This page has only limited features, please log in for full access.
In order to improve the safety of the tunnel asphalt pavement in the event of a fire, and reduce the deterioration of the low temperature crack resistance of the asphalt by the flame retardant. The research uses aluminum hydroxide (ATH) as a smoke suppressant, diethyl aluminum hypophosphite (ADP) as a flame retardant, and halloysite nanotubes (HNTs) as a synergist to modified styrene-butadiene-styrene block copolymer (SBS) modified asphalt (MA). First, the content of ATH, ADP, and HNTs was used as the response variable. The physical properties (Penetration, Softening point, Ductility) and static flame retardant properties (Limiting oxygen index meter, Ignition point) of the asphalt modified by nanocomposite flame-retardant (HNTs-CFRMA) were the response variables. The response surface methodology was used to design the test, and regression models were established to analyze the influence of flame retardants on the performance of asphalt. Then, comprehensively considering the effects of physical properties and flame retardant properties, the normalized desirability function was used to perform a multi-objective optimization design on the components of the nanocomposite flame retardant modifier to obtain the best flame retardant formula. Finally, the rheological properties of MA, conventional flame-retardant modified asphalt (CFRMA), and HNTs-CFRMA were tested based on Dynamic shear rheometer, Multiple stress creep test, Force ductility tester, and Bending beam rheometer. The performance of flame-retardant and smoke suppression were tested by the Cone calorimeter tests. The result shows that ATH, ADP, and HNTs can enhance the high temperature performance of asphalt, reduce the penetration. The addition of HNTs can increase significantly the softening point and reduce the deteriorating effect of flame retardants on the low temperature performance of asphalt; the addition of ATH and HNTs can improve significantly the flame retardancy of asphalt. Based on the desirability function of power exponent, the formulation of the nanocomposite flame retardant with better physical properties and flame retardant properties is ATH:ADP:HNTs = 3:5:1, and the total content is 9 wt%. Nanocomposite flame retardants can improve obviously the high temperature rheological properties of asphalt. The rutting factor and the cracking factor of HNTs-CFRMA improve markedly, and the irrecoverable creep compliance is reduced, compared with MA and CFRMA. Nanocomposite flame retardant can make up for the deterioration of conventional flame retardants on asphalt’s low temperature performance. At the same time, it has better flame-retardant performance and smoke suppression performance.
Jiaqi Li; Zhaoyi He; Le Yu; Lian He; Zuzhen Shen. Multi-Objective Optimization and Performance Characterization of Asphalt Modified by Nanocomposite Flame-Retardant Based on Response Surface Methodology. Materials 2021, 14, 4367 .
AMA StyleJiaqi Li, Zhaoyi He, Le Yu, Lian He, Zuzhen Shen. Multi-Objective Optimization and Performance Characterization of Asphalt Modified by Nanocomposite Flame-Retardant Based on Response Surface Methodology. Materials. 2021; 14 (16):4367.
Chicago/Turabian StyleJiaqi Li; Zhaoyi He; Le Yu; Lian He; Zuzhen Shen. 2021. "Multi-Objective Optimization and Performance Characterization of Asphalt Modified by Nanocomposite Flame-Retardant Based on Response Surface Methodology." Materials 14, no. 16: 4367.
In this study, the semicircle three-point bending tests of ordinary asphalt concrete and basalt fiber asphalt concrete were carried out and acoustic emission parameters were collected during the test. The differences of the characteristics of acoustic emission parameters between basalt fiber asphalt concrete and ordinary asphalt concrete were analyzed, and the damage stages were divided based on the variation of acoustic emission parameters; Rise Angle and Average Frequency were introduced to study the cracking mode and crack resistance mechanism of asphalt concrete with basalt fiber. The results show that the acoustic emission parameters can well represent the toughening and crack resistance effect of basalt fiber in asphalt concrete, and the damage stages can be divided into three stages: microcrack initiation stage, fracture stage, and residual stage. The duration of the fracture stage and the load resistance time of the specimen were greatly prolonged. The proportion of shear events in the whole failure process increased greatly after the basalt fibers were added, especially in the fracture stage, which reduced the tensile failure tendency of the specimens, and thus improved the bending and tensile performance of the specimens and played a toughening and crack resistance role in the fracture stage.
Kang Yang; Zhaoyi He; Dongxue Li; Hao Xu; Lin Kong. Experimental Study on Basalt Fiber Crack Resistance of Asphalt Concrete Based on Acoustic Emission. Materials 2021, 14, 4096 .
AMA StyleKang Yang, Zhaoyi He, Dongxue Li, Hao Xu, Lin Kong. Experimental Study on Basalt Fiber Crack Resistance of Asphalt Concrete Based on Acoustic Emission. Materials. 2021; 14 (15):4096.
Chicago/Turabian StyleKang Yang; Zhaoyi He; Dongxue Li; Hao Xu; Lin Kong. 2021. "Experimental Study on Basalt Fiber Crack Resistance of Asphalt Concrete Based on Acoustic Emission." Materials 14, no. 15: 4096.
