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
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
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
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
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
In the background of little reuse and large stockpile for iron ore tailings, iron ore tailing from Chinese Tonghua were used as raw material to prepare cementitious materials. Cementitious properties of the iron ore t...In the background of little reuse and large stockpile for iron ore tailings, iron ore tailing from Chinese Tonghua were used as raw material to prepare cementitious materials. Cementitious properties of the iron ore tailings activated by compound thermal activation were studied. Testing methods, such as XRD, TG-DTA, and IR were used for researching the phase and structure variety of the iron ore railings in the process of compound thermal activation. The results reveal that a new cementitious material that contains 30wt% of the iron ore tailings can be obtained by compounded thermal activation, whose mortar strength can come up to the standard of 42.5 cement of China.展开更多
High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials. The gangue was calcined at 500℃. The main constituent was calcined gangue, fly ash ...High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials. The gangue was calcined at 500℃. The main constituent was calcined gangue, fly ash and slag, while alkali-silicate solutions were used as the diagenetic agent. The structure of gangue-containing aluminosilicate based cementitious materials was studied by the methods of IR, NMR and SEM. The results show that the mechanical properties are affected by the mass ratio between the gangue, slag and fly ash, the kind of activator and additional salt. For 28-day curing time, the compressive strength of the sample with a mass proportion of 2：1：1 （gangue： slag： fly ash） is 58.9 MPa, while the compressive strength of the sample containing 80wt% gangue can still be up to 52.3 MPa. The larger K^＋ favors the formation of large silicate oligomers with which AI（OH）4- prefers to bind. Therefore, in Na-K compounding activator solutions more oligomers exist which result in a stronger compressive strength of aluminosilicate-based cementitious materials than in the case of Na-containing activator. The reasons for this were found through IR and NMR analysis. Glauber＇s salt reduces the 3-day compressive strength of the paste, but increases its 7-day and 28-day compressive strengths.展开更多
Red mud-fly ash based cementitious material mixed with different contents of oil shale calcined at 700 ℃ is investigated in this paper. The effect of active Si and A1 content on the solidification of Na＋ during the ...Red mud-fly ash based cementitious material mixed with different contents of oil shale calcined at 700 ℃ is investigated in this paper. The effect of active Si and A1 content on the solidification of Na＋ during the hydration process is determined by using X-ray diffraction （XRD）, 27A1 and 29Si magic-angle-spinning nuclear magnetic resonance （MAS-NMR）, infrared （IR）, scanning electronic microscopy （SEM） and X-ray photoelectron spectroscopy （XPS）. It is shown that the content of oil shale has a remarkable effect on the solidified content of Na＋. The hydration process generates a highly reactive intermediate gel phase formed by co-polymerisation of individual alumina and silicate species. This kind of gel is primarily considered as 3D framework of Si04 and A104 tetrahedra interlinked by the shared oxygen atoms randomly. The negative charges and four-coordinated A1 inside the network are mainly charge-balanced by Na＋. The solidifying mechanism of Na＋ is greatly attributed to the forming of this kind of gel.展开更多
To elucidate the intrinsic reaction mechanism of cementitious materials composed of red mud and coal gangue（RGC）, the hydration kinetics of these cementitious materials at 20°C was investigated on the basis of ...To elucidate the intrinsic reaction mechanism of cementitious materials composed of red mud and coal gangue（RGC）, the hydration kinetics of these cementitious materials at 20°C was investigated on the basis of the Krstulovi？-Dabi？ model. An isothermal calorimeter was used to characterize the hydration heat evolution. The results show that the hydration of RGC is controlled by the processes of nucleation and crystal growth（NG）, interaction at phase boundaries（I）, and diffusion（D） in order, and the pozzolanic reactions of slag and compound-activated red mud-coal gangue are mainly controlled by the I process. Slag accelerates the clinker hydration during NG process, whereas the compound-activated red mud-coal gangue retards the hydration of RGC and the time required for I process increases with increasing dosage of red mud-coal gangue in RGC.展开更多
