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学者姓名：范立峰
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Abstract ：
Lightweight geopolymer can combine good physical and mechanical properties, good thermal and chemical stability, low CO2 emission and low energy. The development of high strength lightweight geopolymer concrete for load-bearing structures is important to expand the application range of geopolymer. This paper presents an improvement study on the mechanical properties and pore structure of lightweight geopolymer concrete (LGC) by adding ground granulated blast-furnace slag (GGBFS). The effect of GGBFS content on the mechanical properties of LGC was analyzed, including ultimate compressive stress and elastic modulus. The variation in the microscopic pore structure of LGC with different GGBFS content was further analyzed by low-field nuclear magnetic resonance (LF-NMR) technology. The lightweight geopolymer concrete with different strength grades was proposed including LC20, LC30 and LC40. The results show that as the GGBFS content increases, the ultimate compressive stress and specific strength of LGC increase while the strain corresponding to peak stress decreases, which means that the mechanical properties and deformation resistance of LGC are improved. The CO2 emissions of LGC are lower than that of cement-based lightweight concrete, which shows good sustainability. The results also show that the addition of GGBFS can produce more gel and reduce the volume proportion of capillary pores and air pores, resulting in the densification of the LGC. The recommended GGBFS contents corresponding to the strength grades of LC20, LC30 and LC40 are 0 similar to 12.7 %, 12.7 % similar to 24.6 % and 24.6 % similar to 30%, respectively. The LGC has the characteristics of lightweight and high-strength, which has a potential application in civil engineering. Highlights Mechanical properties and pore structure of LGC were improved by adding GGBFS. The effect of GGBFS content on geopolymer concrete properties was discussed. Effect of slag content on pore structure of geopolymer concrete were studied. GGBGS content of geopolymer concrete with different strength grades was proposed.
Keyword ：
Porosity Porosity LF-NMR LF-NMR GGBFS content GGBFS content Lightweight geopolymer concrete Lightweight geopolymer concrete Microscopic pore structure Microscopic pore structure
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| GB/T 7714 | Zhong, W. L. , Wang, H. , Zhao, X. et al. Optimization of mechanical properties and pore structure of lightweight geopolymer concrete using GGBFS based on LF-NMR technology [J]. | MAGAZINE OF CONCRETE RESEARCH , 2024 , 76 (21) : 1229-1240 . |
| MLA | Zhong, W. L. et al. "Optimization of mechanical properties and pore structure of lightweight geopolymer concrete using GGBFS based on LF-NMR technology" . | MAGAZINE OF CONCRETE RESEARCH 76 . 21 (2024) : 1229-1240 . |
| APA | Zhong, W. L. , Wang, H. , Zhao, X. , Li, J. X. , Fan, L. F. . Optimization of mechanical properties and pore structure of lightweight geopolymer concrete using GGBFS based on LF-NMR technology . | MAGAZINE OF CONCRETE RESEARCH , 2024 , 76 (21) , 1229-1240 . |
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Abstract ：
The cracking of geopolymer caused by its brittleness characteristics could reduce the stability and durability of the building structure. Studying the cracking behavior of fiber-reinforced geopolymer composites (FRGCs) is important to evaluate the toughness strengthening of geopolymer. This paper presents a real-time study on the cracking characteristics of FRGCs under splitting tensile load based on high-speed digital image correlation (HDIC) technology. The splitting tensile test was conducted on the FRGC with different fiber content. The real-time variation of strain and displacement field during the splitting process was analyzed. The influence of fiber content on the mechanical properties and crack behavior of FRGCs was discussed. Considering the splitting strength and crack width, the optimal fiber content for FRGCs that satisfied the crack resistance requirement was proposed. The results show that the incorporation of fiber can delay the cracking time and reduce strain change during the splitting process. The splitting tensile strength and the deformation increase as fiber content increases, while the crack width decreases as fiber content increases. The FRGC with 2.0% fiber content can maintain a crack width smaller than 0.1 mm, which satisfies the crack resistance requirements of practical engineering for economic consideration.
