Enzyme-induced carbonate precipitation(EICP)has emerged as an innovative soil stabilization technology to precipitate CaCO_(3)by catalyzing urea decomposition.Although extensive efforts have been made to increase the ...Enzyme-induced carbonate precipitation(EICP)has emerged as an innovative soil stabilization technology to precipitate CaCO_(3)by catalyzing urea decomposition.Although extensive efforts have been made to increase the calcium carbonate content(CCC)formed in the EICP process for the better biocementation effect,the cementability and micromechanical properties of CaCO_(3)are rarely known.A study of the cementitious characteristics and micromechanical properties of CaCO_(3)precipitates with different mixing percentages of crystal morphology is essential for soil improvement.In the present study,ultrasonic oscillation tests and nanoindentation tests were performed to investigate the cementability and micromechanical properties of CaCO_(3)precipitate.The results show that the cementability and micromechanical properties of CaCO_(3)precipitate are related to the composition of the crystal morphology.A high content of calcite is beneficial to improve the adhesion of calcium carbonate precipitate.Calcite has better mechanical properties(elastic modulus,hardness and ductility)than vaterite,and the presence of vaterite can significantly affect the measured value of mechanical properties in nanoindentation tests.The ductility of CaCO_(3)precipitate induced by crude soybean urease(CSU)is higher than that of CaCO_(3)precipitate induced by commercially available pure enzyme,suggesting that commercially available pure enzyme can be replaced by CSU for cost-effective field-scale engineering applications.This work can provide insight into optimizing the properties of CaCO_(3)precipitate from the micro-scale.展开更多
The engineering application of low-alkali sulphoaluminate cement(L-SAC)is hindered due to the difficulty in adjusting the setting and hardening time.In this paper,lithium hydroxide and borax are mixed into L-SAC to re...The engineering application of low-alkali sulphoaluminate cement(L-SAC)is hindered due to the difficulty in adjusting the setting and hardening time.In this paper,lithium hydroxide and borax are mixed into L-SAC to regulate its setting and hardening process,so as to prepare a sulphoaluminate concrete material with high early strength and high fluidity.The effects of the ratio of lithium hydroxide to borax on the properties of L-SAC concrete were studied by hydration heat,XRD,TG-DTG,SEM and MIP.The experimental results show that the slump increases with the increase of borax content,and the early(3 h)strength increases with the increase of lithium hydroxide content.When 0.05% lithium hydroxide and 0.4% borax are added,the 0.5 h slump reaches 195 mm,and the 3 h compressive strength reaches 15.9 MPa.The increase of lithium hydroxide will promote the formation of early hydration products AFt and AH3 gel and accelerate the hydration process,while borax will inhibit the dissolution and hydration of cement and delay the setting and hardening process of concrete.The combination of the two ensures that the concrete has the characteristics of high early strength and high fluidity,and the early workability and mechanical properties can be controlled by the mix ratio.For long-term mechanical properties,the special concrete does not produce AFm,which can ensure the continuous development of strength.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
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
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
A green pregelatinized glutinous rice flour biological admixture was developed in this paper.The cement hydration process,hydration products,pore structure,and strength of mortar with different quantities of glutinous...A green pregelatinized glutinous rice flour biological admixture was developed in this paper.The cement hydration process,hydration products,pore structure,and strength of mortar with different quantities of glutinous rice flour(GRF),and the macroscopic changes in concrete cracking resistance testing were investigated.Simultaneously,a fast cracking resistance evaluation method based on graphic recognition was proposed.The results indicated that pregelatinized glutinous rice flour(T-GRF)delayed the dissolution rate of anhydrous cement during the induction period,shifting the main exothermic peak of hydration backward.The compressive strength developed slowly in 7-28 d age and returned to normal in 28-56 d.The compressive strength of T-GRF-0.6% modified mortar at 56 d age is less than 10% different from that of control group.The 3.0%T-GRF decreased the total porosity by 3%,and the average pore size decreased from 31.2 to 21.3 nm measured by MIP,indicating that T-GRF could inhibit harmful pores and densify concrete.The crack resistance coefficient of T-GRF modified concrete was obtained by image recognition method,and the GRF could decrease the length,width,and damaged area of cracks in the early age of concrete.展开更多
Ti(C,N)-Mo_(2)C-Ni cermet as alternative materials was explored for use in alkaline conditions,replacing the WC-Co cemented carbides,since Co is classified as a potentially carcinogenic substance and there is potentia...Ti(C,N)-Mo_(2)C-Ni cermet as alternative materials was explored for use in alkaline conditions,replacing the WC-Co cemented carbides,since Co is classified as a potentially carcinogenic substance and there is potential hazard of“hard metal disease”under the exposure to cobalt dust.The changes in microstructure,corrosion rate and volumetric loss rate of the two materials were compared under electrochemical corrosion and erosion-corrosion in alkaline environment.The results demonstrates that Ti(C,N)-Mo_(2)C-Ni cermet undergoes passivation when exposed to electrochemical corrosion of NaOH solution,resulting in a significant increase in oxygen content on the corroded surface.The corrosion rate of cermet is approximately one order of magnitude lower than that of the cemented carbide.Under the erosion-corrosion of an alkaline sand-water mixture,both the cermet and cemented carbide experience a gradual increase in volumetric loss rate with prolonging the erosion time.During erosion,the rim phase in cermet is fragile,so cracks easily penetrate it while the core phase remains intact.The medium-grained cemented carbide commonly demonstrates transgranular fracture mode,while in the fine-grained cemented carbide,cracks tend to propagate along phase boundaries.The erosive wear and damage caused by sand particles play a predominant role in the erosion-corrosion process of alkaline sand-water mixtures.This process represents an accelerated destructive phenomenon influenced and intensified by the combined effects of corrosion and erosion.It is confirmed that using cermet as an alternative anti-wear material to cemented carbides is feasible under alkaline conditions,and even better.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
