Research On Durability Evaluation Of Concrete Arch Bridge Under Inland River Environment

With the rapid development of economy and people pursuing higher demands on bridges,our country's transportation industry has achieced a leap-forward development since the 20 th century.As an important part of the transport network,bridges always play a very important role in the people's livelihood and national defense construction.However,bridges are always affected by many types of factors during the service,and bridges' problems about durability become more serious gradually,such as concrete cracking and reinforcement corrosion,which will affect service life of bridges.Therefore,it becomes important to conduct researches on bridges' problems about durability.The carbonation of concrete is the main factor that leads to material degradation under inland river environment,and conducting researches on specific bridge under specific environment can guide the design of new bridges and maintenance of those bridges in service effectively.Supported by the project of the transportation science and technology in Jiangsu province,the researches on arch bridges under inland river environment were conducted.The durability tests on double curved arch bridge of Nanjing Yangtze river bridge has beed conducted,which mainly include: concrete appearance,concrete strength of the concrete components,protective layer thickness,reinforcement corrosion,carbonation depth and so on.The environment parameters of the bridge has also been studied.The results showed that the degree of reinforcement corrosion was slower with better quality of the appearance and smaller carbonation depth.The carbonation depth in the north of the river is smaller than that in the south because of good construction quality.The statistical regularity of the carbonation depth has been studied,and the result showes that they obey the normal distribution.Then,based on the results of the durability tests,the paper points out that the cracks and leakage saltpetering were the main problems.Factors affecting the bridge were summed up,and the reasons causing these problems were studied.By collecting the test data from many accelerated carbonation results,the paper compared and conducted analysis of many carbonation models.The results showed that more or less,the carbonation depths calculated by these models differed from test rusults because of the establish conditions were different.By calculating a large number of datas,Zhang's model and Niu's model were recommended to calculate carbonation depth.Based on the Zhang's model and relevant test datas,the correction of the existing model is studied.The paper researched the impacts of the fly ash on carbonation depth,and introduced the stress factor to correct the existing model.By comparing with some relevant test datas,the calculation results calculated by the correction model put forward in the paper were reasonable.The specimens derived from the double curved arch bridge of Nanjing Yangtze river bridge were used to conduct accelerated carbonation test,and the regularity of carbonation of the bridge concrete was studied.By collecting bridges datas and relevant parameters,such as service life and environment conditions,a practical model was established based on detecting data of carbonation depth and concrete compressive strength of 29 concrete bridges at service under inland river environment.The results showed that the discreteness of the carbonation coefficient was high,and a tendency revealed that the carbonation coefficient decreased with the increase of concrete compressive strength.Finally,by combining the durability maintenance measurements of the double curved arch bridge of Nanjing Yangtze river bridge,the paper discussed the commonly used durability maintenance measurements of bridges in the respects of durability design and construction of bridge,corrosion protection methods and daily maintenance.The effect of the protection coating was researched by conducting accelerated carbonation test,the results showed that this method performed well and can be used to ensuret the durability of brige concrete.