To investigate the assumptions proposed in this paper,the evolution law governing the strength and expansion performance of MgO and nano-MgO micro-expansive concrete in the environment of mineral powder was firstly ob...To investigate the assumptions proposed in this paper,the evolution law governing the strength and expansion performance of MgO and nano-MgO micro-expansive concrete in the environment of mineral powder was firstly observed in this study.Secondly,SEM,XRD,and TG-DSC microscopic tests were conducted to reveal the effects of the active mineral-powder admixture on the hydration degree and expansion performance of MgO and nano-MgO in HPC.Our experimental results successfully verified our hypothesis,which indicated that the expansion performance of macro-MgO and nano-MgO was indeed depressed by the addition of active mineral power admixtures,even though the mechanical property of concrete composites was effectively improved.Furthermore,the hydration test also demonstrated the negative interference on the mineral powders,which was induced by the expansion agents.It is found the amounts of hydrates tend to decrease because the mineral powder ratio reaches and exceeds 40%.Moreover,it is also concluded the effect of expansion agents is governed by the alkalinity cement paste,especially for the nano-MgO.In other words,the expansion performance of nano-MgO will vary more obviously with the hydration process,than MgO.The results of this study provide that effective experimental and theoretical data support the hydration-inhibition mechanism of magnesium expansive agents.展开更多
Generally,the so-called expansion agent is very effective in eliminating all the micro-annuli that exist between the casing and the cement sheath or between the cement sheath and the formation.However,this approach ca...Generally,the so-called expansion agent is very effective in eliminating all the micro-annuli that exist between the casing and the cement sheath or between the cement sheath and the formation.However,this approach can detrimentally affect the sealing ability of cement sheath if the expansion agent is used in an unreasonable way.For these reasons,in the present work,numerical simulations have been conducted to analyze the effect of elasticity modulus of cement sheath,the elasticity modulus of formation,the expansion rate of cement,the geo-stress on the micro-annulus caused by cement expansion,and the cement sheath expansion on the integrity of cement sheath and formation.The micro-annulus between the casing and the cement sheath has been found to decrease according to the ratio between the elasticity modulus of formation and the elasticity modulus of cement sheath.A positive correlation has been observed between the micro-annulus and the cement expansion ratio.The microannulus decreases as the geo-stress increases,but the effect of the geo-stress on the micro-annulus is much smaller.In conclusion,the expansion agent is suitable for the formation in which the elasticity modulus is higher than the cement sheath.展开更多
A new type of concrete expansion agent has been successfully developed for the first time in the world by utilizing an industrial waste residue soda residue and an industrial wasteliquor.Adding 3%-6% of the agent int...A new type of concrete expansion agent has been successfully developed for the first time in the world by utilizing an industrial waste residue soda residue and an industrial wasteliquor.Adding 3%-6% of the agent into Portland cement enables a shrinkage compensating concrete to be prepared.Mortar and concrete containing this expansion agent have better shrinkage compensating and mechanical properties.The raw materials component,production process,technical properties,micro analysis of mortar made with this expansion agent,mechanism of expansion and research results are described in this article.The experimental results show that the new type of concrete expansion agent accords with the standard and its main mineral component is xCaO ySO 3 zAl 2O 3.展开更多
Rolled static cracking agent(RSCA)can solve the intractable problem of traditional bulk static cracking agent(BSCA)in engineering applications.This paper innovatively studies the rational water-cement ratio of BSCA an...Rolled static cracking agent(RSCA)can solve the intractable problem of traditional bulk static cracking agent(BSCA)in engineering applications.This paper innovatively studies the rational water-cement ratio of BSCA and the immersion soaking time of RSCA under the condition of controlling temperature.Through the expansion and cracking performance experiments,the development characteristics of expansion pressure,the cracking effect of the single-hole specimen and the performance of hole spraying prevention under the action of BSCA and RSCA were compared and analyzed.The results show that:(1)The volume growth rate of static cracking agent decreases with the increase of water-cement ratio,and the fluidity increases with the increase of water-cement ratio.The rational water-cement ratio for BSCA application is 0.3,and the rational immersion time of RSCA is 2-2.5 min;(2)Under the bore diameters of 30,35,40 and 45 mm,the expansion pressure of BSCA with a water-cement ratio of 0.3 is 38.2,52.3,61.5 and 68 MPa,and the expansion pressure of RSCA immersed in water for 2.5 min is 43.5,58.8,69.5 and 75.1 MPa,respectively.Among them,the development speed of expansion pressure of BSCA is higher than that of RSCA,and the arrival time of the peak expansion pressure of RSCA is 1.7 times that of BSCA;(3)The crack initiation speed of single-hole specimen under the action of RSCA is 10.3%lower than that under the action of BSCA,but the cracking speed of the former is 72.6%higher than that of the latter;(4)The hole spraying occurs in BSCA under the bore diameter of 50,55 and 60 mm,while the hole spraying occurs in RSCA under the bore diameter of 60 mm.In terms of bore diameter,the hole spraying prevention of the RSCA is better than that of BSCA.The research results enrich the static blasting technology and provide data support and theoretical reference for field application.展开更多
