This study introduces superabsorbent polymers(SAP)into recycled concrete and,through freeze-thaw cycle tests,unconfined compressive strength tests,and nuclear magnetic resonance(NMR)analysis,evaluates the freeze-thaw ...This study introduces superabsorbent polymers(SAP)into recycled concrete and,through freeze-thaw cycle tests,unconfined compressive strength tests,and nuclear magnetic resonance(NMR)analysis,evaluates the freeze-thaw resistance and durability of recycled concrete samples under varying freeze-thaw cycles.The results indicate that an appropriate addition of SAP significantly enhances the freeze-thaw resistance of recycled concrete.After 200 freeze-thaw cycles,the RS0.6 sample retained good surface integrity,demonstrating the best performance.Compared to NAC,its mass loss decreased by 1.16%,the relative dynamic modulus improved by 7.01%,and the compressive strength loss rate decreased by 5.41%.Additionally,T2 spectrum analysis revealed that adding SAP optimized the pore structure of recycled concrete and mitigated pore development during freeze-thaw cycles.As the number of freeze-thaw cycles increased,the RS0.3 and RS0.6 samples demonstrated superior frost resistance compared to NAC.However,an excessive amount of SAP increased pore expansion during subsequent freeze-thaw cycles,ultimately weakening frost resistance.展开更多
We investigated the effects of fly ash(FA)content on the mechanical properties of recycled aggregate concrete(RAC)and its regeneration potential under freeze and thaw(F-T)cycles.The physical properties of second-gener...We investigated the effects of fly ash(FA)content on the mechanical properties of recycled aggregate concrete(RAC)and its regeneration potential under freeze and thaw(F-T)cycles.The physical properties of second-generation recycled concrete aggregates(RCA)were used to analyze the regeneration potential of RAC after F-T cycles.Scanning electron microscopy was used to study the interfacial transition zone microstructure of RAC after F-T cycles.Results showed that adding 20%FA to RAC significantly enhanced its mechanical properties and frost resistance.Before the F-T cycles,the compressive strength of RAC with 20%FA reached 48.3 MPa,exceeding research strength target of 40 MPa.A majority of second-generation RCA with FA had been verified to attain class Ⅲ,which enabled their practical application in non-structural projects such as backfill trenches and road pavement.However,the second-generation RCA with 20%FA can achieve class Ⅱ,making it ideal for 40 MPa structural concrete.展开更多
Crushing waste coral concrete into recycled aggregates to create recycled coral aggregate concrete(RCAC)contributes to sustainable construction development on offshore islands and reefs.To investigate the impact of re...Crushing waste coral concrete into recycled aggregates to create recycled coral aggregate concrete(RCAC)contributes to sustainable construction development on offshore islands and reefs.To investigate the impact of recycled coral aggregate on concrete properties,this study performed a comprehensive analysis of the physical properties of recycled coral aggregate and the basic mechanical properties and microstructure of RCAC.The test results indicate that,compared to coral debris,the crushing index of recycled coral aggregate was reduced by 9.4%,while porosity decreased by 33.5%.Furthermore,RCAC retained the early strength characteristics of coral concrete,with compressive strength and flexural strength exhibiting a notable increase as the water-cement ratio decreased.Under identical conditions,the compressive strength and flexural strength of RCAC were 12.7% and 2.5% higher than coral concrete's,respectively,with porosity correspondingly reduced from 3.13% to 5.11%.This enhancement could be attributed to the new mortar filling the recycled coral aggregate.Scanning electron microscopy(SEM)analysis revealed three distinct interface transition zones within RCAC,with the‘new mortar-old mortar’interface identified as the weakest.The above findings provided a reference for the sustainable use of coral concrete in constructing offshore islands.展开更多
Traditional machine learning(ML)encounters the challenge of parameter adjustment when predicting the compressive strength of reclaimed concrete.To address this issue,we introduce two optimized hybrid models:the Bayesi...Traditional machine learning(ML)encounters the challenge of parameter adjustment when predicting the compressive strength of reclaimed concrete.To address this issue,we introduce two optimized hybrid models:the Bayesian optimization model(B-RF)and the optimal model(Stacking model).These models are applied to a data set comprising 438 observations with five input variables,with the aim of predicting the compressive strength of reclaimed concrete.Furthermore,we evaluate the performance of the optimized models in comparison to traditional machine learning models,such as support vector regression(SVR),decision tree(DT),and random forest(RF).The results reveal that the Stacking model exhibits superior predictive performance,with evaluation indices including R2=0.825,MAE=2.818 and MSE=14.265,surpassing the traditional models.Moreover,we also performed a characteristic importance analysis on the input variables,and we concluded that cement had the greatest influence on the compressive strength of reclaimed concrete,followed by water.Therefore,the Stacking model can be recommended as a compressive strength prediction tool to partially replace laboratory compressive strength testing,resulting in time and cost savings.展开更多
Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may ...Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.展开更多
The use of recycled concrete and oyster shells as partial cement and aggregate replacements is ongoing research to solve this multifaceted problem of concrete waste in the construction industry as well as waste from o...The use of recycled concrete and oyster shells as partial cement and aggregate replacements is ongoing research to solve this multifaceted problem of concrete waste in the construction industry as well as waste from oyster shell farming. However, there is a lack of evidence on the possibility of producing a fully recycled composite consisting of recycled concrete and oyster shell without the need for new cement and natural aggregates. In this study, recycled concrete powder (RCP) and oyster shell were used to produce a green composite. Separate ground and combined ground (separate ground and co-ground) RCP and oyster shells are used to determine the effects of grinding approaches on the mechanical and chemical properties of the composite. The composite samples were molded via press molding by applying 30 MPa of pressure for 10 minutes. The results revealed that the composite prepared via the combined ground approach presented the highest flexural strength compared to the separate ground and unground samples. The FTIR and XRD characterization results revealed no chemical or phase alterations in the raw materials or the resulting composites before and after grinding. SEM analysis revealed that combined grinding reduced the particles’ size and improved the dispersion of the mixture, thereby increasing the strength.展开更多
