The Mechanistic–Empirical Pavement Design Guide (MEPDG) and MEPDG software are tools that provide more rational pavement designs than previous guides. The application of the mechanistic–empirical method, however, requires careful consideration of the input data and proper calibration to local conditions. Since 2004, several efforts have been made in Chile to study implementation of MEPDG in that country. The work has included obtaining local input data (axle load distributions, weather, and material characteristics), calibration efforts for distress prediction, and comparison of pavement designs by using MEPDG and the local design method. Axle load distributions were obtained for three important highways in the most populated area in the country. Statistical analysis was performed to compare the default load spectra from MEPDG with the local spectra. Significant differences were observed. Weather information was obtained for six cities that represent broadly the different weather conditions in the country. Master curves were developed for Level 2 design on the basis of the aggregate and binder properties of the local materials. Preliminary local calibration factors were obtained for transverse cracking and faulting of jointed plain concrete pavement. These local data were employed to develop pavement designs with the MEPDG software; these designs were then compared with designs developed with the current Chilean design methodology, which is based on AASHTO 93 and 98 methods. The work presented shows that the implementation of the MEPDG is possible for countries of Latin America. Some recommendations are provided for future versions of the MEPDG to make use of the software in the Southern Hemisphere easier and friendlier.
This study addressed the need for more detailed weather information in the context of pavement design with the Mechanistic–Empirical Pavement Design Guide from weather information available for Chile. An initial database was developed with the available hourly data in the country, and the sensitivity of distress predictions for Chilean weather was studied. Because of the limited availability of hourly climatic data, different methods were proposed for completing the missing data. As their inputs, the developed models used weather information that was more generally available. A sinusoidal–exponential model was used for the minimum and maximum daily temperature. An exponential model for hourly humidity based on maximum and minimum daily humidity was also used. Linear interpolation between the available hours with data for wind speed and cloud cover was sufficient to complete the hourly information for these variables. The precision of the distress predictions with these models proved to be accurate compared with the predictions with actual hourly weather data. The models are being successfully used to expand the number of available weather stations for pavement design in Chile. The models are also useful for validating the existing weather stations and detecting inaccuracies and errors in the recorded hourly data.
ResumenEl objetivo de esta investigación fue obtener una caracterización reológica y clasificación avanzada para un grupo de betunes asfálticos modificados y sin modificar utilizados actualmente en Chile. Estudiando seis betunes asfálticos, provenientes de tres empresas asfalteras del medio nacional. Cada empresa aportó con un betún tradicional y un betún modificado. Los tres betunes tradicionales clasificados como CA 24 y los tres modificados clasificados como 60-80 modificados con SBS. Se realizó la caracterización reológica utilizando un reómetro de corte dinámico y un reómetro de viga en flexión, para los betunes en estado original, envejecimiento primario (RTFOT) y envejecimiento secundario (PAV). Determinando para cada uno la clasificación por grado de desempeño, ensayo de fluencia y recuperación (creep and recovery), curvas maestras y diagramas de Black. Se realizó además una completa batería de ensayos tradicionales al total de los betunes asfálticos, para los tres niveles de envejecimiento mencionados. La caracterización reológica permitió determinar las propiedades fundamentales de los betunes a temperaturas altas, temperaturas intermedias y bajas temperaturas. Estas propiedades en conjunto con una adecuada zonificación climatológica de Chile, podrían ser utilizadas para confeccionar una especificación de betunes moderna para nuestro país.También se demostró que para que los ensayos tradicionales tengan alguna utilidad, deben ser realizados para las siguientes condiciones: altas temperaturas, temperaturas intermedias, bajas temperaturas, ligante original, ligante con envejecimiento primario (RTFOT) y ligante con envejecimiento secundario (PAV). Solamente cuando se realizan ensayos para todas las condiciones anteriores, es posible encontrar información y resultados que son comparables a los de Superpave. Palabras Clave: Reología, betunes asfálticos, reómetro Abstract The purpose of this research was to achieve an advanced rheological characterization and classification for a set of modified and non-modified asphaltic bitumens
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