This study investigates the performance enhancement of super-sulfated cement(SSC)derived from arsenic-containing bio-oxidation waste(BW)through the incorporation of carbonated recycled concrete fines(CRCF).The finding...This study investigates the performance enhancement of super-sulfated cement(SSC)derived from arsenic-containing bio-oxidation waste(BW)through the incorporation of carbonated recycled concrete fines(CRCF).The findings revealed that the addition of 5wt%CRCF yields optimal performance,with compressive strengths reaching approximately 1.83,12.59,and 42.81 MPa at 1,3,and 28 d,respectively.These values represented significant increases of 408.3%,10.0%,and 14.3%compared to the reference sample.The improvement was attributed to the synergistic effects of ultrafine CRCF particles acting as fillers and nucleation sites,as well as the high reactivity of silica gels,which promoted the formation of additional hydration gels.Microstructural analysis confirmed that CRCF addition refined pore structure,and enhanced the stiffness of C-S-H gels.Furthermore,CRCF served as a net CO_(2) sink,sequestering 0.268 kg CO_(2) per kilogram of CRCF and thereby reducing the carbon footprint of SSC.In addition,the feasibility of applying CRCF-modified SSC in cemented paste backfill(CPB)is highlighted,given the high cement-related carbon footprint of conventional CPB.When 5wt%CRCFmodified SSC was employed in CPB,its 3-d compressive strength attained over 70%of that of ordinary Portland cement(OPC),while the 28-d strength was comparable to that of OPC.The proposed binder thus provides a sustainable pathway for BW valorization,combining waste utilization,carbon sequestration,and improved engineering performance.展开更多
In coal mining on a high-pressure Ordovician limestone aquifer,grouting materials should have sufficient mechanical properties,particularly strong interfacial bonding performance to address stress concentration at the...In coal mining on a high-pressure Ordovician limestone aquifer,grouting materials should have sufficient mechanical properties,particularly strong interfacial bonding performance to address stress concentration at the grout-limestone interface induced by rock stress disturbances during mining.In this study,graphene oxide(GO)was integrated into cement-polyacrylate composite grout to improve its interfacial bonding.First,four-point bending tests were conducted,and the Monte Carlo method combined with the simplex search algorithm was employed to determine the variations in shear cohesion and static friction parameters.The results reveal that GO can significantly increase both the tensile and shear cohesion of the grout-limestone interface,but minimally affects the interfacial friction coefficient.Second,nuclear magnetic resonance(NMR)and scanning electron microscopy(SEM)tests were performed.The results indicate that GO nanosheets result in a squamaceous microstructure of the grout consolidation mass,increasing the adhesion of the grout-limestone interface.Moreover,spiny Aft(ettringite)clusters can be induced in limestone fracture surfaces by GO,which could serve as anchors for limestone and grout consolidation mass.展开更多
Improving energy efficiency and lowering negative environmental impact through waste heat recovery(WHR)is a critical step toward sustainable cement manufacturing.This study analyzes advanced cogeneration systems for r...Improving energy efficiency and lowering negative environmental impact through waste heat recovery(WHR)is a critical step toward sustainable cement manufacturing.This study analyzes advanced cogeneration systems for recovering waste heat from the Fallujah White Cement Plant in Iraq.The novelty of this work lies in its direct application and comparative thermodynamic analysis of three distinct cogeneration cycles—the Organic Rankine Cycle,the Single-Flash Steam Cycle,and the Dual-Pressure Steam Cycle—within the Iraqi cement industry,a context that has not been widely studied.The main objective is to evaluate and compare these models to determine the most effective approach for enhancing energy and exergy efficiencies.Themethodology involved detailed thermodynamic and exergy analyses of each system,supported by mathematical modelling and simulation using data from plant operations.The results reveal that the Dual-Pressure Steam Cycle emerged as the most effective system,delivering 13.76 MW of net power with a thermal efficiency of 32.8%and an exergy efficiency of 51%.This significantly outperformed the baseline Organic Rankine Cycle(8.18MW,18.8%thermal efficiency,30.7%exergy efficiency).These findings confirm that multipressure steam cycles offer a robust and practical solution for the Fallujah plant.This application provides a clear,high-impact pathway to enhance national industrial energy efficiency,significantly reduce CO_(2) emissions,and promote clean energy sustainability in Iraq.Future work should consider economic feasibility and potential integration with renewable energy sources to further enhance sustainability.展开更多
Cement stands as a dominant contributor to global energy consumption and carbon emissions in the construction industry.With the upgrading of infrastructure and the improvement of building standards,traditional cement ...Cement stands as a dominant contributor to global energy consumption and carbon emissions in the construction industry.With the upgrading of infrastructure and the improvement of building standards,traditional cement fails to reconcile ecological responsibility with advanced functional performance.By incorporating tailored fillers into cement matrices,the resulting composites achieve enhanced thermoelectric(TE)conversion capabilities.These materials can harness solar radiation from building envelopes and recover waste heat from indoor thermal gradients,facilitating bidirectional energy conversion.This review offers a comprehensive and timely overview of cementbased thermoelectric materials(CTEMs),integrating material design,device fabrication,and diverse applications into a holistic perspective.It summarizes recent advancements in TE performance enhancement,encompassing fillers optimization and matrices innovation.Additionally,the review consolidates fabrication strategies and performance evaluations of cement-based thermoelectric devices(CTEDs),providing detailed discussions on their roles in monitoring and protection,energy harvesting,and smart building.We also address sustainability,durability,and lifecycle considerations of CTEMs,which are essential for real-world deployment.Finally,we outline future research directions in materials design,device engineering,and scalable manufacturing to foster the practical application of CTEMs in sustainable and intelligent infrastructure.展开更多
The development of metallic mineral resources generates a significant amount of solid waste,such as tailings and waste rock.Cemented tailings and waste-rock backfill(CTWB)is an effective method for managing and dispos...The development of metallic mineral resources generates a significant amount of solid waste,such as tailings and waste rock.Cemented tailings and waste-rock backfill(CTWB)is an effective method for managing and disposing of this mining waste.This study employs a macro-meso-micro testing method to investigate the effects of the waste rock grading index(WGI)and loading rate(LR)on the uniaxial compressive strength(UCS),pore structure,and micromorphology of CTWB materials.Pore structures were analyzed using scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP).The particles(pores)and cracks analysis system(PCAS)software was used to quantitatively characterize the multi-scale micropores in the SEM images.The key findings indicate that the macroscopic results(UCS)of CTWB materials correspond to the microscopic results(pore structure and micromorphology).Changes in porosity largely depend on the conditions of waste rock grading index and loading rate.The inclusion of waste rock initially increases and then decreases the UCS,while porosity first decreases and then increases,with a critical waste rock grading index of 0.6.As the loading rate increases,UCS initially rises and then falls,while porosity gradually increases.Based on MIP and SEM results,at waste rock grading index 0.6,the most probable pore diameters,total pore area(TPA),pore number(PN),maximum pore area(MPA),and area probability distribution index(APDI)are minimized,while average pore form factor(APF)and fractal dimension of pore porosity distribution(FDPD)are maximized,indicating the most compact pore structure.At a loading rate of 12.0 mm/min,the most probable pore diameters,TPA,PN,MPA,APF,and APDI reach their maximum values,while FDPD reaches its minimum value.Finally,the mechanism of CTWB materials during compression is analyzed,based on the quantitative results of UCS and porosity.The research findings play a crucial role in ensuring the successful application of CTWB materials in deep metal mines.展开更多