It is crucial to investigate the urban agglomerations spatio-temporal evolution patterns and driving factors for analyzing the urban spatial structure-functional division and promoting the coordinated development of u...It is crucial to investigate the urban agglomerations spatio-temporal evolution patterns and driving factors for analyzing the urban spatial structure-functional division and promoting the coordinated development of urban agglomerations.In this study,a novel vegetation-building-nighttime light-adjusted index(VBNAI)was established for rapid and effective mapping of urban construction land(UCL)in Central Plains Urban Agglomeration(CPUA),China during 2000–2020 based on Google Earth Engine(GEE)platform.Compared with traditional indices,VBNAI can significantly decrease the blooming effect,Normalized Difference Vegetation Index(NDVI)saturation,and soil background of nighttime light data.In addition,the urban expansion indices and standard deviation ellipse model were synthetically adopted to analyze the spatio-temporal evolution pattern of urban expansion.The gravity model and the geographically weighted regression model were employed to determine the spatial interaction forces and drivers of urban expansion,respectively.The results showed that the VBNAI index has obvious advantages in efficiency and accuracy to extract UCL with the overall accuracy of more than 91%.The UCL of CPUA had increased by 4489.84 km2 during 2000–2020 with the gravity center moving towards southeast continuously.From 2000 to 2010,the urban expansion was in a‘center-hinterland’pattern which had benefit from the favorable effect of the traffic shaft belt.During 2010–2020,the urban network structure had basically established.Urban expansion had been influenced by a variety of socio-economic and demographic factors,and the impact degree varied from region to region.This study could provide scientific references for facilitating the intensive utilization of urban resources and optimizing the spatial development pattern of urban agglomeration.展开更多
Although traditional urban expansion simulation models can simulate dynamic features, these models fail to address complex changes produced by different agents' behaviors. The paper has built up a set of spatial-temp...Although traditional urban expansion simulation models can simulate dynamic features, these models fail to address complex changes produced by different agents' behaviors. The paper has built up a set of spatial-temporal land resource allocation rules and developed a dynamic urban expansion model based on a multi-agent system, which can simulate the interaction among different agents, such as residents, peasants, and governments. This model is applied to simulate urban expansion process taking Changsha City, in China as a study area. The results show that this model can not only reflect basic characteristics of urban expansion, but also help explain the reasons for urban expansion process and understand the effect of agents' behavior on the expansion process, and provide insights into the causing factors behind the expansion. In addition, in contrast to simulation results with land use classification map from remote sensing images, the precision of the simulation reached over 68% with higher precision than cellular automata model according to the cell-by-cell comparison. The results suggest that the model can help to provide land use decision making support to government and urban planners.展开更多
In this study,three-phase satellite images were used to define rules for the allocation of time and space in construction land resources based on a complex adaptive system and game theory.The decision behavior and rul...In this study,three-phase satellite images were used to define rules for the allocation of time and space in construction land resources based on a complex adaptive system and game theory.The decision behavior and rules of government agent,enterprise agent and resident agent in construction land growth were explored.A distinctive and dynamic simulation model of construction land growth was built,which integrated multi-agent,GIS technology and RS data and described the interaction among influencing agents.Taking Fuyang City in the Changjiang River Delta as an example,an assessment process for the remote sensing data in construction land and scenario planning was constructed.Repast and ArcGIS were used as simulation platforms.A simulation of the spatial pattern in land-use planning and the setting of scenario planning were conducted by using the incomplete active game,which was based on different natural,social and economic levels.Through this model,a simulation of urban planning space and decision-making for Fuyang City was created.Relevant non-structured problems arising from urban planning management could be identified,and the process and logic of urban planning spatial decision-making could thus be improved.Cel1-by-cel1 comparison showed that the simulation accuracy was over 72%.This model has great potential for use by government and town planners in decision support and technique support in the policy-making process.展开更多
