Background Dual-energy CT(DECT)provides several novel methods to assess thrombus perviousness.We aimed to evaluate whether the novel thrombus perviousness measured with DECT is associated with improved recanalisation ...Background Dual-energy CT(DECT)provides several novel methods to assess thrombus perviousness.We aimed to evaluate whether the novel thrombus perviousness measured with DECT is associated with improved recanalisation and better functional outcomes in acute ischaemic stroke(AIS)patients with endovascular thrombectomy(EVT).Methods 108 AIS patients with middle cerebral artery occlusion who underwent DECT angiography on admission and received EVT treatment between April 2020 and September 2023 were retrospectively analysed.Thrombus attenuation increase(TAI)was evaluated on routine CT angiography and non-contrast CT,and DECT quantitative parameters of thrombus,including iodine concentration(IC)and normalised IC(NIC)were measured.Multivariable logistic regression analysis was used to evaluate the association of thrombus characteristics with arterial occlusive lesion scale and 90-day modified Rankin Scale.Results NIC was significantly associated with successful recanalisation(OR 1.372(95%CI 1.194 to 1.625);p<0.001)and good functional outcome(OR 1.252(95%CI 1.114 to 1.446);p<0.001).NIC yielded higher performance,with area under curve(AUC)of 0.789 and 0.740,in the prediction of recanalisation and functional outcome than TAI(AUCs=0.635 and 0.592).Compared with low-level NIC thrombus,high-level NIC was associated with 11.4 and 15.4 times higher likelihood of successful recanalisation and good functional outcome.Moreover,NIC was a significant indicator to differentiate large artery atherosclerosis from cardioembolism stroke with high specificity and positive predictive value.Conclusions Higher DECT-derived NIC is associated with increased odds of successful recanalisation and good functional outcome for EVT patients,and it yielded higher prediction performance than TAI.展开更多
By adding zeolite aggregate with good adsorption properties,different mix ratios of added zeolite pervious concrete(ZPC)were designed to compare the water purification effect of ordinary pervious concrete and water pu...By adding zeolite aggregate with good adsorption properties,different mix ratios of added zeolite pervious concrete(ZPC)were designed to compare the water purification effect of ordinary pervious concrete and water purification tests that were conducted.The pore characteristics of the pervious concrete were identified using three-dimensional reconstruction software and the relationship between pore structure and water purification performance was quantified by gray entropy correlation analysis.The results showed that the purification efficiency of zeolite-doped pervious concrete was 17.6%-22.3%higher than that of ordinary pervious concrete.The characteristic parameters of the pore structure of permeable concrete,i.e.planar porosity and tortuosity,were determined using three-dimensional reconstruction software.The correlation between the degree of tortuosity and the removal rate reached more than 0.90,indicating that the internal pore structure of pervious concrete has a good correlation with the water purification performance.展开更多
The degradation performance of pervious concrete containing TiO_(2)/LDHs-loaded recycled aggregates for NO gas was analyzed using a gas phase catalytic degradation test device,simulating different environmental condit...The degradation performance of pervious concrete containing TiO_(2)/LDHs-loaded recycled aggregates for NO gas was analyzed using a gas phase catalytic degradation test device,simulating different environmental conditions such as load,ambient temperature,and illumination intensity,which provides theoretical support for practical engineering.The experimental results indicate that when the ambient temperature is controlled at 25℃and the illumination intensity is 30 W/m^(2),the sample prepared by soaking recycled aggregates in a 0.8%TiO_(2)/LDHs suspension exhibits the highest photocatalytic degradation rate for NO gas,reaching 72.54%.Further investigation on the influence of environmental temperature reveals that,at 25℃,the maximum photocatalytic degradation rate for NO gas is 72.9%.Moreover,at an illumination intensity of 40 W/m^(2),the maximum photocatalytic degradation rate for NO gas is 87.08%.Additionally,after three repeated photocatalytic tests,the sample demonstrates good stability,with a photocatalytic degradation rate of 58%.The nitrogen content in the eluent obtained from soaking the sample was determined to be 0.0022 mol/L,with a recovery rate of 80%.The adsorption experiment demonstrates that the sample exhibits a favorable adsorption effect on nitrate ions,reaching a maximum of 56.8%.展开更多
The size effects were experimentally investigated and the underlying mechanism was analyzed.The results reveal that,as the specimen size increases,the interconnectivity of macropores slightly decreases.This in turn co...The size effects were experimentally investigated and the underlying mechanism was analyzed.The results reveal that,as the specimen size increases,the interconnectivity of macropores slightly decreases.This in turn constrains the diffusion of CO_(2) and moisture in the specimens,resulting in an increase in the discrepancy between the internal and external carbonation degrees.An increase in cement paste thickness simultaneously decreases the quantity,average size,and interconnectivity of macropores,lowering the diffusion efficacy of CO_(2) and moisture and exacerbating the overall heterogeneity in carbonation.Moreover,the gradual blockage of macropores leads to the emergence of localized ‘occluded zones’ with much lower carbonation degree.The reduction in aggregate size significantly alters the average diameter and connectivity of macropores,leading to notable change to overall non-uniformity.This study provides insight into improving the CO_(2) curing effect of pervious concrete products and developing uniform curing methods.展开更多
The pollutant loads of surface runoff in an urban tourist area have been investigated for two years in the Wuhan City Zoo, China. Eight sampling sites, including two woodlands, three animal yards, two roofs and one ro...The pollutant loads of surface runoff in an urban tourist area have been investigated for two years in the Wuhan City Zoo, China. Eight sampling sites, including two woodlands, three animal yards, two roofs and one road, were selected for sampling and study. The results indicate that pollutants ranked in a predictable order of decreasing load （e.g. animal yard〉roof〉woodland〉road）, with animal yards acting as the key pollution source in the zoo. Pollutants were transported mainly by particulate form in runoff. Particulate nitrogen and particulate phosphorous accounted on average for 61%, 78% of total pollutant, respectively, over 13 monitored rainfall events. These results indicate the treatment practices should be implemented to improve particulate nutrient removal. Analysis of the M（V） curve indicate that no first flush effect existed in the surface runoff from pervious areas （e.g. woodland, animal ground yard）, whereas a first flush effect was evident in runoff from impervious surfaces （e.g. animal cement yard, roof, road）.展开更多
