Harveth Gil - Academia.edu (original) (raw)

Papers by Harveth Gil

Research paper thumbnail of Characterization and Evaluation of Lightweight Fly Ash Concrete Modified with EPS

Civil & Environmental Engineering eJournal, 2019

This research studies the influence of partial substitution of fine aggregate by lightweight expa... more This research studies the influence of partial substitution of fine aggregate by lightweight expanded polystyrene (EPS) in the behavior of a simple concrete modified with fly ash (FA). Replacement of 10%, 30%, 60% by volume of EPS and 10% FA of cement were used. Destructive and non-destructive tests to cylindrical specimens were carried out to assess physical and mechanical properties such as density, compressive strength, and dynamic modulus of elasticity. Additionally, the cementing material and EPS was characterized by scanning electron microscopy (SEM), X-Ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). According to the results, the aggregate percentage substitution range that guarantees a significant reduction in density and a minimum decrease in compressive strength is found between 10% and 30%.

Research paper thumbnail of Mechanical properties and sustainability aspects of coconut fiber modified concrete

Scientia et Technica, 2021

Coir fiber has been examined for their suitability as reinforcement of concrete. Mechanical prope... more Coir fiber has been examined for their suitability as reinforcement of concrete. Mechanical properties and sustainability aspects of concrete composites were estimated after 7. 14, and 28 days of curing. Natural reinforcement of 0.46 and 0.62% by weight of coir fiber was added. Fibers were analyzed by means of scanning electron microscope (SEM). Besides, an Eco-audit tool has been used to estimate energy and carbon emission of material, manufacturing, transportation, and disposal phases. It was found that fibers additions lowered the compressive strength compared to plain concrete. However, failures of the composites exhibited good post-cracking behavior. The use of vegetable fibers affects positively the life cycle of the material. Eco-audit results indicate that there is a potential to reduce between 9.15% and 13.35% of embodied energy and between 9.61% and 13.94% of CO2 during the material production phase. These suggest that coir fibers could be useful from the environmental vie...

Research paper thumbnail of Relevant aspects of the mobility and its relation with environment in the Valle de Aburrá: a review

Ingeniería y Desarrollo, 2018

Fecha de recepción: 26 de septiembre de 2017 Fecha de aceptación: 16 de marzo de 2018 Resumen Deb... more Fecha de recepción: 26 de septiembre de 2017 Fecha de aceptación: 16 de marzo de 2018 Resumen Debido al creciente número de la población vehicular en las ciudades y la necesidad de realizar desplazamientos urbanos, se han generado perjuicios a la sociedad como, por ejemplo, la contaminación ambiental y la congestión del tráfico vehicular. Este artículo presenta una revisión bibliográfica del estado del arte de los aspectos más importantes de este problema, investigaciones que se han realizado para reducirlo y, en particular, las estrategias propuestas aplicadas en Medellín por parte del Área Metropolitana del Valle de Aburrá. Finalmente, se realiza una comparación con las diferentes aproximaciones que se han implementado en algunas ciudades del mundo altamente pobladas.

Research paper thumbnail of Mechanical properties of mortars modified with wood waste ash

Journal of the Indian Academy of Wood Science, 2020

In this paper, a comparative study of the mechanical behavior of mortars with cement replacement ... more In this paper, a comparative study of the mechanical behavior of mortars with cement replacement by wood waste ash (WWA) of 0, 0.5, 1 and 3% by weight was performed. Physical and chemical properties such as density, dynamic modulus of elasticity and compressive strength were evaluated after 7, 30 and 90 days of curing. WWA and cement were analyzed by means of X-ray diffraction and X-ray fluorescence. After failure, the composites were characterized using scanning electron microscopy. The results of the study demonstrate that mortars modified with 0.5% of WWA comply with the Colombian construction requirements, being slightly better in compressive strength and with lower density compared to mortars without modification. The use of WWA as replacement of cement results in weight savings of 4.5, 9 and 27 kg for 0.5, 1 and 3% of WWA, respectively. The mortars are suitable to be used on cement composites due to their adequate physicochemical properties and their positive effect from the sustainability standpoint.

Research paper thumbnail of Desarrollo de una herramienta informática para la selección de materiales termoplásticos en el entorno nacional

Revista Politécnica, 2018

Una aproximación multi-objetivos fue aplicada al diseño de un software de selección de materiales... more Una aproximación multi-objetivos fue aplicada al diseño de un software de selección de materiales. El propósito del software es asistir a los ingenieros y diseñadores para que desempeñen una selección práctica en el momento de toma de decisiones para aplicaciones que involucren materiales termoplásticos. El proceso de selección incluye aspectos técnicos del material también como cuestiones ambientales que dan origen a soluciones sostenibles. Se implementó un método con propiedades ponderadas para obtener un ranking de materiales. Para desarrollar el Software se utilizó Visual Basic 6.0 con la ayuda de Excel para realizar un análisis de ciclo de vida racionalizado (ACVR). Se involucraron aspectos de sostenibilidad para obtener la matriz del producto ambientalmente responsable y gráficos de dianas. La principal fuente de datos provino de materiales disponibles localmente lo que permite una selección efectiva. Finalmente, un estudio de caso fue utilizado para ilustrar la aplicación del...