The electrochemical corrosion of ductile pipes(DPs)in drinking water distribution systems(DWDS)has a crucial impact on cement-mortar lining(CML)failure and metal release,potentially leading to drinking water quality d...The electrochemical corrosion of ductile pipes(DPs)in drinking water distribution systems(DWDS)has a crucial impact on cement-mortar lining(CML)failure and metal release,potentially leading to drinking water quality deterioration and posing a risk to public health.An in-situ scanning vibrating electrode technique(SVET)with micron-scale resolution,microscopic scale detection and water quality analysis were used to investigate the corrosion behavior and metal release from DPs throughout the whole CML failure process.Metal pollutants release occurred at three different stages of CML failure process,and there are potential risks of water quality deterioration exceeding the maximum allowable levels set by national standards in the partial failure stage and lining peeling stage.Furthermore,the effects of water chemistry(Cl^(−),SO_(4)^(2−),NO_(3)−,and Ca^(2+))on corrosion scale growth and iron release activity,were investigated during the CML partial failure stage.Results showed that the CML failure process in DPs was accelerated by the autocatalysis of localized corrosion.Cl^(−)was found to damage the uncorroded metal surface,while SO_(4)^(2−)mainly dissolved the corrosion scale surface,increasing iron release.Both the oxidation of NO_(3)−and selective sedimentation of Ca2+were found to enhance the stability of corrosion scales and inhibit iron release.展开更多
Using cemented rockfill to replace coal pillars offers an effective solution for reducing solid waste while ensuring the safety of gob-side entries.However,achieving the balance among low cost,high waste recycling rat...Using cemented rockfill to replace coal pillars offers an effective solution for reducing solid waste while ensuring the safety of gob-side entries.However,achieving the balance among low cost,high waste recycling rates,and adequate strength remains a significant challenge for cemented rockfill.This study used a composite alkali activator to activate gangue cemented rockfill.The compressive strength,scanning electron microscopy,energy dispersive spectrometer,mercury intrusion porosimetry,X-ray diffraction,and thermogra-vimetric tests were carried out to investigate the effect of the composite alkali activator proportion on the compressive strength,micro-structure,and composition of the cemented rockfill.The calcium silicate hydrate(C–S–H)molecular model of cemented rockfill was con-structed to explore the fracture evolution of the nucleated molecular structure under tension.The results show that compressive strength initially increased and then decreased with the activator proportion,the optimal activator proportion of 1:2 resulted in a 31.25%increase in strength at 3 d.This reasonable activator proportion strengthens the pozzolanic effect of gangue,and consumes more calcium hydroxide to inhibit its agglomeration,ultimately achieving the densification of microstructure.The activator proportion inevitably substitutes calcium ions with sodium ions in the C–S–H molecular model.The 12%substitution of calcium ions increases the adhesion between silicon chain layers,which is beneficial to the interlayer stress transfer.This work proposes a method for preparing low-cost cemented rockfill from al-kali-activated gangue,which can be used for solid waste recycling and reducing cement consumption to achieve low-carbon goals.展开更多
To tackle the common issue of green defects in material extrusion(MEX)additive manufacturing(AM)cemented carbides,warm isostatic pressing(WIP)was introduced to eliminate defects of MEX WC-9Co cemented carbide greens,t...To tackle the common issue of green defects in material extrusion(MEX)additive manufacturing(AM)cemented carbides,warm isostatic pressing(WIP)was introduced to eliminate defects of MEX WC-9Co cemented carbide greens,thereby improving both microstructure uniformity and mechanical properties of sintered bodies.The results indicate that WIP reduces defects in MEX greens,thus decreasing the dimensions and numbers of defects,modifying shapes of pores within sintered bodies,while preserving surface quality and shape characteristics.Compared with WC-9Co prepared via MEX followed by debinding and sintering(DS),the hardness of WC-9Co prepared using MEX-WIP-DS does not change significantly,ranging HV_(30)1494-1508,the transverse rupture strength increases by up to 49.3%,reaching 2998-3514 MPa,and the fracture toughness remains high,ranging 14.8-17.0 MPa·m^(1/2).The mechanical properties surpass comparable cemented carbides fabricated through other AM methods and are comparable to those produced by powder metallurgy.The integration of green WIP into MEX-DS broadens the MEX processing window,and improves the overall mechanical properties of MEX AM WC-Co cemented carbides.展开更多
