The replacement ratio is an essential factor in evaluating the bearing capacity characteristics of compositefoundations. This study focuses on the bearing capacity of a pervious concrete pile with different replacemen...The replacement ratio is an essential factor in evaluating the bearing capacity characteristics of compositefoundations. This study focuses on the bearing capacity of a pervious concrete pile with different replacementratios. The axial force, skin friction, and settlement were evaluated using a model test to assess the performance ofthe pervious concrete pile composite foundation. When the replacement ratio was reduced from 9.26% to 2.32%,the characteristic bearing capacity value was only 14%. Therefore, it may be unreasonable to use the settlementratio method to evaluate this composite foundation's bearing capacity in a model test. Appropriate loading cansignificantly improve the bearing capacity of a pervious concrete pile composite foundation with a lowreplacement ratio. The pile–soil stress ratio exhibited different decreasing ranges in the later loading stage. As theload increased, the axial force of the pervious concrete piles was small and nonobvious, and the average sidefriction resistance of the piles in the foundation with a lower replacement ratio slowly increased.展开更多
To investigate the effect of recycled sand on the compressive properties of recycled coarse aggregate concrete with different strength grades,an experimental study on the stress-strain curve under uniaxial compression...To investigate the effect of recycled sand on the compressive properties of recycled coarse aggregate concrete with different strength grades,an experimental study on the stress-strain curve under uniaxial compression was conducted.The failure processes and modes of recycled sand concrete(RSC)were studied,and the peak stress,peak strain,elastic modulus,ultimate strain,and toughness of RSC with different strength grades were studied.The interfacial transition zone(ITZ)of RSC was studied using microhardness and SEM,and its failure mechanism was studied.The results indicate that the addition of recycled sand has a significant impact on the descending segment of the stress-strain curve for the same strength grade.Based on Chinese standards,the relationship between the parameters of the descending segment and the peak stress of RSC was determined.A constitutive relationship for the stress-strain behavior of RSC under uniaxial compression was proposed.The microhardness of the ITZ increases with the decrease in the water-binder ratio and first increases and then decreases with the replacement ratio.This is due to the gelation activity of recycled powder,which reacts with hydration products to fill pores.However,when the content of recycled powder is excessive,the alkaline environment that maintains the stability of the C-S-H gel is disrupted,leading to a decrease in microhardness.展开更多
The emission of greenhouse gases from cement production is an obstacle for sustainable development of construction industry.The use of waste materials in constructions instead of cement could be a feasible solution to...The emission of greenhouse gases from cement production is an obstacle for sustainable development of construction industry.The use of waste materials in constructions instead of cement could be a feasible solution to green construction.Waste marble powder with good cementing property can be used in concrete partially replace cement.In this research,the effects of using waste marble powder on the physical and mechanical properties of concrete have been studied.Three groups of particle size and five levels of replacement ratio(5%,10%,15%,20%,25%)for each group have been designed.During the different stage of hydration process,the microstructure,phase composition and thermal properties of marble-cement paste have been investigated,the influence of particle size of marble powder on these properties has been discussed.The compressive strength and stressstrain relation were tested for different series prepared by partially replacing cement at proportions of 5%–25%separately.From the data analysis,it was observed that the using of waste marble powder would affect the hydration products and further affect the mechanical properties of concrete,the addition of marble powder that partially replace the cement at particular proportions in concrete is feasible.展开更多
This paper experimentally investigated the flexural behavior of reinforced recycled aggregate concrete(RAC)beams reinforced with glass fiber-reinforced polymer(GFRP)bars.A total of twelve beams were built and tested u...This paper experimentally investigated the flexural behavior of reinforced recycled aggregate concrete(RAC)beams reinforced with glass fiber-reinforced polymer(GFRP)bars.A total of twelve beams were built and tested up to failure under four-point bending.The main parameters were reinforcement ratio(0.38%,0.60%,and 1.17%),recycled aggregate replacement ratio(R=0,50%,and 100%)and longitudinal reinforcement types(GFRP and steel).The flexural capacity,failure modes,flexibility deformation,reinforcement strains and crack distribution of the tested beams were investigated and compared with the calculation models of American code ACI 440.1-R-15,Canadian code CSA S806-12 and ISIS-M03-07.The tested results indicated that the reinforcement ratio has great influence on the ultimate load,crack width and deflection of GFRP-RAC beams,the recycled aggregate replacement ratio has little influence on it.However,it was found that the reinforcement ratio has no obvious influence on the cracking load which was only