A high strength self-compacting pervious concrete(SCPC) with top-bottom interconnected pores was prepared in this paper. The frost-resisting durability of such SCPC in different deicing salt concentrations(0%, 3%, 5%,...A high strength self-compacting pervious concrete(SCPC) with top-bottom interconnected pores was prepared in this paper. The frost-resisting durability of such SCPC in different deicing salt concentrations(0%, 3%, 5%, 10%, and 20%) was investigated. The mass-loss rate, relative dynamic modulus of elasticity, compressive strength, flexural strength and hydraulic conductivity of SCPC after 300 freeze-thaw cycles were measured to evaluate the frost-resisting durability. In addition, the microstructures of SCPC near the top-bottom interconnected pores after 300 freeze-thaw cycles were observed by SEM. The results show that the high strength SCPC possesses much better frost-resisting durability than traditional pervious concrete(TPC) after 300 freeze-thaw cycles, which can be used in heavy loading roads. The most serious freeze-thaw damage emerges in the SCPC immersed in the 3% of Na Cl solution, while there is no obvious damage in 20% of Na Cl solution. Furthermore, it can be deduced that the high strength SCPC can be used for 100 years in a cold environment.展开更多
Surface textures had long been recognized as primary factors to provide the skid resistance on pavements; however, no measurement of skid resistance on pervious concrete pavement with various surface texture parameter...Surface textures had long been recognized as primary factors to provide the skid resistance on pavements; however, no measurement of skid resistance on pervious concrete pavement with various surface texture parameters had been made. Fractal geometry was introduced in the present work to accurately simulate transect contour curves of pervious concrete specimens through fractal interpolation. It is proved that its fractal dimension (D) can be adopted to measure the skid resistance on pervious concrete pavement, overcoming the shortcomings of both macrotexture depth (DT ) and British portable pendulum number (NBP). Combined with Fujikawa-Koike tire/road contact model, the optimization method of all surface textures was recommended for designing and constructing excellently skid-resistant and noise-absorptive pervious concrete pavement. In addition, evaluating of the abrasion process and attenuation of the surface textures on concrete pavement slabs was also the focus of this work based on accelerated abrasion test. Results show that the surface textures on pervious concrete pavement slabs is extremely durable, compared to those on conventional grooved or exposed aggregate concrete pavement slabs.展开更多
An improved design method of pervious concrete was proposed to lower the deviation between the designed and actual porosity and maintain both mechanical property and permeability of pervious concrete. The improved des...An improved design method of pervious concrete was proposed to lower the deviation between the designed and actual porosity and maintain both mechanical property and permeability of pervious concrete. The improved design method is mainly based on the optimal volume ratio of paste to aggregate(VRPA), which was determined by testing the average thickness of cement paste coating aggregate. The performances of pervious concrete designed by the traditional method and the improved one were compared. The results show that with the increase of designed porosity, the reduction of compressive strength and flexural strength of pervious concrete designed by the improved method is significantly smaller than those designed by the traditional one. The maximum deviation between the designed and actual porosity of the pervious concrete by the improved method is only 1.54%, which is far less than 8.7% obtained by the traditional one. Micro-structural analysis shows that the porous distribution of pervious concrete designed by improved method exhibits better uniformity.展开更多
Compressive and flexural strength,fracture energy,as well as fatigue property of pervious cement concrete with either supplementary cementitious materials (SCMs) or polymer intensified,were analyzed.Test results show ...Compressive and flexural strength,fracture energy,as well as fatigue property of pervious cement concrete with either supplementary cementitious materials (SCMs) or polymer intensified,were analyzed.Test results show that the strength development of SCM-modified pervious concrete (SPC) differs from that of polymer-intensified pervious concrete (PPC),and porosity has little effect on their strength growth.PPC has higher flexural strength and remarkably higher flexural-to-compressive strength ratio than SPC at the same porosity level.Results from fracture test of pervious concrete mixes with porosity around 19.5% show that the fracture energy increases with increasing the dosage of polymer,reflecting the ductile damage features rather than brittleness.PPC displays far longer fatigue life than SPC for any given failure probability and at any stress level.It is proved that two-parameter Weibull probability function describes the flexural fatigue of pervious concrete.展开更多
A recycled aggregate(RA)was prepared by crushing and sieving demolished discarded concrete pavements and was subsequently tested and analyzed to determine its various physical properties.On this basis,pervious concret...A recycled aggregate(RA)was prepared by crushing and sieving demolished discarded concrete pavements and was subsequently tested and analyzed to determine its various physical properties.On this basis,pervious concrete(PC)mix proportions were designed.Coarse RA particles with sizes of 5–10 and 10–20 mm were selected.Concrete specimens were prepared with a water–cement ratio of 0.3,an aggregate–cement ratio of 4.5,the substitute rates of RA with 0,25%,50%,75%and a single-/double-gap-graded RA mix(mass ratio of particles with sizes of 5–10 mm to particles with sizes of 10–20 mm:1:1,1:2,2:1,2:3 and 3:2).Various properties of the RA-containing PC(RPC)were determined by analyzing the compressive strength,splitting tensile strength,effective porosity,permeation coefficient and impact and abrasion resistance of the specimens.The results showed the following:The density of the RPC decreased with an increasing RA replacement ratio.The density of the RPC prepared with a double-gapgraded RA mix was lower than that prepared with a single-gap-graded RA(particle size:10–20 mm)mix.The permeation coefficient of the RPC increased with increasing porosity.The splitting tensile strength of the RPC was positively correlated with its compressive strength.The compressive strength of the RPC decreased with increasing porosity.The regression analysis showed that the impact and abrasion resistance of the RPC increased with increasing compressive strength.In addition,all of the RPC specimens met the strength and permeation requirements.This study can provide theoretical support for the application of RPC.展开更多
