Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may ...Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.展开更多
This study meticulously examined the compaction and sulfate erosion resistance of cement-stabilized materials incorporating recycled brick-concrete aggregate (RBCA).To explore the effects of recycled brick aggregate (...This study meticulously examined the compaction and sulfate erosion resistance of cement-stabilized materials incorporating recycled brick-concrete aggregate (RBCA).To explore the effects of recycled brick aggregate (RBA) with varying particle sizes,three size ranges (4.75-9.5 mm,9.5-19 mm and 19-31.5 mm) were used to replace 20% of the corresponding particle sizes of recycled concrete aggregate (RCA) in cement-stabilized materials.The findings indicated that cement-stabilized materials utilizing RBA and RCA exhibited a lower maximum dry density and a higher optimum moisture content than natural aggregate cement-stabilized materials.The use of RBA with a particle size of 4.75-9.5 mm resulted in a lower maximum dry density and a higher optimum moisture content than 9.5-19 mm and 19-31.5 mm.Furthermore,the 7-day unconfined compressive strength of RBCA cement-stabilized materials with RBA of 4.75-9.5 mm demonstrated superior results compared to those with larger particle sizes.Regarding sulfate erosion resistance,the mass loss and unconfined compressive strength loss of the RBCA cement-stabilized materials at 56 days were highest for the 19-31.5 mm particle size of the RBA.In terms of compaction and sulfate resistance,it is recommended to use 4.75-19 mm RBA in RBCA cement-stabilized materials.展开更多
The cement dry jet mixing method has been used to reinforce soft cohesive ground to increase the strength of soft cohesive ground and to decrease its deformation. The study briefly introduces the curing mechanism of c...The cement dry jet mixing method has been used to reinforce soft cohesive ground to increase the strength of soft cohesive ground and to decrease its deformation. The study briefly introduces the curing mechanism of cement-soil,presents the factors of influencing on compressive strength,mainly analyses the factors including cement mixing ratio,cement strength grade,curing age,moisture content and soil texture and puts forward some rational proposals at last.展开更多
The base layer constructed by cement-stabilized macadam(CSM)has been widely used in highway construction due to its low elasticity deformation and high carrying capacity.As a bearing layer,the CSM base is not exempt f...The base layer constructed by cement-stabilized macadam(CSM)has been widely used in highway construction due to its low elasticity deformation and high carrying capacity.As a bearing layer,the CSM base is not exempt from fatigue cracking under cyclic loading in the service process.Cracks in the base will create irreversible structural and functional deficiencies,such as the potential for reflective cracking of subsequently placed asphalt concrete overlays.The fracture of the base will shorten the service life of the pavement.The quality of the CSM base is directly related to the bearing capacity and integrity of the whole pavement structure.It is of practical significance to further study the fatigue failure behavior of CSM material for the long-term performance of the pavement.The CSM material is a typical heterogeneous multiphase composite.On the mesoscale,CSM consists of aggregate,cement mortar,pores,and the interface transitional zone(ITZ).On the microscale,the hardened mortar contains a large number of capillary pores,unhydrated particles,hydrated crystals,etc.,which makes the spatial distribution of its material properties stochastic.In addition,cement hydration,dry shrinkage,and temperature shrinkage can also produce micro-crack defects in cement mortar.These microcracks will have crossscale evolution under load,resulting in structural fracture.Macroscopic complex deformation and mechanical response are the reflections of its microscopic and even mesoscale composition and structure.This study summarized the existing studies on the mesoscopic properties of CSM materials,respectively from the three aspects of mesostructure,structural characterization,and mesoscale fatigue damage analysis,to help the development of long-life pavement.The future research direction is to explore the mesoscale characteristics of CSM using multiscale representation and analysis methods,to establish the connection between mesoscale characteristics and macroscopic mechanical properties.展开更多