The effects of fly ash and MgO-type expansive agent on the shrinkage and expan-sive strain of concrete with high magnesia cement were investigated. The results show that high volumes of fly ash may reduce the shrinkag...The effects of fly ash and MgO-type expansive agent on the shrinkage and expan-sive strain of concrete with high magnesia cement were investigated. The results show that high volumes of fly ash may reduce the shrinkage strain of concrete and inhibit the expansive strain of concrete with MgO-type expansive agent, but can not eliminate the shrinkage of concrete. MgO-type expansive agent may produce expansive strain and compensate the shrinkage strain of concrete, re-lieve the cracking risk, but the hydration product of magnesia tends to get together in paste and pro-duce expansive cracking of concrete with high magnesia content according to SEM observation.展开更多
The hydration behaviors and expansive properties of MgO-type expansive agent curing at different temperatures and environment were investigated.When the curing temperatures changed from 25℃ to 50℃,the conductivities...The hydration behaviors and expansive properties of MgO-type expansive agent curing at different temperatures and environment were investigated.When the curing temperatures changed from 25℃ to 50℃,the conductivities of MgO samples increased from 40 to 80 μs/cm,and the hydrations of MgO were quickened up obviously.Through SEM observation,the hydration product of MgO cured at 50℃ for 28 day was about 2-3μm in length.The expansion of pastes with 5% of the MgO-type expansive agent was from 0.36% to 1.01% when the curing temperature changed from 25oC to 50℃.When 8% of the MgO-type expansive agent was added,the early shrinkage of concrete was reduced.The expansion ratio increased with the curing temperature,and the expansive cracking of concrete with MgO-type expansive agent might be decreased by blending fly ash.展开更多
The effect of combination of steel fiber and MgO-type expansive agent (MEA) on strength, air-permeability and porosity of concrete was investigated. The porosity and air-permeability of concrete were determined by m...The effect of combination of steel fiber and MgO-type expansive agent (MEA) on strength, air-permeability and porosity of concrete was investigated. The porosity and air-permeability of concrete were determined by method of evaporated water and Torrent permeability tester, respectively. Pore structures of mortars in concrete were analyzed using mercury intrusion porosimetry (MIP). Interfacial structures between steel fibers and matrix were examined by use of optical microscope. The experimental results show that improvement of pore structures of mortar and fiber-matrix interfacial structure in concrete by combination of steel fiber and MEA may remarkably increase properties of concrete. In comparison with plain concrete, compressive strength and splitting tensile strength of steel fiber reinforced expansive concrete increased by 15.3% and 38.1%, permeability coefficient Kt, penetration depth L and porosity of concrete decreased by 41.1%, 21.3% and 13.1% at 28 days, respectively.展开更多
The self-stress trial of the fifteen high-strength, low-heat andmicro-expansion concrete-filled steel tube(CFST)is introduced, andthe generating and distributing features of pre-stress and itsrelation to add- ing quan...The self-stress trial of the fifteen high-strength, low-heat andmicro-expansion concrete-filled steel tube(CFST)is introduced, andthe generating and distributing features of pre-stress and itsrelation to add- ing quantity of expansive agent, which providespersuasive dependences for optimal design of high-strength, low- heatand micro-expansion CFST were investigated, especially for the designof added quantity of expansive agent.展开更多
By employing different forms and amounts of materials, many kinds of ettringite type expansive agents had been prepared. The relationship between the compositions and properties of expansive agents was analyzed. The d...By employing different forms and amounts of materials, many kinds of ettringite type expansive agents had been prepared. The relationship between the compositions and properties of expansive agents was analyzed. The design methods of expansive agent have been put forward according to the property, requirement of expansive concrete.展开更多
The mechanisms and processes of sulfate attack on roller compacted concrete(RCC)with MgO expansive agent are proposed by investigating the microstructure and hydration products in specimens immersed in 5%sodium sulfat...The mechanisms and processes of sulfate attack on roller compacted concrete(RCC)with MgO expansive agent are proposed by investigating the microstructure and hydration products in specimens immersed in 5%sodium sulfate solution for one year with the optical micrograph,scanning electron microscopy(SEM)and scanning electron microscopy-energy dispersive spectrometer(SEM-EDS).The results show that the deterioration of concrete due to the sulfate attack is mainly loss of stiffness,strength and adhesion,and expansion cracking is mainly caused by the formation of gypsum and ettringite.In the presence of MgO expansive agent,the microstructures of RCC can be improved by hydration and un-hydrated products,the large pores and permeability are reduced,and the resistance to sulfate corrosion of concrete and durability of hydraulic structure are improved slightly.展开更多