Natural cemented calcareous sand and limestone are highly complex and not well understood in terms of the me-chanical behavior due to the difficulty of obtaining undisturbed samples from far sea.This paper proposes an...Natural cemented calcareous sand and limestone are highly complex and not well understood in terms of the me-chanical behavior due to the difficulty of obtaining undisturbed samples from far sea.This paper proposes an artificial method in a laboratory setting using microbial-induced carbonate precipitation(MICP)to simulate the natural process of cementation of limestone.The artificially cemented sand has a high degree of similarity with the natural weakly limestone in three aspects:(1)the mineral composition of the cemented material is also granular calcite and acicular aragonite;(2)the microstructure in interconnected open pore network can be gradually closed and contracted with cementation.The porosity reaches to approximately 9.2%;(3)both the stress-strain relationship and the unconfined strength closely resemble that of natural weakly limestone.Furthermore,both static and dynamic behaviors of artificial limestone were studied by quasi-static compression tests and Split Hopkinson Pressure Bar(SHPB)tests,finding that the unconfined strength of weakly artifical limestone exponentially increases with increasing strain rate.A rate-dependent bond strength was proposed and implemented in software to reveal the mechanism of strain rate effects.It is found that the loading velocity is too high to keep in sync with the initiation and propagation of cracks under impact loading.This delay-induced viscosity may restrict the movement of the surrounding balls,thus increasing resistance.展开更多
At present,carbon capture and storage(CCS)is the only mature and commercialized technology capable of effectively and economically reducing greenhouse gas emissions to achieve a significant and immedi-ate impact on th...At present,carbon capture and storage(CCS)is the only mature and commercialized technology capable of effectively and economically reducing greenhouse gas emissions to achieve a significant and immedi-ate impact on the CO_(2) level on Earth.Notably,long-term geological storage of captured CO_(2) has emerged as a primary storage method,given its minimal impact on surface ecological environments and high level of safety.The integrity of CO_(2) storage wellbores can be compromised by the corrosion of steel casings and degradation of cement in supercritical CO_(2) storage environments,potentially leading to the leakage of stored CO_(2) from the sites.This critical review endeavors to establish a knowledge foundation for the cor-rosion and materials degradation associated with geological CO_(2) storage through an in-depth examina-tion and analysis of the environments,operation,and the state-of-the-art progress in research pertaining to the topic.This article discusses the physical and chemical properties of CO_(2) in its supercrit-ical phase during injection and storage.It then introduces the principle of geological CO_(2) storage,consid-erations in the construction of storage systems,and the unique geo-bio-chemical environment involving aqueous media and microbial communities in CO_(2) storage.After a comprehensive analysis of existing knowledge on corrosion in CO_(2) storage,including corrosion mechanisms,parametric effects,and corro-sion rate measurements,this review identifies technical gaps and puts forward potential avenues for fur-ther research in steel corrosion within geological CO_(2) storage systems.展开更多
The effects of liquid-solid ratio and reaction time on the leaching rate of magnesium at room temperature were investigated,as well as the effects of the molar ratio of MgO/MgCl_(2),the amount of water added,and the a...The effects of liquid-solid ratio and reaction time on the leaching rate of magnesium at room temperature were investigated,as well as the effects of the molar ratio of MgO/MgCl_(2),the amount of water added,and the amount of acid-impregnated slag dosed on the compressive strength and water resistance of LR-MOC.The results showed that the magnesium element in the boron mud could be maximally leached under the conditions of 1:1 concentration of hydrochloric acid at room temperature,liquid-solid ratio of 2.5 mL·g^(-1),and reaction time of 5 h,and the main products were amorphous SiO_(2) as well as a small amount of magnesium olivine which had not been completely reacted.The LR-MOC prepared using the acid-soaked mixture could reach a softening coefficient of 0.85 for 28 d of water immersion when the molar ratio of MgO/MgCl_(2) was 2.2,the amount of water added was 0 g,and the acid-soaked slag dosing was 40 wt%,which also led to an appreciable late-strength,with an increase of 19.4%in compressive strength at 28 d compared to that at 7 d.Unlike previous studies,LR-MOC prepared in this way has a final strength phase that is not the more easily hydrolysed 3-phase but the lath-like 5-phase.For this phenomenon,we analyzed the mechanism and found that,during the acid leaching process,a part of amorphous SiO_(2) dissolved in the acid leaching solution formed a silica sol,in which Mg^(2+)played a bridging role to make the silica sol more stable.With the addition and hydrolysis of MgO,the silica sol gel coagulation slows down,providing a capping layer to inhibit the hydrolysis of the 5-phase crystals and providing some strength after coagulation.The amorphous SiO_(2) in the other part of the acid-impregnated slag generated M-S-H gel with Mg^(2+)and OH-,which synergised with the dense structure composed of interlocking crystals to improve the water resistance of LR-MOC.展开更多
Paste and mortar specimens were prepared with sulfoaluminate cement(SAC),P⋅O 42.5 ordinary Portland cement(OPC),and standard sand,and mixed and cured with pure water and artificial seawater,respectively.The mechanical...Paste and mortar specimens were prepared with sulfoaluminate cement(SAC),P⋅O 42.5 ordinary Portland cement(OPC),and standard sand,and mixed and cured with pure water and artificial seawater,respectively.The mechanical properties of mortar specimens were tested.Hydration and microstructure of paste specimens were also investigated using X-ray diffraction(XRD),scanning electron microscope(SEM),and 27Al nuclear magnetic resonance(NMR),respectively.The results indicate that SAC mortar samples mixed and cured by seawater have faster strength growth before 28 d and higher compressive strength than OPC mortar samples.Compared to curing in deionized water,the hydration products of SAC are somewhat coarser when cured in simulated seawater.The evolution of aluminum phase hydration products during the hydration process of SAC mixed and cured in simulated seawater is quite different from that of OPC.From 3 to 28 d,the content of each aluminum phase hydration product in SAC paste cured in simulated seawater changed little,while that in OPC paste changed significantly;for example,from 7 to 28 d,the content of ettringite(AFt)in OPC paste increased significantly.This type of AFt formed loosely,harming the mortar's microstructure.展开更多
