In order to explore the leaching law of different elements in the composite cementitious system composed of ferrous extraction tailing of nickel slag(FETNS)and ordinary Portland cement(OPC),element leaching test under...In order to explore the leaching law of different elements in the composite cementitious system composed of ferrous extraction tailing of nickel slag(FETNS)and ordinary Portland cement(OPC),element leaching test under different influencing factors was designed with the aid of ICP-OES,XRD,and SEM-EDS.The experimental results show that,with the extension of leaching time,the continuous hydration reaction in the system enables the leaching amount of Si,Al,Mg,and Ca elements to show an overall downward trend.In the alkaline environment,the more sufficient hydration reaction consumes more soluble elements,resulting in a significantly smaller leaching amount than that in the neutral environment.Temperature is also an important factor affecting the leaching of elements.The rise of temperature promotes the dissolution of amorphous phases Si,Al,and Mg in the system,leading to increased leaching amount and higher consumption of C_(2)S and C_(3)S,generating more reaction products.In addition,the content and fineness of FETNS also have a significant effect on the element leaching of the composite cementitious system.More importantly,this paper clarifies the leaching safety of internal heavy metal elements when FETNS is used under the above conditions,which provides a scientific guarantee for the safe and efficient application of FETNS in building materials.展开更多
In order to make clear the interaction mechanism of single component epoxy in cementitious environment, the interaction between epoxy resin and active silanol, epoxy resin and alkali was investigated From solid-state ...In order to make clear the interaction mechanism of single component epoxy in cementitious environment, the interaction between epoxy resin and active silanol, epoxy resin and alkali was investigated From solid-state 13C NMR and FT-IR tests, it is confirmed that silanol group can initiate epoxy resin. Test results have also revealed that alkali as the dominant product of cement hydration can open the epoxide ring making epoxy harden.展开更多
Single-component epoxy cement system is an interesting material used in construction engineering, and it is different from traditional two-component epoxy-cement system. We studied the interaction mechanism of single-...Single-component epoxy cement system is an interesting material used in construction engineering, and it is different from traditional two-component epoxy-cement system. We studied the interaction mechanism of single-component epoxy-cement system only in the range of macro mechanical performances, and used the cement and single-component epoxy directly to investigate the interaction between the both. Solidstate 13 C NMR, FT-IR, Raman spectroscopy and XRD were employed to trace the change of the system. Results showed that the epoxide rings in cementitious environment had been opened by cement ingredients. It was true that single-component epoxy could be used as reactive additive in cementitious system.展开更多
Polymer modification in the field of construction engineering has a history nearly 90 years. Mechanical properties, water resistance, chemical resistance and durability to some extent have been improved by different p...Polymer modification in the field of construction engineering has a history nearly 90 years. Mechanical properties, water resistance, chemical resistance and durability to some extent have been improved by different polymer modification although those modifications are classified into physical modification. To obtain better performance of cementitious materials, chemical modifications have been tested. In this study, epoxy has been designed as a predominant modifier in the modified system with its corresponding hardener. Amino sulfonate, the additive, has been used to improve the system＇s workability. Functional silane, as it has special functional groups, was used to set up the connections among epoxy, cement moiety and amino sulfonate. The investigation carried out by IR, Raman spectroscopy, DSC and NMR reveals that the chemical connections have been set up among all the components in the modified system. Flexural tests results present the good effect of the chemical modification as the flexural strength and strain have been improved substantially.展开更多
To address the inefficient utilization of electrolytic manganese residue(EMR)caused by its high inert content,this study developed a multifunctional solid waste cementitious material by replacing 50-60%of ordinary Por...To address the inefficient utilization of electrolytic manganese residue(EMR)caused by its high inert content,this study developed a multifunctional solid waste cementitious material by replacing 50-60%of ordinary Portland cement(PO 42.5)with wet-ground electrolytic manganese residue(WEMR),wetground granulated blast-furnace slag(WGBFS),and carbide slag(CS).The mechanical properties,hydration characteristics,microstructure,and carbon emissions of the material were systematically investigated with varying WEMR dosages.The experimental results demonstrates that the wet-grinding process significantly refines the particle size and enhances the reactivity of both EMR and GBFS.As the WEMR dosage increases,the 28-day compressive strength initially rise and then declines.Optimal mechanical performance was achieved with 24%WEMR and 6%CS,yielding a 28-day compressive strength of 48.2 MPa.Advanced analytical techniques,including XRD,TG-DTG,SEM,and MIP,were employed to examine the hydration products.The findings reveal that the wet-grinding-alkali-sulfur synergistic activation system in the multi-solid waste cementitious material effectively utilize EMR to generate abundant hydration products such as AFt and C-(A)-S-H.Additionally,the fine particles of WEMR fill the pores in the mortar,further enhancing compressive strength.The cost and carbon emissions of this multifunctional system are only 65.97%and 46.9% of those of PO 42.5,respectively.This study provides a feasible approach for the efficient utilization of EMR,contributing to sustainable construction practices.展开更多
In this paper,the effect of usage of the permeability reducing admixture(PRA)having different action mechanisms on hardened state properties of cementitious systems containing mineral additives is examined.For this ai...In this paper,the effect of usage of the permeability reducing admixture(PRA)having different action mechanisms on hardened state properties of cementitious systems containing mineral additives is examined.For this aim,three commercial PRAs were used during investigation.The effective parameters in the first and third PRAs were air-entraining and high-rate air-entraining,respectively.The second one contained the insoluble calcium carbonate residue and had a small amount of the air-entraining property.Mortar mixes with binary and ternary cementitious systems were prepared by partially replacing cement with fly ash and metakaolin.The hardened state properties of mortar mixtures such as compressive strength,ultrasonic pulse velocity,water absorption,drying shrinkage and freeze-thaw resistance were investigated.The ternary cement-based mixture having both fly ash and metakaolin was selected as the most successful mineral-additive bearing mix in regard to hardened state properties.In this sense,PRA-B,with both insoluble residues and a small amount of air-entraining properties,showed the best performance among the mixtures containing PRA.The combined use of mineral additive and PRA had a more positive effect on the properties of the mixes.展开更多