The influence of curing temperature on the strength development of cement-stabilized mud has been well documented in terms of strength-increase rate and ultimate strength.However,the strength development model is not ...The influence of curing temperature on the strength development of cement-stabilized mud has been well documented in terms of strength-increase rate and ultimate strength.However,the strength development model is not mature for the extremely early stages.In addition,there is a lack of studies on quality control methods based on early-stage strength development.This paper presents a strength model for cement-stabilized mud to address these gaps,considering various curing temperatures and early-stage behaviors.In this study,a series of laboratory experiments was conducted on two types of muds treated with Portland blast furnace cement and ordinary Portland cement under four different temperatures.The results indicate that elevated temperatures expedite strength development and lead to higher long-term strength.The proposed model,which combines a three-step conversion process and a hyperbolic model at the reference temperature,enables accurate estimate of the strength development for cement-treated mud with any proportions cured under various temperatures.With this model,a practical early quality control method is introduced for applying cement-stabilized mud in field projects.The back-analysis parameters obtained from a 36-h investigation at temperature of 60C demonstrated a sufficient accuracy in predicting strength levels in practical applications.展开更多
In recent years,the amount of waste generated during milling has increased dramatically,and improper disposal poses a significant environmental challenge.To mitigate environmental pollution and enhance the road perfor...In recent years,the amount of waste generated during milling has increased dramatically,and improper disposal poses a significant environmental challenge.To mitigate environmental pollution and enhance the road performance of emulsified asphalt cold recycled mixtures(ECRM),this study employed recycled asphalt pavement(RAP)and reclaimed inorganic binder stabilized aggregate(RAI)as dual recycled materials for ECRM preparation.The blending ratios of reclaimed base and surface layer mixtures significantly influence ECRM's performance,with adjusted proportions substantially improving compressive strength and dynamic modulus.Firstly,three distinct proportioning options were developed for the recycled materials.Mix designs incorporating varying RAP/RAI ratios were used to determine the optimal mix parameters:moisture content,cement dosage,and emulsified asphalt content.Subsequently,comprehensive performance evaluations were conducted through high-temperature wheel tracking tests,freeze-thaw splitting tests,uniaxial compression tests,and dynamic modulus measurements to analyze the pavement characteristics of the three ECRM formulations.Experimental results demonstrate:Compared with ECRM with a blending ratio of RAP:RAI:new aggregate=30:50:20(Option 1),the dynamic stability,freeze-thaw splitting strength ratio,compressive strength,and compressive resilient modulus of ECRM under Option 3(RAP:RAI:new aggregate=50:30:20)decreased by 31.8%,5.2%,16.4%,and 13.1%,respectively.This indicates that increasing RAP content while reducing RAI proportion enhances the tensile strength of ECRM,yet adversely affects its high-temperature stability,moisture resistance,and compressive performance.This work not only addresses the challenge of jointly utilizing asphalt pavement waste and base waste,but also provides a cost-effective and sustainable method for the stable application of milling material resources in road engineering.展开更多
A total of 26 myopic patients （52 eyes） underwent laser in situ keratomileusis. In vivo confocal microscopy revealed that most of the regenerated corneal subbasal nerve fibers in the comeal flap originated from the ...A total of 26 myopic patients （52 eyes） underwent laser in situ keratomileusis. In vivo confocal microscopy revealed that most of the regenerated corneal subbasal nerve fibers in the comeal flap originated from the stump of corneal subbasal nerve fibers outside the ablation zone and extended towards the center of the cornea in all patients. Meanwhile, new fibers were also found to directly regenerate from deep in the stroma in some cases. Approximately 94% of regenerated corneal subbasal nerve fibers （73/78 eyes） regrew vertically into the peripheral central 6-mm circle area 1 month after surgery, 78% （28/36 eyes） grew into the central 3 6 mm area at 2 months, and 23% into the central 3-mm circle area at 3 months. In addition, there was no significant difference in corneal subbasal nerve fiber regenerative capacity between the basic fibroblast growth factor group and the 20% （vN） deproteinized extract of calf blood group. The majority of corneal subbasal nerve fiber regeneration occurred from the stump of corneal subbasal nerve fibers outside the corneal flap and the remaining growth occurred deep within the stroma.展开更多