Pervious concrete(PC)is at risk of clogging due to the continuous blockage of sand into it during its service time.This study aims to evaluate and predict such clogging behavior of PC using hybrid machine learning tec...Pervious concrete(PC)is at risk of clogging due to the continuous blockage of sand into it during its service time.This study aims to evaluate and predict such clogging behavior of PC using hybrid machine learning techniques.Based on the 84 groups of the dataset developed in the earlier study,the clogging behavior of the PC was determined by the algorithm combing the SVM(support vector machines)and particle swarm optimization(PSO)methods.The PSO algorithm was employed to adjust the hyperparameters of the SVM and verify the performance using 10-fold cross-validation.The predicting results of the developed model were assessed by the coefficient of determination(R)and root mean square error(RMSE).The importance of the influential variables on the clogging behavior of PC was evaluated as well.The results showed that the PSO algorithm can effectively adjust the hyperparameters of the SVM model and can be used to construct the predictive model for the clogging behavior of the PC.The combined algorithm has the advantage of higher reliability and validity than the random hyperparameters selection.For the verification process,the developed model was able to obtain values of 0.9469 and 1.8148 for the R and RMSE,showing that the developed machine learning model can accurately be used to evaluate and predict the clogging behavior of the PC,guiding the mix-design of PC from the perspective of durability.The size of the clogging sand is the most important parameter and the thickness of the sample is the least significant factor affecting the clogging behavior.The proportions of the smallest aggregate size and largest aggregate size are the two most important design parameters of concrete with the consideration of the relatively higher importance scores,showing these two aggregates should be given special attention in future PC design for anti-clogging purposes.展开更多
The effects of the proportion of fine aggregate, the maximum size of the aggregate and the proportion of the 9.5 mm to 4.75 mm particle in the coarse aggregate on the properties of the porous concrete are investigated...The effects of the proportion of fine aggregate, the maximum size of the aggregate and the proportion of the 9.5 mm to 4.75 mm particle in the coarse aggregate on the properties of the porous concrete are investigated. Results indicate that the porous concrete with a cement dosage only 150 kg/m^3 has high strength and satisfying permeability when the aggregate has a passing percentage of 4.75 mm around 10% to 15%, with the increase of the maximum size of the aggregate, the strength of the porous concrete decreases and the permeability increases. When the proportion of the 9.5 mm to 4.75 mm particle in the coarse aggregate is about 20%, there are no interference among the particles by Weymouth theory, the strength of the pervious porous concrete reaches the peak value. The optimum continues gradation limit of the aggregate for porous concrete pervious road base material is recommended according to the theoretical calculation and experimental results.展开更多
Pervious concrete is recommended,which is of great benefit to the ecological environment and human living environment.In this paper,the influences of five water-cement ratios and four fly ash contents to replace the c...Pervious concrete is recommended,which is of great benefit to the ecological environment and human living environment.In this paper,the influences of five water-cement ratios and four fly ash contents to replace the cement by mass with a water-cement ratio of 0.30 on the properties of Recycled Aggregate Pervious Concrete(RAPC)were studied.Following this,based on the Grey relational-Technique for Order Preference by Similarity to an Ideal Solution(TOPSIS)optimization method,the strength,permeability,abrasion loss rate,and material costs of RAPC were adopted as evaluation indices to establish a mix proportion optimization model.The results show that the increase of water-cement ratio and fly ash replacement level of RAPC leads to decreased compres-sive strength while an increase in the permeability and abrasion loss rate.According to test results based on the optimal model 0.30 was identified as the best mix proportion.In addition,ecological-economic analysis of RAPC raw materials was carried out by comparing different natural aggregates.The results of EE(embodied energy)and ECO 2e(embodied CO_(2) emission)pointed out that the combination of recycled aggregate and fly ash leads to sig-nificant ecological and economic benefits.展开更多
Many dangerous effects arise from seepage through earth dams based on pervious layer. Therefore, the dam embankment must be provided with seepage control measures to avoid such effects. In the present work, different ...Many dangerous effects arise from seepage through earth dams based on pervious layer. Therefore, the dam embankment must be provided with seepage control measures to avoid such effects. In the present work, different control methods were used such as flat slopes, toe drainage systems, and a catch drain in the tail water. The hydraulic performance of each control measure was evaluated using the analytical solutions, previously developed, to estimate the seepage quantity (q), the height of seepage surface (h<sub>3</sub>), and the coordinates of the free surface (h<sub>x</sub>). Study was conducted on a physical model for a dam embankment having a top width (b) = 10.0 meter, height (H<sub>d</sub>) = 30.0 meter, and slope factor (m) = 1.5. The obtained results were analyzed and presented in dimensionless charts. Results showed that, the used control measures possess a great effect on the characteristics of seepage through earth dams based on pervious foundations. A comparative study was conducted between the studied toe drainage systems to enable the designers the better choice for design purposes.展开更多
Employing Biot’s theory of wave propagation in liquid saturated porous media, waves propagating in a hollow poroelastic closed spherical shell filled with fluid are studied. The frequency equation of axially symmetri...Employing Biot’s theory of wave propagation in liquid saturated porous media, waves propagating in a hollow poroelastic closed spherical shell filled with fluid are studied. The frequency equation of axially symmetric vibrations for a pervious and an impervious surface is obtained. Free vibrations of a closed spherical shell are studied as a particular case when the fluid is vanished. Frequency as a function of ratio of thickness to inner radius is computed in absence of dissipation for two types of poroelastic materials each for a pervious and an impervious surface. Results of previous works are obtained as a particular case of the present study.展开更多