Electrical impedance measurements were performed on fine-grained concrete with low volume content of conductive steel and carbon fibres, either as a mono or as a hybrid system. The influences were investigated of the...Electrical impedance measurements were performed on fine-grained concrete with low volume content of conductive steel and carbon fibres, either as a mono or as a hybrid system. The influences were investigated of the applied frequencies, of fibre combinations and of the age of the composites on the impedance. The results show that when the applied frequency is increased from 0.98 Hz to 1000 Hz, the impedance of the fibre composites significantly decreases. At the same time, impedance difference between plain concrete and fibre-reinforced concrete is enhanced. Dramatic drop of impedance takes place over the low frequency range, i.e. 0.98 to approximately 31 Hz. Impedance also depends on the volume content of hybrid fibres. The cementitious composite with the highest content of hybrid fibres (1.0% steel fibres and 0.2% carbon fibres by volume) has the lowest impedance at all measuring frequencies. 0.6% fibres by volume seem to be a turning point, from which the variation of impedance slows down with the fibre content increases. On the other hand, the impedance increment of the fibre-reinforced composites slows down with the age after 28 days, comparing to plain concrete. (Author abstract) 8 Refs.展开更多
Carbon fibre,steel fibre and graphite were used as conductive fillers to prepare cementitious materials with excellent electrothermal properties.The electrically conductive cementitious materials with different volume...Carbon fibre,steel fibre and graphite were used as conductive fillers to prepare cementitious materials with excellent electrothermal properties.The electrically conductive cementitious materials with different volume dosages were analysed through compressive and flexural strength,electrochemical impedance spectroscopy and temperature rise tests.An equivalent circuit model was established to study the electrically conductive heat generation mechanism in the electrically conductive cementitious composites.The results indicate that the mechanical properties of cementitious composite materials with a ternary conductive phase are better than those of pristine cementitious materials because the fibrous filler improves their mechanical properties.However,the incorporation of graphite in the material reduces its strength.Introducing fibrous and point-like conductive phase materials into the cementitious material enhances the overall conductive pathway and considerably reduces the electrical resistance of the cementitious material,enhancing its conductive properties.The volume ratios of carbon fibre,steel fibre and graphite that achieve an optimal complex doping in the cementitious material were 0.35%,0.6%and 6%,respectively.This was determined using the mutation point of each circuit element parameter as the percolation threshold.In addition,at a certain safety voltage,there is a uniform change between the internal and surface temperatures of the conductive cementitious material,and the heating effect in this materialis is considerably better than that in the pristine cementitious material.展开更多
In order to improve the damage resistance of concrete,a cement-based self-healing additive(abbreviate as CS)was prepared.To investigate the influence of CS on the self-healing performance of cementitious material,X-ra...In order to improve the damage resistance of concrete,a cement-based self-healing additive(abbreviate as CS)was prepared.To investigate the influence of CS on the self-healing performance of cementitious material,X-ray diffraction(XRD)and thermal analysis were used to investigate the effects of different dosages of CS on the hydration process and hydration products of cementitious material.Compressive strength test and load damage self-healing test were used to show the influence of different amounts of CS on the mechanical properties of concrete.The pore structure distribution of cement paste with different dosages of CS was analyzed using mercury intrusion testing method.The results indicated that different dosages of CS had no effect on the types of hydration products of cementitious material.Adding an appropriate amount of CS can effectively improve the micro pore structure of cement-based materials,reduce the proportion of harmful pores in the structure,and decrease the most probable pore diameter.When microcracks are generated in the structure under load,CS can promote the formation of hydration products inside the structure to fill the microcracks,thereby improving the self-healing performance of cement-based materials.This study provides an idea for improving microcracks and enhancing durability of marine concrete structures.展开更多
This study applied machine learning methods to predict the durability performance(specifically shrinkage and freeze-thaw resistance)of solid waste-activated cementitious materials.It also offered insights for optimizi...This study applied machine learning methods to predict the durability performance(specifically shrinkage and freeze-thaw resistance)of solid waste-activated cementitious materials.It also offered insights for optimizing material formulations through feature impact analysis.The study collected a total of 130 sets of shrinkage data and 106 sets of freeze-thaw data,establishing various models,including BP,GA-BP,SVM,RF,RBF,and LSTM.The results revealed that the SVM model performed the best on the test dataset.It achieved an R^(2) of 0.9358 for shrinkage prediction,with MAE and RMSE values of 0.4644 and 0.6254,respectively.Regarding freeze-thaw quality loss prediction,the R^(2) was 0.9178,with MAE and RMSE values of 0.3139 and 0.5328,respectively.The study analyzed the impact of different features on the outcomes using the SHAP method,highlighting that the alkaline activator dosage,Al_(2)O_(3),SiO_(2),and water glass modulus were critical factors influencing shrinkage,while CaO,water-cement ratio,water,and Al_(2)O_(3) were crucial for freeze-thaw resistance.By investigating feature interactions through single-factor and two-factor analysis,the study proposed recommendations for optimizing material formulations.This research validated the efficacy of machine learning in predicting the durability of solid waste cementitious materials and offered insights for material optimization through feature impact analysis,thereby laying the groundwork for the development of related materials.展开更多
As the second most important solid waste produced by coal-fired power plants,the improper management of coal-fired slag has the potential to result in environmental pollution.It is therefore imperative that high-value...As the second most important solid waste produced by coal-fired power plants,the improper management of coal-fired slag has the potential to result in environmental pollution.It is therefore imperative that high-value utilization pathways for coal-fired slag should be developed.In this study,modified magnesium slag(MMS),produced by a magnesium smelter,was selected as the alkali activator.The activated silica-aluminum solid wastes,namely coal-fired slag(CFS)and mineral powder(MP),were employed as pozzolanic materials in the preparation of alkali-activated cementitious materials.The alkali-activated cementitious materials prepared with 50 wt%MMS,40 wt%CFS and 10 wt%MP exhibited favorable mechanical properties,with a compressive strength of 32.804 MPa in the paste sample cured for 28 d.Then,the activated silica-aluminum solid waste consisting of CFS-MP generated a significant amount of C-S(A)-H gels,AFt,and other products,which were observed to occupy the pore structure of the specimen.In addition,the secondary hydration reaction of CFS-MP occurs in high alkalinity environments,resulting in the formation of a mutually stimulated and promoted reaction system between CFS-MP and MMS,this will subsequently accelerate the hydrolysis reaction of MMS.It is important to emphasize that the amount of MMS in alkali-activated cementitious materials must be strictly regulated to avert the potential issue of incomplete depolymerization-repolymerization of active silica-aluminum solid waste containing CFS-MP.This in turn could have a deleterious impact on the late strength of the cementitious materials.The aim of this work is to improve the joint disposal of MMS,CFS and MP and thereby provide a scientific basis for the development of environmentally friendly and low-carbon modified magnesium slag alkali-activated coal-fired slag based cementitious materials for mine backfilling.展开更多
