碳化过程中C-S-H平均链长演变规律

Evolution Law of Average Chain Length of C-S-H during the Carbonation Process

为了研究碳化过程中水化硅酸钙凝胶(C-S-H)平均链长的演变规律,采用29Si NMR技术对不同水灰比、不同碳化时间的水泥净浆试样进行了分析.同时,对碳化后试样的氢氧化钙(CH)和CaCO3质量进行了热重分析.结果表明:加速碳化条件下试样的C-S-H平均链长增加,相同水灰比试样的碳化时间越长,其C-S-H平均链长越长;相同碳化时间的试样,水灰比越大,其C-S-H平均链长越长;碳化28d之后,0.53水灰比(质量比,下同)试样的C-S-H已基本完全碳化,0.35水灰比试样的C-S-H结构在一定程度上发生了变化,而0.23水灰比试样的C-S-H结构基本没有变化.另外,0.53水灰比试样的C-S-H碳化不是在CH完全反应后才开始的,碳化至7d时CH和C-S-H都发生了碳化反应且都没有完全碳化.

In order to study the evolution law of calcium silicate hydrate gel（C-S-H）average chain length during the carbonation process,the cement paste specimens prepared from different water-cement ratios（mw/mc）and carbonation ages were studied by using the nuclear magnetic resonance（NMR）spectroscopy.Meanwhile,the content of calcium hydroxide（CH）and CaCO3 was calculated by thermogravimetric experiment.The experimental results show that the C-S-H average chain length changes from low to high under the condition of accelerated carbonation.For the same mw/mcspecimen,its C-S-H average chain length increases with the extension of carbonation age.After 28 days carbonation,0.53 mw/mcspecimen＇s C-S-H is almost completely carbonated and 0.35 mw/mcspecimen＇s C-S-H structure changes to certain extent,while0.23 mw/mcspecimen changes barely.In addition,the carbonation of 0.53 mw/mcspecimen＇s C-S-H does not begin with CH completely reacted;after 7days of carbonation both CH and C-S-H undergoes carbonation reaction but the carbonation is not completed.