Asphalt rubber mixtures with warm mix asphalt additives

En los últimos años, debido a la creciente preocupación por el calentamiento global y el cambio climático, uno de los retos más importantes a los que se enfrenta nuestra sociedad es el uso eficiente y económico de energía así como la necesidad correspondiente de reducir los gases de efecto invernadero (GEI). Las tecnologías de mezclas semicalientes se han convertido en un nuevo e importante tema de investigación en el campo de los materiales para pavimentos ya que ofrece una solución potencial para la reducción del consumo energético y las emisiones de GEI durante la producción y puesta en obra de las mezclas bituminosas. Por otro lado, los pavimentos que contienen polvo de caucho procedente de neumático fuera de uso, al hacer uso productos de desecho, ahorran energía y recursos naturales. Estos pavimentos ofrecen una resistencia mejorada a la formación de roderas, a la fatiga y a la fisuración térmica, reducen los costes de mantenimiento y el ruido del tráfico así como prolongan la vida útil del pavimento. Sin embargo, estas mezclas presentan un importante inconveniente: la temperatura de fabricación se debe aumentar en comparación con las mezclas asfálticas convencionales, ya que la incorporación de caucho aumenta la viscosidad del ligante y, por lo tanto, se producen mayores cantidades de emisiones de GEI. En la presente Tesis, la tecnología de mezclas semicalientes con aditivos orgánicos (Sasobit, Asphaltan A, Asphaltan B, Licomont) se incorporó a la de betunes de alta viscosidad modificados con caucho (15% y 20% de caucho) con la finalidad de dar una solución a los inconvenientes de mezclas con caucho gracias a la utilización de aditivos reductores de la viscosidad. Para este fin, se estudió si sería posible obtener una producción más sostenible de mezclas con betunes de alto contenido en caucho sin afectar significativamente su nivel de rendimiento mecánico. La metodología aplicada para evaluar y comparar las características de las mezclas consistió en la realización de una serie de ensayos de laboratorio para betunes y mezclas con caucho y con aditivos de mezclas semicalientes y de un análisis del ciclo de vida híbrido de la producción de mezclas semicalientes teniendo en cuenta la papel del aditivo en la cadena de suministro con el fin de cuantificar con precisión los beneficios de esta tecnología. Los resultados del estudio indicaron que la incorporación de los aditivos permite reducir la viscosidad de los ligantes y, en consecuencia, las temperaturas de producción y de compactación de las mezclas. Por otro lado, aunque la adición de caucho mejoró significativamente el comportamiento mecánico de los ligantes a baja temperatura reduciendo la susceptibilidad al fenómeno de fisuración térmica, la adición de las ceras aumentó ligeramente la rigidez. Los resultados del estudio reológico mostraron que la adición de porcentajes crecientes de caucho mejoraban la resistencia del pavimento con respecto a la resistencia a la deformación permanente a altas temperaturas y a la fisuración térmica a bajas temperaturas. Además, se observó que los aditivos mejoran la resistencia a roderas y la elasticidad del pavimento al aumentar el módulo complejo a altas temperaturas y al disminuir del ángulo de fase. Por otra parte, el estudio reológico confirmó que los aditivos estudiados aumentan ligeramente la rigidez a bajas temperaturas. Los ensayos de fluencia llevados a cabo con el reómetro demostraron una vez más la mejora en la elasticidad y en la resistencia a la deformación permanente dada por la adición de las ceras. El estudio de mezclas con caucho y aditivos de mezclas semicalientes llevado a cabo demostró que las temperaturas de producción/compactación se pueden disminuir, que las mezclas no experimentarían escurrimiento, que los aditivos no cambian significativamente la resistencia conservada y que cumplen la sensibilidad al agua exigida. Además, los aditivos aumentaron el módulo de rigidez en algunos casos y mejoraron significativamente la resistencia a la deformación permanente. Asimismo, a excepción de uno de los aditivos, las mezclas con ceras tenían la misma o mayor resistencia a la fatiga en comparación con la mezcla control. Los resultados del análisis de ciclo de vida híbrido mostraron que la tecnología de mezclas semicalientes es capaz de ahorrar significativamente energía y reducir las emisiones de GEI, hasta un 18% y 20% respectivamente, en comparación con las mezclas de control. Sin embargo, en algunos de los casos estudiados, debido a la presencia de la cera, la temperatura de fabricación debe reducirse en un promedio de 8 ºC antes de que los beneficios de la reducción de emisiones y el consumo de combustible puedan ser obtenidos. Los principales sectores contribuyentes a los impactos ambientales generados en la fabricación de mezclas semicalientes fueron el sector de los combustibles, el de la minería y el de la construcción. Due to growing concerns over global warming and climate change in recent years, one of the most important challenges facing our society is the efficient and economic use of energy, and with it, the corresponding need to reduce greenhouse gas (GHG) emissions. The Warm Mix Asphalt (WMA) technology has become an important new research topic in the field of pavement materials as it offers a potential solution for the reduction of energy consumption and GHG emissions during the production and placement of asphalt mixtures. On the other hand, pavements containing crumb-rubber modified (CRM) binders save energy and natural resources by making use of waste products. These pavements offer an improved resistance to rutting, fatigue and thermal cracking; reduce traffic noise and maintenance costs and prolong pavement life. These mixtures, however, present one major drawback: the manufacturing temperature is higher compared to conventional asphalt mixtures as the rubber lends greater viscosity to the binder and, therefore, larger amounts of GHG emissions are produced. In this dissertation the WMA technology with organic additives (Sasobit, Asphaltan A, Asphaltan B and Licomont) was applied to CRM binders (15% and 20% of rubber) in order to offer a solution to the drawbacks of asphalt rubber (AR) mixtures thanks to the use of fluidifying additives. For this purpose, this study sought to determine if a more sustainable production of AR mixtures could be obtained without significantly affecting their level of mechanical performance. The methodology applied in order to evaluate and compare the performance of the mixtures consisted of carrying out several laboratory tests for the CRM binders and AR mixtures with WMA additives (AR-WMA mixtures) and a hybrid input-output-based life cycle assessment (hLCA) of the production of WMA. The results of the study indicated that the incorporation of the organic additives were able to reduce the viscosity of the binders and, consequently, the production and compaction temperatures. On the other hand, although the addition of rubber significantly improved the mechanical behaviour of the binders at low temperatures reducing the susceptibility to thermal cracking phenomena, the addition of the waxes slightly increased the stiffness. Master curves showed that the addition of increasing percentages of rubber improved the resistance of the pavement regarding both resistance to permanent deformation at high temperatures and thermal cracking at low temperatures. In addition, the waxes improved the rutting resistance and the elasticity as they increased the complex modulus at high temperatures and decreased the phase angle. Moreover, master curves also attest that the WMA additives studied increase the stiffness at low temperatures. The creep tests carried out proved once again the improvement in the elasticity and in the resistance to permanent deformation given by the addition of the waxes. The AR-WMA mixtures studied have shown that the production/compaction temperatures can be decreased, that the mixtures would not experience binder drainage, that the additives did not significantly change the retained resistance and fulfilled the water sensitivity required. Furthermore, the additives increased the stiffness modulus in some cases and significantly improved the permanent deformation resistance. Except for one of the additives, the waxes had the same or higher fatigue resistance compared to the control mixture. The results of the hLCA demonstrated that the WMA technology is able to significantly save energy and reduce GHG emissions, up to 18% and 20%, respectively, compared to the control mixtures. However, in some of the case studies, due to the presence of wax, the manufacturing temperature at the asphalt plant must be reduced by an average of 8ºC before the benefits of reduced emissions and fuel usage can be obtained. The results regarding the overall impacts generated using a detailed production layer decomposition indicated that fuel, mining and construction sectors are the main contributors to the environmental impacts of manufacturing WMA mixtures.