To investigate the feasibility of applying electrolytic manganese residue(EMR)in cementitious materials,an approach combining high-temperature activation(200,400,600,800 and 1000℃)and mechanical grinding(5 min)was ad...To investigate the feasibility of applying electrolytic manganese residue(EMR)in cementitious materials,an approach combining high-temperature activation(200,400,600,800 and 1000℃)and mechanical grinding(5 min)was adopted to stimulate the EMR activity.We analyzed the effect of calcination temperature on the performance of EMR with the aid of X-ray diffraction(XRD),specific surface area test(BET)and pozzolanic activity test,explored the effects of EMR activation temperature and content(0%,10%,15% and 20%)on the setting time,soundness,drying shrinkage,compressive strength,hydration products of cement-EMR mixed slurry,and assessed the effect of cement hydration on the solidification of harmful NH_(4)^(+)-N and Mn^(2+) in EMR.The research results show that high-temperature calcination can lead to the dehydration,decomposition or crystalline phase transformation of the inert sulfate and other substances in EMR,mechanical grinding can improve its particle distribution,and the coupling of the two can effectively enhance the pozzolanic activity of EMR.The decomposition and recombination of aluminum-silica phase at 800℃ optimized the EMR activity,and the strength activity index(SAI)of EMR at 28 d reached up to 95%.Appropriate calcination temperature and EMR content can ensure the workability of the mixed slurry,and when the EMR calcination temperature was 400-1000℃,the setting time of the mixed slurry under different EMR contents satisfied the specification requirements.When the calcination temperature was 600-1000℃ and EMR content was less than 20%,the soundness of the mixed slurry satisfied the specification requirements.The compressive strength of the mixed slurry increased and then decreased with the increase of activated EMR content,when the EMR content was 10%,the compressive strength of all specimens was optimal and higher than the baseline group;when the activation temperature was 800℃,the C-S-H gel in the mixed slurry interconnected with the rod-like Aft and blocked Ca(OH)_(2),and the 28 d compressive strength was increased by 14%compared with that of the baseline group.The solidification rate of Mn^(2+) in EMR by cement hydration was higher than 99%,and that of NH_(4)^(+)-N was higher than 97%.The leaching toxicity after solidification can meet the requirements of toxic emission.The results of the study may provide theoretical basis for the feasibility of the application of EMR in cementitious materials.展开更多
Molybdenum tailings are the solid waste left from ore processing,which damages soil and water resources.To address that,molybdenum tailings(MTs)powder obtained from molybdenum tailings sands was processed as an admixt...Molybdenum tailings are the solid waste left from ore processing,which damages soil and water resources.To address that,molybdenum tailings(MTs)powder obtained from molybdenum tailings sands was processed as an admixture.Compared with moisture-cured conditions,the influence of MTs on the steam-cured mortar’s mechanical properties,surface and internal pore characteristics,and microscopic morphology was investigated.The results show that steam-cured mortar containing appropriate MTs can still have high early strength.When the content of MTs doesn’t exceed 15%,the mechanical strength of mortar steam-cured for 3 d can reach 85%of that of corresponding mortar moisture-cured for 28 d,and that of mortar steam-cured for 28 d isn’t lower than 90%of that of pure cement mortar.The proportion of harmful pores(HFP)and more harmful pores(MHFP)and most probable pore diameters(MPD)on the mortar surface containing MTs steam-cured for 28 d are significantly decreased.When MTs’content is 15%,the proportion of HFP and MHFP on the surface of paste is decreased by 71.4%and 72.2%,respectively,with MPS decreasing from 12.7 nm to 10.8 nm.SEM analysis shows that the surfaces of steam-cured paste containing 15%MTs have more hydration products and dense microstructures.The effect of pozzolanic and dense filling of MTs effectively refines the pore structure,reducing the large pore-size pores.展开更多
The rapid change in CO_(2) concentration levels,due to climate change,will lead to a significant reduction in the durability and safety of the vital reinforced concrete(RC)structures.Utilizing supplementary cementitio...The rapid change in CO_(2) concentration levels,due to climate change,will lead to a significant reduction in the durability and safety of the vital reinforced concrete(RC)structures.Utilizing supplementary cementitious materials,such as low calcium fly ash(LCFA)or slag,etc.,with larger percentages in concrete mixes,would lead to an increase in the carbonation depth and risk of corrosion,especially for cracked concrete sections subjected to severe CO_(2) concentration levels.This research aims to compare the carbonation depth values using two different mathematical models across various CO_(2) concentrations and crack widths,for concrete mixes composed of different percentages and types of fly ash for both uncracked and cracked RC members,at a specific time of CO_(2) exposure.Moreover,the main objective is to assess the probability of corrosion(PC)across various percentages and types of fly ash used in cracked RC decks subjected to a severe CO_(2) level.The PC would be investigated through the Montecarlo simulation method.A Crack width of 0.1 mm in the RC decks would lead to a severe impact on the PC conducted using the Al-Ameeri model compared to the Kwon and Na model,when the percentages of LCFA vary from 5%to 30%in concrete mixes.It is recommended in this research to reduce the amount of high calcium fly ash in the mixes for RC decks to a percentage below 15%instead of LCFA to inhibit the carbonation-induced corrosion and enhance the durability and serviceability of RC structures.展开更多
Understanding the differences in CO_(2)adsorption in cementitious material is critical in mitigating the carbon footprint of the construction industry.This study chose the most common β-C_(2)S phase in the industry a...Understanding the differences in CO_(2)adsorption in cementitious material is critical in mitigating the carbon footprint of the construction industry.This study chose the most common β-C_(2)S phase in the industry as the cementitious material,selecting the β-C_(2)S(111)and β-C_(2)S(100)surfaces for CO_(2)adsorption.First-principles calculations were employed to systematically compare the CO_(2)ad-sorption behaviors on both surfaces focusing on adsorption energy,adsorption configurations,and surface reconstruction.The comparis-on of CO_(2)and H2O adsorption behaviors on the β-C_(2)S(111)surface was also conducted to shed light on the influence of CO_(2)on cement hydration.The adsorption energies of CO_(2)on the β-C_(2)S(111)and β-C_(2)S(100)surfaces were determined as-0.647 and-0.423 eV,respect-ively,suggesting that CO_(2)adsorption is more energetically favorable on the β-C_(2)S(111)surface than on the β-C_(2)S(100)surface.The ad-sorption energy of H2O on the β-C_(2)S(111)surface was-1.588 eV,which is 0.941 eV more negative than that of CO_(2),implying that β-C_(2)S tends to become hydrated before reacting with CO_(2).Bader charges,charge density differences,and the partial density of states were ap-plied to characterize the electronic properties of CO_(2)and H2O molecules and those of the surface atoms.The initial Ca/O sites on the β-C_(2)S(111)surface exhibited higher chemical reactivity due to the greater change in the average number of valence electrons in the CO_(2)ad-sorption.Specifically,after CO_(2)adsorption,the average number of valence electrons for both the Ca and O atoms increased by 0.002 on the β-C_(2)S(111)surface,while both decreased by 0.001 on the β-C_(2)S(100)surface.In addition,due to the lower valence electron number of O atoms,the chemical reactivity of O atoms on the β-C_(2)S(111)surface after H2O adsorption was higher than the case of CO_(2)adsorption,which favors the occurrence of further reactions.Overall,this work assessed the adsorption capacity of the β-C_(2)S surface for CO_(2)mo-lecules,offering a strong theoretical foundation for the design of novel cementitious materials for CO_(2)capture and storage.展开更多
