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
In this paper, a high calcium high sulfate ash as the main material, adding fly ash, lime, cement, gypsum and some modifiers to prepare autoclaved aerated concrete. The products complies with the technical requirement...In this paper, a high calcium high sulfate ash as the main material, adding fly ash, lime, cement, gypsum and some modifiers to prepare autoclaved aerated concrete. The products complies with the technical requirements of GB/T11968-2006. This paper also studies the influence of the physical methods and water ratio on autoclaved aerated concrete by high calcium high sulfate ash aerated concrete. The best ratio of water and Grinding time were found in practice study.展开更多
High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace sla...High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace slag (GGBFS). Substitution of 10% - 30% of GGBFS by HCFA and premixing of 1% - 3% Na2CO3 to this dry binary binder was discovered to give mortar compression strength of 10 - 30 to 30 - 45 MPa at 7 and 28 days when moist cured at ambient temperature. High-calcium fly ash produced from low-temperature combustion of fuel, like in circulating fluidized bed technology, reacts with water readily and is itself a good hardening activator for GGBFS, so introduction of Na<sub>2</sub>CO<sub>3</sub> into such mix has no noticeable effect on the mortar strength. However, low-temperature HCFA has higher water demand, and the strength of mortar is compromised by this factor. As of today, our research is still ongoing, and we expect to publish more data on different aspects of durability of proposed GGBFS-HCFA binder later.展开更多
The feasibility of high calcium fly ash （CFA）-based geopolymers to fix heavy metals were studied. The CFA-based geopolymers were prepared from CFA, flue gas desulfurization gypsum （FGDG）, and water treatment resid...The feasibility of high calcium fly ash （CFA）-based geopolymers to fix heavy metals were studied. The CFA-based geopolymers were prepared from CFA, flue gas desulfurization gypsum （FGDG）, and water treatment residual （WTR）. The static leaching showed that heavy metals concentrations from CFA- based geopolymers were lower than their maximum concentration limits according to the U.S. environmental protection law. And the encapsulated and fixed ratios of heavy metals by the CFA-based geopolymers were 96.02%-99.88%. The dynamic real-time leaching experiment showed that concentration of Pb （II） was less than 1.μg / L, Cr （VI） less than 3.25 mg / L, while Hg （II） less than 4.0 μg / L. Additionally, dynamic accumulated leaching concentrations were increased at the beginning of leaching process then kept stable. During the dynamic leaching process, heavy metals migrated and accumulated in an area near to the solid-solution interface. When small part of heavy metals in ＂the accumulated area＂ breached through the threshold value of physical encapsulation and chemical fixation they migrated into solution. The dynamic leaching ratios and effective diffusion coefficients of heavy metals from CFA-based geopolymer were very low and the long-term security of heavy metals in CFA-based geopolymer was safe.展开更多
为改善高钙粉煤灰在混凝土中的体积安定性和水化活性,本文对高钙粉煤灰进行了CO_(2)矿化改性,研究了不同CO_(2)矿化反应时长下高钙粉煤灰的固碳量和游离氧化钙含量,及CO_(2)矿化改性高钙粉煤灰对水泥砂浆水化热、力学性能和孔隙结构的...为改善高钙粉煤灰在混凝土中的体积安定性和水化活性,本文对高钙粉煤灰进行了CO_(2)矿化改性,研究了不同CO_(2)矿化反应时长下高钙粉煤灰的固碳量和游离氧化钙含量,及CO_(2)矿化改性高钙粉煤灰对水泥砂浆水化热、力学性能和孔隙结构的影响。结果表明,经12 h CO_(2)矿化改性处理,高钙粉煤灰固碳量可超过10%(质量分数),高钙粉煤灰中的游离氧化钙含量明显降低。随着矿化反应时间的延长,掺高钙粉煤灰的水泥浆体水化诱导期缩短,早期水化放热量明显降低。CO_(2)矿化改性处理还能减轻高钙粉煤灰对水泥砂浆强度的负面影响,改善水泥砂浆孔隙结构,降低孔隙率和大孔含量,促进水泥的早期水化和水化硅酸钙的成核结晶。展开更多
为提高高钙粉煤灰在混凝土中的水化活性和体积安定性,分别以原状、CO_(2)矿化预处理6、24 h的3种高钙粉煤灰为单一前驱体制备了地聚物,研究了矿化程度对高钙粉煤灰理化特性的影响,并分析其作用机理。结果表明,经6、24 h CO_(2)矿化预处...为提高高钙粉煤灰在混凝土中的水化活性和体积安定性,分别以原状、CO_(2)矿化预处理6、24 h的3种高钙粉煤灰为单一前驱体制备了地聚物,研究了矿化程度对高钙粉煤灰理化特性的影响,并分析其作用机理。结果表明,经6、24 h CO_(2)矿化预处理的高钙粉煤灰中f-CaO含量比原状高钙粉煤灰降低了2.64、2.80个百分点。采用6 h CO_(2)矿化预处理高钙粉煤灰制备的地聚物1 d抗压强度可达29.7 MPa,比原状高钙粉煤灰制备的提高了34.4%。经6 h CO_(2)矿化预处理可以促进水化产物的生成和成核结晶。但CO_(2)矿化预处理时间过长(24 h)时,不利于高钙粉煤灰基地聚物的强度发展。展开更多
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In this paper, a high calcium high sulfate ash as the main material, adding fly ash, lime, cement, gypsum and some modifiers to prepare autoclaved aerated concrete. The products complies with the technical requirements of GB/T11968-2006. This paper also studies the influence of the physical methods and water ratio on autoclaved aerated concrete by high calcium high sulfate ash aerated concrete. The best ratio of water and Grinding time were found in practice study.