Values of the deformation modulus of soil at different ways of determining this amount

In accordance with Russian, Kazakh and European building regulations, the deformation modulus of soil should be determined in the laboratory and also apply in situ soil tests on the stages of engineering geology prospecting. In this paper we present data on the determination and adjustment of the deformation characteristics at different stages of construction

Modal analysis of buildings : quantification of uncertainties and model updating

Una estructura vibra con la suma de sus infinitos modos de vibración, definidos por sus parámetros modales (frecuencias naturales, formas modales y coeficientes de amortiguamiento). Estos parámetros se pueden identificar a través del Análisis Modal Operacional (OMA). Así, un equipo de investigación de la Universidad Politécnica de Madrid ha identificado las propiedades modales de un edificio de hormigón armado en Madrid con el método Identificación de los sub-espacios estocásticos (SSI). Para completar el estudio dinámico de este edificio, se ha desarrollado un modelo de elementos finitos (FE) de este edificio de 19 plantas. Este modelo se ha calibrado a partir de su comportamiento dinámico obtenido experimentalmente a través del OMA. Los objetivos de esta tesis son; (i) identificar la estructura con varios métodos de SSI y el uso de diferentes ventanas de tiempo de tal manera que se cuantifican incertidumbres de los parámetros modales debidos al proceso de estimación, (ii) desarrollar FEM de este edificio y calibrar este modelo a partir de su comportamiento dinámico, y (iii) valorar la bondad del modelo. Los parámetros modales utilizados en esta calibración han sido; espesor de las losas, densidades de los materiales, módulos de elasticidad, dimensiones de las columnas y las condiciones de contorno de la cimentación. Se ha visto que el modelo actualizado representa el comportamiento dinámico de la estructura con una buena precisión. Por lo tanto, este modelo puede utilizarse dentro de un sistema de monitorización estructural (SHM) y para la detección de daños. En el futuro, podrá estudiar la influencia de los agentes medioambientales, tales como la temperatura o el viento, en los parámetros modales. A structure vibrates according to the sum of its vibration modes, defined by their modal parameters (natural frequencies, damping ratios and modal shapes). These parameters can be identified through Operational Modal Analysis (OMA). Thus, a research team of the Technical University of Madrid has identified the modal properties of a reinforced-concrete-frame building in Madrid using the Stochastic Subspace Identification (SSI) method and a time domain technique for the OMA. To complete the dynamic study of this building, a finite element model (FE) of this 19-floor building has been developed throughout this thesis. This model has been updated from its dynamic behavior identified by the OMA. The objectives of this thesis are to; (i) identify the structure with several SSI methods and using different time blocks in such a way that uncertainties due to the modal parameter estimation are quantified, (ii) develop a FEM of this building and tune this model from its dynamic behavior, and (iii) Assess the quality of the model, the modal parameters used in this updating process have been; thickness of slabs, material densities, modulus of elasticity, column dimensions and foundation boundary conditions. It has been shown that the final updated model represents the structure with a very good accuracy. Thus, this model might be used within a structural health monitoring framework (SHM). The study of the influence of changing environmental factors (such as temperature or wind) on the model parameters might be considered as a future work.