The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compressio...The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compression tests,CT scanning,SEM,and EDS tests were conducted on cemented gangue backfill samples(CGBSs)with various carbon nanotube concentrations(P_(CNT))that satisfied fractal theory for the PSD of aggregates.The mechanical properties,energy dissipations,and failure mechanisms of the CGBSs under true triaxial compression were systematically analyzed.The results indicate that appropriate carbon nanotubes(CNTs)effectively enhance the mechanical properties and energy dissipations of CGBSs through micropore filling and microcrack bridging,and the optimal effect appears at P_(CNT)of 0.08wt%.Taking PSD fractal dimension(D)of 2.500 as an example,compared to that of CGBS without CNT,the peak strength(σ_(p)),axial peak strain(ε_(1,p)),elastic strain energy(Ue),and dissipated energy(U_(d))increased by 12.76%,29.60%,19.05%,and90.39%,respectively.However,excessive CNTs can reduce the mechanical properties of CGBSs due to CNT agglomeration,manifesting a decrease inρ_(p),ε_(1,p),and the volumetric strain increment(Δε_(v))when P_(CNT)increases from 0.08wt%to 0.12wt%.Moreover,the addition of CNTs improved the integrity of CGBS after macroscopic failure,and crack extension in CGBSs appeared in two modes:detour and pass through the aggregates.Theσ_(p)and U_(d)firstly increase and then decrease with increasing D,and porosity shows the opposite trend.Theε_(1,p)andΔε_(v)are negatively correlated with D,and CGBS with D=2.150 has the maximum deformation parameters(ε_(1,p)=0.05079,Δε_(v)=0.01990)due to the frictional slip effect caused by coarse aggregates.With increasing D,the failure modes of CGBSs are sequentially manifested as oblique shear failure,"Y-shaped"shear failure,and conjugate shear failure.展开更多
This study aimed to address the challenges of solid waste utilization,cost reduction,and carbon reduction in the treatment of deep-dredged soil at Xuwei Port in Lianyungang city of China.Past research in this area was...This study aimed to address the challenges of solid waste utilization,cost reduction,and carbon reduction in the treatment of deep-dredged soil at Xuwei Port in Lianyungang city of China.Past research in this area was limited.Therefore,a curing agent made from powdered shells was used to solidify the dredged soil in situ.We employed laboratory orthogonal tests to investigate the physical and mechanical properties of the powdered shell-based curing agent.Data was collected by conducting experiments to assess the role of powdered shells in the curing process and to determine the optimal ratios of powdered shells to solidified soil for different purposes.The development of strength in solidified soil was studied in both seawater and pure water conditions.The study revealed that the strength of the solidified soil was influenced by the substitution rate of powdered shells and their interaction with cement.Higher cement content had a positive effect on strength.For high-strength solidified soil,the recommended ratio of wet soil:cement:lime:powdered shells were 100:16:4:4,while for low-strength solidified soil,the recommended ratio was 100:5.4:2.4:0.6.Seawater,under appropriate conditions,improved short-term strength by promoting the formation of expansive ettringite minerals that contributed to cementation and precipitation.These findings suggest that the combination of cement and powdered shells is synergistic,positively affecting the strength of solidified soil.The recommended ratios provide practical guidance for achieving desired strength levels while considering factors such as cost and carbon emissions.The role of seawater in enhancing short-term strength through crystal formation is noteworthy and can be advantageous for certain applications.In conclusion,this research demonstrates the potential of using a powdered shell-based curing agent for solidifying dredged soil in an environmentally friendly and cost-effective manner.The recommended ratios for different strength requirements offer valuable insights for practical applications in the field of soil treatment,contributing to sustainable and efficient solutions for soil management.展开更多
The injection of bone cement is a promising surgical intervention for the treatment of osteoporosis.The aim of this study was to formulate a novel injectable bioactive bone cement to adress such medical problems.The b...The injection of bone cement is a promising surgical intervention for the treatment of osteoporosis.The aim of this study was to formulate a novel injectable bioactive bone cement to adress such medical problems.The bone cement primarily consists of tricalcium phosphate(β-TCP),konjac glucomannan(KGM),and hydroxyapatite whisker(HAw).An orthogonal experiment was designed to generate multiple sets of new composite calcium phosphate cement(NCPC)samples,and their setting times were measured.The in vitro compatibility of the new bone cement was assessed through relative cell proliferation rate(RGR)and in vitro cell growth experiments.Mechanical strength and porosity tests were conducted for each group of bone cement,and cross-sectional morphology was observed.The results demonstrate that the bone cement exhibits favorable properties such as self-curing,mechanical robustness,and resistance to collapse.The optimum formulation involves a doping ratio of 5/15(wt%)HAw and HA,an additional amount of 1.2wt%KGM,and a liquid citric acid concentration of 2wt%.Porosity tests confirmed that the material has high compressive strength and a favorable porosity of 27%,creating conducive conditions for cell growth,proliferation,and material degradation.Moreover,in vitro cell culture experiments revealed excellent biocompatibility of the material.Consequently,the developed NCPC emerges as a potential candidate material for applications of bone implantation.展开更多
基金the financial support of National Natural Science Foundation of China(Grant No.52378392)“Foal Eagle Program”Youth Top-notch Talent Project of Fujian Province(Grant No.00387088)Natural Science Foundation of Fujian Province(Grant No.2020J06013).