Static cracking agent(SCA)is actively investigated as an alternative to explosive blasting for rock breakage due to its immense expansion property.SCA can eliminate the negative effects of shock,noise and harmful gase...Static cracking agent(SCA)is actively investigated as an alternative to explosive blasting for rock breakage due to its immense expansion property.SCA can eliminate the negative effects of shock,noise and harmful gases encountered in explosive blasting processes.Accurate measurement and deep understanding of the expansive properties of SCAs are important in their industrial application.An improved outer pipe method(OPM),termed the upper end surface method(UESM),is proposed in this paper to overcome the shortcomings of the OPM in the expansive pressure measurement of SCAs.Numerical simulation is used to proof the concept and a mathematical model established to relate the internal pressure and the radial strains at different positions in the upper end surface method test equipment.The new equipment is calibrated using oil pressure and strain measurements.The calibrated equipment is then used to measure the expansion pressure of SCA at three different water contents to proof its potential.The differences in the measurements with OPM and UESM at three different moisture contents are less than 4%.The experimental results confirm the accuracy and applicability of the more user friendly and less expensive UESM in the measurement of the expansive pressures of SCAs.展开更多
Polypropylene fiber and expansive agent are used in airport concrete to improve its shrinkage cracking resistance and mechanical properties.The concrete specimens with amount content of polypropylene fiber or expansiv...Polypropylene fiber and expansive agent are used in airport concrete to improve its shrinkage cracking resistance and mechanical properties.The concrete specimens with amount content of polypropylene fiber or expansive agent or both of them are prepared.The morphology of specimens is observed by scanning electron microscope,the time when the first crack occurred is recorded through slap test,and the mechanical properties such as compressive strength and impact energies of concrete are measured.The results show that polypropylene fiber in concrete can reduce the shrinkage and delay the first crack,improve the impact resistance obviously,and improve the compressive strength slightly.Expansive agent can compensate the shrinkage and reduce cracks of concrete pavement markedly,and improve the mechanical properties of concrete pavement slightly.The study provides recommendations for cracking control of airport concrete pavement in the future.展开更多
After having expanded its capacity from 300 kt/a to 450 kt/a in 1994, the steam cracking unit of Yanshan Petrochemical Company was still experiencing such problems as low feedstock flexibility, high energy consumption...After having expanded its capacity from 300 kt/a to 450 kt/a in 1994, the steam cracking unit of Yanshan Petrochemical Company was still experiencing such problems as low feedstock flexibility, high energy consumption and smaller production capacity as compared to other ethylene units constructed in the same time. In order to fully improve technical capability, reduce energy consumption, improve feedstock flexibility and increase production capacity of steam crackers, a lot of technical transform schemes on steam cracking were studied and compared with attention focused on the feasibility, safety, operability of the related revamp schemes, as well as the advanced nature and economical features. The transform scheme decided includes following projects. For the pyrolysis quench compression system, the pyrolysis gasoline fractionation tower is retrofitted on the site, quench water tower, pyrolysis gas compressor and steam turbine are replaced by new ones respectively. For the separation system a low pressure methane removal technology is adopted with the demethanizer tower replaced, coupled with the C 3 catalytic rectification/hydrogenation technology, while the high pressure depropanizer is replaced with addition of a propylene rectification tower. The fractionation flow sheet and equipment are adjusted with addition of a propylene compressor and compressor for binary mixture of methane ethylene cooling agents. The revamped complex has expanded the ethylene capacity to the target of 660 kt/a with the actual capacity reaching 710 kt/a, remarkably reduced the energy consumption, and is capable of using naphtha, light diesel fuel, heavy diesel fuel and the hydrocracked tail oil as the steam cracking feedstock. This project is the first to apply refrigeration by means of a mixed cooling agent and has succeeded in using C\-3 catalytic rectification/hydrogenation technology, which has given an impetus to the progress of steam cracking industry in the world.展开更多
基金Funded by the National Natural Science Foundation of China(No.51578325)。
