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This research investigated a pavement system on steel bridge decks that use epoxy resin (EP) bonded ultra-high performance concrete (UHPC). Through FEM analysis and static and dynamic bending fatigue tests of the composite structure, the influences of the interface of the pavement layer, reinforcement, and different paving materials on the structural performance were compared and analyzed. The results show that the resin bonded UHPC pavement structure can reduce the weld strain in the steel plate by about 32% and the relative deflection between ribs by about 52% under standard axial load conditions compared to traditional pavements. The EP bonding layer can nearly double the drawing strength of the pavement interface from 1.3 MPa, and improve the bending resistance of the UHPC structure on steel bridge decks by about 50%; the bending resistance of reinforced UHPC structures is twice that of unreinforced UHPC structure, and the dynamic deflection of the UHPC pavement structure increases exponentially with increasing fatigue load. The fatigue life is about 1.2 × 107 cycles under a fixed force of 9 kN and a dynamic deflection of 0.35 mm, which meets the requirements for fatigue performance of pavements on steel bridge decks under traffic conditions of large flow and heavy load.

There is a limitation to apply air content in fresh concrete as the only index to pre-control frost resistance of cast-in-place concrete. By using an air void analyzer (AVA), the research investigated the influence laws of factors including water-cement ratio, addition amount of fly ash, vibration time, and time-dependent behaviors on a series of characteristics of fresh cement mortars. These characteristics include content, spacing factor, specific surface area (SSA), and size of air voids. The results demonstrated that when the air content was in the range of 7≈8%, the water-cement ratio insignificantly influenced the air-void structure. As fly ash can adsorb the air void, so its addition substantially reduced the content of large air voids and make the size distribution of voids more uniform. Compared with poker vibration, high-frequency vibration exhibited better effects in more uniformly distributing the air voids in the mixture. As large air voids escaped and split, the air content decreased, which was in favor of reducing the air-void size and the air-void spacing factor; Air-void structure in the mixture underwent complex change over time. On the whole, the air-void structure showed the following change trend: small air voids combined to large ones, air voids escaped, the number of air voids and the air-void SSA declined, and the air-void spacing factor enlarged. Therefore, while preparing concrete in practical engineering, it is particularly necessary to consider the adsorption effect of admixture, the time-delay effect of air-entraining agents, and the time-dependent behaviors of air voids, so as to control air-void parameters of hardened concrete.

With the advent and development of Industry 4.0 and 5.0, manufacturing modes have changed and numerous newly complicated and integrated village-level industrial parks have emerged in the Southeast of China, where several enterprises are gathered in the same multistory building. The number of floors and surrounding enterprises can have an impact on accident risk. To reduce the overall risk level of industrial parks, the layout of enterprises with different risks needs to be well designed and optimized. However, to date, limited studies have been conducted to emphatically consider safety and optimize the enterprise layout at an industrial area level, and most studies focus on the cost of the layout. Therefore, this study proposed three biobjective mathematical optimization models to obtain the trade-off between minimizing risk and maximizing rental profit. Risk factors include the enterprise location and the association risk; the enterprise inherent safety risks are not considered. To solve this problem, a specific linearization strategy was proposed and an epsilon-constraint method was applied to obtain Pareto-optimal solutions. Subsequently, an industrial park in Shunde, China, was considered as a case study to verify the performance of the proposed models and methods. Finally, a sensitivity analysis of critical parameters was conducted. The critical factors influencing the objective functions were also analyzed to provide valuable managerial insights.

Fatigue cracks are main damages to steel bridge deck pavement with thermosetting epoxy asphalt. By combining a high-toughness resin material with fiber woven fabrics, this study formed an ultrathin overlay of fiber-reinforced high-toughness resin to improve cracking resistance of pavement. Through theoretical measurement and bending test, this research studied change laws of bending and tensile properties of epoxy asphalt concrete after fiber reinforcement and analyzed bending strength and the maximum failure strain of beams at different temperatures. Moreover, the reinforcing effects of different fibers were discussed. It is found that bending strength, maximum failure strain, and stiffness modulus of the beams with epoxy asphalt are improved after fiber reinforcement. With the decrease of temperature, after fiber reinforcement, the mode of bending failure of the epoxy asphalt mixture (EAM) changes from brittle fracture into shear failure, accompanied with significant yield phenomenon. Furthermore, organic carbon fiber is sensitive to influences of temperature, while glass fiber is least sensitive to temperature.

