Physical and mechanical properties variations of lithium slag were systematically investigated by three different ways such as physical, chemical activation, physical-chemical combined activation. Mechanisms of the ce...Physical and mechanical properties variations of lithium slag were systematically investigated by three different ways such as physical, chemical activation, physical-chemical combined activation. Mechanisms of the cementitious properties and hydration process of lithium slag composite cement were studied by XRD and SEM. The results showed that specific surface area increased from 254 to 700 m2/kg while median particle size decreased from 14.97 to 8.45 urn with the increase of grinding time. Physical, chemical activation and combined activation improved the strength and hydration degree of lithium slag composite cement. Compared with original lithium slag, the flexural strength and compressive strength of mortars were improved significantly with the increase of grinding time. A higher strength of the cement with the lithium slag was attained; The sample with 10% lithium slag got the highest strength when the grinding time was 10 min; the compressive strength was higher than OPC at 28 days, which increased by 12.3%. When the Na2SO4 content was 0.6%, the compressive strength increased by 1.4%; when the Al2（SO4）3·18H2O content was 0.4%, the compressive strength increased by 5.8% at 28 days. Compared with the late strength, the improving degree of early strength was larger with the incorporation of activator. The results of XRD and SEM were consistent with the results of mechanical properties; it is also evident that lithium slag composite cement hydration products were mainly AFt, Ca（OH）2, CaSO4·2H2O, and C-S-H gel.展开更多
In a recent investigation Mills and Riaz [1] showed that industrial oxide refractory corrosion by liquid oxides could be changed by the application of a small voltage across the liquid oxide-refractory interface. They...In a recent investigation Mills and Riaz [1] showed that industrial oxide refractory corrosion by liquid oxides could be changed by the application of a small voltage across the liquid oxide-refractory interface. They explained their result in terms of penetration of the refractory pores with liquid oxide. Their analysis of the corrosion effect was to some degree limited by the use of an industrial refractory material in the study. Further, it was not clear whether their findings were limited to solely industrial refractories or had wider ranging application to more dense ceramic type solid oxide systems. In this study, a simpler and more easily characterized solid oxide (dense MgO) has been used to examine the effects of an applied voltage on the solid oxide in a liquid oxide melt. The dissolution rate of an MgO ceramic in a CaO-SiO2-Al2O3 and CaO-SiO2- Fe2O3-FeO-MgO liquid oxide composition at various applied voltages has been measured at 1540°C. It was found that the MgO corrosion in the CaO-SiO2-Al2O3 system was insensitive to an applied voltage over the voltage range –0.5 to 0.3 V. In the CaO-SiO2-Fe2O3-FeO-MgO liquid oxide system the MgO corrosion rate showed a maximum at –0.45 V. This effect has been explained by considering the consequences of an applied voltage on the rate of Marangoni flow at the liquid oxide-refractory-gas interface and in turn, the flow effect on the rate of the mass transfer controlled MgO dissolution reaction.展开更多
The time-dependent rheological behaviors of alkali-activated cement(AAC)are expected to be precisely controlled,in order to meet the requirements of modern engineering practices.In this paper,the effects of activator,...The time-dependent rheological behaviors of alkali-activated cement(AAC)are expected to be precisely controlled,in order to meet the requirements of modern engineering practices.In this paper,the effects of activator,including the Na_(2)O concentration and SiO_(2)/Na_(2)O(S/N)molar ratio,on the rheological behavior of alkali-activated slag fly ash pastes were investigated.The small amplitude oscillatory shear(SAOS)and shear test were used to evaluate the structural build-up and flowability of pastes.Besides,zeta potential measurement,calorimetric test and thermogravimetric analysis(TGA)were carried out to reveal the physico-chemical mechanisms behind the rheological evolution of fresh pastes.It was found that high Na_(2)O concentration and low S/N molar ratio improved the flowability and structural build-up rate of paste.Moreover,the structural build-up of alkali-activated slag-fly ash pastes consists of two stages,which is controlled by the dissolution of solid reactants and formation of C-(A)-S-H gels,respectively.展开更多
