE QUE LA CAPACIDAD DEL MOLINO SE VE AMPLIAMENTE SUPERADA Y SE TIENE QUE ALQUILAR OTROS MOLINOS Y ES LO QUE ELEVA SUSTANCIALMENTE LOS COSTOS.Y PARA ELLO SE HA TRATADO DE LLEVAR UN DISEÑO DE INVESTIGACION DONDE SE TRATA DE ANALIZAR Y DEMOSTRAR QUE EL PROBLEMA ES FACTIBLE Y QUE ESTARIA LIMITADO SOLAMENTE POR RESTRICCIONES EN LA INVERSION Y LA BUSQUEDA DEL EQUIPO PESADO. SUS VENTAJAS SERIAN TENER CAPACIDAD DE PROCESAR MATERIAL DE MANERA CONTINUA , LA PRODUCCION SE DETENDRIA UNICAMENTE CUANDO TOQUE L

Evaluación del Comportamiento en Compresión de Morteros Reforzados con Óxido de Grafeno y Costos Inherentes al Proceso Productivo de Mezcla

Se propone evaluar la obtención de óxido de grafeno a partir de: esquistos grafíticos procedentes del cerro Villonaco en la provincia de Loja–Ecuador, y de grafito sintético comercializado en Ecuador para reforzar químicamente morteros de cemento. Comparativamente se estudian mezclas de mortero reforzadas con óxido de grafeno reducido. El grafito natural es producto de la recristalización metamórfica de materia orgánica contenida en las rocas, cuando este proceso se produce sobre capas de carbón o sobre rocas que contienen hidrocarburos líquidos generando yacimientos. Las muestras de esquistos grafíticos son procesadas mecánica y químicamente separando las partículas de carbono de otros minerales o impurezas inorgánicas (sílice, alúmina, óxido férrico, otros) determinando el porcentaje de impurezas mediante un proceso de calcinación. Se ensayan 26 probetas cúbicas de mortero reforzadas con incrementos equidistantes entre 0,03-0,06% del peso de cemento en el mortero (ASTM-C-109), obteniendo una tendencia incremental de la resistencia mecánica a compresión

Tamaño máximo del agregado y su influencia en la porosidad de un hormigón elaborado con fibra de vidrio

Due to the importance of the granulometry, within the area of knowledge in the field of construction, the same that allows us to study and know the size of the aggregates at the moment of making a mixture, as is the case of coarse aggregate, within the study of the porosity the concrete.This investigation has as main objective, to evaluate the maximum size of the aggregate and it’s influence on the porosity of a concrete, made with glass fiber as a substitute for this; through Goran Fagerlund's methodology. For the evaluation of porosity in a conventional concrete with glass fiber, were carried out on the basis of a design by the ACI method and with a resistance of 21MPa. The samples used of the coarse aggregates came from the quarry COPETO.C. LTDA located in the province of Santo Domingo de los Tsáchilas. From the results obtained, it has been determined the influence of coarse aggregates on the percentage of effective capillary porosity valúes, of 1/2" and 3/4" have less than 10%, within the mixing designs when it is replaced up to 3% in the fine aggregate. The decrease of the porosity in the mixtures was based on the decrease in the a/c ratio with the addition of glass fiber; the greater the addition of glass fiber, the lower the settling/fluidity of the concrete. Therefore, the decrease of porosity with the addition of glass fiber improves the redistribution of micro-cracks with the use of this material. Keywords: Granulometry, Porosity, Compressive strength, glass fiber.Debido a la trascendencia de la granulometría, dentro del área de conocimiento en materia de la construcción, la misma que nos permite estudiar y conocer el tamaño de los agregados al momento de hacer una mezcla, como es el caso del agregado grueso, dentro del estudio en la porosidad del hormigón. Esta investigación tiene como objetivo principal, evaluar el tamaño máximo del agregado y su influencia en la porosidad de un hormigón, elaborado con fibra de vidrio como sustituto de este; a través de la metodología de Goran Fagerlund. Para la evaluación de la porosidad en un hormigón convencional con fibra de vidrio, se efectuaron en base a un diseño por el método ACI y con una resistencia de 21MPa. Las muestras empleadas de los agregados gruesos, provinieron de la cantera COPETO.C. LTDA ubicada en la provincia de Santo Domingo de los Tsáchilas. De los resultados obtenidos, se ha determinado la incidencia de los agregados gruesos en los valores del porcentaje de porosidad capilar efectivo, de 1/2" y 3/4" tienen menos del 10%, dentro de los diseños de mezcla cuando se sustituye hasta un 3% en el agregado fino. El descenso de la porosidad en las mezclas, se basó en el decrecimiento de la relación a/c con la adición de fibra de vidrio; a mayor adición de fibra de vidrio, menor asentamiento/fluidez del hormigón. Por ende, el decrecimiento de la porosidad con la adición de fibra de vidrio, mejora la redistribución de micro fisuras con el uso de este material. Palabras clave: Granulometría, Porosidad, Resistencia a compresión, Fibra de vidrio. Abstract Due to the importance of the granulometry, within the area of knowledge in the field of construction, the same that allows us to study and know the size of the aggregates at the moment of making a mixture, as is the case of coarse aggregate, within the study of the porosity the concrete.This investigation has as main objective, to evaluate the maximum size of the aggregate and it’s influence on the porosity of a concrete, made with glass fiber as a substitute for this; through Goran Fagerlund's methodology. For the evaluation of porosity in a conventional concrete with glass fiber, were carried out on the basis of a design by the ACI method and with a resistance of 21MPa. The samples used of the coarse aggregates came from the quarry COPETO.C. LTDA located in the province of Santo Domingo de los Tsáchilas. From the results obtained, it has been determined the influence of coarse aggregates on the percentage of effective capillary porosity valúes, of 1/2" and 3/4" have less than 10%, within the mixing designs when it is replaced up to 3% in the fine aggregate. The decrease of the porosity in the mixtures was based on the decrease in the a/c ratio with the addition of glass fiber; the greater the addition of glass fiber, the lower the settling/fluidity of the concrete. Therefore, the decrease of porosity with the addition of glass fiber improves the redistribution of micro-cracks with the use of this material. Keywords: Granulometry, Porosity, Compressive strength, glass fiber. Información del manuscrito:Fecha de recepción: 09 de febrero de 2023.Fecha de aceptación: 28 de abril de 2023.Fecha de publicación: 12 de mayo de 2023