The goal of this study was to compare the predicted void content with the actual void content of pervious concrete cylinders. All pervious concrete systems are designed with a void content in mind to facilitate a spec...The goal of this study was to compare the predicted void content with the actual void content of pervious concrete cylinders. All pervious concrete systems are designed with a void content in mind to facilitate a specific permeability;however, due to variable placing techniques and inherent issues with the material, the actual in place void content often varies from designed. This study quantifies this difference and attempts to develop a correction factor, such that design values are more approximate to in place pervious concrete systems. The analysis included multiple mixtures with three design void contents (15%, 25%, 35%), two aggregate types (angular and rounded), and three different water-to-cement ratios (0.33, 0.37, 0.41). These samples were methodically designed to contain a desired void ratio, then casted in the laboratory, in which the compaction of each sample was controlled for consistency. Following casting, the in-place void content was determined using ASTM C1754 and compared to the predicted. The difference was then averaged to create a correction factor requiring more or less cement paste, which was used to redesign the mixtures. The new mixtures were then compared to the predicted void content. The results of this study show that initial designs can vary from 3% - 15% on average from initial designed void content and that a correction factor can be used to obtain within 3% on average of the target void ratios.展开更多
Understanding the hydrologic budget is crucial in planning for community based water supply. The water budget includes rainfall intensity, groundwater recharge, interception, evapotranspiration, and surface runoff. Th...Understanding the hydrologic budget is crucial in planning for community based water supply. The water budget includes rainfall intensity, groundwater recharge, interception, evapotranspiration, and surface runoff. The percentage of rain going to recharge groundwater, rivers, and lakes is very important from the standpoint of human water consumption and ecosystems service. The objective of this work is to determine the recharge potential of groundwater in the Mokonde Community, Southern Sierra Leone. The community is dependent on wells as the main source of domestic water supply. This research need was born out of the absence of available data to show the relationship between rainfall amounts and groundwater recharge in the study area. In this study we monitored groundwater in a well at the United Methodist Church (UMC) compound at Ngegba Street. Automatic water logging devices were deployed to take readings in water level fluctuations every 15 minutes. Monitoring continued throughout the hydrological year of Sierra Leone. A rain gauge was deployed at neighboring UMC Primary School, and daily rainfall records taken at 9:00 a.m. Our team members also deployed at the well on a daily basis to collect data on abstraction of water. The results revealed, through a 29-year rainfall data and the Specific Yield, that 1170 mm of rainfall (48%) was the maximum potential of rainfall that would make groundwater a convenient source of water supply in the area. This demand was higher with the recent 1-year rainfall data. Increase in settlement had likely led to reduction in pervious area, and hence more and more rainfall needed for recharge. The time it took for maximum recharge (4 weeks) was shorter than that for maximum discharge (28 - 30 weeks). Groundwater flowed southwards towards the Gbengitay stream, which drained into the Tia River. These results would inform first step in delineating the water balance in the study area. Future studies could include the quality aspect, stream/river flow, interception and evapotranspiration. These pieces of information are required to help informed decision for water security.展开更多
A study evaluating the relationship between porosity and permeability coefficient for pervious concrete (PC) is presented. In addition, the effect of mixture design parameters particularly, water-to-cement ratio (W/C)...A study evaluating the relationship between porosity and permeability coefficient for pervious concrete (PC) is presented. In addition, the effect of mixture design parameters particularly, water-to-cement ratio (W/C) and size of aggregate on the permeability coefficient of PC was investigated. The PC mixtures were made with 4 range of W/C and 2 range size of aggregate. PC mixes were made from each aggregate and were tested. The results showed that the W/C and aggregate size are key parameters which significantly affect the characteristic performance of PC. Permeability coefficient of coarse pervious concrete (CPC) is bigger than fine pervious concrete (FPC) and the porosity of CPC are bigger than porosity of FPC. A regression model (RM) along with analysis of variance (ANOVA) was conducted to study the significance of porosity distribution on permeability coefficient of PC. The statistical model developed in this study can facilitate prediction permeability coefficient of CPC and FPC as the sustainable pavements.展开更多
The application of the concept of sponge city in engineering and construction can efficiently reduce the surface runoff and peak flow,prevent surface flooding,and purify rainwater,thus achieving the recycle of water r...The application of the concept of sponge city in engineering and construction can efficiently reduce the surface runoff and peak flow,prevent surface flooding,and purify rainwater,thus achieving the recycle of water resources.In this paper,ecological technologies including the permeable concrete floor,sunken green space,grassed swale,ecological tree pool,and catchment module were comprehensively used in the construction of ecological squares.It can be said that this paper has carried on the effective exploration and practice of ensuring the city's water ecological security,promoting the transition of the traditional concept of urbanization construction in China and the sustainable development of the modernization construction of urban clusters.展开更多
High-strength pervious concrete(HSPC) with porosity ranging from 0.08% to 2.011% was prepared. The mechanical properties and rainstorm waterlogging resistance of HSPC were evaluated,and a design method of HSPC pore ch...High-strength pervious concrete(HSPC) with porosity ranging from 0.08% to 2.011% was prepared. The mechanical properties and rainstorm waterlogging resistance of HSPC were evaluated,and a design method of HSPC pore characteristics(porosity and pore diameter) based on the mechanical properties and rainstorm waterlogging resistance was proposed. The results showed that the reduction of effective cross-sectional area caused by artificial channels was the main factor affecting flexural strength but had limited influence on compressive strength. Compared with the concrete matrix without artificial channels,the compressive strength of HSPC with porosity of 2.011% decreased by 7.4%, while the flexural strength decreased by 48.3%. The permeability coefficient of HSPC can reach 16.35 mm/s even at low porosity(2.011%).HSPC can meet the requirements of no rainstorm waterlogging, even if exposed to 100-year rainstorms. When the mechanical properties and rainstorm waterlogging resistance are compromised, the recommended porosity ranges from 1.1% to 3.5%, and the recommended pore diameter ranges from 0.8 to 2.7 mm.展开更多
基金sponsored by Tianjin Health Research Project(Grant No.TJWJ2022QN061 to SL)Tianjin Medical Talent Project(Grant No.TJSJMYXYC-D2-059 to TH)Tianjin Municipal Health Commission Special Plan for High Level Talents in Science and Technology Project(Grant No.TJWJ2024RC016 to TH).
