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1

Research on the linear viscoelastic rheological properties of rejuvenated asphalt mastic based on the discrete element method

Lin Mei, Lei Yu, Li Ping, Shuai Jun, Wang Zhaoli

Archives of Civil Engineering

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2023

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Vol. 69, nr 2

399--416

EN

The rheological property of asphalt is an important factor affecting the pavement performance of asphalt binder, and the fundamental reason for the change of asphalt rheological property is the strong evolution of asphalt material meso structure. However, the internal mechanism of rejuvenated asphalt mastic system is complex and its rules are difficult to grasp. Aiming to study the relationship between meso mechanical parameters and rheological parameters of rejuvenated asphalt mastic, the meso structure model of rejuvenated asphalt mastic was established and improved based on the discrete element method. Moreover, the meso parameters of the model were obtained by the objective function method, and then the influences of various factors were studied to construct the mathematical constitutive model of rheological parameter modulus and meso mechanical parameters. Combing with the reliability of the improved Burgers model was verified based on the rheological test results of rejuvenated asphalt mastic. In addition, the virtual test of dynamic shear rheological dynamic frequency scanning was carried out on the asphalt mastic sample by particle flow software. By adjusting the mesomechanical parameters, the simulation results (complex shear modulus and phase angle) were consistent with the test results. This study clarified the relationship between mesomechanics and macro performance, and this model could be used to obtain the complex shear modulus of rejuvenated asphalt mastic under different types, filler-asphalt ratio and external force environments by adjusting particle flow, wall boundary and other conditions, which can greatly save the workload for the later research and provide a theoretical basis for production experiments.

2

Synthesis and Curing of Allyl Urethane NIMMO-THF Copolyether with Three Functional Groups as a Potential Energetic Binder

Wang Xiaochuan, Li Ping, Lu Xianming, Mo Hongchang, Xu Minghui, Liu Ning, Shu Yuanjie

Central European Journal of Energetic Materials

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2020

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Vol. 17, no. 1

141--163

EN

A tri-functional NIMMO-THF copolyether (T-NT) was synthesized by polymerization of 3-nitratomethyl-3-methyloxetane (NIMMO) and tetrahydrofuran (THF) in the presence of trimethylolpropane and catalyzed by BF3·OEt2. The allyl urethane NIMMO-THF copolyether with three functional groups (AUT-NT) was synthesized from tri-functional NIMMO-THF copolyether and allyl isocyanate. The polymer was characterized by FT-IR, 1H NMR, and 13C NMR. Furthermore, an elastomer that was prepared from allyl urethane NIMMO-THF copolyether with three functional groups and trimethylisophthalodinitrile oxide (TINO) had satisfactory mechanical properties and good thermal stability. The elastomer is expected to be used in composite solid propellants and polymer-bonded explosives (PBX).

3

Badania wytrzymałości, struktury porów i przemian fazowych materiału podsadzkowego zawierającego odpady po przeróbce rud żelaza, poddanego działaniu wysokiej temperatury

