Examinando por Materia "Creep"

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    Ítem
    Comportamiento de tejas de cubierta tipo multicapa fabricadas con asfalto crudo y modificado cuando son sometidas a cargas constantes
    (Universidad EAFIT, 2011) López Bula, Pedro Javier; Múnera Ossa, Juan Camilo
    El presente trabajo, analiza las propiedades viscoelasticas de diferentes materiales asfalticos después de ser sometidos a cargas permanentes y a diferente temperatura -- Estas cargas simulan las que eventualmente se pueden presentar en la aplicacion y fabricación de productos asfalticos ampliamente utilizados en el sector de la construcción -- Para este estudio se utilizó asfalto crudo y modificado con diferentes polímeros: Cera de polietileno (CERA), caucho molido de llanta (CR), copolimero de estireno – butadieno - estireno (SBS), fueron los aditivos poliméricos utilizados como modificadores del asfalto, tanto el asfalto crudo como las diferentes mezclas fueron sometidas a ensayos creep con cargas constantes de 10 N, 60 N, 110 N, 160 N y 210 N -- Con el fin de determinar la dependencia del comportamiento del asfalto crudo y modificado respecto a la temperatura, se desarrollaron ensayos a tres diferentes temperaturas: Ambiente (aprox. 23°C), 30°C y 40°C -- Entre los resultados obtenidos, se destaca que la menor deformación de los materiales en cuestión la presentó el asfalto modificado con CERA al 6 %, seguido del asfalto modificado con CERA al 3 %, asfalto modificado con SBS al 6 %, asfalto modificado con SBS al 3 %, asfalto modificado con CR al 3 % y finalmente, el asfalto modificado con CR al 6 % a temperatura ambiente -- Mientras, que al aumentar la temperatura a 30 °C y 40 °C, se presenta el caso contrario en cuanto a deformación de los materiales, siendo los asfaltos CR 6 % y SBS 3 % los que mejor comportamiento presentaron durante todo el ensayo -- Los materiales con mejor comportamiento serán propuestos como material base para la fabricación de prototipos de tejas a nivel industrial
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    Ítem
    Spherical indentation behavior of asphalt mixtures
    (ASCE-AMER SOC CIVIL ENGINEERS, 2007-01-01) Ossa, E.A.; Collop, A.C.; Ossa, E.A.; Collop, A.C.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
    The spherical indentation response of a dense bitumen macadam asphalt mixture with two different volume fractions of bitumen binder is investigated both experimentally and via an analytical model. The model for the indentation of bitumen developed by Ossa et al. in 2005, was used to study the spherical indentation behavior of the mixtures with good agreement when compared to experimental results. An extensive experimental study of the monotonic and recovery spherical indentation behavior is reported for a range of temperatures. In line with the predictions of the model, the monotonic indentation response of the mixtures exhibits a power-law dependence on the indentation force. The model is also successful in capturing the indentation recovery behavior of the mixtures. A comparison of the material parameters obtained from uniaxial compression and indentation tests showed that indentation tests can be used in an easy and reliable way to obtain the fundamental asphalt parameters. Further, parameters found from indentation tests implicitly account for the confining conditions generated by the aggregate particles below the indenter. © 2007 ASCE.
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    Ítem
    Triaxial deformation behavior of bituminous mixes
    (ASCE-AMER SOC CIVIL ENGINEERS, 2010-02-01) Ossa, E. A.; Deshpande, V. S.; Cebon, D.; Ossa, E. A.; Deshpande, V. S.; Cebon, D.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
    The triaxial compressive response of bituminous mixes with volume fractions of aggregate in the range 52 to 85% was investigated over a wide range stresses and strain rates. The types of loadings considered include triaxial monotonic constant stress and constant applied strain rate, as well as creep recovery, continuous cyclic, and stress pulse train loadings. The mixes with a "fully dense" aggregate skeleton were found to dilate under all loading conditions and the creep response of the mixes was dependent on both the deviatoric and hydrostatic stresses. By contrast, recovery was found to occur under zero applied deviatoric stresses with the recovery rate only dependent on the "recoverable strain" and independent of any superimposed hydrostatic stress. Continuous and pulse loading cyclic stress-controlled tests showed that the response of the mixes was governed by the mean applied deviatoric stress in the continuous cyclic tests while strain recovery was important in the pulse loading tests. A phenomenological constitutive model was proposed to fit the measured triaxial response of the bituminous mixes and shown to capture the measurements over all the triaxial stress states and loading time histories investigated here. Furthermore, the model was extended to capture the temperature dependence of the mixtures which is governed by the temperature dependence of the bitumen binder. © 2010 ASCE.