Microcapsules containing rejuvenator are particles used to increase the self-healing capability of asphalt. To date, no reports focus on studying their behaviors in asphalt binders between the aggregates. The purpose of this work was to directly observe the states of self-healing microcapsules in asphalt binders. Asphalt samples were prepared by mixing bitumen and various weight contents of microcapsules. Experimental tests were carried out to observe the morphology, integrity, distribution, thermal stability, interface bonding and triggered rupture of microcapsules in asphalt binders. Fluorescence microscope morphologies and X-ray computed tomography images showed that microcapsules survived in asphalt resisting high temperature and strong agitation without premature damage. At the same time, microcapsules were homogenously dispersed in asphalt binders avoiding particles aggregation and adhesion. A circular heating-cooling process was used to simulate temperature changes in the natural environment. It was found that microcapsules still kept a stable state after an extreme temperature change. In addition, interface debonding phenomenon did not appear. Microscopic observation results reflected that microcapsules could be pierced by microcracks in the asphalt binder and the encapsulated rejuvenator flowed out under the force of capillary action. All the above conclusions indicate that microcapsules containing rejuvenator meet the application conditions and play the role of self-healing material in asphalt binders.

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The downstream peak discharge increase during hyperconcentrated floods in the Yellow River has been attributed to bed erosion, roughness reduction and floodplain effects. While great improvements have been made on the nderstandings of the roles of bed erosion and roughness reduction, the effects of floodplain remain poorly understood. Here, as a first step to reveal the floodplain effects, we present a numerical experimental study on how the channel-floodplain system reacts to a hyperconcentrated flood process. For this purpose, schematized channel-floodplain systems are designed and the classical 1992 flood record data is prescribed at the upstream boundary. By applying a fully coupled morphodynamic model, numerical experiments are conducted for a comprehensive analysis on the effects of bed erodibility, floodplain width, bed roughness variation, symmetry and longitudinal variability of geomorphology. Our results show two distinct trends for the response of channel- floodplain system depending on bed erodibility. For a small bed erodibility, both channel and floodplain experience erosion. For a moderate/large bed erodibility, only the channel experiences erosion whereas deposition occurs on the floodplain. The variation of the floodplain width does not affect these erosion-deposition behaviors while changing the magnitude and patterns of floodplain deposition. The
longitudinally discontinuous channel-floodplain divided by either water storage areas or housing/farming banks diminishes the floodplain deposition at the discontinuous locations. The present numerical experiments do not show an obvious peak discharge increase, nonetheless, the recognized erosion-deposition characteristics would help further study of the floodplain effects on the peak of hyperconcentrated floods. @en

The concept of real-time kinematic precise point positioning (PPP-RTK) is to achieve integer ambiguity resolution (IAR) at a single global navigation satellite system (GNSS) user by providing network-derived satellite phase biases (SPBs) in addition to the standard PPP corrections. The integerness of the user ambiguities gets recovered and resolved, obtaining high-precision position solutions with the aid of the precise carrier-phase observables. Most of current PPP-RTK methods focus on processing dual-frequency or multifrequency GNSS network observations. The new developing Indian regional navigation satellite system (IRNSS), however, provides only a single-frequency signal in L-band, and shares the L5 frequency with the American global positioning system (GPS), the European Galileo, and the Japanese quasi-zenith satellite system (QZSS). This contribution proposes a new array-aided state-space RTK (SS-RTK) method following the concept of PPP-RTK, which is applicable to the single-frequency network data processing. A small array of multi-GNSS stations, separated by a few meters, takes the role of reference station to provide a batch of single-frequency RTK corrections. Similar to PPP-RTK, the single-frequency stand-alone user ambiguities are a double-differenced (DD) form after applying the SS-RTK corrections. Based on the proposed array-aided SS-RTK concept, the authors analyze the capability of the single-receiver positioning with IAR using L5/E5a frequency observations from IRNSS, as well as GPS, Galileo, and QZSS. Results from real-data experiments demonstrate that even though stand-alone RTK using current IRNSS satellites is not yet possible, they effectively contribute to the tightly integrated multisystem RTK. By increasing the number of antennas in the array used for SS-RTK corrections, the user would achieve more precise and reliable positions. After increasing the dimension of the array to four antennas, a 4-10% improvement in the IAR success rate is experienced. Moreover, the convergence time of the float solutions, reaching a subdecimeter precision level, reduces from 30 to 40 min (single-antenna array) to about 20 min (four-antenna array).

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The development of an Australian PPP-RTK processing platform is an important component of a multi-GNSS (global navigation satellite system) enabled national positioning infrastructure. The PPP-RTK concept extends the precise point positioning (PPP) concept by providing single-receiver users with information enabling integer ambiguity resolution, thereby reducing convergence times as compared to that of PPP. In this contribution we present and discuss the underlying principles of the PPP-RTK platform for both network and user. We demonstrate its GPS-based performance and provide an outlook for when multi-GNSS constellations, such as BDS, Galileo and QZSS, become fully operational.

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The aging problem of bitumen leads to pavement failure after years of usage. Microcapsules containing rejuvenator is a promising chemical product applied to improve the self-healing ability of bitumen. The aim of this work was to fabricate and characterize the self-healing microcapsules containing bituminous rejuvenator with nano-inorganic/organic hybrid shells. The shell had a two-layer structure: the inside layer material was the cross-linked methanol modified melamine-formaldehyde (MMF) resin and the outside materials was composed of methanol modified MMF resin and nano-particles of calcium carbonate (nano-CaCO₃). The forming mechanism of the two-layer structure was described based on a twice-condensation process. Fourier transform infrared spectroscopy (FT-IR) and Energy Dispersive Spectroscopy (EDS) results confirmed the nano-inorganic/organic hybrid structure of shells. The ideal content of nano-CaCO₃ particles was optimized through the morphologies observation. The addition of nano-CaCO₃ particles did not greatly influence the mean size of microcapsules. On the contrary, the nano-CaCO₃ particles increased the shell thickness of microcapsules owing to the loosely composite structure of shells. Thermal stability tests showed that the microcapsules could survive in the bitumen with a temperature of 200 °C. Moreover, the microcapsules could resist a violent temperature change process without destruction attributing to the protection of nano-CaCO₃ particles. The nano-particles on microcapsules decreased the deformation possibility of shells tested by nanoindentation.

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