related to the recycled aggregate replacement ratio.The average cracking load decreased by 5%and 15%as the recycled aggregate replacement ratio increased from 0 to 50%and 100%.For the steel-RAC beams,the ultimate load was found to be about 1/2 of the ultimate load of GFRP-RAC beam under the same condition and the trend of strain,deflection and crack width were different from GFRP-RAC beams.This is due to the different material properties of GFRP bars and steel rebar.On the other hand,the calculation results showed that ACI 440.1-R-15 and CSA S806-12 underestimated the ultimate load of GFRP-RAC beams.Moreover,the deflection prediction of GFRP-RAC beams by CSA S806-12 is relatively accurate compared with ACI 440.1-R-15 and ISIS-M03-07.As for the prediction of crack width,the results of ACI 440.1-R-15 prediction were in good agreement with the experimental results at the ultimate load,with the average value of 1.09±0.28.展开更多
As a typical compression member,the concrete-filled steel tube has been widely used in civil engineering structures.However,little research on recycled self-compacting concrete flled circular steel tubular(RSCCFCST)co...As a typical compression member,the concrete-filled steel tube has been widely used in civil engineering structures.However,little research on recycled self-compacting concrete flled circular steel tubular(RSCCFCST)columns subjected to eccentric load was reported.In this study,21 specimens were designed and experimental studies on the stress-strain relationship of were carried out to study the mechanical behaviors.Recycled coarse aggregate replacement ratio,concrete strength grade,length to diameter ratio and eccentric distance of specimens were considered as the main experimental parameters to carry out eccentric compression tests.The corresponding stress-strain relationship curves were used to analyze the influence of concerned parameters on ecentric load-bearing capacity of RSCCFCST columns.The experimental results show that the strain of the eccentric compression stress-strain curves increase with the increase of recycled coarse aggregate replacement ratio and concrete strength grade.With increase of eccentric distance,the ductility of specimens increases while the bearing capacity decreases.Moreover,a phenomenological model of RSCCFCST columns is proposed,which exhibits versatile ability to capture the process during loading.The present study is expected to further understanding the behaviors and to provide guidance of RSCCFCST columns in design and engineering applications.展开更多
基金the support from the National Natural Science Foundation of China(Grant No.41977241).
文摘The replacement ratio is an essential factor in evaluating the bearing capacity characteristics of compositefoundations. This study focuses on the bearing capacity of a pervious concrete pile with different replacementratios. The axial force, skin friction, and settlement were evaluated using a model test to assess the performance ofthe pervious concrete pile composite foundation. When the replacement ratio was reduced from 9.26% to 2.32%,the characteristic bearing capacity value was only 14%. Therefore, it may be unreasonable to use the settlementratio method to evaluate this composite foundation's bearing capacity in a model test. Appropriate loading cansignificantly improve the bearing capacity of a pervious concrete pile composite foundation with a lowreplacement ratio. The pile–soil stress ratio exhibited different decreasing ranges in the later loading stage. As theload increased, the axial force of the pervious concrete piles was small and nonobvious, and the average sidefriction resistance of the piles in the foundation with a lower replacement ratio slowly increased.
基金Funded by National Key Research and Development Program of China(No.2020YFC1909905)Science and Technology Research and Development Plan of China National Railway Group Co.+2 种基金Ltd.(No.L2022G009)National Natural Science Foundation of China High-speed Rail Joint Fund(No.U1934206)New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘To investigate the effect of recycled sand on the compressive properties of recycled coarse aggregate concrete with different strength grades,an experimental study on the stress-strain curve under uniaxial compression was conducted.The failure processes and modes of recycled sand concrete(RSC)were studied,and the peak stress,peak strain,elastic modulus,ultimate strain,and toughness of RSC with different strength grades were studied.The interfacial transition zone(ITZ)of RSC was studied using microhardness and SEM,and its failure mechanism was studied.The results indicate that the addition of recycled sand has a significant impact on the descending segment of the stress-strain curve for the same strength grade.Based on Chinese standards,the relationship between the parameters of the descending segment and the peak stress of RSC was determined.A constitutive relationship for the stress-strain behavior of RSC under uniaxial compression was proposed.The microhardness of the ITZ increases with the decrease in the water-binder ratio and first increases and then decreases with the replacement ratio.This is due to the gelation activity of recycled powder,which reacts with hydration products to fill pores.However,when the content of recycled powder is excessive,the alkaline environment that maintains the stability of the C-S-H gel is disrupted,leading to a decrease in microhardness.
基金National Natural Science Foundation of China(Grant No.51661145023)Systematic Project of Guangxi Key Laboratory of Disaster Prevention and Structural Safety(Grant No.2019ZDX003).
