When the castable refractory linings are installed without drying out sufficiently and exposed to high humidity for a long time,white fibrous or powdery substance appears on the surface,which is called“efflorescence...When the castable refractory linings are installed without drying out sufficiently and exposed to high humidity for a long time,white fibrous or powdery substance appears on the surface,which is called“efflorescence”.The main reason is the cement of castable refractory linings contacts with C02 and moisture in the atmosphere to form calcium carbonate(CaC03).In general,efflorescence takes place more readily in lightweight castable refractories.In the walking beam reheating furnace construction project,there are many white powdery substances in the walking beams,because the construction procedure causes poor ventilation in the surrounding area,and the internal moisture of castable refractory linings cannot be evaporated effectively.In future,the project programming should consider the environmental humidity and surrounding ventilation.展开更多
Blended fly ash/blast-furnace slag geopolymers are focused on due to their excellent mechanical and chemical resistant properties. We investigated the effect of slag partial substitution for fly ash on the efflorescen...Blended fly ash/blast-furnace slag geopolymers are focused on due to their excellent mechanical and chemical resistant properties. We investigated the effect of slag partial substitution for fly ash on the efflorescence of the resulting geopolymers. The efflorescence of geopolymer binders was inspected and evaluated through leaching tests. The efflorescence deposits on surface of the geopolymer binders were analyzed using XRD and SEM-EDS. The results showed that sodium and calcium cations leached from geopolymer binders reacted with the atmospheric CO_2 and formed the crystal deposits, gaylussite and calcite, in the forms of granular and angular crystal particles. The slag addition led to a refinement of the pore structure of fly ash-based geopolymers, but an increment in the concentration of alkali leaching. The crystal deposits gradually developed in the pore volume of the binders, and finally exceeded the capacity of pore volume. The extent of efflorescence on the surface of specimens increased with the slag substitution. The visible efflorescence is therefore a result of available alkalis and pore sizes and volumes. Higher concentration of available alkalis and smaller pores(and volume) will lead to more intensive efflorescence.展开更多
This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na<sub>2</sub>...This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>): the soundness, sulfate resistance, alkali-silica reactivity and efflorescence factors are considered. Results of tests show that such mortars are resistant to alkali-silica expansion. Mortars are also sulfate-resistant when the amount of HCFA in the complex binder is within a limit of 10 wt%. The fineness of fly ash determines its’ ability to activate GGBFS hydration, and influence soundness of the binder, early strength development, sulfate resistance and efflorescence behavior. The present article is a continuation of authors’ work, previously published in MSA, Vol. 14, 240-254.展开更多
为了降低碱激发偏高岭土地聚物的泛碱程度,采用具备阳离子交换性能的改性5A沸石降低地聚物孔隙中游离碱金属阳离子的含量。通过地聚物的抗压强度测试、孔结构分析(BET)、微观形貌分析(SEM-EDS)等方法探究改性5A沸石对地聚物微观结构和...为了降低碱激发偏高岭土地聚物的泛碱程度,采用具备阳离子交换性能的改性5A沸石降低地聚物孔隙中游离碱金属阳离子的含量。通过地聚物的抗压强度测试、孔结构分析(BET)、微观形貌分析(SEM-EDS)等方法探究改性5A沸石对地聚物微观结构和宏观性能的影响。通过电感耦合等离子原子发射光谱仪(ICP-OES)检测浸出液中阳离子含量,利用Image Pro Plus软件计算在固定泛碱模式下地聚物的泛碱面积,评估改性5A沸石对地聚物泛碱程度的影响,并揭示改性5A沸石对地聚物中Na^(+)和Ca^(2+)迁移规律的影响。结果表明,掺量为4%(质量分数)的改性5A沸石既能通过内养护和微集料效应优化孔结构,增强地聚物的力学性能,又能与孔溶液进行阳离子交换,形成(N,C)-A-S-H凝胶;Na+浸出量降低了19.4%,地聚物表观泛碱程度降低了57.3%。展开更多
文摘When the castable refractory linings are installed without drying out sufficiently and exposed to high humidity for a long time,white fibrous or powdery substance appears on the surface,which is called“efflorescence”.The main reason is the cement of castable refractory linings contacts with C02 and moisture in the atmosphere to form calcium carbonate(CaC03).In general,efflorescence takes place more readily in lightweight castable refractories.In the walking beam reheating furnace construction project,there are many white powdery substances in the walking beams,because the construction procedure causes poor ventilation in the surrounding area,and the internal moisture of castable refractory linings cannot be evaporated effectively.In future,the project programming should consider the environmental humidity and surrounding ventilation.