基金Funded partly by the National Natural Science Foundation of China(Nos.51378408,51408448)State Key Laboratory of Silicate Materials for Architectures(Wuhan University of Technology)(No.SYSJJ2013-07)
文摘Physical and mechanical properties variations of lithium slag were systematically investigated by three different ways such as physical, chemical activation, physical-chemical combined activation. Mechanisms of the cementitious properties and hydration process of lithium slag composite cement were studied by XRD and SEM. The results showed that specific surface area increased from 254 to 700 m2/kg while median particle size decreased from 14.97 to 8.45 urn with the increase of grinding time. Physical, chemical activation and combined activation improved the strength and hydration degree of lithium slag composite cement. Compared with original lithium slag, the flexural strength and compressive strength of mortars were improved significantly with the increase of grinding time. A higher strength of the cement with the lithium slag was attained; The sample with 10% lithium slag got the highest strength when the grinding time was 10 min; the compressive strength was higher than OPC at 28 days, which increased by 12.3%. When the Na2SO4 content was 0.6%, the compressive strength increased by 1.4%; when the Al2（SO4）3·18H2O content was 0.4%, the compressive strength increased by 5.8% at 28 days. Compared with the late strength, the improving degree of early strength was larger with the incorporation of activator. The results of XRD and SEM were consistent with the results of mechanical properties; it is also evident that lithium slag composite cement hydration products were mainly AFt, Ca（OH）2, CaSO4·2H2O, and C-S-H gel.
文摘In a recent investigation Mills and Riaz [1] showed that industrial oxide refractory corrosion by liquid oxides could be changed by the application of a small voltage across the liquid oxide-refractory interface. They explained their result in terms of penetration of the refractory pores with liquid oxide. Their analysis of the corrosion effect was to some degree limited by the use of an industrial refractory material in the study. Further, it was not clear whether their findings were limited to solely industrial refractories or had wider ranging application to more dense ceramic type solid oxide systems. In this study, a simpler and more easily characterized solid oxide (dense MgO) has been used to examine the effects of an applied voltage on the solid oxide in a liquid oxide melt. The dissolution rate of an MgO ceramic in a CaO-SiO2-Al2O3 and CaO-SiO2- Fe2O3-FeO-MgO liquid oxide composition at various applied voltages has been measured at 1540°C. It was found that the MgO corrosion in the CaO-SiO2-Al2O3 system was insensitive to an applied voltage over the voltage range –0.5 to 0.3 V. In the CaO-SiO2-Fe2O3-FeO-MgO liquid oxide system the MgO corrosion rate showed a maximum at –0.45 V. This effect has been explained by considering the consequences of an applied voltage on the rate of Marangoni flow at the liquid oxide-refractory-gas interface and in turn, the flow effect on the rate of the mass transfer controlled MgO dissolution reaction.
基金Project(2017 YFB 0310100)supported by National Key R&D Program of ChinaProjects(51778629,51922109)supported by the National Natural Science Foundation of ChinaProjects(2020 zzts 617,2020 CX 011)supported by the Innovation-Driven Project of Central South University,China。
文摘The time-dependent rheological behaviors of alkali-activated cement(AAC)are expected to be precisely controlled,in order to meet the requirements of modern engineering practices.In this paper,the effects of activator,including the Na_(2)O concentration and SiO_(2)/Na_(2)O(S/N)molar ratio,on the rheological behavior of alkali-activated slag fly ash pastes were investigated.The small amplitude oscillatory shear(SAOS)and shear test were used to evaluate the structural build-up and flowability of pastes.Besides,zeta potential measurement,calorimetric test and thermogravimetric analysis(TGA)were carried out to reveal the physico-chemical mechanisms behind the rheological evolution of fresh pastes.It was found that high Na_(2)O concentration and low S/N molar ratio improved the flowability and structural build-up rate of paste.Moreover,the structural build-up of alkali-activated slag-fly ash pastes consists of two stages,which is controlled by the dissolution of solid reactants and formation of C-(A)-S-H gels,respectively.
基金Chinese National Programs for High Technology Research and Development(2010AA03A405,2012AA062303)National Natural Science Foundation of China(51004033,51204040)+1 种基金National Science and Technology Support Program(2012BAE01B02)Doctoral Fund Project(20120042110011)
