The cemented-gangue-fly-ash backfill(CGFB)prepared from coal-based solid waste materials commonly exhibits high brittleness,leading to an increased susceptibility to cracking.Uniaxial compressive strength(UCS),acousti...The cemented-gangue-fly-ash backfill(CGFB)prepared from coal-based solid waste materials commonly exhibits high brittleness,leading to an increased susceptibility to cracking.Uniaxial compressive strength(UCS),acoustic emission(AE),and scanning electron microscopy tests were conducted on CGFB samples with recycled steel fiber(RSF)contents of 0,0.5%,1.0%and 1.5%to assess the mechanical properties and damage evolution law of the CGFB.The research findings indicate that:1)When RSF contents were 0.5%,1%,and 1.5%,respectively,compared to samples without RSF,the UCS decreased by 3.86%,6.76%,and 15.59%,while toughness increased by 69%,98%,and 123%;2)The addition of RSFs reduced the post-peak stress energy activity and increased the fluctuations in the b-value;3)As the RSF dosage increased from 0 to 1.5%,the per unit dissipated strain energy increased from 5.84 to 21.51,and the post-peak released energy increased from 15.07 to 33.76,indicating that the external energy required for the CGFB sample to fail increased;4)The hydration products,such as C-S-H gel,ettringite,and micro-particle materials,were embedded in the damaged areas of the RSFs,increasing the frictional force at the interface between the RSF and CGFB matrix.The shape variability of the RSFs caused interlocking between the RSFs and the matrix.Both mechanisms strengthened the bridging effect of the RSFs in the CGFB,thereby improving the damage resistance capability of CGFB.The excellent damage resistance occurred at an RSF content of 0.5%;thus,this content is recommended for engineering applications.展开更多
This research addresses the growing demand for high-performance protective materials against high-velocity projectile impacts.The performance of multi-layered steel fiber-reinforced mortar(SFRM)panels with varying thi...This research addresses the growing demand for high-performance protective materials against high-velocity projectile impacts.The performance of multi-layered steel fiber-reinforced mortar(SFRM)panels with varying thicknesses and air gaps,was experimentally investigated under single and repeated impacts of 7.62×51 mm bullets fired from a distance of 50 m.The impact events were recorded using a high-speed camera at 40000 fps.Panel performance was assessed in terms of failure modes,kinetic energy absorption,spalling diameter,and percentage of back-face damage area,and weight loss.Results showed that panel configuration significantly influenced performance.Panel P10,with 70 mm SFRM thickness and 20 mm air gaps,provided the highest resistance,dissipating 5223 J of kinetic energy and preventing back-face damage.In contrast,P7,which absorbed 4476 J,presented a back damage area percentage of 8.93%after three impacts.Weight loss analysis further confirmed durability improvements,with P10 showing only 1.53%cumulative loss compared to 3.26%in P7.The inclusion of wider air gaps enhanced energy dissipation and reduced damage.Comparison between single and repeated impacts demonstrated the sustained resistance of high-performance panels,with P10 maintaining minimal degradation across three consecutive impacts.These findings highlight the potential of multi-layer SFRM panels to enhance ballistic resistance,making them suitable for military,security,and civilian protective applications requiring long-term durability.展开更多
An experimental study on the compressive behavior of steel fiber reinforced concrete-filled steel tube columns is presented. Specimens were tested to investigate the effects of the concrete strength, the thickness of ...An experimental study on the compressive behavior of steel fiber reinforced concrete-filled steel tube columns is presented. Specimens were tested to investigate the effects of the concrete strength, the thickness of steel tube and the steel fiber volume fraction on the ultimate strength and the ductility. The experimental results indicate that the addition of steel fibers in concrete can significantly improve the ductility and the energy dissipation capacity of the concrete-filled steel tube columns and delay the local buckling of the steel tube, but has no obvious effect on the failure mode. It has also been found that the addition of steel fibers is a more effective method than using thicker steel tube in enhancing the ductility, and more advantageous in the case of higher strength concrete. An analytical model to estimate the load capacity is proposed for steel tube columns filled with both plain concrete and steel fiber reinforced concrete. The predicted results are in good agreement with the experimental ones obtained in this work and literatures.展开更多