文摘High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace slag (GGBFS). Substitution of 10% - 30% of GGBFS by HCFA and premixing of 1% - 3% Na2CO3 to this dry binary binder was discovered to give mortar compression strength of 10 - 30 to 30 - 45 MPa at 7 and 28 days when moist cured at ambient temperature. High-calcium fly ash produced from low-temperature combustion of fuel, like in circulating fluidized bed technology, reacts with water readily and is itself a good hardening activator for GGBFS, so introduction of Na<sub>2</sub>CO<sub>3</sub> into such mix has no noticeable effect on the mortar strength. However, low-temperature HCFA has higher water demand, and the strength of mortar is compromised by this factor. As of today, our research is still ongoing, and we expect to publish more data on different aspects of durability of proposed GGBFS-HCFA binder later.
基金Funded by the National Natural Science Foundation of China(Nos.51208370,51172164)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20110072120046)
文摘The feasibility of high calcium fly ash （CFA）-based geopolymers to fix heavy metals were studied. The CFA-based geopolymers were prepared from CFA, flue gas desulfurization gypsum （FGDG）, and water treatment residual （WTR）. The static leaching showed that heavy metals concentrations from CFA- based geopolymers were lower than their maximum concentration limits according to the U.S. environmental protection law. And the encapsulated and fixed ratios of heavy metals by the CFA-based geopolymers were 96.02%-99.88%. The dynamic real-time leaching experiment showed that concentration of Pb （II） was less than 1.μg / L, Cr （VI） less than 3.25 mg / L, while Hg （II） less than 4.0 μg / L. Additionally, dynamic accumulated leaching concentrations were increased at the beginning of leaching process then kept stable. During the dynamic leaching process, heavy metals migrated and accumulated in an area near to the solid-solution interface. When small part of heavy metals in ＂the accumulated area＂ breached through the threshold value of physical encapsulation and chemical fixation they migrated into solution. The dynamic leaching ratios and effective diffusion coefficients of heavy metals from CFA-based geopolymer were very low and the long-term security of heavy metals in CFA-based geopolymer was safe.
文摘为改善高钙粉煤灰在混凝土中的体积安定性和水化活性,本文对高钙粉煤灰进行了CO_(2)矿化改性,研究了不同CO_(2)矿化反应时长下高钙粉煤灰的固碳量和游离氧化钙含量,及CO_(2)矿化改性高钙粉煤灰对水泥砂浆水化热、力学性能和孔隙结构的影响。结果表明,经12 h CO_(2)矿化改性处理,高钙粉煤灰固碳量可超过10%(质量分数),高钙粉煤灰中的游离氧化钙含量明显降低。随着矿化反应时间的延长,掺高钙粉煤灰的水泥浆体水化诱导期缩短,早期水化放热量明显降低。CO_(2)矿化改性处理还能减轻高钙粉煤灰对水泥砂浆强度的负面影响,改善水泥砂浆孔隙结构,降低孔隙率和大孔含量,促进水泥的早期水化和水化硅酸钙的成核结晶。
文摘为提高高钙粉煤灰在混凝土中的水化活性和体积安定性,分别以原状、CO_(2)矿化预处理6、24 h的3种高钙粉煤灰为单一前驱体制备了地聚物,研究了矿化程度对高钙粉煤灰理化特性的影响,并分析其作用机理。结果表明,经6、24 h CO_(2)矿化预处理的高钙粉煤灰中f-CaO含量比原状高钙粉煤灰降低了2.64、2.80个百分点。采用6 h CO_(2)矿化预处理高钙粉煤灰制备的地聚物1 d抗压强度可达29.7 MPa,比原状高钙粉煤灰制备的提高了34.4%。经6 h CO_(2)矿化预处理可以促进水化产物的生成和成核结晶。但CO_(2)矿化预处理时间过长(24 h)时,不利于高钙粉煤灰基地聚物的强度发展。