The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully rep...The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully replace natural fine aggregates was investigated.The results indicated that a 50% FA content significantly increased the compressive strength of RFA-HDCC by 13.93%.However,a?further increase in FA content led to a drastic decrease.The increased fly ash content substantially reduced the flexural and tensile strength;however,it markedly increased the matrix strain capacity,resulting in a 53.73% increase in the peak strain when FA was raised to 70%.Regarding durability,the increase in FA content negatively affected the chloride ion permeability and carbonation resistance.However,the increase in FA content initially improved the frost resistance of RFA-HDCC,peaking at 50% FA and deteriorating at 60% and 70% FA content.展开更多
In order to avoid the waste of iron caused by the direct use of ferronickel slag(FNS)in building materials,the effects of reduction iron extraction on the physical and chemical properties,cementitious reactivity and h...In order to avoid the waste of iron caused by the direct use of ferronickel slag(FNS)in building materials,the effects of reduction iron extraction on the physical and chemical properties,cementitious reactivity and hydration reaction characteristics of FNS and ferrum extraction tailing of nickel slag(FETNS)were studied.The experimental results show that the reduction ferrum extraction method changes the mineral phase composition of the waste slag,breaks the Si-O-Si bond,forms the tetrahedral structure of Si-O-NBO or Si-O-2NBO,and increases the content of active components such as Ca,Si,Mg,and Al.Compared with FNS,the 28 d compressive strength of pastes prepared by FETNS increases by 16.12%,22.57%,33.13%,44.26%,and 57.65%,respectively.The degree of hydration reaction of the composite cementitious systems in the FETNS group is higher than that in the FNS group at different ages,and the content of hydration products such as C-S-H gel and ettringite(AFt)is also higher than that in the FNS group.More hydration products can improve the curing ability to Cr and Mn of the composite cementitious systems in the FETNS group,and reduce the leaching value of Cr and Mn.展开更多
A solid,fast-dissolving sodium silicate was used as an alkaline activator.Granulated blast furnace slag(GGBS),metakaolin(MK),and steel slag(SS)were used as the cementious components to prepare a ternary composite ceme...A solid,fast-dissolving sodium silicate was used as an alkaline activator.Granulated blast furnace slag(GGBS),metakaolin(MK),and steel slag(SS)were used as the cementious components to prepare a ternary composite cementitious material known as alkali-activated steel slag composite cementitious material(ASCM)by the"one-step method".The impacts of cementitious components,alkali activator modulus,and Na_(2)O%on the mechanical strength were investigated,and the hydration products and hydration kinetics of ASCM were analyzed.The experimental results reveal that XRD,FTIR,SEM,EDS,and exothermic heat of hydration show that when GGBS:MK:SS=60wt%:10wt%:30wt%,the activator modulus is 1.2,and the alkali content is 5.5wt%,the 28 d flexural strength of ASCM mortar is 12.6 MPa,and the compressive strength is 53.3 MPa,the hydration products consist of C-S-H gel/C-A-S-H gel,mullite(3Al_(2)O_(3)-2SiO_(2)),calcite(CaCO_(3)),quartz,etc.ASCM has a large initial hydration exotherm rate but a small cumulative exotherm.展开更多
A TiO2 photocatalyst is coated on the surface of a zeolite fly ash bead（ZFAB） to improve its dispersability and exposure degree in a cement system.The application of Ag particles in TiO2/ZFAB modified cementitious m...A TiO2 photocatalyst is coated on the surface of a zeolite fly ash bead（ZFAB） to improve its dispersability and exposure degree in a cement system.The application of Ag particles in TiO2/ZFAB modified cementitious materials is to further enhance the photocatalytic performance.Various Ag@TiO2/ZFAB modified cementitious specimens with different Ag dosages are prepared and the characteristics and photocatalytic performance of the prepared samples are investigated.It is observed that the multi-level pore structure of ZFAB can improve the exposure degree of TiO2 in a cement system and is also useful to enhance the photocatalytic efficiency.With an increment of the amounts of Ag particles in the TiO2/ZFAB modified cementitious samples,the photocatalytic activities increased first and then decreased.The optimal Ag@TiO2/ZFAB modified cementitious sample reveals the maximum reaction rate constant for degrading benzene（9.91×10^-3 min^-1）,which is approximately 3 and 10 times higher than those of TiO2/ZFAB and TiO2 modified samples,respectively.This suggests that suitable Ag particles coupled with a ZFAB carrier could effectively enhance the photocatalytic effects and use of TiO2 in a cement system.Thus,ZFAB as a carrier could provide a potential method for a high efficiency engineering application of TiO2 in the construction field.展开更多
To investigate the flexural behaviors of steel reinforced engineered cementitious composite （ECC） beams, the behaviors of the steel reinforced ECC beam and the conventional steel reinforced concrete beam subjected t...To investigate the flexural behaviors of steel reinforced engineered cementitious composite （ECC） beams, the behaviors of the steel reinforced ECC beam and the conventional steel reinforced concrete beam subjected to flexural load are experimentally compared. The experimental results show that the flexural strength and ductility of the steel reinforced ECC beam are 24.8% and 187.67% times larger than those of the steel reinforced concrete beam, and the substitution of concrete with ECC can significantly delay the propagation of cracks. Additionally, a simplified constitutive model of the ECC material is used to simulate the flexural behaviors of beams by the finite element analysis （FEA）. The results show a good agreement between the simulation and test results. The crack width of the steel reinforced ECC beam can be limited to 0.4 mm under the service load conditions. The application of ductile ECC can significantly increase the flexural performance in terms of flexural strength, deformation capacity and ductility of the beams.展开更多
基金Funded by the Science and Technology Program of Gansu Province(Nos.23JRRA799 and 24JRRA213)the National Natural Science Foundation of China(Nos.52178216,52008196,and U21A20150)。
文摘In order to explore the leaching law of different elements in the composite cementitious system composed of ferrous extraction tailing of nickel slag(FETNS)and ordinary Portland cement(OPC),element leaching test under different influencing factors was designed with the aid of ICP-OES,XRD,and SEM-EDS.The experimental results show that,with the extension of leaching time,the continuous hydration reaction in the system enables the leaching amount of Si,Al,Mg,and Ca elements to show an overall downward trend.In the alkaline environment,the more sufficient hydration reaction consumes more soluble elements,resulting in a significantly smaller leaching amount than that in the neutral environment.Temperature is also an important factor affecting the leaching of elements.The rise of temperature promotes the dissolution of amorphous phases Si,Al,and Mg in the system,leading to increased leaching amount and higher consumption of C_(2)S and C_(3)S,generating more reaction products.In addition,the content and fineness of FETNS also have a significant effect on the element leaching of the composite cementitious system.More importantly,this paper clarifies the leaching safety of internal heavy metal elements when FETNS is used under the above conditions,which provides a scientific guarantee for the safe and efficient application of FETNS in building materials.