文摘To investigate the assumptions proposed in this paper,the evolution law governing the strength and expansion performance of MgO and nano-MgO micro-expansive concrete in the environment of mineral powder was firstly observed in this study.Secondly,SEM,XRD,and TG-DSC microscopic tests were conducted to reveal the effects of the active mineral-powder admixture on the hydration degree and expansion performance of MgO and nano-MgO in HPC.Our experimental results successfully verified our hypothesis,which indicated that the expansion performance of macro-MgO and nano-MgO was indeed depressed by the addition of active mineral power admixtures,even though the mechanical property of concrete composites was effectively improved.Furthermore,the hydration test also demonstrated the negative interference on the mineral powders,which was induced by the expansion agents.It is found the amounts of hydrates tend to decrease because the mineral powder ratio reaches and exceeds 40%.Moreover,it is also concluded the effect of expansion agents is governed by the alkalinity cement paste,especially for the nano-MgO.In other words,the expansion performance of nano-MgO will vary more obviously with the hydration process,than MgO.The results of this study provide that effective experimental and theoretical data support the hydration-inhibition mechanism of magnesium expansive agents.
基金funded by the Sinopec Science and Technology Department Project(P21056).
文摘Generally,the so-called expansion agent is very effective in eliminating all the micro-annuli that exist between the casing and the cement sheath or between the cement sheath and the formation.However,this approach can detrimentally affect the sealing ability of cement sheath if the expansion agent is used in an unreasonable way.For these reasons,in the present work,numerical simulations have been conducted to analyze the effect of elasticity modulus of cement sheath,the elasticity modulus of formation,the expansion rate of cement,the geo-stress on the micro-annulus caused by cement expansion,and the cement sheath expansion on the integrity of cement sheath and formation.The micro-annulus between the casing and the cement sheath has been found to decrease according to the ratio between the elasticity modulus of formation and the elasticity modulus of cement sheath.A positive correlation has been observed between the micro-annulus and the cement expansion ratio.The microannulus decreases as the geo-stress increases,but the effect of the geo-stress on the micro-annulus is much smaller.In conclusion,the expansion agent is suitable for the formation in which the elasticity modulus is higher than the cement sheath.
文摘A new type of concrete expansion agent has been successfully developed for the first time in the world by utilizing an industrial waste residue soda residue and an industrial wasteliquor.Adding 3%-6% of the agent into Portland cement enables a shrinkage compensating concrete to be prepared.Mortar and concrete containing this expansion agent have better shrinkage compensating and mechanical properties.The raw materials component,production process,technical properties,micro analysis of mortar made with this expansion agent,mechanism of expansion and research results are described in this article.The experimental results show that the new type of concrete expansion agent accords with the standard and its main mineral component is xCaO ySO 3 zAl 2O 3.
基金supported by the National Natural Science Foundation of China(Nos.51874277 and 41977238)the National Science Fund for Excellent Young Scholars of China(No.52122404).
文摘Rolled static cracking agent(RSCA)can solve the intractable problem of traditional bulk static cracking agent(BSCA)in engineering applications.This paper innovatively studies the rational water-cement ratio of BSCA and the immersion soaking time of RSCA under the condition of controlling temperature.Through the expansion and cracking performance experiments,the development characteristics of expansion pressure,the cracking effect of the single-hole specimen and the performance of hole spraying prevention under the action of BSCA and RSCA were compared and analyzed.The results show that:(1)The volume growth rate of static cracking agent decreases with the increase of water-cement ratio,and the fluidity increases with the increase of water-cement ratio.The rational water-cement ratio for BSCA application is 0.3,and the rational immersion time of RSCA is 2-2.5 min;(2)Under the bore diameters of 30,35,40 and 45 mm,the expansion pressure of BSCA with a water-cement ratio of 0.3 is 38.2,52.3,61.5 and 68 MPa,and the expansion pressure of RSCA immersed in water for 2.5 min is 43.5,58.8,69.5 and 75.1 MPa,respectively.Among them,the development speed of expansion pressure of BSCA is higher than that of RSCA,and the arrival time of the peak expansion pressure of RSCA is 1.7 times that of BSCA;(3)The crack initiation speed of single-hole specimen under the action of RSCA is 10.3%lower than that under the action of BSCA,but the cracking speed of the former is 72.6%higher than that of the latter;(4)The hole spraying occurs in BSCA under the bore diameter of 50,55 and 60 mm,while the hole spraying occurs in RSCA under the bore diameter of 60 mm.In terms of bore diameter,the hole spraying prevention of the RSCA is better than that of BSCA.The research results enrich the static blasting technology and provide data support and theoretical reference for field application.