文摘Enzyme-induced carbonate precipitation(EICP)has emerged as an innovative soil stabilization technology to precipitate CaCO_(3)by catalyzing urea decomposition.Although extensive efforts have been made to increase the calcium carbonate content(CCC)formed in the EICP process for the better biocementation effect,the cementability and micromechanical properties of CaCO_(3)are rarely known.A study of the cementitious characteristics and micromechanical properties of CaCO_(3)precipitates with different mixing percentages of crystal morphology is essential for soil improvement.In the present study,ultrasonic oscillation tests and nanoindentation tests were performed to investigate the cementability and micromechanical properties of CaCO_(3)precipitate.The results show that the cementability and micromechanical properties of CaCO_(3)precipitate are related to the composition of the crystal morphology.A high content of calcite is beneficial to improve the adhesion of calcium carbonate precipitate.Calcite has better mechanical properties(elastic modulus,hardness and ductility)than vaterite,and the presence of vaterite can significantly affect the measured value of mechanical properties in nanoindentation tests.The ductility of CaCO_(3)precipitate induced by crude soybean urease(CSU)is higher than that of CaCO_(3)precipitate induced by commercially available pure enzyme,suggesting that commercially available pure enzyme can be replaced by CSU for cost-effective field-scale engineering applications.This work can provide insight into optimizing the properties of CaCO_(3)precipitate from the micro-scale.
基金Funded by the National Natural Science Foundation of China(No.52568032)Guangxi Key Research and Development Program(GKNos.AB24010020,AB23026071,and AD24010062)。
文摘The engineering application of low-alkali sulphoaluminate cement(L-SAC)is hindered due to the difficulty in adjusting the setting and hardening time.In this paper,lithium hydroxide and borax are mixed into L-SAC to regulate its setting and hardening process,so as to prepare a sulphoaluminate concrete material with high early strength and high fluidity.The effects of the ratio of lithium hydroxide to borax on the properties of L-SAC concrete were studied by hydration heat,XRD,TG-DTG,SEM and MIP.The experimental results show that the slump increases with the increase of borax content,and the early(3 h)strength increases with the increase of lithium hydroxide content.When 0.05% lithium hydroxide and 0.4% borax are added,the 0.5 h slump reaches 195 mm,and the 3 h compressive strength reaches 15.9 MPa.The increase of lithium hydroxide will promote the formation of early hydration products AFt and AH3 gel and accelerate the hydration process,while borax will inhibit the dissolution and hydration of cement and delay the setting and hardening process of concrete.The combination of the two ensures that the concrete has the characteristics of high early strength and high fluidity,and the early workability and mechanical properties can be controlled by the mix ratio.For long-term mechanical properties,the special concrete does not produce AFm,which can ensure the continuous development of strength.
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Funded by Hainan Provincial Natural Science Foundation(No.522QN279)State Key Laboratory of High Performance Civil Engineering Materials(No.2023CEM004)。
文摘A green pregelatinized glutinous rice flour biological admixture was developed in this paper.The cement hydration process,hydration products,pore structure,and strength of mortar with different quantities of glutinous rice flour(GRF),and the macroscopic changes in concrete cracking resistance testing were investigated.Simultaneously,a fast cracking resistance evaluation method based on graphic recognition was proposed.The results indicated that pregelatinized glutinous rice flour(T-GRF)delayed the dissolution rate of anhydrous cement during the induction period,shifting the main exothermic peak of hydration backward.The compressive strength developed slowly in 7-28 d age and returned to normal in 28-56 d.The compressive strength of T-GRF-0.6% modified mortar at 56 d age is less than 10% different from that of control group.The 3.0%T-GRF decreased the total porosity by 3%,and the average pore size decreased from 31.2 to 21.3 nm measured by MIP,indicating that T-GRF could inhibit harmful pores and densify concrete.The crack resistance coefficient of T-GRF modified concrete was obtained by image recognition method,and the GRF could decrease the length,width,and damaged area of cracks in the early age of concrete.
基金Chongqing Light Alloy Materials and Processing Engineering Technology Research Center Open Fund Project(GCZX201903)Yunnan Province Major Science and Technology Special Project Plan(202302AA310038)Sichuan University-Suining Municipal-University Cooperation Project(2023CDSN-12)。
文摘Ti(C,N)-Mo_(2)C-Ni cermet as alternative materials was explored for use in alkaline conditions,replacing the WC-Co cemented carbides,since Co is classified as a potentially carcinogenic substance and there is potential hazard of“hard metal disease”under the exposure to cobalt dust.The changes in microstructure,corrosion rate and volumetric loss rate of the two materials were compared under electrochemical corrosion and erosion-corrosion in alkaline environment.The results demonstrates that Ti(C,N)-Mo_(2)C-Ni cermet undergoes passivation when exposed to electrochemical corrosion of NaOH solution,resulting in a significant increase in oxygen content on the corroded surface.The corrosion rate of cermet is approximately one order of magnitude lower than that of the cemented carbide.Under the erosion-corrosion of an alkaline sand-water mixture,both the cermet and cemented carbide experience a gradual increase in volumetric loss rate with prolonging the erosion time.During erosion,the rim phase in cermet is fragile,so cracks easily penetrate it while the core phase remains intact.The medium-grained cemented carbide commonly demonstrates transgranular fracture mode,while in the fine-grained cemented carbide,cracks tend to propagate along phase boundaries.The erosive wear and damage caused by sand particles play a predominant role in the erosion-corrosion process of alkaline sand-water mixtures.This process represents an accelerated destructive phenomenon influenced and intensified by the combined effects of corrosion and erosion.It is confirmed that using cermet as an alternative anti-wear material to cemented carbides is feasible under alkaline conditions,and even better.
