[Objective]The construction of weirs changes the hydraulic characteristics of rivers and affects the structure of phytoplankton communities and the health of aquatic ecosystems in the river.This study aims to explore ...[Objective]The construction of weirs changes the hydraulic characteristics of rivers and affects the structure of phytoplankton communities and the health of aquatic ecosystems in the river.This study aims to explore the nonlinear response relationship between phytoplankton community structure and its driving factors in spring and autumn in Furong Creek under the construction of cascade weirs.[Methods]The structure of phytoplankton communities and related environmental factors were investigated in Furong Creek from 2023 to 2024.This study focused on the analysis of the changes of nutrient concentrations and biomass of phytoplankton in autumn and spring within the same dry season in Furong Creek.Redundancy analysis was used to identify the key factors influencing the structure of phytoplankton communities.The MIKE 11 model was employed to simulate the hydrodynamic changes in the river.Combined with total nitrogen and permanganate index,a GAM model of phytoplankton diversity index and hydrodynamic factors was developed,and the change of phytoplankton diversity after the optimized layout of the cascade weirs was fitted.[Results]The result showed that the annual average value of Shannon-Wiener diversity index of phytoplankton in Furong Creek was 2.79,which was in a state of mild pollution.A total of 239 species from 95 genera in 8 phyla were identified.Among the phytoplankton,Chlorophyta was the dominant group throughout the year in Furong Creek,followed by Bacillariophyta and Cyanophyta.The cell abundance of phytoplankton ranged from 3.11 to 20.64 mg/L and from 0.23 to 6.31 mg/L in spring and autumn,which indicated a clear seasonal succession of phytoplankton community structure.Compared with autumn,the relative abundance of Cyanophyta significantly decreased in spring across the whole river section,while Chrysophyta and Dinophyta showed significant increase at some monitoring sites,leading to water bloom phenomenon and a noticeable decline in the diversity of phytoplankton.The dominant species in the water bodies throughout the year were Cyclotella catenata,Chlorella vulgaris,Scenedesmus bijuga,Scenedesmus quadricauda,Chroomonas acuta,Cryptomonas ovata,and Cryptomonas erosa.Redundancy analysis(RDA)showed that hydrodynamic factors(v,h)and water environmental factors(TN,COD_(Mn))were the main influencing factors of phytoplankton community structure.[Conclusion]The result show that the nutrient concentration,phytoplankton biomass,and density in Furong Creek in spring are significantly higher than in autumn.The GAM model,constructed by combining hydrodynamic and environmental factors,can effectively reflect the nonlinear relationship between phytoplankton diversity index and its driving factors.In spring,with an increase in nutrient concentration,the habitat conditions of low flow speed and high water depths formed by overflow weirs will lead to a decrease in the Shannon-Wiener index of phytoplankton and an intensified risk of eutrophication.However,a reasonable layout scheme of cascade weirs will improve the diversity of phytoplankton and reduce the risk of eutrophication in the river.The findings of this study can help deepen the understanding of the ecological and environmental effects of cascade weir construction in the river.展开更多
With the constantly changing engineering construction sector,the detection accuracy of conventional electrical resistivity tomography(ERT)is no longer sufficient.A multichannel electrode design(MERT)-based ERT is intr...With the constantly changing engineering construction sector,the detection accuracy of conventional electrical resistivity tomography(ERT)is no longer sufficient.A multichannel electrode design(MERT)-based ERT is introduced in this paper to address the growing need for resolution.The imaging accuracy of the ERT method is improved through the collection of apparent resistivity data in various directions by measuring the potential diff erence between diff erent channels.Numerical simulation results of the inclined high-resistivity anomaly model reveal that MERT is a precise representation of the shape,inclined direction,and buried depth of the anomaly,with thoroughfare M2N2 producing the most precise forward and inverse results.Based on the analysis results of the model resolution matrix,when the buried depth of power supply points and the gap between potential acquisition points are 30%-90%and 30%-60%of the electrode distance,respectively,the MERT approach yields superior detection outcomes.The detection eff ect of the MERT method on anomalous bodies with diff erent burial depths under the optimal parameters also indicates that the MERT method can obtain richer potential change information with higher resolution in deep areas compared to the ERT method.With the implementation of the MERT approach,the scope of applications for ERT is expanded,the accuracy of ERT detection is increased,and the progress of near-surface fine detection is positively infl uenced.展开更多