基金Under the auspices of Social Science and Humanity on Young Fund of the Ministry of Education of China(No.21YJCZH100)the Scientific Research Project on Outstanding Young of the Fujian Agriculture and Forestry University(No.XJQ201920)+1 种基金the Science and Technology Innovation Special Fund Project of Fujian Agriculture and Forestry University(No.CXZX2021032)the Forestry Peak Discipline Construction Project of Fujian Agriculture and Forestry University(No.72202200205)。
文摘It is crucial to investigate the urban agglomerations spatio-temporal evolution patterns and driving factors for analyzing the urban spatial structure-functional division and promoting the coordinated development of urban agglomerations.In this study,a novel vegetation-building-nighttime light-adjusted index(VBNAI)was established for rapid and effective mapping of urban construction land(UCL)in Central Plains Urban Agglomeration(CPUA),China during 2000–2020 based on Google Earth Engine(GEE)platform.Compared with traditional indices,VBNAI can significantly decrease the blooming effect,Normalized Difference Vegetation Index(NDVI)saturation,and soil background of nighttime light data.In addition,the urban expansion indices and standard deviation ellipse model were synthetically adopted to analyze the spatio-temporal evolution pattern of urban expansion.The gravity model and the geographically weighted regression model were employed to determine the spatial interaction forces and drivers of urban expansion,respectively.The results showed that the VBNAI index has obvious advantages in efficiency and accuracy to extract UCL with the overall accuracy of more than 91%.The UCL of CPUA had increased by 4489.84 km2 during 2000–2020 with the gravity center moving towards southeast continuously.From 2000 to 2010,the urban expansion was in a‘center-hinterland’pattern which had benefit from the favorable effect of the traffic shaft belt.During 2010–2020,the urban network structure had basically established.Urban expansion had been influenced by a variety of socio-economic and demographic factors,and the impact degree varied from region to region.This study could provide scientific references for facilitating the intensive utilization of urban resources and optimizing the spatial development pattern of urban agglomeration.
基金National Natural Science Foundation of China, No.40771198Hunan Provincial Natural Science Foundation of China, No.08JJ6023
文摘Although traditional urban expansion simulation models can simulate dynamic features, these models fail to address complex changes produced by different agents' behaviors. The paper has built up a set of spatial-temporal land resource allocation rules and developed a dynamic urban expansion model based on a multi-agent system, which can simulate the interaction among different agents, such as residents, peasants, and governments. This model is applied to simulate urban expansion process taking Changsha City, in China as a study area. The results show that this model can not only reflect basic characteristics of urban expansion, but also help explain the reasons for urban expansion process and understand the effect of agents' behavior on the expansion process, and provide insights into the causing factors behind the expansion. In addition, in contrast to simulation results with land use classification map from remote sensing images, the precision of the simulation reached over 68% with higher precision than cellular automata model according to the cell-by-cell comparison. The results suggest that the model can help to provide land use decision making support to government and urban planners.
基金Under the auspices of National Science and Technology Support Program of China(No.2012BAH29B04-00)
文摘In this study,three-phase satellite images were used to define rules for the allocation of time and space in construction land resources based on a complex adaptive system and game theory.The decision behavior and rules of government agent,enterprise agent and resident agent in construction land growth were explored.A distinctive and dynamic simulation model of construction land growth was built,which integrated multi-agent,GIS technology and RS data and described the interaction among influencing agents.Taking Fuyang City in the Changjiang River Delta as an example,an assessment process for the remote sensing data in construction land and scenario planning was constructed.Repast and ArcGIS were used as simulation platforms.A simulation of the spatial pattern in land-use planning and the setting of scenario planning were conducted by using the incomplete active game,which was based on different natural,social and economic levels.Through this model,a simulation of urban planning space and decision-making for Fuyang City was created.Relevant non-structured problems arising from urban planning management could be identified,and the process and logic of urban planning spatial decision-making could thus be improved.Cel1-by-cel1 comparison showed that the simulation accuracy was over 72%.This model has great potential for use by government and town planners in decision support and technique support in the policy-making process.