Exploring alternative aggregates or recycled aggregates to substitute traditional concrete aggregates,particularly sand aggregates,which are becoming more limited and must comply with environmental protection standard...Exploring alternative aggregates or recycled aggregates to substitute traditional concrete aggregates,particularly sand aggregates,which are becoming more limited and must comply with environmental protection standards,is essential.Research has explored various alternative materials to sand in concrete,including concrete from demolished buildings,and broken glass from projects,among others.Investigating the use of recycled broken glass to substitute sand aggregates and implementing this research in compression columns is crucial.This paper examines the compressive behavior of reinforced concrete columns that utilize recycled glass particles as a substitute for sand in concrete.The research findings establish the relationships:load and vertical displacement,load and deformation at the column head,mid-column,and column base;the formation and propagation of cracks in the column,while considering factors such as the percentage of recycled glass,the arrangement of stirrups,and the amount of load-bearing steel influencing the performance of square reinforced concrete columns under compression.The feasibility of using recycled glass as a substitute for sand in column structures subjected to compression has been demonstrated,with the ideal replacement content for sand aggregate in reinforced concrete columns in this study ranging from 0%to 10%.The column’s load-bearing ability dropped from 250 kN to 150 kN when 100%recycled glass was used instead of sand.This is a 40%drop,and cracks started to show up sooner.The research will support recycling broken glass instead of using sand in building,improving the environment and reducing natural sand use.展开更多
Aiming to solve the problem of large discharge and severe pollution of reactive dyeing wastewater for wool fabrics,peroxodisulfate(SPS)was used for the degradation and recycling of dyeing wastewater containing reactiv...Aiming to solve the problem of large discharge and severe pollution of reactive dyeing wastewater for wool fabrics,peroxodisulfate(SPS)was used for the degradation and recycling of dyeing wastewater containing reactive dye Lanasol Red CE.The process of degrading the reactive dye was determined by using the dye residual rate as the evaluation index.The feasibility of reactive dyeing of wool fabrics using recycled dyeing wastewater was confirmed by measuring the dye uptake,exhaustion and fixation rates,as well as color parameters and fastness of the dyed fabrics.The results showed that the appropriate conditions for degrading Lanasol Red CE were 0.2 g/L SPS,an initial pH value of 3 and 100℃for 30 min.Under these conditions,the dye degradation rate was as high as 93.14%.When the recycled dyeing wastewater was used for dyeing of wool fabrics,the exhaustion rate of Lanasol Red CE exceeded 99%,and the fixation rate was higher than that achieved by the conventional dyeing process.Under the same dyeing conditions,the recycled-dyed fabrics appeared darker.When the number of cycles was fewer than five,the effect on color fastness was not obvious.Although the color fastness to rubbing and washing of the fabrics dyed in the 10th cycle decreased by half a grade and 1 grade,respectively,compared to that of the fabrics dyed with the conventional dyeing process,they still met the production requirements.展开更多
One of the significant technological challenges in safeguarding electronic devices pertains to the modulation of electromagnetic(EM)wave jamming and the recycling of defensive shields.The synergistic effect of heterod...One of the significant technological challenges in safeguarding electronic devices pertains to the modulation of electromagnetic(EM)wave jamming and the recycling of defensive shields.The synergistic effect of heterodimensional materials can effectively enable the manipulation of EM waves by altering the nanostructure.Here we propose a novel approach for upcycling by-products of silver nanowires that can fabricate shape-tunable aerogels which enable the modulation of its interaction with microwaves by heterodimensional structure of byproducts.By-product heterodimensionality was used to design EM-wave-jamming-dissipation structures and therefore two typical tunable aerogel forms were studied.The first tunable form was aerogel film,which shielded EM interference(EMI shielding effectiveness(EMI SE)>89 dB)and the second tunable form was foam,which performed dual EM functions(SE>30 dB&reflective loss(RL)<-35 dB,effective absorption bandwidth(EAB)>6.7 GHz).We show that secondary recycled aerogels retain nearly all of their EM protection properties,making this type of closed-loop cycle an appealing option.Our findings pave the way for the development of adaptive EM functions with nanoscale regulation in a green and closed-loop cycle,and they shed light on the fundamental understanding of microwave interactions with heterodimensional structures.展开更多
The iron content is one of the most critical parameters affecting the microstructure and mechanical properties of recycled aluminum alloy.This study aimed to compare the microstructure and tensile properties of alloys...The iron content is one of the most critical parameters affecting the microstructure and mechanical properties of recycled aluminum alloy.This study aimed to compare the microstructure and tensile properties of alloys with varying iron content to ascertain the optimal iron content for formulating a recycled Al-Si-Mg aluminum alloy.Additionally,the effects of aging temperature and aging time on the microstructure and mechanical properties of recycled aluminum alloy were investigated.With increasing aging temperature and time,both tensile strength and yield strength are improved,while elongation is decreased.Specifically,when subject to a heat treatment consisting of a solution treatment at 535℃for 5 h followed by an aging treatment at 170℃for5.5 h,the newly designed recycled aluminum alloy achieves a tensile strength of 291 MPa and a yield strength of 238 MPa.These findings hold significant implications for the further development and broader application of recycled aluminum alloys.展开更多
Facing the high demand for faster and heavier freight trains in Australia,researchers and practitioners are endeavouring to develop more innovative and resilient ballasted tracks.In recent years,many studies have been...Facing the high demand for faster and heavier freight trains in Australia,researchers and practitioners are endeavouring to develop more innovative and resilient ballasted tracks.In recent years,many studies have been conducted by the researchers from Transport Research Centre at the University of Technology Sydney(TRC-UTS)to examine the feasibility of incorporating recycled tyre/rubber into rail tracks.This paper reviews three innovative applications using recycled rubber products such as(1)a synthetic energy-absorbing layer for railway subballast using a composite of rubber crumbs and mining byproducts,(2)using rubber intermixed ballast stratum to replace conventional ballast,and(3)installing recycled rubber mat to mitigate ballast degradation under the impact loading.Comprehensive laboratory and field tests as well as numerical modelling have been conducted to examine the performance of rail tracks incorporating these innovative inclusions.The laboratory and field test results and numerical modelling reveal that incorporating these rubber products could increase the energy-absorbing capacity of the track,and mitigate the ballast breakage and settlement significantly,hence increasing the track stability.The research outcomes will facilitate a better understanding of the performance of ballast tracks incorporating these resilient waste tyre materials while promoting more economical and environmentally sustainable tracks for greater passenger comfort and increased safety.展开更多
