## 4 Conclusions  
This study presented an analytical technique for predicting the service life of cracked concrete structures under carbonation and climate change.  
First, by using a kinetic hydration model, the degree of hydration of cement was calculated. The hydration related properties such as the amount of carbonatable substances and porosity were calculated through the degree of hydration and concrete mixing proportions. The calculated results from the hydration model were used as input parameters for the carbonation model. The carbonation depth for sound concrete was evaluated by considering the concrete material properties and the environmental conditions. By using a difference scheme of carbonation model, the effects of climate change on carbonation such as increased CO\({}_{2}\) concentration and environmental temperature were considered.  
Second, the influence of cracks on equivalent CO\({}_{2}\) diffusivity and carbonation depth was analyzed. With the decrease of water-to-cement ratios and increase of crack width, the ratio of CO\({}_{2}\) diffusivity between cracked concrete and sound concrete increased. High strength concrete with a lower water-to-cement ratio is more vulnerable to cracks than low strength concrete with a higher water-to cement ratio. With the increase of water-to-cement ratio and crack width, the carbonation depth of concrete increased.  
Third, different climate change scenarios (such as RCP 2.6, RCP 4.5, RCP 8.5 and upper 90% confidence interval of RCP 8.5) and time slices (such as 2000 and 2050) were considered for case studies. By utilizing the Monte Carlo method, the influences of various climate change scenarios on the service life loss of concrete structures were highlighted. For cases involving the RCP 8.5, RCP 4.5 and RCP 2.6 climate change scenarios, concrete structures with a time slice 2000 and a 50-year service life, after considering climate change had their service life reduced by 16%, 14.5% and 11%, respectively. With a time slice in 2000, as the climate change scenario changed from RCP 8.5 to RCP 8.5 upper 90% confidence interval, service life loss slightly increased from 16% to 16.5%. While with a time slice 2050, as the climate change scenario changed from RCP 8.5 to RCP 8.5 upper 90% confidence interval, service life loss slightly increased from 24% to 25%. The service life loss may have more uncertainty in the near future than in the present. In the case of the RCP 8.5 climate change scenario, service life loss increased from 16% to 24% for concrete structures with a 50-year service life when the time slice changed from 2000 to 2050. This showed that with increases in former service life, the reduction ratio regarding former service life also increased after considering climate change. Climate change presented a more significant influence on the service life of more durable concrete.  
In addition, the outcome of the current study cannot be generalized for all concrete structures. When the concrete material properties, environmental conditions and crack conditions are different from those shown in the current study, the service life loss may be different.  
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (No. 2015R1A5A1037548) and a NRF grant (NRF-2017R1C1B1010076).  
The authors declare no conflict of interest.