Keyword ：
cracking characteristics cracking characteristics high-speed digital image correlation high-speed digital image correlation fiber-reinforced geopolymer composites fiber-reinforced geopolymer composites splitting tensile test splitting tensile test fiber content fiber content
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| GB/T 7714 | Zhang, Yunhan , Sun, Yuhang , Zhong, Weiliang et al. A Real-Time Study on the Cracking Characteristics of Polyvinyl Alcohol Fiber-Reinforced Geopolymer Composites under Splitting Tensile Load Based on High-Speed Digital Image Correlations [J]. | BUILDINGS , 2024 , 14 (7) . |
| MLA | Zhang, Yunhan et al. "A Real-Time Study on the Cracking Characteristics of Polyvinyl Alcohol Fiber-Reinforced Geopolymer Composites under Splitting Tensile Load Based on High-Speed Digital Image Correlations" . | BUILDINGS 14 . 7 (2024) . |
| APA | Zhang, Yunhan , Sun, Yuhang , Zhong, Weiliang , Fan, Lifeng . A Real-Time Study on the Cracking Characteristics of Polyvinyl Alcohol Fiber-Reinforced Geopolymer Composites under Splitting Tensile Load Based on High-Speed Digital Image Correlations . | BUILDINGS , 2024 , 14 (7) . |
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Abstract ：
The stability of rock blocks near the underground opening may be influenced by the impact loadings caused by either natural hazards or man-made disasters. This paper addressed the dynamic response of the rock blocks under impact loadings. The experimental tests were carried out to record the movement as a function of vibrations using the impact-induced rock burst system. Granite blocks were placed in the steel frame and loaded to the designed quasi-static condition at first. Permanent jumps of displacements toward the opening were observed after the pulse loading was applied. Analytical investigations were carried out to understand the macroscopic friction during the vibration progress. The results showed that the friction force was reduced by 4% due to the pulse loading in the orthogonal direction. The friction angle at the block boundary was also determined and further adopted in the DDA models which were built to understand the micro-friction. Three zones were determined in the model based on the uneven distributions of stresses in the potential sliding block: the concentration zone, the transition zone and the active zone, from the opening to the inner place. Consequently, the variations of stress and displacement as the function of the vibrations in the three distinguished zones were presented to show the dynamic response of the stressed rock block. The results showed that the direction of the major principal stress was turning to be vertical in the concentration zone which was favorable for self-stabilization during the impact loading. Dynamic responses of stressed rock blocks were tested.Analytical investigations were carried out to understand the macroscopic friction.DDA models were built to examine the microscopic friction.
Keyword ：
Macroscopic friction Macroscopic friction Microscopic friction Microscopic friction Dynamic response Dynamic response DDA DDA
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| GB/T 7714 | Nie, Wen , Yong, Zhaorui , Ma, Guowei et al. Dynamic Responses of an Underground Opening Subject to Impact Loadings in Blocky Rock [J]. | ROCK MECHANICS AND ROCK ENGINEERING , 2024 , 57 (8) : 5595-5608 . |
| MLA | Nie, Wen et al. "Dynamic Responses of an Underground Opening Subject to Impact Loadings in Blocky Rock" . | ROCK MECHANICS AND ROCK ENGINEERING 57 . 8 (2024) : 5595-5608 . |
| APA | Nie, Wen , Yong, Zhaorui , Ma, Guowei , Liu, Dongqiao , Fan, Lifeng , Sun, Jie . Dynamic Responses of an Underground Opening Subject to Impact Loadings in Blocky Rock . | ROCK MECHANICS AND ROCK ENGINEERING , 2024 , 57 (8) , 5595-5608 . |
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Abstract ：
This study experimentally investigated the wave attenuation coefficient and wave number of the heated granite after water cooling (W-C) and air cooling (A-C) treatments. The granite specimens heated to five temperatures (25 degrees C, 100 degrees C, 200 degrees C, 300 degrees C and 400 degrees C) were subjected to the W-C and A-C treatments, respectively. The pendulum impact test was performed on the cooled granite at room temperature to obtain the separated stress pulse. The wave attenuation ratio in the cooled granite was investigated. Propagation coefficients (attenuation coefficient and wave number) were introduced to describe the harmonic wave attenuation in the cooled granite. The effects of W-C and A-C treatments on the attenuation coefficient and wave number were discussed. The results show that the P-wave velocity decreases as temperature increases, while the wave attenuation ratio increases as temperature increases. The P-wave velocity of the granite after the W-C treatment is smaller than that of the granite after the A-C treatment. The wave attenuation ratio, attenuation coefficient and wave number of the stress pulse in the granite after the W-C treatment are larger than those of the stress pulse in the granite after the A-C treatment. The differences of P-wave velocity, wave attenuation ratio, attenuation coefficient and wave number after two cooling treatments increase as temperature increases.