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supported by the National Natural Science Foundation of China(Nos.51808158,52170101,and 52200116)Tianjin Natural Science Foundation(No.23JCYBJC00640).
文摘The electrochemical corrosion of ductile pipes(DPs)in drinking water distribution systems(DWDS)has a crucial impact on cement-mortar lining(CML)failure and metal release,potentially leading to drinking water quality deterioration and posing a risk to public health.An in-situ scanning vibrating electrode technique(SVET)with micron-scale resolution,microscopic scale detection and water quality analysis were used to investigate the corrosion behavior and metal release from DPs throughout the whole CML failure process.Metal pollutants release occurred at three different stages of CML failure process,and there are potential risks of water quality deterioration exceeding the maximum allowable levels set by national standards in the partial failure stage and lining peeling stage.Furthermore,the effects of water chemistry(Cl^(−),SO_(4)^(2−),NO_(3)−,and Ca^(2+))on corrosion scale growth and iron release activity,were investigated during the CML partial failure stage.Results showed that the CML failure process in DPs was accelerated by the autocatalysis of localized corrosion.Cl^(−)was found to damage the uncorroded metal surface,while SO_(4)^(2−)mainly dissolved the corrosion scale surface,increasing iron release.Both the oxidation of NO_(3)−and selective sedimentation of Ca2+were found to enhance the stability of corrosion scales and inhibit iron release.
基金supported by the Key Research and Development Special Tasks of Xinjiang,China (No.2022B01051-2)the National Natural Science Foundation of China (Nos.U23B2091,42372328,and 52478253)+1 种基金the Natural Science Foundation of Jiangsu Province,China (No.BK20240209)the Science and Technology Program Special Fund of Jiangsu Province (Frontier Leading Technology Basic Research) Major projects,China (No.BK 20222004)
文摘Using cemented rockfill to replace coal pillars offers an effective solution for reducing solid waste while ensuring the safety of gob-side entries.However,achieving the balance among low cost,high waste recycling rates,and adequate strength remains a significant challenge for cemented rockfill.This study used a composite alkali activator to activate gangue cemented rockfill.The compressive strength,scanning electron microscopy,energy dispersive spectrometer,mercury intrusion porosimetry,X-ray diffraction,and thermogra-vimetric tests were carried out to investigate the effect of the composite alkali activator proportion on the compressive strength,micro-structure,and composition of the cemented rockfill.The calcium silicate hydrate(C–S–H)molecular model of cemented rockfill was con-structed to explore the fracture evolution of the nucleated molecular structure under tension.The results show that compressive strength initially increased and then decreased with the activator proportion,the optimal activator proportion of 1:2 resulted in a 31.25%increase in strength at 3 d.This reasonable activator proportion strengthens the pozzolanic effect of gangue,and consumes more calcium hydroxide to inhibit its agglomeration,ultimately achieving the densification of microstructure.The activator proportion inevitably substitutes calcium ions with sodium ions in the C–S–H molecular model.The 12%substitution of calcium ions increases the adhesion between silicon chain layers,which is beneficial to the interlayer stress transfer.This work proposes a method for preparing low-cost cemented rockfill from al-kali-activated gangue,which can be used for solid waste recycling and reducing cement consumption to achieve low-carbon goals.
基金supported by the Key Project of Chinese Academy of Engineering(No.2019-XZ-11)the General Project of Chinese Academy of Engineering(No.2023-XY-18)+1 种基金the Open Fund of National Joint Engineering Research Center for Abrasion Control and Molding of Metal Materials of China(No.HKDNM201907)the Independent Project of State Key Laboratory of Powder Metallurgy,China。
文摘To tackle the common issue of green defects in material extrusion(MEX)additive manufacturing(AM)cemented carbides,warm isostatic pressing(WIP)was introduced to eliminate defects of MEX WC-9Co cemented carbide greens,thereby improving both microstructure uniformity and mechanical properties of sintered bodies.The results indicate that WIP reduces defects in MEX greens,thus decreasing the dimensions and numbers of defects,modifying shapes of pores within sintered bodies,while preserving surface quality and shape characteristics.Compared with WC-9Co prepared via MEX followed by debinding and sintering(DS),the hardness of WC-9Co prepared using MEX-WIP-DS does not change significantly,ranging HV_(30)1494-1508,the transverse rupture strength increases by up to 49.3%,reaching 2998-3514 MPa,and the fracture toughness remains high,ranging 14.8-17.0 MPa·m^(1/2).The mechanical properties surpass comparable cemented carbides fabricated through other AM methods and are comparable to those produced by powder metallurgy.The integration of green WIP into MEX-DS broadens the MEX processing window,and improves the overall mechanical properties of MEX AM WC-Co cemented carbides.
基金The authors would like to acknowledge the support of the National Natural Science Foundation of China(No.52279097,No.51779264)Blue and Green Project of Jiangsu Province.