Water-quenched copper-nickel metallurgical slag enriched with olivine minerals exhibits promising potential for the production of CO_(2)-mineralized cementitious materials.In this work,copper-nickel slag-based cementi...Water-quenched copper-nickel metallurgical slag enriched with olivine minerals exhibits promising potential for the production of CO_(2)-mineralized cementitious materials.In this work,copper-nickel slag-based cementitious material(CNCM)was synthesized by using different chemical activation methods to enhance its hydration reactivity and CO_(2) mineralization capacity.Different water curing ages and carbonation conditions were explored related to their carbonation and mechanical properties development.Meanwhile,thermogravimetry differential scanning calorimetry and X-ray diffraction methods were applied to evaluate the CO_(2) adsorption amount and carbonation products of CNCM.Microstructure development of carbonated CNCM blocks was examined by backscattered electron imaging(BSE)with energy-dispersive X-ray spectrometry.Results showed that among the studied samples,the CNCM sample that was subjected to water curing for 3 d exhibited the highest CO_(2) sequestration amount of 8.51wt%at 80℃and 72 h while presenting the compressive strength of 39.07 MPa.This result indicated that 1 t of this CNCM can sequester 85.1 kg of CO_(2) and exhibit high compressive strength.Although the addition of citric acid did not improve strength development,it was beneficial to increase the CO_(2) diffusion and adsorption amount under the same carbonation conditions from BSE results.This work provides guidance for synthesizing CO_(2)-mineralized cementitious materials using large amounts of metallurgical slags containing olivine minerals.展开更多
By means of low-field nuclear magnetic resonance(LF-NMR),the transverse relaxation time(T_(2))signals of physically bound water in cement paste were monitored to indicate water content change and characterize the earl...By means of low-field nuclear magnetic resonance(LF-NMR),the transverse relaxation time(T_(2))signals of physically bound water in cement paste were monitored to indicate water content change and characterize the early-age hydration process.With the curves of the T_(2)signals and hydration time obtained,the hydration process could be divided into four typical periods using the null points of the second derivative curve,and the influences of water-cement ratio(w/c)and hydration heat regulating materials(HHRM)on hydration process were analyzed.The experimental results showed that the hydration rate of pure cement paste in accelerated period presented a positive correlation with w/c.Compared to pure cement paste,the addition of HHRM extended all four periods,and led to a much faster hydration rate in initial period as well as a slower rate in accelerated period.Finally,according to the LFNMR test results,the early-age hydration model of cementitious materials was proposed considering w/c and HHRM content.展开更多
To explore the distribution of and the mechanical properties(compressive strength)of the hardened body of alkali slag-fly ash cementitious materials,this study was conducted by using the XRD,FTIR,SEM/EDS,and other tes...To explore the distribution of and the mechanical properties(compressive strength)of the hardened body of alkali slag-fly ash cementitious materials,this study was conducted by using the XRD,FTIR,SEM/EDS,and other test methods in three conditions:airtight drying(AD),airtight immersion(AI),and airtight soaking(AS).The 1D distribution law of free of hardened body under standard curing conditions was explored.The experimental results show that under standard curing conditions,the 1D distribution of within 0d-3 d shows a∨-shaped distribution,within 3-7 d show a∧-shaped distribution,and within 7-28 d tends to be balanced.The test results of leaching rate show that the free was the most stable under AD conditions and the hardened body bound the most by XRD,FTIR and SEM/EDS.And the compressive strength of the hardened body was the highest.The compressive strength of 28th reached 95.9 MPa.The definite distribution of provides an important reference for the strength development and durability evaluation of the hardened body of alkaliexcited cementitious materials.展开更多
In this study,micronized sand is selected as a kind of filler to partially replace cement in cementitious materials. This filler is considered as chemically inert material,which can not react with water or hydration p...In this study,micronized sand is selected as a kind of filler to partially replace cement in cementitious materials. This filler is considered as chemically inert material,which can not react with water or hydration products,but still indirectly influences the hydration in a positive way. In the experimental program,non-evaporable water test was carried out to determine the degree of hydration of cement paste with and without micronized sands. The influence of different finenesses of sand particles,240 m2/kg,400 m2/kg and 1 300 m2/kg,and different curing ages were investigated. The SEM image analysis was used to characterize the morphological changes of microstructure by the presence of the micronized sand during the cement hydration process. Hydration reaction is enhanced by the use of inert micronized sands. The fineness of micronized sands influences the degree of hydration a lot. The fineness factor has been taken into account in the simulation. There is a clear interface area between sand particle and hydration products.展开更多