To reduce the shielding effect of hardened layers on electrical resistivity tomography,a ratio method based on the distortion correction principle and the isolation coefficient is proposed.The effects of the resistivi...To reduce the shielding effect of hardened layers on electrical resistivity tomography,a ratio method based on the distortion correction principle and the isolation coefficient is proposed.The effects of the resistivity and thickness of hardened concrete layers on the detection of target objects are explored.Both numerical simulations and indoor tank tests indicate that when the ratio method is employed to correct the original collected data,the maximum allowable error for the isolation coefficient should not exceed 1%.Notably,when the ratio of hardened layer thickness to electrode spacing does not exceed 1,correction through this method significantly enhances the recognition capability of target objects.However,when the hardened layer thickness is greater than the electrode spacing by a factor of 2 or more,the ratio method cannot achieve satisfactory results.The case study of flood control engineering detection in the Zhangxi section of the Huangpen River in Dongzhi County demonstrates that the detection effect after correction by the ratio method is comparable to that for the adjacent unhardened pavement,and the influence of the hardened layer is obviously weakened,resulting in more reliable results.展开更多
In order to reduce the agglomeration of nanographene and improve its dispersibility,six silane coupling agents were used to modify the surface of the nanographene particles.Visual inspection,Fourier-transform infrared...In order to reduce the agglomeration of nanographene and improve its dispersibility,six silane coupling agents were used to modify the surface of the nanographene particles.Visual inspection,Fourier-transform infrared spectroscopy,transmission electron microscopy,Raman spectroscopy,and X-ray diffraction were employed to evaluate the dispersion properties of the resulting graphene in an aqueous solution of silane coupling agents.Results show that all six types of silane coupling agents are efficient in promoting the dispersion of graphene in aqueous solutions,and no obvious sedimentation of the graphene dispersion solution is observed after a stationary storage period of 30 d.Taking 3-aminopropyltriethoxysilane(KH-550)as an example,after the graphene is dispersed in the KH-550 aqueous solution,the carboxyl group on the surface of the graphene reacts with the KH-550 amino group to form an amide bond,and KH-550 is successfully grafted onto the graphene surface.Polar functional groups ionize in water,creating an electrostatic repulsion effect,or hydrophilic functional groups form hydrogen bonds with water molecules,which is believed to improve the dispersion stability of graphene.The dispersed graphene is curled and contains many folds.Each fold has about three or four layers,with an interlayer spacing of about 0.65 nm.The dispersed graphene also has a complete lattice and a reduced number of defects.Nanographene disperses well in silane coupling agent aqueous solutions and can,therefore,be used to prepare cement-based composites.展开更多
To verify the accuracy of weir and orifice formula and analyze the hydraulic characteristics of exchange flow in a manhole,a three-dimensional numerical model was proposed to assess the exchange flow rate between the ...To verify the accuracy of weir and orifice formula and analyze the hydraulic characteristics of exchange flow in a manhole,a three-dimensional numerical model was proposed to assess the exchange flow rate between the surface and sewer pipe systems based on the real-world scale model.The hydrodynamic model is based on the three-dimensional Navier-Stokes equations including the standard k-εmodel for turbulence processes,and the volume of fluid(VOF)method for capturing the free surface.The results of the computational fluid dynamics(CFD)simulation are compared with the conventional overflow equations,showing that the weir and orifice formula is appropriate to determine the exchange flow rate between two systems in this specific study case.Streamlines and velocity contours at the center profile under both the inflow and surcharge conditions show that the exchange flow is directly related to the water level on the surface and the junction area between the manhole and right pipe.The results demonstrate the potential application of CFD in analyzing the interaction of urban flood flows,which can provide much clearer details of the interaction process.展开更多
