Ernesto Villar Cociña

Ernesto Villar Cociña
Universidad Central "Marta Abreu" de las Villas · Faculty of Mathematics, Physics and Computing

PhD Physical SCiences

About

85
Publications
19,282
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1,517
Citations
Citations since 2017
17 Research Items
838 Citations
2017201820192020202120222023050100150200
2017201820192020202120222023050100150200
2017201820192020202120222023050100150200
2017201820192020202120222023050100150200
Additional affiliations
July 1990 - present
Universidad Central "Marta Abreu" de las Villas
Position
  • Professor (Full)

Publications

Publications (85)
Poster
Full-text available
Las plantas invasoras proceden de ámbitos diferentes en los que se manifiestan de manera prolífica, crean comunidades resistentes que tapizan los suelos de manera indiscriminada y caótica. El marabú (Dichrostachys cinerea) es una de estas especies que, procedente de Europa, se ha instalado de una manera incontrolada en Cuba. La abundancia de esta p...
Article
Full-text available
Calcareous and siliceous CDW wastes from concrete and glass wastes when mixed in binary mixtures has been analyzed in this study. Fine CDW fractions (<5 mm) of different sorts are selected: siliceous waste (HsT), calcareous waste (HcG) and laminated glass waste. The binary mixtures HsT/glass and HcG/glass at mix-proportions of 1:1, 2:1 and 1:2, res...
Article
Full-text available
In this research work, the quantitative characterization of a binary blend comprised of two pozzolans (sugar cane straw (SCSA)–sugar cane bagasse ashes (SCBA), bamboo leaf ash (BLAsh)–SCBA and paper sludge (PS)–fly ash (FA)) taking into account the calculated values of the kinetic parameters of the reaction in the pozzolan/calcium hydroxide system...
Conference Paper
Full-text available
The water transport process in concretes is responsible for the deterioration of concretes and their reinforcement structures, causing a considerable decrease in their performance in countries with a maritime climate such as Cuba. It is known that pozzolanic additions in their reaction with calcium hydroxide (produced in the cement and concrete hyd...
Article
Full-text available
This study analysed the fine particle (<5 mm) waste generated during siliceous or calcareous (depending on the composition of the original aggregate) concrete waste crushing. In the absence of industrial applications, such waste is amassed in open-air stockpiles on construction and demolition wastes (CDW) management plant grounds. The aim pursued w...
Article
Full-text available
Silica fume is the most performing siliceous product among the pozzolanic materials. This is mainly related to his high content (around of 90%) of amorphous silica. However, this residue has a high cost and the quantities available are limited. This limits its use in the modern construction industry, particularly in developing countries. For this r...
Article
Full-text available
The results of the characterization of the Sugarcane Bagasse Ash from the co-generator boiler (SCBAB) of a Cuban sugar mill, obtained in previous works are offered. Aluminum Matrix composites (AMCs) samples were fabricated employing powder metallurgy technique. The comparative study of the Al-SCBAB composite with respect to the non-reinforced matri...
Article
Full-text available
At present, there is growing interest in the investigation of economic options for the development of aluminum matrix composites. In this context, the characterization of a cane bagasse ash from a Cuban clay, both in its natural state and after being calcined for 4 h at 1000C, for its possible use as a reinforcement material in matrix composites o...
Article
In the context of cement industry sustainability and socio-economic development, one of the primary objectives of the circular economy is the use of industrial waste as a supplementary cementitious material in the manufacture of future eco-efficient binders. This paper reports a first-time study of the effect of large proportions of the activated c...
Article
Full-text available
The paper presents a study of the pozzolanic activity of Cuban bamboo leaf ash. To evaluate the pozzolanic activity a conductometric method was used, which is based on the measurement of variation in electrical conductivity of a bamboo leaf ash (BLAsh)/lime solution with reaction time. Later, the kinetic parameters (in particular, the reaction rate...