Keyword ：
Granite Granite High temperature High temperature Wave attenuation Wave attenuation Wave velocity Wave velocity Cooling method Cooling method
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| GB/T 7714 | Yang, Q. H. , Yang, K. C. , Li, G. Y. et al. Wave attenuation coefficient and wave number of high-temperature granite after water cooling and air cooling [J]. | BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT , 2024 , 83 (10) . |
| MLA | Yang, Q. H. et al. "Wave attenuation coefficient and wave number of high-temperature granite after water cooling and air cooling" . | BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT 83 . 10 (2024) . |
| APA | Yang, Q. H. , Yang, K. C. , Li, G. Y. , Fan, L. F. , Du, X. L. . Wave attenuation coefficient and wave number of high-temperature granite after water cooling and air cooling . | BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT , 2024 , 83 (10) . |
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Abstract ：
The seismic wave propagation properties of granite after thermal cycles were experimentally investigated. The granite specimens were subjected to a series of thermal cycles with different thermal cycling temperatures and numbers. Ultra-sonic and pendulum impact tests were performed on the gran-ite after thermal cycles. Subsequently, a theoretical study was introduced to explore the wave propagation coefficients of granite after thermal cycles. The effects of the thermal cycling number on the wave attenuation rate, wave velocity, attenu-ation coefficient, and wavenumber were discussed. The results indicate that the wave velocity and dynamic elastic modulus decrease as the number of thermal cycles increases and that the damage factor increases as the number of thermal cycles increases. However, the variations in wave velocity, dynamic elastic modulus, and damage factor are concentrated mainly in the first thermal cycle. The results further indicate that the wave propagation coefficients, attenuation coefficient, and wavenumber increase as the number of thermal cycles increases. However, they are not significantly influenced by the amplitude and wavelength of impact loading.
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| GB/T 7714 | Fan, Lifeng , Yang, Kaichao , Wang, Meng et al. Original Article Evaluation of postoperative bleeding control employing Surgicel: a clinical trial [J]. | GEOPHYSICS , 2023 , 88 (2) : G19-G27 . |
| MLA | Fan, Lifeng et al. "Original Article Evaluation of postoperative bleeding control employing Surgicel: a clinical trial" . | GEOPHYSICS 88 . 2 (2023) : G19-G27 . |
| APA | Fan, Lifeng , Yang, Kaichao , Wang, Meng , Chen, Su . Original Article Evaluation of postoperative bleeding control employing Surgicel: a clinical trial . | GEOPHYSICS , 2023 , 88 (2) , G19-G27 . |
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Abstract ：
This study aims to prepare cement mortar with different proportions of artificial geopolymer sand (AGS) and investigate its dynamic mechanical properties. Firstly, AGS was used to replace natural sand (NS) to obtain cement mortar with different proportions of AGS (0.0%, 20.0%, 40.0%, 60.0%, 80.0% and 100.0%). Secondly, the dynamic impact test was conducted on cement mortar. The dynamic stress-strain relationship was obtained. Finally, the effects of AGS replacement rate and strain rate on dynamic mechanical properties (dynamic strength, elastic modulus, energy absorption and dynamic increase factor DIF) of cement mortar were discussed. The results show that the dynamic strength, elastic modulus and energy absorption of cement mortar increase firstly and then decrease as replacement rate increases at a fixed impact pressure, while DIF decreases firstly and then increases with replacement rate increasing. The dynamic strength, elastic modulus and energy absorption reach the maximum, the DIF reaches the minimum at the replacement rate of 20.0%. In addition, the dynamic strength, DIF and energy absorption of cement mortar significantly increase as strain rate increases, showing an obvious rate dependence.