In order to establish the constitutive relationship of high-ductility cementitious composites(HDCCs)under uniaxial tensile load and to guide the structural design of HDCCs,based on the analysis of the existing uniaxia...In order to establish the constitutive relationship of high-ductility cementitious composites(HDCCs)under uniaxial tensile load and to guide the structural design of HDCCs,based on the analysis of the existing uniaxial tensile constitutive relationship and ideal elastoplastic linear strain-hardening model,a bilinear tensile constitutive equation of HDCCs was proposed.The points of nominal initial cracking and nominal maximum stress were adopted as control points of the line segment,and the constitutive relationship of HDCCs was established.Five series of uniaxial tensile stress-strain curves of HDCCs were combined to perform an experimental application of the constitutive equation,along with an analysis of the key parameters.The experimental results confirm the ability of the constitutive equation to overcome the problem of insufficient or excessive redundancy of existing models in terms of calculation bearing capacity.Specifically,the measured maximum stress value is larger than the nominal value,and the ratio between the two values ranges from 1.08 to 1.22.Additionally,the tensile strain at the softening point obtained by fitting a straight line with the valley points of the strain-hardening stage curve is greater than or equal to the tensile strain at the measured maximum stress point and the ratio of the fitted values to the measured values ranges from 1.00 to 1.19.展开更多
High-density polyethylene(HDPE)film leakage location detection is frequently accomplished using the double-electrode technique.The electric potential and potential difference are the main physical parameters in the do...High-density polyethylene(HDPE)film leakage location detection is frequently accomplished using the double-electrode technique.The electric potential and potential difference are the main physical parameters in the double-electrode approach.Due to the impact of the complex geoelectric environment,the electric potential and the electric potential difference are not sensitive enough to respond to minimal leakage.The tiny leaking area cannot be precisely located using the electric potential and electric potential difference.Using the COMSOL Multiphysics software,this study created a standard geoelectric model of the double-electrode method.We calculated a new parameter—the G parameter through secondary electric potential difference—based on the response characteristics of the electric potential and the electric potential difference while the HDPEfilm is leaking.The experiment demonstrates that the G parameter is more sensitive than the electric potential and electric potential difference for detecting the leaking area of HDPE film.The G parameter is more effective at detecting leakage than the electric potential and electric potential difference.The results of this study can be used to locate HDPEfilm leakage areas in a landfill.展开更多
To investigate the effect of fiber types on bending and tensile properties of high-strength,high-ductility cementitious composites( HS-HDCCs), ultra-high-molecular-weight polyethylene( PE) fibers,polyvinyl alcohol( PV...To investigate the effect of fiber types on bending and tensile properties of high-strength,high-ductility cementitious composites( HS-HDCCs), ultra-high-molecular-weight polyethylene( PE) fibers,polyvinyl alcohol( PVA) fibers,and copper-plated micro steel fibers were selected as the reinforcement materials. The bending and tensile properties of HS-HDCCs with different fibers with a volume fraction of 2% were studied. The results indicate that PE,PVA,micro steel,and PVA-PE hybrid fibers impart varying degrees of toughening and improve the tensile strength. During the tensile and bending processes,HS-HDCCs with micro steel fibers exhibit a strain-softening phenomenon. HS-HDCCs with PVA fibers or with PVA-PE hybrid fibers can achieve multiple cracking behaviors and strain hardening phenomenon to a certain extent and show slight high-ductility characteristics. HS-HDCCs with PE fibers exhibit multiple cracking behavior and strain hardening phenomenon and show significant high-ductility characteristics. The test results can provide a basis for selecting fibers suitable for HS-HDCCs reinforcement.展开更多