With the vigorous development of China's transportation industry,the mileage of high-grade highways based on semi rigid base layers has been increasing year by year.However,the commonly used material for semi rigi...With the vigorous development of China's transportation industry,the mileage of high-grade highways based on semi rigid base layers has been increasing year by year.However,the commonly used material for semi rigid base layers,cement stabilized crushed stone mixture(hereinafter referred to as water stabilized mixture),often experiences segregation during mixing,transportation,and paving.Separation of water stabilized mixture can greatly reduce the service life of roads and cause damage to people's property,the traditional separation detection method that relies on manual experience has problems of low detection efficiency and low recognition accuracy.In order to solve these problems and assist in the modernization of road construction,this article proposes a separation recognition method for water stabilized mixtures based on deep learning.Firstly,a database of segregation diseases of water stabilized mixture was built.Secondly,the control tests were set up by standard fine-tuning and feature extraction,and four different optimizers were set up respectively.By comparing accuracy,loss,precision,recall and F1-score at the end of the pre-trained network,the overall recognition effect of ResNet-101 as the network model was better.Thirdly,the ResNet-101 model was optimized by SpotTune,replacing cross entropy loss with focus loss,adding PReLU to the pre-trained network and a BN layer to the top layer of the pre-trained network,and using 1×1.Convolutional replacement of the fully connected layer.Finally,build a web side water stabilized mixture segregation recognition platform,and its stability was verified in practical engineering.展开更多
对比3种橡胶改性方式下的橡胶水稳碎石混合料,通过电镜扫描(scanning electron microscope,SEM)与能谱分析(energy dispersive spectrometry,EDS)选取最优的改性方法,对橡胶改性处理之后的水稳碎石混合料进行力学性能与收缩性能试验。...对比3种橡胶改性方式下的橡胶水稳碎石混合料,通过电镜扫描(scanning electron microscope,SEM)与能谱分析(energy dispersive spectrometry,EDS)选取最优的改性方法,对橡胶改性处理之后的水稳碎石混合料进行力学性能与收缩性能试验。结果表明:经NaOH与硅烷偶联剂KH-570复合改性处理之后的橡胶水稳碎石混合料,其橡胶-水泥基体界面过渡区的平均裂缝宽度最小,水化硅酸钙凝胶生成比例最大,界面过渡区结构最为紧密。在水稳碎石混合料中掺入复合改性处理后的橡胶,能够大大减少因掺入橡胶颗粒对混合料带来的强度损失,材料的抗收缩性能也未因橡胶颗粒的改性处理而减弱。展开更多
基金Project(2024JJ2073)supported by the Science Fund for Distinguished Young Scholars of Hunan Province,ChinaProjects(2023YFC3807205,2019YFC1904704)+4 种基金supported by the National Key R&D Program of ChinaProject(52178443)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0109)supported by Fundamental Research Funds for the Central Universities of Central South University,China。
文摘Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.
基金Funded by the National Natural Science Foundation of China (No.52078068)the Natural Science Foundation of Jiangsu Province (No.BK20220626)。
文摘This study meticulously examined the compaction and sulfate erosion resistance of cement-stabilized materials incorporating recycled brick-concrete aggregate (RBCA).To explore the effects of recycled brick aggregate (RBA) with varying particle sizes,three size ranges (4.75-9.5 mm,9.5-19 mm and 19-31.5 mm) were used to replace 20% of the corresponding particle sizes of recycled concrete aggregate (RCA) in cement-stabilized materials.The findings indicated that cement-stabilized materials utilizing RBA and RCA exhibited a lower maximum dry density and a higher optimum moisture content than natural aggregate cement-stabilized materials.The use of RBA with a particle size of 4.75-9.5 mm resulted in a lower maximum dry density and a higher optimum moisture content than 9.5-19 mm and 19-31.5 mm.Furthermore,the 7-day unconfined compressive strength of RBCA cement-stabilized materials with RBA of 4.75-9.5 mm demonstrated superior results compared to those with larger particle sizes.Regarding sulfate erosion resistance,the mass loss and unconfined compressive strength loss of the RBCA cement-stabilized materials at 56 days were highest for the 19-31.5 mm particle size of the RBA.In terms of compaction and sulfate resistance,it is recommended to use 4.75-19 mm RBA in RBCA cement-stabilized materials.
文摘The cement dry jet mixing method has been used to reinforce soft cohesive ground to increase the strength of soft cohesive ground and to decrease its deformation. The study briefly introduces the curing mechanism of cement-soil,presents the factors of influencing on compressive strength,mainly analyses the factors including cement mixing ratio,cement strength grade,curing age,moisture content and soil texture and puts forward some rational proposals at last.