Cemented paste backfill(CPB)is a technology that achieves safe mining by filling the goaf with waste rocks,tailings,and other materials.It is an inevitable choice to deal with the development of deep and highly diffic...Cemented paste backfill(CPB)is a technology that achieves safe mining by filling the goaf with waste rocks,tailings,and other materials.It is an inevitable choice to deal with the development of deep and highly difficult mines and meet the requirements of environmental protection and safety regulations.It promotes the development of a circular economy in mines through the development of lowgrade resources and the resource utilization of waste,and extends the service life of mines.The mass concentration of solid content(abbreviated as“concentration”)is a critical parameter for CPB.However,discrepancies often arise between the on-site measurements and the pre-designed values due to factors such as groundwater inflow and segregation within the goaf,which cannot be evaluated after the solidification of CPB.This paper innovatively provides an in-situ non-destructive approach to identify the real concentration of CPB after curing for certain days using hyperspectral imaging(HSI)technology.Initially,the spectral variation patterns under different concentration conditions were investigated through hyperspectral scanning experiments on CPB samples.The results demonstrate that as the CPB concentration increases from 61wt%to 73wt%,the overall spectral reflectance gradually increases,with two distinct absorption peaks observed at 1407 and 1917 nm.Notably,the reflectance at 1407 nm exhibited a strong linear relationship with the concentration.Subsequently,the K-nearest neighbors(KNN)and support vector machine(SVM)algorithms were employed to classify and identify different concentrations.The study revealed that,with the KNN algorithm,the highest accuracy was achieved when K(number of nearest neighbors)was 1,although this resulted in overfitting.When K=3,the model displayed the optimal balance between accuracy and stability,with an accuracy of 95.03%.In the SVM algorithm,the highest accuracy of 98.24%was attained with parameters C(regularization parameter)=200 and Gamma(kernel coefficient)=10.A comparative analysis of precision,accuracy,and recall further highlighted that the SVM provided superior stability and precision for identifying CPB concentration.Thus,HSI technology offers an effective solution for the in-situ,non-destructive monitoring of CPB concentration,presenting a promising approach for optimizing and controlling CPB characteristic parameters.展开更多
To investigate the pore structure of graphene oxide modified polymer cement mortar(GOPM)under salt-freeze-thaw(SFT)coupling effects and its impact on deterioration,this study modifies polymer cement mortar(EMCM)with g...To investigate the pore structure of graphene oxide modified polymer cement mortar(GOPM)under salt-freeze-thaw(SFT)coupling effects and its impact on deterioration,this study modifies polymer cement mortar(EMCM)with graphene oxide(GO).The micro-pore structure of GOPM is characterized using LF-NMR and SEM.Fractal theory is applied to calculate the fractal dimension of pore volume,and the deterioration patterns are analyzed based on the evolution characteristics of capillary pores.The experimental results indicate that,after 25 salt-freeze-thaw cycles(SFTc),SO2-4 ions penetrate the matrix,generating corrosion products that fill existing pores and enhance the compactness of the specimen.As the number of cycles increases,the ongoing formation and expansion of corrosion products within the matrix,combined with persistent freezing forces,and result in the degradation of the pore structure.Therefore,the mass loss rate(MLR)of the specimens shows a trend of first decreasing and then increasing,while the relative dynamic elastic modulus(RDEM)initially increases and then decreases.Compared to the PC group specimens,the G3PM group specimens show a 28.71% reduction in MLR and a 31.42% increase in RDEM after 150 SFTc.The fractal dimensions of the transition pores,capillary pores,and macropores in the G3PM specimens first increase and then decrease as the number of SFTc increases.Among them,the capillary pores show the highest correlation with MLR and RDEM,with correlation coefficients of 0.97438 and 0.98555,respectively.展开更多
Additive manufacturing(AM)technology has emerged as a viable solution for manufacturing complexshaped WC−Co cemented carbide products,thereby expanding their applications in industries such as resource mining,equipmen...Additive manufacturing(AM)technology has emerged as a viable solution for manufacturing complexshaped WC−Co cemented carbide products,thereby expanding their applications in industries such as resource mining,equipment manufacturing,and electronic information.This review provides a comprehensive summary of the progress of AM technology in WC−Co cemented carbides.The fundamental principles and classification of AM techniques are introduced,followed by a categorization and evaluation of the AM techniques for WC−Co cemented carbides.These techniques are classified as either direct AM technology(DAM)or indirect AM technology(IDAM),depending on their inclusion of post-processes like de-binding and sintering.Through an analysis of microstructure features,the most suitable AM route for WC−Co cemented carbide products with controllable microstructure is identified as the indirect AM technology,such as binder jet printing(BJP),which integrates AM with conventional powder metallurgy.展开更多
As underground mining advances to greater depths,cemented paste backfill(CPB)is increasingly subjected to complex thermo-mechanical loading conditions,including multiaxial stress states and elevated temperatures.This ...As underground mining advances to greater depths,cemented paste backfill(CPB)is increasingly subjected to complex thermo-mechanical loading conditions,including multiaxial stress states and elevated temperatures.This study investigates the coupled effects of field-representative vertical self-weight and horizontal rockwall closure stresses,along with in-situ temperatures,on the mechanical behavior and pore water pressure(PWP)evolution of CPB.Experiments were conducted using a novel apparatus capable of controlling multiaxial stress and temperature during curing,replicating in-situ stress paths and thermal profiles typical of deep mine environments.Results show that multiaxial stress enhances CPB strength and stiffness by promoting denser particle packing,reducing porosity,and increasing frictional resistance.Elevated temperatures independently accelerate early-age cement hydration,further improving bond strength and stiffness.When combined,multiaxial stress and elevated temperature produce a synergistic enhancement in unconfined compressive strength(UCS)and elastic modulus,as confirmed by two-way ANOVA and synergy index analysis.PWP responses were also highly sensitive to thermo-mechanical conditions.The evolution of positive and negative PWP was governed by the interplay of thermal expansion,hydration-induced desaturation,and mechanical compaction.Multiaxial stress amplified early positive PWP and delayed its dissipation,whereas elevated temperature accelerated hydration and reduced pore pressure,leading to enhanced suction at later ages.A transient“stress-induced resaturation”effect was observed under late-stage excessive horizontal stress but was mitigated by elevated temperatures.These findings provide critical insights into the coupled mechanical and hydraulic behavior of CPB under realistic field conditions and offer guidance for optimizing backfill design,binder content,and barricade stability in deep mining applications.展开更多