Research paper thumbnail of Atmospheric corrosion of copper and silver influenced by particulate matter

Journal of Solid State Electrochemistry, 2016

The atmospheric corrosion of copper and silver influenced by graphite and alumina as particulate ... more The atmospheric corrosion of copper and silver influenced by graphite and alumina as particulate matter (PM) in an environment containing 200 μg m−3 SO2 + 150 μg m−3 NO2 at 85% RH and 25 °C was analyzed. Different proportions of PM mixture conditions were used, and the corrosion rate was followed using gravimetric analysis. Results of linear sweep voltammetry (LSV) and coulometric reduction (CR) indicated that larger corrosion rates were obtained in the presence of deposited PM. Under present exposure conditions, copper corrosion rate was larger than silver corrosion rate. X-ray diffraction (XRD) shows the presence of cuprite (Cu2O) and brochantite (Cu4SO4(OH)6) in the case of copper and achantite (Ag2S) in the case of silver.

Research paper thumbnail of The initial atmospheric corrosion of copper and zinc induced by carboxylic acids : Quantitative in situ analysis and computer simulations

Degradation of metals through atmospheric corrosion is a most important and costly phenomenon wit... more Degradation of metals through atmospheric corrosion is a most important and costly phenomenon with significant effects on, e.g., the lifespan of industrial materials, the reliability of electronic components and military equipment, and the aesthetic appearance of our cultural heritage. Atmospheric corrosion is the result of the interaction between the metal and its atmospheric environment, and occurs in the presence of a thin aqueous adlayer. The common incorporation of pollutant species into this adlayer usually enhances the degradation process. During atmospheric corrosion indoors, low concentrations of organic atmospheric constituents, such as formic, acetic, propionic, butyric and oxalic acids, have found to play an accelerating role on a broad range of metals or their alloys, including lead, steel, nickel, copper, cadmium,

Research paper thumbnail of Characterization of atmospheric corrosion products formed on silver in tropical-mountain environments

Journal of Solid State Electrochemistry, 2015

An electrochemical characterization of the atmospheric corrosion products formed on silver expose... more An electrochemical characterization of the atmospheric corrosion products formed on silver exposed to Colombian tropical-mountain sites is reported. Rural and urban environments were selected for exposures up to 6 months. Corrosion products were characterized by X-ray diffraction (XRD), linear sweep voltammetry (LSV), and coulometric reduction (CR). XRD patterns shows that achantite (Ag2S) and silver (I) oxide (Ag2O) were the main corrosion products. Electrochemical results show a relationship between the reduction charge obtained by LSV and the sulfide thickness estimated by CR. To perform a correct assignments of all reduction peaks, cyclic voltammetry (CV) and subsequent anodic polarizations at specific potentials of pure silver surface were made in different solutions, such as 0.1 M NaOH, 0.01 M Na2S, and 0.1 M Na2SO4. This procedure was reliable in terms of the electrochemical formation of Ag2S, Ag2O, and Ag2SO4, respectively. Electrochemical techniques were highly reproducible and sensible to detect and measure silver corrosion rates in this type of environments.

Research paper thumbnail of Atmospheric corrosion of copper induced by low concentration of carboxylic acids

Tesis (Doctor en Ingeniería) Universidad de Antioquia Facultad de Ingeniería The interaction of c... more Tesis (Doctor en Ingeniería) Universidad de Antioquia Facultad de Ingeniería The interaction of carboxylic acids with copper is a phenomenon found in both outdoors and, more commonly, indoors. The influence on copper of some carboxylic acids (formic, acetic, propionic, and butyric) have so far been studied at concentrations levels at least three or four orders of magnitude higher than actual indoor conditions (< 20 ppb, volume parts per billion), and with only limited emphasis on any mechanistic approach. In this doctoral study a unique analytical setup has been successfully applied for in situ characterization and quantification of corrosion products formed during initial atmospheric corrosion of copper in the presence of acetic, formic or propionic acid. The setup is based on monitoring mass changes by the quartz crystal microbalance (QCM) and simultaneously identifying the chemical species by infrared reflection-absorption spectroscopy (IRAS). Post-analysis of corrosion produc...

Research paper thumbnail of Papers in peer-reviewed journals published in 2008

Research paper thumbnail of Influence of Environmental Factors in the Atmospheric Corrosion of Copper in the Presence of Propionic Acid

Journal of the Chilean Chemical Society, 2009

Exposure time, pollutant concentration, and relative humidity (RH) are important environmental va... more Exposure time, pollutant concentration, and relative humidity (RH) are important environmental variables for the atmospheric corrosion of copper in the presence of propionic acid vapors. This paper shows the most outstanding results into the effect of these variables. This study was carried out by mean of exposures at dynamic conditions in 260, 380, and 680 ppbv propionic acid, with relative humidities of 70% and 90%. The effect of the propionic acid was also evaluated in static conditions with 4, 40, and 120 ppmv propionic acid with relative humidities of 40%, 80%, and 100% RH. All the samples were evaluated by triplicate within 21 days of exposure. The corrosion rate was used to quantify the degradation of copper by mean of weight loss and coulometric reduction technique. Coulometric reduction indicates that the charge needed to reduce the oxides increases as exposure time, relative humidity and pollutant concentration increases. On the other hand, the corrosion rate determined gravimetrically, confirms that at a higher relative humidity and higher propionic acid concentration the copper deterioration is also higher.