基金Funded by the National Natural Science Founda-tion of China(No.51578290)
文摘In order to make clear the interaction mechanism of single component epoxy in cementitious environment, the interaction between epoxy resin and active silanol, epoxy resin and alkali was investigated From solid-state 13C NMR and FT-IR tests, it is confirmed that silanol group can initiate epoxy resin. Test results have also revealed that alkali as the dominant product of cement hydration can open the epoxide ring making epoxy harden.
基金Funded by the National Natural Science Foundation of China(No.51578290)
文摘Single-component epoxy cement system is an interesting material used in construction engineering, and it is different from traditional two-component epoxy-cement system. We studied the interaction mechanism of single-component epoxy-cement system only in the range of macro mechanical performances, and used the cement and single-component epoxy directly to investigate the interaction between the both. Solidstate 13 C NMR, FT-IR, Raman spectroscopy and XRD were employed to trace the change of the system. Results showed that the epoxide rings in cementitious environment had been opened by cement ingredients. It was true that single-component epoxy could be used as reactive additive in cementitious system.
基金Funded by the National Basic Research Program of China(973 Program(No.2009CB623200)
文摘Polymer modification in the field of construction engineering has a history nearly 90 years. Mechanical properties, water resistance, chemical resistance and durability to some extent have been improved by different polymer modification although those modifications are classified into physical modification. To obtain better performance of cementitious materials, chemical modifications have been tested. In this study, epoxy has been designed as a predominant modifier in the modified system with its corresponding hardener. Amino sulfonate, the additive, has been used to improve the system＇s workability. Functional silane, as it has special functional groups, was used to set up the connections among epoxy, cement moiety and amino sulfonate. The investigation carried out by IR, Raman spectroscopy, DSC and NMR reveals that the chemical connections have been set up among all the components in the modified system. Flexural tests results present the good effect of the chemical modification as the flexural strength and strain have been improved substantially.
基金Funded by the Guangxi Key Research and Development Program(Nos.GK AB24010020,and GK AB23026071)the Key Project of Guangxi Natural Science Foundation(No.2025GXNSFDA090046)the Guangxi Science and Technology Base and Talent Special Project(No.GK AD24010062)。
文摘To address the inefficient utilization of electrolytic manganese residue(EMR)caused by its high inert content,this study developed a multifunctional solid waste cementitious material by replacing 50-60%of ordinary Portland cement(PO 42.5)with wet-ground electrolytic manganese residue(WEMR),wetground granulated blast-furnace slag(WGBFS),and carbide slag(CS).The mechanical properties,hydration characteristics,microstructure,and carbon emissions of the material were systematically investigated with varying WEMR dosages.The experimental results demonstrates that the wet-grinding process significantly refines the particle size and enhances the reactivity of both EMR and GBFS.As the WEMR dosage increases,the 28-day compressive strength initially rise and then declines.Optimal mechanical performance was achieved with 24%WEMR and 6%CS,yielding a 28-day compressive strength of 48.2 MPa.Advanced analytical techniques,including XRD,TG-DTG,SEM,and MIP,were employed to examine the hydration products.The findings reveal that the wet-grinding-alkali-sulfur synergistic activation system in the multi-solid waste cementitious material effectively utilize EMR to generate abundant hydration products such as AFt and C-(A)-S-H.Additionally,the fine particles of WEMR fill the pores in the mortar,further enhancing compressive strength.The cost and carbon emissions of this multifunctional system are only 65.97%and 46.9% of those of PO 42.5,respectively.This study provides a feasible approach for the efficient utilization of EMR,contributing to sustainable construction practices.
基金This research was financially supported by Bursa Uludag University Scientific Research Projects Center(BAP)with project number SLBÇ(MH)-2017/1The materials used in this study were supplied by Polisan Construction Chemicals Company and Bursa-Beton Ready-Mixed Concrete Plant.
文摘In this paper,the effect of usage of the permeability reducing admixture(PRA)having different action mechanisms on hardened state properties of cementitious systems containing mineral additives is examined.For this aim,three commercial PRAs were used during investigation.The effective parameters in the first and third PRAs were air-entraining and high-rate air-entraining,respectively.The second one contained the insoluble calcium carbonate residue and had a small amount of the air-entraining property.Mortar mixes with binary and ternary cementitious systems were prepared by partially replacing cement with fly ash and metakaolin.The hardened state properties of mortar mixtures such as compressive strength,ultrasonic pulse velocity,water absorption,drying shrinkage and freeze-thaw resistance were investigated.The ternary cement-based mixture having both fly ash and metakaolin was selected as the most successful mineral-additive bearing mix in regard to hardened state properties.In this sense,PRA-B,with both insoluble residues and a small amount of air-entraining properties,showed the best performance among the mixtures containing PRA.The combined use of mineral additive and PRA had a more positive effect on the properties of the mixes.
