For a better understanding of the changing trend in crystalline components of asphalt binders, as... more For a better understanding of the changing trend in crystalline components of asphalt binders, asphalt binders originating from the SHRP Materials Reference Library with different oxidation degrees (unaged, 20 h PAV, and 60 h PAV) were prepared. The native asphalt binders and their oxidized residues were characterized by liquid-state nuclear magnetic resonance (NMR) spectroscopy and high-temperature gas chromatography (HTGC). The results showed that, compared with other carbon types, the content of internal methylene carbons of long paraffinic chains between different SHRP binders was quite different. The NMR average length of a long paraffinic internal methylene chain showed a good correlation with the wax content obtained at −20 °C using the methyl ethyl ketone (MEK) precipitation method and also the recently developed variable-temperature Fourier-transform infrared spectroscopy (VT-FTIR) method. In most cases, the average length of straight internal methylene carbons of a long pa...
2013 1st International Conference on Artificial Intelligence, Modelling and Simulation, 2013
Dynamic modulus, E is one of the fundamental properties defining the response of hot mix asphalt ... more Dynamic modulus, E is one of the fundamental properties defining the response of hot mix asphalt (HMA) mixtures in flexible pavement systems. Correspondingly, HMA materials are characterized by E master curve incorporating time and temperature effects. One of the widely used models, modified by Bonaquist (2009) is the MEPDG master curve model. The aim of this study is to obtain dynamic modulus data using the modified MEPDG master curve model. The sample has been tested at unconfined pressure where the unconfined master curve typically used in mechanistic-empirical (M-E) pavement analysis methods. From the Goodness-of-fit statistics, most of the sample gave an excellent correlation when R2 ≥ 0.90. It also has been supported by the standard error ratio when the Se/Sy ≤ 0.35. Nonetheless, the correlation coefficient, R2 is not always a reliable coefficient to measure the Goodness-of-fit for nonlinear regression analysis. Furthermore, there may be overall and/or local biases in the predictions that can cause significant reductions in accuracy under certain conditions.
The use of Reclaimed Asphalt Pavement (RAP) has been enormously increased from the last two decad... more The use of Reclaimed Asphalt Pavement (RAP) has been enormously increased from the last two decades. In fact using RAP in pavement construction has now become common practice in many countries. Using RAP not only economical and environmental friendly but also preserve the natural resources and similar or even better in structural performance than virgin asphalt mixtures. This paper presents an experimental study to evaluate the effect of various types and percentages of RAP on the properties of asphalt mixtures. Four mixtures, which were the combination of two different virgin aggregates and two different RAP sources were studied in this research. The mixtures were designed by Marshall method at a wide range of 0 to 100% RAP blends. RAP material was blended with virgin aggregate such that all specimens tested had approximately the same gradation. Mixtures containing RAP showed significant variability and the variability increased with the increase in RAP content.
Over 700 bike-sharing systems are currently in operation worldwide, and the number of systems has... more Over 700 bike-sharing systems are currently in operation worldwide, and the number of systems has grown quickly in recent years. Rwanda's bike-sharing system has only recently begun operations and has encountered numerous challenges. The current study used an Ordinal Priority Approach (OPA) to examine these challenges and provide an acceptable strategy for overcoming them. Five strategies have been established. These strategies are prioritized using four criteria. The results indicate that “theft” and “damage of some bikes when being returned” are the most critical challenges while the first alternative “improving the current bike infrastructure to better serve the bike share system” is the appropriate strategy to overcome these challenges for a successful operation of the bike share system. Taking into account the findings, recommendations were provided to help local administrative bodies handle these challenges.
For a better understanding of the changing trend in crystalline components of asphalt binders, as... more For a better understanding of the changing trend in crystalline components of asphalt binders, asphalt binders originating from the SHRP Materials Reference Library with different oxidation degrees (unaged, 20 h PAV, and 60 h PAV) were prepared. The native asphalt binders and their oxidized residues were characterized by liquid-state nuclear magnetic resonance (NMR) spectroscopy and high-temperature gas chromatography (HTGC). The results showed that, compared with other carbon types, the content of internal methylene carbons of long paraffinic chains between different SHRP binders was quite different. The NMR average length of a long paraffinic internal methylene chain showed a good correlation with the wax content obtained at −20 °C using the methyl ethyl ketone (MEK) precipitation method and also the recently developed variable-temperature Fourier-transform infrared spectroscopy (VT-FTIR) method. In most cases, the average length of straight internal methylene carbons of a long pa...
2013 1st International Conference on Artificial Intelligence, Modelling and Simulation, 2013
Dynamic modulus, E is one of the fundamental properties defining the response of hot mix asphalt ... more Dynamic modulus, E is one of the fundamental properties defining the response of hot mix asphalt (HMA) mixtures in flexible pavement systems. Correspondingly, HMA materials are characterized by E master curve incorporating time and temperature effects. One of the widely used models, modified by Bonaquist (2009) is the MEPDG master curve model. The aim of this study is to obtain dynamic modulus data using the modified MEPDG master curve model. The sample has been tested at unconfined pressure where the unconfined master curve typically used in mechanistic-empirical (M-E) pavement analysis methods. From the Goodness-of-fit statistics, most of the sample gave an excellent correlation when R2 ≥ 0.90. It also has been supported by the standard error ratio when the Se/Sy ≤ 0.35. Nonetheless, the correlation coefficient, R2 is not always a reliable coefficient to measure the Goodness-of-fit for nonlinear regression analysis. Furthermore, there may be overall and/or local biases in the predictions that can cause significant reductions in accuracy under certain conditions.
The use of Reclaimed Asphalt Pavement (RAP) has been enormously increased from the last two decad... more The use of Reclaimed Asphalt Pavement (RAP) has been enormously increased from the last two decades. In fact using RAP in pavement construction has now become common practice in many countries. Using RAP not only economical and environmental friendly but also preserve the natural resources and similar or even better in structural performance than virgin asphalt mixtures. This paper presents an experimental study to evaluate the effect of various types and percentages of RAP on the properties of asphalt mixtures. Four mixtures, which were the combination of two different virgin aggregates and two different RAP sources were studied in this research. The mixtures were designed by Marshall method at a wide range of 0 to 100% RAP blends. RAP material was blended with virgin aggregate such that all specimens tested had approximately the same gradation. Mixtures containing RAP showed significant variability and the variability increased with the increase in RAP content.
Over 700 bike-sharing systems are currently in operation worldwide, and the number of systems has... more Over 700 bike-sharing systems are currently in operation worldwide, and the number of systems has grown quickly in recent years. Rwanda's bike-sharing system has only recently begun operations and has encountered numerous challenges. The current study used an Ordinal Priority Approach (OPA) to examine these challenges and provide an acceptable strategy for overcoming them. Five strategies have been established. These strategies are prioritized using four criteria. The results indicate that “theft” and “damage of some bikes when being returned” are the most critical challenges while the first alternative “improving the current bike infrastructure to better serve the bike share system” is the appropriate strategy to overcome these challenges for a successful operation of the bike share system. Taking into account the findings, recommendations were provided to help local administrative bodies handle these challenges.
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Papers by Yanjun Qiu