The utilization of discarded coral debris in cementitious material is a prominent research area for island construction projects.The aim of this study is to explore the use of environment-friendly cement and waste cor...The utilization of discarded coral debris in cementitious material is a prominent research area for island construction projects.The aim of this study is to explore the use of environment-friendly cement and waste coral sand in the preparation of coral mortar,while investigating its performance when exposed to a chloride environment.Three types of low-carbon cements were employed,such as rapid hardening sulphoaluminate(RCSA)cement,high belite sulphoaluminate(HBCSA)cement,and slag sulphoaluminate cement(SSC).The coulomb electric flux,mechanical properties,free chloride content,and mass change of the cement mortar under exposed to 3.5 wt%NaCl solution were examined at various time intervals.X-ray diffraction analysis was conducted to identify the mineral phases present in the mortar samples.The results demonstrate that the flexural and compressive strength of the mortar consistently increase throughout the 360 days chloride exposure period.Incorporating coral sand into SSC-based mortars enhances their compressive strength from day 28 up until day 360.However,it adversely affects the strength of HBCSA-based mortars.The behavior of mortars exposed to a chloride-rich environment is closely associated with the amount of C-S-H gel present within them.SSC generates a significant quantity of C-S-H gel which possesses a large specific surface area capable of absorbing more chloride ions thereby reducing their concentration within the mortar matrix as well as increasing its mass and improving resistance against chloride ion penetration.展开更多
High ground temperature and unloading disturbance have emerged as critical factors impacting the property of cemented gauge-fly ash backfill(CGFB).The characteristics of energy and damage in CGFB were analyzed under c...High ground temperature and unloading disturbance have emerged as critical factors impacting the property of cemented gauge-fly ash backfill(CGFB).The characteristics of energy and damage in CGFB were analyzed under conditions of high ground temperature and unloading by conducting triaxial unloading tests with different initial confining pressures on CGFB that had been cured at various temperatures.Based on dissipative energy,triaxial unloading confining pressure damage constitutive model of CGFB was constructed.It has been demonstrated that the ratio of elastic strain energy in CGFB decreases and the ratio of dissipated energy increases at the end of unloading increases under higher curing temperature.The change in the elastic energy consumption ratio curve of CGFB,which shifts from a gradual increase to a swift rise at a certain"inflection point",can be utilized as a criterion for evaluating the failure of the unloading strength of CGFB.The triaxial unloading damage constitutive model for CGFB divides the damage progression into three distinct phases:initial damage stage,accelerated damage development stage,and rapid damage growth stage.The research findings offer a theoretical foundation for evaluating the extent of damage to CGFB caused by the combined influences of elevated ground temperature and unloading.展开更多
The cemented tailings backfill(CTB)with initial defects is more prone to destabilization damage under the influence of various unfavorable factors during the mining process.In order to investigate its influence on the...The cemented tailings backfill(CTB)with initial defects is more prone to destabilization damage under the influence of various unfavorable factors during the mining process.In order to investigate its influence on the stability of underground mining engineering,this paper simulates the generation of different degrees of initial defects inside the CTB by adding different contents of air-entraining agent(AEA),investigates the acoustic emission RA/AF eigenvalues of CTB with different contents of AEA under uniaxial compression,and adopts various denoising algorithms(e.g.,moving average smoothing,median filtering,and outlier detection)to improve the accuracy of the data.The variance and autocorrelation coefficients of RA/AF parameters were analyzed in conjunction with the critical slowing down(CSD)theory.The results show that the acoustic emission RA/AF values can be used to characterize the progressive damage evolution of CTB.The denoising algorithm processed the AE signals to reduce the effects of extraneous noise and anomalous spikes.Changes in the variance curves provide clear precursor information,while abrupt changes in the autocorrelation coefficient can be used as an auxiliary localization warning signal.The phenomenon of dramatic increase in the variance and autocorrelation coefficient curves during the compression-tightening stage,which is influenced by the initial defects,can lead to false warnings.As the initial defects of the CTB increase,its instability precursor time and instability time are prolonged,the peak stress decreases,and the time difference between the CTB and the instability damage is smaller.The results provide a new method for real-time monitoring and early warning of CTB instability damage.展开更多
The promotion of deep decarbonization in the cement industry is crucial for mitigating global climate change,a key component of which is carbon capture,utilization,and storage(CCUS)technology.Despite its importance,th...The promotion of deep decarbonization in the cement industry is crucial for mitigating global climate change,a key component of which is carbon capture,utilization,and storage(CCUS)technology.Despite its importance,there is a lack of empirical assessments of early opportunities for CCUS implementation in the cement sector.In this study,a comprehensive onshore and offshore source–sink matching optimization assessment framework for CCUS retrofitting in the cement industry,called the SSM-Cement framework,is proposed.The framework comprises four main modules:the cement plant suitability screening module,the storage site assessment module,the source–sink matching optimization model module,and the economic assessment module.By applying this framework to China,919 candidates are initially screened from 1132 existing cement plants.Further,603 CCUS-ready cement plants are identified,and are found to achieve a cumulative emission reduction of 18.5 Gt CO_(2) from 2030 to 2060 by meeting the CCUS feasibility conditions for constructing both onshore and offshore CO_(2) transportation routes.The levelized cost of cement(LCOC)is found to range from 30 to 96(mean 73)USD·(t cement)^(-1),while the levelized carbon avoidance cost(LCAC)ranges from^(-5) to 140(mean 88)USD·(t CO_(2))^(-1).The northeastern and northwestern regions of China are considered priority areas for CCUS implementation,with the LCAC concentrated in the range of 35 to 70 USD·(t CO_(2))^(-1).In addition to onshore storage of 15.8 Gt CO_(2) from 2030 to 2060,offshore storage would contribute 2.7 Gt of decarbonization for coastal cement plants,with comparable LCACs around 90 USD·(t CO_(2))^(-1).展开更多
The good combination of mechanical and wear properties for cemented carbides is crucial.In this work,the wear behavior of functionally graded cemented carbide(FGCC)and non-graded cemented carbide(CC),with CoNiFeCr mul...The good combination of mechanical and wear properties for cemented carbides is crucial.In this work,the wear behavior of functionally graded cemented carbide(FGCC)and non-graded cemented carbide(CC),with CoNiFeCr multi-principal-element alloy(MPEA)binder,has been investigated by performing sliding wear tests and composition characterization.The results showed that compared with CC,FGCC had higher hardness,stronger fracture toughness,better wear performance,and similar TRS.FGCCs exhibited lower wear rates(3.44×10^(−7)–6.95×10^(−6)mm^(3)/(N m))and coefficients of friction(COFs)(0.27–0.39)than CCs from RT to 600℃due to mitigation of multiple risks caused by binder removal,fragmentation and pull-out of WC grains,high-temperature oxidation and softening.In the low-temperature wear stage,the MPEA binder underwent dynamic recrystallization(DRX)and twinning deformation before removing from the surface.The binder removal caused dislocation pile-ups and stacking faults(SFs)to form under high stress,resulting in fragmentation and pull-out of WC grains.The low-temperature wear was dominated by abrasive wear and adhesive wear,with a low wear rate and a high and unstable COF.In the high-temperature wear stage,initial pitting oxidation of WC grains generated many subgrain boundaries,reducing heat transfer and exacerbating oxidation,resulting in an oxide layer enriched with WO3,Mx Oy,and MWO4.High-temperature wear was dominated by oxidation wear and high-temperature softening,with a high wear rate and a low and smooth COF.The results from the present study do not only provide theoretical guidance for an understanding of the antiwear mechanism of WC-CoNiFeCr,but also a new approach for the preparation of cemented carbides with high wear resistance.展开更多