文摘Electrical impedance measurements were performed on fine-grained concrete with low volume content of conductive steel and carbon fibres, either as a mono or as a hybrid system. The influences were investigated of the applied frequencies, of fibre combinations and of the age of the composites on the impedance. The results show that when the applied frequency is increased from 0.98 Hz to 1000 Hz, the impedance of the fibre composites significantly decreases. At the same time, impedance difference between plain concrete and fibre-reinforced concrete is enhanced. Dramatic drop of impedance takes place over the low frequency range, i.e. 0.98 to approximately 31 Hz. Impedance also depends on the volume content of hybrid fibres. The cementitious composite with the highest content of hybrid fibres (1.0% steel fibres and 0.2% carbon fibres by volume) has the lowest impedance at all measuring frequencies. 0.6% fibres by volume seem to be a turning point, from which the variation of impedance slows down with the fibre content increases. On the other hand, the impedance increment of the fibre-reinforced composites slows down with the age after 28 days, comparing to plain concrete. (Author abstract) 8 Refs.
基金Funded by the Key R&D Projects of Shanxi Province(No.201903D321113)the Shanxi Provincial Natural Science Foundation(No.202303021212359)the General Research Projects of Taiyuan University(No.23TYYB07)。
文摘Carbon fibre,steel fibre and graphite were used as conductive fillers to prepare cementitious materials with excellent electrothermal properties.The electrically conductive cementitious materials with different volume dosages were analysed through compressive and flexural strength,electrochemical impedance spectroscopy and temperature rise tests.An equivalent circuit model was established to study the electrically conductive heat generation mechanism in the electrically conductive cementitious composites.The results indicate that the mechanical properties of cementitious composite materials with a ternary conductive phase are better than those of pristine cementitious materials because the fibrous filler improves their mechanical properties.However,the incorporation of graphite in the material reduces its strength.Introducing fibrous and point-like conductive phase materials into the cementitious material enhances the overall conductive pathway and considerably reduces the electrical resistance of the cementitious material,enhancing its conductive properties.The volume ratios of carbon fibre,steel fibre and graphite that achieve an optimal complex doping in the cementitious material were 0.35%,0.6%and 6%,respectively.This was determined using the mutation point of each circuit element parameter as the percolation threshold.In addition,at a certain safety voltage,there is a uniform change between the internal and surface temperatures of the conductive cementitious material,and the heating effect in this materialis is considerably better than that in the pristine cementitious material.
基金supported by China Academy of Railway Sciences grant number[No.2023YJ078].
文摘In order to improve the damage resistance of concrete,a cement-based self-healing additive(abbreviate as CS)was prepared.To investigate the influence of CS on the self-healing performance of cementitious material,X-ray diffraction(XRD)and thermal analysis were used to investigate the effects of different dosages of CS on the hydration process and hydration products of cementitious material.Compressive strength test and load damage self-healing test were used to show the influence of different amounts of CS on the mechanical properties of concrete.The pore structure distribution of cement paste with different dosages of CS was analyzed using mercury intrusion testing method.The results indicated that different dosages of CS had no effect on the types of hydration products of cementitious material.Adding an appropriate amount of CS can effectively improve the micro pore structure of cement-based materials,reduce the proportion of harmful pores in the structure,and decrease the most probable pore diameter.When microcracks are generated in the structure under load,CS can promote the formation of hydration products inside the structure to fill the microcracks,thereby improving the self-healing performance of cement-based materials.This study provides an idea for improving microcracks and enhancing durability of marine concrete structures.
文摘This study applied machine learning methods to predict the durability performance(specifically shrinkage and freeze-thaw resistance)of solid waste-activated cementitious materials.It also offered insights for optimizing material formulations through feature impact analysis.The study collected a total of 130 sets of shrinkage data and 106 sets of freeze-thaw data,establishing various models,including BP,GA-BP,SVM,RF,RBF,and LSTM.The results revealed that the SVM model performed the best on the test dataset.It achieved an R^(2) of 0.9358 for shrinkage prediction,with MAE and RMSE values of 0.4644 and 0.6254,respectively.Regarding freeze-thaw quality loss prediction,the R^(2) was 0.9178,with MAE and RMSE values of 0.3139 and 0.5328,respectively.The study analyzed the impact of different features on the outcomes using the SHAP method,highlighting that the alkaline activator dosage,Al_(2)O_(3),SiO_(2),and water glass modulus were critical factors influencing shrinkage,while CaO,water-cement ratio,water,and Al_(2)O_(3) were crucial for freeze-thaw resistance.By investigating feature interactions through single-factor and two-factor analysis,the study proposed recommendations for optimizing material formulations.This research validated the efficacy of machine learning in predicting the durability of solid waste cementitious materials and offered insights for material optimization through feature impact analysis,thereby laying the groundwork for the development of related materials.
基金Projects(52222404,52074212)supported by the National Natural Science Foundation of ChinaProject(2023-LL-QY-07)supported by the Two-chain Integration Key Projects in Shaanxi Province,China。
文摘As the second most important solid waste produced by coal-fired power plants,the improper management of coal-fired slag has the potential to result in environmental pollution.It is therefore imperative that high-value utilization pathways for coal-fired slag should be developed.In this study,modified magnesium slag(MMS),produced by a magnesium smelter,was selected as the alkali activator.The activated silica-aluminum solid wastes,namely coal-fired slag(CFS)and mineral powder(MP),were employed as pozzolanic materials in the preparation of alkali-activated cementitious materials.The alkali-activated cementitious materials prepared with 50 wt%MMS,40 wt%CFS and 10 wt%MP exhibited favorable mechanical properties,with a compressive strength of 32.804 MPa in the paste sample cured for 28 d.Then,the activated silica-aluminum solid waste consisting of CFS-MP generated a significant amount of C-S(A)-H gels,AFt,and other products,which were observed to occupy the pore structure of the specimen.In addition,the secondary hydration reaction of CFS-MP occurs in high alkalinity environments,resulting in the formation of a mutually stimulated and promoted reaction system between CFS-MP and MMS,this will subsequently accelerate the hydrolysis reaction of MMS.It is important to emphasize that the amount of MMS in alkali-activated cementitious materials must be strictly regulated to avert the potential issue of incomplete depolymerization-repolymerization of active silica-aluminum solid waste containing CFS-MP.This in turn could have a deleterious impact on the late strength of the cementitious materials.The aim of this work is to improve the joint disposal of MMS,CFS and MP and thereby provide a scientific basis for the development of environmentally friendly and low-carbon modified magnesium slag alkali-activated coal-fired slag based cementitious materials for mine backfilling.