Chapter
Contemporary society is faced with any number of pressing problems, not least of which is the generation of waste and industrial by-products. Technological progress is nonetheless favoring ever more efficient, sustainable, and eco-friendly industrial development. In construction in particular, it has been standard practice for many decades to use i...
Data
En el presente artículo se estudia la relación cuasilineal existente entre el índice de permeabilidad y el coeficiente de difusión de humedad en cuatro mezclas autofraguantes para machos de fundición que emplean silicato sódico y proceso CO2. Con este propósito se ejecutan ensayos de permeabilidad y empleando técnicas gravimétricas se investiga la...
Article
Due to economical and sustainable issues there is growing interest in investigating agro-industrial wastes as alternative route for future eco-efficient and sustainable pozzolans. The generation of ashes from cogeneration processes in which sugar cane wastes are used as biomass, involves significant environmental, social and health problems when th...
Poster
Full-text available
Se ha descrito como con el empleo de cenizas puzolánicas, obtenidas a partir de la combustión de materiales de desechos tales como paja y bagazo de caña de azúcar, cáscara de arroz, hojas de bambú y otros, en sustitución de hasta un 20 % del cemento Portland en las mezclas para hormigones, se puede disminuir el impacto medioambiental y mantener en...
Poster
Full-text available
En la actualidad existe un interés creciente en la investigación de opciones económicas para el desarrollo de materiales compuestos de matriz de aluminio [1-2]. En este contexto se presentan la caracterización de una ceniza de bagazo de caña y de una arcilla cubana, tanto en su estado natural como después de ser calcinada durante 4 h a 1 000 °C, pa...
Article
Full-text available
Se evalúa el comportamiento de mezclas de moldeo para machos de fundición expuestas a intemperies de altas humedades relativas. En las mezclas analizadas se obtuvo la relación entre la resistencia mecánica a la compresión y el incremento relativo en peso húmedo. La dependencia entre ambos parámetros, de tipo exponencial, fue corroborada por estimac...
Article
This paper presents for the first time the influence of mixing different thermally activated paper sludges (APS) and fly ash (FA) on the pozzolanic reaction kinetics in APS–FA–Ca(OH)2 systems as a previous step to manufacture the future commercial ternary blended cements. In this study, two paper sludge wastes from different origins and activation...
Article
Full-text available
Elephant grass ash (EGA) was produced at 700 degrees C, with two different treatments: hot water (EGAhw) or acid solution (EGAas). The efficiency of the treatments at removing the potassium oxide was evaluated with the aim of using the EGA as a pozzolanic mineral addition for cement-based composites. Characterizations were carried out by X-ray fluo...
Article
Full-text available
The paper presents a study of the pozzolanic reaction kinetics between calcium hydroxide and sugar cane bagasse ash (SCBAB) from the boiler of a sugar factory. A pozzolanic activity method (conductometric method) based on measurement of the electrical conductivity of the SCBAB/calcium hydroxide solution as the reaction proceeds is applied and the k...
Article
Full-text available
Zeolites generally show pozzolanic activity due to their structural characteristics. The utilisation of pozzolans as additions to cements results in added technical advantages of the construction materials. In this study, the pozzolanic activity of a thermally treated natural mordenite-type zeolite from the Palmarito open-air deposit (Cuba) was eva...
Article
Full-text available
Resumen: En el presente artículo se estudia la relación cuasilineal existente entre el índice de permeabilidad y el coeficiente de difusión de humedad en cuatro mezclas autofraguantes para machos de fundición que emplean silicato sódico y proceso CO2. Con este propósito se ejecutan ensayos de permeabilidad y empleando técnicas gravimétricas se inve...
Article
For proper management of wastes and their possible recycling as raw materials, complete characterization of the materials is necessary to evaluate the main scientific aspects and potential applications. The current paper presents a detailed scientific study of different Brazilian sugar cane bagasse ashes from the cogeneration industry as alternativ...