Influencia de la adición de nanosílice y microsílice en el comportamiento mecánico, microestructural y durable de un hormigón autocompactante

Desde mediados de la década de los 80 se está investigando sobre el hormigón autocompactante. Cada día, su uso en el mundo de la construcción es más común debido a sus numerosas ventajas como su excelente fluidez ya que puede fluir bajo su propio peso y llenar encofrados con formas complicadas y muy armados sin necesidad de compactaciones internas o externas. Por otra parte, la búsqueda de materiales más resistentes y duraderos, ha dado lugar a la incorporación de adiciones en materiales a base de cemento. En las últimas dos décadas, los ensayos con los nanomateriales, ha experimentado un gran aumento. Los resultados hasta ahora obtenidos pueden asumir no sólo un aumento en la resistencia de estos materiales, pero un cambio es su funcionalidad. Estas nanopartículas, concretamente la nanosílice, no sólo mejoran sus propiedades mecánicas y especialmente sus propiedades durables, sino que pueden implicar un cambio sustancial en las condiciones de uso y en su ciclo de vida. Este trabajo tiene como principal objetivo el estudio de las propiedades mecánicas, características microestructurales y durables de un hormigón autocompactante cuando se le agrega como adición nanosílice, microsílice y mezcla binarias de ambas, como adición al cemento. Para ello se han realizado 10 mezclas de hormigón. Se utilizó como referencia un hormigón autocompactante obtenido con cemento, caliza, árido, aditivo modificador de viscosidad Se han fabricado tres hormigones con la misma dosificación pero con diferentes contenidos de nanosílice. 2,5%, 5% y 7,5% Tres dosificaciones con adición de microsílice 2,5%, 5% y 7,5% y las tres restantes con mezclas binarias de nanosílice y microsílice con respectivamente2,5%-2,5%, 5%-2,5% y 2,5%-5%, sobre el peso del cemento. El contenido de superplastificante se modificó para conseguir las características de autocompactabilidad. Para observar los efectos de las adiciones añadidas al hormigón, se realiza una extensa campaña experimental. En ella se evaluaron en primer lugar, las características de autocompactabilidad del material en estado fresco, mediante los ensayos prescritos en la Instrucción Española del hormigón estructural EHE 08. Las propiedades mecánicas fueron evaluadas con ensayos de resistencia a compresión, resistencia a tracción indirecta y módulo de elasticidad. Las características microestructurales fueron analizadas mediante porosimetría por intrusión de mercurio, el análisis termogravimétrico y la microscopía electrónica de barrido. Para el estudio de la capacidad durable de las mezclas se realizaron ensayos de resistividad eléctrica, migración de cloruros, difusión de cloruros, carbonatación acelerada, absorción capilar y resistencia al hielo-deshielo. Los resultados ponen de manifiesto que la acción de las adiciones genera mejoras en las propiedades resistentes del material. Así, la adición de nanosílice proporciona mayores resistencias a compresión que la microsílice, sin embargo las mezclas binarias con bajas proporciones de adición producen mayores resistencias. Por otra parte, se observó mediante la determinación de las relaciones de gel/portlandita, que las mezclas que contienen nanosílice tienen una mayor actividad puzolánica que las que contienen microsílice. En las mezclas binarias se obtuvo como resultado que mientras mayor es el contenido de nanosílice en la mezcla mayor es la actividad puzolánica. Unido a lo anteriormente expuesto, el estudio de la porosidad da como resultado que la adición de nanosílice genera un refinamiento del tamaño de los poros mientras que la adición de microsílice disminuye la cantidad de los mismos sin variar el tamaño de poro medio. Por su parte, en las micrografías, se visualizó la formación de cristales procedentes de la hidratación del cemento. En ellas, se pudo observar, que al adicionar nanosílice, la velocidad de hidratación aumenta al aumentar la formación de monosulfoaluminatos con escasa presencia de etringita. Mientras que en las mezclas con adición de microsílice se observan mayor cantidad de cristales de etringita, lo que confirma que la velocidad de hidratación en estos últimos fue menor. Mediante el estudio de los resultados de las pruebas de durabilidad, se observó que no hay diferencias significativas entre el coeficiente de migración de cloruros y el coeficiente de difusión de cloruros en hormigones con adición de nano o microsílice. Aunque este coeficiente es ligeramente menor en mezclas con adición de microsílice. Sin embargo, en las mezclas binarias de ambas adiciones se obtuvo valores de los coeficientes de difusión o migración de cloruros inferiores a los obtenidos en mezclas con una única adición. Esto se evidencia en los resultados de las pruebas de resistividad eléctrica, de difusión de cloruros y de migración de cloruros. Esto puede ser debido a la suma de los efectos que producen el nano y micro adiciones en la porosidad. El resultado mostró que nanosílice tiene un papel importante en la reducción de los poros y la microsílice disminuye el volumen total de ellos. Esto permite definir la vida útil de estos hormigones a valores muy superiores a los exigidos por la EHE-08, por lo que es posible reducir, de forma notable, el recubrimiento exigido en ambiente de alta agresividad asegurando un buen comportamiento en servicio. Por otra parte, la pérdida de masa debido a los ciclos de congelación-descongelación es significativamente menor en los hormigones que contienen nanosílice que los que contienen microsílice. Este resultado está de acuerdo con el ensayo de absorción capilar. De manera general, se puede concluir que son las mezclas binarias y más concretamente la mezcla con un 5% de nanosílice y 2,5% de microsílice la que presenta los mejores resultados tanto en su comportamiento resistente con en su comportamiento durable. Esto puede ser debido a que en estas mezclas la nanosílice se comporta como un núcleo de activación de las reacciones