The cemented-gangue-fly-ash backfill(CGFB)prepared from coal-based solid waste materials commonly exhibits high brittleness,leading to an increased susceptibility to cracking.Uniaxial compressive strength(UCS),acousti...The cemented-gangue-fly-ash backfill(CGFB)prepared from coal-based solid waste materials commonly exhibits high brittleness,leading to an increased susceptibility to cracking.Uniaxial compressive strength(UCS),acoustic emission(AE),and scanning electron microscopy tests were conducted on CGFB samples with recycled steel fiber(RSF)contents of 0,0.5%,1.0%and 1.5%to assess the mechanical properties and damage evolution law of the CGFB.The research findings indicate that:1)When RSF contents were 0.5%,1%,and 1.5%,respectively,compared to samples without RSF,the UCS decreased by 3.86%,6.76%,and 15.59%,while toughness increased by 69%,98%,and 123%;2)The addition of RSFs reduced the post-peak stress energy activity and increased the fluctuations in the b-value;3)As the RSF dosage increased from 0 to 1.5%,the per unit dissipated strain energy increased from 5.84 to 21.51,and the post-peak released energy increased from 15.07 to 33.76,indicating that the external energy required for the CGFB sample to fail increased;4)The hydration products,such as C-S-H gel,ettringite,and micro-particle materials,were embedded in the damaged areas of the RSFs,increasing the frictional force at the interface between the RSF and CGFB matrix.The shape variability of the RSFs caused interlocking between the RSFs and the matrix.Both mechanisms strengthened the bridging effect of the RSFs in the CGFB,thereby improving the damage resistance capability of CGFB.The excellent damage resistance occurred at an RSF content of 0.5%;thus,this content is recommended for engineering applications.展开更多
The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully rep...The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully replace natural fine aggregates was investigated.The results indicated that a 50% FA content significantly increased the compressive strength of RFA-HDCC by 13.93%.However,a?further increase in FA content led to a drastic decrease.The increased fly ash content substantially reduced the flexural and tensile strength;however,it markedly increased the matrix strain capacity,resulting in a 53.73% increase in the peak strain when FA was raised to 70%.Regarding durability,the increase in FA content negatively affected the chloride ion permeability and carbonation resistance.However,the increase in FA content initially improved the frost resistance of RFA-HDCC,peaking at 50% FA and deteriorating at 60% and 70% FA content.展开更多
In order to realize the resource utilization of construction waste,industrial waste slag and silt,this paper used Portland cement,mineral waste residue and phosphogypsum composite to make cementing material(CMPS)with ...In order to realize the resource utilization of construction waste,industrial waste slag and silt,this paper used Portland cement,mineral waste residue and phosphogypsum composite to make cementing material(CMPS)with construction waste recycled aggregate to solidify silt.The mechanical properties of the solidified silt were analyzed by laboratory solidification test and microscopic examination respectively.In order to clarify the mineral composition,microscopic morphology and pore characteristics of the regenerated aggregate and CMPS solidified silt,X-ray diffractometer(XRD),scanning electron microscope(SEM),and nitrogen adsorption pore analyzer(NA)were used to further explore and analyze the regenerated aggregate and CMPS solidified silt effectively,and further reveal the internal mechanism of the regenerated aggregate and CMPS solidified silt effectively.The experimental results show that the strength of Portland cement-mineral waste residue phosphogypsum terpolymer system curing agent increases by 107.34%than that of single Port-land cement solidified silt at 56 d,and the strength of CMPS solidified silt increases by 25.68%under the action of recycled aggregate framework.The curing age and moisture content of the silt have a high correlation with the strength of the solidified silt.Therefore,the influence law of the above two influencing factors on its mechanical properties is further explored and the strength prediction is made.The microscopic test results show that,based on the hydration of Port-land cement and the pozzolans reaction of mineral waste residue,the solidified system has produced calcium silicate hydrate gel and ettringite crystals with gelatinous properties,which helps to fill the pores and form a denser structure.展开更多
Poly(lactic acid)(PLA),a bio-based polymer,is considered to be a sustainable alternative to conventional petroleum-based plastics.However,owing to its widespread use and relatively slow degradation rate in water,PLA s...Poly(lactic acid)(PLA),a bio-based polymer,is considered to be a sustainable alternative to conventional petroleum-based plastics.However,owing to its widespread use and relatively slow degradation rate in water,PLA still poses potential environmental pollution risks after being discarded.The efficient chemical recycling of PLA represents an attractive approach to addressing both resource reuse and environmental pollution challenges caused by its waste.Hydrolysis is the predominant method of industrial recycling.However,because PLA is insoluble in water,efficient heterogeneous hydrolysis requires high-temperature and high-pressure conditions.In this study,an efficient homogenous hydrolysis method capable of simultaneously dissolving PLA and calcium hydroxide(Ca(OH)_(2))was developed.Suitable solvents for this method were screened,and it was found that PLA hydrolysis using dioxane and 1,4,7,10,13-Pen-taoxacyclopentadecane as solvents achieved conversion rates of 93%and 90%,respectively,within 2 h at room temperature.Notably,the hydrolysis product,calcium lactate,precipitated as a solid from the solvent and therefore self-separated from the reaction solution.The solvent,acid/base conditions,water content,and depolymerization kinetics were investigated.Compared with previously reported hydrolysis methods,the enhanced efficiency observed in this study can be attributed to the concurrent solvation of PLA and Ca(OH)_(2),which maintains homogeneity throughout the reaction process.Additionally,this method facilitates closed-loop recycling of PLA and is compatible with the highly selective recovery of PLA from various types of PLA products.展开更多
This study meticulously examined the compaction and sulfate erosion resistance of cement-stabilized materials incorporating recycled brick-concrete aggregate (RBCA).To explore the effects of recycled brick aggregate (...This study meticulously examined the compaction and sulfate erosion resistance of cement-stabilized materials incorporating recycled brick-concrete aggregate (RBCA).To explore the effects of recycled brick aggregate (RBA) with varying particle sizes,three size ranges (4.75-9.5 mm,9.5-19 mm and 19-31.5 mm) were used to replace 20% of the corresponding particle sizes of recycled concrete aggregate (RCA) in cement-stabilized materials.The findings indicated that cement-stabilized materials utilizing RBA and RCA exhibited a lower maximum dry density and a higher optimum moisture content than natural aggregate cement-stabilized materials.The use of RBA with a particle size of 4.75-9.5 mm resulted in a lower maximum dry density and a higher optimum moisture content than 9.5-19 mm and 19-31.5 mm.Furthermore,the 7-day unconfined compressive strength of RBCA cement-stabilized materials with RBA of 4.75-9.5 mm demonstrated superior results compared to those with larger particle sizes.Regarding sulfate erosion resistance,the mass loss and unconfined compressive strength loss of the RBCA cement-stabilized materials at 56 days were highest for the 19-31.5 mm particle size of the RBA.In terms of compaction and sulfate resistance,it is recommended to use 4.75-19 mm RBA in RBCA cement-stabilized materials.展开更多
