Microstructural Evolution Mechanism of C-(A)-S-H Gel in Portland Cement Pastes Affected by Sulfate Ions

作     者：张高展 ZHANG Xiaojia 丁庆军 HOU Dongshuai LIU Kaiwei 

作者机构：Advanced Building Materials Key Laboratory of Anhui Province Anhui Jianzhu University School of Materials Science and Engineering Wuhan University of Technology Department of Civil EngineeringQingdao Technological University 

出 版 物：《Journal of Wuhan University of Technology(Materials Science)》 (武汉理工大学学报（材料科学英文版）)

年 卷 期：2018年第33卷第3期

页      面：639-647页

核心收录：

学科分类：08[工学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0702[理学-物理学] 

基　　金：Funded by National Natural Science Foundation of China(Nos.51778513,51578004,51608004) the Major State Basic Research Development Program of China("973"Program)(No.2015CB655101) 

主　　题：sulfate attack portland cement paste C （A） S H gel microstructure interaction mechanism 

摘      要：The microstructural evolution of C-（A）-S-H gel in Portland cement pastes immersed in pure water and 5.0 wt% Na2SO4 solution for different ages was comparatively investigated, by means of ^（29） Si NMR spectroscopy, and SEM-EDS analysis. Additionally, molecular dynamics simulation was performed to study the aluminum coordination status and interaction of sulfate ions in C-（A）-S-H gel. The results showed significant changes in the microstructural evolution of C-（A）-S-H gel in Portland cement paste. Sulfate attack has decalcifying and dealuminizing effect on C-（A）-S-H gel which is evident from increase in mean chain length（MCL） and decrease in Ca/Si ＆ Al[4]/Si ratios of C-（A）-S-H gel. Additionally, Molecular dynamics simulation proves that Al[4] substituted in silicate chains of C-（A）-S-H gel is thermodynamically metastable, which may explain its migration from the silicate chains and transformation to Al[6], thus lowering the Al[4]/Si ratio of C-（A）-S-H gel. SO4^（2-）ions can carry the interfacial Ca^（2＋） ions into the pore solution by the diffusion-absorption-desorption process, which unravels the mechanism of sulfate attack on C-（A）-S-H gel.