puzolánicas rodeado de partículas de mayor tamaño. Además, el extraordinario comportamiento durable puede deberse también a la continuidad en la curva granulométrica por la existencia de la microsílice, el filler calizo, el cemento, la arena y la gravilla con tamaños de partículas que garantice mezclas muy compactas que presentan elevadas prestaciones. Since the middle of the decade of the 80 is being investigated about self-consolidating concrete. Every day, its use in the world of construction is more common due to their numerous advantages as its excellent fluidity such that it can flow under its own weight and fill formworks with complicated shapes and congested reinforcement without need for internal or external compactions. Moreover, the search for more resistant and durable materials, has led to the incorporation of additions to cement-based materials. In the last two decades, trials with nanomaterials, has experienced a large increase. The results so far obtained can assume not only an increase in the resistance of these materials but a change is its functionality. These nano particles, particularly the nano silica, not only improve their mechanical properties and especially its durable properties, but that may imply a substantial change in the conditions of use and in their life cycle. This work has as its main objective the study of the mechanical properties, the microstructural characteristics and durability capacity in one self-compacting concrete, when added as addition to cement: nano silica, micro silica o binary mixtures of both. To this effect, 10 concrete mixes have been made. As reference one with a certain amount of cement, limestone filler, viscosity modifying additive and water/binder relation. Furthermore they were manufactured with the same dosage three mix with addition of 2.5%, 5% and 7.5% of nano silica by weight of cement. Other three with 2.5%, 5% and 7.5% of micro silica and the remaining three with binary mixtures of 2.5%-2.5%, 5%-2.5% and 2.5%-5% of silica nano-micro silica respectively, b weight of cement, varying only the amount of superplasticizer to obtain concrete with characteristics of self-compactability. To observe the effects of the additions added to the concrete, an extensive experimental campaign was performed. It assessed, first, the characteristics of self-compactability of fresh material through the tests prescribed in the Spanish Structural Instruction Concrete EHE 08. The mechanical properties were evaluated by compression strength tests, indirect tensile strength and modulus of elasticity. The microstructural properties were analyzed by mercury intrusion porosimetry, thermogravimetric analysis and scanning electron microscopy. To study the durability, were performed electrical resistivity tests, migration and diffusion of chlorides, accelerated carbonation, capillary suction and resistance to freeze-thaw cycles. The results show that the action of the additions generates improvements in the strength properties of the material. Specifically, the addition of nano silica provides greater resistance to compression that the mix with micro silica, however binary mixtures with low addition rates generate higher strengths. Moreover, it was observed by determining relationships gel/portlandite, that the pozzolanic activity in the mixtures with nano silica was higher than in the mixtures with micro silica. In binary mixtures it was found that the highest content of nano silica in the mix is the one with the highest pozzolanic activity. Together with the foregoing, the study of the porosity results in the mixture with addition of nano silica generates a refinement of pore size while adding micro silica decreases the amount thereof without changing the average pore size. On the other hand, in the micrographs, the formation of crystals of cement hydration was visualized. In them, it was observed that by adding nano silica, the speed of hydration increases with increasing formation monosulfoaluminatos with scarce presence of ettringite. While in mixtures with addition of micro silica, ettringite crystals are observed, confirming that the hydration speed was lower in these mixtures. By studying the results of durability testing, it observed that no significant differences between the coefficient of migration of chlorides and coefficient of diffusion of chlorides in concretes with addition of nano or micro silica. Although this coefficient is slightly lower in mixtures with addition of micro silica. However, in binary mixtures of both additions was obtained values of coefficients of difusion o migration of chlorides lower than those obtained in mixtures with one of the additions. This is evidenced by the results of the tests electrical resistivity, diffusion of chlorides and migration of chlorides. This may be due to the sum of the effects that produced the nano and micro additions in the porosity. The result showed that nano silica has an important role in the pores refining and the micro silica decreases the total volume of them. This allows defining the life of these concretes in values to far exceed those required by the EHE-08, making it possible to reduce, significantly, the coating required in highly aggressive environment and to guarantee good behavior in service. Moreover, the mass loss due to freeze-thaw cycles is significantly lower in concretes containing nano silica than those containing micro silica. This result agrees with the capillary absorption test. In general, one can conclude that the binary mixture and more specifically the mixture with 5% of nano silica and 2.5% silica fume is which presents the best results in its durable behavior. This may be because in these mixtures, the nano silica behaves as cores activation of pozzolanic reactions. In addition, the durable extraordinary behavior may also be due to the continuity of the grading curve due to existence of micro silica, limestone filler, cement, sand and gravel with particle sizes that guarantees very compact mixtures which have high performance.

