## 1 Introduction  
With the development of modern society and technology, more and more huge reinforced concrete (RC) structures have been built in China [1; 2; 3], such as Hong Kong-Zhuhai-Macau (HZM) bridge (49.968 km long, in service), Hangzhou Bay bridge (36 km long, in service) and Jiaozhou Bay bridge (36.48 km long, in service). As reinforced concrete sea-crossing bridges service in marine environments, chloride ions penetrate the concrete cover and result in the corrosion of the reinforced bars, thereby causing serious damage to the bridge structures [4; 5; 6; 7; 8]. Many problems caused by the corrosion of reinforced bars have been reported all over the world. Further, corrosion-associated maintenance and repair of reinforced concrete (RC) structures have cost multiple billions of USD per annum [9]. In some developed countries, nearly 3.5% of their gross national product (GNP) has been applied in the repair cost [10]. In order to reduce the repair cost, the durability design of RC structures,in particular, those exposed to marine environments, has been recognized as an effective means to ensure the service life of concrete structures, which has been a focus of researchers and engineers all over the world [11; 12; 13]. Service life prediction modeling has become one of the current major issues in the design of concrete structures. Using the third-moment method, [PERSON] [14] developed a time-dependent probability assessment for chloride-induced corrosion of RC structures. In order to provide corrective parameters for service life prediction, [PERSON] [15] investigated the time-dependent chloride penetration into concrete in marine environments. Considering the effect of the materials' heterogeneity when exposed to a marine tidal zone, [PERSON] [16] developed a service life prediction model. [PERSON] and [PERSON] [17] explored a probabilistic assessment of the influence of the age factor on the service life prediction using concrete with limestone cement/ground granulated blast slag (GGBS) binders. [PERSON] [18; 19] developed a service life prediction model considering freeze-thaw fatigue, taking into account fly ash and slag. [PERSON] and [PERSON] [20] developed a reliability assessment which uses the coupled effect of corrosion initiation and progression to represent the deterioration of reinforced concrete structures. Considering the action of loading, chloride ions' transport path, and the binding capacity of concrete, a series of service life prediction models were developed by [PERSON] [21]. Based on the experimental and theoretical studies on chloride transportation into concrete in marine environments, a service life prediction model was developed in DuraCrete, Life 365, and Chinese code for the durability design of concrete structures. However, [PERSON] [22] highlighted that most of the experimental studies on the corrosion of reinforced concrete structures are tested in the laboratory by means of accelerated measurement. Hence, the experimental data may not be representative compared to the \"in situ\" behavior. [PERSON] [23] also emphasized that it is undesirable to predict the long-term service life of structures on the basis of laboratory sample measurements, which is a limitation to reliable predictions. Further, the measurement results obtained by [PERSON] [24; 25] showed that there were fluctuations in the durability parameters of lining concrete, such as concrete cover, concrete strength, and chloride diffusion coefficient, in the Jiaozhou Bay subsea tunnel, and the service life was also predicted. However, there is still limited research on the service life prediction of real marine projects, such as sea-crossing bridges, offshore platforms, and subsea tunnels. The Jiaozhou Bay sea-crossing railway bridge is about 16.337 km long, and 2.006 km is in the marine area. It is the control bridge for the Qingdao-Lianyungang city railway network. At Qingdao, where the bridge is located, the relative humidity is 62-86%, which is the most suitable humidity range for carbonation.