This paper studied the effects of different retarders on the performance of the"one-step"alkali-activated composite cementitious material(ACCM)which is composed of ground granulated blast slag(GGBS)and fly a...This paper studied the effects of different retarders on the performance of the"one-step"alkali-activated composite cementitious material(ACCM)which is composed of ground granulated blast slag(GGBS)and fly ash(FA),and analyzed its mechanical properties,hydration mechanism,and retardation mechanism.The effects of retarders on the hydration products,mechanical properties,and hydration kinetics of ACCM were investigated using XRD,SEM,FTIR,EDS,and thermoactive microcalorimetry.The results showed that Na_(2)B_(4)O_(7)·10H_(2)O(B)delayed the exotherm during the alkali activation process and could effectively delay the setting time of ACCM,but the mechanical properties were slightly decreased.The setting time of ACCM increased with the increase in SG content,but the mechanical properties of ACCM decreased with the increase in SG content.C1_(2)H_(22)O_(11)(CHO)could effectively delay the hydration reaction of ACCM and weakly enhanced the compressive strength.H_(3)PO_(4)(HP)at a concentration of 0.05 mol/L had a certain effect on ACCM retardation,but HP at a concentration of 0.07 and 0.09 mol/L had an effect of promoting the setting and hardening time of ACCM.展开更多
To obtain the compositions and microstructure of hydration products of cementitious material in different hydration ages and its growth law of filling strength, the optimal proportion of composite cementitious materia...To obtain the compositions and microstructure of hydration products of cementitious material in different hydration ages and its growth law of filling strength, the optimal proportion of composite cementitious material was determined according to the chemical composition of cement clinker which was composed of the Portland cement 32.5R, CSA 42.5 sulphoaluminate cement and two gypsum（CS）. The characterization of composite cementitious materials in different hydration ages was conducted by NMR, XRD and SEM techniques. The mechanism of hydration was explored. It is shown that the compressive strength of the test block increases gradually with the increase of hydration age. The microstructure of composite cementitious material can be changed from Al-O octahedron into Al-O tetrahedron in the hydration process. The hydrated alkali alumi niumsilicate formed with Si-O tetrahedron and Al-O tetrahedron. The degree of polymerization of Si-O tetrahedron gradually increased, and the structural strength of cementitious materials continued to increase. The diffraction peak of clinker minerals gradually decreased with the extension of hydration age. The CaSO4 completely hydrated to produce Aft during hydration which resulted in high early strength of cementitious material. The early hydration product of composite cementitious materials was Aft with a needle bar structure. The main middle and last hydration products were CSH gel and CH gel with dense prismatic shape. The microscopic pore of composite cementitious material gradually decreased and improved the later strength of filling block. The strong support was provided for mined-out area.展开更多
This paper aimed to improve the water-retention performance and basic physical properties of sulfoaluminate cement（SAC）-based planting cementitious material. The effect of natural zeolite on the performance of SAC-b...This paper aimed to improve the water-retention performance and basic physical properties of sulfoaluminate cement（SAC）-based planting cementitious material. The effect of natural zeolite on the performance of SAC-based planting material was investigated. The water-retention performance, porosity, compressive strength, and alkalinity had been tested and TG-DSC analysis had been adopted in this paper. Experimental results showed that zeolite was effective to improve the water-retention capacity and 10%, 20% and 30% natural zeolite increased the pore volume of the hardened pastes by 10.6%, 26.0%, and 38.6%, especially pore size below 0.1 μm was increased by 9.7%, 26.2% and 17.5%. And 10% zeolite was beneficial to the compressive strengths of cementitious material and 1, 3, and 28 d compressive strength reached up to 35.9, 55.0, 80.3 MPa. Furthermore zeolite decreased the alkalinity of pore fluid of hardened cementitious material, while the addition of zeolite reached up to 30%, the alkalinity of pore fluid of hardened cementitious material decreased by 8.9%. Therefore zeolite was suitable for improving the performance of SAC-based planting cementitious material.展开更多
Experimental investigation was conducted on the effects of gypsum types and SO 3 content on the fluidity and strengths of different cementitious systems.The experimental results show that influences of gypsum in vari...Experimental investigation was conducted on the effects of gypsum types and SO 3 content on the fluidity and strengths of different cementitious systems.The experimental results show that influences of gypsum in various cementitious materials are different.For cementitious materials blended with various proportions of slag fly ash and 5% gypsum content,influences of gypsum and calcined gypsum on the fluidity and flexural/compressive strength are similar.It is revealed that 'combination effect' and 'synergistic effect' of slag and fly ash play an important role during hydration.For cementitious materials with 45% clinkers,30%slag,20%fly ash and 5%limestone,the optimized SO 3 contents in gypsum and calcined gypsum are 3.13% and 3.51% respectively and the optimized gypsum content is 6.5%.While both of them are blended,the optimum ratio of gypsum to calcined gypsum is 40%∶60%(total gypsum content 6.5%),correspondingly the optimum ratio of SO 3 is 19.3%∶32.4%.展开更多
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.