Treatment of peat soil foundation in Yunnan surrounding Dianchi and Erhai Lakes poses complex problems for engineering projects.It is insufficient to rely on ordinary cement to reinforce peat soil.In order to make the...Treatment of peat soil foundation in Yunnan surrounding Dianchi and Erhai Lakes poses complex problems for engineering projects.It is insufficient to rely on ordinary cement to reinforce peat soil.In order to make the reinforcement reliable,this experiment mixed(ultrafine cement)UFC into ordinary cement to form a composite solidify agent.This study aimed to analyze the influence of UFC proportion on the strength of cement-soil in the peat soil environment.Unconfined compressive strength(UCS)and scanning electron microscope(SEM)tests were conducted on samples soaked for 28 and 90 days,respectively.The test results show that without considering the effects of Humic Acid(HA)and Fulvic Acid(FA),incorporating UFC can significantly improve the UCS of cement-soil.The rapid hydration of the fine particles generates a large number of cementitious products,improves the cohesion of the soil skeleton,and fills the pores.However,when the proportion of UFC increases,the aggregate structure formed by a larger quantity of fine particles reduces the hydration rate and degree of cement hydration,making the UCS growth rate of cement-soil insignificant.In the peat soil environment,HA significantly weakened the UCS of cement-soil in both physical and chemical aspects.However,UFC can mitigate the adverse effect of HA on cement-soil by its small particle size,high surface energy,and solid binding ability.In addition,FA has a positive effect on the UCS of cement-soil soaked for 28 days and 90 days.The UFC addition could promote the enhancement effect of FA on cement-soil UCS.SEM test results showed that cement hydration products increased significantly with the increase of UFC proportion,and cementation between hydration products and soil particles was enhanced.The size and connectivity of cement-soil pores were significantly reduced,thereby improving cement-soil structural integrity.展开更多
Weak cementation between natural gas hydrates and mud–sand seriously affects the solid-fluidized mining of natural gas hydrates. In this study, we analyze the debonding of natural gas hydrate sediment (NGHS) particle...Weak cementation between natural gas hydrates and mud–sand seriously affects the solid-fluidized mining of natural gas hydrates. In this study, we analyze the debonding of natural gas hydrate sediment (NGHS) particles by applying the principle of spiral-cyclone coupling separation. To achieve this, weakly cemented NGHS particle and mechanical models were established. In the flow field of the spiral-cyclone flow-coupling separator, the motion characteristics of the weakly cemented NGHS particles and the destruction process of the cementation bond were analyzed. The destruction of the bonds mainly occurred in the spiral channel, and the destruction efficiency of the bonds was mainly affected by the rotational speed. Collision analysis of the particles and walls showed that when the velocity is 10–16 m·s^(−1), the cementation bond can be broken. The greater the speed, the better the effect of the bond fracture. The breaking rate of the cementation bonds was 85.7%. This study is significant for improving the degumming efficiency in natural gas hydrate exploitation, improving the recovery efficiency of hydrates, and promoting the commercialization of hydrate solid fluidization exploitation.展开更多
Utilizing mine solid waste as a partial cement substitute(CS)to develop new cementitious materials is a significant technological innovation that will decrease the expenses associated with filling mining.To realize th...Utilizing mine solid waste as a partial cement substitute(CS)to develop new cementitious materials is a significant technological innovation that will decrease the expenses associated with filling mining.To realize the resource utilization of magnesium slag(MS)and blast furnace slag(BFS),the effects of different contents of MS and BFS as partial CSs on the deformation and energy characteristics of cemented tailings backfill on different curing ages(3,7,and 28 d)were discussed.Meanwhile,the destabilization failure energy criterion of the backfill was established from the direction of energy change.The results show that the strength of all backfills increased with increasing curing age,and the strengths of the backfills exceeded 1.342 MPa on day 28.The backfill with 50%BFS+50%cement has the best performance in mechanical properties(the maximum strength can reach 6.129 MPa)and is the best choice among these CS combinations.The trend in peak strain and elastic modulus of the backfill with increasing curing age may vary depending on the CS combination.The energy index at peak stress of the backfill with BFS as a partial CS was significantly higher than that of the backfill under other CS combinations.In contrast,the enhancement of the energy index when MS was used as a partial CS was not as significant as BFS.Sharp changes in the energy consumption ratio after continuous smooth changes can be used as a criterion for destabilization and failure of the backfill.The research results can provide guidance for the application of MS and BFS as partial CSs in mine filling.展开更多
The strength of backfill body is a crucial parameter in backfilling mining,and the failure process of cemented backfill body is essentially an energy dissipation process.To investigate the effects of curing age and ce...The strength of backfill body is a crucial parameter in backfilling mining,and the failure process of cemented backfill body is essentially an energy dissipation process.To investigate the effects of curing age and cement-sand ratio on the strength and energy consumption of backfill,whole tailings were used as aggregate to prepare slurry with mass concentration of 74%,and the slurry with cement-sand ratio of 1:4,1:6,1:8 and 1:12 was poured into backfill.Uniaxial compression tests were conducted on backfill body specimens that had been cured for 7 days,14 days,28 days,and 45 days.It aims at studying the compressive strength,damage,energy storage limit,energy dissipation,and crack propagation of the fill.The results show that when the cement-sand ratio is held constant,the strength of the backfill increases with curing age.Simultaneously,when the curing age is fixed,the strength is positively correlated with the cement-sand ratio.During uniaxial compression tests,it is observed that the pre-peak energy consumption,post-peak energy consumption,total energy consumption,and unit volume strain energy of the cemented backfill body exhibit exponential relationships with both curing age and cement-sand ratio.The energy storage limit of the backfill reflects its capacity to absorb energy prior to failure,while the relationship between damage and energy consumption provides an accurate depiction of its internal failure mechanisms at different stages.In the failure process of the cemented backfill body,primary cracks accompany secondary cracks,many microcracks initiate and propagate from the stress direction,and crack propagation consumes a significant amount of energy.This study on the strength,energy storage limit,and failure of the cemented backfill body can provide valuable insights for mine safety production.展开更多
The first author proposed the concept of the cemented material dam （CMD） in 2009. This concept was aimed at building an environmentally friendly dam in a safer and more economical way for both the dam and the area d...The first author proposed the concept of the cemented material dam （CMD） in 2009. This concept was aimed at building an environmentally friendly dam in a safer and more economical way for both the dam and the area downstream. The concept covers the cemented sand, gravel, and rock dam （CSGRD）, the rockfill concrete （RFC） dam （or the cemented rockfill dam, CRD）, and the cemented soil dam （CSD）. This paper summarizes the concept and principles of the CMD based on studies and practices in projects around the world. It also introduces new developments in the CSGRD, CRD, and CSD.展开更多
基金supports from the National Natural Science Foundation of China(No.52304148)the Youth Project of Shanxi Basic Research Program(No.202203021212262).