Accurately predicting the compressive strength of recycled aggregate concrete(RAC)incorporating supplementary cementitious materials(SCMs)remains a critical challenge due to the heterogeneous nature of recycled aggreg...Accurately predicting the compressive strength of recycled aggregate concrete(RAC)incorporating supplementary cementitious materials(SCMs)remains a critical challenge due to the heterogeneous nature of recycled aggregates(RA)and the complex interactions among multiple binder constituents.This study advances the field by developing the most extensive and rigorously preprocessed database to date,which comprises 1243 RAC mixtures containing silica fume,fly ash,and ground-granulated blast-furnace slag.A hybrid,domain-informed machine-learning framework was then proposed,coupling optimized Extreme Gradient Boosting(XGBost)with civil engineering expertise to capture the complex chemical and microstructural mechanisms that govern RAC performance.Systematic grid-search optimization(n_estimators=50,learning_rate=0.2,max_depth=7)produced superior predictive accuracy(training R^(2)=0.9923,testing R^(2)=0.937;MAE=2.378 MPa;RMSE=3.591 MPa),which outperformed Extra Trees,Light Gradient Boosting,and traditional regressors.Beyond prediction,model interpretability was achieved using Shapley additive explanations and partial dependence analyses,which revealed curing age as the dominant strength driver,while water-to-binder ratio and recycled aggregate water absorption exhibited strong negative influences.Three-dimensional interaction plots further demonstrated how optimal superplasticizer dosages reduce the strength loss associated with high recycled aggregate content.In summary,this work provides a novel,explainable,and data-driven framework that achieves high predictive accuracy with mechanistic transparency and offers a powerful,interpretable tool for the design and optimization of sustainable RAC mixtures.展开更多
In order to study the effects of the contents of used mortar recycled aggregate(OMRA)and brick recycled aggregate(BRA)on the deformation properties of recycled aggregate concrete(RAC),under uniaxial compression condit...In order to study the effects of the contents of used mortar recycled aggregate(OMRA)and brick recycled aggregate(BRA)on the deformation properties of recycled aggregate concrete(RAC),under uniaxial compression conditions,The RAC of OMRA(0%,5%,10%,and 15%)and BRA(0%,3%,6%,9%,12%,and 15%)were studied.The experimental results show that,under uniaxial compression,the interfacial relationships of RAC containing OMRA and BRA between different materials are more complex,and the failure mechanism is also more complex.The content of OMRA and BRA had significant influence on the deformation behavior of RAC.When the content of OMRA and BRA is high,it is difficult for existing formulas and models to accurately represent the actual value.In this study,the influence of OMRA and BRA content is taken into account,and the existing formulas for calculating concrete deformation are modified,so that these formulas can more accurately calculate the elastic modulus,peak strain and ultimate strain of recycled concrete.The stress-strain formula of Guo concrete fits the stress-strain curve of concrete very well.We modified the formula on the basis of Guo formula to make the formula more suitable for the stress-strain curve of recycled concrete containing old mortar and brick,and the theoretical model proposed has better fitting accuracy.The study provides a valuable reference for nonlinear analysis of recycled aggregate concrete structures under different proportions of OMRA and BRA.展开更多
To investigate the effect of recycled sand on the compressive properties of recycled coarse aggregate concrete with different strength grades,an experimental study on the stress-strain curve under uniaxial compression...To investigate the effect of recycled sand on the compressive properties of recycled coarse aggregate concrete with different strength grades,an experimental study on the stress-strain curve under uniaxial compression was conducted.The failure processes and modes of recycled sand concrete(RSC)were studied,and the peak stress,peak strain,elastic modulus,ultimate strain,and toughness of RSC with different strength grades were studied.The interfacial transition zone(ITZ)of RSC was studied using microhardness and SEM,and its failure mechanism was studied.The results indicate that the addition of recycled sand has a significant impact on the descending segment of the stress-strain curve for the same strength grade.Based on Chinese standards,the relationship between the parameters of the descending segment and the peak stress of RSC was determined.A constitutive relationship for the stress-strain behavior of RSC under uniaxial compression was proposed.The microhardness of the ITZ increases with the decrease in the water-binder ratio and first increases and then decreases with the replacement ratio.This is due to the gelation activity of recycled powder,which reacts with hydration products to fill pores.However,when the content of recycled powder is excessive,the alkaline environment that maintains the stability of the C-S-H gel is disrupted,leading to a decrease in microhardness.展开更多
Against the backdrop of intensifying global water scarcity,reclaimed water reuse has emerged as a critical strategy for ecological replenishment of landscape water bodies.However,its potential ecological risks remain ...Against the backdrop of intensifying global water scarcity,reclaimed water reuse has emerged as a critical strategy for ecological replenishment of landscape water bodies.However,its potential ecological risks remain underexplored.This study aims to establish a multidimensional ecological safety evaluation framework for reclaimed water replenishment systems and propose hierarchical risk prevention strategies.By integrating ecotoxicological assays(algae growth inhibition,Daphnia behavioral anomalies,zebrafish embryo toxicity),multimedia exposure modeling,and Monte Carlo probabilistic simulations,the risk contributions and spatial heterogeneity of typical pollutants are quantitatively analyzed.Results revealed that sulfamethoxazole(RQ=2.3)and diclofenac(RQ=1.8)posed high ecological risks,with their effects nonlinearly correlated with hydraulic retention time(HRT<3 days)and nutrient loading(TN>1.2 mg/L).A three-tier risk prevention system was developed based on the“source-pathway-receptor”framework:ozone-activated carbon pretreatment achieved 85%removal efficiency for pharmaceutical contaminants,ecological floating beds enhanced nitrogen and phosphorus retention by 40%-60%,and hydraulic regulation(flow velocity>0.1 m/s)effectively suppressed pathogen proliferation.The innovation of this study lies in establishing a chemical-biological-hydrological coupled risk quantification model for reclaimed water reuse scenarios.The hierarchical prevention standards have been incorporated into local reclaimed water management regulations,providing a scientific foundation and technical paradigm for sustainable landscape water replenishment.展开更多
基金Funded by the Science and Technology Program of Gansu Province(Nos.25JRRA497,23ZDFA017)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0950000)High-level Talent Funding of Kashi。
文摘This study introduces superabsorbent polymers(SAP)into recycled concrete and,through freeze-thaw cycle tests,unconfined compressive strength tests,and nuclear magnetic resonance(NMR)analysis,evaluates the freeze-thaw resistance and durability of recycled concrete samples under varying freeze-thaw cycles.The results indicate that an appropriate addition of SAP significantly enhances the freeze-thaw resistance of recycled concrete.After 200 freeze-thaw cycles,the RS0.6 sample retained good surface integrity,demonstrating the best performance.Compared to NAC,its mass loss decreased by 1.16%,the relative dynamic modulus improved by 7.01%,and the compressive strength loss rate decreased by 5.41%.Additionally,T2 spectrum analysis revealed that adding SAP optimized the pore structure of recycled concrete and mitigated pore development during freeze-thaw cycles.As the number of freeze-thaw cycles increased,the RS0.3 and RS0.6 samples demonstrated superior frost resistance compared to NAC.However,an excessive amount of SAP increased pore expansion during subsequent freeze-thaw cycles,ultimately weakening frost resistance.