基金Funded by the National Natural Science Foundation of China (No. 60672166)the Bureau of Water Resources & Hydropower Research of China (No. SPKJ006-13-01-01)
文摘The effects of fly ash and MgO-type expansive agent on the shrinkage and expan-sive strain of concrete with high magnesia cement were investigated. The results show that high volumes of fly ash may reduce the shrinkage strain of concrete and inhibit the expansive strain of concrete with MgO-type expansive agent, but can not eliminate the shrinkage of concrete. MgO-type expansive agent may produce expansive strain and compensate the shrinkage strain of concrete, re-lieve the cracking risk, but the hydration product of magnesia tends to get together in paste and pro-duce expansive cracking of concrete with high magnesia content according to SEM observation.
基金Funded by the National Project of "863" (2009AA03Z508)XiBu Traffic Program (2009ZB01)
文摘The hydration behaviors and expansive properties of MgO-type expansive agent curing at different temperatures and environment were investigated.When the curing temperatures changed from 25℃ to 50℃,the conductivities of MgO samples increased from 40 to 80 μs/cm,and the hydrations of MgO were quickened up obviously.Through SEM observation,the hydration product of MgO cured at 50℃ for 28 day was about 2-3μm in length.The expansion of pastes with 5% of the MgO-type expansive agent was from 0.36% to 1.01% when the curing temperature changed from 25oC to 50℃.When 8% of the MgO-type expansive agent was added,the early shrinkage of concrete was reduced.The expansion ratio increased with the curing temperature,and the expansive cracking of concrete with MgO-type expansive agent might be decreased by blending fly ash.
基金Funded by the National Basic Research Program of China (2009CB623105)the "11th Five-Year Plan" Scientific and Technological Support Project of China (2006BAF02A25)
文摘The effect of combination of steel fiber and MgO-type expansive agent (MEA) on strength, air-permeability and porosity of concrete was investigated. The porosity and air-permeability of concrete were determined by method of evaporated water and Torrent permeability tester, respectively. Pore structures of mortars in concrete were analyzed using mercury intrusion porosimetry (MIP). Interfacial structures between steel fibers and matrix were examined by use of optical microscope. The experimental results show that improvement of pore structures of mortar and fiber-matrix interfacial structure in concrete by combination of steel fiber and MEA may remarkably increase properties of concrete. In comparison with plain concrete, compressive strength and splitting tensile strength of steel fiber reinforced expansive concrete increased by 15.3% and 38.1%, permeability coefficient Kt, penetration depth L and porosity of concrete decreased by 41.1%, 21.3% and 13.1% at 28 days, respectively.
文摘The self-stress trial of the fifteen high-strength, low-heat andmicro-expansion concrete-filled steel tube(CFST)is introduced, andthe generating and distributing features of pre-stress and itsrelation to add- ing quantity of expansive agent, which providespersuasive dependences for optimal design of high-strength, low- heatand micro-expansion CFST were investigated, especially for the designof added quantity of expansive agent.
基金Funded by the State "the Nineth Five-Plan"of Communica-tion Ministry(95 - 05 - 02 - 25)
文摘By employing different forms and amounts of materials, many kinds of ettringite type expansive agents had been prepared. The relationship between the compositions and properties of expansive agents was analyzed. The design methods of expansive agent have been put forward according to the property, requirement of expansive concrete.
基金supported by the High-Level Talent Project Funding Scheme,Post-doctoral fund of China and Jiangsu (Nos.1301057B,2014M551588)the Fundamental Research Funds Universities(No.NS2015010)
文摘The mechanisms and processes of sulfate attack on roller compacted concrete(RCC)with MgO expansive agent are proposed by investigating the microstructure and hydration products in specimens immersed in 5%sodium sulfate solution for one year with the optical micrograph,scanning electron microscopy(SEM)and scanning electron microscopy-energy dispersive spectrometer(SEM-EDS).The results show that the deterioration of concrete due to the sulfate attack is mainly loss of stiffness,strength and adhesion,and expansion cracking is mainly caused by the formation of gypsum and ettringite.In the presence of MgO expansive agent,the microstructures of RCC can be improved by hydration and un-hydrated products,the large pores and permeability are reduced,and the resistance to sulfate corrosion of concrete and durability of hydraulic structure are improved slightly.