基金sponsored by the projects found by the National Natural Science Foundation of China(NSFC)under Grant No.51978163 and Grant No.52208439the Natural Science Foundation of Jiangsu Province under Grant No.BK20200468+4 种基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province under Grant No.SJCX22_0063the Jiangsu Transportation Science and Technology and Achievement Transformation Project under Grant No.2020Y19-1(1)Key S&T Project of Ministry of Transport of the People's Republic of China(2021-ZD1-004)the Scientific Research Program Project of Shanghai Municipal Transportation Commission(JT2021-KY-016)which the authors are very grateful.
文摘The base layer constructed by cement-stabilized macadam(CSM)has been widely used in highway construction due to its low elasticity deformation and high carrying capacity.As a bearing layer,the CSM base is not exempt from fatigue cracking under cyclic loading in the service process.Cracks in the base will create irreversible structural and functional deficiencies,such as the potential for reflective cracking of subsequently placed asphalt concrete overlays.The fracture of the base will shorten the service life of the pavement.The quality of the CSM base is directly related to the bearing capacity and integrity of the whole pavement structure.It is of practical significance to further study the fatigue failure behavior of CSM material for the long-term performance of the pavement.The CSM material is a typical heterogeneous multiphase composite.On the mesoscale,CSM consists of aggregate,cement mortar,pores,and the interface transitional zone(ITZ).On the microscale,the hardened mortar contains a large number of capillary pores,unhydrated particles,hydrated crystals,etc.,which makes the spatial distribution of its material properties stochastic.In addition,cement hydration,dry shrinkage,and temperature shrinkage can also produce micro-crack defects in cement mortar.These microcracks will have crossscale evolution under load,resulting in structural fracture.Macroscopic complex deformation and mechanical response are the reflections of its microscopic and even mesoscale composition and structure.This study summarized the existing studies on the mesoscopic properties of CSM materials,respectively from the three aspects of mesostructure,structural characterization,and mesoscale fatigue damage analysis,to help the development of long-life pavement.The future research direction is to explore the mesoscale characteristics of CSM using multiscale representation and analysis methods,to establish the connection between mesoscale characteristics and macroscopic mechanical properties.
基金supported by funding from the National Natural Science Foundation of China (Grant Nos.51978303 and 52208367)the Fundamental Research Funds for the Central Universities (Grant No.2042023kfyq03).
文摘The influence of curing temperature on the strength development of cement-stabilized mud has been well documented in terms of strength-increase rate and ultimate strength.However,the strength development model is not mature for the extremely early stages.In addition,there is a lack of studies on quality control methods based on early-stage strength development.This paper presents a strength model for cement-stabilized mud to address these gaps,considering various curing temperatures and early-stage behaviors.In this study,a series of laboratory experiments was conducted on two types of muds treated with Portland blast furnace cement and ordinary Portland cement under four different temperatures.The results indicate that elevated temperatures expedite strength development and lead to higher long-term strength.The proposed model,which combines a three-step conversion process and a hyperbolic model at the reference temperature,enables accurate estimate of the strength development for cement-treated mud with any proportions cured under various temperatures.With this model,a practical early quality control method is introduced for applying cement-stabilized mud in field projects.The back-analysis parameters obtained from a 36-h investigation at temperature of 60C demonstrated a sufficient accuracy in predicting strength levels in practical applications.
基金sponsored by National Natural Science Foundation of China(No.52308466)SASAC Science and Technology Innovation Project(JF-23-01-0063)Shaanxi Provincial Transportation Research Project(25-84 K,25-85 K).