Estudio de hormigón autocompactante con árido reciclado

La tesis doctoral “Estudio de hormigón autocompactante con árido reciclado” realizada dentro del programa de doctorado de la Universidad Politécnica de Madrid “Máster en técnicas experimentales avanzadas en la ingeniería civil”, investiga la sustitución de áridos gruesos naturales por reciclados en hormigones autocompactantes, para demostrar la posibilidad de utilización de este tipo de árido en la fabricación de hormigones autocompactantes. En cuanto a la línea experimental adoptada, la primera fase corresponde a la caracterización de los cementos y de los áridos naturales y reciclados. En ella se han obtenido las principales características físicas y mecánicas. Una vez validadas las características de todos los materiales y adoptada una dosificación de hormigón autocompactante, se han elaborado cuatro dosificaciones con cuatro grados de incorporación de árido reciclado cada una, y una dosificación con seis grados de incorporación de árido reciclado. Fabricándose un total de 22 tipos de hormigón diferentes, sin contar todas las amasadas iniciales hasta la consecución de un hormigón autocompactante. Las cinco dosificaciones se han dividido en dos grupos para poder analizar con mayor grado de definición las características de cada uno. El primer grupo es aquel que contienen los hormigones con diferentes relaciones a/c, que incluye a la muestra A (a/c=0.55), muestra D (a/c=0.50) y muestra E (a/c=0.45). Por el contrario, el segundo grupo dispone de una relación fija de a/c=0.45 pero diferentes relaciones a/c efectivas, ya que algunas de las muestras disponen de un contenido de agua que permite contrarrestar la mayor absorción del árido reciclado. Estando en este grupo la muestra E (sin agua adicional), la muestra H (con presaturación de los áridos) y la muestra I (con un aporte de agua junto con el agua de amasado. Una vez fabricados los hormigones, se pasa a la segunda fase del estudio correspondiente a la caracterización del hormigón en estado fresco. En esta fase se han llevado a cabo los ensayos de escurrimiento, escurrimiento con anillo japonés, ensayo embudo en V y embudo V a los 5 minutos. Todos estos ensayos permiten evaluar la autocompactabilidad del hormigón según el anejo 17 de la EHE-08. La tercera fase del estudio se centra en la caracterización de los hormigones en estado endurecido, evaluando las características resistentes del hormigón. Para ello, se han realizado los ensayos de resistencia a compresión, a tracción, módulo de elasticidad y coeficiente de Poisson. En la cuarta y última fase, se han analizado la durabilidad de los hormigones, debido que a pesar de ofrecer una adecuada autocompactabilidad y resistencia mecánica, se debe de obtener un hormigón con una correcta durabilidad. Para tal fin, se ha determinado la resistencia a la penetración de agua bajo presión y carbonatación de las probetas. Este último ensayo se ha realizado teniendo en cuenta las condiciones del denominado método natural, con una exposición al ambiente de 90 días y 365 días. Con todos estos resultados se elaboraron las conclusiones derivadas de la investigación, demostrándose la posibilidad de fabricación de hormigones autocompactantes con árido reciclado (HACR) con sustituciones de hasta un 40%, e incluso dependiendo de la relación a/c con sustituciones del 60% y el 80%. ABSTRACT The doctoral thesis titled Analysis of self-compacting concrete with recycled aggregates, has been developed in accordance with the doctoral program: Master degree in advanced experimental techniques in civil engineering, at UPM. It investigates the possibility of replacing natural coarse aggregates with recycled coarse aggregates, in the field of self-compacting concrete. The aim of this dissertation is to analyze the possibility of using recycled coarse aggregates in the manufacture process of self-compacting concretes. Regarding the experimental part, the first phase refers to mechanical and physical characterization of some materials such as cement, natural aggregates and recycled aggregates. Once the characteristics of all materials have been validated and the mixing proportions have been adopted, four different mixes are elaborated by using four dosage rates of recycled aggregates in each one of the samples. Moreover, an additional sample consisting of six different dosages of recycled aggregates is considered. A total number of 22 concrete specimens have been manufactured, without including all the initial kneading samples used to obtain this type of self-compacting concrete. The aforementioned mixes have been divided in two different groups to be able to analyze with more definition. The first group is the one in which the concrete contains different values of the water - cement ratio. It includes the next samples: A (w/c=0.55), D (w/c=0.50) and E (w/c=0.45). The second group has a fixed water -cement ratio, w/c=0.45, but a different effective water - cement ratio, since some of the samples have a water content that enables to offset the major absorption of the recycled aggregates, being in this group the mixing E (without additional water), the mixing H (with saturated recycled aggregate) and the mixing I (with an additional water content to the existing kneading water). Once the concrete samples have been manufactured, the following section deals with the characterization of the concrete in fresh conditions. To accomplish this, several characterization tests are carried out such as the slump-flow test, test slump flow with Japanese ring, test V-funnel and V-funnel to 5 minutes. These tests are used to assess the self-compacting conditions according to the annex 17 of the EHE-08 The third phase of the study focuses on the mechanical characterization, the assessment of the strength properties of the concrete such as compressive strength, tensile strength, modulus of elasticity and Poisson´s ratio. Within the fourth and last phase, durability of the concrete is evaluated. This fact is motivated by the need to obtain not only good self-compacting and mechanical strength properties, but also adequate durability conditions. To accomplish the aforementioned durability, resistance of the samples under certain conditions such as water penetration pressure and carbonation, has been obtained. The latter test has been carried out taking into account the natural method, with an exhibition period to the environment of 90 days and 365 days. Through the results coming from this research work, it has been possible to obtain the main conclusions. It has been demonstrated the possibility to manufacture self-compacting concrete by using recycled aggregates with replacement rates up to 40% or, depending on the w/c ratio, rates of 60% and 80% might be reached.

