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RISS 인기검색어
- 검색키워드
- 저자 : Hu Shaowei (검색결과 4 건)
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Effects of subsequent curing on chloride resistance and microstructure of steam-cured mortar
Hu, Yuquan,Hu, Shaowei,Yang, Bokai,Wang, Siyao Techno-Press 2020 Advances in concrete construction Vol.9 No.5
The influence of subsequent curing on the performance of fly ash contained mortar under steam curing was studied. Mortar samples incorporated with different content (0%, 20%, 50% and 70%) of Class F fly ash under five typical subsequent curing conditions, including standard curing (ZS), water curing(ZW) under 25℃, oven-dry curing (ZD) under 60℃, frozen curing (ZF) under -10℃, and nature curing (ZN) exposed to outdoor environment were implemented. The unsteady chloride diffusion coefficient was measured by rapid chloride migration test (RCM) to analyze the influence of subsequent curing condition on the resistance to chloride penetration of fly ash contained mortar under steam curing. The compressive strength was measured to analyze the mechanical properties. Furthermore, the open porosity, mercury intrusion porosimetry (MIP), x-ray diffraction (XRD) and thermogravimetric analysis (TGA) were examined to investigate the pore characteristics and phase composition of mortar. The results indicate that the resistance to chloride ingress and compressive strength of steam-cured mortar decline with the increase of fly ash incorporated, regardless of the subsequent curing condition. Compared to ZS, ZD and ZF lead to poor resistance to chloride penetration, while ZW and ZN show better performance. Interestingly, under different fly ash contents, the declining order of compressive strength remains ZS>ZW>ZN>ZD>ZF. When the fly ash content is blow 50%, the open porosity grows with increase of fly ash, regardless of the curing conditions are diverse. However, if the replacement amount of fly ash exceeds a certain high proportion (70%), the value of open porosity tends to decrease. Moreover, the main phase composition of the mortar hydration products is similar under different curing conditions, but the declining order of the C-S-H gels and ettringite content is ZS>ZD>ZF. The addition of fly ash could increase the amount of harmless pores at early age.
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Study on fracture characteristics of reinforced concrete wedge splitting tests
Hu Shaowei,XU Aiqing,HU Xin,YIN Yangyang 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.18 No.3
To study the influence on fracture properties of reinforced concrete wedge splitting test specimens by the addition of reinforcement, and the restriction of steel bars on crack propagation, 7 groups reinforced concrete specimens of different reinforcement position and 1 group plain concrete specimens with the same size factors were designed and constructed for the tests. Based on the double-K fracture criterion and tests, fracture toughness calculation model which was suitable for reinforced concrete wedge splitting tensile specimens has been obtained. The results show that: the value of initial craking load Pini and unstable fracture load Pun decreases gradually with the distance of reinforcement away from specimens’s top. Compared with plain concrete specimens, addition of steel bar can reduce the value of initial fracture toughness KIini, but significantly increase the value of the critical effective crack length ac and unstable fracture toughness KIun. For tensional concrete member, the effect of anti-cracking by reinforcement was mainly acted after cracking, the best function of preventing fracture initiation was when the steel bar was placed in the middle of the crack, and when the reinforcement was across the crack and located away from crack tip, it plays the best role in inhibiting the extension of crack.
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Yang Wang,Shaowei Hu,Jun Lu,Yanmin Qiao 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.9
This study examined the experiment of the water fracture interactions in the concrete. In order to create water pressure in the crack, a sealing device consisting of a mechanical clamp device and a waterproof membrane was proposed. Firstly, eighteen three-point bending tests were carried out to verify the proposed sealing device under three different loading rates. Subsequently, twelve hydraulic tests were performed under different loading rates. The results showed that the sealing device had minimal influence on the fracture behavior of concrete. Besides, with the increase of internal water pressure, the carrying capacity, fracture parameters and crack opening rate of concrete beam were evidently decreased. Meanwhile, the decrease of the carrying capacity, fracture parameters, and crack opening rate induced by internal water pressure decreased with the increase of loading rate. In addition, a significant hydraulic fracturing behavior caused by water pressure was observed in the quasi-static state.
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Damage and fracture processes of concrete using acoustic emission parameters
Fan Xiangqian,Hu Shaowei,Lu Jun 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.18 No.2
In order to observe the internal damage of concrete in real time, we introduced acoustic emission nondestructive detecting technology into a series of fracture tests; the test results revealed the whole process that concrete undergoes when it sustains damage that leads to failure, according to the change rules of the acoustic emission parameters. The results showed that both the initiation and unstable loads can be accurately determined using the abrupt change of the acoustic emission rate curves and the turning point of the acoustic emission parameters’ accumulative curves. The whole process, from damage to failure, includes five phases, beginning with damage, such as cracking, a stable crack growth process, a critical unstable stage, and unstable propagation. The brittle fracture characteristics of concrete change when steel bars are joined, because the steel bars and the concrete structure bond, which causes an increase in the acoustic emission signals within the fracture process of the reinforced concrete. The unstable propagation stage is also extended. Our research results provide a valid methodology and technical explanations, which can help researchers to monitor the cracking process of concrete structures, in real time, during actual projects.
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