In this study, asphalt concrete specimens were subjected to a semicircle bending test at −10 °C to simulate the process of the development of cracks in asphalt concrete at low temperature. The acoustic emission parameters were collected during the test, the variation characteristics of acoustic emission parameters were analyzed, and the peakedness value was introduced to evaluate the damage of asphalt concrete. The dynamic evolution of fracture development was analyzed by periods with acoustic emission source location. The results indicate that the damage of asphalt mixtures shows an obvious brittle characteristic at low temperature, acoustic emission signals mainly originate from the crack damage caused by tensile stress, and the strength and number of signals can reflect the degree of crack development. Based on acoustic emission parameters and load curves, the cracking damage of asphalt concrete at low temperature in this study can be divided into three periods: a calm period, a stable development period, and a rapid fracture period. The crack point occurred and propagated upward rapidly in the rapid fracture period. During this period, acoustic emission parameters such as ringing count, acoustic emission energy, and amplitude increased suddenly; furthermore, the peakedness value reached its peak in this period and corresponded well with the low-temperature damage of asphalt concrete. Acoustic emission source location technology can track position of crack points and the propagation path of cracks, reflecting the dynamic evolution process of asphalt concrete crack damage at low temperature.
Kang Yang; Dongxue Li; Zhaoyi He; Hanlin Zhou; Jiaqi Li. Study on Acoustic Emission Characteristics of Low-Temperature Asphalt Concrete Cracking Damage. Materials 2021, 14, 881 .
AMA StyleKang Yang, Dongxue Li, Zhaoyi He, Hanlin Zhou, Jiaqi Li. Study on Acoustic Emission Characteristics of Low-Temperature Asphalt Concrete Cracking Damage. Materials. 2021; 14 (4):881.
Chicago/Turabian StyleKang Yang; Dongxue Li; Zhaoyi He; Hanlin Zhou; Jiaqi Li. 2021. "Study on Acoustic Emission Characteristics of Low-Temperature Asphalt Concrete Cracking Damage." Materials 14, no. 4: 881.
The inflammability of asphalt road will promote fire spread in the tunnel and produce lots of toxic smoke. To improve the fire resistance of asphalt pavement, mineral powder flame retardants are generally replaced by flame retardants in equal amounts. In this study, the effects of the synergistic flame retardancy system of halloysite nanotubes (HNTs) and conventional flame retardants (CFR) on the flame retardancy performance and mechanism of asphalt were investigated. Firstly, the flame retardancy properties of the HNTs and CFR composite modified asphalt were investigated based on the Cleveland open cup method (COC), Limiting oxygen index meter (LOI), and Cone calorimeter tests (CCTs). Then, the flame retardancy mechanism of the modified asphalt was studied based on Thermogravimetric analyzer (TGA), Fourier-transform infrared (FTIR), and Scanning electron microscopy (SEM). The results show that adding HNTs could improve the flame retardancy of the CFR modified asphalt binder. When 1 wt % HNTs and 8 wt % CFR were used, the limiting oxygen index of asphalt increased by 40.1%, the ignition temperature increased by 40 °C, while the heat release rate, total heat release, the smoke production rate, total smoke release, and other parameters decreased with varying degrees. Based on TG, FTIR, and SEM, the targeted flame retardancy mechanism and synergistic effect of HNTs/CFR flame retardancy system were revealed and summarized as three stages: (1) Stage 1, aluminum hydroxide (ATH) absorbs heat through thermal decomposition and inhibits the decomposition of lightweight components in asphalt; (2) Stage 2, aluminum diethyl phosphate (ADP) decomposes and produces organic phosphoric acid, which catalyzes crosslinking and ring thickening of asphalt and the quenching effect of phosphorus free radicals to block the combustion; and (3) Stage 3, HNTs plays an important role in increasing the integrity and density of the barrier layer. In addition, the Al2O3 produced by the decomposition of ATH, the carbon layer formed by the ADP catalyzed pitch, and HNTs play a significant synergistic effect in the formation of the barrier layer. Thus, the combination of HNTs and CFR has been proved to be a prospective flame retardancy system for asphalt.
Yangwei Tan; Zhaoyi He; Xiang Li; Bin Jiang; Jiaqi Li; Yonggang Zhang. Research on the Flame Retardancy Properties and Mechanism of Modified Asphalt with Halloysite Nanotubes and Conventional Flame Retardant. Materials 2020, 13, 4509 .
AMA StyleYangwei Tan, Zhaoyi He, Xiang Li, Bin Jiang, Jiaqi Li, Yonggang Zhang. Research on the Flame Retardancy Properties and Mechanism of Modified Asphalt with Halloysite Nanotubes and Conventional Flame Retardant. Materials. 2020; 13 (20):4509.
Chicago/Turabian StyleYangwei Tan; Zhaoyi He; Xiang Li; Bin Jiang; Jiaqi Li; Yonggang Zhang. 2020. "Research on the Flame Retardancy Properties and Mechanism of Modified Asphalt with Halloysite Nanotubes and Conventional Flame Retardant." Materials 13, no. 20: 4509.