To obtain the design parameters of the structure made by ecological high ductility cementitious composites(Eco-HDCC),the effects of curing age on the compressive and tensile stress-strain relationships were studied.Th...To obtain the design parameters of the structure made by ecological high ductility cementitious composites(Eco-HDCC),the effects of curing age on the compressive and tensile stress-strain relationships were studied.The reaction degree of fly ash,non-evaporable water content and the pH value in pore solution were calculated to reveal the mechanical property.The results indicate that as the curing age increases,the peak compressive strength,peak compressive strain and ultimate tensile strength of Eco-HDCC increase.However,the ultimate compressive strain and ultimate tensile strain of Eco-HDCC decrease with the increase in curing age.Besides,as the curing age increases,the reaction degree of fly ash and non-evaporable water content in Eco-HDCC increase,while the pH value in the pore solution of Eco-HDCC decreases.Finally,the simplified compressive and tensile stress-strain constitutive relationship models of Eco-HDCC with a curing age of 28 d were suggested for the structure design safety.展开更多
To explore the tensile property parameters in the structural design of bridge deck link slabs made by ecological high ductility cementitious composites (Eco-HDCC), the tensile properties of Eco-HDCC exposed to interac...To explore the tensile property parameters in the structural design of bridge deck link slabs made by ecological high ductility cementitious composites (Eco-HDCC), the tensile properties of Eco-HDCC exposed to interactive freeze-thaw-carbonation cycles and single carbonation cycles were studied. The carbonation front of Eco-HDCC was determined by X-ray diffraction and differential scanning calorimetry-thermal gravimetric methods. Results indicate that the carbonation front of Eco-HDCC after interaction tests is deeper than that of Eco-HDCC after single carbonation tests. In addition, the ultimate tensile strength for Eco-HDCC shows an increasing trend after the interaction of 1 to 5 cycles compared with that of virgin specimens, while the ultimate tensile strength decreases after the interaction of 10 to 15 cycles. For single carbonation tests, the ultimate tensile strength of Eco-HDCC increases as cycles increase. After being subjected to interaction and single carbonation environments, both the ultimate tensile strain and tensile strain energy of Eco-HDCC decrease as cycles increase, and the decrease degrees of Eco-HDCC after interaction cycles are larger than those of Eco-HDCC after single carbonation. For general consideration, the tensile stress-strain relationship of Eco-HDCC after the interaction of 15 cycles can be adopted in the design of bridge deck link slabs for the purpose of safety.展开更多
文摘[Objective]The construction of weirs changes the hydraulic characteristics of rivers and affects the structure of phytoplankton communities and the health of aquatic ecosystems in the river.This study aims to explore the nonlinear response relationship between phytoplankton community structure and its driving factors in spring and autumn in Furong Creek under the construction of cascade weirs.[Methods]The structure of phytoplankton communities and related environmental factors were investigated in Furong Creek from 2023 to 2024.This study focused on the analysis of the changes of nutrient concentrations and biomass of phytoplankton in autumn and spring within the same dry season in Furong Creek.Redundancy analysis was used to identify the key factors influencing the structure of phytoplankton communities.The MIKE 11 model was employed to simulate the hydrodynamic changes in the river.Combined with total nitrogen and permanganate index,a GAM model of phytoplankton diversity index and hydrodynamic factors was developed,and the change of phytoplankton diversity after the optimized layout of the cascade weirs was fitted.