Tang Jianhui, Li Ping, Chen Xudong, Bai Yin

Cement Wapno Beton

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2020

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R. 25, nr 2

78--94

PL

Wraz ze zwiększaniem głębokości wydobycia kopalin, temperatura, na którą narażona jest podsadzka stale wzrasta, a więc zwiększa się także ryzyko samozapłonu minerałów zawierających siarkę. Nagłe pożary narażają podsadzkę na działanie wysokich temperatur, co zagraża bezpieczeństwu jej konstrukcji. Z tego względu, aby w pełni określić zmiany właściwości podsadzki, wystawionej na działanie wysokich temperatur, zbadano wytrzymałość na ściskanie i wytrzymałość na rozciąganie przy rozłupywaniu podsadzek z dodatkiem spoiwa cementowego, po różnym czasie dojrzewania: 7 dni, 28 dni i 60 dni oraz przy trzech stosunkach spoiwo/odpad: 1:6, 1:8 i 1:10, po prażeniu próbek w piecu wysokotemperaturowym, w temperaturze: 100°C, 200°C, 400°C, 600°C i 800°C. Zbadano także zmiany fazowe i strukturę porów w podsadzce po prażeniu w tych temperaturach. Uzyskane wyniki wykazały, że wytrzymałość i struktura porów w podsadzce z dodatkiem odpadów po przeróbce rud żelaza w wysokiej temperaturze zależą od czasu dojrzewania. Wytrzymałość podsadzki dojrzewającej przez 7 dni początkowo rośnie, a następnie maleje ze wzrostem temperatury. Wytrzymałość na ściskanie i wytrzymałość na rozciąganie przy rozłupywaniu osiągają maksimum odpowiednio w 200°C i 100°C. Bez względu na czas dojrzewania podsadzki, materiał wyprażony w temperaturze przekraczającej 400°C nie ma praktycznie żadnej wytrzymałości na rozciąganie. Cechy te są ściśle powiązane z rozkładem produktów hydratacji spoiwa, przede wszystkim ettringitu i fazy C-S-H.

EN

With the deepening of mining depth, the geothermal temperature faced by the pit backfill is getting higher and higher, so the spontaneous combustion probability of sulfur-bearing minerals increases. In addition, sudden fires can expose the backfill to high temperatures, which will endanger the structural safety of the backfill. Therefore, in order to fully understand the mechanical response and pore structure evolution characteristics of backfills under high-temperature loading, the compressive strength and splitting tensile strength of backfills with different ages: 7 days, 28 days and 60 days and cement-tailings ratios: 1:6, 1:8 and 1:10 were tested using high-temperature furnace to simulate different temperature loads: 100, 200, 400, 600 and 800°C. The pore structure characteristics of the backfill after high temperature are analyzed by mercury intrusion porosimetry. To further understand the mechanism of backfill transformation at high temperature, the phase evolution characteristics of iron tailings and cementitious materials are analyzed by X-ray diffractometer and differential thermal/thermogravimetric analyzer. The results show that the strength and pore structure of iron tailings backfill at high temperature are related to the curing age. The strength and most probable pore size of backfill cured at 7 days increased first and then decreased with the increase of temperature. Among them, the compressive strength and splitting tensile strength reached their peak values at 200°C and 100°C, respectively. While after 28 days, the pore size increased with the increase of high temperature, and the strength of backfill decreased continuously with increasing temperature. No matter what age of backfill is, it almost loses its tensile strength after being subjected to a high temperature above 400°C. These characteristics are closely related to the expansion of mica in iron tailings and the dehydration and decomposition of cementing material hydration products, such as ettringite and C-S-H phase at high temperature.

4

Battery/super-capacitor HESS applied in DC microgrid

Zhang Zhen, Baoge Zhang Baoge, Wang Donghao, Li Ping, Rong Yao

Archives of Electrical Engineering

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2020

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Vol. 69, nr 2

379--388

EN

Energy storage technology (EST) is an effective way to improve the power quality of renewable energy generation (such as solar energy and wind energy), but a single energy storage system (ESS) is difficult to meet the demand for the safe operation of the grid. According to the structure and operation characteristics of the existing battery/super-capacitor hybrid energy storage system (HESS), a battery/super-capacitor HESS is proposed. The working principle and three working modes (the super-capacitor pre-charging cold standby mode, the boost mode and buck mode) of the HESS are analyzed in detail. The state equations of the boost mode and buck mode are derived. The state space average method is used to establish the small signal equivalent model under the buck/boost mode. Moreover, the charge and discharge control strategy of the HESS is obtained by combining the voltage closed-loop control. The simulation model is built in Matlab/Simulink to verify the effectiveness of the proposed HESS and its control strategy. The results show that the HESS and its control strategy can ensure the DC bus voltage has good stability and superior anti-interference, and it can simultaneously provide large current, increase the battery life, and improve the technical economy of energy storage.