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 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supported by the National Nature Science Foundation of China (No.50674062)the National Key Technologies R&D Program of China (No.2006BAC21B03)the Post doctoral Science Foundation (No.20070420354)
文摘In the background of little reuse and large stockpile for iron ore tailings, iron ore tailing from Chinese Tonghua were used as raw material to prepare cementitious materials. Cementitious properties of the iron ore tailings activated by compound thermal activation were studied. Testing methods, such as XRD, TG-DTA, and IR were used for researching the phase and structure variety of the iron ore railings in the process of compound thermal activation. The results reveal that a new cementitious material that contains 30wt% of the iron ore tailings can be obtained by compounded thermal activation, whose mortar strength can come up to the standard of 42.5 cement of China.
基金This work was supported by the National High-Tech Research and Development Program of China (No.2003AA332020), the Nation-al Natural Science Foundation of China (No.50474002) and the Key Project of the Ministry of Education of China (No.104231).
文摘High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials. The gangue was calcined at 500℃. The main constituent was calcined gangue, fly ash and slag, while alkali-silicate solutions were used as the diagenetic agent. The structure of gangue-containing aluminosilicate based cementitious materials was studied by the methods of IR, NMR and SEM. The results show that the mechanical properties are affected by the mass ratio between the gangue, slag and fly ash, the kind of activator and additional salt. For 28-day curing time, the compressive strength of the sample with a mass proportion of 2：1：1 （gangue： slag： fly ash） is 58.9 MPa, while the compressive strength of the sample containing 80wt% gangue can still be up to 52.3 MPa. The larger K^＋ favors the formation of large silicate oligomers with which AI（OH）4- prefers to bind. Therefore, in Na-K compounding activator solutions more oligomers exist which result in a stronger compressive strength of aluminosilicate-based cementitious materials than in the case of Na-containing activator. The reasons for this were found through IR and NMR analysis. Glauber＇s salt reduces the 3-day compressive strength of the paste, but increases its 7-day and 28-day compressive strengths.
基金the National Natural Science Foundation of China(Nos.51034008 and 51104008)the China Postdoctoral Science Foundation Funded Project(No.20100480202)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China(No.20100006120010)the Fundamental Research Funds for the Central Universities of China (No.FRF-TP-12-026A)
文摘Red mud-fly ash based cementitious material mixed with different contents of oil shale calcined at 700 ℃ is investigated in this paper. The effect of active Si and A1 content on the solidification of Na＋ during the hydration process is determined by using X-ray diffraction （XRD）, 27A1 and 29Si magic-angle-spinning nuclear magnetic resonance （MAS-NMR）, infrared （IR）, scanning electronic microscopy （SEM） and X-ray photoelectron spectroscopy （XPS）. It is shown that the content of oil shale has a remarkable effect on the solidified content of Na＋. The hydration process generates a highly reactive intermediate gel phase formed by co-polymerisation of individual alumina and silicate species. This kind of gel is primarily considered as 3D framework of Si04 and A104 tetrahedra interlinked by the shared oxygen atoms randomly. The negative charges and four-coordinated A1 inside the network are mainly charge-balanced by Na＋. The solidifying mechanism of Na＋ is greatly attributed to the forming of this kind of gel.
基金financially supported by the National Natural Science Foundation of China(Nos.51302012 and 51234008)the China Postdoctoral Science Foundation(No.2016M590046)
文摘To elucidate the intrinsic reaction mechanism of cementitious materials composed of red mud and coal gangue（RGC）, the hydration kinetics of these cementitious materials at 20°C was investigated on the basis of the Krstulovi？-Dabi？ model. An isothermal calorimeter was used to characterize the hydration heat evolution. The results show that the hydration of RGC is controlled by the processes of nucleation and crystal growth（NG）, interaction at phase boundaries（I）, and diffusion（D） in order, and the pozzolanic reactions of slag and compound-activated red mud-coal gangue are mainly controlled by the I process. Slag accelerates the clinker hydration during NG process, whereas the compound-activated red mud-coal gangue retards the hydration of RGC and the time required for I process increases with increasing dosage of red mud-coal gangue in RGC.
基金supported by the Intergovernmental International Science and Technology Innovation Cooperation Key Project of the National Key Research and Development Program of China (No.2022YFE0135100)the National Natural Science Foundation of China (No.52072171)+1 种基金the Beijing Nova Program (No.20220484057)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).