The accurate localization of an acoustic emission (AE) source is a vital aspect of AE nondestructive testing technology. A model of wave velocity attenuation caused by the extension of transmission distance is established to analyze the attenuation of AE wave velocities in concrete and thus improve the acoustic source localization accuracy from the perspective of modified velocity. In combination with the exhaustive and region localization methods, a region exhaustive localization method is established based on the modified wave velocity. The results indicate that the smaller the water–cement ratio, the larger the reference wave velocity, and the spatially dependent attenuation of wave velocity increase. Moreover, the larger the aggregate particle size, the larger the reference wave velocity, and the greater the attenuation of wave velocity with distance. For a propagation distance of 1000 mm, the AE wave velocity attenuation exceeds 50% compared with the AE velocity. The optimized localization method reduces the number of nodes calculated, thus improving the method’s accuracy when used for localization.
Dongxue Li; Kang Yang; Zhaoyi He; Hanlin Zhou; Jiaqi Li. Acoustic Emission Wave Velocity Attenuation of Concrete and Its Application in Crack Localization. Sustainability 2020, 12, 7405 .
AMA StyleDongxue Li, Kang Yang, Zhaoyi He, Hanlin Zhou, Jiaqi Li. Acoustic Emission Wave Velocity Attenuation of Concrete and Its Application in Crack Localization. Sustainability. 2020; 12 (18):7405.
Chicago/Turabian StyleDongxue Li; Kang Yang; Zhaoyi He; Hanlin Zhou; Jiaqi Li. 2020. "Acoustic Emission Wave Velocity Attenuation of Concrete and Its Application in Crack Localization." Sustainability 12, no. 18: 7405.
Hao Xiang; Wenwu Zhang; Peng Liu; Zhaoyi He. Fatigue–healing performance evaluation of asphalt mixture using four-point bending test. Materials and Structures 2020, 53, 1 .
AMA StyleHao Xiang, Wenwu Zhang, Peng Liu, Zhaoyi He. Fatigue–healing performance evaluation of asphalt mixture using four-point bending test. Materials and Structures. 2020; 53 (3):1.
Chicago/Turabian StyleHao Xiang; Wenwu Zhang; Peng Liu; Zhaoyi He. 2020. "Fatigue–healing performance evaluation of asphalt mixture using four-point bending test." Materials and Structures 53, no. 3: 1.
To solve the early rutting failure of asphalt pavement, the application of rock asphalt from Sichuan, China, based on anti-rutting performance, was studied. Preparations of North Sichuan rock asphalt (NS RA) and NS RA-modified asphalt mixture were elaborated in detail. Using Zhonghai AH-70 asphalt, Esso AH-70 asphalt, North American rock asphalt (NA RA) and NS RA, the performances of NS RA modified asphalt were researched based on index tests, Brookfield rotary viscosity test and bending beam rheometer test. A performance verification of NS RA-modified asphalt was carried out using rutting calculation, the rutting, indirect tensile fatigue, freeze–thaw split and small beam bending tests based on five kinds of selected gradations. The results indicated that in comparison with NA RA, the NS RA has a good modification effect as well. The NS RA can obviously improve the anti-rutting ability of the asphalt binder, and it can enhance its anti-aging performance as well. For the NS RA-modified asphalt mixture, it is feasible to determine the optimum NS RA content, based on its anti-rutting performance, and its optimum NS RA content is about 8%. The dynamic stability values of NS RA-modified asphalt mixtures are at least 3-fold higher than those of the base asphalt mixtures, and they are all far greater than the summer hot area requirement (no less than 2800 times/mm). NS RA-modified asphalt mixtures used in the middle course of asphalt pavement can obviously improve the anti-rutting performance of the pavement, and to enhance the anti-rutting ability of pavements, it should be used in the middle course of the pavement. The fatigue life values of NS RA-modified asphalt mixtures are at least 14.5-fold higher than those of the base asphalt mixtures. The freeze–thaw splitting strength ratio values of NS RA-modified asphalt mixtures are improved by at least 9.5% over the base asphalt mixtures, and their freeze–thaw splitting strength ratio values are all greater than the requirement (no less than 75%). In comparison with the base asphalt, the low temperature performances of NS RA-modified asphalt and its mixtures slightly decline, but they can meet the requirements for the zones with a minimum temperature of no less than –21.5 °C too. Therefore, except for the extremely low temperature area, it is an effective method for solving the rutting problem of pavement for using NS RA-modified asphalt.
Limin Li; Zhaoyi He; Weidong Liu; Cheng Hu. A Study on the Application of Rock Asphalt from Sichuan China Based on Anti-Rutting Performance. Applied Sciences 2019, 9, 870 .
AMA StyleLimin Li, Zhaoyi He, Weidong Liu, Cheng Hu. A Study on the Application of Rock Asphalt from Sichuan China Based on Anti-Rutting Performance. Applied Sciences. 2019; 9 (5):870.
Chicago/Turabian StyleLimin Li; Zhaoyi He; Weidong Liu; Cheng Hu. 2019. "A Study on the Application of Rock Asphalt from Sichuan China Based on Anti-Rutting Performance." Applied Sciences 9, no. 5: 870.