Research paper thumbnail of Study of the copper corrosion mechanism in the presence of propionic acid vapors

Journal of the Brazilian Chemical Society, 2009

O mecanismo da interação entre o cobre e os vapores do ácido propiônico é apresentado. As exposiç... more O mecanismo da interação entre o cobre e os vapores do ácido propiônico é apresentado. As exposições foram realizadas em diferentes tempos e concentração de poluentes. Varredura Catódica, XRD e SEM foram usados para quantificar o grau de deterioração. Os resultados obtidos foram explicados pelo seguinte mecanismo: Uma camada do cuprita (Cu 2 O) é formada imediatamente. Este composto, na presença da água adsorvida é oxidado a tenorita (CuO) com aumento do pH. A hidratação da camada de tenorita beneficia a formação de um hidróxido CuO•xH 2 O. Enquanto o nível do poluente é aumentado, o propionato básico insolúvel é formado (Cu(OH) x (Pro) 2-x). Concentrações mais elevadas de ácido propiônico acidificam as mono camadas e um composto novo Cu (Pro) 2 •H 2 O começa a se precipitar em pH baixo. Este é o constituinte principal da pátina verdeoliva formada nessas condições. Este mecanismo concorda, em termos gerais, com os propostos em trabalhos precedentes visando estudar a interação entre o cobre e os ácidos acético e fórmico. The interaction mechanism between copper and propionic acid vapors is shown. Exposures were carried out to various pollutant concentrations and times. Cathodic scan, x-ray diffraction (XRD) and scanning electrode microscope (SEM) were used to quantify the degree of deterioration. The results obtained were explained by the following mechanism: A cuprite (Cu 2 O) layer covers the copper surface immediately; this compound in presence of adsorbed water is oxidized to tenorite (CuO). The hydration of the tenorite layer benefits the formation of a hydroxide compound such as CuO•xH 2 O. As the pollutant level is increased, insoluble basic propionate is formed (Cu(OH) x (CH 3 CH 2 COO) 2-x). Higher concentrations of propionic acid acidify the monolayers and a new compound Cu(CH 3 CH 2 COO) 2 •H 2 O begins to precipitate at low pH, this is the main constituent of the green olive patina formed under these conditions. This mechanism agrees, in general terms, with those proposed in previous works to study the interaction between copper and the acetic and formic acids.

Research paper thumbnail of Initial Atmospheric Corrosion of Copper Induced by Carboxylic Acids

Journal of The Electrochemical Society, 2007

The interaction of carboxylic acids with copper is a phenomenon found both outdoors and, more com... more The interaction of carboxylic acids with copper is a phenomenon found both outdoors and, more commonly, indoors. The influence on copper of some carboxylic acids (formic, acetic, propionic, and butyric) have so far been studied at concentrations levels at least three or four orders of magnitude higher than actual indoor conditions (< 20 ppb, volume parts per billion), and with only limited emphasis on any mechanistic approach. In this licentiate study a unique analytical setup has been successfully applied for in situ characterization and quantification of corrosion products formed during initial atmospheric corrosion of copper in the presence of acetic, formic or propionic acid. The setup is based on monitoring mass changes by the quartz crystal microbalance (QCM) and simultaneously identifying the chemical species by infrared reflection-absorption spectroscopy (IRAS). Post-analysis of corrosion products was performed by coulometric reduction (mass of copper (I) oxide formed), grazing incidence xray diffraction (phase identification) and atomic force microscopy (surface topography). The absolute amounts of mass of individual constituents in the corrosion products, mainly copper (I) oxide or cuprite, copper (II) carboxylate and water or hydroxyl groups, have been deduced in situ during exposure in 120 ppb of carboxylic acid concentration, 95% relative humidity and 20ºC. An overall result is the consistency of analytical information obtained. For copper (I) oxide the quantified data estimated from IRAS, QCM or coulomeric reduction agrees with a relative accuracy of 12 % or better. The interaction of copper with the carboxylic acids seems to follow two spatially separated main pathways. A proton-induced dissolution of cuprous ions followed by the formation of copper (I) oxide, and a carboxylate-induced dissolution followed by the formation of copper (II) carboxylate. The first pathway is initially very fast but levels off with a more uniform growth over the surface. This pathway dominates in acetic acid. The second pathway exhibits iii a more constant growth rate and localized growth, and dominates in formic acid. Propionic acid exhibits low rates for both pathways. The difference between the carboxylic acids with respect to both total corrosion rate and carboxylate-induced dissolution can be attributed to differences in acid dissociation constant and deposition velocity.

Research paper thumbnail of Quantitative In Situ Analysis of Initial Atmospheric Corrosion of Copper Induced by Acetic Acid

Journal of The Electrochemical Society, 2007

The interaction of carboxylic acids with copper is a phenomenon found both outdoors and, more com... more The interaction of carboxylic acids with copper is a phenomenon found both outdoors and, more commonly, indoors. The influence on copper of some carboxylic acids (formic, acetic, propionic, and butyric) have so far been studied at concentrations levels at least three or four orders of magnitude higher than actual indoor conditions (< 20 ppb, volume parts per billion), and with only limited emphasis on any mechanistic approach. In this licentiate study a unique analytical setup has been successfully applied for in situ characterization and quantification of corrosion products formed during initial atmospheric corrosion of copper in the presence of acetic, formic or propionic acid. The setup is based on monitoring mass changes by the quartz crystal microbalance (QCM) and simultaneously identifying the chemical species by infrared reflection-absorption spectroscopy (IRAS). Post-analysis of corrosion products was performed by coulometric reduction (mass of copper (I) oxide formed), grazing incidence xray diffraction (phase identification) and atomic force microscopy (surface topography). The absolute amounts of mass of individual constituents in the corrosion products, mainly copper (I) oxide or cuprite, copper (II) carboxylate and water or hydroxyl groups, have been deduced in situ during exposure in 120 ppb of carboxylic acid concentration, 95% relative humidity and 20ºC. An overall result is the consistency of analytical information obtained. For copper (I) oxide the quantified data estimated from IRAS, QCM or coulomeric reduction agrees with a relative accuracy of 12 % or better. The interaction of copper with the carboxylic acids seems to follow two spatially separated main pathways. A proton-induced dissolution of cuprous ions followed by the formation of copper (I) oxide, and a carboxylate-induced dissolution followed by the formation of copper (II) carboxylate. The first pathway is initially very fast but levels off with a more uniform growth over the surface. This pathway dominates in acetic acid. The second pathway exhibits iii a more constant growth rate and localized growth, and dominates in formic acid. Propionic acid exhibits low rates for both pathways. The difference between the carboxylic acids with respect to both total corrosion rate and carboxylate-induced dissolution can be attributed to differences in acid dissociation constant and deposition velocity.