基金Funded by the Science and Technology Program of Gansu Province(No.25CXGA070)。
文摘To investigate the feasibility of applying electrolytic manganese residue(EMR)in cementitious materials,an approach combining high-temperature activation(200,400,600,800 and 1000℃)and mechanical grinding(5 min)was adopted to stimulate the EMR activity.We analyzed the effect of calcination temperature on the performance of EMR with the aid of X-ray diffraction(XRD),specific surface area test(BET)and pozzolanic activity test,explored the effects of EMR activation temperature and content(0%,10%,15% and 20%)on the setting time,soundness,drying shrinkage,compressive strength,hydration products of cement-EMR mixed slurry,and assessed the effect of cement hydration on the solidification of harmful NH_(4)^(+)-N and Mn^(2+) in EMR.The research results show that high-temperature calcination can lead to the dehydration,decomposition or crystalline phase transformation of the inert sulfate and other substances in EMR,mechanical grinding can improve its particle distribution,and the coupling of the two can effectively enhance the pozzolanic activity of EMR.The decomposition and recombination of aluminum-silica phase at 800℃ optimized the EMR activity,and the strength activity index(SAI)of EMR at 28 d reached up to 95%.Appropriate calcination temperature and EMR content can ensure the workability of the mixed slurry,and when the EMR calcination temperature was 400-1000℃,the setting time of the mixed slurry under different EMR contents satisfied the specification requirements.When the calcination temperature was 600-1000℃ and EMR content was less than 20%,the soundness of the mixed slurry satisfied the specification requirements.The compressive strength of the mixed slurry increased and then decreased with the increase of activated EMR content,when the EMR content was 10%,the compressive strength of all specimens was optimal and higher than the baseline group;when the activation temperature was 800℃,the C-S-H gel in the mixed slurry interconnected with the rod-like Aft and blocked Ca(OH)_(2),and the 28 d compressive strength was increased by 14%compared with that of the baseline group.The solidification rate of Mn^(2+) in EMR by cement hydration was higher than 99%,and that of NH_(4)^(+)-N was higher than 97%.The leaching toxicity after solidification can meet the requirements of toxic emission.The results of the study may provide theoretical basis for the feasibility of the application of EMR in cementitious materials.
基金Project(LM(2022)-F-053)supported by the China Railway Resources Science and Technology。
文摘Molybdenum tailings are the solid waste left from ore processing,which damages soil and water resources.To address that,molybdenum tailings(MTs)powder obtained from molybdenum tailings sands was processed as an admixture.Compared with moisture-cured conditions,the influence of MTs on the steam-cured mortar’s mechanical properties,surface and internal pore characteristics,and microscopic morphology was investigated.The results show that steam-cured mortar containing appropriate MTs can still have high early strength.When the content of MTs doesn’t exceed 15%,the mechanical strength of mortar steam-cured for 3 d can reach 85%of that of corresponding mortar moisture-cured for 28 d,and that of mortar steam-cured for 28 d isn’t lower than 90%of that of pure cement mortar.The proportion of harmful pores(HFP)and more harmful pores(MHFP)and most probable pore diameters(MPD)on the mortar surface containing MTs steam-cured for 28 d are significantly decreased.When MTs’content is 15%,the proportion of HFP and MHFP on the surface of paste is decreased by 71.4%and 72.2%,respectively,with MPS decreasing from 12.7 nm to 10.8 nm.SEM analysis shows that the surfaces of steam-cured paste containing 15%MTs have more hydration products and dense microstructures.The effect of pozzolanic and dense filling of MTs effectively refines the pore structure,reducing the large pore-size pores.
文摘The rapid change in CO_(2) concentration levels,due to climate change,will lead to a significant reduction in the durability and safety of the vital reinforced concrete(RC)structures.Utilizing supplementary cementitious materials,such as low calcium fly ash(LCFA)or slag,etc.,with larger percentages in concrete mixes,would lead to an increase in the carbonation depth and risk of corrosion,especially for cracked concrete sections subjected to severe CO_(2) concentration levels.This research aims to compare the carbonation depth values using two different mathematical models across various CO_(2) concentrations and crack widths,for concrete mixes composed of different percentages and types of fly ash for both uncracked and cracked RC members,at a specific time of CO_(2) exposure.Moreover,the main objective is to assess the probability of corrosion(PC)across various percentages and types of fly ash used in cracked RC decks subjected to a severe CO_(2) level.The PC would be investigated through the Montecarlo simulation method.A Crack width of 0.1 mm in the RC decks would lead to a severe impact on the PC conducted using the Al-Ameeri model compared to the Kwon and Na model,when the percentages of LCFA vary from 5%to 30%in concrete mixes.It is recommended in this research to reduce the amount of high calcium fly ash in the mixes for RC decks to a percentage below 15%instead of LCFA to inhibit the carbonation-induced corrosion and enhance the durability and serviceability of RC structures.
基金financially supported by the Natural Sci-ence Foundation of Hunan Province,China(No.2024JJ2074)National Natural Science Foundation of China(No.22376221)+2 种基金Young Elite Scientists Sponsorship Pro-gram by the China Association for Science and Technology(CAST)(No.2023QNRC001)partly supported by the High Performance Computing Center of Central South University,Chinasupported by resources provided by the Pawsey Supercomputing Centre with funding from the Australian Government and the Government of Western Australia.
文摘Understanding the differences in CO_(2)adsorption in cementitious material is critical in mitigating the carbon footprint of the construction industry.This study chose the most common β-C_(2)S phase in the industry as the cementitious material,selecting the β-C_(2)S(111)and β-C_(2)S(100)surfaces for CO_(2)adsorption.First-principles calculations were employed to systematically compare the CO_(2)ad-sorption behaviors on both surfaces focusing on adsorption energy,adsorption configurations,and surface reconstruction.The comparis-on of CO_(2)and H2O adsorption behaviors on the β-C_(2)S(111)surface was also conducted to shed light on the influence of CO_(2)on cement hydration.The adsorption energies of CO_(2)on the β-C_(2)S(111)and β-C_(2)S(100)surfaces were determined as-0.647 and-0.423 eV,respect-ively,suggesting that CO_(2)adsorption is more energetically favorable on the β-C_(2)S(111)surface than on the β-C_(2)S(100)surface.The ad-sorption energy of H2O on the β-C_(2)S(111)surface was-1.588 eV,which is 0.941 eV more negative than that of CO_(2),implying that β-C_(2)S tends to become hydrated before reacting with CO_(2).Bader charges,charge density differences,and the partial density of states were ap-plied to characterize the electronic properties of CO_(2)and H2O molecules and those of the surface atoms.The initial Ca/O sites on the β-C_(2)S(111)surface exhibited higher chemical reactivity due to the greater change in the average number of valence electrons in the CO_(2)ad-sorption.Specifically,after CO_(2)adsorption,the average number of valence electrons for both the Ca and O atoms increased by 0.002 on the β-C_(2)S(111)surface,while both decreased by 0.001 on the β-C_(2)S(100)surface.In addition,due to the lower valence electron number of O atoms,the chemical reactivity of O atoms on the β-C_(2)S(111)surface after H2O adsorption was higher than the case of CO_(2)adsorption,which favors the occurrence of further reactions.Overall,this work assessed the adsorption capacity of the β-C_(2)S surface for CO_(2)mo-lecules,offering a strong theoretical foundation for the design of novel cementitious materials for CO_(2)capture and storage.