文摘The emission of greenhouse gases from cement production is an obstacle for sustainable development of construction industry.The use of waste materials in constructions instead of cement could be a feasible solution to green construction.Waste marble powder with good cementing property can be used in concrete partially replace cement.In this research,the effects of using waste marble powder on the physical and mechanical properties of concrete have been studied.Three groups of particle size and five levels of replacement ratio(5%,10%,15%,20%,25%)for each group have been designed.During the different stage of hydration process,the microstructure,phase composition and thermal properties of marble-cement paste have been investigated,the influence of particle size of marble powder on these properties has been discussed.The compressive strength and stressstrain relation were tested for different series prepared by partially replacing cement at proportions of 5%–25%separately.From the data analysis,it was observed that the using of waste marble powder would affect the hydration products and further affect the mechanical properties of concrete,the addition of marble powder that partially replace the cement at particular proportions in concrete is feasible.
基金The authors gratefully acknowledge the support of the National Natural Science Foundation of China(51704029)Liaoning Revitalization Talents Program(XLYC1807044,XLYC1807050).
文摘This paper experimentally investigated the flexural behavior of reinforced recycled aggregate concrete(RAC)beams reinforced with glass fiber-reinforced polymer(GFRP)bars.A total of twelve beams were built and tested up to failure under four-point bending.The main parameters were reinforcement ratio(0.38%,0.60%,and 1.17%),recycled aggregate replacement ratio(R=0,50%,and 100%)and longitudinal reinforcement types(GFRP and steel).The flexural capacity,failure modes,flexibility deformation,reinforcement strains and crack distribution of the tested beams were investigated and compared with the calculation models of American code ACI 440.1-R-15,Canadian code CSA S806-12 and ISIS-M03-07.The tested results indicated that the reinforcement ratio has great influence on the ultimate load,crack width and deflection of GFRP-RAC beams,the recycled aggregate replacement ratio has little influence on it.However,it was found that the reinforcement ratio has no obvious influence on the cracking load which was only related to the recycled aggregate replacement ratio.The average cracking load decreased by 5%and 15%as the recycled aggregate replacement ratio increased from 0 to 50%and 100%.For the steel-RAC beams,the ultimate load was found to be about 1/2 of the ultimate load of GFRP-RAC beam under the same condition and the trend of strain,deflection and crack width were different from GFRP-RAC beams.This is due to the different material properties of GFRP bars and steel rebar.On the other hand,the calculation results showed that ACI 440.1-R-15 and CSA S806-12 underestimated the ultimate load of GFRP-RAC beams.Moreover,the deflection prediction of GFRP-RAC beams by CSA S806-12 is relatively accurate compared with ACI 440.1-R-15 and ISIS-M03-07.As for the prediction of crack width,the results of ACI 440.1-R-15 prediction were in good agreement with the experimental results at the ultimate load,with the average value of 1.09±0.28.
基金Supported by the National Natural Science Foundation of China(Grant Nos.51578001,51608003,and 51878002)Natural Science Foundation granted by Department of Education,Anhui Province(No.KJ2015ZD10)+2 种基金Key Research and Development Plan of Anhui Province(No.1704a0802131)the Outstanding Young Talent Support Program of Anhui Province(No.gxyqZD2016072)This work was also supported by the Graduate Innovation Research Foundation granted by Anhui University of Technology(Nos.2016097,2016094).
文摘As a typical compression member,the concrete-filled steel tube has been widely used in civil engineering structures.However,little research on recycled self-compacting concrete flled circular steel tubular(RSCCFCST)columns subjected to eccentric load was reported.In this study,21 specimens were designed and experimental studies on the stress-strain relationship of were carried out to study the mechanical behaviors.Recycled coarse aggregate replacement ratio,concrete strength grade,length to diameter ratio and eccentric distance of specimens were considered as the main experimental parameters to carry out eccentric compression tests.The corresponding stress-strain relationship curves were used to analyze the influence of concerned parameters on ecentric load-bearing capacity of RSCCFCST columns.The experimental results show that the strain of the eccentric compression stress-strain curves increase with the increase of recycled coarse aggregate replacement ratio and concrete strength grade.With increase of eccentric distance,the ductility of specimens increases while the bearing capacity decreases.Moreover,a phenomenological model of RSCCFCST columns is proposed,which exhibits versatile ability to capture the process during loading.The present study is expected to further understanding the behaviors and to provide guidance of RSCCFCST columns in design and engineering applications.
