Temperature segregation and its impact on the quality and performance of asphalt pavements

Temperature segregation is non-uniform temperature distribution across the uncompacted asphalt mat during paving operations and may have detrimental effects on the quality and performance of asphalt pavements. However, many research studies conducted across the US have reported mixed observations regarding its effects on the initial quality and long-term performance of asphalt pavements.The objective of this study was to determine the effects of the temperature segregation on the density and mechanical properties of Louisiana asphalt mixtures. Seven asphalt rehabilitation projects across Louisiana were selected. A multisensor infrared bar (Pave-IR) system and a hand-held portable thermal camera were used to measure the temperature of asphalt mats. Field core samples were collected from various areas with varying severity levels of temperature segregation and tested for the density, fracture resistance (J_c) by semi-circular bending (SCB), rut depth by wheel tracking, and dynamic modulus (|E*|) by indirect tension (IDT) devices.Two distinctive patterns of non-uniform temperature distribution were observed: a cyclic and irregular temperature segregations. Laboratory test results showed that highly temperature segregated asphalt pavements (i.e., temperature differentials ≥41.7°C) can have significantly lower densities and the mechanical properties than the non-segregated area, especially when the temperature differentials are measured at compaction.     

Catalytic Efficiency of Ceria–Zirconia and Ceria–Hafnia Nanocomposite Oxides for Soot Oxidation

The catalytic oxidation of soot particulates has been investigated over CeO₂, CeO₂–ZrO₂ and CeO₂–HfO₂ nanocomposite oxides. These oxides were synthesized by a modified precipitation method employing dilute aqueous ammonia solution. The prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and BET surface area methods. The soot oxidation has been evaluated by a thermogravimetric method under ‘tight contact’ conditions. The XRD results revealed formation of cubic CeO₂, Ce_0.75Zr_0.25O₂ and Ce_0.8Hf_0.2O₂ phases in case of CeO₂, CeO₂–ZrO₂ and CeO₂–HfO₂ samples, respectively. TEM studies confirm the nanosized nature of the catalysts. Raman measurements suggest the presence of oxygen vacancies, lattice defects and oxide ion displacement from normal ceria lattice positions. UV-Vis DRS studies show presence of charge transfer transitions Ce³⁺←O^2? and Ce⁴⁺←O^2? respectively. The catalytic activity studies suggest that the oxidation of soot could be enhanced by incorporation of Zr⁴⁺ and Hf⁴⁺ into the CeO₂ lattice. The CeO₂–HfO₂ combination catalyst exhibited better activity than the CeO₂–ZrO₂. The observed high activity has been related to the nanosized nature of the composite oxides and the oxygen vacancy created in the crystal lattice.     

Flood Frequency Modeling and Prediction of Beki and Pagladia Rivers Using Deep Learning Approach

Neural Processing Letters - Flood is one of the major reasons of death and despair in the North East Indian state of Assam during the monsoon months each year. The flooding in adjacent areas...     

Utilizing the Oxygen Carrier Property of Cerium Iron Oxide for the Low-Temperature Synthesis of 1,3-butadiene from 1-butene

Catalysis Letters - Low-temperature oxidative dehydrogenation (ODH) of 1-butene to 1,3-butadiene is one of the challenging reactions in the polymer industry. Towards this a highly dispersed cerium...