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Experimental study on SHPB cyclic impact of rubber-cement composite with different confine modes

Yang Rongzhou, Xu Ying, Chen Peiyuan, Cheng Lin, Ding Jinfu, Fu Hongxin

Archives of Civil Engineering

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2023

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Vol. 69, nr 2

517--534

EN

To promote the application of rubber-cement composites as the main bearing structure and key components in practical engineering under frequent dynamic disturbances, in this work, the split Hopkinson pressure bar (SHPB) cyclic impact tests of rubber-cement composite specimens with four different confine modes were carried out in which the impact load increased sequentially. The relationship between average strain rate, ultimate strain and impact times and the relationship between peak stress, damage energy, ultimate strain and incident energy were analyzed. The results showed that the appropriate confine reinforcement treatment can make rubber-cement composite give full play to its deformation ability when it was completely damaged. Carbon fiber-reinforced polymer (CFRP) sheet and steel cylinder can work together with the rubber-cement composite matrix to resist impact load, which effectively improves the structural strength, damage fracture energy, and cyclic impact resistance of the rubber-cement composite. Finally, based on the effect difference of confine modes, the simplified plane force models of rubber-cement composite specimens with four different confine modes were established, which clearly revealed the completely different impact resistance mechanism of the rubber-cement composites with different constraints under cyclic impact loading.

2

Dynamic tensile behaviour under impact loading for rocks damaged by static precompression

Zheng Qiangqiang, Xu Ying, Yin Zhiqiang, Wang Feng, Zhang Haijiang

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e199, 2023

EN

In geotechnical engineering projects, rock masses are subjected to various degrees of disturbance from geotectonic movements, rock drilling and mining before they are subjected to dynamic loads such as rock bursts, earthquakes, and blasting. We aim to investigate the dynamic mechanical properties, strain field, energy evolution, and progressive cracking of damaged sandstone under impact loading. In this study, sandstone specimens undergo various damage degrees caused by precompression and are characterized by computed tomography (CT) imaging. Then, the damaged specimens are subjected to impact tensile loads by employing a split Hopkinson pressure bar (SHPB) coupled with a high-speed camera and digital image correlation (DIC). The experimental results show that the energy dissipation density ratio, scale of the initial central crack, strain, and level of rock fragmentation in the vicinity of the bar-sample interfaces all increase with increasing driving pressure or sandstone damage degree. In contrast, the regular pattern of dynamic tensile strength is the opposite. We also find that the total strength rises before the prestress ratio of 0.2 and subsequently decreases as the sandstone’s damage degree increases. The rock’s dynamic tensile strength reduction ratio grows with the Weibull distribution as the damage degree expands. In addition, the function of the growth rate of the dissipated energy density ratio concerning the sandstone’s damage factor follows the Weibull distribution. These findings are of great significance to studying the mechanical responses of damaged rock and risk mitigation under dynamic catastrophes such as rock bursts, earthquakes, and blasting in rock engineering projects.

3

Dispersion of sodium phytate on muscovite and the implications for arsenopyrite flotation

Zou Dan, Wang Zhen, Zhao Kaile, Xu Ying

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 6

art. no. 154951

EN

The effective flotation separation of sulfides and sliming silicate minerals is always a difficult problem. In this paper, the selective flotation of arsenopyrite from muscovite was studied by using sodium phytate (SP) as dispersant, and the mechanism was investigated through SEM/EDS, zeta potential, FTIR and XPS measurements. Single mineral flotation results showed that with the increasing isoamyl xanthate (IAX) dosage the recovery of arsenopyrite increased, until 8×10−5 mol/L IAX (79.40% recovery, pH=7), after that it decreased slightly. While muscovite floated poorly at any IAX concentration. For the mixed minerals, arsenopyrite recovery was only 54.63% while that of muscovite was 42.70%, which was attributed to the coverage of muscovite on arsenopyrite surface. When 6×10−5 mol/L SP was added into the mixed minerals system, the recovery of arsenopyrite recovered to 68.26% while that of muscovite was 8.48% (approximate the value of the single mineral). SEM/EDS results showed that SP could disperse muscovite and prevented its coverage on arsenopyrite surface. Zeta potential results showed that the electrokinetic potential of muscovite and arsenopyrite decrease from -26.60mV to -39.01 mV and from -26.90 mV to -27.84 mV at pH=7, respectively. It was obvious that the negatively charged phytate ions selectively adsorbed on the surface of muscovite. FTIR and XPS resulted co-proved the chemisorption of SP with active sites on muscovite while arsenopyrite spectrum did not change significantly, which was consistent with flotation and zeta potential results. The selective adsorption of SP on muscovite compared to arsenopyrite was responsible for the effective separation of them.

4

Adsorption of yeast dextran on clinochlore surface and the implications for pyrite/clinochlore separation

Wang Zhen, Zou Dan, Zhao Kaile, Safarov Sayfidin, Xu Ying

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 4

art. no. 151635

EN

Silicate minerals with a certain degree of flotability are often easy to mix into sulfide ore concentrate in mineral processing industry. In this paper, the adsorption of yeast dextran on clinochlore and its application in pyrite/clinochlore separation were investigated. The adsorbed amount and micro polarity measurement results displayed that the yeast dextran molecules selectively adsorbed onto clinochlore surface compared with pyrite. The adsorbed yeast dextran resulted in the increase in the surface polarity of clinochlore surface, and inhibited the further adsorption of xanthate, thus keep it hydrophilic and depressed. Quantum chemical computation results indicated that yeast dextran was mainly adsorbed on mineral surface by the chelation with the surface metal active sites, and the chelating strength of yeast dextran with three ions was in the sequence of Fe3+ > Mg2+ > Fe2+. While Mg2+, Fe2+ and Fe3+ are the main metal ions on the surface of clinochlore, and Fe2+ is the unique metal ions on pyrite surface. This is the reason of the selectivity of the yeast dextran depressant for pyrite/clinochlore flotation system. The flotation results demonstrated that yeast dextran was qualified to selectively depress clinochlore in pyrite flotation.

5

Experimental study on dynamic stability of rubber-cement composites by SHPB and high-speed slicing

Yang Rongzhou, Xu Ying, Chen Pei Yuan

Archives of Civil Engineering

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2022

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Vol. 68, nr 1

319--334

EN

Improper disposal of waste tires will not only bring environmental impact and safety risks but also cause a serious waste of resources. In the field of civil engineering materials, waste tire particles are used as a substitute for non-renewable aggregates to produce flexible rubber-cement composites (RCC). To explore the high-speed slicing stability of RCC, this test took normal cement mortar (NCM) and rubber cement mortar (RCM) as research objects. The SHPB tests with the same impact energy level and the high-speed slicing tests with a slice thickness range of about 1.4 mm ~ 4.4 mm were carried out. The results showed that NCM and RCM showed different stability differences in the process of high-speed slicing. In the case of ensuring the integrity of the slice, the minimum thickness of the slice can be better decreased with the increase of the rubber content. Finally, from the perspectives of split Hopkinson pressure bar (SHPB) test results and mesoscopic structure states, the essential reason for ensuring the stability of high-speed slicing lied in the improvement of rubber particles (dominant role) and pores on material deformation and flexible energy dissipation.