[Results]The result showed that the annual average value of Shannon-Wiener diversity index of phytoplankton in Furong Creek was 2.79,which was in a state of mild pollution.A total of 239 species from 95 genera in 8 phyla were identified.Among the phytoplankton,Chlorophyta was the dominant group throughout the year in Furong Creek,followed by Bacillariophyta and Cyanophyta.The cell abundance of phytoplankton ranged from 3.11 to 20.64 mg/L and from 0.23 to 6.31 mg/L in spring and autumn,which indicated a clear seasonal succession of phytoplankton community structure.Compared with autumn,the relative abundance of Cyanophyta significantly decreased in spring across the whole river section,while Chrysophyta and Dinophyta showed significant increase at some monitoring sites,leading to water bloom phenomenon and a noticeable decline in the diversity of phytoplankton.The dominant species in the water bodies throughout the year were Cyclotella catenata,Chlorella vulgaris,Scenedesmus bijuga,Scenedesmus quadricauda,Chroomonas acuta,Cryptomonas ovata,and Cryptomonas erosa.Redundancy analysis(RDA)showed that hydrodynamic factors(v,h)and water environmental factors(TN,COD_(Mn))were the main influencing factors of phytoplankton community structure.[Conclusion]The result show that the nutrient concentration,phytoplankton biomass,and density in Furong Creek in spring are significantly higher than in autumn.The GAM model,constructed by combining hydrodynamic and environmental factors,can effectively reflect the nonlinear relationship between phytoplankton diversity index and its driving factors.In spring,with an increase in nutrient concentration,the habitat conditions of low flow speed and high water depths formed by overflow weirs will lead to a decrease in the Shannon-Wiener index of phytoplankton and an intensified risk of eutrophication.However,a reasonable layout scheme of cascade weirs will improve the diversity of phytoplankton and reduce the risk of eutrophication in the river.The findings of this study can help deepen the understanding of the ecological and environmental effects of cascade weir construction in the river.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFC3000103)the National Natural Science Foundation of China(Grant No.41504081)。
文摘With the constantly changing engineering construction sector,the detection accuracy of conventional electrical resistivity tomography(ERT)is no longer sufficient.A multichannel electrode design(MERT)-based ERT is introduced in this paper to address the growing need for resolution.The imaging accuracy of the ERT method is improved through the collection of apparent resistivity data in various directions by measuring the potential diff erence between diff erent channels.Numerical simulation results of the inclined high-resistivity anomaly model reveal that MERT is a precise representation of the shape,inclined direction,and buried depth of the anomaly,with thoroughfare M2N2 producing the most precise forward and inverse results.Based on the analysis results of the model resolution matrix,when the buried depth of power supply points and the gap between potential acquisition points are 30%-90%and 30%-60%of the electrode distance,respectively,the MERT approach yields superior detection outcomes.The detection eff ect of the MERT method on anomalous bodies with diff erent burial depths under the optimal parameters also indicates that the MERT method can obtain richer potential change information with higher resolution in deep areas compared to the ERT method.With the implementation of the MERT approach,the scope of applications for ERT is expanded,the accuracy of ERT detection is increased,and the progress of near-surface fine detection is positively infl uenced.
基金National Key Research and Development Program of China(No.2021YFC3000103).
文摘To reduce the shielding effect of hardened layers on electrical resistivity tomography,a ratio method based on the distortion correction principle and the isolation coefficient is proposed.The effects of the resistivity and thickness of hardened concrete layers on the detection of target objects are explored.Both numerical simulations and indoor tank tests indicate that when the ratio method is employed to correct the original collected data,the maximum allowable error for the isolation coefficient should not exceed 1%.Notably,when the ratio of hardened layer thickness to electrode spacing does not exceed 1,correction through this method significantly enhances the recognition capability of target objects.However,when the hardened layer thickness is greater than the electrode spacing by a factor of 2 or more,the ratio method cannot achieve satisfactory results.The case study of flood control engineering detection in the Zhangxi section of the Huangpen River in Dongzhi County demonstrates that the detection effect after correction by the ratio method is comparable to that for the adjacent unhardened pavement,and the influence of the hardened layer is obviously weakened,resulting in more reliable results.
基金The National Key R&D Program of China(No.2018YFC0406701)the National Natural Science Foundation of China(No.51778133,51739008).