基金Funded by the Natural Science Foundation of Jiangsu Province(No.BK20220626)the National Natural Science Foundation of China(No.52078068)+2 种基金Science and Technology Innovation Foundation of NIT(No.KCTD006)Jiangsu Marine Structure Service Performance Improvement Engineering Research CenterKey Laboratory of Jiangsu"Marine Floating Wind Power Technology and Equipment"。
文摘We investigated the effects of fly ash(FA)content on the mechanical properties of recycled aggregate concrete(RAC)and its regeneration potential under freeze and thaw(F-T)cycles.The physical properties of second-generation recycled concrete aggregates(RCA)were used to analyze the regeneration potential of RAC after F-T cycles.Scanning electron microscopy was used to study the interfacial transition zone microstructure of RAC after F-T cycles.Results showed that adding 20%FA to RAC significantly enhanced its mechanical properties and frost resistance.Before the F-T cycles,the compressive strength of RAC with 20%FA reached 48.3 MPa,exceeding research strength target of 40 MPa.A majority of second-generation RCA with FA had been verified to attain class Ⅲ,which enabled their practical application in non-structural projects such as backfill trenches and road pavement.However,the second-generation RCA with 20%FA can achieve class Ⅱ,making it ideal for 40 MPa structural concrete.
基金Funded by Natural Science Foundation of Guangxi(No.2025GXNSFBA069565)Guangxi Science and Technology Program(No.AD25069101)Guangxi Bagui Scholars Fund。
文摘Crushing waste coral concrete into recycled aggregates to create recycled coral aggregate concrete(RCAC)contributes to sustainable construction development on offshore islands and reefs.To investigate the impact of recycled coral aggregate on concrete properties,this study performed a comprehensive analysis of the physical properties of recycled coral aggregate and the basic mechanical properties and microstructure of RCAC.The test results indicate that,compared to coral debris,the crushing index of recycled coral aggregate was reduced by 9.4%,while porosity decreased by 33.5%.Furthermore,RCAC retained the early strength characteristics of coral concrete,with compressive strength and flexural strength exhibiting a notable increase as the water-cement ratio decreased.Under identical conditions,the compressive strength and flexural strength of RCAC were 12.7% and 2.5% higher than coral concrete's,respectively,with porosity correspondingly reduced from 3.13% to 5.11%.This enhancement could be attributed to the new mortar filling the recycled coral aggregate.Scanning electron microscopy(SEM)analysis revealed three distinct interface transition zones within RCAC,with the‘new mortar-old mortar’interface identified as the weakest.The above findings provided a reference for the sustainable use of coral concrete in constructing offshore islands.
基金Funded by China National Key Research and Development Program for Application and Verification of Typical Groundwater Contaminated Sites(No.2019YFC1804805)Shenyang Key Laboratory of Safety Evaluation and Disaster Prevention of Engineering Structures(No.S230184)the Funding Project of Northeast Geological S&T Innovation Center of China Geological Survey(No.QCJJ2023-39)。
文摘Traditional machine learning(ML)encounters the challenge of parameter adjustment when predicting the compressive strength of reclaimed concrete.To address this issue,we introduce two optimized hybrid models:the Bayesian optimization model(B-RF)and the optimal model(Stacking model).These models are applied to a data set comprising 438 observations with five input variables,with the aim of predicting the compressive strength of reclaimed concrete.Furthermore,we evaluate the performance of the optimized models in comparison to traditional machine learning models,such as support vector regression(SVR),decision tree(DT),and random forest(RF).The results reveal that the Stacking model exhibits superior predictive performance,with evaluation indices including R2=0.825,MAE=2.818 and MSE=14.265,surpassing the traditional models.Moreover,we also performed a characteristic importance analysis on the input variables,and we concluded that cement had the greatest influence on the compressive strength of reclaimed concrete,followed by water.Therefore,the Stacking model can be recommended as a compressive strength prediction tool to partially replace laboratory compressive strength testing,resulting in time and cost savings.
基金Project(2024JJ2073)supported by the Science Fund for Distinguished Young Scholars of Hunan Province,ChinaProjects(2023YFC3807205,2019YFC1904704)+4 种基金supported by the National Key R&D Program of ChinaProject(52178443)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0109)supported by Fundamental Research Funds for the Central Universities of Central South University,China。
文摘Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.
文摘The use of recycled concrete and oyster shells as partial cement and aggregate replacements is ongoing research to solve this multifaceted problem of concrete waste in the construction industry as well as waste from oyster shell farming. However, there is a lack of evidence on the possibility of producing a fully recycled composite consisting of recycled concrete and oyster shell without the need for new cement and natural aggregates. In this study, recycled concrete powder (RCP) and oyster shell were used to produce a green composite. Separate ground and combined ground (separate ground and co-ground) RCP and oyster shells are used to determine the effects of grinding approaches on the mechanical and chemical properties of the composite. The composite samples were molded via press molding by applying 30 MPa of pressure for 10 minutes. The results revealed that the composite prepared via the combined ground approach presented the highest flexural strength compared to the separate ground and unground samples. The FTIR and XRD characterization results revealed no chemical or phase alterations in the raw materials or the resulting composites before and after grinding. SEM analysis revealed that combined grinding reduced the particles’ size and improved the dispersion of the mixture, thereby increasing the strength.
