Crack damage evolution in concrete coarse aggregates under microwave-induced thermal stress

Yuan, Yuan; Shao, Zhushan; Qiao, Rujia; Guo, Xuan; Wang, Weitao

doi:10.1007/s43452-022-00419-3

Cited by 6 publications

(3 citation statements)

References 44 publications

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“…The thermal expansion and temperature gradient caused by this local high temperature are large enough to cause a serious rock fracture effect. Similarly, in the process of actual microwave irradiation on heterogeneous rocks, the temperature of microwave-sensitive minerals with high dielectric properties rises rapidly after microwave irradiation; the temperature gradient and thermal expansion between minerals are large, which will also lead to rock fracture [ 24 ]. The maximum temperature from 4 cm to 8 cm drops sharply from 606 °C to 234 °C, with a decrease of 372 °C.…”

Section: Resultsmentioning

confidence: 99%

Effect of Waveguide Aperture and Distance on Microwave Treatment Performance in Rock Excavation

Chen

Zhang

2023

Sensors

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Rock burst is a common hazard during tunnel excavation in high-stress and hard rock strata. Microwave-assisted breaking has a great potential application in hard rock tunnel excavation, reducing the possibility of rock burst, and how to reasonably make the application on the TBM cutterhead is one of the critical issues. The waveguide aperture and distance between the rock face and waveguide have serious effects on its performance. In this paper, based on the arrangement of the microwave waveguide of the TBM cutterhead and the actual excavation situation, considering the reflection of microwave energy by the metal cutterhead and the scattering state of electromagnetic waves at the rock surface irradiation, a 2D model of rock irradiated by microwaves is established. The effects of waveguide aperture and distance on microwave irradiation performance of rock are studied, considering three different waveguide types: convergent waveguide, rectangular waveguide, and horn waveguide. The results show that the maximum temperature is located on the rock irradiation surface, rather than inside the rock. The rock temperature decreases in a cosine pattern with irradiation distance, rather than in linearity, which is consistent with the characteristics of electromagnetic wave propagation. The interval of irradiation distance where the rock temperature local maximum value appears is 1/4 of the electromagnetic wavelength, corresponding to the crest and trough of the electromagnetic wave. The rock temperature at the wave trough distance is lower than that of the wave crest distance, but the high-temperature zone is wider. In the range of 50~200 mm waveguide apertures, the rock temperature and damage decrease with the increase in waveguide aperture when irradiated at the crest distance, while the valley distance is opposite. A convergent waveguide and short irradiation distance enhance the energy focusing performance, so the temperature rise characteristics and rock damage are more concentrated. A large-waveguide-aperture horn waveguide and long irradiation distance form a wide range of high-temperature zones and rock damages.

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Section: Resultsmentioning

confidence: 99%

Effect of Waveguide Aperture and Distance on Microwave Treatment Performance in Rock Excavation

Chen

Zhang

2023

Sensors

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“…The process of fracture toughness degradation of the granite is analyzed herein. Based on scanning electron microscopy observations, the average length of the initial microcracks in granite is l 0 = 13 µm [50]. The cracks are subjected to both normal stress and shear stress, and the maximum stress intensity factor of the cracks in Mode I takes precedence over that of Mode II to exceed the fracture toughness in most cases [37].…”

Section: Fracture Toughness and Degradation Mechanism Of Granitementioning

confidence: 99%

“…It was assumed that the stress at the initial crack surface was uniform because the crack was micro-sized compared with the mineral particles. The stress intensity factor K I (MPa•m 1/2 ) of pre-existing cracks in Mode I can be calculated the following way [50]:…”

Section: Fracture Toughness and Degradation Mechanism Of Granitementioning

confidence: 99%

Analysis of Microwave-Induced Damage in Granite Aggregates Influenced by Mineral Texture

Yuan,

Zhao

2024

Buildings

Self Cite

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The use of microwave energy to recycle high-quality coarse aggregates from waste concrete or assist hard rock breakage in underground building engineering is promising. Controlling or promoting the damage of coarse aggregates, i.e., hard rocks, under microwave irradiation is a crucial issue faced by these techniques. Understanding the damage mechanisms of hard rocks exposed to microwaves is thus urgent. Fracture toughness is a significant mechanical parameter of rocks that reflects their ability to resist crack propagation and damage evolution. In this study, the fracture toughness degradation of microwave-heated granite was investigated by combining experimental investigations and numerical simulations. A three-point-bending (TPB) experiment was conducted on granite specimens after microwave irradiation. A coupled electromagnetic–thermal–mechanical model considering the actual mineral texture of the granite specimen was established. The evolution of the temperature gradient and stress field near the initial notch tip were investigated. The results suggest that the microwave-induced maximum temperature gradient and stress in granite are at the plagioclase–quartz (Pl–Qtz) interfaces or inside the Pl near the boundary. The region of cracking initiation was defined as the damage zone, which could be obtained by comparing the microwave-induced thermal stress with the critical value. The fracture toughness degradation, which corresponds to the evolution of the damage zones, can be divided into two stages. A relatively rapid decrease in fracture toughness in the first stage is primarily caused by the spread of the scattered damage zones along the Pl–Qtz interfaces; subsequently, a gentler fracture toughness degradation results mainly from the extension of the previous damage zones.

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The current status and future of solid waste recycled building bricks

Cheng,

Shao,

Wang

et al. 2023

Environ Sci Pollut Res

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Crack damage evolution in concrete coarse aggregates under microwave-induced thermal stress

Cited by 6 publications

References 44 publications

Effect of Waveguide Aperture and Distance on Microwave Treatment Performance in Rock Excavation

Effect of Waveguide Aperture and Distance on Microwave Treatment Performance in Rock Excavation

Analysis of Microwave-Induced Damage in Granite Aggregates Influenced by Mineral Texture

The current status and future of solid waste recycled building bricks

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