Epoxy asphalt concrete (EAC) is a widely used steel bridge deck pavement (SBDP) material. Due to the curing reaction, the EAC-based material needs a long curing period before opening to traffic, ...which in an inconvenience in the construction of SBDP. This study developed a cold mix high-early-strength (CHES) epoxy asphalt through the design of a compatilizer and curing agent system. The optimum formula of CHES epoxy asphalt was determined through a series of laboratory tests. By comparison of the performances of CHES EAC and some conventional EACs for SBDP, it was found that the developed CHES epoxy asphalt can significantly reduce the curing period, and the pavement performance of CHES EAC is, overall, excellent for application in SBDP. In addition, the sufficient allowable construction duration shows that the CHES EAC has a good construction workability.
Ductile Cu–Al–Mn shape memory alloys obtain the damping capacity through the movement of martensite boundaries. To reduce the number of vacancies at martensite boundaries can improve their damping ...capacity. Our results showed that Ni alloying could remarkably suppress the vacancy movement during the process of cooling from high temperature and heating as well as ageing. The Cu-18.0Al-8.4Mn-2.5Ni alloy showed remarkably higher damping capacity than the Cu-18.0Al-9.4Mn alloy did due to the reduced vacancies at martensite boundaries by the Ni alloying, regardless of the direct quenching, up-quenching, and step-quenching. The occurrence of martensitic stabilization could rationalize the lower improvement of damping capacity in the up-quenched Cu-18.0Al-9.4Mn alloy. The present results also further confirmed that the original number of vacancies at the martensite boundaries determined the occurrence of martensitic stabilization.
Asphalt rubber shows good road performance. However, the compatibility and aging problems of asphalt rubber limit its application. The improvement of the solubility of crumb rubber in asphalt was ...investigated in this research, and the mechanism of its aging effect on the rheological properties of activated asphalt rubber was studied. First, the crumb rubber was activated by using a sodium hypochlorite (NaClO) solution, and the pore characteristics and microstructure of the activated crumb rubber were analyzed. Second, the influence of the crumb rubber’s activation characteristics on the rheological properties of the asphalt rubber before and after aging was analyzed. Finally, the aging mechanism of the activated asphalt rubber was revealed at a microscopic level. The results showed that with the increase in the activation degree, the pore characteristics of the crumb rubber decreased first and then increased. The surface stacking structure of the crumb rubber increased, and a dense gel film gradually formed. The asphalt rubber prepared by the activated crumb rubber had better rheological properties and had a more significant effect under higher stress conditions. This may have been due to the activation of the crumb-rubber surface, forming oxygen-containing functional groups, which, in turn, increased the combination of the crumb rubber and the asphalt. In addition, the activation degree and aging effect of crumb rubber can reduce the large-particle-size molecule (LMS) content of activated asphalt rubber. There is a significant correlation between LMS content and rheological properties, and LMS content can be used to predict the rheological properties of asphalt rubber.
Compared with hot mix asphalt, warm mix asphalt ( WMA) has inferior adhesion performance, and ultraviolet (UV) aging will further weaken the adhesion performance of WMA. There are, however, few ...investigations on the aging mechanism under conditions of single UV radiation, and the majority of current research on UV aging is conducted under the combined action of UV radiation and oxygen. In this paper, an indoor accelerated experimental equipment for UV aging was developed, and two experimental schemes of oxygen isolation condition and light-oxygen coupling condition were designed. The developed UV aging tests were carried out on WMA this for 0–50–100–150 and 200 h. The nano adhesion properties were studied by atomic force microscopy ( AFM) and gel permeation chromatography ( GPC) experiments. The characterization method of WMA nano adhesion performance was proposed using correlation analysis. In addition, the nonlinear differential equations between nano-indexes and aging time were established by the Verhulst model. The results showed that the generation of microcracks and the increase of large molecular weight during UV aging will decrease WMA adhesion performance, and the degradation is more significant under the light-oxygen coupling conditions. Moreover, the correlation coefficients between large molecular weight and nano-adhesion under two UV aging conditions were higher than 0.90, showing that large molecular weight could characterize the degradation of nano-adhesion of WMA after UV aging. The saturation characteristics of the honeycomb structure area ratio were prominent, and the coefficient of determination of the nonlinear equations were higher than 0.93 for both two UV aging conditions. The aging model can be used to accurately characterize and predict the WMA UV aging state through the variation of honeycomb structure area ratio.
The purpose of this study was to investigate the adhesive properties of polyphosphoric acid compounded SBS (PPA/SBS) modified asphalt. Three base asphalt binders, one SBS, one dibutyl phthalate ...(DBP), one furfural extraction oil, and two polyphosphoric acids (PPA), were used to produce the modified binders. The adhesive properties tested in this study included contact angle, cohesive work, adhesive work, and peak area ratio. Cohesive work and adhesive work indicators were calculated from the contact angle, the contact angle between PPA/SBS modified asphalt and three liquids (distilled water, glycerin, formamide) were tested by the contact angle tester, and the peak area ratio of the microscopic adhesion performance index by AFM. The relation between the microscopic adhesion performance characterization method (peak area ratio) and the macroscopic adhesion performance index (cohesive work, adhesion work) was established. The test results indicated that the PPA/SBS modified asphalt had the highest cohesive work and adhesion work under the conditions of 0.5% PPA, 1% DBP, 1.5% extracted oil, and 3.5% SBS, which was clearly greater than the original SBS modified asphalt, while the peak area ratio was consistent with the cohesive work and adhesive work, in which the correlation coefficient between the peak area ratio and cohesive work was 0.77788, and that between the peak area ratio and adhesion work was 0.87203. We recommend adopting the peak area ratio to characterize PPA/SBS modified asphalt’s microscopic adhesion properties.
