RESUMENLas propiedades reológicas del asfalto dependen de las proporciones en que están presentes sus componentes, las cuales varían de acuerdo con el origen de los crudos de petróleo. El comportamiento reológico del ligante tiene una influencia significativa en las propiedades de la mezcla asfalto-agregado (ahuellamiento, fatiga y susceptibilidad térmica). Para describir el comportamiento reológico del asfalto proveniente del Complejo Industrial de Barrancabermeja (CIB) y del asfalto modificado con material reciclado (poliestireno expandido y grano de caucho de llanta reciclada) con control de granulometría y sin él, se realizaron mediciones de viscosidad a diferentes temperaturas (con intervalos de 2 ºC) con el viscosímetro rotacional Brookfield, y a partir de estos datos se propusieron varias expresiones matemáticas que describen el comportamiento de la viscosidad en términos de la temperatura, se evaluaron en términos del coeficiente de determinación y se hallaron las temperaturas de mezclado y compactación. Los resultados indican que el mejor ajuste en los tres casos corresponde al modelo tipo Arrhenius truncado, con correlaciones entre 0,9945 y 0,9968. Las temperaturas de mezclado y compactación calculadas a partir de este modelo comparadas con las de las normas ASTM D2493 (2001) y AASHTO (2002) resultaron significativamente disímiles para el asfalto modificado (con polímeros de granulometría controlada) pero similares para el asfalto original. De otra parte, con el fin de establecer la estructura química del asfalto original y modificado así como su influencia sobre la viscosidad, se realizó la separación de cada muestra de acuerdo con la norma ASTM D4124 (2001). Los resultados indicaron que sólo ocurrió cambio estructural en el asfalto modificado con polímeros de granulometría controlada, lo que muestra la relación entre la composición química y la viscosidad de los tres ligantes estudiados. ABSTRACTThe rheological properties of asphalt are directly related to its chemical composition, which varies with the origin of crude oil. The rheological behavior of the binder has a significant influence on the properties of the asphalt--aggregate mixture (truck-wheel test, fatigue, and thermal susceptibility,). To describe the rheological behavior of asphalt from the Barrancabermeja Industrial Complex (IBC) and the modified asphalt with recycled material (polystyrene and tire rubber) with and without control of particle size, viscosity measurements were conducted at different temperatures (intervals of 2 º C) with a Brookfield rotational viscometer, and from these data suggested several mathematical expressions that describe the behavior of viscosity in terms of temperature, were evaluated in terms of the coefficient of determination, and determined the mixing and compaction temperatures. The results indicate that the best fit in the three cases corresponds to the Arrhenius model truncation, correlations between 0.9945 and 0.9968. The mixing and compaction temperatures calculated from this model compared to those o...

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Elastic modulus of the radial section of theGuadua angustifoliaKunth variety Bicolor was studied by technique of propagation of acoustic waves; the signal time delay in the samples was used as the control parameter. The studies were carried out in the culm cross-section in radial direction. The results indicate that the elastic modulus and the propagation velocity of the longitudinal wave in each of the cross-sections varied from2.5×107to1.6×109 Pa and from 1370 to 250 m/s for the inside and outside region of the culm, respectively. This behavior is due to the inhomogeneity, the water concentration, the fiber density, and the silicon concentration. The Raman spectroscopy analysis showed bands associated with hemicellulose, cellulose (carbon-carbon bonds), hydroxides carbon, and lignin. Silicone polymer compounds were identified by gas chromatography/mass spectroscopy.

The vibrational modes and compositional behavior of plant material ofGuadua angustifoliaKunth Variety Bicolor (GAKVB) and the characteristics associated with color changes were evaluated by Raman, infrared, and energy-dispersive X-ray spectroscopy. In the vibrational spectra, the frequencies of 1598, 2099, and 845 cm−1were associated with yellow and blue pigments. These pigments can be found in natural organic dyes of vegetable origin, such as indigo blue (anil or pastel), extracted from Central American shrubs (Indigoferaand indaco) (Domenech, 2010), in some pigments synthesized in solid-state reactions from aluminum oxides, such as CaAl12O19, that have a turquoise color (Costa et al., 2009), and in Indian yellow (MgC19H16O11·5H2O). Using an immersion test, it was shown that the color was stable and that no loss of color occurred when photosynthesis was halted in the sample. The green and yellow stripes are assigned to Fe, N, Mg, and Si compounds. The yellow is due to decrease of Fe, Mg, and elemental Si. Results are obtained using energy-dispersive X-ray spectroscopy and Raman measurements.