Keyword ：
Cement mortar Cement mortar Dynamic mechanical properties Dynamic mechanical properties Replacement rate Replacement rate Artificial geopolymer sand Artificial geopolymer sand
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| GB/T 7714 | Gao, J. W. , Li, H. , Zhong, W. L. et al. Effects of artificial geopolymer sand as an alternative to natural sand on dynamic mechanical properties of cement mortar [J]. | CONSTRUCTION AND BUILDING MATERIALS , 2023 , 394 . |
| MLA | Gao, J. W. et al. "Effects of artificial geopolymer sand as an alternative to natural sand on dynamic mechanical properties of cement mortar" . | CONSTRUCTION AND BUILDING MATERIALS 394 (2023) . |
| APA | Gao, J. W. , Li, H. , Zhong, W. L. , Fan, L. F. , Jiang, D. . Effects of artificial geopolymer sand as an alternative to natural sand on dynamic mechanical properties of cement mortar . | CONSTRUCTION AND BUILDING MATERIALS , 2023 , 394 . |
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Abstract ：
This paper investigated the microstructure deterioration of sandstones under three commonly used freezing-thawing (F-T) cycle treatments and compared the thermal-induced damage caused by these F-T treatments. Firstly, a series of F-T cycle treatments were carried out on the sandstones by the three F-T methods namely freezing in water and thawing in water (W-W), freezing in air and thawing in water (A-W), and freezing in air and thawing in air (A-A), respectively. Then, computed tomography (CT) tests were performed to observe the variations in microdefects of sandstones from planar and spatial levels, which were quantitatively described by areal porosity and volumetric porosity. Moreover, the damage factor was introduced to describe the damage evolutions of sandstones under F-T cycles and compare the differences in microstructure deterioration induced by the three F-T treatments. Finally, a damage estimation model based on the simplest F-T treatment method (A-A) was established to estimate the damage degree of sandstones under the W-W and A-W treatments. The results showed that under the three F-T treatments, the microdefects of sandstones developed, the areal porosities, volumetric porosities, damage factors, and damage difference coefficients increased as the number of F-T cycles increased. However, the different F-T treatments had different effects on the microstructure deterioration of sandstones. As the number of cycles increased to 50, the W-W treatment caused the most serious damage to sandstone, followed by A-W and A-A treatments. In addition, the damage estimation model based on the A-A treatment can effectively estimate the damage degree of sandstones under W-W and A-W treatments.
Keyword ：
Damage and deterioration Damage and deterioration Estimation model Estimation model CT scanning CT scanning Microstructure Microstructure Three freezing-thawing treatments Three freezing-thawing treatments
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| GB/T 7714 | Fan, Lifeng , Qiu, Bei , Gao, Jingwei . Evaluation of microstructure deterioration inside sandstone under three different freezing-thawing cycle treatments [J]. | BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT , 2023 , 82 (5) . |
| MLA | Fan, Lifeng et al. "Evaluation of microstructure deterioration inside sandstone under three different freezing-thawing cycle treatments" . | BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT 82 . 5 (2023) . |
| APA | Fan, Lifeng , Qiu, Bei , Gao, Jingwei . Evaluation of microstructure deterioration inside sandstone under three different freezing-thawing cycle treatments . | BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT , 2023 , 82 (5) . |
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Abstract ：
An economical and widely available raw material is essential for the application and populari-zation of geopolymer. Due to the vast reserves of natural clay, calcined natural clay is considered a cost-effective geopolymer raw material. The present study aims at developing a high-ductile engineered geopolymer composites (EGC) using calcined natural clay. Firstly, natural clay as a construction waste was ground and calcined, and the calcined natural clay was mixed with ground granulated blast furnaces slag (GGBFS) and polyvinyl alcohol (PVA) fiber to prepare geopolymer composite samples. Then, the mini slump and uniaxial tensile test were conducted on the geopolymer composite samples, and the digital image correlation technology (DIC) was used to further analyze the effect of the slag and fiber contents on the tensile behavior of EGC. Finally, the optimal slag and fiber contents for EGC with highest ductility were proposed. The results showed that the natural clay exhibited a certain reactivity after a thermal activation process due to the presence of a small amount of kaolinite. The tensile properties of geopolymer composites prepared by calcined natural clay were significantly enhanced with increasing fiber content. Meanwhile, the incorporation of slag could enhance the tensile properties, while excessive slag content decreased the tensile properties. The EGC with 10.0% slag content and 2.5% fiber content exhibited the highest ductility, with an ultimate tensile strength of 3.61 MPa and a tensile strain capacity of 6.59%.
