Mix-ratio optimization for air-tight tunnel concrete Xiaoliang Huang, Yong Zhang, Dingge Hou, Cheng Xue, Guang Li, Bo Li, Zhendi Wang and Bin Li E3S Web Conf., 358 (2022) 02042 Published online: 27 October 2022 DOI: 10.1051/e3sconf/202235802042