文摘Background Dual-energy CT(DECT)provides several novel methods to assess thrombus perviousness.We aimed to evaluate whether the novel thrombus perviousness measured with DECT is associated with improved recanalisation and better functional outcomes in acute ischaemic stroke(AIS)patients with endovascular thrombectomy(EVT).Methods 108 AIS patients with middle cerebral artery occlusion who underwent DECT angiography on admission and received EVT treatment between April 2020 and September 2023 were retrospectively analysed.Thrombus attenuation increase(TAI)was evaluated on routine CT angiography and non-contrast CT,and DECT quantitative parameters of thrombus,including iodine concentration(IC)and normalised IC(NIC)were measured.Multivariable logistic regression analysis was used to evaluate the association of thrombus characteristics with arterial occlusive lesion scale and 90-day modified Rankin Scale.Results NIC was significantly associated with successful recanalisation(OR 1.372(95%CI 1.194 to 1.625);p<0.001)and good functional outcome(OR 1.252(95%CI 1.114 to 1.446);p<0.001).NIC yielded higher performance,with area under curve(AUC)of 0.789 and 0.740,in the prediction of recanalisation and functional outcome than TAI(AUCs=0.635 and 0.592).Compared with low-level NIC thrombus,high-level NIC was associated with 11.4 and 15.4 times higher likelihood of successful recanalisation and good functional outcome.Moreover,NIC was a significant indicator to differentiate large artery atherosclerosis from cardioembolism stroke with high specificity and positive predictive value.Conclusions Higher DECT-derived NIC is associated with increased odds of successful recanalisation and good functional outcome for EVT patients,and it yielded higher prediction performance than TAI.
基金Hunan Provincial Department of Water Resources:Research on Formula Optimization and Performance Evaluation System of Ecological Concrete for River Water Quality Purification Based on the Dual Carbon Goal(Project No.:XSKJ2024064-44)。
文摘By adding zeolite aggregate with good adsorption properties,different mix ratios of added zeolite pervious concrete(ZPC)were designed to compare the water purification effect of ordinary pervious concrete and water purification tests that were conducted.The pore characteristics of the pervious concrete were identified using three-dimensional reconstruction software and the relationship between pore structure and water purification performance was quantified by gray entropy correlation analysis.The results showed that the purification efficiency of zeolite-doped pervious concrete was 17.6%-22.3%higher than that of ordinary pervious concrete.The characteristic parameters of the pore structure of permeable concrete,i.e.planar porosity and tortuosity,were determined using three-dimensional reconstruction software.The correlation between the degree of tortuosity and the removal rate reached more than 0.90,indicating that the internal pore structure of pervious concrete has a good correlation with the water purification performance.
基金Funded by the National Natural Science Foundation of China(No.52478281)the Natural Science Foundation of Zhejiang Province(No.LZ22E080003)the Science and Technology Project of Zhejiang Provincial Department of Transport(No.202225)。
文摘The degradation performance of pervious concrete containing TiO_(2)/LDHs-loaded recycled aggregates for NO gas was analyzed using a gas phase catalytic degradation test device,simulating different environmental conditions such as load,ambient temperature,and illumination intensity,which provides theoretical support for practical engineering.The experimental results indicate that when the ambient temperature is controlled at 25℃and the illumination intensity is 30 W/m^(2),the sample prepared by soaking recycled aggregates in a 0.8%TiO_(2)/LDHs suspension exhibits the highest photocatalytic degradation rate for NO gas,reaching 72.54%.Further investigation on the influence of environmental temperature reveals that,at 25℃,the maximum photocatalytic degradation rate for NO gas is 72.9%.Moreover,at an illumination intensity of 40 W/m^(2),the maximum photocatalytic degradation rate for NO gas is 87.08%.Additionally,after three repeated photocatalytic tests,the sample demonstrates good stability,with a photocatalytic degradation rate of 58%.The nitrogen content in the eluent obtained from soaking the sample was determined to be 0.0022 mol/L,with a recovery rate of 80%.The adsorption experiment demonstrates that the sample exhibits a favorable adsorption effect on nitrate ions,reaching a maximum of 56.8%.
基金Funded by the National Natural Science Foundation of China (No.22203066)the 6th Young Elite Scientist Sponsorship Program by China Association for Science and Technology (No.2020QNRC001)。
文摘The size effects were experimentally investigated and the underlying mechanism was analyzed.The results reveal that,as the specimen size increases,the interconnectivity of macropores slightly decreases.This in turn constrains the diffusion of CO_(2) and moisture in the specimens,resulting in an increase in the discrepancy between the internal and external carbonation degrees.An increase in cement paste thickness simultaneously decreases the quantity,average size,and interconnectivity of macropores,lowering the diffusion efficacy of CO_(2) and moisture and exacerbating the overall heterogeneity in carbonation.Moreover,the gradual blockage of macropores leads to the emergence of localized ‘occluded zones’ with much lower carbonation degree.The reduction in aggregate size significantly alters the average diameter and connectivity of macropores,leading to notable change to overall non-uniformity.This study provides insight into improving the CO_(2) curing effect of pervious concrete products and developing uniform curing methods.
