Abstract: To investigate the laws of natural carbonization depth and their influencing factors of existing concrete structures in the atmospheric environment of southeastern coast of China, field surveys on the ambient temperature, humidity, CO2 concentration, concrete strength, and carbonization depth of 142 highway concrete bridges located in the southeast coastal area of Fujian Province with different service ages were conducted. Based on 142 sets of data measured on-site for over six months, the relationship between the carbonization depth of concrete and various influencing factors in natural environment was explored. It is found that: the compressive strength of concrete has the greatest impact on the natural carbonization depth, followed by the age of the bridge and the water-cement ratio. The ambient relative humidity, temperature and CO2 concentration have a relatively minor impact on the natural carbonization depth due to their small variation amplitude. Four kinds of carbonization depth prediction models (including FIB model, Chinese specification model, Portuguese LNEC model, Japanese JSCE model) were tested by use of 142 sets of on-site measurement data. The findings demonstrate that the carbonization depth prediction model proposed by China’s current specification exhibits the smallest deviation from the on-site measured data. Utilizing multivariate nonlinear regression analysis method, the influence coefficients of the Chinese specification model were further modified, and a concrete carbonization depth prediction model suitable for the atmospheric environment of the southeast coast of China was proposed. The mean square error (MSE), root mean square error (RMSE) and mean absolute error (MAE) of the proposed model are 6.75, 2.60, and 1.85, respectively, which can well reflect the natural carbonization degree of concrete under the atmospheric environment of the southeast coastern of China.

Key words: bridge engineering; natural carbonization; on-site measurement; multivariate nonlinear regression; southeastern coastal atmospheric environment; durability

摘要： 为研究我国东南沿海大气环境下既有混凝土结构的自然碳化深度规律及其影响因素，对位于福建东南沿海地区142座不同在役龄期公路混凝土桥梁的环境温度、环境湿度、CO2浓度、混凝土强度及碳化深度等进行了现场调查。基于半年多现场实测的142组数据，探讨了自然环境下混凝土碳化深度与各影响因素之间的关系，发现混凝土抗压强度对自然碳化深度影响最大，桥梁龄期和水灰比次之，环境相对湿度、温度和CO2浓度由于变化幅度小，对自然碳化深度影响较小。利用现场实测的142组数据，对4种碳化深度预测模型（FIB模型、中国规范模型、葡萄牙LNEC模型、日本JSCE模型）进行了检验，结果表明：我国现行规范提出的碳化深度预测模型与现场实测数据偏差最小。基于多元非线性回归分析方法进一步修正我国规范模型的影响系数，提出了适用于我国东南沿海大气环境下的混凝土碳化深度预测模型，该模型的均方误差、均方根误差、平均绝对误差分别为6.75、2.60、1.85，能较好地反应东南沿海大气环境下混凝土的自然碳化程度。

关键词: 桥梁工程；自然碳化；现场实测；多元非线性回归；东南沿海大气环境；耐久性