Experimental Study on the Properties of Mixed-Fiber Concrete Shield Tunnel Segments Subjected to High Temperatures

Zhang, Yajun; Wang, Yao; Ren, Zhaoqing

doi:10.3390/fire6010017

Cited by 3 publications

(4 citation statements)

References 11 publications

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“…Based on the requirements set out in the literature [ 19 ], the reinforcement ratio used in this study was 0.41%. The strength grade of longitudinal reinforcement on the inner and outer curved surfaces and hoop reinforcement was HRB400, and the reinforcement rate and method of the segments after exposure to high temperature were the same as those of the segments at room temperature.…”

Section: Test Methodsmentioning

confidence: 99%

“…The length of the steel fiber was 35 mm and its diameter was 0.7 mm; the length of the polypropylene fiber was 12 mm and its diameter was 0.03 mm; and the melting point was about 170 °C. Based on the requirements set out in the literature [19], the reinforcement ratio used in this study was 0.41%. The strength grade of longitudinal reinforcement on the inner and outer curved surfaces and hoop reinforcement was HRB400, and the reinforcement rate and method of the segments after exposure to high temperature were the same as those of the segments at room temperature.…”

Section: Test Sample Introductionmentioning

confidence: 99%

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Test Research on Residual Mechanical Properties of Fiber-Reinforced Concrete Segments after High Temperature

Zong,

Wang,

Wang

et al. 2024

Materials

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In order to research the residual mechanical properties of concrete shield tunnel segments after exposure to high temperatures, two types of concrete segments were designed: a self-compacting concrete segment and a mixed fiber (steel fiber and polypropylene fiber) self-compacting concrete segment. The mechanical properties of seven blocks of concrete segments (five segments after high-temperature exposure and two segments at room temperature) were tested to analyze the influence of different loading sizes and fibers on the development of cracks after high temperature, failure mode, crack width, deformation, and so on in the concrete segments. The results showed that the damage model of the segment after exposure to high temperature and the segment at room temperature were crushed in the pressurized zone, but the high temperature had little effect on the concrete in the pressurized area. The size of the preload at high temperatures had little effect on the remaining load capacity, and the effect on the number of cracks was mainly concentrated on the internal arc surface of the segment. After high-temperature exposure, the number of cracks on the sides and inner arc surface of the segment increased, and the development of cracks was concentrated as several major cracks at high temperatures. When fibers were incorporated, the cracks in the segment became obvious, where the cracks at the loading point became denser and the interval distance became smaller.

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Section: Test Methodsmentioning

confidence: 99%

Section: Test Sample Introductionmentioning

confidence: 99%

Test Research on Residual Mechanical Properties of Fiber-Reinforced Concrete Segments after High Temperature

Zong,

Wang,

Wang

et al. 2024

Materials

Self Cite

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“…The new magnesia expansion agent was commissioned by a company in Shandong for processing and preparation and the water reducing agent is Rheoplus101(ST) polycarboxylate superplasticizer produced by a company. The polymer was MU-618 waterborne epoxy polymer produced by a chemical plant in Shanghai [16]. The curing agent (G) was a curing agent produced by a chemical plant in Changzhou, which is a colorless liquid with an active hydrogen equivalent of 24.3 and with 10~13 parts per 100 standard resins.…”

Section: Test Raw Materialsmentioning

confidence: 99%

Properties of High-Performance Materials for the Crack Repair of Segment Structures

Sun,

Zhong,

Gao

et al. 2023

Sustainability

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In order to improve the crack repair effect of high-performance segment structure crack repair materials, in this paper, we used the orthogonal test research method of four factors and three levels to analyze changes in the microstructure of crack repair materials under different material compatibility levels, followed by analysis through the performance testing of repair materials. The flow performance, setting time, compressive and flexural strength, and bonding and tensile strength were studied. The results show that (1) excessively thick epoxy polymer film affects the bond strength, an appropriate increase in the polymer–cement ratio can promote the hydration of cement, and an appropriate increase in gel material can enhance the repair function of repair material; (2) the setting time clearly increases with increases in the polymer–cement and water–cement ratios and the decrease range clearly increases with an increase in the water–cement ratio; (3) the adhesive flexural strength of epoxy polymer repair material increased the most in 28 days; and (4) the bonding tensile strength of the repair material increases first and then decreases with increases in epoxy polymer content. An appropriate increase in the polymer–cement ratio can promote cement hydration.

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“…Zheng [29] pointed out that when the addition of polypropylene fiber was 0.25% volume fraction, the impact strength of foamed concrete increased by 300% compared to a blank control group. To reduce the bursting and peeling of concrete shield tunnel segments under fire and to improve durability, Zhang et al [30][31][32][33][34][35] investigated the fire performance of concrete shield tunnel segments with polypropylene fibers and their mixtures. Krishna et al [36] observed that the hybrid mixture of polypropylene and micro-steel fibers exhibited good impact resistance at high temperatures.…”

Section: Introductionmentioning

confidence: 99%

Study on the Compressive Stress–Strain Curve and Performance of Low-Slump Polypropylene Fiber Concrete after High Temperature

Zheng

Zhang

2023

Applied Sciences

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This study aims to investigate the effect of high temperature on the mechanical properties of low-slump polypropylene fiber (PPF) concrete, and tests the tensile and compressive properties of 204 groups of low-slump PPF concrete with eight different dosages and four different lengths at normal temperature and after high temperature. The results of the compressive test showed that PPF can significantly improve the mechanical properties of concrete after high temperature when the fiber content is small, and the compressive strength of low collapse polypropylene fiber concrete after high temperature showed a tendency to rise and then fall at the same temperature with an increase of the fiber admixture. When the fiber content was 0.5 kg/m3, the compressive strengths of 3 mm, 9 mm, 15 mm and 19 mm reached their maxima, which were 9.65%, 11.33%, 7.90% and 2.87% higher than that of ordinary concrete, respectively. With an increase in fiber length, the effect of PPF on the compressive strength of concrete is not obvious. PPF at high admixture further increases the pore and air content in concrete, which decreases the compactness of the concrete, thus leading to a decrease in the compressive strength of the concrete. When the temperature was 800 °C and the fiber admixture was 5.0 kg/m3, the compressive strength of PPF concrete with different lengths reduced by 17.83%, 17.27%, 22.59% and 23.92%, respectively, compared to normal concrete. In addition, according to the results, the optimal combinations of strength at room temperature and after high temperature were 3 mm fiber length and 1.0 kg/m3 dosing and 9 mm fiber length and 0.5 kg/m3 dosing, respectively, which increased the compressive and tensile strengths by 17.15% and 25.72% at room temperature and by at least 6% and 20% after high temperature, compared to the concrete without fiber dosing. Moreover, the stress–strain constitutive equations of PPF concrete at normal temperature and after high temperature were established, which can be used for finite element simulation and related mechanical analysis of PPF after high temperature.

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Experimental Study on the Properties of Mixed-Fiber Concrete Shield Tunnel Segments Subjected to High Temperatures

Cited by 3 publications

References 11 publications

Test Research on Residual Mechanical Properties of Fiber-Reinforced Concrete Segments after High Temperature

Test Research on Residual Mechanical Properties of Fiber-Reinforced Concrete Segments after High Temperature

Properties of High-Performance Materials for the Crack Repair of Segment Structures

Study on the Compressive Stress–Strain Curve and Performance of Low-Slump Polypropylene Fiber Concrete after High Temperature

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