基金Project supported by the National Hi-Tech Research and Development Program (863) of China (No. 2002AA601022)
文摘The pollutant loads of surface runoff in an urban tourist area have been investigated for two years in the Wuhan City Zoo, China. Eight sampling sites, including two woodlands, three animal yards, two roofs and one road, were selected for sampling and study. The results indicate that pollutants ranked in a predictable order of decreasing load （e.g. animal yard〉roof〉woodland〉road）, with animal yards acting as the key pollution source in the zoo. Pollutants were transported mainly by particulate form in runoff. Particulate nitrogen and particulate phosphorous accounted on average for 61%, 78% of total pollutant, respectively, over 13 monitored rainfall events. These results indicate the treatment practices should be implemented to improve particulate nutrient removal. Analysis of the M（V） curve indicate that no first flush effect existed in the surface runoff from pervious areas （e.g. woodland, animal ground yard）, whereas a first flush effect was evident in runoff from impervious surfaces （e.g. animal cement yard, roof, road）.
基金Funded by the National Natural Science Foundation of China(No.51878081).
文摘A high strength self-compacting pervious concrete(SCPC) with top-bottom interconnected pores was prepared in this paper. The frost-resisting durability of such SCPC in different deicing salt concentrations(0%, 3%, 5%, 10%, and 20%) was investigated. The mass-loss rate, relative dynamic modulus of elasticity, compressive strength, flexural strength and hydraulic conductivity of SCPC after 300 freeze-thaw cycles were measured to evaluate the frost-resisting durability. In addition, the microstructures of SCPC near the top-bottom interconnected pores after 300 freeze-thaw cycles were observed by SEM. The results show that the high strength SCPC possesses much better frost-resisting durability than traditional pervious concrete(TPC) after 300 freeze-thaw cycles, which can be used in heavy loading roads. The most serious freeze-thaw damage emerges in the SCPC immersed in the 3% of Na Cl solution, while there is no obvious damage in 20% of Na Cl solution. Furthermore, it can be deduced that the high strength SCPC can be used for 100 years in a cold environment.
基金Project(kfj080205) supported by Key Laboratory of Road Structure and Material of Ministry of Transport of Changsha, China
文摘Surface textures had long been recognized as primary factors to provide the skid resistance on pavements; however, no measurement of skid resistance on pervious concrete pavement with various surface texture parameters had been made. Fractal geometry was introduced in the present work to accurately simulate transect contour curves of pervious concrete specimens through fractal interpolation. It is proved that its fractal dimension (D) can be adopted to measure the skid resistance on pervious concrete pavement, overcoming the shortcomings of both macrotexture depth (DT ) and British portable pendulum number (NBP). Combined with Fujikawa-Koike tire/road contact model, the optimization method of all surface textures was recommended for designing and constructing excellently skid-resistant and noise-absorptive pervious concrete pavement. In addition, evaluating of the abrasion process and attenuation of the surface textures on concrete pavement slabs was also the focus of this work based on accelerated abrasion test. Results show that the surface textures on pervious concrete pavement slabs is extremely durable, compared to those on conventional grooved or exposed aggregate concrete pavement slabs.
基金Projects(51978346,51778302)supported by the National Natural Science Foundation of ChinaProject(202002N3117)supported by the Ningbo Science and Technology Project,China。
文摘An improved design method of pervious concrete was proposed to lower the deviation between the designed and actual porosity and maintain both mechanical property and permeability of pervious concrete. The improved design method is mainly based on the optimal volume ratio of paste to aggregate(VRPA), which was determined by testing the average thickness of cement paste coating aggregate. The performances of pervious concrete designed by the traditional method and the improved one were compared. The results show that with the increase of designed porosity, the reduction of compressive strength and flexural strength of pervious concrete designed by the improved method is significantly smaller than those designed by the traditional one. The maximum deviation between the designed and actual porosity of the pervious concrete by the improved method is only 1.54%, which is far less than 8.7% obtained by the traditional one. Micro-structural analysis shows that the porous distribution of pervious concrete designed by improved method exhibits better uniformity.
基金Project(kfj080205)supported by Key Laboratory of Road Structure and Material of Ministry of Transport(Changsha),China
文摘Compressive and flexural strength,fracture energy,as well as fatigue property of pervious cement concrete with either supplementary cementitious materials (SCMs) or polymer intensified,were analyzed.Test results show that the strength development of SCM-modified pervious concrete (SPC) differs from that of polymer-intensified pervious concrete (PPC),and porosity has little effect on their strength growth.PPC has higher flexural strength and remarkably higher flexural-to-compressive strength ratio than SPC at the same porosity level.Results from fracture test of pervious concrete mixes with porosity around 19.5% show that the fracture energy increases with increasing the dosage of polymer,reflecting the ductile damage features rather than brittleness.PPC displays far longer fatigue life than SPC for any given failure probability and at any stress level.It is proved that two-parameter Weibull probability function describes the flexural fatigue of pervious concrete.
基金This study was funded by the National key research and development program fund project(No.2018YFC0406803).