文摘In order to reduce the agglomeration of nanographene and improve its dispersibility,six silane coupling agents were used to modify the surface of the nanographene particles.Visual inspection,Fourier-transform infrared spectroscopy,transmission electron microscopy,Raman spectroscopy,and X-ray diffraction were employed to evaluate the dispersion properties of the resulting graphene in an aqueous solution of silane coupling agents.Results show that all six types of silane coupling agents are efficient in promoting the dispersion of graphene in aqueous solutions,and no obvious sedimentation of the graphene dispersion solution is observed after a stationary storage period of 30 d.Taking 3-aminopropyltriethoxysilane(KH-550)as an example,after the graphene is dispersed in the KH-550 aqueous solution,the carboxyl group on the surface of the graphene reacts with the KH-550 amino group to form an amide bond,and KH-550 is successfully grafted onto the graphene surface.Polar functional groups ionize in water,creating an electrostatic repulsion effect,or hydrophilic functional groups form hydrogen bonds with water molecules,which is believed to improve the dispersion stability of graphene.The dispersed graphene is curled and contains many folds.Each fold has about three or four layers,with an interlayer spacing of about 0.65 nm.The dispersed graphene also has a complete lattice and a reduced number of defects.Nanographene disperses well in silane coupling agent aqueous solutions and can,therefore,be used to prepare cement-based composites.
基金The National Natural Science Foundation of China(No.51979040)。
文摘To verify the accuracy of weir and orifice formula and analyze the hydraulic characteristics of exchange flow in a manhole,a three-dimensional numerical model was proposed to assess the exchange flow rate between the surface and sewer pipe systems based on the real-world scale model.The hydrodynamic model is based on the three-dimensional Navier-Stokes equations including the standard k-εmodel for turbulence processes,and the volume of fluid(VOF)method for capturing the free surface.The results of the computational fluid dynamics(CFD)simulation are compared with the conventional overflow equations,showing that the weir and orifice formula is appropriate to determine the exchange flow rate between two systems in this specific study case.Streamlines and velocity contours at the center profile under both the inflow and surcharge conditions show that the exchange flow is directly related to the water level on the surface and the junction area between the manhole and right pipe.The results demonstrate the potential application of CFD in analyzing the interaction of urban flood flows,which can provide much clearer details of the interaction process.
基金The National Key Research and Development Program of China(No.2018YFC0406701)the National Natural Science Foundation of China(No.51778133,51739008)
文摘In order to establish the constitutive relationship of high-ductility cementitious composites(HDCCs)under uniaxial tensile load and to guide the structural design of HDCCs,based on the analysis of the existing uniaxial tensile constitutive relationship and ideal elastoplastic linear strain-hardening model,a bilinear tensile constitutive equation of HDCCs was proposed.The points of nominal initial cracking and nominal maximum stress were adopted as control points of the line segment,and the constitutive relationship of HDCCs was established.Five series of uniaxial tensile stress-strain curves of HDCCs were combined to perform an experimental application of the constitutive equation,along with an analysis of the key parameters.The experimental results confirm the ability of the constitutive equation to overcome the problem of insufficient or excessive redundancy of existing models in terms of calculation bearing capacity.Specifically,the measured maximum stress value is larger than the nominal value,and the ratio between the two values ranges from 1.08 to 1.22.Additionally,the tensile strain at the softening point obtained by fitting a straight line with the valley points of the strain-hardening stage curve is greater than or equal to the tensile strain at the measured maximum stress point and the ratio of the fitted values to the measured values ranges from 1.00 to 1.19.
基金supported by the National Key Research and Development Program of China (Grant Nos. 2019YFC1510802 and 2019YFC1804302)the National Natural Science Foundation of China (Grant No. 41504081)the Fundamental Research Funds for the Central Universities (Grant No. 2019B17214)。
文摘High-density polyethylene(HDPE)film leakage location detection is frequently accomplished using the double-electrode technique.The electric potential and potential difference are the main physical parameters in the double-electrode approach.Due to the impact of the complex geoelectric environment,the electric potential and the electric potential difference are not sensitive enough to respond to minimal leakage.The tiny leaking area cannot be precisely located using the electric potential and electric potential difference.Using the COMSOL Multiphysics software,this study created a standard geoelectric model of the double-electrode method.We calculated a new parameter—the G parameter through secondary electric potential difference—based on the response characteristics of the electric potential and the electric potential difference while the HDPEfilm is leaking.The experiment demonstrates that the G parameter is more sensitive than the electric potential and electric potential difference for detecting the leaking area of HDPE film.The G parameter is more effective at detecting leakage than the electric potential and electric potential difference.The results of this study can be used to locate HDPEfilm leakage areas in a landfill.