文摘Exploring alternative aggregates or recycled aggregates to substitute traditional concrete aggregates,particularly sand aggregates,which are becoming more limited and must comply with environmental protection standards,is essential.Research has explored various alternative materials to sand in concrete,including concrete from demolished buildings,and broken glass from projects,among others.Investigating the use of recycled broken glass to substitute sand aggregates and implementing this research in compression columns is crucial.This paper examines the compressive behavior of reinforced concrete columns that utilize recycled glass particles as a substitute for sand in concrete.The research findings establish the relationships:load and vertical displacement,load and deformation at the column head,mid-column,and column base;the formation and propagation of cracks in the column,while considering factors such as the percentage of recycled glass,the arrangement of stirrups,and the amount of load-bearing steel influencing the performance of square reinforced concrete columns under compression.The feasibility of using recycled glass as a substitute for sand in column structures subjected to compression has been demonstrated,with the ideal replacement content for sand aggregate in reinforced concrete columns in this study ranging from 0%to 10%.The column’s load-bearing ability dropped from 250 kN to 150 kN when 100%recycled glass was used instead of sand.This is a 40%drop,and cracks started to show up sooner.The research will support recycling broken glass instead of using sand in building,improving the environment and reducing natural sand use.
基金Youth Foundation of Hebei Province Department of Education Fund,China(No.QN2023090)Opening Project of Textile Ecological Dyeing and Finishing Key Laboratory of Sichuan Province(Chengdu Textile College),China(No.2024DF-AO2)Innovation and Entrepreneurship Training Program for College Students,China(No.202410082023)。
文摘Aiming to solve the problem of large discharge and severe pollution of reactive dyeing wastewater for wool fabrics,peroxodisulfate(SPS)was used for the degradation and recycling of dyeing wastewater containing reactive dye Lanasol Red CE.The process of degrading the reactive dye was determined by using the dye residual rate as the evaluation index.The feasibility of reactive dyeing of wool fabrics using recycled dyeing wastewater was confirmed by measuring the dye uptake,exhaustion and fixation rates,as well as color parameters and fastness of the dyed fabrics.The results showed that the appropriate conditions for degrading Lanasol Red CE were 0.2 g/L SPS,an initial pH value of 3 and 100℃for 30 min.Under these conditions,the dye degradation rate was as high as 93.14%.When the recycled dyeing wastewater was used for dyeing of wool fabrics,the exhaustion rate of Lanasol Red CE exceeded 99%,and the fixation rate was higher than that achieved by the conventional dyeing process.Under the same dyeing conditions,the recycled-dyed fabrics appeared darker.When the number of cycles was fewer than five,the effect on color fastness was not obvious.Although the color fastness to rubbing and washing of the fabrics dyed in the 10th cycle decreased by half a grade and 1 grade,respectively,compared to that of the fabrics dyed with the conventional dyeing process,they still met the production requirements.
基金supported by the National Key Research and Development Program of China(Grant 2021YFA0715600,2021YFA0717700,2018YFB2202900)National Natural Science Foundation of China(52192610,62274127,62374128)+5 种基金the Fundamental Research Funds for the Central Universities,2023 Qinchuangyuan Construction Two Chain Integration Special Project(23LLRH0043)Key Research and Development Program of Shaanxi Province(Grant 2024GX-YBXM-512)Foundation of Zhejiang Provincial Key Lab of Solar Energy Utilization&Energy Saving Technology(ZJS-OP-2020-11)GuangDong Basic and Applied Basic Research Foundation(Grant 2022A1515111220)the fund of the state Key Laboratory of Solidification Processing in NPU(Grant No.SKLSP202317)Young Elite Scientists Sponsorship Program by CAST,Doctoral Student Special Plan.
文摘One of the significant technological challenges in safeguarding electronic devices pertains to the modulation of electromagnetic(EM)wave jamming and the recycling of defensive shields.The synergistic effect of heterodimensional materials can effectively enable the manipulation of EM waves by altering the nanostructure.Here we propose a novel approach for upcycling by-products of silver nanowires that can fabricate shape-tunable aerogels which enable the modulation of its interaction with microwaves by heterodimensional structure of byproducts.By-product heterodimensionality was used to design EM-wave-jamming-dissipation structures and therefore two typical tunable aerogel forms were studied.The first tunable form was aerogel film,which shielded EM interference(EMI shielding effectiveness(EMI SE)>89 dB)and the second tunable form was foam,which performed dual EM functions(SE>30 dB&reflective loss(RL)<-35 dB,effective absorption bandwidth(EAB)>6.7 GHz).We show that secondary recycled aerogels retain nearly all of their EM protection properties,making this type of closed-loop cycle an appealing option.Our findings pave the way for the development of adaptive EM functions with nanoscale regulation in a green and closed-loop cycle,and they shed light on the fundamental understanding of microwave interactions with heterodimensional structures.
基金support from funded project:Key Industrial R&D Projects of Chongqing Technology Innovation and Application Demonstration (cstc2020jscx-dxwtBX0023)。
文摘The iron content is one of the most critical parameters affecting the microstructure and mechanical properties of recycled aluminum alloy.This study aimed to compare the microstructure and tensile properties of alloys with varying iron content to ascertain the optimal iron content for formulating a recycled Al-Si-Mg aluminum alloy.Additionally,the effects of aging temperature and aging time on the microstructure and mechanical properties of recycled aluminum alloy were investigated.With increasing aging temperature and time,both tensile strength and yield strength are improved,while elongation is decreased.Specifically,when subject to a heat treatment consisting of a solution treatment at 535℃for 5 h followed by an aging treatment at 170℃for5.5 h,the newly designed recycled aluminum alloy achieves a tensile strength of 291 MPa and a yield strength of 238 MPa.These findings hold significant implications for the further development and broader application of recycled aluminum alloys.
基金financial support from the Australian Research Council for ARCLP200200915 and ARCDP220102862financial and technical support from industry partners including Sydney Trains,SMEC Australia Pty.
文摘Facing the high demand for faster and heavier freight trains in Australia,researchers and practitioners are endeavouring to develop more innovative and resilient ballasted tracks.In recent years,many studies have been conducted by the researchers from Transport Research Centre at the University of Technology Sydney(TRC-UTS)to examine the feasibility of incorporating recycled tyre/rubber into rail tracks.This paper reviews three innovative applications using recycled rubber products such as(1)a synthetic energy-absorbing layer for railway subballast using a composite of rubber crumbs and mining byproducts,(2)using rubber intermixed ballast stratum to replace conventional ballast,and(3)installing recycled rubber mat to mitigate ballast degradation under the impact loading.Comprehensive laboratory and field tests as well as numerical modelling have been conducted to examine the performance of rail tracks incorporating these innovative inclusions.The laboratory and field test results and numerical modelling reveal that incorporating these rubber products could increase the energy-absorbing capacity of the track,and mitigate the ballast breakage and settlement significantly,hence increasing the track stability.The research outcomes will facilitate a better understanding of the performance of ballast tracks incorporating these resilient waste tyre materials while promoting more economical and environmentally sustainable tracks for greater passenger comfort and increased safety.
