The total utilization amount of red mud is limited due to its high content of alkali,heavy metals and naturally occurring radioactive element.In order to rationalize the use of red mud,a typical field road cement usin...The total utilization amount of red mud is limited due to its high content of alkali,heavy metals and naturally occurring radioactive element.In order to rationalize the use of red mud,a typical field road cement using dealkalized red mud(content of alkali lower than 1%) as raw material was firstly prepared in this paper.Then,a preliminary research on the radioactivity of the red mud based field road cement has been carried out.For that reason,two samples of raw materials were prepared.One was with ordinary raw materials,as the control group(CG),the other was with 23 w % red mud,as the experimental group(EG).The clinkers were acquired by sintering the above two raw materials at 1 400 ℃.Subsequently,the two types of cement prepared by the above two kinds of clinkers were tested by measuring the normal consistency,setting time,mechanical strength and drying shrinkage.Meanwhile,the hydration products of the two types of cement were examined by XRD analysis at the curing age of 6 hours,1,3,7,and 28 days,respectively.The radioactivity of the two kinds of cement clinkers was then measured by gamma-ray spectrometry.The experimental results indicate that the main mineralogical phases components in the EG field road cement clinkers are C3S,C2S,and C4AF,the 28 days flexural and compressive strength of the EG field road cement mortars could be up to 8.45 and 53.2 MPa,respectively.The radioactive measuring results of the EG field road cement show that the value of radium equivalent activity index(Raeq) is 254.8 Bq/Kg-1,which is lower than the upper limit.展开更多
The relationships between microstructure and melting temperature of slag containing different heavy metals (Zn, Cu, Pb and Cr) were studied. Furthermore, the corresponding solidification mechanism and rule of heavy ...The relationships between microstructure and melting temperature of slag containing different heavy metals (Zn, Cu, Pb and Cr) were studied. Furthermore, the corresponding solidification mechanism and rule of heavy metals were analyzed by microscopic tests during melting and reconstructing process. Based on preliminary results, three conclusions were derived. Firstly, pure slag would begin to melt when the temperature reached 1 180℃; however, Zn did not play any fluxing action. Secondly, upon adding Cu and Pb, the initial melting temperature of slag decreased by 5-8℃ and their fluxing effect was observed. Thirdly, the initial melting temperature and the reaction time for slag decreased by 22℃ and 6 s respectively after adding Cr; the fluxing action was significant under Cr. The results of X-ray diffraction (XRD) and Fourier transform infrared spectroscope (FTIR) analyses showed that the above heavy metals had little influence on the reconstruction of slag. Toxicity characteristic leaching procedure (TCLP) leaching tests showed a good solidification effect of the heavy metals with melting slag, fixation rate of Zn, Cu, Pb and Cr was 36.3%, 24.6%, 9.2% and 93.2%, respectively. The leaching toxicity of the heavy metals met the requirements for environmental emission after solidification treatment.展开更多
β-SiAION hollow spheres were prepared by carbothermal reduction method, using coal fly ash ( 〈 15 μm, 43 - 77 μm, and 〉 100 μm) and active carbon in Some proportion (20% less than theoretical addition, theore...β-SiAION hollow spheres were prepared by carbothermal reduction method, using coal fly ash ( 〈 15 μm, 43 - 77 μm, and 〉 100 μm) and active carbon in Some proportion (20% less than theoretical addition, theoretical addition and 10% excess theoretical addition) as starting materials, putting into alumina crucible in high temperature nitriding furnace after well mixed, and holding at 1 300 ℃, 1 350 ℃, 1 400 ℃, 1 450 ℃, and 1 500 ℃ for 6 h. Effects of temperature, particle size of the microsphere . and addition of active carbon on the phase composition and microstructure of the nitridized products were studied by means of XRD and SEM. The results show that the nitridation reaction starts at 1 300 ℃ ; excess active carbon is necessary to form β-SiAION hollow spheres, and particle size is the important parameter to form the hollow spheres nitridized products β-SiAION; at 1 500 ℃, when the active carbon is 10% in excess, the β-SiAlON hollow spheres, which were prepared using coal fly ash with particle size 〉 100 μm, are featured with rough surface, high hollowness and low density.展开更多
An accelerated laboratory method(saturated ammonium nitrate solution immersion method) was used to analyze the degradation of cement decalcification process. By studying the changes of intensity, volume, elastic mod...An accelerated laboratory method(saturated ammonium nitrate solution immersion method) was used to analyze the degradation of cement decalcification process. By studying the changes of intensity, volume, elastic modulus, quality, p H value, the Ca/Si, and mineral phase, it could be found that the first cement decalcification degradation process was the decalcification of calcium hydroxide, and then CSH gel, AFm, etc. The secondary ettringite deposition happened and the decalcification degradation depth was proportional to the square root of time. Moreover, the corresponding strength of cement would be gradually reduced, cement rock volume shrinkage occurred, p H values decreased, the surface elastic modulus decreased down to a certain level, and slightly changed and the Ca/Si was 3.1 from the beginning and lasted down to 1.3.展开更多