文摘Natural cemented calcareous sand and limestone are highly complex and not well understood in terms of the me-chanical behavior due to the difficulty of obtaining undisturbed samples from far sea.This paper proposes an artificial method in a laboratory setting using microbial-induced carbonate precipitation(MICP)to simulate the natural process of cementation of limestone.The artificially cemented sand has a high degree of similarity with the natural weakly limestone in three aspects:(1)the mineral composition of the cemented material is also granular calcite and acicular aragonite;(2)the microstructure in interconnected open pore network can be gradually closed and contracted with cementation.The porosity reaches to approximately 9.2%;(3)both the stress-strain relationship and the unconfined strength closely resemble that of natural weakly limestone.Furthermore,both static and dynamic behaviors of artificial limestone were studied by quasi-static compression tests and Split Hopkinson Pressure Bar(SHPB)tests,finding that the unconfined strength of weakly artifical limestone exponentially increases with increasing strain rate.A rate-dependent bond strength was proposed and implemented in software to reveal the mechanism of strain rate effects.It is found that the loading velocity is too high to keep in sync with the initiation and propagation of cracks under impact loading.This delay-induced viscosity may restrict the movement of the surrounding balls,thus increasing resistance.
文摘At present,carbon capture and storage(CCS)is the only mature and commercialized technology capable of effectively and economically reducing greenhouse gas emissions to achieve a significant and immedi-ate impact on the CO_(2) level on Earth.Notably,long-term geological storage of captured CO_(2) has emerged as a primary storage method,given its minimal impact on surface ecological environments and high level of safety.The integrity of CO_(2) storage wellbores can be compromised by the corrosion of steel casings and degradation of cement in supercritical CO_(2) storage environments,potentially leading to the leakage of stored CO_(2) from the sites.This critical review endeavors to establish a knowledge foundation for the cor-rosion and materials degradation associated with geological CO_(2) storage through an in-depth examina-tion and analysis of the environments,operation,and the state-of-the-art progress in research pertaining to the topic.This article discusses the physical and chemical properties of CO_(2) in its supercrit-ical phase during injection and storage.It then introduces the principle of geological CO_(2) storage,consid-erations in the construction of storage systems,and the unique geo-bio-chemical environment involving aqueous media and microbial communities in CO_(2) storage.After a comprehensive analysis of existing knowledge on corrosion in CO_(2) storage,including corrosion mechanisms,parametric effects,and corro-sion rate measurements,this review identifies technical gaps and puts forward potential avenues for fur-ther research in steel corrosion within geological CO_(2) storage systems.
基金Funded by Provincial Basic Research Projects(No.LJKMZ20220947)。
文摘The effects of liquid-solid ratio and reaction time on the leaching rate of magnesium at room temperature were investigated,as well as the effects of the molar ratio of MgO/MgCl_(2),the amount of water added,and the amount of acid-impregnated slag dosed on the compressive strength and water resistance of LR-MOC.The results showed that the magnesium element in the boron mud could be maximally leached under the conditions of 1:1 concentration of hydrochloric acid at room temperature,liquid-solid ratio of 2.5 mL·g^(-1),and reaction time of 5 h,and the main products were amorphous SiO_(2) as well as a small amount of magnesium olivine which had not been completely reacted.The LR-MOC prepared using the acid-soaked mixture could reach a softening coefficient of 0.85 for 28 d of water immersion when the molar ratio of MgO/MgCl_(2) was 2.2,the amount of water added was 0 g,and the acid-soaked slag dosing was 40 wt%,which also led to an appreciable late-strength,with an increase of 19.4%in compressive strength at 28 d compared to that at 7 d.Unlike previous studies,LR-MOC prepared in this way has a final strength phase that is not the more easily hydrolysed 3-phase but the lath-like 5-phase.For this phenomenon,we analyzed the mechanism and found that,during the acid leaching process,a part of amorphous SiO_(2) dissolved in the acid leaching solution formed a silica sol,in which Mg^(2+)played a bridging role to make the silica sol more stable.With the addition and hydrolysis of MgO,the silica sol gel coagulation slows down,providing a capping layer to inhibit the hydrolysis of the 5-phase crystals and providing some strength after coagulation.The amorphous SiO_(2) in the other part of the acid-impregnated slag generated M-S-H gel with Mg^(2+)and OH-,which synergised with the dense structure composed of interlocking crystals to improve the water resistance of LR-MOC.
基金Funded by Science and Technology Development Project of China Railway Design Corporation(Nos.2023A0226407,2023B03040003)。
文摘Paste and mortar specimens were prepared with sulfoaluminate cement(SAC),P⋅O 42.5 ordinary Portland cement(OPC),and standard sand,and mixed and cured with pure water and artificial seawater,respectively.The mechanical properties of mortar specimens were tested.Hydration and microstructure of paste specimens were also investigated using X-ray diffraction(XRD),scanning electron microscope(SEM),and 27Al nuclear magnetic resonance(NMR),respectively.The results indicate that SAC mortar samples mixed and cured by seawater have faster strength growth before 28 d and higher compressive strength than OPC mortar samples.Compared to curing in deionized water,the hydration products of SAC are somewhat coarser when cured in simulated seawater.The evolution of aluminum phase hydration products during the hydration process of SAC mixed and cured in simulated seawater is quite different from that of OPC.From 3 to 28 d,the content of each aluminum phase hydration product in SAC paste cured in simulated seawater changed little,while that in OPC paste changed significantly;for example,from 7 to 28 d,the content of ettringite(AFt)in OPC paste increased significantly.This type of AFt formed loosely,harming the mortar's microstructure.