Egineering running experience shows that with the increase of the operating voltage of the transmission line, the lightning trip rate is increasing. According to theoretical calculation ， UHV ...transmission lines should be provided with full lightning protection characteristics；however，running experience shows that the lightning withstand level of UHV transmission lines is high，not completely lightning protection; it puts forward higher requirements for lightning protection design of UHV transmission line in China. UHV transmission line is mainly against direct lightning stroke characteristics， one is caused by lightning counterattack trip，the other is the shielding failure of lightning around the line to strike the wound caused by the wire. The lightning fault type identification is based on the micro topography of UHV transmission tower，accumulation of historical data，the development of a more targeted and high voltage transmission line lightning protection scheme is of great significance. In this paper, a real-time identification system based on UV detection technology, which has high accuracy and fast response time, is proposed for lightning fault types of UHV transmission lines, the systems use ultraviolet light to realize online detection of high-voltage transmission line tower nearby lightning, can effective observation tower near lightning discharge, and it has the characteristics of continuous detection, longdistance, no power supply, no contact and no disassembly, it provides an advanced technology for the detection of lightning discharge in UHV transmission line.
Self-powered ZnO/perovskite heterostructured ultraviolet （UV） photodetectors （PDs） based on the pyro-phototronic effect have been recently reported as a promising solution for energy-efficient, ...ultrafast-response, and high-performance UV PDs. In this study, the temperature dependence of the pyro-phototronic effect on the photo-sensing performance of self-powered ZnO/perovskite heterostructured PDs was investigated. The current responses of these PDs to UV light were enhanced by 174.1% at 77 K and 28.7% at 300 K owing to the improved pyro-phototronic effect at low temperatures. The fundamentals of the pyro-phototronic effect were thoroughly studied by analyzing the charge- transfer process and the time constant of the current response of the PDs upon UV illumination. This work presents in-depth understandings about the pyro- phototronic effect on the ZnO/perovskite heterostructure and provides guidance for the design and development of corresponding optoelectronics for ultrafast photo sensing, optothermal detection, and biocompatible optoelectronic probes.
A higher yield strength of parent phase in shape memory alloys is necessary for achieving a higher recovery stress. Fe alloying combined with grain boundary engineering (GBE) were investigated to ...improve the yield strength of ductile Cu17Al11Mn alloy. Results showed that the precipitation of low strength ductile α phase through the GBE remarkably enhanced the ductility while not obviously reducing the yield strength in the step-quenched Cu17Al11Mn4.5Fe alloy due to the precipitation of nanoscale κ phase inside them. Compared to the Cu17Al11Mn alloy, a 200 MPa higher yield strength and better ductility could be realized in the Cu17Al11Mn4.5Fe alloy step-quenched into two-phase region between 993 K and 1003 K. The recovery strains of ∼6.5% could be guaranteed in the step-quenched Cu17Al11Mn4.5Fe alloy. The Fe alloying combined with the GBE through the step-quenching will be a direction for developing ductile CuAlMn based alloys with both high strength and recovery strain.
To know differences in oxidation resistance and mechanical properties between Al2O3-forming and SiO2-forming austenitic stainless steels, oxidation behavior and mechanical properties were ...investigated in Fe-20Ni-14Cr-3Al-1Nb-0.1C, Fe-20Ni-14Cr-5Si, and Fe-20Ni-14Cr-3Si-1Nb-0.1C (in wt%) steels. The results showed that the oxidation resistance of Fe-20Ni-14Cr-3Si-1Nb-0.1C steel was comparable to that of Fe-20Ni-14Cr-3Al-1Nb-0.1C steel at 1023–1073 K but poor at 1123 K. The addition of Nb could improve the oxidation resistance in the SiO2-forming steels. The solution-treated and oxidized SiO2-forming steels showed remarkably higher ductility but lower yield strength than the Al2O3-forming steel did. The easier twinning and fewer precipitates were responsible for the remarkably higher ductility in the SiO2-forming steels.
•Oxidation resistance of the AFA steel and SFA steels were comparable at 1023–1073 K.•Continuous SiO2 scales were observed at the metal/oxide interface.•The addition of Nb could improve the oxidation resistance in the SFA steel.•The solution-treated and aged SFA steels showed a higher ductility but a lower strength than the AFA steel did.
We realized a good combination of shape memory effect and mechanical properties in a hot-rolled Fe47.7Mn15.5Co9.8Cr10.8Ni5.1Si11.1 high entropy alloy (HEA) by Si alloying and proper heat treatment to ...guarantee a low density of annealing twin boundaries. Its maximal recovery strain of 5.7% reached the level that conventional FeMnSi-based and Co-based shape memory alloys (SMAs) showing the same FCC to HCP martensitic transformation can realize. It showed a better combination of ultimate tensile strength and fracture strain than the reported CoCrFeNiMn-based HEAs with FCC matrix did. This result showed that to marry the shape memory effect with the excellent mechanical properties will be a promising direction for developing novel HEAs.
•A good combination of SME (RSmax=5.7%) and excellent mechanical properties was obtained in a CoCrFeNiMnSi HEA.•This excellent combination provides a promising direction for developing the novel HEAs.•Si alloying, proper heat treatment to guarantee a low density of annealing TBs were responsible for these good performances.
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