The thermodynamic stability of sulfate ions on synthesized calcium aluminosilicate hydrate（C-A-S-H） microstructure with different Ca/Si ratios and Al/Si ratios was investigated by XRD, SEM-EDS, 29 Si and 27 Al nucle...The thermodynamic stability of sulfate ions on synthesized calcium aluminosilicate hydrate（C-A-S-H） microstructure with different Ca/Si ratios and Al/Si ratios was investigated by XRD, SEM-EDS, 29 Si and 27 Al nuclear magnetic resonance（NMR） and thermodynamic modeling. The results indicate that sulfate attack leads to both decalcification and dealumination for C-A-S-H gels, and the amount of corrosion products（gypsum and ettringite） decreased gradually with decreasing Ca/Si ratios of C-A-S-H. Sulfate ions can also promote the polymerization degree of C-A-S-H gels, improving its resistance to sulfate attack. Moreover, the 4-coordination aluminum（Al[4]） in C-A-S-H, 5-coordination aluminum（Al[5]）, 6-ccordination aluminum（Al[6]） in TAH（third aluminum hydrate） and Al[6] in monosulfate or C-A-H（calcium aluminate hydrate） can be transformed into Al[6] in ettringite by sulfate attack. Furthermore, through thermodynamic calculation, the decrease of Ca/Si ratios and increase of Al/Si ratios can improve the thermodynamic stability of C-A-S-H gels under sulfate attack, which agrees well with the experiment results.展开更多
一前言在英文版出版三十余年后,《北京的人力车夫:1920年代的市民与政治》(Rickshaw Beijing:City People and Politics in the 1920s,以下简称《北京的人力车夫》)中文版终于面世。在这本列文森奖获奖作品当中,作者史谦德(David Strand...一前言在英文版出版三十余年后,《北京的人力车夫:1920年代的市民与政治》(Rickshaw Beijing:City People and Politics in the 1920s,以下简称《北京的人力车夫》)中文版终于面世。在这本列文森奖获奖作品当中,作者史谦德(David Strand)通过充分挖掘当时的北京地方报刊等史料,再现了1920年代北京的城市生活。在此基础上,《北京的人力车夫》对五四运动结束后十年间的北京城市政治变迁进行了清晰的梳理与分析。展开更多
基金Funded by Anhui Key Laboratory of Advanced Building Materials,Anhui Jianzhu University(No.JZCL201602KF)Major State Basic Research Development Program of China(973 Program)(No.2015CB655101)+2 种基金State Key Laboratory of High Performance Civil Engineering Materials(No.2015CEM005)Natural Science Foundation of Hebei Province(No.E2016209283)Hubei Key Laboratory of Roadway Bridge and Structure Engineering(Wuhan University of Technology)(No.DQZDJJ201504)
文摘The thermodynamic stability of sulfate ions on synthesized calcium aluminosilicate hydrate（C-A-S-H） microstructure with different Ca/Si ratios and Al/Si ratios was investigated by XRD, SEM-EDS, 29 Si and 27 Al nuclear magnetic resonance（NMR） and thermodynamic modeling. The results indicate that sulfate attack leads to both decalcification and dealumination for C-A-S-H gels, and the amount of corrosion products（gypsum and ettringite） decreased gradually with decreasing Ca/Si ratios of C-A-S-H. Sulfate ions can also promote the polymerization degree of C-A-S-H gels, improving its resistance to sulfate attack. Moreover, the 4-coordination aluminum（Al[4]） in C-A-S-H, 5-coordination aluminum（Al[5]）, 6-ccordination aluminum（Al[6]） in TAH（third aluminum hydrate） and Al[6] in monosulfate or C-A-H（calcium aluminate hydrate） can be transformed into Al[6] in ettringite by sulfate attack. Furthermore, through thermodynamic calculation, the decrease of Ca/Si ratios and increase of Al/Si ratios can improve the thermodynamic stability of C-A-S-H gels under sulfate attack, which agrees well with the experiment results.
文摘一前言在英文版出版三十余年后,《北京的人力车夫:1920年代的市民与政治》(Rickshaw Beijing:City People and Politics in the 1920s,以下简称《北京的人力车夫》)中文版终于面世。在这本列文森奖获奖作品当中,作者史谦德(David Strand)通过充分挖掘当时的北京地方报刊等史料,再现了1920年代北京的城市生活。在此基础上,《北京的人力车夫》对五四运动结束后十年间的北京城市政治变迁进行了清晰的梳理与分析。