文摘A recycled aggregate(RA)was prepared by crushing and sieving demolished discarded concrete pavements and was subsequently tested and analyzed to determine its various physical properties.On this basis,pervious concrete(PC)mix proportions were designed.Coarse RA particles with sizes of 5–10 and 10–20 mm were selected.Concrete specimens were prepared with a water–cement ratio of 0.3,an aggregate–cement ratio of 4.5,the substitute rates of RA with 0,25%,50%,75%and a single-/double-gap-graded RA mix(mass ratio of particles with sizes of 5–10 mm to particles with sizes of 10–20 mm:1:1,1:2,2:1,2:3 and 3:2).Various properties of the RA-containing PC(RPC)were determined by analyzing the compressive strength,splitting tensile strength,effective porosity,permeation coefficient and impact and abrasion resistance of the specimens.The results showed the following:The density of the RPC decreased with an increasing RA replacement ratio.The density of the RPC prepared with a double-gapgraded RA mix was lower than that prepared with a single-gap-graded RA(particle size:10–20 mm)mix.The permeation coefficient of the RPC increased with increasing porosity.The splitting tensile strength of the RPC was positively correlated with its compressive strength.The compressive strength of the RPC decreased with increasing porosity.The regression analysis showed that the impact and abrasion resistance of the RPC increased with increasing compressive strength.In addition,all of the RPC specimens met the strength and permeation requirements.This study can provide theoretical support for the application of RPC.
基金the“Qihang Plan”of China University of Mining and Technology.
文摘Pervious concrete(PC)is at risk of clogging due to the continuous blockage of sand into it during its service time.This study aims to evaluate and predict such clogging behavior of PC using hybrid machine learning techniques.Based on the 84 groups of the dataset developed in the earlier study,the clogging behavior of the PC was determined by the algorithm combing the SVM(support vector machines)and particle swarm optimization(PSO)methods.The PSO algorithm was employed to adjust the hyperparameters of the SVM and verify the performance using 10-fold cross-validation.The predicting results of the developed model were assessed by the coefficient of determination(R)and root mean square error(RMSE).The importance of the influential variables on the clogging behavior of PC was evaluated as well.The results showed that the PSO algorithm can effectively adjust the hyperparameters of the SVM model and can be used to construct the predictive model for the clogging behavior of the PC.The combined algorithm has the advantage of higher reliability and validity than the random hyperparameters selection.For the verification process,the developed model was able to obtain values of 0.9469 and 1.8148 for the R and RMSE,showing that the developed machine learning model can accurately be used to evaluate and predict the clogging behavior of the PC,guiding the mix-design of PC from the perspective of durability.The size of the clogging sand is the most important parameter and the thickness of the sample is the least significant factor affecting the clogging behavior.The proportions of the smallest aggregate size and largest aggregate size are the two most important design parameters of concrete with the consideration of the relatively higher importance scores,showing these two aggregates should be given special attention in future PC design for anti-clogging purposes.
基金Funded by the Opening Fund of the Key Laboratory of Silicate Material Science and Engineering,Ministry of Education(No.YSJJ2004-13)
文摘The effects of the proportion of fine aggregate, the maximum size of the aggregate and the proportion of the 9.5 mm to 4.75 mm particle in the coarse aggregate on the properties of the porous concrete are investigated. Results indicate that the porous concrete with a cement dosage only 150 kg/m^3 has high strength and satisfying permeability when the aggregate has a passing percentage of 4.75 mm around 10% to 15%, with the increase of the maximum size of the aggregate, the strength of the porous concrete decreases and the permeability increases. When the proportion of the 9.5 mm to 4.75 mm particle in the coarse aggregate is about 20%, there are no interference among the particles by Weymouth theory, the strength of the pervious porous concrete reaches the peak value. The optimum continues gradation limit of the aggregate for porous concrete pervious road base material is recommended according to the theoretical calculation and experimental results.
基金This work was supported by the National Natural Science Foundation of China(No.52009045)National Key Research and Development Program of China(No.2018YFC0406902).
文摘Pervious concrete is recommended,which is of great benefit to the ecological environment and human living environment.In this paper,the influences of five water-cement ratios and four fly ash contents to replace the cement by mass with a water-cement ratio of 0.30 on the properties of Recycled Aggregate Pervious Concrete(RAPC)were studied.Following this,based on the Grey relational-Technique for Order Preference by Similarity to an Ideal Solution(TOPSIS)optimization method,the strength,permeability,abrasion loss rate,and material costs of RAPC were adopted as evaluation indices to establish a mix proportion optimization model.The results show that the increase of water-cement ratio and fly ash replacement level of RAPC leads to decreased compres-sive strength while an increase in the permeability and abrasion loss rate.According to test results based on the optimal model 0.30 was identified as the best mix proportion.In addition,ecological-economic analysis of RAPC raw materials was carried out by comparing different natural aggregates.The results of EE(embodied energy)and ECO 2e(embodied CO_(2) emission)pointed out that the combination of recycled aggregate and fly ash leads to sig-nificant ecological and economic benefits.
文摘Many dangerous effects arise from seepage through earth dams based on pervious layer. Therefore, the dam embankment must be provided with seepage control measures to avoid such effects. In the present work, different control methods were used such as flat slopes, toe drainage systems, and a catch drain in the tail water. The hydraulic performance of each control measure was evaluated using the analytical solutions, previously developed, to estimate the seepage quantity (q), the height of seepage surface (h<sub>3</sub>), and the coordinates of the free surface (h<sub>x</sub>). Study was conducted on a physical model for a dam embankment having a top width (b) = 10.0 meter, height (H<sub>d</sub>) = 30.0 meter, and slope factor (m) = 1.5. The obtained results were analyzed and presented in dimensionless charts. Results showed that, the used control measures possess a great effect on the characteristics of seepage through earth dams based on pervious foundations. A comparative study was conducted between the studied toe drainage systems to enable the designers the better choice for design purposes.