Adición de puzolana natural (diatomita) para mejorar la resistencia en mortero estructural

The investigative work carried out consisted in the evaluation of type (M) structural mortars, according to the standard (ASTM C109/C109 M-99), depending on the compressive strength. The tests were carried out with specific materials such as: Type I Portland cement, diatomite Pozzolana, crushed sand from (Megarok S.A.) and water. The mixtures were worked at the same fluidity level, obtaining homogeneous mixtures with great workability. The molding of the specimens was carried out in cubes of 50mm on each side. Diatomite was added proportionally at 15% and 20% as a replacement for Portland cement. Breakage tests were performed at 7, 14, 28, and 91 days of curing, which were successful, creating a type M (structural) mortar. The diatomite was very efficient thanks to its high amorphous silica content, which reacts with the hydration products of the cement ( and the alkalis  and  among others) to produce a structural mortar in order to obtain the required level of resistance and improve its durability. Keywords: Pozzolan, Diatomite, Resistance, Mortar, Structural.El trabajo investigativo realizado consistió en la evaluación de morteros estructurales tipo (M), según la norma (ASTM C109/C109 M-99), en función de la resistencia a la compresión. Los ensayos se realizaron con materiales específicos como: cemento Portland tipo I, Puzolana diatomita, arena triturada de (Megarok S.A.) y agua. Las mezclas fueron trabajadas a un mismo nivel de fluidez obteniendo mezclas homogéneas y de gran trabajabilidad. El moldeo de los especímenes se realizó en cubos de 50mm por cada lado. La diatomita fue adicionada proporcionalmente en el 15% y 20%como remplazo del cemento Portland. Los ensayos de rotura se realizaron a los 7, 14, 28, y 91 días de curado, los cuales resultaron exitosos, creando un mortero tipo M (estructural). La diatomita resulto muy eficiente gracias a su alto contenido de sílice amorfa, la que reacciona con los productos de hidratación del cemento (Ca〖OH〗_2 y los álcalis NaOH y KOH entre otros) para producir un mortero estructural con el fin de obtener el nivel de resistencia requerido y mejorar su durabilidad. Palabras clave: Puzolana, Diatomita, Resistencia, Mortero, Estructural. Abstract The investigative work carried out consisted in the evaluation of type (M) structural mortars, according to the standard (ASTM C109/C109 M-99), depending on the compressive strength. The tests were carried out with specific materials such as: Type I Portland cement, diatomite Pozzolana, crushed sand from (Megarok S.A.) and water. The mixtures were worked at the same fluidity level, obtaining homogeneous mixtures with great workability. The molding of the specimens was carried out in cubes of 50mm on each side. Diatomite was added proportionally at 15% and 20% as a replacement for Portland cement. Breakage tests were performed at 7, 14, 28, and 91 days of curing, which were successful, creating a type M (structural) mortar. The diatomite was very efficient thanks to its high amorphous silica content, which reacts with the hydration products of the cement ( and the alkalis  and  among others) to produce a structural mortar in order to obtain the required level of resistance and improve its durability. Keywords: Pozzolan, Diatomite, Resistance, Mortar, Structural. Información del manuscrito:Fecha de recepción: 09 de enero de 2023.Fecha de aceptación: 23 de marzo de 2023.Fecha de publicación: 28 de marzo de 2023