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Leaching behavior and environmental safety evaluation of fluorine ions from shotcrete with high-fluorine alkali-free liquid accelerator
Environmental Science and Pollution Research Pub Date : 2021-09-17 , DOI: 10.1007/s11356-021-16436-3
Renhe Yang 1 , Tingshu He 1
Affiliation  

High-fluorine alkali-free liquid accelerator (AF-hf, 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-hf 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-hf 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 Na2CO3, Na3PO4, Na2SO4, and NaNO3) 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 CaF2 peaks’ intensity was relatively weaker and Ca(OH)2 decreased obviously. Meanwhile, cement hydration products became looser and abundant of flaky C-S-H gel transformed into fibrous and chained structure.



中文翻译:

高氟无碱液体速凝剂喷射混凝土中氟离子的浸出行为及环境安全评价

高氟无碱液体速凝剂(AF -hf,F -浓度约为2.31g/L)以其成本低、稳定性好、促凝效果好等优点,仍在工程中使用。本研究的主要目的是探讨高氟无碱液体速凝剂隧道衬砌喷射混凝土中氟离子的淋溶行为及是否存在氟污染。测试了AF -hf水泥浆体和砂浆的凝结时间和力学性能。在不同的环境条件下,F -对喷射混凝土的浸出浓度进行了比较研究。此外,XRD和SEM用于分析水化产物的晶体组成和微观形貌。试验结果表明,随着AF -hf掺量的增加,水泥浆的凝结时间大大缩短,砂浆和喷射混凝土后期强度满足施工要求。此外,当浸出液类型(包括Na 2 CO 3、Na 3 PO 4、Na 2 SO 4和NaNO 3)和测试条件(粒径、浸泡温度、浸出液)不同时,F -淋溶浓度呈规律性变化,最低值大于20 mg/L,可能对地下水和土壤造成氟污染。喷射混凝土试样浸泡后,CaF 2峰强度相对变弱,Ca(OH) 2明显下降。同时,水泥水化产物变得更加疏松和丰富,片状CSH凝胶转变为纤维状和链状结构。

更新日期:2021-09-17
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