To better understand thermal behaviors, combustion kinetic characteristics and dynamic releasing processes of gaseous products of four components separated from asphalt binder, thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) tests were conducted on each component at different heating rates, and both differential and integral methods were utilized to discuss their combustion kinetics characteristics, respectively. Results indicate that combustion processes of four components include the volatilization of light components in stage 1 and the combustion of charring layer in stage 2. Main mass losses of saturates and aromatics occur in stage 1, but the mass loss percentages of resins and asphaltenes in the two stages are almost equal. Thermal stability of four components is successively increased from saturates to aromatics, resins and asphaltenes. Also, there is a lag of combustion process due to more incomplete decomposition of each component at a higher heating rate. Temperature range of each combustion stage is widened as the heating rate is raised. Thermal decompositions of resins and asphaltenes are less affected by the heating rate than those of saturates and aromatics. Additionally, activation energy in each component combustion stage is calculated and collated by differential and integral methods, which are suitable to discuss combustion kinetics characteristics of four components and evaluate their thermal stability. Finally, the release rate and amount of gaseous products are increased at a higher heating rate. Combustion properties of asphalt materials are further understood at the component level.

Background The wishbone flower or Torenia fournieri Lind., an annual from tropical Indochina and southern China, is a popular ornamental plant, and many interspecific (T. fournieri × T. concolor) hybrid lines have been bred for the international market. The cultivated lines show a pattern of genetic similarity that correlates with floral color which informs on future breeding strategies. This study aimed to perform genetic analysis and population structure of cultivated hybrid lines comparing with closely related T. concolor wild populations. Methods We applied the retrotransposon based iPBS marker system for genotyping of a total of 136 accessions from 17 lines/populations of Torenia. These included 15 cultivated lines of three series: Duchess (A, B, C); Kauai (D, E, F, G, H, I, J); Little Kiss (K, L, M, N, P) and two wild T. concolor populations (Q and R). PCR products from each individual were applied to estimate the genetic diversity and differentiation between lines/populations. Results Genotyping results showed a pattern of genetic variation differentiating the 17 lines/populations characterized by their specific floral colors. The final PCoA analysis, phylogenetic tree construction, and Bayesian population structural bar plot all showed a clear subdivision of lines/populations analysed. The 15 cultivated hybrid lines and the wild population Q that collected from a small area showed the lowest genetic variability while the other wild population R which sampled from a larger area had the highest genetic variability. Discussion The extremely low genetic variability of 15 cultivated lines indicated that individual line has similar reduction in diversity/heterozygosity from a bottleneck event, and each retained a similar (but different from each other) content of the wild genetic diversity. The genetic variance for the two wild T. concolor populations could be due to our varied sampling methods. The two wild populations (Q, R) and the cultivated hybrid lines (I, K, M, N, P) are genetically more closely related, but strong positive correlations presented in cultivated lines A, C, E, M, and N. These results could be used to guide future Torenia breeding. Conclusions The genetic variation and population structure found in our study showed that cultivated hybrid lines had similar reduction in diversity/heterozygosity from a bottleneck event and each line retained a similar (but different from each other) content of the wild genetic diversity, especially when strong phenotypic selection of floral color overlaps. Generally, environmental factors could induce transposon activation and generate genetic variability which enabled the acceleration of the evolutionary process of wild Torenia species. Our study revealed that wild Torenia populations sampled from broad geographic region represent stronger species strength with outstanding genetic diversity, but selective breeding targeting a specific floral color decreased such genetic variability.

Through laboratory testing, this research studied the connection between air-void structures of hardened concrete and fresh concrete and discussed the effects of the air-void structure on the salt-frost durability of the concrete. The results demonstrate that, in comparison with fresh concrete, the air-void spacing factor shows a close correlation with hardened concrete air-content and decreases in the form of a power function as the air-content increases. When the fresh concrete air-content is more than 6% and the hardened concrete air-void spacing factor is less than 0.18 mm, the influence of parameters of air-void structure on the salt-frost resistance of the concrete reduces. The air-void spacing factor more significantly affects the salt-frost resistance of the concrete compared with air content and the correlation reaches 0.93. Therefore, air-content and air-void spacing factor are recommended for dual control.

This study discussed influences of surface states of concrete on salt-frost durability. By using the Capillary suction of Deicing solution and Freeze-thaw test method(CDF), the effects of factors, such as solution saturation in capillary, surface property and load coupling were compared and analyzed. It is found that drying shrinkage exerts greater effects on salt-frost resistance of the concrete in comparison with solution saturation in capillary. According to the CDF test standard recommended by RILEM, the salt-frost test results of the surface formed with the partitions in the laboratory overestimate salt-frost resistance of the concrete in the actual situation. Scaled mass of the top surface of the molded concrete due to salt frost is about 50% larger than that of the surface formed with the partitions. Coupling effects of repeated load and salt-freezing cycles can aggravate salt-frost damages of the concrete. Keywords: Salt-freezing cycle, Saturation, Surface property, Load coupling