基金financially supported by the National Natural Science Foundation of China(Nos.52174092,51904290,and 52374147)the Natural Science Foundation of Jiangsu Province,China(No.BK20220157)+2 种基金the Fundamental Research Funds for the Central Universities,China(No.2022YCPY0202)the National Key Research and Development Program of China(No.2023YFC3804204)the Major Program of Xinjiang Uygur Autonomous Region S cience and Technology(No.2023A01002)。
文摘The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compression tests,CT scanning,SEM,and EDS tests were conducted on cemented gangue backfill samples(CGBSs)with various carbon nanotube concentrations(P_(CNT))that satisfied fractal theory for the PSD of aggregates.The mechanical properties,energy dissipations,and failure mechanisms of the CGBSs under true triaxial compression were systematically analyzed.The results indicate that appropriate carbon nanotubes(CNTs)effectively enhance the mechanical properties and energy dissipations of CGBSs through micropore filling and microcrack bridging,and the optimal effect appears at P_(CNT)of 0.08wt%.Taking PSD fractal dimension(D)of 2.500 as an example,compared to that of CGBS without CNT,the peak strength(σ_(p)),axial peak strain(ε_(1,p)),elastic strain energy(Ue),and dissipated energy(U_(d))increased by 12.76%,29.60%,19.05%,and90.39%,respectively.However,excessive CNTs can reduce the mechanical properties of CGBSs due to CNT agglomeration,manifesting a decrease inρ_(p),ε_(1,p),and the volumetric strain increment(Δε_(v))when P_(CNT)increases from 0.08wt%to 0.12wt%.Moreover,the addition of CNTs improved the integrity of CGBS after macroscopic failure,and crack extension in CGBSs appeared in two modes:detour and pass through the aggregates.Theσ_(p)and U_(d)firstly increase and then decrease with increasing D,and porosity shows the opposite trend.Theε_(1,p)andΔε_(v)are negatively correlated with D,and CGBS with D=2.150 has the maximum deformation parameters(ε_(1,p)=0.05079,Δε_(v)=0.01990)due to the frictional slip effect caused by coarse aggregates.With increasing D,the failure modes of CGBSs are sequentially manifested as oblique shear failure,"Y-shaped"shear failure,and conjugate shear failure.
基金Funded by the Science and Technology Project of Jiangsu Provincial Transportation Department(No.2022Y13)。
文摘This study aimed to address the challenges of solid waste utilization,cost reduction,and carbon reduction in the treatment of deep-dredged soil at Xuwei Port in Lianyungang city of China.Past research in this area was limited.Therefore,a curing agent made from powdered shells was used to solidify the dredged soil in situ.We employed laboratory orthogonal tests to investigate the physical and mechanical properties of the powdered shell-based curing agent.Data was collected by conducting experiments to assess the role of powdered shells in the curing process and to determine the optimal ratios of powdered shells to solidified soil for different purposes.The development of strength in solidified soil was studied in both seawater and pure water conditions.The study revealed that the strength of the solidified soil was influenced by the substitution rate of powdered shells and their interaction with cement.Higher cement content had a positive effect on strength.For high-strength solidified soil,the recommended ratio of wet soil:cement:lime:powdered shells were 100:16:4:4,while for low-strength solidified soil,the recommended ratio was 100:5.4:2.4:0.6.Seawater,under appropriate conditions,improved short-term strength by promoting the formation of expansive ettringite minerals that contributed to cementation and precipitation.These findings suggest that the combination of cement and powdered shells is synergistic,positively affecting the strength of solidified soil.The recommended ratios provide practical guidance for achieving desired strength levels while considering factors such as cost and carbon emissions.The role of seawater in enhancing short-term strength through crystal formation is noteworthy and can be advantageous for certain applications.In conclusion,this research demonstrates the potential of using a powdered shell-based curing agent for solidifying dredged soil in an environmentally friendly and cost-effective manner.The recommended ratios for different strength requirements offer valuable insights for practical applications in the field of soil treatment,contributing to sustainable and efficient solutions for soil management.
文摘The injection of bone cement is a promising surgical intervention for the treatment of osteoporosis.The aim of this study was to formulate a novel injectable bioactive bone cement to adress such medical problems.The bone cement primarily consists of tricalcium phosphate(β-TCP),konjac glucomannan(KGM),and hydroxyapatite whisker(HAw).An orthogonal experiment was designed to generate multiple sets of new composite calcium phosphate cement(NCPC)samples,and their setting times were measured.The in vitro compatibility of the new bone cement was assessed through relative cell proliferation rate(RGR)and in vitro cell growth experiments.Mechanical strength and porosity tests were conducted for each group of bone cement,and cross-sectional morphology was observed.The results demonstrate that the bone cement exhibits favorable properties such as self-curing,mechanical robustness,and resistance to collapse.The optimum formulation involves a doping ratio of 5/15(wt%)HAw and HA,an additional amount of 1.2wt%KGM,and a liquid citric acid concentration of 2wt%.Porosity tests confirmed that the material has high compressive strength and a favorable porosity of 27%,creating conducive conditions for cell growth,proliferation,and material degradation.Moreover,in vitro cell culture experiments revealed excellent biocompatibility of the material.Consequently,the developed NCPC emerges as a potential candidate material for applications of bone implantation.