基金Projects(52274143,51874284)supported by the National Natural Science Foundation of China。
文摘The cemented-gangue-fly-ash backfill(CGFB)prepared from coal-based solid waste materials commonly exhibits high brittleness,leading to an increased susceptibility to cracking.Uniaxial compressive strength(UCS),acoustic emission(AE),and scanning electron microscopy tests were conducted on CGFB samples with recycled steel fiber(RSF)contents of 0,0.5%,1.0%and 1.5%to assess the mechanical properties and damage evolution law of the CGFB.The research findings indicate that:1)When RSF contents were 0.5%,1%,and 1.5%,respectively,compared to samples without RSF,the UCS decreased by 3.86%,6.76%,and 15.59%,while toughness increased by 69%,98%,and 123%;2)The addition of RSFs reduced the post-peak stress energy activity and increased the fluctuations in the b-value;3)As the RSF dosage increased from 0 to 1.5%,the per unit dissipated strain energy increased from 5.84 to 21.51,and the post-peak released energy increased from 15.07 to 33.76,indicating that the external energy required for the CGFB sample to fail increased;4)The hydration products,such as C-S-H gel,ettringite,and micro-particle materials,were embedded in the damaged areas of the RSFs,increasing the frictional force at the interface between the RSF and CGFB matrix.The shape variability of the RSFs caused interlocking between the RSFs and the matrix.Both mechanisms strengthened the bridging effect of the RSFs in the CGFB,thereby improving the damage resistance capability of CGFB.The excellent damage resistance occurred at an RSF content of 0.5%;thus,this content is recommended for engineering applications.
基金Funded by the Natural Science Foundation of Jiangsu Province(No.BK20220626)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX24_3174)Taizhou Science and Technology Support Programme(Social Development)Directive Project(No.TS202432)。
文摘The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully replace natural fine aggregates was investigated.The results indicated that a 50% FA content significantly increased the compressive strength of RFA-HDCC by 13.93%.However,a?further increase in FA content led to a drastic decrease.The increased fly ash content substantially reduced the flexural and tensile strength;however,it markedly increased the matrix strain capacity,resulting in a 53.73% increase in the peak strain when FA was raised to 70%.Regarding durability,the increase in FA content negatively affected the chloride ion permeability and carbonation resistance.However,the increase in FA content initially improved the frost resistance of RFA-HDCC,peaking at 50% FA and deteriorating at 60% and 70% FA content.
基金Funded by the Jiangsu Province Industry University Research Project(No.BY20231142)the Yangzhou Science&Technology Program(No.YZ2023061)the Zhenjiang Science&Technology Program(No.SH2022018)。
文摘In order to realize the resource utilization of construction waste,industrial waste slag and silt,this paper used Portland cement,mineral waste residue and phosphogypsum composite to make cementing material(CMPS)with construction waste recycled aggregate to solidify silt.The mechanical properties of the solidified silt were analyzed by laboratory solidification test and microscopic examination respectively.In order to clarify the mineral composition,microscopic morphology and pore characteristics of the regenerated aggregate and CMPS solidified silt,X-ray diffractometer(XRD),scanning electron microscope(SEM),and nitrogen adsorption pore analyzer(NA)were used to further explore and analyze the regenerated aggregate and CMPS solidified silt effectively,and further reveal the internal mechanism of the regenerated aggregate and CMPS solidified silt effectively.The experimental results show that the strength of Portland cement-mineral waste residue phosphogypsum terpolymer system curing agent increases by 107.34%than that of single Port-land cement solidified silt at 56 d,and the strength of CMPS solidified silt increases by 25.68%under the action of recycled aggregate framework.The curing age and moisture content of the silt have a high correlation with the strength of the solidified silt.Therefore,the influence law of the above two influencing factors on its mechanical properties is further explored and the strength prediction is made.The microscopic test results show that,based on the hydration of Port-land cement and the pozzolans reaction of mineral waste residue,the solidified system has produced calcium silicate hydrate gel and ettringite crystals with gelatinous properties,which helps to fill the pores and form a denser structure.
基金financially supported by the National Key R&D Program of China(No.2021YFB3801901)the National Natural Science Foundation of China(No.22075188 and U19A2095)supported by State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology。
文摘Poly(lactic acid)(PLA),a bio-based polymer,is considered to be a sustainable alternative to conventional petroleum-based plastics.However,owing to its widespread use and relatively slow degradation rate in water,PLA still poses potential environmental pollution risks after being discarded.The efficient chemical recycling of PLA represents an attractive approach to addressing both resource reuse and environmental pollution challenges caused by its waste.Hydrolysis is the predominant method of industrial recycling.However,because PLA is insoluble in water,efficient heterogeneous hydrolysis requires high-temperature and high-pressure conditions.In this study,an efficient homogenous hydrolysis method capable of simultaneously dissolving PLA and calcium hydroxide(Ca(OH)_(2))was developed.Suitable solvents for this method were screened,and it was found that PLA hydrolysis using dioxane and 1,4,7,10,13-Pen-taoxacyclopentadecane as solvents achieved conversion rates of 93%and 90%,respectively,within 2 h at room temperature.Notably,the hydrolysis product,calcium lactate,precipitated as a solid from the solvent and therefore self-separated from the reaction solution.The solvent,acid/base conditions,water content,and depolymerization kinetics were investigated.Compared with previously reported hydrolysis methods,the enhanced efficiency observed in this study can be attributed to the concurrent solvation of PLA and Ca(OH)_(2),which maintains homogeneity throughout the reaction process.Additionally,this method facilitates closed-loop recycling of PLA and is compatible with the highly selective recovery of PLA from various types of PLA products.
基金Funded by the National Natural Science Foundation of China (No.52078068)the Natural Science Foundation of Jiangsu Province (No.BK20220626)。
文摘This study meticulously examined the compaction and sulfate erosion resistance of cement-stabilized materials incorporating recycled brick-concrete aggregate (RBCA).To explore the effects of recycled brick aggregate (RBA) with varying particle sizes,three size ranges (4.75-9.5 mm,9.5-19 mm and 19-31.5 mm) were used to replace 20% of the corresponding particle sizes of recycled concrete aggregate (RCA) in cement-stabilized materials.The findings indicated that cement-stabilized materials utilizing RBA and RCA exhibited a lower maximum dry density and a higher optimum moisture content than natural aggregate cement-stabilized materials.The use of RBA with a particle size of 4.75-9.5 mm resulted in a lower maximum dry density and a higher optimum moisture content than 9.5-19 mm and 19-31.5 mm.Furthermore,the 7-day unconfined compressive strength of RBCA cement-stabilized materials with RBA of 4.75-9.5 mm demonstrated superior results compared to those with larger particle sizes.Regarding sulfate erosion resistance,the mass loss and unconfined compressive strength loss of the RBCA cement-stabilized materials at 56 days were highest for the 19-31.5 mm particle size of the RBA.In terms of compaction and sulfate resistance,it is recommended to use 4.75-19 mm RBA in RBCA cement-stabilized materials.