Impatiens macrovexilla Y. L. Chen is a potential ornamental herbaceous plant originated from a relatively small area of subtropical Karst region in southern China, and natural populations of this species presented strong adaptability to a range of environmental conditions, with strong horticultural characteristics including bright colour, large flowers, early flowering, long flowering, and floriferousness. Overall, these adventive traits are significant for future selective breeding. Using a ‘jumping gene’ based or retrotransposon-based Inter-Primer Binding Site (iPBS) marker system to evaluate the genetic variation of nine I. macrovexilla populations collected from contrasting environments. The electrophoretic patterns of the PCR products produced for all the accessions were applied to evaluate the genetic diversity and differentiation between populations. The genotyping results distinguished all the 91 individual accessions in nine I. macrovexilla populations from varied microclimates, and population G was separated as a particular variety (I. macrovexilla var. yaoshannensis) which agrees with former botanical classifications about this species. Results from the AMOVA analysis showed that the greatest genetic variation (77 %) was observed within populations whilst 23 % was recorded among populations, indicating a wide range of biotypes at each location where germplasm collected. Results from our PCoA analysis, the phylogenetic dendrogram, and the Bayesian clustering analysis showed obvious subdivision among populations analyzed. The genetic relationships for population G (Jinxiu) and population H (Gantang) were the most different from each other and showed the highest genetic distance of 0.254. Characteristics of specific traits for each population and the genetic relationships of these populations could be utilized in optimizing potential parental candidate for cross combinations. Variations of the genetic pattern and the relationships among and within the populations will impact profoundly on our selective breeding of the species in the future.

The presence of negative bending moments at the top of a continuous beam bridge can facilitate the sawing of false seams. The concrete bridge deck and its asphalt pavement will therefore develop transverse fatigue cracks under long-term cyclic traffic loads. This paper aims at preventing reflective cracks from forming in such asphalt pavements. The structure and materials used in crack prevention based on a composite stress-absorbing layer (CSAL) consisting of a geotextile and an asphalt gravel seal coat were investigated. The properties of polypropylene (PP) geotextiles were evaluated by means of differential scanning calorimetry, thermogravimetric analysis, thermal shock tests, etc. Adhesion, shear, and tensile tests were used to study the influences of factors such as the type, amount of asphalt materials, and construction temperature on the bonding performance of the pavement interface. Texas overlay tests were also carried out to explore the anti-reflective cracking and anti-fatigue performance of different pavement structures including an asphalt rubber stress-absorbing membrane interlayer (ARSAMI) and a CSAL. The results show that the PP geotextile has a melting point of about 166 ℃, a glass-transition temperature in the range of –20 to –10 ℃, and a thermal decomposition temperature of about 400 ℃. In addition, it retains good strength and deformability when subjected to thermal shock at 180 ℃, and it has high thermal stability. The modified asphalt has the highest adhesion strength to concrete slabs, followed by ordinary asphalt and then emulsified asphalt. The temperature state of the bonding layer is not sensitive to the bond strength of the bridge deck paving structure. The asphalt mixture waterproofs the surface after paving. The adhesive stress-absorbing layer imparts a secondary heating effect, thereby ensuring interface adhesion. Using a pavement structure with a CSAL can enhance resistance to reflective cracking at a low temperature by more than 5 times compared to the case not taking preventative measures. Its resistance to reflective cracking under a deformation amplitude of 2 mm at the room temperature (20 ℃) is also slightly better than that of the ARSAMI. Hence, CSALs have promising prospects for use in crack prevention.

Fatigue cracking is a typical defect in steel deck pavements. To reduce, or even eliminate, fatigue cracking in orthotropic steel deck pavements, a new-generation, cold-mix, high-toughness resin (CHR) for steel deck pavements was prepared by introducing a flexible chain into the molecular structure of cured epoxy resin based on the principle of action of a simultaneous interpenetrating polymer network (IPN). Meanwhile, the strength and durability of the CHR were studied experimentally. The results show that, with increased dosage of active toughening agent, the microstructure of CHR transitioned from a sea-island structure to an interpenetrating network structure. In addition, the transparency of CHR gradually increased and the tensile strength gradually decreased while the elongation at break gradually increased. The reaction orders of Z15-G1 and Z15-G2 CHRs were 0.918 and 0.921 and their apparent activation energies were 47.60 kJ/mol and 50.74 kJ/mol, respectively. The basic pavement performances of the Z15-G1 and Z15-G2 CHR mixtures both satisfied the technical index requirements of a steel deck pavement. Moreover, four-point bending fatigue test results show that the fatigue life of the Z15-G1 CHR mixture was much longer than that of an epoxy asphalt mixture.