文摘Water-quenched copper-nickel metallurgical slag enriched with olivine minerals exhibits promising potential for the production of CO_(2)-mineralized cementitious materials.In this work,copper-nickel slag-based cementitious material(CNCM)was synthesized by using different chemical activation methods to enhance its hydration reactivity and CO_(2) mineralization capacity.Different water curing ages and carbonation conditions were explored related to their carbonation and mechanical properties development.Meanwhile,thermogravimetry differential scanning calorimetry and X-ray diffraction methods were applied to evaluate the CO_(2) adsorption amount and carbonation products of CNCM.Microstructure development of carbonated CNCM blocks was examined by backscattered electron imaging(BSE)with energy-dispersive X-ray spectrometry.Results showed that among the studied samples,the CNCM sample that was subjected to water curing for 3 d exhibited the highest CO_(2) sequestration amount of 8.51wt%at 80℃and 72 h while presenting the compressive strength of 39.07 MPa.This result indicated that 1 t of this CNCM can sequester 85.1 kg of CO_(2) and exhibit high compressive strength.Although the addition of citric acid did not improve strength development,it was beneficial to increase the CO_(2) diffusion and adsorption amount under the same carbonation conditions from BSE results.This work provides guidance for synthesizing CO_(2)-mineralized cementitious materials using large amounts of metallurgical slags containing olivine minerals.
基金Funded by National Natural Science Foundation of China(Nos.U1965105,51878245)National Key R&D Program of China(No.2021YFF0500802)。
文摘By means of low-field nuclear magnetic resonance(LF-NMR),the transverse relaxation time(T_(2))signals of physically bound water in cement paste were monitored to indicate water content change and characterize the early-age hydration process.With the curves of the T_(2)signals and hydration time obtained,the hydration process could be divided into four typical periods using the null points of the second derivative curve,and the influences of water-cement ratio(w/c)and hydration heat regulating materials(HHRM)on hydration process were analyzed.The experimental results showed that the hydration rate of pure cement paste in accelerated period presented a positive correlation with w/c.Compared to pure cement paste,the addition of HHRM extended all four periods,and led to a much faster hydration rate in initial period as well as a slower rate in accelerated period.Finally,according to the LFNMR test results,the early-age hydration model of cementitious materials was proposed considering w/c and HHRM content.
基金Funded by the Natural Sciences Foundation of China(No.51808025)the Pyramid Talent Training Project of BUCEA(No.JDYC20200329)。
文摘To explore the distribution of and the mechanical properties(compressive strength)of the hardened body of alkali slag-fly ash cementitious materials,this study was conducted by using the XRD,FTIR,SEM/EDS,and other test methods in three conditions:airtight drying(AD),airtight immersion(AI),and airtight soaking(AS).The 1D distribution law of free of hardened body under standard curing conditions was explored.The experimental results show that under standard curing conditions,the 1D distribution of within 0d-3 d shows a∨-shaped distribution,within 3-7 d show a∧-shaped distribution,and within 7-28 d tends to be balanced.The test results of leaching rate show that the free was the most stable under AD conditions and the hardened body bound the most by XRD,FTIR and SEM/EDS.And the compressive strength of the hardened body was the highest.The compressive strength of 28th reached 95.9 MPa.The definite distribution of provides an important reference for the strength development and durability evaluation of the hardened body of alkaliexcited cementitious materials.
文摘In this study,micronized sand is selected as a kind of filler to partially replace cement in cementitious materials. This filler is considered as chemically inert material,which can not react with water or hydration products,but still indirectly influences the hydration in a positive way. In the experimental program,non-evaporable water test was carried out to determine the degree of hydration of cement paste with and without micronized sands. The influence of different finenesses of sand particles,240 m2/kg,400 m2/kg and 1 300 m2/kg,and different curing ages were investigated. The SEM image analysis was used to characterize the morphological changes of microstructure by the presence of the micronized sand during the cement hydration process. Hydration reaction is enhanced by the use of inert micronized sands. The fineness of micronized sands influences the degree of hydration a lot. The fineness factor has been taken into account in the simulation. There is a clear interface area between sand particle and hydration products.
