No abstract

In order to produce a high-viscosity asphalt and mixtures that can be used for ultra-thin overlays, high contents of Styrene–butadiene–styrene (SBS, 5%, 6%, 7%), styrene butadiene rubber (SBR, 1%, 2%, 3%) and micro carbon fiber (MCF, 0.8%) were used to modify conventional asphalt to prepare high-viscosity modified asphalt suitable for this purpose. The performance of the modified asphalts was evaluated by conventional index, kinematic viscosity, dynamic shear rheological test (DSR), multiple stress creep recovery test (MSCR), and bending beam rheometer test (BBR). The road performance of the modified asphalt mixtures was evaluated by high-temperature rutting, low-temperature bending, freeze-thaw splitting, fatigue, speckle, anti-skid, and water seepage tests. The results show that increasing the content of SBS can improve the high-temperature deformation resistance, low-temperature failure strain, kinematic viscosity, and viscosity toughness of modified asphalt, and the optimum content of SBS was 6%. SBR can improve the high-temperature performance, kinematic viscosity, and water damage resistance of modified asphalt, and the optimum dosage was 2%. Compared with 5% SBS-modified asphalt mixture, the dynamic stability, low-temperature failure strain, and freeze-thaw splitting strength ratio of 6% SBS + 0.8% MCF composite-modified asphalt mixture were increased by 48.7%, 24.7%, and 5.2% respectively. Compared with the 5% SBS-modified asphalt, the same characteristics of the 2% SBR + 5% SBS + 0.8% MCF composite-modified asphalt increased by 127.1%, 13.5%, and 5.5%, respectively. Compared with 5% SBS-modified asphalt, the fatigue performance of 6% SBS + 0.8% MCF-modified asphalt was improved by 32.2%. The kinematic viscosity of 6% SBS + 0.8% MCF and 5% SBS + 0.8% MCF + 2% SBR modified asphalt met the performance requirements of high-viscosity asphalt and had excellent road performance. It can be applied to ultra-thin overlays to optimize its adhesion with the original pavement.

In order to produce high-viscosity and high-toughness asphalt for ultra-thin overlays, the conventional asphalt cement was modified with high-content SBS and micro carbon fiber (MCF). The performances of the modified asphalt were studied by tests of penetration, softening point, ductility, kinematic viscosity, multiple stress creep recovery (MSCR), and by dynamic shear rheometer (DSR) and bending beam rheometer (BBR). Mixture properties were studied by tests of rutting, low-temperature bending, freeze–thaw splitting, four-point bending fatigue and dynamic modulus. The results reflect that the addition of MCF could enormously improve the high- and low-temperature properties, increase the viscosity of asphalt, and improve the toughness of asphalt. When SBS content was 6%, with the increase of MCF content, G*/sin δ and R values first increased and then decreased, and the Jnr value first decreased and then increased. When MCF content was 0.8%, the overall performance was best. Adding MCF into an asphalt mixture or increasing the content of SBS improved the rutting resistance, low-temperature crack resistance, water stability, and fatigue performance of the asphalt mixture. At the same temperature and frequency, there was little difference in phase angle between the 6%SBS + 0.8%MCF and 5%SBS + 0.0%MCF modified asphalt mixtures, and the dynamic modulus was slightly higher over the whole range. It can be concluded that the addition of SBS and MCF can enormously enhance the viscosity and toughness of asphalt. The viscosity of the 6%SBS + 0.8%MCF modified asphalt met the performance requirements of high-viscosity asphalt. When used for ultra-thin overlays, it had great road service performance and met the application requirements.

With the increase of expressway construction in seasonal frozen soil region, the freeze-thaw problem of subgrade soil has attracted more and more attention [...]

An optical correlator plays a major role in optical information processing and computing. As the technology progresses, various schemes for optical correlation have been proposed. Basically, almost all these schemes can be classified into either VanderLugt or joint transform types. We discuss the peak intensity performance of the VanderLugt correlator (VLC) and the joint transform correlator (JTC). The analysis is carried out with the same illumination and optimum spatial filters. Objects embedded in random noise and multiple input objects are considered. For the case of simple input objects (i.e., correlation with the reference image), the JTC offers a higher correlation peak intensity than the VLC. For the case of objects embedded in random noise, the correlation intensity of the JTC monotonically decreases as a function of noise, whereas the peak intensity of the VLC is independent of noise. For multiobject cases, the correlation intensity of the JTC is inversely proportional to N, and the correlation intensity is unchanged.