Epoxy asphalt concrete is widely used for long-span steel bridge deck pavement in China. Because of the heavy traffic load and extreme climatic conditions, epoxy asphalt deck pavement tends to develop cracks, debonding, and potholes and needs reconstructing typically after 5 to 10 years. Research was performed on the cracking mechanism under both traffic and thermal loads, with the aim of finding the best sealing material. The performances of various crack-sealing materials, including workability, mechanical property, and durability, were evaluated. Test methods such as the simplified penetration ability test and bending fatigue test were employed for rating the crack-sealing materials. Experimental results revealed that the traditional crack-sealing materials, such as bitumen modified with styrene–butadiene–styrene, rubber bitumen, bitumen emulsion, and solvent bitumen, cannot meet the requirements for repairing epoxy asphalt on long-span bridge decks because of the low penetration ability and low adhesive strength. Results showed that cracks could be repaired well with epoxy resin–sealing materials, which showed great penetration ability, high bond strength, large deformation capacity, and short curing time.

The epoxy asphalt (EA) binder has been widely used for the pavement on the steel plate deck and in tunnels. In this study, horizontal burning and limiting oxygen index (LOI) were conducted to evaluate the effects of mixed decabrombromodiphenyl ethane (DBDPE) and antimony trioxide (Sb2O3) on flame retardancy for epoxy asphalt binder. The influence of DBDPE/Sb2O3 on the rotational viscosity, the thermal and mechanical properties of epoxy asphalt binder was evaluated by thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), and tensile test. The addition of DBDPE/Sb2O3 reduces the horizontal burning classification of epoxy asphalt binder from FH-2 to FH-1, and the LOI values of EAs is also significantly increased. The addition of flame retardants has no significant effect on the rotational viscosity of EA in the initial stage of cure reaction. TG results show that the presence of DBDPE/Sb2O3 improves the thermal stability of the epoxy asphalt binder. The addition of DBDPE/Sb2O3 has little effect on the tensile strength of the epoxy asphalt binder. However, the elongation at break of flame-retarded EAs is lower than that of the neat EA.

A series of interpenetrating polymer networks (IPNs) based on epoxy (EP) resin and polyurethane (PU) prepolymer derived from soybean oil-based polyols with different mass ratios were synthesized. The structure, thermal properties, damping properties, tensile properties, and morphology of soybean oil-based PU/EP IPNs were characterized by Fourier-transform infrared spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), universal test machine, and scanning electron microscopy (SEM). DSC and DMA results show that the glass transition temperature of the soybean oil-based PU/EP IPN decreases with the increase of PU prepolymer contents. Soybean oil-based PU/EP IPNs have better damping properties than that of the pure epoxy resin. The tensile strength and modulus of PU/EP IPNs decrease, while elongation at break increases with the increase of PU prepolymer contents. SEM observations reveal that phase separation appears in PU/EP IPNs with higher PU prepolymer contents.

Amino-functionalized multiwalled carbon nanotubes (MWCNT-NH2s) as nanofillers were incorporated into diglycidyl ether of bisphenol A (DGEBA) toughened with amine-terminated butadiene–acrylonitrile (ATBN). The curing kinetics, glass-transition temperature (Tg), thermal stability, mechanical properties, and morphology of DGEBA/ATBN/MWCNT-NH2 nanocomposites were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis, a universal test machine, and scanning electron microscopy. DSC dynamic kinetic studies showed that the addition of MWCNT-NH2s accelerated the curing reaction of the ATBN-toughened epoxy resin. DSC results revealed that the Tg of the rubber-toughened epoxy nanocomposites decreased nearly 10°C with 2 wt % MWCNT-NH2s. The thermogravimetric results show that the addition of MWCNT-NH2s enhanced the thermal stability of the ATBN-toughened epoxy resin. The tensile strength, flexural strength, and flexural modulus of the DGEBA/ATBN/MWCNT-NH2 nanocomposites increased increasing MWCNT-NH2 contents, whereas the addition of the MWCNT-NH2s slightly decreased the elongation at break of the rubber-toughened epoxy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40472.

Today, serious deterioration has occurred on concrete deck pavement in China. One reason for the problem is the interface slippage between the concrete deck and the pavement. An efficient interface treatment can solve the problem. The interface treatment contains two aspects: the concrete deck treatment and the adhesion layer. Concrete deck treatment can change the physical form of the concrete deck and is more reliable in improving the shear performance of the concrete deck pavement. This paper summarizes and presents a comparison through physical form analysis and indoor tests of three kinds of concrete deck treatment: manual work treatment, milling treatment and sandblast treatment. The test results show that milling treatment can improve shear performance more than sandblast treatment. This paper suggests a more reliable way to improve the shear performance of concrete deck pavement.