LiNO3对碱硅酸反应及其膨胀的影响

摘要

Alkali-silica reaction (ASR) processes of quartz glass soaked in NaOH solutions with or without LiNO3 at 38℃ was investigated.Ions concentrations,silicate types,phase compositions and microstructures of the reaction products at different ages were tested and analyzed by inductively coupled plasma,acidification method,X-ray diffraction and scanning electron microscope,respectively.In order to verify the long-term effectiveness of LiNO3 on mitigating ASR expansion,lengths of concrete micro-bars containing alkali-silica reactive aggregates and different LiNO3 dosages were evaluated in moist air at 38℃.Results showed that,Li+ reacted with dissolved SiO44-prior to Na+ in NaOH solution doped with LiNO3.Licontaining insoluble products,formed which covered the surface of quartz glass,resistance to further attack by OH-ions,effectively mitigated thereaction rate of ASR.For concrete micro-bars doped with LiNO3,the greater inhibition was caused with increasing molar ratio of [Li]/[Na+K].However,ASR might still proceed or cause further expansion in a longer time.Accordingly,effects that LiNO3 inhibits ASR expansion are good only in a short time,but may be invalidated after long term.%本文研究了38℃下LiNO3对石英玻璃在NaOH溶液中碱硅酸反应(ASR)的影响,采用等离子发射光谱仪(ICP)、酸化处理、X射线衍射仪(XRD)和扫描电镜(SEM)对溶液中的离子浓度、SiO2分布、固相产物的组成和微观形貌进行分析和表征.测定了长龄期在38℃湿气养护下LiNO3对沸石化珍珠岩和防城港砂岩混凝土微柱中ASR膨胀的作用效果.结果表明:掺LiNO3的碱溶液中,Li+先于Na+与溶出的SiO44-反应,生成低溶解性的含锂产物,并附着在石英玻璃表面,降低了溶液中OH-对石英玻璃的溶蚀,进而减缓了ASR的反应速率.混凝土试件中[Li]/[Na+ K]摩尔比越高,LiNO3抑制ASR膨胀效果越好;随着龄期的延长,后期掺锂试件仍存在ASR膨胀.短龄期下LiNO3抑制活性集料的ASR膨胀效果良好,长龄期作用效果减弱.