Keyword ：
Digital image correlation Digital image correlation Tensile properties Tensile properties Polyvinyl alcohol fiber Polyvinyl alcohol fiber Calcined natural clay Calcined natural clay Engineered geopolymer composites Engineered geopolymer composites
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| GB/T 7714 | Zhong, W. L. , Zhang, Y. H. , Fan, L. F. . High-ductile engineered geopolymer composites (EGC) prepared by calcined natural clay [J]. | JOURNAL OF BUILDING ENGINEERING , 2023 , 63 . |
| MLA | Zhong, W. L. et al. "High-ductile engineered geopolymer composites (EGC) prepared by calcined natural clay" . | JOURNAL OF BUILDING ENGINEERING 63 (2023) . |
| APA | Zhong, W. L. , Zhang, Y. H. , Fan, L. F. . High-ductile engineered geopolymer composites (EGC) prepared by calcined natural clay . | JOURNAL OF BUILDING ENGINEERING , 2023 , 63 . |
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Abstract ：
The propagation properties of stress waves in rock masses are significantly affected by high temperature. This paper presents an experimental investigation on the frequency-spectrum characteristics of stress waves in hightemperature granites. The pendulum impact test was performed on high-temperature granite bars to generate stress waves. The frequency-spectrum variation of stress waves in high-temperature granites was investigated by adopting the discrete Fourier transform. The effects of temperature on both the spectral attenuation ratio and the average energy dissipation rate of the harmonic wave were discussed. The results show that frequency spectra of stress waves occur attenuation when stress waves propagate in high-temperature granites. The frequencyspectrum attenuation is more obvious in the granite with higher temperature. Moreover, the spectral attenuation ratio and the average energy dissipation rate of the harmonic wave are significantly affected by the high temperature. The spectral attenuation ratio and the average energy dissipation rate of the harmonic wave increase as temperature increases.
Keyword ：
Energy dissipation Energy dissipation Frequency spectrum Frequency spectrum Wave propagation Wave propagation Wave attenuation Wave attenuation High temperature High temperature
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| GB/T 7714 | Yang, Qihao , Fan, Lifeng , Du, Xiuli . Experimental investigation on the frequency-spectrum characteristic of stress wave propagation through thermally treated granite [J]. | INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES , 2023 , 170 . |
| MLA | Yang, Qihao et al. "Experimental investigation on the frequency-spectrum characteristic of stress wave propagation through thermally treated granite" . | INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES 170 (2023) . |
| APA | Yang, Qihao , Fan, Lifeng , Du, Xiuli . Experimental investigation on the frequency-spectrum characteristic of stress wave propagation through thermally treated granite . | INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES , 2023 , 170 . |
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Abstract ：
In rock engineering, the weakening effects of water on the stressed rock are nonnegligible. This paper studied the microstructure deterioration processes of sandstones under stress and stress-water coupling by real-time computed tomography (CT) technology and compared the difference in these two processes. Firstly, the real-time CT tests were performed on the dry and saturated sandstones during the uniaxial compression to study the progressive deterioration of sandstones caused by stress and stress-water coupling, which were further quantitatively described by porosity. Then, the equivalent radius was introduced to analyze the real-time pore structure characteristics of sandstones under stress and stress-water coupling. Finally, the difference in failure patterns of sandstones under stress and stress-water coupling was compared. The results show that the real-time CT images intuitively present the continuous changes of spatial morphology of defects in sandstones under stress and stress-water coupling. During the uniaxial compression, the porosities of dry and saturated sandstones decrease at first, then increase slowly and finally increase rapidly. However, as the increase of stress, the variation in porosity, shifting of pore size distribution curve and change of maximum equivalent radius interval of saturated sandstone are more significant, indicating that even under the same stress state, the water aggravates the microstructure deterioration of sandstone, thus leading to the reduction of bearing capacity of sandstone. In addition, the failed region of saturated sandstone is mainly composed of multiple shear and tensile cracks, which presents the typical tensile-shear composite failure.
Keyword ：
Pore structure characteristic Pore structure characteristic Failure characteristic Failure characteristic Damage-failure process Damage-failure process Microscopic observation Microscopic observation Real-time CT scanning Real-time CT scanning
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| GB/T 7714 | Fan, L. F. , Qiu, B. , Fan, Y. D. et al. Stress-Water Coupling Effects on Failure of Sandstone Based on Real-Time CT Technology [J]. | ROCK MECHANICS AND ROCK ENGINEERING , 2023 , 56 (6) : 4329-4341 . |
| MLA | Fan, L. F. et al. "Stress-Water Coupling Effects on Failure of Sandstone Based on Real-Time CT Technology" . | ROCK MECHANICS AND ROCK ENGINEERING 56 . 6 (2023) : 4329-4341 . |
| APA | Fan, L. F. , Qiu, B. , Fan, Y. D. , Gao, J. W. . Stress-Water Coupling Effects on Failure of Sandstone Based on Real-Time CT Technology . | ROCK MECHANICS AND ROCK ENGINEERING , 2023 , 56 (6) , 4329-4341 . |
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