基金Funded by the Jiangsu Higher Education Institutions for a project PAPD(Priority Academic Program Development),Program for Changjiang Scholars and Innovative Research Team in University(PCSIRT)(No.IRT1146)+1 种基金Graduate Education Innovation Project in Jiangsu Province(No.CXLX13_409)supported by University of Southern Queensland and an ARC-linkage project
文摘Blended fly ash/blast-furnace slag geopolymers are focused on due to their excellent mechanical and chemical resistant properties. We investigated the effect of slag partial substitution for fly ash on the efflorescence of the resulting geopolymers. The efflorescence of geopolymer binders was inspected and evaluated through leaching tests. The efflorescence deposits on surface of the geopolymer binders were analyzed using XRD and SEM-EDS. The results showed that sodium and calcium cations leached from geopolymer binders reacted with the atmospheric CO_2 and formed the crystal deposits, gaylussite and calcite, in the forms of granular and angular crystal particles. The slag addition led to a refinement of the pore structure of fly ash-based geopolymers, but an increment in the concentration of alkali leaching. The crystal deposits gradually developed in the pore volume of the binders, and finally exceeded the capacity of pore volume. The extent of efflorescence on the surface of specimens increased with the slag substitution. The visible efflorescence is therefore a result of available alkalis and pore sizes and volumes. Higher concentration of available alkalis and smaller pores(and volume) will lead to more intensive efflorescence.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20073004, No.20473012, No.20673010, and No.20640420450）, the 111 Project B07012, and the China Postdoctoral Science Foundation （No.20070410466）. The Trans-Century Training Program Foundation for the Talents by the Ministry of Education of China was also gratefully acknowledged.
文摘This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>): the soundness, sulfate resistance, alkali-silica reactivity and efflorescence factors are considered. Results of tests show that such mortars are resistant to alkali-silica expansion. Mortars are also sulfate-resistant when the amount of HCFA in the complex binder is within a limit of 10 wt%. The fineness of fly ash determines its’ ability to activate GGBFS hydration, and influence soundness of the binder, early strength development, sulfate resistance and efflorescence behavior. The present article is a continuation of authors’ work, previously published in MSA, Vol. 14, 240-254.
文摘为了降低碱激发偏高岭土地聚物的泛碱程度,采用具备阳离子交换性能的改性5A沸石降低地聚物孔隙中游离碱金属阳离子的含量。通过地聚物的抗压强度测试、孔结构分析(BET)、微观形貌分析(SEM-EDS)等方法探究改性5A沸石对地聚物微观结构和宏观性能的影响。通过电感耦合等离子原子发射光谱仪(ICP-OES)检测浸出液中阳离子含量,利用Image Pro Plus软件计算在固定泛碱模式下地聚物的泛碱面积,评估改性5A沸石对地聚物泛碱程度的影响,并揭示改性5A沸石对地聚物中Na^(+)和Ca^(2+)迁移规律的影响。结果表明,掺量为4%(质量分数)的改性5A沸石既能通过内养护和微集料效应优化孔结构,增强地聚物的力学性能,又能与孔溶液进行阳离子交换,形成(N,C)-A-S-H凝胶;Na+浸出量降低了19.4%,地聚物表观泛碱程度降低了57.3%。
