硝酸侵蚀喷射混凝土NO_3~-扩散研究
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摘要
以一般大气环境喷射混凝土衬砌长大公路隧道为背景,以汽车尾气中氮氧化物与水的主要产物硝酸为侵蚀介质,开展喷射混凝土硝酸浸泡试验,研究喷射混凝土衬砌结构耐久性能退化规律.采用固液萃取法和电化学分析法,测试侵蚀喷射混凝土pH值和NO_3~-含量,分析浸泡龄期、硝酸溶液pH值、钢纤维和混凝土成型方式等因素对喷射混凝土pH值和NO_3~-扩散的影响,研究硝酸侵蚀喷射混凝土物理力学性能劣化机理.结果表明,硝酸侵蚀喷射混凝土pH值高于模筑混凝土,而NO_3~-含量较低,喷射混凝土硝酸侵蚀耐久性优于模筑混凝土.侵蚀溶液pH值不大于2时,钢纤维喷射混凝土pH值和NO_3~-含量分别大于和小于普通喷射混凝土.综合分析钢纤维喷射混凝土物理力学性能、pH值及NO_3~-含量,钢纤维对提升低pH值硝酸侵蚀喷射混凝土耐久性能具有明显的作用.
Durability degradation of shotcrete-lining-long-highway-tunnel in general atmospheric environment which is corroded nitrogen dioxide in automobile exhaust was analyzed. Shotcrete was immersed in nitric acid solution with pH of 1.0, 2.0 and 3.0. The pH values and nitrate ion diffusion of concrete specimens which were immersed in nitric acid solution were measured by using solid-liquid extraction method and electrochemical method. In the meantime, the influence factors of pH values and nitrate ion diffusion on shotcrete was discussed in terms of immersion aging, pH value of nitric acid solution, steel fiber and formation way, respectively. Result shows that the pH value of normal shotcrete was higher than that of normal concrete, while nitrate ion content was lower. Therefore, the durability of shotcrete exposed to nitric acid was better than that of normal concrete. As nitric acid solution pH value was less than 2, the pH value and nitrate ion content of steel fiber reinforced shotcrete were higher and lower than those of normal shotcrete, respectively. It was indicated that steel fiber can obviously improve the shotcrete durability exposed to low pH value nitric acid.
Durability degradation of shotcrete-lining-long-highway-tunnel in general atmospheric environment which is corroded nitrogen dioxide in automobile exhaust was analyzed. Shotcrete was immersed in nitric acid solution with pH of 1.0, 2.0 and 3.0. The pH values and nitrate ion diffusion of concrete specimens which were immersed in nitric acid solution were measured by using solid-liquid extraction method and electrochemical method. In the meantime, the influence factors of pH values and nitrate ion diffusion on shotcrete was discussed in terms of immersion aging, pH value of nitric acid solution, steel fiber and formation way, respectively. Result shows that the pH value of normal shotcrete was higher than that of normal concrete, while nitrate ion content was lower. Therefore, the durability of shotcrete exposed to nitric acid was better than that of normal concrete. As nitric acid solution pH value was less than 2, the pH value and nitrate ion content of steel fiber reinforced shotcrete were higher and lower than those of normal shotcrete, respectively. It was indicated that steel fiber can obviously improve the shotcrete durability exposed to low pH value nitric acid.
引文
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[11] YUAN H, DANGLA P, CHATELLIER P, et al. Degradation modelling of concrete submitted to sulfuric acid attack[J]. Cement & Concrete Research, 2013, 53(2):267-277.
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[13] 尹蓉蓉, 朱合华. 酸侵蚀对公路隧道安全性影响的模拟计算[J]. 扬州大学学报(自然科学版), 2011, 14(3):70-73.YIN Rongrong, ZHU Hehua. Safety influenced by acid medium to deep highway tunnel[J]. Journal of Yangzhou University (Natural Science Edition), 2011, 14(3):70-73.
[14] 中国国家标准化管理委员会. 喷射混凝土用速凝剂:GB/T 35159-2017[S]. 北京: 中国标准出版社, 2017.Standardization administration of the PRC. Flash setting admixtures for shotcrete:GB/T 35159-2017[S]. Beijing: China Standard Press, 2017.
[2] GARY B. Hemphill. Practical tunnel construction [M]. Hoboken: Jone Wiley & Sons, 2013.
[3] LEUNG C K Y, LAI R, LEE A Y F. Properties of wet-mixed fiber reinforced shotcrete and fiber reinforced concrete with similar composition [J]. Cement and Concrete Research, 2005, 35:788-795.
[4] 《中国公路学报》编辑部. 中国隧道工程学术研究综述·2015[J]. 中国公路学报, 2015, 28(5):1-65.Editorial department of China journal of highway and transport. Review on China’s tunnel engineering research: 2015[J]. China Journal of Highway and Transport, 2015, 28(5):1-65.
[5] TOMAS F, GARSHOL K F, TOMISAWA N. Sprayed concrete for final lining: ITA working group report [J] Tunneling and Underground Space Technology, 2001,16: 295-309
[6] 王家滨, 牛荻涛, 张永利. 喷射混凝土力学性能、渗透性及耐久性试验研究[J]. 土木工程学报, 2016, 49(5):96-109.WANG Jiabin, NIU Ditao, ZHANG Yongli. Investigation of mechanical, permeability and durability performance of shotcrete with and without steel fiber[J]. China Civil Engineering Journal, 2016, 49(5): 96-109
[7] WANG Jiabin, NIU Ditao, DING Sha, et al. Microstructure, permeability and mechanical properties of accelerated shotcrete at different curing age[J]. Construction & Building Materials, 2015, 78: 203-216.
[8] 雷宏刚, 吴涛, 吕建国. 在硝酸盐作用下混凝土结构的腐蚀与防护[J]. 建筑结构, 2007, 37(S1): 8-11.LEI Honggang, WU Tao, Lü Jianguo. Preservation and protection of concrete corroded by nitrate[J]. Construction Structure, 2007, 37(S1): 8-11.
[9] GLASS G K, BUENFELD N R. Differential acid neutralization analysis[J]. Cement & Concrete Research, 1999, 29(10):1681-1684.
[10] YUAN H, DANGLA P, CHATELLIER P, et al. Degradation modeling of concrete submitted to biogenic acid attack[J]. Cement & Concrete Research, 2015, 70(2):29-38.
[11] YUAN H, DANGLA P, CHATELLIER P, et al. Degradation modelling of concrete submitted to sulfuric acid attack[J]. Cement & Concrete Research, 2013, 53(2):267-277.
[12] FAN Y F, HU Z Q, ZHANG Y Z, et al. Deterioration of compressive property of concrete under simulated acid rain environment[J]. Construction & Building Materials, 2010, 24(10):1975-1983.
[13] 尹蓉蓉, 朱合华. 酸侵蚀对公路隧道安全性影响的模拟计算[J]. 扬州大学学报(自然科学版), 2011, 14(3):70-73.YIN Rongrong, ZHU Hehua. Safety influenced by acid medium to deep highway tunnel[J]. Journal of Yangzhou University (Natural Science Edition), 2011, 14(3):70-73.
[14] 中国国家标准化管理委员会. 喷射混凝土用速凝剂:GB/T 35159-2017[S]. 北京: 中国标准出版社, 2017.Standardization administration of the PRC. Flash setting admixtures for shotcrete:GB/T 35159-2017[S]. Beijing: China Standard Press, 2017.