Adsorption and Desorption Characteristics of Alkali Ions in Hydrated C_3S-nano SiO_2 Pastes  

作　　者：LU Guosen DENG Min MO Liwu 陆国森;邓敏;MO Liwu(State Key Laboratory of Materials Oriented Chemical Engineering, College of Materials Science and Engineering, Nanjing Tech University)

机构地区：[1]State Key Laboratory of Materials Oriented Chemical Engineering, College of Materials Science and Engineering, Nanjing Tech University

出　　处：《Journal of Wuhan University of Technology(Materials Science)》2018年第5期1176-1185,共10页武汉理工大学学报（材料科学英文版）

基　　金：Funded by the Program for Changjiang Scholars and Innovative Research Team in University(PCSIRT)(No.IRT1146);the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)

摘　　要：C3S pastes containing 0%,5%,10%,and 15%nano-SiO2 mixed with de-ionized water and alkali solutions were prepared.When C3S was completely hydrated,the pastes were ground into powders with a particle size less than 80μm.Adsorption and desorption characteristics of alkali ions adsorbed by C3S-nano SiO2 pastes mixed with de-ionized water immersed in alkali solutions and those in C3S-nano SiO2 pastes mixed with alkali solutions,were investigated.Meawhile,the adsorption mechanisms of alkali ions were discussed.Results showed that the contents of alkali ions adsorbed by C3S-nano SiO2 pastes mixed with de-ionized water increased with increasing substitution levels of nano-SiO2 and/or the initial alkali concentrations.In C3S-nano SiO2 pastes mixed with de-ionized water,each paste was characterized by having a fixed alkali-adsorption capacity that was essentially independent of alkali concentration.No obvious difference between the adsorption capacity of a given paste for K~＋and Na~＋was observed.Adsorption of alkali ions in the pastes is considered to be caused by surface force which is related to the BET specific surface area of the paste,and charge compensation of C-S-H gel,mainly by electrostatic interactions.In C3S-nano SiO2 pastes mixed with alkali solutions,alkali ions may enter the structure of C-S-H gel to replace a part of Ca^2＋in the interlayer.This assumption is supported by the structural characterization of C-S-H gel using ^（29）Si MAS NMR.C3S pastes containing 0%,5%,10%,and 15%nano-SiO2 mixed with de-ionized water and alkali solutions were prepared.When C3S was completely hydrated,the pastes were ground into powders with a particle size less than 80μm.Adsorption and desorption characteristics of alkali ions adsorbed by C3S-nano SiO2 pastes mixed with de-ionized water immersed in alkali solutions and those in C3S-nano SiO2 pastes mixed with alkali solutions,were investigated.Meawhile,the adsorption mechanisms of alkali ions were discussed.Results showed that the contents of alkali ions adsorbed by C3S-nano SiO2 pastes mixed with de-ionized water increased with increasing substitution levels of nano-SiO2 and/or the initial alkali concentrations.In C3S-nano SiO2 pastes mixed with de-ionized water,each paste was characterized by having a fixed alkali-adsorption capacity that was essentially independent of alkali concentration.No obvious difference between the adsorption capacity of a given paste for K~＋and Na~＋was observed.Adsorption of alkali ions in the pastes is considered to be caused by surface force which is related to the BET specific surface area of the paste,and charge compensation of C-S-H gel,mainly by electrostatic interactions.In C3S-nano SiO2 pastes mixed with alkali solutions,alkali ions may enter the structure of C-S-H gel to replace a part of Ca^2＋in the interlayer.This assumption is supported by the structural characterization of C-S-H gel using ^（29）Si MAS NMR.

关 键 词：C3S pastes nano-SiO2 adsorption desorption alkali ions 

分 类 号：TU52[建筑科学—建筑技术科学] O647.3[理学—物理化学]