Research paper thumbnail of GILDES Model Simulations of the Atmospheric Corrosion of Copper Induced by Low Concentrations of Carboxylic Acids

Journal of The Electrochemical Society, 2011

A computer simulation with a GILDES-based model using the COMSOL multiphysics software was perfor... more A computer simulation with a GILDES-based model using the COMSOL multiphysics software was performed for copper exposed to low concentrations of carboxylic acids in humidified air at room temperature. GILDES is a six-regime computer model (Gas, the Interface between gas and liquid, the Liquid, the Deposition layer, the Electrodic region near the surface and the Solid). The simulations were compared to previously published in-situ results for copper at the same conditions analysed by a quartz crystal microbalance (QCM) and infrared reflection absorption spectroscopy (IRAS). Experimental and calculated results agree with each other with respect to the effect of corrosion, showing formic acid as the most aggressive followed by acetic and propionic acid. This is supported by a higher ligand-and proton-promoted dissolution found in formic acid exposures, followed by acetic and propionic exposures. The dominating precipitated phases were Cu 2 O, Cu(OH) 2 , Cu(CH 3 COO) 2 • H 2 O, Cu(HCOO) 2 • 4H 2 O and Cu(CH 3 CH 2 COO) 2 • H 2 O. Besides Cu 2 O, the simulations suggest that the hydrated form of the respective carboxylates is the most likely compound to be formed in this type of atmospheres.

Research paper thumbnail of Electrochemical reduction modeling of copper oxides obtained during in situ and ex situ conditions in the presence of acetic acid

Electrochimica Acta, 2009

We used the potentiodynamic reduction technique to study the mechanism of copper oxide formation ... more We used the potentiodynamic reduction technique to study the mechanism of copper oxide formation in the presence of acetic acid. We performed all reductions under neutral conditions (0.1M KCl) until hydrogen evolution. We produced the copper oxides in an environment containing 0, 500, and 800ppb acetic acid at high relative humidity. We then compared experimental results between electrochemically produced oxide films obtained by imposing anodic potentials to copper specimens in several concentrations of pure acetic acid (1, 0.1, 0.01 and 0.001M). We found that, as the concentration of the acid decreases, the formation of the copper oxide (I) increases. We also found the same peaks in samples produced under the synthetic environment. We modeled the curves, taking into account the electrochemical reduction of copper (II) oxide (CuO), amorphous cuprite (Cu2O)am, intermediate cuprite (Cu2O)in, crystalline cuprite (Cu2O)cr, and hydrogen. These oxides have been previously detected in similar conditions. We found no evidence of copper carboxylate founding samples produced by the electrochemical method.

Research paper thumbnail of 2007 W.R. Whitney Award Lecture:Molecular In Situ Studies of Atmospheric Corrosion

CORROSION, 2007

Atmospheric corrosion involves chemical, electrochemical, and physical processes in three phases ... more Atmospheric corrosion involves chemical, electrochemical, and physical processes in three phases (solid, liquid, and gas) and two interfaces (solid∕ liquid and liquid∕ gas). Because of inherent experimental and conceptual difficulties, scientific efforts to characterize this ...

Research paper thumbnail of Indoor atmospheric corrosion of electronic materials in tropical-mountain environments

Corrosion Science, 2010

Indoor corrosion rate during one year exposure for carbon steel, copper, nickel, and tin was dete... more Indoor corrosion rate during one year exposure for carbon steel, copper, nickel, and tin was determined in three different atmospheres in Colombia. In addition, pollutants deposition rates and environmental parameters were also measured during indoor-outdoor conditions. The results show higher pollutant deposition in outdoor conditions, while inside metallic boxes the pollutant deposition significantly diminishes. No difference for relative humidity values was found between inside and outside measurements. For all samples, except nickel, the corrosion rate decrease with exposure time. The nature of corrosion products was found to be related to the exposure conditions.

Research paper thumbnail of Estudio del comportamiento mecánico de morteros modificados con fibras de aserrín bajo esfuerzos de compresión

Ingeniería y Desarrollo, 2019

En este artículo, se presenta un estudio sobre el comportamiento mecánico de morteros modificados... more En este artículo, se presenta un estudio sobre el comportamiento mecánico de morteros modificados con fibras de aserrín bajo cargas de compresión. Se estimó la densidad, resistencia a la compresión, y el módulo de elasticidad dinámico de morteros modificados con 0, 0,5, 1 y 3% en peso de fibra de aserrín. Los compuestos fueron evaluados luego de 7, 30 y 90 días de curado. Además, se utilizó microscopia electrónica de barrido (SEM) y espectroscopía de rayos X de energía dispersa (EDX) para caracterizar la morfología y encontrar la composición elemental tanto de las fibras como de la matriz de cemento. Los resultados muestran que a mayor porcentaje de aserrín, la resistencia, el módulo de elasticidad y la densidad disminuyen. Se sugiere utilizar hasta 1% de fibra de aserrín en morteros para evitar una reducción importante en las propiedades mecánicas de los morteros.