The complete splitting process of steel fiber reinforced concrete （SFRC） at intermediate strain rate was studied by experiment. The basic information of a self-developed SFRC dynamic test system matching with lnstro...The complete splitting process of steel fiber reinforced concrete （SFRC） at intermediate strain rate was studied by experiment. The basic information of a self-developed SFRC dynamic test system matching with lnstron 1342 materials testing machine was given, and the experiment principle and the loading mode of cubic split specimen were introduced. During the experiment, 30 cubes of 150 mm×150 mm×150 mm and 36 cubes of 100 mm×100 mm×100 mm, designed and prepared according to C20 class SFRC with different volume fractions of steel fiber （0, 1%, 2%, 3%, 4%） were tested and analyzed. At the same time, the size effect of SFRC at intermediate strain rate was investigated. The experimental study indicates that SFRC size effect is not influenced by the loading speed or strain rate. When the steel fiber content increases from 0 to 4%, the splitting strength of SFRC increases from 100% to 261%, i.e. increasing by 161% compared with that of the common concrete. The loading rate increases from 1.33 kN/s to 80.00 kN/s, and the splitting tensile strength increases by 43.55%.展开更多
Isothermal sintering experiments were performed on the 316 L stainless steel fiber felts with fiber diameters of 8 μm and20 μm. Surface morphologies of the sintered specimens were investigated by using scanning elec...Isothermal sintering experiments were performed on the 316 L stainless steel fiber felts with fiber diameters of 8 μm and20 μm. Surface morphologies of the sintered specimens were investigated by using scanning electron microscopy(SEM) and optical microscopy. The results show that the amount of the sintering necks and the relative densities of the fiber felt increase with the increasing of both the sintering temperature and the sintering time. And the activation energies estimated present a decline at high relative densities for both 8 μm and 20 μm fiber felts. Moreover, the sintering densification of the fiber felts is dominated by volume diffusion mechanism at low temperature and relative densities. As more grain boundaries are formed at higher temperature and relative density, grain boundary diffusion will also contribute to the densification of the specimen.展开更多
The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interfa...The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interface. Fatigue properties of the composite beam under the action of negative moment were experimentally studied. Through inverted loading mode the load-beating state of a composite beam was simulated under the action of negative moment. With the ratios of constructional bars being 0, 0.082% and 0.164% respectively as parameters, the effects of constructional bars on the properties of composite beam, such as fatigue life, crack propagation, rigidity loss as well as damage behavior of bonding interface, were studied. The mechanism of the constructional bars on the fatigue properties of the composite beams and the restriction mechanism of crack widths and rigidity loss were analyzed. The test results show that the constructional bars can enhance the shear resistance of the bonding interface between composite layer and old concrete beam and restrict expanding of steel fiber reinforced self-stressing concrete, which are beneficial to synergistic action of composite layer and old concrete beam, to reducing the stress amplitude of bars and the crack width of composite layer, and to increasing the durability and fatigue life of the composite beam.展开更多
基金Projects(52274143,51874284)supported by the National Natural Science Foundation of China。
文摘The cemented-gangue-fly-ash backfill(CGFB)prepared from coal-based solid waste materials commonly exhibits high brittleness,leading to an increased susceptibility to cracking.Uniaxial compressive strength(UCS),acoustic emission(AE),and scanning electron microscopy tests were conducted on CGFB samples with recycled steel fiber(RSF)contents of 0,0.5%,1.0%and 1.5%to assess the mechanical properties and damage evolution law of the CGFB.The research findings indicate that:1)When RSF contents were 0.5%,1%,and 1.5%,respectively,compared to samples without RSF,the UCS decreased by 3.86%,6.76%,and 15.59%,while toughness increased by 69%,98%,and 123%;2)The addition of RSFs reduced the post-peak stress energy activity and increased the fluctuations in the b-value;3)As the RSF dosage increased from 0 to 1.5%,the per unit dissipated strain energy increased from 5.84 to 21.51,and the post-peak released energy increased from 15.07 to 33.76,indicating that the external energy required for the CGFB sample to fail increased;4)The hydration products,such as C-S-H gel,ettringite,and micro-particle materials,were embedded in the damaged areas of the RSFs,increasing the frictional force at the interface between the RSF and CGFB matrix.The shape variability of the RSFs caused interlocking between the RSFs and the matrix.Both mechanisms strengthened the bridging effect of the RSFs in the CGFB,thereby improving the damage resistance capability of CGFB.The excellent damage resistance occurred at an RSF content of 0.5%;thus,this content is recommended for engineering applications.