文摘This study investigates the performance enhancement of super-sulfated cement(SSC)derived from arsenic-containing bio-oxidation waste(BW)through the incorporation of carbonated recycled concrete fines(CRCF).The findings revealed that the addition of 5wt%CRCF yields optimal performance,with compressive strengths reaching approximately 1.83,12.59,and 42.81 MPa at 1,3,and 28 d,respectively.These values represented significant increases of 408.3%,10.0%,and 14.3%compared to the reference sample.The improvement was attributed to the synergistic effects of ultrafine CRCF particles acting as fillers and nucleation sites,as well as the high reactivity of silica gels,which promoted the formation of additional hydration gels.Microstructural analysis confirmed that CRCF addition refined pore structure,and enhanced the stiffness of C-S-H gels.Furthermore,CRCF served as a net CO_(2) sink,sequestering 0.268 kg CO_(2) per kilogram of CRCF and thereby reducing the carbon footprint of SSC.In addition,the feasibility of applying CRCF-modified SSC in cemented paste backfill(CPB)is highlighted,given the high cement-related carbon footprint of conventional CPB.When 5wt%CRCFmodified SSC was employed in CPB,its 3-d compressive strength attained over 70%of that of ordinary Portland cement(OPC),while the 28-d strength was comparable to that of OPC.The proposed binder thus provides a sustainable pathway for BW valorization,combining waste utilization,carbon sequestration,and improved engineering performance.
基金supported by the National Key R&D Program of China(Grant Nos.U25A20810 and 2024YFF0508201)the National Natural Science Foundation of China(Grant No.12302504).
文摘In coal mining on a high-pressure Ordovician limestone aquifer,grouting materials should have sufficient mechanical properties,particularly strong interfacial bonding performance to address stress concentration at the grout-limestone interface induced by rock stress disturbances during mining.In this study,graphene oxide(GO)was integrated into cement-polyacrylate composite grout to improve its interfacial bonding.First,four-point bending tests were conducted,and the Monte Carlo method combined with the simplex search algorithm was employed to determine the variations in shear cohesion and static friction parameters.The results reveal that GO can significantly increase both the tensile and shear cohesion of the grout-limestone interface,but minimally affects the interfacial friction coefficient.Second,nuclear magnetic resonance(NMR)and scanning electron microscopy(SEM)tests were performed.The results indicate that GO nanosheets result in a squamaceous microstructure of the grout consolidation mass,increasing the adhesion of the grout-limestone interface.Moreover,spiny Aft(ettringite)clusters can be induced in limestone fracture surfaces by GO,which could serve as anchors for limestone and grout consolidation mass.
文摘Improving energy efficiency and lowering negative environmental impact through waste heat recovery(WHR)is a critical step toward sustainable cement manufacturing.This study analyzes advanced cogeneration systems for recovering waste heat from the Fallujah White Cement Plant in Iraq.The novelty of this work lies in its direct application and comparative thermodynamic analysis of three distinct cogeneration cycles—the Organic Rankine Cycle,the Single-Flash Steam Cycle,and the Dual-Pressure Steam Cycle—within the Iraqi cement industry,a context that has not been widely studied.The main objective is to evaluate and compare these models to determine the most effective approach for enhancing energy and exergy efficiencies.Themethodology involved detailed thermodynamic and exergy analyses of each system,supported by mathematical modelling and simulation using data from plant operations.The results reveal that the Dual-Pressure Steam Cycle emerged as the most effective system,delivering 13.76 MW of net power with a thermal efficiency of 32.8%and an exergy efficiency of 51%.This significantly outperformed the baseline Organic Rankine Cycle(8.18MW,18.8%thermal efficiency,30.7%exergy efficiency).These findings confirm that multipressure steam cycles offer a robust and practical solution for the Fallujah plant.This application provides a clear,high-impact pathway to enhance national industrial energy efficiency,significantly reduce CO_(2) emissions,and promote clean energy sustainability in Iraq.Future work should consider economic feasibility and potential integration with renewable energy sources to further enhance sustainability.
基金supported by the National Natural Science Foundation of China(No.52242305).
文摘Cement stands as a dominant contributor to global energy consumption and carbon emissions in the construction industry.With the upgrading of infrastructure and the improvement of building standards,traditional cement fails to reconcile ecological responsibility with advanced functional performance.By incorporating tailored fillers into cement matrices,the resulting composites achieve enhanced thermoelectric(TE)conversion capabilities.These materials can harness solar radiation from building envelopes and recover waste heat from indoor thermal gradients,facilitating bidirectional energy conversion.This review offers a comprehensive and timely overview of cementbased thermoelectric materials(CTEMs),integrating material design,device fabrication,and diverse applications into a holistic perspective.It summarizes recent advancements in TE performance enhancement,encompassing fillers optimization and matrices innovation.Additionally,the review consolidates fabrication strategies and performance evaluations of cement-based thermoelectric devices(CTEDs),providing detailed discussions on their roles in monitoring and protection,energy harvesting,and smart building.We also address sustainability,durability,and lifecycle considerations of CTEMs,which are essential for real-world deployment.Finally,we outline future research directions in materials design,device engineering,and scalable manufacturing to foster the practical application of CTEMs in sustainable and intelligent infrastructure.
基金Project(2022YFC2904103)supported by the National Key Research and Development Program of ChinaProjects(52374112,52274108)supported by the National Natural Science Foundation of China+1 种基金Projects(BX20220036,BX20230041)supported by the Postdoctoral Innovation Talents Support Program,ChinaProject(2232080)supported by the Beijing Natural Science Foundation,China。
文摘The development of metallic mineral resources generates a significant amount of solid waste,such as tailings and waste rock.Cemented tailings and waste-rock backfill(CTWB)is an effective method for managing and disposing of this mining waste.This study employs a macro-meso-micro testing method to investigate the effects of the waste rock grading index(WGI)and loading rate(LR)on the uniaxial compressive strength(UCS),pore structure,and micromorphology of CTWB materials.Pore structures were analyzed using scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP).The particles(pores)and cracks analysis system(PCAS)software was used to quantitatively characterize the multi-scale micropores in the SEM images.The key findings indicate that the macroscopic results(UCS)of CTWB materials correspond to the microscopic results(pore structure and micromorphology).Changes in porosity largely depend on the conditions of waste rock grading index and loading rate.The inclusion of waste rock initially increases and then decreases the UCS,while porosity first decreases and then increases,with a critical waste rock grading index of 0.6.As the loading rate increases,UCS initially rises and then falls,while porosity gradually increases.Based on MIP and SEM results,at waste rock grading index 0.6,the most probable pore diameters,total pore area(TPA),pore number(PN),maximum pore area(MPA),and area probability distribution index(APDI)are minimized,while average pore form factor(APF)and fractal dimension of pore porosity distribution(FDPD)are maximized,indicating the most compact pore structure.At a loading rate of 12.0 mm/min,the most probable pore diameters,TPA,PN,MPA,APF,and APDI reach their maximum values,while FDPD reaches its minimum value.Finally,the mechanism of CTWB materials during compression is analyzed,based on the quantitative results of UCS and porosity.The research findings play a crucial role in ensuring the successful application of CTWB materials in deep metal mines.