Research paper thumbnail of Characterization and Evaluation of Lightweight Fly Ash Concrete Modified with EPS

Civil & Environmental Engineering eJournal, 2019

This research studies the influence of partial substitution of fine aggregate by lightweight expa... more This research studies the influence of partial substitution of fine aggregate by lightweight expanded polystyrene (EPS) in the behavior of a simple concrete modified with fly ash (FA). Replacement of 10%, 30%, 60% by volume of EPS and 10% FA of cement were used. Destructive and non-destructive tests to cylindrical specimens were carried out to assess physical and mechanical properties such as density, compressive strength, and dynamic modulus of elasticity. Additionally, the cementing material and EPS was characterized by scanning electron microscopy (SEM), X-Ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). According to the results, the aggregate percentage substitution range that guarantees a significant reduction in density and a minimum decrease in compressive strength is found between 10% and 30%.

Research paper thumbnail of Mechanical properties and sustainability aspects of coconut fiber modified concrete

Scientia et Technica, 2021

Coir fiber has been examined for their suitability as reinforcement of concrete. Mechanical prope... more Coir fiber has been examined for their suitability as reinforcement of concrete. Mechanical properties and sustainability aspects of concrete composites were estimated after 7. 14, and 28 days of curing. Natural reinforcement of 0.46 and 0.62% by weight of coir fiber was added. Fibers were analyzed by means of scanning electron microscope (SEM). Besides, an Eco-audit tool has been used to estimate energy and carbon emission of material, manufacturing, transportation, and disposal phases. It was found that fibers additions lowered the compressive strength compared to plain concrete. However, failures of the composites exhibited good post-cracking behavior. The use of vegetable fibers affects positively the life cycle of the material. Eco-audit results indicate that there is a potential to reduce between 9.15% and 13.35% of embodied energy and between 9.61% and 13.94% of CO2 during the material production phase. These suggest that coir fibers could be useful from the environmental vie...

Research paper thumbnail of Relevant aspects of the mobility and its relation with environment in the Valle de Aburrá: a review

Ingeniería y Desarrollo, 2018

Fecha de recepción: 26 de septiembre de 2017 Fecha de aceptación: 16 de marzo de 2018 Resumen Deb... more Fecha de recepción: 26 de septiembre de 2017 Fecha de aceptación: 16 de marzo de 2018 Resumen Debido al creciente número de la población vehicular en las ciudades y la necesidad de realizar desplazamientos urbanos, se han generado perjuicios a la sociedad como, por ejemplo, la contaminación ambiental y la congestión del tráfico vehicular. Este artículo presenta una revisión bibliográfica del estado del arte de los aspectos más importantes de este problema, investigaciones que se han realizado para reducirlo y, en particular, las estrategias propuestas aplicadas en Medellín por parte del Área Metropolitana del Valle de Aburrá. Finalmente, se realiza una comparación con las diferentes aproximaciones que se han implementado en algunas ciudades del mundo altamente pobladas.

Research paper thumbnail of Mechanical properties of mortars modified with wood waste ash

Journal of the Indian Academy of Wood Science, 2020

In this paper, a comparative study of the mechanical behavior of mortars with cement replacement ... more In this paper, a comparative study of the mechanical behavior of mortars with cement replacement by wood waste ash (WWA) of 0, 0.5, 1 and 3% by weight was performed. Physical and chemical properties such as density, dynamic modulus of elasticity and compressive strength were evaluated after 7, 30 and 90 days of curing. WWA and cement were analyzed by means of X-ray diffraction and X-ray fluorescence. After failure, the composites were characterized using scanning electron microscopy. The results of the study demonstrate that mortars modified with 0.5% of WWA comply with the Colombian construction requirements, being slightly better in compressive strength and with lower density compared to mortars without modification. The use of WWA as replacement of cement results in weight savings of 4.5, 9 and 27 kg for 0.5, 1 and 3% of WWA, respectively. The mortars are suitable to be used on cement composites due to their adequate physicochemical properties and their positive effect from the sustainability standpoint.

Research paper thumbnail of Desarrollo de una herramienta informática para la selección de materiales termoplásticos en el entorno nacional

Revista Politécnica, 2018

Una aproximación multi-objetivos fue aplicada al diseño de un software de selección de materiales... more Una aproximación multi-objetivos fue aplicada al diseño de un software de selección de materiales. El propósito del software es asistir a los ingenieros y diseñadores para que desempeñen una selección práctica en el momento de toma de decisiones para aplicaciones que involucren materiales termoplásticos. El proceso de selección incluye aspectos técnicos del material también como cuestiones ambientales que dan origen a soluciones sostenibles. Se implementó un método con propiedades ponderadas para obtener un ranking de materiales. Para desarrollar el Software se utilizó Visual Basic 6.0 con la ayuda de Excel para realizar un análisis de ciclo de vida racionalizado (ACVR). Se involucraron aspectos de sostenibilidad para obtener la matriz del producto ambientalmente responsable y gráficos de dianas. La principal fuente de datos provino de materiales disponibles localmente lo que permite una selección efectiva. Finalmente, un estudio de caso fue utilizado para ilustrar la aplicación del...

