养护温度对LiNO3抑制碱硅酸反应及其膨胀的影响

研究了38℃和60℃下石英玻璃在掺LiNO_3的Na OH溶液中碱硅酸反应过程,采用酸化处理法确定体系中SiO_2分布,采用等离子发射光谱(ICP)分析溶液中Na、Si和Li元素浓度变化,采用X射线衍射(XRD)和扫描电子显微镜(SEM)表征反应产物的组成和形貌;并检测了38℃和80℃湿气养护下掺LiNO_3的沸石化珍珠岩混凝土微柱的膨胀性。结果表明:加入LiNO_3降低了溶液中石英玻璃的溶蚀率和SiO_2的溶解度,减缓了ASR的反应速率;不同养护温度下形成的含锂产物不同,提高温度有利于Li_2SiO_3晶体的形成。对于混凝土微柱,掺锂试件早期抑制效果良好,后期仍膨胀;相同锂掺量下80℃湿气养护的试件膨胀率却明显低于38℃时的膨胀率。可见,高温养护下LiNO_3抑制ASR膨胀的效果不能很好地评价在低温下的作用效果。

Effects of Curing Temperature on Reaction and Expansion of Alkali-silica by the Use of LiNO3

To research the reaction process of quartz glass soaking in alkaline solution doped LiNO₃ or not at 38 °C and 60 °C. Silica forms content was determined quantitatively via acidification method. Inductively coupled plasma emission spectral was used to analyze ions concentration. The composition of reaction products was characterized by X-ray diffraction and scanning electron microscope. The expansion of zeolitization perlite concrete microbars with LiNO₃ was evaluated at 38°C and 80°C. Results showed that the addition of LiNO₃ decreased the dissolve rate of quartz glass and the solubility of silica, and then mitigated or delayed the reaction rate of ASR. The Li-containing solid products depended on curing temperature. Li₂SiO₃ crystal could be easily formed in higher curing temperature. For perlite concrete microbars, the effects of LiNO₃ on inhibiting ASR expansion were greater by added larger dosage of LiNO₃, but no suppression in long term. Expansion of specimens with the same lithium dosage and curing in moisture was significantly lower at 80°C than that at 38°C. Accordingly, it is unsuitable to evaluate the effectiveness of lithium inhibiting ASR by increasing curing temperature.