Article
Natural zeolite is a type of mineralogical material containing large quantities of reactive SiO2 and Al2O3. These materials have been used in the cement industry as a supplementary cementing material. Like other pozzolanic materials the zeolite contributes to improve the mortar and concrete performances mainly through the pozzolanic reaction with c...
Article
Full-text available
The paper presents a characterization and study of the pozzolanic behavior between calcium hydroxide (CH) and bamboo leaf ash (BLAsh), which was obtained by calcining bamboo leaves at 600 C for 2 h in a laboratory electric furnace. To evaluate the pozzolanic behavior the conductometric method was used, which is based on the measurement of the elect...
Article
Loessic sediments, widely distributed in the Argentine plains, are composed mainly of silt particles, transported and accumulated by wind during Quaternary geological times. At that period an important aeolian process took place together with explosive volcanic activity in the western area of the country. The chemical and mineralogical composition...
Article
It is well known that the transformation of some clay minerals into pozzolanic materials for the manufacture of Portland cements depends on the activation conditions. In the current paper, a study was carried out to evaluate the effect of activation temperature in the range of 500–7008C on the characteristics of thermally activated clay wastes (ACW...
Article
Full-text available
The kinetic study of the tempering reactions of a low-alloy steel (AISI 1050) was carried out through non-isothermal dilatometry. The kinetic parameters of the first and third stages on tempering (here referred to as processes I and II) are calculated by procedures which assume that the nucleation and growth reactions obey a Kolmogorov–Johnson–Mehl...
Article
A natural mordenite-type zeolite from Palmarito ore deposit (Cuba) was studied along the reaction with a saturated lime solution at 40 C in order to determine its pozzolanic activity. Ca(OH)2 is an alkali activating agent that simulates the release of lime from ordinary portland cement during the hydration reaction. Formation of C–S–H-like phases w...
Article
Full-text available
In this paper is described the investigation process and development of a new mixture for foundry cores, in which a factorial complete at two levels experimental design for mixtures with relationships between the components and an operation variable is used. The mixture that is developed uses the traditional process sodium silicate - CO2 and a new...
Article
Full-text available
In this paper is described the investigation process and development of a new mixture for foundry cores, in which a factorial complete at two levels experimental design for mixtures with relationships between the components and an operation variable is used. The mixture that is developed uses the traditional process sodium silicate - CO2 and a new...
Article
Full-text available
In this paper a study of calcining conditions on the microstructural features of sugar cane waste ash (SCWA) is carried out. For this purpose, some microparticles (<90 lm) of sugar cane straw ash and sugar cane bagasse ash of samples calcined at 800 C and 1000 are studied by combining the bright field and the dark field images with the electron dif...
Article
Full-text available
This paper presents a study of the pozzolanic reaction kinetics between calcium hydroxide and a mixture of sugar cane bagasse with 20 and 30% of clay, burned at 800 and 10008C (SCBCA) by electrical conductivity measurements. A kinetic–diffusive model produced in previous studies by some of the authors was used. The model was fitted to the experimen...
Article
Full-text available
A natural mordenite-type zeolite from Palmarito ore deposit (Cuba) was studied along the reaction with a satd. lime soln. at 40 °C in order to det. its pozzolanic activity. Ca(OH)2 is an alkali activating agent that simulates the release of lime from ordinary portland cement during the hydration reaction. Formation of C-S-H-like phases with very l...
Article
Full-text available
This paper proposes a kinetic-diffusive model that allows for determination of pozzolanic activity as related to optimum calcining temperature on the activation of wastes from sugar cane industries and their use as pozzolanic material. Research based on the reaction kinetics between lime (calcium hydroxide [CH]), sugar cane straw ash (SCSA), and su...
Conference Paper
Full-text available
The paper presents a study of the pozzolanic reaction kinetics between calcium hydroxide (CH) and bamboo leaf ash, calcined at 600ºC (BLAsh). A pozzolanic activity method (conductometric method) based on the measurement of the electrical conductivity of the BLAsh/CH solution as the reaction proceeds is applied and latter on the kinetic parameters a...