Research paper thumbnail of Atmospheric corrosion of copper and silver influenced by particulate matter

Journal of Solid State Electrochemistry, 2016

The atmospheric corrosion of copper and silver influenced by graphite and alumina as particulate ... more The atmospheric corrosion of copper and silver influenced by graphite and alumina as particulate matter (PM) in an environment containing 200 μg m−3 SO2 + 150 μg m−3 NO2 at 85% RH and 25 °C was analyzed. Different proportions of PM mixture conditions were used, and the corrosion rate was followed using gravimetric analysis. Results of linear sweep voltammetry (LSV) and coulometric reduction (CR) indicated that larger corrosion rates were obtained in the presence of deposited PM. Under present exposure conditions, copper corrosion rate was larger than silver corrosion rate. X-ray diffraction (XRD) shows the presence of cuprite (Cu2O) and brochantite (Cu4SO4(OH)6) in the case of copper and achantite (Ag2S) in the case of silver.

Research paper thumbnail of The initial atmospheric corrosion of copper and zinc induced by carboxylic acids : Quantitative in situ analysis and computer simulations

Degradation of metals through atmospheric corrosion is a most important and costly phenomenon wit... more Degradation of metals through atmospheric corrosion is a most important and costly phenomenon with significant effects on, e.g., the lifespan of industrial materials, the reliability of electronic components and military equipment, and the aesthetic appearance of our cultural heritage. Atmospheric corrosion is the result of the interaction between the metal and its atmospheric environment, and occurs in the presence of a thin aqueous adlayer. The common incorporation of pollutant species into this adlayer usually enhances the degradation process. During atmospheric corrosion indoors, low concentrations of organic atmospheric constituents, such as formic, acetic, propionic, butyric and oxalic acids, have found to play an accelerating role on a broad range of metals or their alloys, including lead, steel, nickel, copper, cadmium,

Research paper thumbnail of Characterization of atmospheric corrosion products formed on silver in tropical-mountain environments

Journal of Solid State Electrochemistry, 2015

An electrochemical characterization of the atmospheric corrosion products formed on silver expose... more An electrochemical characterization of the atmospheric corrosion products formed on silver exposed to Colombian tropical-mountain sites is reported. Rural and urban environments were selected for exposures up to 6 months. Corrosion products were characterized by X-ray diffraction (XRD), linear sweep voltammetry (LSV), and coulometric reduction (CR). XRD patterns shows that achantite (Ag2S) and silver (I) oxide (Ag2O) were the main corrosion products. Electrochemical results show a relationship between the reduction charge obtained by LSV and the sulfide thickness estimated by CR. To perform a correct assignments of all reduction peaks, cyclic voltammetry (CV) and subsequent anodic polarizations at specific potentials of pure silver surface were made in different solutions, such as 0.1 M NaOH, 0.01 M Na2S, and 0.1 M Na2SO4. This procedure was reliable in terms of the electrochemical formation of Ag2S, Ag2O, and Ag2SO4, respectively. Electrochemical techniques were highly reproducible and sensible to detect and measure silver corrosion rates in this type of environments.

Research paper thumbnail of Atmospheric corrosion of copper induced by low concentration of carboxylic acids

Tesis (Doctor en Ingeniería) Universidad de Antioquia Facultad de Ingeniería The interaction of c... more Tesis (Doctor en Ingeniería) Universidad de Antioquia Facultad de Ingeniería The interaction of carboxylic acids with copper is a phenomenon found in both outdoors and, more commonly, indoors. The influence on copper of some carboxylic acids (formic, acetic, propionic, and butyric) have so far been studied at concentrations levels at least three or four orders of magnitude higher than actual indoor conditions (< 20 ppb, volume parts per billion), and with only limited emphasis on any mechanistic approach. In this doctoral study a unique analytical setup has been successfully applied for in situ characterization and quantification of corrosion products formed during initial atmospheric corrosion of copper in the presence of acetic, formic or propionic acid. The setup is based on monitoring mass changes by the quartz crystal microbalance (QCM) and simultaneously identifying the chemical species by infrared reflection-absorption spectroscopy (IRAS). Post-analysis of corrosion produc...

Research paper thumbnail of Papers in peer-reviewed journals published in 2008

Research paper thumbnail of Influence of Environmental Factors in the Atmospheric Corrosion of Copper in the Presence of Propionic Acid

Journal of the Chilean Chemical Society, 2009

Exposure time, pollutant concentration, and relative humidity (RH) are important environmental va... more Exposure time, pollutant concentration, and relative humidity (RH) are important environmental variables for the atmospheric corrosion of copper in the presence of propionic acid vapors. This paper shows the most outstanding results into the effect of these variables. This study was carried out by mean of exposures at dynamic conditions in 260, 380, and 680 ppbv propionic acid, with relative humidities of 70% and 90%. The effect of the propionic acid was also evaluated in static conditions with 4, 40, and 120 ppmv propionic acid with relative humidities of 40%, 80%, and 100% RH. All the samples were evaluated by triplicate within 21 days of exposure. The corrosion rate was used to quantify the degradation of copper by mean of weight loss and coulometric reduction technique. Coulometric reduction indicates that the charge needed to reduce the oxides increases as exposure time, relative humidity and pollutant concentration increases. On the other hand, the corrosion rate determined gravimetrically, confirms that at a higher relative humidity and higher propionic acid concentration the copper deterioration is also higher.

