文献类型：期刊文献

英文题名：Unraveling the Interactive Effects of Na/Al, Si/Al and Calcium on the Properties of Geopolymers from Circulating Fluidized Bed Fly Ashes

作者：Li, Xiaojiao[1]; Jin, Sai[1]; Yan, Tong[1]; Qiao, Xiuchen[2]; Yuan, Jin[1]

机构：[1] School of Environmental Science and Engineering, Taiyuan University of Technology, Jinzhong, 030600, China; [2] School of Resource and Environmental Engineering, East China University of Science and Technology, Shanghai, 200237, China

年份：2024

外文期刊名：SSRN

收录：EI(收录号：20240287246)

语种：英文

外文关键词：Calcium - Compressive strength - Curing - Fluidized bed process - Fluidized beds - Geopolymers - Inorganic polymers - Silicates - Silicon - Sodium hydroxide - Thermoelectric power plants

摘要：Circulating fluidized bed fly ash (CFB-FA) is generated from the thermal power plant as the solid waste with the different content of calcium. The reuse of CFB-FA for construction materials is the most promising method for the large-scale transformation of waste to resource. This paper examines the ratio effects of Na/Al and Si/Al on the geopolymer from the low-calcium fly ash (CFB-FA1) and high-calcium fly ash (CFB-FA2) by using the mixed Na2SiO3 and NaOH as the alkali activator. The detailed mechanistic study with XRD, FTIR, SEM, and MAS-NMR is also conducted for the role of Si, Al, and Ca in the reaction process and their mutual affective mechanism, along with the regulating mechanism for the compressive strength and setting time for geopolymer. The results indicate that the increased ratios of Na/Al and Si/Al were favorable to the reactions, and decreased the setting time for CFB-FA1 and CFB-FA2 based geopolymer. The CFB-FA1 based geopolymer had a faster setting rate than the CFB-FA2 based geopolymer did, and achieved a maximum compressive strength of 17.4 MPa after the 28d of curing with the Na/Al ratio at 0.9 and the Si/Al ratio at 2.5. The CFB-FA2 based geopolymer reached the peak compressive strength of 14.6 MPa after the 28d curing with the Na/Al ratio at 0.7 and the Si/Al ratio at 4.2. CFB-FA1 required a higher ratio of Na/Al for silicate activation and N-A-S-H formation, but CFB-FA2 needed a higher Si/Al ratio to ensure adequate active silicon for C(N)-A-S-H formation. The low calcium was favorable for the long-term strength, but the high calcium acted oppositely, primarily attributed to the decomposition of ettringite, a crucial component for maintaining the compressive strength of CFB-FA2 based geopolymers. ? 2024, The Authors. All rights reserved.