基金supported by the Ongoing Research Funding Program(Grant No.ORFT-2025-025-6)at King Saud University,Riyadh,Saudi Arabia.
文摘Accurately predicting the compressive strength of recycled aggregate concrete(RAC)incorporating supplementary cementitious materials(SCMs)remains a critical challenge due to the heterogeneous nature of recycled aggregates(RA)and the complex interactions among multiple binder constituents.This study advances the field by developing the most extensive and rigorously preprocessed database to date,which comprises 1243 RAC mixtures containing silica fume,fly ash,and ground-granulated blast-furnace slag.A hybrid,domain-informed machine-learning framework was then proposed,coupling optimized Extreme Gradient Boosting(XGBost)with civil engineering expertise to capture the complex chemical and microstructural mechanisms that govern RAC performance.Systematic grid-search optimization(n_estimators=50,learning_rate=0.2,max_depth=7)produced superior predictive accuracy(training R^(2)=0.9923,testing R^(2)=0.937;MAE=2.378 MPa;RMSE=3.591 MPa),which outperformed Extra Trees,Light Gradient Boosting,and traditional regressors.Beyond prediction,model interpretability was achieved using Shapley additive explanations and partial dependence analyses,which revealed curing age as the dominant strength driver,while water-to-binder ratio and recycled aggregate water absorption exhibited strong negative influences.Three-dimensional interaction plots further demonstrated how optimal superplasticizer dosages reduce the strength loss associated with high recycled aggregate content.In summary,this work provides a novel,explainable,and data-driven framework that achieves high predictive accuracy with mechanistic transparency and offers a powerful,interpretable tool for the design and optimization of sustainable RAC mixtures.
基金Funded by the Project of National Key Research and Development Program of China(No.2019YFC1906202)。
文摘In order to study the effects of the contents of used mortar recycled aggregate(OMRA)and brick recycled aggregate(BRA)on the deformation properties of recycled aggregate concrete(RAC),under uniaxial compression conditions,The RAC of OMRA(0%,5%,10%,and 15%)and BRA(0%,3%,6%,9%,12%,and 15%)were studied.The experimental results show that,under uniaxial compression,the interfacial relationships of RAC containing OMRA and BRA between different materials are more complex,and the failure mechanism is also more complex.The content of OMRA and BRA had significant influence on the deformation behavior of RAC.When the content of OMRA and BRA is high,it is difficult for existing formulas and models to accurately represent the actual value.In this study,the influence of OMRA and BRA content is taken into account,and the existing formulas for calculating concrete deformation are modified,so that these formulas can more accurately calculate the elastic modulus,peak strain and ultimate strain of recycled concrete.The stress-strain formula of Guo concrete fits the stress-strain curve of concrete very well.We modified the formula on the basis of Guo formula to make the formula more suitable for the stress-strain curve of recycled concrete containing old mortar and brick,and the theoretical model proposed has better fitting accuracy.The study provides a valuable reference for nonlinear analysis of recycled aggregate concrete structures under different proportions of OMRA and BRA.
基金Funded by National Key Research and Development Program of China(No.2020YFC1909905)Science and Technology Research and Development Plan of China National Railway Group Co.+2 种基金Ltd.(No.L2022G009)National Natural Science Foundation of China High-speed Rail Joint Fund(No.U1934206)New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘To investigate the effect of recycled sand on the compressive properties of recycled coarse aggregate concrete with different strength grades,an experimental study on the stress-strain curve under uniaxial compression was conducted.The failure processes and modes of recycled sand concrete(RSC)were studied,and the peak stress,peak strain,elastic modulus,ultimate strain,and toughness of RSC with different strength grades were studied.The interfacial transition zone(ITZ)of RSC was studied using microhardness and SEM,and its failure mechanism was studied.The results indicate that the addition of recycled sand has a significant impact on the descending segment of the stress-strain curve for the same strength grade.Based on Chinese standards,the relationship between the parameters of the descending segment and the peak stress of RSC was determined.A constitutive relationship for the stress-strain behavior of RSC under uniaxial compression was proposed.The microhardness of the ITZ increases with the decrease in the water-binder ratio and first increases and then decreases with the replacement ratio.This is due to the gelation activity of recycled powder,which reacts with hydration products to fill pores.However,when the content of recycled powder is excessive,the alkaline environment that maintains the stability of the C-S-H gel is disrupted,leading to a decrease in microhardness.
文摘Against the backdrop of intensifying global water scarcity,reclaimed water reuse has emerged as a critical strategy for ecological replenishment of landscape water bodies.However,its potential ecological risks remain underexplored.This study aims to establish a multidimensional ecological safety evaluation framework for reclaimed water replenishment systems and propose hierarchical risk prevention strategies.By integrating ecotoxicological assays(algae growth inhibition,Daphnia behavioral anomalies,zebrafish embryo toxicity),multimedia exposure modeling,and Monte Carlo probabilistic simulations,the risk contributions and spatial heterogeneity of typical pollutants are quantitatively analyzed.Results revealed that sulfamethoxazole(RQ=2.3)and diclofenac(RQ=1.8)posed high ecological risks,with their effects nonlinearly correlated with hydraulic retention time(HRT<3 days)and nutrient loading(TN>1.2 mg/L).A three-tier risk prevention system was developed based on the“source-pathway-receptor”framework:ozone-activated carbon pretreatment achieved 85%removal efficiency for pharmaceutical contaminants,ecological floating beds enhanced nitrogen and phosphorus retention by 40%-60%,and hydraulic regulation(flow velocity>0.1 m/s)effectively suppressed pathogen proliferation.The innovation of this study lies in establishing a chemical-biological-hydrological coupled risk quantification model for reclaimed water reuse scenarios.The hierarchical prevention standards have been incorporated into local reclaimed water management regulations,providing a scientific foundation and technical paradigm for sustainable landscape water replenishment.