基金funded by the State Key Research Development Program of China(No.2018YFC0604400)the National Science Foundation of China(Nos.51874068,52074062)+2 种基金the Fundamental Research Funds for the Central Universities(Nos.N2001003,N160107001,N180701016,N182608003,N2001001)the 111 Project(No.B17009)The authors also acknowledge Nazarbayev University for funding the research through its Collaborative Research Program(No.OPCRP2020014).
文摘Static cracking agent(SCA)is actively investigated as an alternative to explosive blasting for rock breakage due to its immense expansion property.SCA can eliminate the negative effects of shock,noise and harmful gases encountered in explosive blasting processes.Accurate measurement and deep understanding of the expansive properties of SCAs are important in their industrial application.An improved outer pipe method(OPM),termed the upper end surface method(UESM),is proposed in this paper to overcome the shortcomings of the OPM in the expansive pressure measurement of SCAs.Numerical simulation is used to proof the concept and a mathematical model established to relate the internal pressure and the radial strains at different positions in the upper end surface method test equipment.The new equipment is calibrated using oil pressure and strain measurements.The calibrated equipment is then used to measure the expansion pressure of SCA at three different water contents to proof its potential.The differences in the measurements with OPM and UESM at three different moisture contents are less than 4%.The experimental results confirm the accuracy and applicability of the more user friendly and less expensive UESM in the measurement of the expansive pressures of SCAs.
基金Supported by the High-Level Talent Funding and Construction System of Jiangsu Province(JZ-010,2013ZD12)the China Post-Doctoral Science Foundation(2014M551588,1301057B)the National High-Tech Research and Development Program of China("863"Program)(2009AA03Z508)
文摘Polypropylene fiber and expansive agent are used in airport concrete to improve its shrinkage cracking resistance and mechanical properties.The concrete specimens with amount content of polypropylene fiber or expansive agent or both of them are prepared.The morphology of specimens is observed by scanning electron microscope,the time when the first crack occurred is recorded through slap test,and the mechanical properties such as compressive strength and impact energies of concrete are measured.The results show that polypropylene fiber in concrete can reduce the shrinkage and delay the first crack,improve the impact resistance obviously,and improve the compressive strength slightly.Expansive agent can compensate the shrinkage and reduce cracks of concrete pavement markedly,and improve the mechanical properties of concrete pavement slightly.The study provides recommendations for cracking control of airport concrete pavement in the future.
文摘After having expanded its capacity from 300 kt/a to 450 kt/a in 1994, the steam cracking unit of Yanshan Petrochemical Company was still experiencing such problems as low feedstock flexibility, high energy consumption and smaller production capacity as compared to other ethylene units constructed in the same time. In order to fully improve technical capability, reduce energy consumption, improve feedstock flexibility and increase production capacity of steam crackers, a lot of technical transform schemes on steam cracking were studied and compared with attention focused on the feasibility, safety, operability of the related revamp schemes, as well as the advanced nature and economical features. The transform scheme decided includes following projects. For the pyrolysis quench compression system, the pyrolysis gasoline fractionation tower is retrofitted on the site, quench water tower, pyrolysis gas compressor and steam turbine are replaced by new ones respectively. For the separation system a low pressure methane removal technology is adopted with the demethanizer tower replaced, coupled with the C 3 catalytic rectification/hydrogenation technology, while the high pressure depropanizer is replaced with addition of a propylene rectification tower. The fractionation flow sheet and equipment are adjusted with addition of a propylene compressor and compressor for binary mixture of methane ethylene cooling agents. The revamped complex has expanded the ethylene capacity to the target of 660 kt/a with the actual capacity reaching 710 kt/a, remarkably reduced the energy consumption, and is capable of using naphtha, light diesel fuel, heavy diesel fuel and the hydrocracked tail oil as the steam cracking feedstock. This project is the first to apply refrigeration by means of a mixed cooling agent and has succeeded in using C\-3 catalytic rectification/hydrogenation technology, which has given an impetus to the progress of steam cracking industry in the world.