文摘In recent years,the amount of waste generated during milling has increased dramatically,and improper disposal poses a significant environmental challenge.To mitigate environmental pollution and enhance the road performance of emulsified asphalt cold recycled mixtures(ECRM),this study employed recycled asphalt pavement(RAP)and reclaimed inorganic binder stabilized aggregate(RAI)as dual recycled materials for ECRM preparation.The blending ratios of reclaimed base and surface layer mixtures significantly influence ECRM's performance,with adjusted proportions substantially improving compressive strength and dynamic modulus.Firstly,three distinct proportioning options were developed for the recycled materials.Mix designs incorporating varying RAP/RAI ratios were used to determine the optimal mix parameters:moisture content,cement dosage,and emulsified asphalt content.Subsequently,comprehensive performance evaluations were conducted through high-temperature wheel tracking tests,freeze-thaw splitting tests,uniaxial compression tests,and dynamic modulus measurements to analyze the pavement characteristics of the three ECRM formulations.Experimental results demonstrate:Compared with ECRM with a blending ratio of RAP:RAI:new aggregate=30:50:20(Option 1),the dynamic stability,freeze-thaw splitting strength ratio,compressive strength,and compressive resilient modulus of ECRM under Option 3(RAP:RAI:new aggregate=50:30:20)decreased by 31.8%,5.2%,16.4%,and 13.1%,respectively.This indicates that increasing RAP content while reducing RAI proportion enhances the tensile strength of ECRM,yet adversely affects its high-temperature stability,moisture resistance,and compressive performance.This work not only addresses the challenge of jointly utilizing asphalt pavement waste and base waste,but also provides a cost-effective and sustainable method for the stable application of milling material resources in road engineering.
文摘A total of 26 myopic patients （52 eyes） underwent laser in situ keratomileusis. In vivo confocal microscopy revealed that most of the regenerated corneal subbasal nerve fibers in the comeal flap originated from the stump of corneal subbasal nerve fibers outside the ablation zone and extended towards the center of the cornea in all patients. Meanwhile, new fibers were also found to directly regenerate from deep in the stroma in some cases. Approximately 94% of regenerated corneal subbasal nerve fibers （73/78 eyes） regrew vertically into the peripheral central 6-mm circle area 1 month after surgery, 78% （28/36 eyes） grew into the central 3 6 mm area at 2 months, and 23% into the central 3-mm circle area at 3 months. In addition, there was no significant difference in corneal subbasal nerve fiber regenerative capacity between the basic fibroblast growth factor group and the 20% （vN） deproteinized extract of calf blood group. The majority of corneal subbasal nerve fiber regeneration occurred from the stump of corneal subbasal nerve fibers outside the corneal flap and the remaining growth occurred deep within the stroma.
基金sponsored by the National Natural Science Foundation of China under grant No.52008154,to which the authors are very grateful.
文摘With the vigorous development of China's transportation industry,the mileage of high-grade highways based on semi rigid base layers has been increasing year by year.However,the commonly used material for semi rigid base layers,cement stabilized crushed stone mixture(hereinafter referred to as water stabilized mixture),often experiences segregation during mixing,transportation,and paving.Separation of water stabilized mixture can greatly reduce the service life of roads and cause damage to people's property,the traditional separation detection method that relies on manual experience has problems of low detection efficiency and low recognition accuracy.In order to solve these problems and assist in the modernization of road construction,this article proposes a separation recognition method for water stabilized mixtures based on deep learning.Firstly,a database of segregation diseases of water stabilized mixture was built.Secondly,the control tests were set up by standard fine-tuning and feature extraction,and four different optimizers were set up respectively.By comparing accuracy,loss,precision,recall and F1-score at the end of the pre-trained network,the overall recognition effect of ResNet-101 as the network model was better.Thirdly,the ResNet-101 model was optimized by SpotTune,replacing cross entropy loss with focus loss,adding PReLU to the pre-trained network and a BN layer to the top layer of the pre-trained network,and using 1×1.Convolutional replacement of the fully connected layer.Finally,build a web side water stabilized mixture segregation recognition platform,and its stability was verified in practical engineering.
文摘对比3种橡胶改性方式下的橡胶水稳碎石混合料,通过电镜扫描(scanning electron microscope,SEM)与能谱分析(energy dispersive spectrometry,EDS)选取最优的改性方法,对橡胶改性处理之后的水稳碎石混合料进行力学性能与收缩性能试验。结果表明:经NaOH与硅烷偶联剂KH-570复合改性处理之后的橡胶水稳碎石混合料,其橡胶-水泥基体界面过渡区的平均裂缝宽度最小,水化硅酸钙凝胶生成比例最大,界面过渡区结构最为紧密。在水稳碎石混合料中掺入复合改性处理后的橡胶,能够大大减少因掺入橡胶颗粒对混合料带来的强度损失,材料的抗收缩性能也未因橡胶颗粒的改性处理而减弱。