基金Funded by the Natural Science Foundation of Jiangsu Province(No.BK20220626)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX24_3174)Taizhou Science and Technology Support Programme(Social Development)Directive Project(No.TS202432)。
文摘The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully replace natural fine aggregates was investigated.The results indicated that a 50% FA content significantly increased the compressive strength of RFA-HDCC by 13.93%.However,a?further increase in FA content led to a drastic decrease.The increased fly ash content substantially reduced the flexural and tensile strength;however,it markedly increased the matrix strain capacity,resulting in a 53.73% increase in the peak strain when FA was raised to 70%.Regarding durability,the increase in FA content negatively affected the chloride ion permeability and carbonation resistance.However,the increase in FA content initially improved the frost resistance of RFA-HDCC,peaking at 50% FA and deteriorating at 60% and 70% FA content.
基金Funded by the Science and Technology Program of Gansu Province(Nos.23JRRA799 and 24JRRA213)the National Natural Science Foundation of China(Nos.52178216,52008196,and U21A20150)。
文摘In order to avoid the waste of iron caused by the direct use of ferronickel slag(FNS)in building materials,the effects of reduction iron extraction on the physical and chemical properties,cementitious reactivity and hydration reaction characteristics of FNS and ferrum extraction tailing of nickel slag(FETNS)were studied.The experimental results show that the reduction ferrum extraction method changes the mineral phase composition of the waste slag,breaks the Si-O-Si bond,forms the tetrahedral structure of Si-O-NBO or Si-O-2NBO,and increases the content of active components such as Ca,Si,Mg,and Al.Compared with FNS,the 28 d compressive strength of pastes prepared by FETNS increases by 16.12%,22.57%,33.13%,44.26%,and 57.65%,respectively.The degree of hydration reaction of the composite cementitious systems in the FETNS group is higher than that in the FNS group at different ages,and the content of hydration products such as C-S-H gel and ettringite(AFt)is also higher than that in the FNS group.More hydration products can improve the curing ability to Cr and Mn of the composite cementitious systems in the FETNS group,and reduce the leaching value of Cr and Mn.
基金Funded by the Scientific Research Program of Jilin Provincial Science and Technology Development(No.20250203184SF)。
文摘A solid,fast-dissolving sodium silicate was used as an alkaline activator.Granulated blast furnace slag(GGBS),metakaolin(MK),and steel slag(SS)were used as the cementious components to prepare a ternary composite cementitious material known as alkali-activated steel slag composite cementitious material(ASCM)by the"one-step method".The impacts of cementitious components,alkali activator modulus,and Na_(2)O%on the mechanical strength were investigated,and the hydration products and hydration kinetics of ASCM were analyzed.The experimental results reveal that XRD,FTIR,SEM,EDS,and exothermic heat of hydration show that when GGBS:MK:SS=60wt%:10wt%:30wt%,the activator modulus is 1.2,and the alkali content is 5.5wt%,the 28 d flexural strength of ASCM mortar is 12.6 MPa,and the compressive strength is 53.3 MPa,the hydration products consist of C-S-H gel/C-A-S-H gel,mullite(3Al_(2)O_(3)-2SiO_(2)),calcite(CaCO_(3)),quartz,etc.ASCM has a large initial hydration exotherm rate but a small cumulative exotherm.
基金supported by the National Natural Science Foundation of China (51478370)the Engineering and Physical Sciences Research Council of UK–Natural Science Foundation of China (EPSRC-NSFC) International Joint Research Project (51461135005)~~
文摘A TiO2 photocatalyst is coated on the surface of a zeolite fly ash bead（ZFAB） to improve its dispersability and exposure degree in a cement system.The application of Ag particles in TiO2/ZFAB modified cementitious materials is to further enhance the photocatalytic performance.Various Ag@TiO2/ZFAB modified cementitious specimens with different Ag dosages are prepared and the characteristics and photocatalytic performance of the prepared samples are investigated.It is observed that the multi-level pore structure of ZFAB can improve the exposure degree of TiO2 in a cement system and is also useful to enhance the photocatalytic efficiency.With an increment of the amounts of Ag particles in the TiO2/ZFAB modified cementitious samples,the photocatalytic activities increased first and then decreased.The optimal Ag@TiO2/ZFAB modified cementitious sample reveals the maximum reaction rate constant for degrading benzene（9.91×10^-3 min^-1）,which is approximately 3 and 10 times higher than those of TiO2/ZFAB and TiO2 modified samples,respectively.This suggests that suitable Ag particles coupled with a ZFAB carrier could effectively enhance the photocatalytic effects and use of TiO2 in a cement system.Thus,ZFAB as a carrier could provide a potential method for a high efficiency engineering application of TiO2 in the construction field.
基金The National Natural Science Foundation of China(No.51278118)the National Basic Research Program of China(973Program)(No.2009CB623200)the Natural Science Foundation of Jiangsu Province(No.BK2012756)
文摘To investigate the flexural behaviors of steel reinforced engineered cementitious composite （ECC） beams, the behaviors of the steel reinforced ECC beam and the conventional steel reinforced concrete beam subjected to flexural load are experimentally compared. The experimental results show that the flexural strength and ductility of the steel reinforced ECC beam are 24.8% and 187.67% times larger than those of the steel reinforced concrete beam, and the substitution of concrete with ECC can significantly delay the propagation of cracks. Additionally, a simplified constitutive model of the ECC material is used to simulate the flexural behaviors of beams by the finite element analysis （FEA）. The results show a good agreement between the simulation and test results. The crack width of the steel reinforced ECC beam can be limited to 0.4 mm under the service load conditions. The application of ductile ECC can significantly increase the flexural performance in terms of flexural strength, deformation capacity and ductility of the beams.