基金The National Key Research and Development Program of China(No.2016YFC0401610)the National Natural Science Foundation of China(No.51778133,51739008,51438003)
文摘To investigate the effect of fiber types on bending and tensile properties of high-strength,high-ductility cementitious composites( HS-HDCCs), ultra-high-molecular-weight polyethylene( PE) fibers,polyvinyl alcohol( PVA) fibers,and copper-plated micro steel fibers were selected as the reinforcement materials. The bending and tensile properties of HS-HDCCs with different fibers with a volume fraction of 2% were studied. The results indicate that PE,PVA,micro steel,and PVA-PE hybrid fibers impart varying degrees of toughening and improve the tensile strength. During the tensile and bending processes,HS-HDCCs with micro steel fibers exhibit a strain-softening phenomenon. HS-HDCCs with PVA fibers or with PVA-PE hybrid fibers can achieve multiple cracking behaviors and strain hardening phenomenon to a certain extent and show slight high-ductility characteristics. HS-HDCCs with PE fibers exhibit multiple cracking behavior and strain hardening phenomenon and show significant high-ductility characteristics. The test results can provide a basis for selecting fibers suitable for HS-HDCCs reinforcement.
基金The National Natural Science Foundations of China(No.51778133)the Transportation Science&Technology Project of Fujian Province(No.2017Y057)+1 种基金the China Railway Project(No.2017G007-C)Foundation of the China Scholarship Council(No.201906090163).
文摘To obtain the design parameters of the structure made by ecological high ductility cementitious composites(Eco-HDCC),the effects of curing age on the compressive and tensile stress-strain relationships were studied.The reaction degree of fly ash,non-evaporable water content and the pH value in pore solution were calculated to reveal the mechanical property.The results indicate that as the curing age increases,the peak compressive strength,peak compressive strain and ultimate tensile strength of Eco-HDCC increase.However,the ultimate compressive strain and ultimate tensile strain of Eco-HDCC decrease with the increase in curing age.Besides,as the curing age increases,the reaction degree of fly ash and non-evaporable water content in Eco-HDCC increase,while the pH value in the pore solution of Eco-HDCC decreases.Finally,the simplified compressive and tensile stress-strain constitutive relationship models of Eco-HDCC with a curing age of 28 d were suggested for the structure design safety.
基金The National Natural Science Foundation of China(No.51778133)the National Basic Research Program of China(973Program)(No.2015CB655102)+1 种基金the Fundamental Research Funds for the Central Universities(No.3212009403)the China Railway Project(No.2017G007-C)
文摘To explore the tensile property parameters in the structural design of bridge deck link slabs made by ecological high ductility cementitious composites (Eco-HDCC), the tensile properties of Eco-HDCC exposed to interactive freeze-thaw-carbonation cycles and single carbonation cycles were studied. The carbonation front of Eco-HDCC was determined by X-ray diffraction and differential scanning calorimetry-thermal gravimetric methods. Results indicate that the carbonation front of Eco-HDCC after interaction tests is deeper than that of Eco-HDCC after single carbonation tests. In addition, the ultimate tensile strength for Eco-HDCC shows an increasing trend after the interaction of 1 to 5 cycles compared with that of virgin specimens, while the ultimate tensile strength decreases after the interaction of 10 to 15 cycles. For single carbonation tests, the ultimate tensile strength of Eco-HDCC increases as cycles increase. After being subjected to interaction and single carbonation environments, both the ultimate tensile strain and tensile strain energy of Eco-HDCC decrease as cycles increase, and the decrease degrees of Eco-HDCC after interaction cycles are larger than those of Eco-HDCC after single carbonation. For general consideration, the tensile stress-strain relationship of Eco-HDCC after the interaction of 15 cycles can be adopted in the design of bridge deck link slabs for the purpose of safety.