Research paper thumbnail of Study of the copper corrosion mechanism in the presence of propionic acid vapors

Journal of the Brazilian Chemical Society, 2009

O mecanismo da interação entre o cobre e os vapores do ácido propiônico é apresentado. As exposiç... more O mecanismo da interação entre o cobre e os vapores do ácido propiônico é apresentado. As exposições foram realizadas em diferentes tempos e concentração de poluentes. Varredura Catódica, XRD e SEM foram usados para quantificar o grau de deterioração. Os resultados obtidos foram explicados pelo seguinte mecanismo: Uma camada do cuprita (Cu 2 O) é formada imediatamente. Este composto, na presença da água adsorvida é oxidado a tenorita (CuO) com aumento do pH. A hidratação da camada de tenorita beneficia a formação de um hidróxido CuO•xH 2 O. Enquanto o nível do poluente é aumentado, o propionato básico insolúvel é formado (Cu(OH) x (Pro) 2-x). Concentrações mais elevadas de ácido propiônico acidificam as mono camadas e um composto novo Cu (Pro) 2 •H 2 O começa a se precipitar em pH baixo. Este é o constituinte principal da pátina verdeoliva formada nessas condições. Este mecanismo concorda, em termos gerais, com os propostos em trabalhos precedentes visando estudar a interação entre o cobre e os ácidos acético e fórmico. The interaction mechanism between copper and propionic acid vapors is shown. Exposures were carried out to various pollutant concentrations and times. Cathodic scan, x-ray diffraction (XRD) and scanning electrode microscope (SEM) were used to quantify the degree of deterioration. The results obtained were explained by the following mechanism: A cuprite (Cu 2 O) layer covers the copper surface immediately; this compound in presence of adsorbed water is oxidized to tenorite (CuO). The hydration of the tenorite layer benefits the formation of a hydroxide compound such as CuO•xH 2 O. As the pollutant level is increased, insoluble basic propionate is formed (Cu(OH) x (CH 3 CH 2 COO) 2-x). Higher concentrations of propionic acid acidify the monolayers and a new compound Cu(CH 3 CH 2 COO) 2 •H 2 O begins to precipitate at low pH, this is the main constituent of the green olive patina formed under these conditions. This mechanism agrees, in general terms, with those proposed in previous works to study the interaction between copper and the acetic and formic acids.

Research paper thumbnail of Initial Atmospheric Corrosion of Copper Induced by Carboxylic Acids

Journal of The Electrochemical Society, 2007

The interaction of carboxylic acids with copper is a phenomenon found both outdoors and, more com... more The interaction of carboxylic acids with copper is a phenomenon found both outdoors and, more commonly, indoors. The influence on copper of some carboxylic acids (formic, acetic, propionic, and butyric) have so far been studied at concentrations levels at least three or four orders of magnitude higher than actual indoor conditions (< 20 ppb, volume parts per billion), and with only limited emphasis on any mechanistic approach. In this licentiate study a unique analytical setup has been successfully applied for in situ characterization and quantification of corrosion products formed during initial atmospheric corrosion of copper in the presence of acetic, formic or propionic acid. The setup is based on monitoring mass changes by the quartz crystal microbalance (QCM) and simultaneously identifying the chemical species by infrared reflection-absorption spectroscopy (IRAS). Post-analysis of corrosion products was performed by coulometric reduction (mass of copper (I) oxide formed), grazing incidence xray diffraction (phase identification) and atomic force microscopy (surface topography). The absolute amounts of mass of individual constituents in the corrosion products, mainly copper (I) oxide or cuprite, copper (II) carboxylate and water or hydroxyl groups, have been deduced in situ during exposure in 120 ppb of carboxylic acid concentration, 95% relative humidity and 20ºC. An overall result is the consistency of analytical information obtained. For copper (I) oxide the quantified data estimated from IRAS, QCM or coulomeric reduction agrees with a relative accuracy of 12 % or better. The interaction of copper with the carboxylic acids seems to follow two spatially separated main pathways. A proton-induced dissolution of cuprous ions followed by the formation of copper (I) oxide, and a carboxylate-induced dissolution followed by the formation of copper (II) carboxylate. The first pathway is initially very fast but levels off with a more uniform growth over the surface. This pathway dominates in acetic acid. The second pathway exhibits iii a more constant growth rate and localized growth, and dominates in formic acid. Propionic acid exhibits low rates for both pathways. The difference between the carboxylic acids with respect to both total corrosion rate and carboxylate-induced dissolution can be attributed to differences in acid dissociation constant and deposition velocity.

Research paper thumbnail of Quantitative In Situ Analysis of Initial Atmospheric Corrosion of Copper Induced by Acetic Acid

Journal of The Electrochemical Society, 2007

The interaction of carboxylic acids with copper is a phenomenon found both outdoors and, more com... more The interaction of carboxylic acids with copper is a phenomenon found both outdoors and, more commonly, indoors. The influence on copper of some carboxylic acids (formic, acetic, propionic, and butyric) have so far been studied at concentrations levels at least three or four orders of magnitude higher than actual indoor conditions (< 20 ppb, volume parts per billion), and with only limited emphasis on any mechanistic approach. In this licentiate study a unique analytical setup has been successfully applied for in situ characterization and quantification of corrosion products formed during initial atmospheric corrosion of copper in the presence of acetic, formic or propionic acid. The setup is based on monitoring mass changes by the quartz crystal microbalance (QCM) and simultaneously identifying the chemical species by infrared reflection-absorption spectroscopy (IRAS). Post-analysis of corrosion products was performed by coulometric reduction (mass of copper (I) oxide formed), grazing incidence xray diffraction (phase identification) and atomic force microscopy (surface topography). The absolute amounts of mass of individual constituents in the corrosion products, mainly copper (I) oxide or cuprite, copper (II) carboxylate and water or hydroxyl groups, have been deduced in situ during exposure in 120 ppb of carboxylic acid concentration, 95% relative humidity and 20ºC. An overall result is the consistency of analytical information obtained. For copper (I) oxide the quantified data estimated from IRAS, QCM or coulomeric reduction agrees with a relative accuracy of 12 % or better. The interaction of copper with the carboxylic acids seems to follow two spatially separated main pathways. A proton-induced dissolution of cuprous ions followed by the formation of copper (I) oxide, and a carboxylate-induced dissolution followed by the formation of copper (II) carboxylate. The first pathway is initially very fast but levels off with a more uniform growth over the surface. This pathway dominates in acetic acid. The second pathway exhibits iii a more constant growth rate and localized growth, and dominates in formic acid. Propionic acid exhibits low rates for both pathways. The difference between the carboxylic acids with respect to both total corrosion rate and carboxylate-induced dissolution can be attributed to differences in acid dissociation constant and deposition velocity.