文摘Employing Biot’s theory of wave propagation in liquid saturated porous media, waves propagating in a hollow poroelastic closed spherical shell filled with fluid are studied. The frequency equation of axially symmetric vibrations for a pervious and an impervious surface is obtained. Free vibrations of a closed spherical shell are studied as a particular case when the fluid is vanished. Frequency as a function of ratio of thickness to inner radius is computed in absence of dissipation for two types of poroelastic materials each for a pervious and an impervious surface. Results of previous works are obtained as a particular case of the present study.
文摘The goal of this study was to compare the predicted void content with the actual void content of pervious concrete cylinders. All pervious concrete systems are designed with a void content in mind to facilitate a specific permeability;however, due to variable placing techniques and inherent issues with the material, the actual in place void content often varies from designed. This study quantifies this difference and attempts to develop a correction factor, such that design values are more approximate to in place pervious concrete systems. The analysis included multiple mixtures with three design void contents (15%, 25%, 35%), two aggregate types (angular and rounded), and three different water-to-cement ratios (0.33, 0.37, 0.41). These samples were methodically designed to contain a desired void ratio, then casted in the laboratory, in which the compaction of each sample was controlled for consistency. Following casting, the in-place void content was determined using ASTM C1754 and compared to the predicted. The difference was then averaged to create a correction factor requiring more or less cement paste, which was used to redesign the mixtures. The new mixtures were then compared to the predicted void content. The results of this study show that initial designs can vary from 3% - 15% on average from initial designed void content and that a correction factor can be used to obtain within 3% on average of the target void ratios.
文摘Understanding the hydrologic budget is crucial in planning for community based water supply. The water budget includes rainfall intensity, groundwater recharge, interception, evapotranspiration, and surface runoff. The percentage of rain going to recharge groundwater, rivers, and lakes is very important from the standpoint of human water consumption and ecosystems service. The objective of this work is to determine the recharge potential of groundwater in the Mokonde Community, Southern Sierra Leone. The community is dependent on wells as the main source of domestic water supply. This research need was born out of the absence of available data to show the relationship between rainfall amounts and groundwater recharge in the study area. In this study we monitored groundwater in a well at the United Methodist Church (UMC) compound at Ngegba Street. Automatic water logging devices were deployed to take readings in water level fluctuations every 15 minutes. Monitoring continued throughout the hydrological year of Sierra Leone. A rain gauge was deployed at neighboring UMC Primary School, and daily rainfall records taken at 9:00 a.m. Our team members also deployed at the well on a daily basis to collect data on abstraction of water. The results revealed, through a 29-year rainfall data and the Specific Yield, that 1170 mm of rainfall (48%) was the maximum potential of rainfall that would make groundwater a convenient source of water supply in the area. This demand was higher with the recent 1-year rainfall data. Increase in settlement had likely led to reduction in pervious area, and hence more and more rainfall needed for recharge. The time it took for maximum recharge (4 weeks) was shorter than that for maximum discharge (28 - 30 weeks). Groundwater flowed southwards towards the Gbengitay stream, which drained into the Tia River. These results would inform first step in delineating the water balance in the study area. Future studies could include the quality aspect, stream/river flow, interception and evapotranspiration. These pieces of information are required to help informed decision for water security.
文摘A study evaluating the relationship between porosity and permeability coefficient for pervious concrete (PC) is presented. In addition, the effect of mixture design parameters particularly, water-to-cement ratio (W/C) and size of aggregate on the permeability coefficient of PC was investigated. The PC mixtures were made with 4 range of W/C and 2 range size of aggregate. PC mixes were made from each aggregate and were tested. The results showed that the W/C and aggregate size are key parameters which significantly affect the characteristic performance of PC. Permeability coefficient of coarse pervious concrete (CPC) is bigger than fine pervious concrete (FPC) and the porosity of CPC are bigger than porosity of FPC. A regression model (RM) along with analysis of variance (ANOVA) was conducted to study the significance of porosity distribution on permeability coefficient of PC. The statistical model developed in this study can facilitate prediction permeability coefficient of CPC and FPC as the sustainable pavements.
文摘The application of the concept of sponge city in engineering and construction can efficiently reduce the surface runoff and peak flow,prevent surface flooding,and purify rainwater,thus achieving the recycle of water resources.In this paper,ecological technologies including the permeable concrete floor,sunken green space,grassed swale,ecological tree pool,and catchment module were comprehensively used in the construction of ecological squares.It can be said that this paper has carried on the effective exploration and practice of ensuring the city's water ecological security,promoting the transition of the traditional concept of urbanization construction in China and the sustainable development of the modernization construction of urban clusters.
基金Funded by the National Natural Science Foundation of China (No. 51878081)Natural Science Foundation of Jiangsu Province (No. BK20220626)+1 种基金Changzhou Leading Innovative Talent Introduction and Cultivation Project (No. CQ20210085)Postgraduate Research and Practice Innovation Program of Jiangsu Province (No. KYCX21_2847)。
文摘High-strength pervious concrete(HSPC) with porosity ranging from 0.08% to 2.011% was prepared. The mechanical properties and rainstorm waterlogging resistance of HSPC were evaluated,and a design method of HSPC pore characteristics(porosity and pore diameter) based on the mechanical properties and rainstorm waterlogging resistance was proposed. The results showed that the reduction of effective cross-sectional area caused by artificial channels was the main factor affecting flexural strength but had limited influence on compressive strength. Compared with the concrete matrix without artificial channels,the compressive strength of HSPC with porosity of 2.011% decreased by 7.4%, while the flexural strength decreased by 48.3%. The permeability coefficient of HSPC can reach 16.35 mm/s even at low porosity(2.011%).HSPC can meet the requirements of no rainstorm waterlogging, even if exposed to 100-year rainstorms. When the mechanical properties and rainstorm waterlogging resistance are compromised, the recommended porosity ranges from 1.1% to 3.5%, and the recommended pore diameter ranges from 0.8 to 2.7 mm.
