A novel algorithm to reproduce the arrangement of grains in polycrystalline materials was recently published by the authors. In this original approach, a dense package of circles (or spheres) with the same distribution as the grains is generated to produce a set of Voronoi cells that are later modified to Laguerre cells representing the original structure. This algorithm was successfully applied to materials with somewhat equidimensional grains; however, it fails for long-shaped grains. In this paper, modifications are provided in order to overcome these drawbacks. This is accomplished by moving each vertex of the Voronoi cells in such a way that the vertex should be equidistant from the particles with respect to the Euclidean distance. The algorithm is applied to packages of ellipses and spherocylinders in 2D. An example for a package of spheres is also provided to illustrate the application for a simple 3D case. The adherence between the generated packages and the corresponding tessellations is verified by means of the Jaccard coefficient (J). Several packages are generated randomly and the distribution of J coefficients is investigated. The obtained values satisfy the theoretical restraints and the quality of the proposed algorithm is statistically validated.
The paper presents a comparative study between the properties of a conventional binder and a polymer-modified binder, as well as some mechanical properties of hot mix asphalt concrete (HMA) made with these binders. The comparation of binder based on conventional indices and advanced dynamic properties obtained with a dynamic shear rheometer (DSR). These include the dynamic modulus |G*|and phase angle (δ) master curves, the fatigue susceptibility in the LAS (Linear Amplitude Sweep) and permanent deformations in the MSCR (Multi Stage Creep Recovery). The asphalt mixtures dosed and compacted according to the Superpave methodology. The mechanical properties explored in concrete asphalt (CA) specimens subjected to moisture-induced damage and static creep tests. The results show the positive effects of polymer addition in the binder's and hot mix asphalt concrete properties, especially with regard to elastic resilience and permanent deformation reduction.
RESUMO A geração e o gerenciamento de resíduos sólidos industriais consideram-se uma problemática ambiental no mundo. Vários estudos têm se concentrado na utilização de resíduos da construção civil no âmbito da pavimentação. O objetivo deste artigo é avaliar o uso do pó de agregados reciclados de concreto RFPA (Recycled Fine Aggregates Powder) no Concreto Betuminoso Usinado a Quente (CBUQ). Para tal fim, se fabricaram três tipos de misturas asfálticas: a mistura de referência com materiais convencionais e dois misturas de estudo com substituição do 3% e 6% do filer natural pelo RFAP (composição total da massa da mistura). Avaliou-se a resistência sob carga monotônica das misturas (Ensaio Marshall e Tração Indireta-RT) e a resistência ao desgaste Cântabro. Uma análise de variância (ANOVA) foi realizada para verificar se os resultados obtidos eram estatisticamente significativos. Ao substituir a 3% do fíler da granulometria pelo pó RFAP, obteve-se um comportamento mecânico satisfatório sob a ação das cargas monotônicas, embora houvesse aumento da perda de massa no ensaio Cântabro. Os resultados evidenciam que a utilização do RFAP da forma proposta é viável desde o ponto de vista técnico e ambiental, por permitir uma forma de disposição final segura de resíduos.
Por varias décadas, en la práctica ingenieril se ha evaluado la influencia del trazado de la carretera en la seguridad vial mediante el análisis de la consistencia; para ello es necesario contar con los perfiles de velocidad de operación del proyecto nuevo o de la carretera existente. Con este fin, generalmente, se emplean modelos de velocidad de operación existentes que fueron desarrollados para otras condiciones, regiones o países. En los análisis de consistencia del trazado es imprescindible contar con la información de la planta, el perfil del proyecto y la velocidad de operación de los vehículos. Una de las principales dificultades y fuentes de error en estos análisis radica en determinar la velocidad de operación. El objetivo del trabajo es desarrollar modelos de predicción de velocidad de operación para Costa Rica que consideren las características del trazado y las condiciones del parque vehicular. El procedimiento seguido incluye una serie de etapas, desde el análisis de las carreteras del territorio hasta el desarrollo de los modelos de predicción del perfil de velocidad y su validación. Como resultado de la investigación se proponen, por primera vez en Costa Rica, modelos de predicción de las velocidades de operación de las rutas nacionales con características rurales en terreno llano. Se demuestra que las ecuaciones propuestas presentan menores errores de estimación si se comparan con algunos de los modelos más usados internacionalmente.
This paper evaluated the physical-mechanical characteristics of two asphalt mixtures. One mix with conventional asphalt and the other with asphalt modified with recycled rubber grain. For this purpose, the asphalt mix designs were made by means of the Marshall methodology. Subsequently, asphalt mixtures were manufactured to analyze the action of monotonic loads (indirect tensile strength) and dynamic loads (resilient modulus). Previously, each type of asphalt mix was subjected to short- and long-term aging conditions, following Aastho guidelines. It is concluded that the incorporation of recycled rubber grain makes the changes in mechanical properties with aging not very noticeable in relation to mixtures without this material.
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