基金funded by the National Natural Science Foundation of China(Nos.52474165 and 52522404)。
文摘Cemented paste backfill(CPB)is a technology that achieves safe mining by filling the goaf with waste rocks,tailings,and other materials.It is an inevitable choice to deal with the development of deep and highly difficult mines and meet the requirements of environmental protection and safety regulations.It promotes the development of a circular economy in mines through the development of lowgrade resources and the resource utilization of waste,and extends the service life of mines.The mass concentration of solid content(abbreviated as“concentration”)is a critical parameter for CPB.However,discrepancies often arise between the on-site measurements and the pre-designed values due to factors such as groundwater inflow and segregation within the goaf,which cannot be evaluated after the solidification of CPB.This paper innovatively provides an in-situ non-destructive approach to identify the real concentration of CPB after curing for certain days using hyperspectral imaging(HSI)technology.Initially,the spectral variation patterns under different concentration conditions were investigated through hyperspectral scanning experiments on CPB samples.The results demonstrate that as the CPB concentration increases from 61wt%to 73wt%,the overall spectral reflectance gradually increases,with two distinct absorption peaks observed at 1407 and 1917 nm.Notably,the reflectance at 1407 nm exhibited a strong linear relationship with the concentration.Subsequently,the K-nearest neighbors(KNN)and support vector machine(SVM)algorithms were employed to classify and identify different concentrations.The study revealed that,with the KNN algorithm,the highest accuracy was achieved when K(number of nearest neighbors)was 1,although this resulted in overfitting.When K=3,the model displayed the optimal balance between accuracy and stability,with an accuracy of 95.03%.In the SVM algorithm,the highest accuracy of 98.24%was attained with parameters C(regularization parameter)=200 and Gamma(kernel coefficient)=10.A comparative analysis of precision,accuracy,and recall further highlighted that the SVM provided superior stability and precision for identifying CPB concentration.Thus,HSI technology offers an effective solution for the in-situ,non-destructive monitoring of CPB concentration,presenting a promising approach for optimizing and controlling CPB characteristic parameters.
基金Funded by the National Natural Science Foundation of China(Nos.5226804252468035)。
文摘To investigate the pore structure of graphene oxide modified polymer cement mortar(GOPM)under salt-freeze-thaw(SFT)coupling effects and its impact on deterioration,this study modifies polymer cement mortar(EMCM)with graphene oxide(GO).The micro-pore structure of GOPM is characterized using LF-NMR and SEM.Fractal theory is applied to calculate the fractal dimension of pore volume,and the deterioration patterns are analyzed based on the evolution characteristics of capillary pores.The experimental results indicate that,after 25 salt-freeze-thaw cycles(SFTc),SO2-4 ions penetrate the matrix,generating corrosion products that fill existing pores and enhance the compactness of the specimen.As the number of cycles increases,the ongoing formation and expansion of corrosion products within the matrix,combined with persistent freezing forces,and result in the degradation of the pore structure.Therefore,the mass loss rate(MLR)of the specimens shows a trend of first decreasing and then increasing,while the relative dynamic elastic modulus(RDEM)initially increases and then decreases.Compared to the PC group specimens,the G3PM group specimens show a 28.71% reduction in MLR and a 31.42% increase in RDEM after 150 SFTc.The fractal dimensions of the transition pores,capillary pores,and macropores in the G3PM specimens first increase and then decrease as the number of SFTc increases.Among them,the capillary pores show the highest correlation with MLR and RDEM,with correlation coefficients of 0.97438 and 0.98555,respectively.
基金supported by Major Science and Technology Projects in Fujian Province,China(No.2023HZ021005)State Key Laboratory of Powder Metallurgy,Central South University,ChinaFujian Key Laboratory of Rare-earth Functional Materials,China。
文摘Additive manufacturing(AM)technology has emerged as a viable solution for manufacturing complexshaped WC−Co cemented carbide products,thereby expanding their applications in industries such as resource mining,equipment manufacturing,and electronic information.This review provides a comprehensive summary of the progress of AM technology in WC−Co cemented carbides.The fundamental principles and classification of AM techniques are introduced,followed by a categorization and evaluation of the AM techniques for WC−Co cemented carbides.These techniques are classified as either direct AM technology(DAM)or indirect AM technology(IDAM),depending on their inclusion of post-processes like de-binding and sintering.Through an analysis of microstructure features,the most suitable AM route for WC−Co cemented carbide products with controllable microstructure is identified as the indirect AM technology,such as binder jet printing(BJP),which integrates AM with conventional powder metallurgy.
基金the University of Ottawa, the China Scholarship Council and the Natural Sciences and Engineering Research Council of Canada (NSERC) for their financial support.
文摘As underground mining advances to greater depths,cemented paste backfill(CPB)is increasingly subjected to complex thermo-mechanical loading conditions,including multiaxial stress states and elevated temperatures.This study investigates the coupled effects of field-representative vertical self-weight and horizontal rockwall closure stresses,along with in-situ temperatures,on the mechanical behavior and pore water pressure(PWP)evolution of CPB.Experiments were conducted using a novel apparatus capable of controlling multiaxial stress and temperature during curing,replicating in-situ stress paths and thermal profiles typical of deep mine environments.Results show that multiaxial stress enhances CPB strength and stiffness by promoting denser particle packing,reducing porosity,and increasing frictional resistance.Elevated temperatures independently accelerate early-age cement hydration,further improving bond strength and stiffness.When combined,multiaxial stress and elevated temperature produce a synergistic enhancement in unconfined compressive strength(UCS)and elastic modulus,as confirmed by two-way ANOVA and synergy index analysis.PWP responses were also highly sensitive to thermo-mechanical conditions.The evolution of positive and negative PWP was governed by the interplay of thermal expansion,hydration-induced desaturation,and mechanical compaction.Multiaxial stress amplified early positive PWP and delayed its dissipation,whereas elevated temperature accelerated hydration and reduced pore pressure,leading to enhanced suction at later ages.A transient“stress-induced resaturation”effect was observed under late-stage excessive horizontal stress but was mitigated by elevated temperatures.These findings provide critical insights into the coupled mechanical and hydraulic behavior of CPB under realistic field conditions and offer guidance for optimizing backfill design,binder content,and barricade stability in deep mining applications.
基金Funded by the National Natural Science Foundation of China(No.51708290)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘The utilization of discarded coral debris in cementitious material is a prominent research area for island construction projects.The aim of this study is to explore the use of environment-friendly cement and waste coral sand in the preparation of coral mortar,while investigating its performance when exposed to a chloride environment.Three types of low-carbon cements were employed,such as rapid hardening sulphoaluminate(RCSA)cement,high belite sulphoaluminate(HBCSA)cement,and slag sulphoaluminate cement(SSC).The coulomb electric flux,mechanical properties,free chloride content,and mass change of the cement mortar under exposed to 3.5 wt%NaCl solution were examined at various time intervals.X-ray diffraction analysis was conducted to identify the mineral phases present in the mortar samples.The results demonstrate that the flexural and compressive strength of the mortar consistently increase throughout the 360 days chloride exposure period.Incorporating coral sand into SSC-based mortars enhances their compressive strength from day 28 up until day 360.However,it adversely affects the strength of HBCSA-based mortars.The behavior of mortars exposed to a chloride-rich environment is closely associated with the amount of C-S-H gel present within them.SSC generates a significant quantity of C-S-H gel which possesses a large specific surface area capable of absorbing more chloride ions thereby reducing their concentration within the mortar matrix as well as increasing its mass and improving resistance against chloride ion penetration.