The degree of nonlinearity and anisotropy of blood vessel elasticity

Blood vessel elasticity is important to physiology and clinical problems involving surgery, angioplasty, tissue remodeling, and tissue engineering. Nonlinearity in blood vessel elasticity in vivo is important to the formation of solitons in arterial pulse waves. It is well known that the stress–strain relationship of the blood vessel is nonlinear in general, but a controversy exists on how nonlinear it is in the physiological range. Another controversy is whether the vessel wall is biaxially isotropic. New data on canine aorta were obtained from a biaxial testing machine over a large range of finite strains referred to the zero-stress state. A new pseudo strain energy function is used to examine these questions critically. The stress–strain relationship derived from this function represents the sum of a linear stress–strain relationship and a definitely nonlinear relationship. This relationship fits the experimental data very well. With this strain energy function, we can define a parameter called the degree of nonlinearity, which represents the fraction of the nonlinear strain energy in the total strain energy per unit volume. We found that for the canine aorta, the degree of nonlinearity varies from 5% to 30%, depending on the magnitude of the strains in the physiological range. In the case of canine pulmonary artery in the arch region, Debes and Fung [Debes, J. C. & Fung, Y. C.(1995) Am. J. Physiol. 269, H433–H442] have shown that the linear regime of the stress–strain relationship extends from the zero-stress state to the homeostatic state and beyond. Both vessels, however, are anisotropic in both the linear and nonlinear regimes.

Torsional directed walks, entropic elasticity, and DNA twist stiffness

DNA and other biopolymers differ from classical polymers because of their torsional stiffness. This property changes the statistical character of their conformations under tension from a classical random walk to a problem we call the “torsional directed walk.” Motivated by a recent experiment on single lambda-DNA molecules [Strick, T. R., Allemand, J.-F., Bensimon, D., Bensimon, A. & Croquette, V. (1996) Science 271, 1835–1837], we formulate the torsional directed walk problem and solve it analytically in the appropriate force regime. Our technique affords a direct physical determination of the microscopic twist stiffness C and twist-stretch coupling D relevant for DNA functionality. The theory quantitatively fits existing experimental data for relative extension as a function of overtwist over a wide range of applied force; fitting to the experimental data yields the numerical values C = 120 nm and D = 50 nm. Future experiments will refine these values. We also predict that the phenomenon of reduction of effective twist stiffness by bend fluctuations should be testable in future single-molecule experiments, and we give its analytic form.

Dynamics and elasticity of the fibronectin matrix in living cell culture visualized by fibronectin–green fluorescent protein

Fibronectin (FN) forms the primitive fibrillar matrix in both embryos and healing wounds. To study the matrix in living cell cultures, we have constructed a cell line that secretes FN molecules chimeric with green fluorescent protein. These FN–green fluorescent protein molecules were assembled into a typical matrix that was easily visualized by fluorescence over periods of several hours. FN fibrils remained mostly straight, and they were seen to extend and contract to accommodate movements of the cells, indicating that they are elastic. When fibrils were broken or detached from cells, they contracted to less than one-fourth of their extended length, demonstrating that they are highly stretched in the living culture. Previous work from other laboratories has suggested that cryptic sites for FN assembly may be exposed by tension on FN. Our results show directly that FN matrix fibrils are not only under tension but are also highly stretched. This stretched state of FN is an obvious candidate for exposing the cryptic assembly sites.