基金Funded by the National Natural Science Foundation of China(No.51172155)
文摘The total utilization amount of red mud is limited due to its high content of alkali,heavy metals and naturally occurring radioactive element.In order to rationalize the use of red mud,a typical field road cement using dealkalized red mud(content of alkali lower than 1%) as raw material was firstly prepared in this paper.Then,a preliminary research on the radioactivity of the red mud based field road cement has been carried out.For that reason,two samples of raw materials were prepared.One was with ordinary raw materials,as the control group(CG),the other was with 23 w % red mud,as the experimental group(EG).The clinkers were acquired by sintering the above two raw materials at 1 400 ℃.Subsequently,the two types of cement prepared by the above two kinds of clinkers were tested by measuring the normal consistency,setting time,mechanical strength and drying shrinkage.Meanwhile,the hydration products of the two types of cement were examined by XRD analysis at the curing age of 6 hours,1,3,7,and 28 days,respectively.The radioactivity of the two kinds of cement clinkers was then measured by gamma-ray spectrometry.The experimental results indicate that the main mineralogical phases components in the EG field road cement clinkers are C3S,C2S,and C4AF,the 28 days flexural and compressive strength of the EG field road cement mortars could be up to 8.45 and 53.2 MPa,respectively.The radioactive measuring results of the EG field road cement show that the value of radium equivalent activity index(Raeq) is 254.8 Bq/Kg-1,which is lower than the upper limit.
基金Funded by the National Natural Science Foundation of China(Nos.51202222,51002110)the State Key Laboratory of Silicate Materials for Architectures(Wuhan University of Technology)(No.SYSJJ2013-07)
文摘The relationships between microstructure and melting temperature of slag containing different heavy metals (Zn, Cu, Pb and Cr) were studied. Furthermore, the corresponding solidification mechanism and rule of heavy metals were analyzed by microscopic tests during melting and reconstructing process. Based on preliminary results, three conclusions were derived. Firstly, pure slag would begin to melt when the temperature reached 1 180℃; however, Zn did not play any fluxing action. Secondly, upon adding Cu and Pb, the initial melting temperature of slag decreased by 5-8℃ and their fluxing effect was observed. Thirdly, the initial melting temperature and the reaction time for slag decreased by 22℃ and 6 s respectively after adding Cr; the fluxing action was significant under Cr. The results of X-ray diffraction (XRD) and Fourier transform infrared spectroscope (FTIR) analyses showed that the above heavy metals had little influence on the reconstruction of slag. Toxicity characteristic leaching procedure (TCLP) leaching tests showed a good solidification effect of the heavy metals with melting slag, fixation rate of Zn, Cu, Pb and Cr was 36.3%, 24.6%, 9.2% and 93.2%, respectively. The leaching toxicity of the heavy metals met the requirements for environmental emission after solidification treatment.
文摘β-SiAION hollow spheres were prepared by carbothermal reduction method, using coal fly ash ( 〈 15 μm, 43 - 77 μm, and 〉 100 μm) and active carbon in Some proportion (20% less than theoretical addition, theoretical addition and 10% excess theoretical addition) as starting materials, putting into alumina crucible in high temperature nitriding furnace after well mixed, and holding at 1 300 ℃, 1 350 ℃, 1 400 ℃, 1 450 ℃, and 1 500 ℃ for 6 h. Effects of temperature, particle size of the microsphere . and addition of active carbon on the phase composition and microstructure of the nitridized products were studied by means of XRD and SEM. The results show that the nitridation reaction starts at 1 300 ℃ ; excess active carbon is necessary to form β-SiAION hollow spheres, and particle size is the important parameter to form the hollow spheres nitridized products β-SiAION; at 1 500 ℃, when the active carbon is 10% in excess, the β-SiAlON hollow spheres, which were prepared using coal fly ash with particle size 〉 100 μm, are featured with rough surface, high hollowness and low density.
基金Funded by the Natural Science Foundation of Ministry of Housing and Urban-Rural Development of the People's Republic of China(No.2009-K4-27)
文摘An accelerated laboratory method(saturated ammonium nitrate solution immersion method) was used to analyze the degradation of cement decalcification process. By studying the changes of intensity, volume, elastic modulus, quality, p H value, the Ca/Si, and mineral phase, it could be found that the first cement decalcification degradation process was the decalcification of calcium hydroxide, and then CSH gel, AFm, etc. The secondary ettringite deposition happened and the decalcification degradation depth was proportional to the square root of time. Moreover, the corresponding strength of cement would be gradually reduced, cement rock volume shrinkage occurred, p H values decreased, the surface elastic modulus decreased down to a certain level, and slightly changed and the Ca/Si was 3.1 from the beginning and lasted down to 1.3.