基金Funded by Key Laboratory for Comprehensive Energy Saving of Cold Regions Architecture of Ministry of Education(No.JLJZHDKF202204)。
文摘This paper studied the effects of different retarders on the performance of the"one-step"alkali-activated composite cementitious material(ACCM)which is composed of ground granulated blast slag(GGBS)and fly ash(FA),and analyzed its mechanical properties,hydration mechanism,and retardation mechanism.The effects of retarders on the hydration products,mechanical properties,and hydration kinetics of ACCM were investigated using XRD,SEM,FTIR,EDS,and thermoactive microcalorimetry.The results showed that Na_(2)B_(4)O_(7)·10H_(2)O(B)delayed the exotherm during the alkali activation process and could effectively delay the setting time of ACCM,but the mechanical properties were slightly decreased.The setting time of ACCM increased with the increase in SG content,but the mechanical properties of ACCM decreased with the increase in SG content.C1_(2)H_(22)O_(11)(CHO)could effectively delay the hydration reaction of ACCM and weakly enhanced the compressive strength.H_(3)PO_(4)(HP)at a concentration of 0.05 mol/L had a certain effect on ACCM retardation,but HP at a concentration of 0.07 and 0.09 mol/L had an effect of promoting the setting and hardening time of ACCM.
基金Funded by the National Natural Science Foundation of China(No.51574055)the Natural Science Foundation of Liaoning Province(No.20170540143)
文摘To obtain the compositions and microstructure of hydration products of cementitious material in different hydration ages and its growth law of filling strength, the optimal proportion of composite cementitious material was determined according to the chemical composition of cement clinker which was composed of the Portland cement 32.5R, CSA 42.5 sulphoaluminate cement and two gypsum（CS）. The characterization of composite cementitious materials in different hydration ages was conducted by NMR, XRD and SEM techniques. The mechanism of hydration was explored. It is shown that the compressive strength of the test block increases gradually with the increase of hydration age. The microstructure of composite cementitious material can be changed from Al-O octahedron into Al-O tetrahedron in the hydration process. The hydrated alkali alumi niumsilicate formed with Si-O tetrahedron and Al-O tetrahedron. The degree of polymerization of Si-O tetrahedron gradually increased, and the structural strength of cementitious materials continued to increase. The diffraction peak of clinker minerals gradually decreased with the extension of hydration age. The CaSO4 completely hydrated to produce Aft during hydration which resulted in high early strength of cementitious material. The early hydration product of composite cementitious materials was Aft with a needle bar structure. The main middle and last hydration products were CSH gel and CH gel with dense prismatic shape. The microscopic pore of composite cementitious material gradually decreased and improved the later strength of filling block. The strong support was provided for mined-out area.
基金Funded by the National Natural Science Foundation of China(Nos.51302104,51472109)Science and Technology Development Plan of Shandong Province(No.2014G-ZX208001)the Program for Scientific Research Innovation Team in Colleges and Universities of Shandong Province
文摘This paper aimed to improve the water-retention performance and basic physical properties of sulfoaluminate cement（SAC）-based planting cementitious material. The effect of natural zeolite on the performance of SAC-based planting material was investigated. The water-retention performance, porosity, compressive strength, and alkalinity had been tested and TG-DSC analysis had been adopted in this paper. Experimental results showed that zeolite was effective to improve the water-retention capacity and 10%, 20% and 30% natural zeolite increased the pore volume of the hardened pastes by 10.6%, 26.0%, and 38.6%, especially pore size below 0.1 μm was increased by 9.7%, 26.2% and 17.5%. And 10% zeolite was beneficial to the compressive strengths of cementitious material and 1, 3, and 28 d compressive strength reached up to 35.9, 55.0, 80.3 MPa. Furthermore zeolite decreased the alkalinity of pore fluid of hardened cementitious material, while the addition of zeolite reached up to 30%, the alkalinity of pore fluid of hardened cementitious material decreased by 8.9%. Therefore zeolite was suitable for improving the performance of SAC-based planting cementitious material.
文摘Experimental investigation was conducted on the effects of gypsum types and SO 3 content on the fluidity and strengths of different cementitious systems.The experimental results show that influences of gypsum in various cementitious materials are different.For cementitious materials blended with various proportions of slag fly ash and 5% gypsum content,influences of gypsum and calcined gypsum on the fluidity and flexural/compressive strength are similar.It is revealed that 'combination effect' and 'synergistic effect' of slag and fly ash play an important role during hydration.For cementitious materials with 45% clinkers,30%slag,20%fly ash and 5%limestone,the optimized SO 3 contents in gypsum and calcined gypsum are 3.13% and 3.51% respectively and the optimized gypsum content is 6.5%.While both of them are blended,the optimum ratio of gypsum to calcined gypsum is 40%∶60%(total gypsum content 6.5%),correspondingly the optimum ratio of SO 3 is 19.3%∶32.4%.