基金Project(2024YFC2911000)supported by the National Key Research and Development Program Young Scientist Project,ChinaProject(2022HWYQ-078)supported by the Natural Science Foundation of Shandong Province of China+1 种基金Project(tsqn202103074)supported by the"Taishan Scholars Young Expert Program"of Shandong Province,ChinaProject(2023GX051)supported by the Tai'an Science and Technology Innovation Development Project(Policy Guidance),China。
文摘High ground temperature and unloading disturbance have emerged as critical factors impacting the property of cemented gauge-fly ash backfill(CGFB).The characteristics of energy and damage in CGFB were analyzed under conditions of high ground temperature and unloading by conducting triaxial unloading tests with different initial confining pressures on CGFB that had been cured at various temperatures.Based on dissipative energy,triaxial unloading confining pressure damage constitutive model of CGFB was constructed.It has been demonstrated that the ratio of elastic strain energy in CGFB decreases and the ratio of dissipated energy increases at the end of unloading increases under higher curing temperature.The change in the elastic energy consumption ratio curve of CGFB,which shifts from a gradual increase to a swift rise at a certain"inflection point",can be utilized as a criterion for evaluating the failure of the unloading strength of CGFB.The triaxial unloading damage constitutive model for CGFB divides the damage progression into three distinct phases:initial damage stage,accelerated damage development stage,and rapid damage growth stage.The research findings offer a theoretical foundation for evaluating the extent of damage to CGFB caused by the combined influences of elevated ground temperature and unloading.
基金Projects(52374138,51764013)supported by the National Natural Science Foundation of ChinaProject(20204BCJ22005)supported by the Training Plan for Academic and Technical Leaders of Major Disciplines of Jiangxi Province,China+1 种基金Project(2019M652277)supported by the China Postdoctoral Science FoundationProject(20192ACBL21014)supported by the Natural Science Youth Foundation Key Projects of Jiangxi Province,China。
文摘The cemented tailings backfill(CTB)with initial defects is more prone to destabilization damage under the influence of various unfavorable factors during the mining process.In order to investigate its influence on the stability of underground mining engineering,this paper simulates the generation of different degrees of initial defects inside the CTB by adding different contents of air-entraining agent(AEA),investigates the acoustic emission RA/AF eigenvalues of CTB with different contents of AEA under uniaxial compression,and adopts various denoising algorithms(e.g.,moving average smoothing,median filtering,and outlier detection)to improve the accuracy of the data.The variance and autocorrelation coefficients of RA/AF parameters were analyzed in conjunction with the critical slowing down(CSD)theory.The results show that the acoustic emission RA/AF values can be used to characterize the progressive damage evolution of CTB.The denoising algorithm processed the AE signals to reduce the effects of extraneous noise and anomalous spikes.Changes in the variance curves provide clear precursor information,while abrupt changes in the autocorrelation coefficient can be used as an auxiliary localization warning signal.The phenomenon of dramatic increase in the variance and autocorrelation coefficient curves during the compression-tightening stage,which is influenced by the initial defects,can lead to false warnings.As the initial defects of the CTB increase,its instability precursor time and instability time are prolonged,the peak stress decreases,and the time difference between the CTB and the instability damage is smaller.The results provide a new method for real-time monitoring and early warning of CTB instability damage.
基金financial support of National Natural Science Foundation of China(72174196 and 71874193)the Open Fund of State Key Laboratory of Coal Resources and Safe Mining(SKLCRSM21KFA05)National Program for Support of Top-Notch Young Professionals.
文摘The promotion of deep decarbonization in the cement industry is crucial for mitigating global climate change,a key component of which is carbon capture,utilization,and storage(CCUS)technology.Despite its importance,there is a lack of empirical assessments of early opportunities for CCUS implementation in the cement sector.In this study,a comprehensive onshore and offshore source–sink matching optimization assessment framework for CCUS retrofitting in the cement industry,called the SSM-Cement framework,is proposed.The framework comprises four main modules:the cement plant suitability screening module,the storage site assessment module,the source–sink matching optimization model module,and the economic assessment module.By applying this framework to China,919 candidates are initially screened from 1132 existing cement plants.Further,603 CCUS-ready cement plants are identified,and are found to achieve a cumulative emission reduction of 18.5 Gt CO_(2) from 2030 to 2060 by meeting the CCUS feasibility conditions for constructing both onshore and offshore CO_(2) transportation routes.The levelized cost of cement(LCOC)is found to range from 30 to 96(mean 73)USD·(t cement)^(-1),while the levelized carbon avoidance cost(LCAC)ranges from^(-5) to 140(mean 88)USD·(t CO_(2))^(-1).The northeastern and northwestern regions of China are considered priority areas for CCUS implementation,with the LCAC concentrated in the range of 35 to 70 USD·(t CO_(2))^(-1).In addition to onshore storage of 15.8 Gt CO_(2) from 2030 to 2060,offshore storage would contribute 2.7 Gt of decarbonization for coastal cement plants,with comparable LCACs around 90 USD·(t CO_(2))^(-1).
基金financially supported by the National Key Research and Development Program of China(No.2021YFB3701800)Special funding support for the Yuelu Mountain National University Science and Technology City“Ranking the Top of the List”Research Project:(Tunnel Boring Machine High-performance Long-life Cutting Tools)the State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China.
文摘The good combination of mechanical and wear properties for cemented carbides is crucial.In this work,the wear behavior of functionally graded cemented carbide(FGCC)and non-graded cemented carbide(CC),with CoNiFeCr multi-principal-element alloy(MPEA)binder,has been investigated by performing sliding wear tests and composition characterization.The results showed that compared with CC,FGCC had higher hardness,stronger fracture toughness,better wear performance,and similar TRS.FGCCs exhibited lower wear rates(3.44×10^(−7)–6.95×10^(−6)mm^(3)/(N m))and coefficients of friction(COFs)(0.27–0.39)than CCs from RT to 600℃due to mitigation of multiple risks caused by binder removal,fragmentation and pull-out of WC grains,high-temperature oxidation and softening.In the low-temperature wear stage,the MPEA binder underwent dynamic recrystallization(DRX)and twinning deformation before removing from the surface.The binder removal caused dislocation pile-ups and stacking faults(SFs)to form under high stress,resulting in fragmentation and pull-out of WC grains.The low-temperature wear was dominated by abrasive wear and adhesive wear,with a low wear rate and a high and unstable COF.In the high-temperature wear stage,initial pitting oxidation of WC grains generated many subgrain boundaries,reducing heat transfer and exacerbating oxidation,resulting in an oxide layer enriched with WO3,Mx Oy,and MWO4.High-temperature wear was dominated by oxidation wear and high-temperature softening,with a high wear rate and a low and smooth COF.The results from the present study do not only provide theoretical guidance for an understanding of the antiwear mechanism of WC-CoNiFeCr,but also a new approach for the preparation of cemented carbides with high wear resistance.