Conference Paper
Athermic analyses for the kinetic study of the reactions in the solid state are preferred because they consume much less experimental work time than the isothermal tests, and lead to more accurate calculations of the energies of activation of reactions that have occurred. In the present work are required conditions where you can apply the equation...
Article
This paper reports on the influence of calcining temperature (800 and 1000 degrees C) on the pozzolanic activation of sugar cane straw (SCS). The reaction kinetics of SCS ash-lime mixtures were inferred from physicochemical characteristics (X-ray diffraction patterns and thermogravimetry analysis. The fitting of a kinetic-diffusive model to the exp...
Article
Full-text available
The present paper describes a study of the influence of calcining temperature (800 and 1000°C) on the activation of sugar-cane bagasse. The reaction kinetics in a bagasse ash-lime system were investigated by means of X-ray diffraction patterns and thermogravimetric curves. The kinetic parameters were calculated by applying a kineticdiffusive model....
Article
The present paper describes a study of the influence of calcining temperature (800 and 10008C) on the activation of sugar-cane bagasse. The reaction kinetics in a bagasse ash–lime system were investigated by means of X-ray diffraction patterns and thermogravimetric curves. The kinetic parameters were calculated by applying a kinetic– diffusive mode...
Conference Paper
Full-text available
We study the structural characteristics of some metallic coatings using the arc spraying process. In order to save and to reduce the coating materials, it was analyzed the influence of a Cu-base alloy, as bond coat, on the metallic coatings sprayed with the standard arc spraying parameters. The results show that as the bond coat has a higher therma...
Article
The paper presents a comparative study in which different kinetic models were applied to describe the reaction kinetics of a mixture of sugar cane straw with 20 and 30% of clay, burned at 800 and 10008C (SCSCA), and hydrated lime [calcium hydroxide (CH)]. Classical models, such as the Jander, Jander Modified and Zuravlev models were applied. These...
Conference Paper
Full-text available
The kinetics of precipitation of the primary and independent carbides during tempering of a low-alloy steel are characterized by the application of the Kinetic Theory of the Overlapping Phase Transformations(KTOPT). It is based on the Avrami model and considers two simultaneous precipitation processes. The present set-up allows us to calculate the...
Article
The reaction kinetics of a mixture of sugar cane straw with 20% and 30% of clay burned at 800 and 1000 °C and lime (calcium hydroxide) is studied. A direct method (accelerated chemical method) based on the measurement of the amount of lime reacted as the reaction proceeds is applied. A kinetic–diffusive model published in a previous paper by some a...
Article
Full-text available
In this paper three core moulding mixtures with Sodium Silicate and CO2 process, employing different unbinders studied. The optimum composition for each mixture is found with a fractional factorial design which use relations of components and process variables (1/3 33). The compression strength at 24 hours and the work to remove the core are select...
Article
A kinetic-diffusive model proposed by the authors in previous papers to describe pozzolanic reaction kinetics in sugar cane straw-clay ash (SCSCA)/calcium hydroxide (CH) systems is validated in this study. Two different methods (direct and indirect) for determining pozzolanic activity were applied and their effect on pozzolanic reaction rate kineti...
Article
A kinetic-diffusive model proposed by the authors in previous papers to describe pozzolanic reaction kinetics in sugar cane straw-clay ash (SCSCA)/calcium hydroxide (CH) systems is validated in this study. Two different methods (direct and indirect) for determining pozzolanic activity were applied and their effect on pozzolanic reaction rate kineti...
Article
Full-text available
In this paper the behavior of the moisture sorption-desorption by porous solid isdiscussed. Employing the diffusion theory the moisture transference is formulated for the permeable plane sheets configuration. The problem is solved for the initially dry solid that remains at environments with controlled relative humidity and temperature. It is demon...