基金funded by Thailand Research Fund under Research and Researchers for Industries (contract no. MSD62I0063)
文摘This research addresses the growing demand for high-performance protective materials against high-velocity projectile impacts.The performance of multi-layered steel fiber-reinforced mortar(SFRM)panels with varying thicknesses and air gaps,was experimentally investigated under single and repeated impacts of 7.62×51 mm bullets fired from a distance of 50 m.The impact events were recorded using a high-speed camera at 40000 fps.Panel performance was assessed in terms of failure modes,kinetic energy absorption,spalling diameter,and percentage of back-face damage area,and weight loss.Results showed that panel configuration significantly influenced performance.Panel P10,with 70 mm SFRM thickness and 20 mm air gaps,provided the highest resistance,dissipating 5223 J of kinetic energy and preventing back-face damage.In contrast,P7,which absorbed 4476 J,presented a back damage area percentage of 8.93%after three impacts.Weight loss analysis further confirmed durability improvements,with P10 showing only 1.53%cumulative loss compared to 3.26%in P7.The inclusion of wider air gaps enhanced energy dissipation and reduced damage.Comparison between single and repeated impacts demonstrated the sustained resistance of high-performance panels,with P10 maintaining minimal degradation across three consecutive impacts.These findings highlight the potential of multi-layer SFRM panels to enhance ballistic resistance,making them suitable for military,security,and civilian protective applications requiring long-term durability.
基金Project(51078294)supported by the National Natural Science Foundation of ChinaProject(201101411100025)supported by the Doctoral Fund of Ministry of Education of China
文摘An experimental study on the compressive behavior of steel fiber reinforced concrete-filled steel tube columns is presented. Specimens were tested to investigate the effects of the concrete strength, the thickness of steel tube and the steel fiber volume fraction on the ultimate strength and the ductility. The experimental results indicate that the addition of steel fibers in concrete can significantly improve the ductility and the energy dissipation capacity of the concrete-filled steel tube columns and delay the local buckling of the steel tube, but has no obvious effect on the failure mode. It has also been found that the addition of steel fibers is a more effective method than using thicker steel tube in enhancing the ductility, and more advantageous in the case of higher strength concrete. An analytical model to estimate the load capacity is proposed for steel tube columns filled with both plain concrete and steel fiber reinforced concrete. The predicted results are in good agreement with the experimental ones obtained in this work and literatures.
文摘The complete splitting process of steel fiber reinforced concrete （SFRC） at intermediate strain rate was studied by experiment. The basic information of a self-developed SFRC dynamic test system matching with lnstron 1342 materials testing machine was given, and the experiment principle and the loading mode of cubic split specimen were introduced. During the experiment, 30 cubes of 150 mm×150 mm×150 mm and 36 cubes of 100 mm×100 mm×100 mm, designed and prepared according to C20 class SFRC with different volume fractions of steel fiber （0, 1%, 2%, 3%, 4%） were tested and analyzed. At the same time, the size effect of SFRC at intermediate strain rate was investigated. The experimental study indicates that SFRC size effect is not influenced by the loading speed or strain rate. When the steel fiber content increases from 0 to 4%, the splitting strength of SFRC increases from 100% to 261%, i.e. increasing by 161% compared with that of the common concrete. The loading rate increases from 1.33 kN/s to 80.00 kN/s, and the splitting tensile strength increases by 43.55%.
基金Project(51134003) supported by the National Natural Science Foundation of China
文摘Isothermal sintering experiments were performed on the 316 L stainless steel fiber felts with fiber diameters of 8 μm and20 μm. Surface morphologies of the sintered specimens were investigated by using scanning electron microscopy(SEM) and optical microscopy. The results show that the amount of the sintering necks and the relative densities of the fiber felt increase with the increasing of both the sintering temperature and the sintering time. And the activation energies estimated present a decline at high relative densities for both 8 μm and 20 μm fiber felts. Moreover, the sintering densification of the fiber felts is dominated by volume diffusion mechanism at low temperature and relative densities. As more grain boundaries are formed at higher temperature and relative density, grain boundary diffusion will also contribute to the densification of the specimen.
基金Project(50578027) supported by the National Natural Science Foundation of China
文摘The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interface. Fatigue properties of the composite beam under the action of negative moment were experimentally studied. Through inverted loading mode the load-beating state of a composite beam was simulated under the action of negative moment. With the ratios of constructional bars being 0, 0.082% and 0.164% respectively as parameters, the effects of constructional bars on the properties of composite beam, such as fatigue life, crack propagation, rigidity loss as well as damage behavior of bonding interface, were studied. The mechanism of the constructional bars on the fatigue properties of the composite beams and the restriction mechanism of crack widths and rigidity loss were analyzed. The test results show that the constructional bars can enhance the shear resistance of the bonding interface between composite layer and old concrete beam and restrict expanding of steel fiber reinforced self-stressing concrete, which are beneficial to synergistic action of composite layer and old concrete beam, to reducing the stress amplitude of bars and the crack width of composite layer, and to increasing the durability and fatigue life of the composite beam.