Caracterização da farinha e do amido isolado da semente de jaca e comportamento reológico de dispersões de amido

O amido é um ingrediente com grande versatilidade de aplicação, e as sementes de jaca, fruto bem difundido, porém pouco aproveitado no Brasil, contêm uma quantidade considerável de amido, sendo ainda fonte de ferro e proteínas. Dessa maneira, os objetivos desse projeto foram a obtenção da farinha de sementes de jaca das variedades mole e dura, a extração do amido utilizando diferentes solventes, e a caracterização de suas propriedades físico-químicas, estruturais e funcionais, bem como a caracterização reológica de dispersões/géis de amido em cisalhamento estacionário e oscilatório. A extração alcalina do amido, além de reduzir significativamente o conteúdo de lipídeos e proteínas, deixando o amido mais puro, promoveu um aumento no teor de amilose e influenciou diretamente as características de inchamento e solubilidade, que apresentaram aumento significativo a partir da temperatura de 70 °C. O aumento da temperatura ocasionou aumento no poder de inchamento e solubilidade, que foi mais pronunciado para a variedade dura, porém esses valores ainda foram considerados baixos (< 17%). Os amidos de sementes de jaca apresentaram grânulos lisos, arredondados e em forma de sino, com formato mais truncado para o amido extraído com hidróxido de sódio. O diâmetro médio dos grânulos de amido foi menor para a extração alcalina, mas sempre com comportamento monomodal. Foi observado um padrão de difração de Raios-X do tipo A para todas as amostras estudadas, e o índice de cristalinidade foi maior para os amidos de sementes de jaca dura, com uma redução estimada em 70% para os amidos obtidos por extração alcalina. A temperatura de gelatinização dos amidos de semente de jaca foi considerada alta (70-100 °C). Os amidos de sementes de jaca dura obtidos na extração com água apresentaram maiores valores de viscosidade de pico e de Breakdown, que representa menor resistência mecânica. A extração com solução de NaOH 0,1 M aumentou a tendência a retrogradação de ~36% (extração aquosa) para 64% e 45% dos amidos de sementes de jaca das variedades mole e dura, respectivamente. Todas as amostras apresentaram comportamento pseudoplástico (n < 1) nas concentrações e temperaturas estudadas, e as dispersões e/ou géis de amido obtidos pela extração alcalina com NaOH apresentaram menor tixotropia e maiores valores de viscosidade. Os modelos Lei da Potência e Herschel Bulkley apresentaram ótimos ajustes aos pontos experimentais (R² ~0,998) para as amostras com 2 e 6 % de amido, respectivamente, porém para a concentração de 5%, o melhor modelo foi função da variedade do fruto usado na obtenção do amido. A dependência das propriedades reológicas com a temperatura foi analisada pela equação de Arrhenius e a energia de ativação foi baixa (15-25 kJ/mol). Quanto ao comportamento viscoelástico, as amostras com 5 e 6% de amido apresentaram comportamento de gel fraco e o aumento da concentração desse polissacarídeo produziu um aumento na elasticidade do material. Os módulos de armazenamento (G\') associados à elasticidade do gel de amido aumentaram durante o seu resfriamento nos ensaios de varredura de temperatura, o que pode ser relacionado à recristalização da amilose durante esse processo e mantiveram-se praticamente constantes no aquecimento isotérmico a 80 °C, sugerindo boa estabilidade térmica do gel. A farinha isolada da semente de jaca pode ser considerada fonte de fibras e apresentou elevados teores de proteínas (~14-16%) e ferro (~85-150 mg/kg). A distribuição do tamanho de partículas da farinha apresentou comportamento bimodal, com grânulos arredondados, presença de fibras e uma matriz proteica envolvendo os grânulos de amido. As propriedades de pasta revelaram maior pico de viscosidade para a farinha de semente de jaca mole. As características encontradas sugerem que os amidos de semente de jaca poderiam ser aplicados na produção de filmes biodegradáveis, e a farinha da semente de jaca poderia ser utilizada em substituição parcial à farinha convencional na fabricação de bolos e biscoitos.

Caracterização geométrica e mecânica de macrofibras poliméricas.