Article
We study the kinetics of absorption of water in Portland cement concretes added with 60, 70 and 80% of granulated blast furnace slag (GGBS) cured in water and at open air and preheated at 50 and 100oC. A mathematical model is presented that allows describing the process not only in early ages where the capillary sorption is predominant but also for...
Article
Full-text available
The deviation of the Avrami slope, using the propagation of the uncertainty, is bigger at small fraction transformed values than at high ones. The minimum deviation of the Avrami slope is obtained at the fraction transformed value equal to 0.632, independently of the uncertainty value in the fraction transformed.
Article
The reaction kinetics of a mixture of sugar cane straw with 20% and 30% of clay burned at 800 and 1000 ^oC and lime (calcium hydroxide) is studied. A direct method (accelerated chemical method) based on the measurement of the amount of lime...
Article
Full-text available
emplean diferentes desarenantes, las que posteriormente son sopladas con gas carbónico. La composición adecuada para cada tipo de mezcla se determina mediante un diseño factorial incompleto con relaciones y variable de operación (1/3 33). Como variables de respuestas se seleccionaron la resistencia a la compresión a las 24 horas y la desmoldeabilid...
Article
This paper discusses the characterization of sugar industry solid waste as pozzolanic materials. Research on the reaction kinetics between calcium hydroxide (CH) and sugar cane straw ash and bagasse ash with 20% and 30% clay, calcined at 800 °C and 1000 °C, is described. A simple experimental technique was utilized based on the electrical conductiv...
Article
Full-text available
Often a number of precipitation processes in steels and alloys occur simultaneously (they have the same origin in time) albeit at different rates. Consequently, isothermal transformations are accompanied, in this case, by the occurrence of second processes of precipitation that influence the changes of the macroscopic parameter chosen for the kinet...
Article
Full-text available
The kinetics of the pozzolanic reaction between lime (calcium hydroxide) and sugar cane straw ash (SCSA) with 20% and 30% of clay burned at 800 and 1000 °C is studied. A simple experimental technique was used in which the conductivity is the experimental variable. For correlating the conductivity with the concentration of calcium hydroxide (CH), a...
Conference Paper
This paper discusses the characterization of sugar industry solid waste as pozzolanic materials. Research on the reaction kinetics between calcium hydroxide (CH) and sugar cane straw ash and bagasse ash with 20% and 30% clay, calcined at 800 0C and 1000 0C, is described. A simple experimental technique was utilized based on the electrical conductiv...
Article
Full-text available
Often a number of precipitation processes in steels and alloys occur simultaneously (they have the same origin in time) albeit at different rates. Consequently, isothermic transformations are accompanied, in this case, by the occurrence of second processes of precipitation that influence the changes of the macroscopic parameter chosen for the kinet...
Article
Full-text available
We study the kinetics of absorption of water in portland cement mortars added with 60, 70 and 80% of granulated blast furnace slag (GGBS or Slag) cured in water and at open air and preheating at 50 and 100 C.A mathematical model is presented that allows describing the process not only in early ages where the capillary sorption is predominant but al...
Article
Full-text available
The moisture diffusion in molding mixtures employing in foundry processes is described. Using gravimetric techniques the humectation kinetic behavior of different types of molding mixtures for foundry cores were registered. The mixture higroscopicity is compared using the porcentual increase in wet mass. The kinetic study is ending with the calcula...
Article
Full-text available
The moisture diffusion in molding mixtures employing in foundry processes is described. Using gravimetric techniques the humectation kinetic behavior of different types of molding mixtures for foundry cores were registered. The mixture I higroscopicity is compared using the porcentual increase in wet mass. The kinetic study is ending with the calcu...
Article
Full-text available
Using gravimetric methods the humectation kinetic behavior of two autoforge mixtures with sodium silicate and CO2 process for foundry cores(with similar characteristic) that use discarded raw sugar as agent that help to remove cores from castings were registered. The influence of the content of sugar in the hygroscope properties of these mixtures w...