Zheng Jun, Zeng Gang, Zhou Hui, Cai Guanghua
China Railway 11th Bureau Group Co., Ltd., Wuhan 430061, China.
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China.
Materials (Basel). 2022 Jul 29;15(15):5238. doi: 10.3390/ma15155238.
The corrosive water environment has a decisive influence on the durability of a diversion tunnel lining. In this paper, the effects of carbonation on cement-based materials in water-immersion and saturated-humidity environments were studied by increasing the CO concentration. The results show that under conditions of water-immersion and saturated humidity, the color of the non-carbonation region is dark, while the carbonation region is gray, and the color boundary is obvious. However, in an atmospheric environment, there is no zone with a dark color and the color boundary is not obvious. In a saturated-humidity environment, the carbonation depth increases over time and changes greatly, and its value is about 16.71 mm at 200 days. While in a water-immersion environment, the carbonation depth varies little with time and the value is only 2.31 mm. The carbonation depths of cement mortar samples in different environments generally follow a linear relationship with the square root of time. The carbonation coefficient in a saturated-humidity environment is more than nine times that in the water-immersion environment. In a water-immersion environment, the carbonation causes a large loss of calcium in cement-based materials, and their Ca/Si ratio obviously decreases. The calcium silicon ratio (Ca/Si) of cement-based materials in a water-immersion environment is 0.11, which is much less than 1.51 in a water-saturated environment and 1.49 in an atmospheric environment. In a saturated-humidity environment, the carbonation only reduces the pH of the pore solution in the carbonation region, and the structural stability of cement-based materials is not degraded. The number of pores of all radii after carbonation in a water-immersion environment exceeds that in a saturated-humidity environment, and the total pore volume and average pore radius in a water-immersion environment are also larger than in a saturated-humidity environment, so the water-immersion environment accelerates the development and expansion of pores. The research results can provide some theoretical and technical support for the design, construction, and safe operation of diversion tunnel linings.
腐蚀性水环境对引水隧洞衬砌的耐久性具有决定性影响。本文通过提高CO浓度，研究了碳化在水浸和饱和湿度环境下对水泥基材料的影响。结果表明，在水浸和饱和湿度条件下，未碳化区域颜色较深，而碳化区域为灰色，颜色边界明显。然而，在大气环境中，不存在深色区域，颜色边界不明显。在饱和湿度环境中，碳化深度随时间增加且变化较大，200天时其值约为16.71mm。而在水浸环境中，碳化深度随时间变化较小，值仅为2.31mm。不同环境下水泥砂浆样品的碳化深度一般与时间的平方根呈线性关系。饱和湿度环境下的碳化系数是水浸环境下的九倍多。在水浸环境中，碳化导致水泥基材料中钙大量流失，其Ca/Si比明显降低。水浸环境中水泥基材料的钙硅比（Ca/Si）为0.11，远低于水饱和环境中的1.51和大气环境中的1.49。在饱和湿度环境中，碳化仅降低了碳化区域孔隙溶液的pH值，水泥基材料的结构稳定性未退化。水浸环境中碳化后所有半径的孔隙数量均超过饱和湿度环境，水浸环境中的总孔隙体积和平均孔隙半径也大于饱和湿度环境，因此水浸环境加速了孔隙的发展和扩张。研究结果可为引水隧洞衬砌的设计、施工及安全运行提供一定的理论和技术支持。