Uma grande diversidade de macrofibras poliméricas para reforço de concreto se encontram disponibilizadas hoje em dia. Por natureza estas fibras apresentam grande diversidade de características e propriedades. Estas variações afetam sua atuação como reforço no concreto. No entanto, não há normas brasileiras sobre o assunto e as metodologias de caracterização de normas estrangeiras apresentam divergências. Algumas normas definem que a caracterização do comportamento mecânico deva ser feita nos fios originais e outras que se devam utilizar métodos definidos para caracterização de materiais metálicos. A norma EN14889-2:2006 apresenta maior abrangência, mas deixa dúvidas quanto à adequação dos critérios de caracterização geométrica das fibras e não define um método de ensaio específico para sua caracterização mecânica. Assim, há a necessidade de estabelecimento de uma metodologia que permita a realização de um programa de controle de qualidade da fibra nas condições de emprego. Esta metodologia também proporcionaria uma forma de caracterização do material para estudos experimentais, o que permitiria maior fundamentação científica desses trabalhos que, frequentemente, fundamentam-se apenas em dados dos fabricantes. Assim, foi desenvolvido um estudo experimental focando a caracterização de duas macrofibras poliméricas disponíveis no mercado brasileiro. Focou-se o estudo na determinação dos parâmetros geométricos e na caracterização mecânica através da determinação da resistência à tração e avaliação do módulo de elasticidade. Na caracterização geométrica foi adotada como referência a norma europeia EN14889-2:2006. As medições do comprimento se efetuaram por dois métodos: o método do paquímetro e o método de análise de imagens digitais, empregando um software para processamento das imagens. Para a medição do diâmetro, além das metodologias mencionadas, foi usado o método da densidade. Conclui-se que o método do paquímetro, com o cuidado de esticar previamente as macrofibras, e o método das imagens digitais podem ser igualmente utilizados para medir o comprimento. Já parar determinar o diâmetro, recomenda-se o método da densidade. Quanto à caracterização mecânica, foi desenvolvida uma metodologia própria a partir de informações obtidas de outros ensaios. Assim, efetuaram-se ensaios de tração direta nas macrofibras coladas em molduras de tecido têxtil. Complementarmente, foi avaliado também o efeito do contato abrasivo das macrofibras com os agregados durante a mistura em betoneira no comportamento mecânico do material. Também se avaliou o efeito do método de determinação da área da seção transversal nos resultados medidos no ensaio de tração da fibra. Conclui-se que o método proposto para o ensaio de tração direta da fibra é viável, especialmente para a determinação da resistência à tração. O valor do módulo de elasticidade, por sua vez, acaba sendo subestimado. A determinação da área da seção da fibra através do método da densidade forneceu também os melhores resultados. Além disso, comprovou-se que o atrito das fibras com o agregado durante a mistura compromete o comportamento mecânico, reduzindo tanto a resistência quanto o módulo de elasticidade. Assim, pode-se afirmar que a metodologia proposta para o controle geométrico e mecânico das macrofibras poliméricas é adequada para a caracterização do material.

Calmness modulus of linear semi-infinite programs

Our main goal is to compute or estimate the calmness modulus of the argmin mapping of linear semi-infinite optimization problems under canonical perturbations, i.e., perturbations of the objective function together with continuous perturbations of the right-hand side of the constraint system (with respect to an index ranging in a compact Hausdorff space). Specifically, we provide a lower bound on the calmness modulus for semi-infinite programs with unique optimal solution which turns out to be the exact modulus when the problem is finitely constrained. The relationship between the calmness of the argmin mapping and the same property for the (sub)level set mapping (with respect to the objective function), for semi-infinite programs and without requiring the uniqueness of the nominal solution, is explored, too, providing an upper bound on the calmness modulus of the argmin mapping. When confined to finitely constrained problems, we also provide a computable upper bound as it only relies on the nominal data and parameters, not involving elements in a neighborhood. Illustrative examples are provided.

Relationship between static and dynamic elastic modulus of calcarenite heated at different temperatures: the San Julián's stone

The San Julián’s stone is the main material used to build the most important historical buildings in Alicante city (Spain). This paper describes the analysis developed to obtain the relationship between the static and the dynamic modulus of this sedimentary rock heated at different temperatures. The rock specimens have been subjected to heating processes at different temperatures to produce different levels of weathering on 24 specimens. The static and dynamic modulus has been measured for every specimen by means of the ISRM standard and ultrasonic tests, respectively. Finally, two analytic formulas are proposed for the relationship between the static and the dynamic modulus for this stone. The results have been compared with some relationships proposed by different researchers for other types of rock. The expressions presented in this paper can be useful for the analysis, using non-destructive techniques, of the integrity level of historical constructions built with San Julián’s stone affected by fires.

Fire-resistance, physical, and mechanical characterization of particleboard containing Oceanic Posidonia waste

In this work, particleboards manufactured with Oceanic Posidonia waste and bonded with cement are investigated. The particleboards are made with 3/1.5/0.5 parts of cement per part of Posidonia waste. The physical properties of bulk density, swelling, surface absorption, and dimensional changes due to relative humidity as well as the mechanical properties of modulus of elasticity, bending strength, surface soundness, perpendicular tensile strength and impact resistance are studied. In terms of the above properties, the best results were obtained for particleboards with high cement content and when the waste “leaves” are treated (crushed) before board fabrication, due to internal changes to the board structure under these conditions. Based on the results of fire tests, the particleboard is non-flammable without any fire-resistant treatment.

Revisiting the effect of foundation embedment on elastic settlement: A new approach

The effect of foundation embedment on settlement calculation is a widely researched topic in which there is no scientific consensus regarding the magnitude of settlement reduction. In this paper, a non-linear three dimensional Finite Element analysis has been performed with the aim of evaluating the aforementioned effect. For this purpose, 1800 models were run considering different variables, such as the depth and dimensions of the foundation and the Young’s modulus and Poisson’s ratio of the soil. The settlements from models with foundations at surface level and at depth were then compared and the relationship between them established. The statistical analysis of this data allowed two new expressions, with a mean maximum error of 1.80%, for the embedment influence factor of a foundation to be proposed and these to be compared with commonly used corrections. The proposed equations were validated by comparing the settlements calculated with the proposed influence factors and the true settlements measured in several real foundations. From the comprehensive study of all modelled cases, an improved approach, when compared to those proposed by other authors, for the calculation of the true elastic settlements of an embedded foundation is proposed.