Research paper thumbnail of GILDES Model Simulations of the Atmospheric Corrosion of Copper Induced by Low Concentrations of Carboxylic Acids

Journal of The Electrochemical Society, 2011

A computer simulation with a GILDES-based model using the COMSOL multiphysics software was perfor... more A computer simulation with a GILDES-based model using the COMSOL multiphysics software was performed for copper exposed to low concentrations of carboxylic acids in humidified air at room temperature. GILDES is a six-regime computer model (Gas, the Interface between gas and liquid, the Liquid, the Deposition layer, the Electrodic region near the surface and the Solid). The simulations were compared to previously published in-situ results for copper at the same conditions analysed by a quartz crystal microbalance (QCM) and infrared reflection absorption spectroscopy (IRAS). Experimental and calculated results agree with each other with respect to the effect of corrosion, showing formic acid as the most aggressive followed by acetic and propionic acid. This is supported by a higher ligand-and proton-promoted dissolution found in formic acid exposures, followed by acetic and propionic exposures. The dominating precipitated phases were Cu 2 O, Cu(OH) 2 , Cu(CH 3 COO) 2 • H 2 O, Cu(HCOO) 2 • 4H 2 O and Cu(CH 3 CH 2 COO) 2 • H 2 O. Besides Cu 2 O, the simulations suggest that the hydrated form of the respective carboxylates is the most likely compound to be formed in this type of atmospheres.

Research paper thumbnail of Electrochemical reduction modeling of copper oxides obtained during in situ and ex situ conditions in the presence of acetic acid

Electrochimica Acta, 2009

We used the potentiodynamic reduction technique to study the mechanism of copper oxide formation ... more We used the potentiodynamic reduction technique to study the mechanism of copper oxide formation in the presence of acetic acid. We performed all reductions under neutral conditions (0.1M KCl) until hydrogen evolution. We produced the copper oxides in an environment containing 0, 500, and 800ppb acetic acid at high relative humidity. We then compared experimental results between electrochemically produced oxide films obtained by imposing anodic potentials to copper specimens in several concentrations of pure acetic acid (1, 0.1, 0.01 and 0.001M). We found that, as the concentration of the acid decreases, the formation of the copper oxide (I) increases. We also found the same peaks in samples produced under the synthetic environment. We modeled the curves, taking into account the electrochemical reduction of copper (II) oxide (CuO), amorphous cuprite (Cu2O)am, intermediate cuprite (Cu2O)in, crystalline cuprite (Cu2O)cr, and hydrogen. These oxides have been previously detected in similar conditions. We found no evidence of copper carboxylate founding samples produced by the electrochemical method.

Research paper thumbnail of 2007 W.R. Whitney Award Lecture:Molecular In Situ Studies of Atmospheric Corrosion

CORROSION, 2007

Atmospheric corrosion involves chemical, electrochemical, and physical processes in three phases ... more Atmospheric corrosion involves chemical, electrochemical, and physical processes in three phases (solid, liquid, and gas) and two interfaces (solid∕ liquid and liquid∕ gas). Because of inherent experimental and conceptual difficulties, scientific efforts to characterize this ...

Research paper thumbnail of Indoor atmospheric corrosion of electronic materials in tropical-mountain environments

Corrosion Science, 2010

Indoor corrosion rate during one year exposure for carbon steel, copper, nickel, and tin was dete... more Indoor corrosion rate during one year exposure for carbon steel, copper, nickel, and tin was determined in three different atmospheres in Colombia. In addition, pollutants deposition rates and environmental parameters were also measured during indoor-outdoor conditions. The results show higher pollutant deposition in outdoor conditions, while inside metallic boxes the pollutant deposition significantly diminishes. No difference for relative humidity values was found between inside and outside measurements. For all samples, except nickel, the corrosion rate decrease with exposure time. The nature of corrosion products was found to be related to the exposure conditions.

Research paper thumbnail of Estudio del comportamiento mecánico de morteros modificados con fibras de aserrín bajo esfuerzos de compresión

Ingeniería y Desarrollo, 2019

En este artículo, se presenta un estudio sobre el comportamiento mecánico de morteros modificados... more En este artículo, se presenta un estudio sobre el comportamiento mecánico de morteros modificados con fibras de aserrín bajo cargas de compresión. Se estimó la densidad, resistencia a la compresión, y el módulo de elasticidad dinámico de morteros modificados con 0, 0,5, 1 y 3% en peso de fibra de aserrín. Los compuestos fueron evaluados luego de 7, 30 y 90 días de curado. Además, se utilizó microscopia electrónica de barrido (SEM) y espectroscopía de rayos X de energía dispersa (EDX) para caracterizar la morfología y encontrar la composición elemental tanto de las fibras como de la matriz de cemento. Los resultados muestran que a mayor porcentaje de aserrín, la resistencia, el módulo de elasticidad y la densidad disminuyen. Se sugiere utilizar hasta 1% de fibra de aserrín en morteros para evitar una reducción importante en las propiedades mecánicas de los morteros.