College of Materials Science and Engineering, Xi'an University of Architecture & Technology, Xi'an, 710055, Shaanxi, People's Republic of China.
Environ Sci Pollut Res Int. 2022 Feb;29(8):11267-11280. doi: 10.1007/s11356-021-16436-3. Epub 2021 Sep 17.
High-fluorine alkali-free liquid accelerator (AF, F concentration was about 2.31g/L) was still used in engineering because of its low cost, excellent stability, and coagulation-promoting effect. The main purpose of this study was to explore the leaching behavior of fluorine ions in shotcrete for tunnel lining with high-fluorine alkali-free liquid accelerator and whether there was fluoride pollution. The setting time and mechanical properties of cement paste and mortar with AF were tested. Under different environmental conditions, F leaching concentration from sprayed concrete was studied comparatively. Moreover, XRD and SEM were used to analyze the crystal composition and micro morphology of hydration products. The experimental results showed that with the increase of AF dosage, the setting time of cement paste was greatly shortened, and later strength of mortar and shotcrete could meet the construction requirements. In addition, when the leaching solution type (including NaCO, NaPO, NaSO, and NaNO) and testing conditions (particle size, soaking temperature, leaching solutions) were different, F leaching concentration changed regularly, and the minimum value was more than 20 mg/L, which might cause fluorine pollution to groundwater and soil. After shotcrete samples were soaked, the CaF peaks' intensity was relatively weaker and Ca(OH) decreased obviously. Meanwhile, cement hydration products became looser and abundant of flaky C-S-H gel transformed into fibrous and chained structure.
高氟无碱液体速凝剂（AF，氟浓度约为 2.31g/L）因其成本低、稳定性好、促凝效果好，仍在工程中使用。本研究主要探讨了高氟无碱液体速凝剂喷射混凝土中氟离子的浸出行为，以及是否存在氟污染。测试了含 AF 的水泥净浆和砂浆的凝结时间和力学性能。在不同的环境条件下，比较了喷射混凝土中 F 的浸出浓度。此外，还采用 XRD 和 SEM 分析了水化产物的晶体组成和微观形貌。实验结果表明，随着 AF 掺量的增加，水泥净浆的凝结时间大大缩短，砂浆和喷射混凝土的后期强度能满足施工要求。此外，当浸出溶液类型（包括 NaCO、NaPO、NaSO 和 NaNO）和测试条件（粒径、浸泡温度、浸出溶液）不同时，F 的浸出浓度呈有规律变化，最小值超过 20mg/L，可能会对地下水和土壤造成氟污染。喷射混凝土样品浸泡后，CaF 峰的强度相对较弱，Ca(OH)明显减少。同时，水泥水化产物变得更加疏松，丰富的片状 C-S-H 凝胶转化为纤维状和链式结构。