基金National Natural Science Foundation of China(No.41967035)。
文摘Treatment of peat soil foundation in Yunnan surrounding Dianchi and Erhai Lakes poses complex problems for engineering projects.It is insufficient to rely on ordinary cement to reinforce peat soil.In order to make the reinforcement reliable,this experiment mixed(ultrafine cement)UFC into ordinary cement to form a composite solidify agent.This study aimed to analyze the influence of UFC proportion on the strength of cement-soil in the peat soil environment.Unconfined compressive strength(UCS)and scanning electron microscope(SEM)tests were conducted on samples soaked for 28 and 90 days,respectively.The test results show that without considering the effects of Humic Acid(HA)and Fulvic Acid(FA),incorporating UFC can significantly improve the UCS of cement-soil.The rapid hydration of the fine particles generates a large number of cementitious products,improves the cohesion of the soil skeleton,and fills the pores.However,when the proportion of UFC increases,the aggregate structure formed by a larger quantity of fine particles reduces the hydration rate and degree of cement hydration,making the UCS growth rate of cement-soil insignificant.In the peat soil environment,HA significantly weakened the UCS of cement-soil in both physical and chemical aspects.However,UFC can mitigate the adverse effect of HA on cement-soil by its small particle size,high surface energy,and solid binding ability.In addition,FA has a positive effect on the UCS of cement-soil soaked for 28 days and 90 days.The UFC addition could promote the enhancement effect of FA on cement-soil UCS.SEM test results showed that cement hydration products increased significantly with the increase of UFC proportion,and cementation between hydration products and soil particles was enhanced.The size and connectivity of cement-soil pores were significantly reduced,thereby improving cement-soil structural integrity.
基金funded by the State Key Laboratory of Natural Gas Hydrate of China(2022-KFJJ-SHW)the National Key Research and Development Program of China(2021YFC2800903)+2 种基金the National Natural Science Foundation of China(52004235)the National Natural Science Foundation General Program of China(52374011)the Miaozi Engineering Cultivation Project of Sichuan Science and Technology Department of China(MZG20230127).
文摘Weak cementation between natural gas hydrates and mud–sand seriously affects the solid-fluidized mining of natural gas hydrates. In this study, we analyze the debonding of natural gas hydrate sediment (NGHS) particles by applying the principle of spiral-cyclone coupling separation. To achieve this, weakly cemented NGHS particle and mechanical models were established. In the flow field of the spiral-cyclone flow-coupling separator, the motion characteristics of the weakly cemented NGHS particles and the destruction process of the cementation bond were analyzed. The destruction of the bonds mainly occurred in the spiral channel, and the destruction efficiency of the bonds was mainly affected by the rotational speed. Collision analysis of the particles and walls showed that when the velocity is 10–16 m·s^(−1), the cementation bond can be broken. The greater the speed, the better the effect of the bond fracture. The breaking rate of the cementation bonds was 85.7%. This study is significant for improving the degumming efficiency in natural gas hydrate exploitation, improving the recovery efficiency of hydrates, and promoting the commercialization of hydrate solid fluidization exploitation.
基金Projects(52274108,U2341265)supported by the National Natural Science Foundation of ChinaProject(2022YFC2904103)supported by the National Key Research and Development Program of China。
文摘Utilizing mine solid waste as a partial cement substitute(CS)to develop new cementitious materials is a significant technological innovation that will decrease the expenses associated with filling mining.To realize the resource utilization of magnesium slag(MS)and blast furnace slag(BFS),the effects of different contents of MS and BFS as partial CSs on the deformation and energy characteristics of cemented tailings backfill on different curing ages(3,7,and 28 d)were discussed.Meanwhile,the destabilization failure energy criterion of the backfill was established from the direction of energy change.The results show that the strength of all backfills increased with increasing curing age,and the strengths of the backfills exceeded 1.342 MPa on day 28.The backfill with 50%BFS+50%cement has the best performance in mechanical properties(the maximum strength can reach 6.129 MPa)and is the best choice among these CS combinations.The trend in peak strain and elastic modulus of the backfill with increasing curing age may vary depending on the CS combination.The energy index at peak stress of the backfill with BFS as a partial CS was significantly higher than that of the backfill under other CS combinations.In contrast,the enhancement of the energy index when MS was used as a partial CS was not as significant as BFS.Sharp changes in the energy consumption ratio after continuous smooth changes can be used as a criterion for destabilization and failure of the backfill.The research results can provide guidance for the application of MS and BFS as partial CSs in mine filling.
基金funded by the National Natural Science Foundation of China(52474131)the National Natural Science Foundation of China(42467022)+1 种基金the Yunnan Major Scientific and Technological Projects(Grant No.202202AG050014)the Yunnan Fundamental Research Projects(NO.202101BE070001-038,202201AT070146).
文摘The strength of backfill body is a crucial parameter in backfilling mining,and the failure process of cemented backfill body is essentially an energy dissipation process.To investigate the effects of curing age and cement-sand ratio on the strength and energy consumption of backfill,whole tailings were used as aggregate to prepare slurry with mass concentration of 74%,and the slurry with cement-sand ratio of 1:4,1:6,1:8 and 1:12 was poured into backfill.Uniaxial compression tests were conducted on backfill body specimens that had been cured for 7 days,14 days,28 days,and 45 days.It aims at studying the compressive strength,damage,energy storage limit,energy dissipation,and crack propagation of the fill.The results show that when the cement-sand ratio is held constant,the strength of the backfill increases with curing age.Simultaneously,when the curing age is fixed,the strength is positively correlated with the cement-sand ratio.During uniaxial compression tests,it is observed that the pre-peak energy consumption,post-peak energy consumption,total energy consumption,and unit volume strain energy of the cemented backfill body exhibit exponential relationships with both curing age and cement-sand ratio.The energy storage limit of the backfill reflects its capacity to absorb energy prior to failure,while the relationship between damage and energy consumption provides an accurate depiction of its internal failure mechanisms at different stages.In the failure process of the cemented backfill body,primary cracks accompany secondary cracks,many microcracks initiate and propagate from the stress direction,and crack propagation consumes a significant amount of energy.This study on the strength,energy storage limit,and failure of the cemented backfill body can provide valuable insights for mine safety production.
文摘The first author proposed the concept of the cemented material dam （CMD） in 2009. This concept was aimed at building an environmentally friendly dam in a safer and more economical way for both the dam and the area downstream. The concept covers the cemented sand, gravel, and rock dam （CSGRD）, the rockfill concrete （RFC） dam （or the cemented rockfill dam, CRD）, and the cemented soil dam （CSD）. This paper summarizes the concept and principles of the CMD based on studies and practices in projects around the world. It also introduces new developments in the CSGRD, CRD, and CSD.
