Experimental Study On The Effect Of Carbonization And Freeze-thaw On Durability Of Concrete Bridges In Cold Regions

With the rapid development of bridge projects in China,the durability of concrete bridges has become increasingly prominent.The cold regions of China are widely distributed,and the phenomenon of cold damage to bridges is very common.In addition,as global carbon dioxide concentrations continue to rise in recent years,the carbonation damage suffered by concrete bridge structures will also become more serious.The joint action of the two will accelerate the deterioration of the durability of concrete bridges.Only a single factor was considered in traditional design methods of China.Therefore,for the cold regions,it is of great engineering significance to study the durability of the concrete bridge structure under the freeze-thaw cycle and the carbonation composite effects.Based on the study of the durability of concrete bridges in cold regions and the investigation of concrete bridge diseases in the cold regions of northern Heibei Province,the durability of concrete bridges in cold regions was investigated.In this paper,C35 ordinary concrete,C35 self-compacting concrete,and C50 self-compacting concrete are used to carry out the freeze-thaw cycle test,carbonization test,and a combination of the two,and the following conclusions are reached:(1)Under a single freeze-thaw cycle test condition,the frost resistance of C35 self-compacting concrete is better than that of ordinary concrete of the same grade.Under the same conditions,the former can withstand additional 50 cycles of freeze-thaw cycles.The higher the strength grade,the better frost resistance of self-compacting concrete,and C50 self-compacting concrete could withstand additional 25-50 freeze-thaw cycles compared with C35 ordinary concrete.This is because the smaller water-cement ratio or the incorporation of silica fume makes the concrete more compact,thus improving its frost resistance.(2)The strength grade has a great influence on the carbonation resistance of self-compacting concrete,reducing the water-binder ratio and increasing the strength grade can improve the anti-carbonization ability of the concrete.After 14 days of accelerating carbonization,the carbonization depth of C50 self-compacting concrete is about 1.1 mm,lower than that of C35 self-compacting concrete.(3)Under the single carbonization test conditions,the incorporation of silica fume causes the decline of alkali in concrete,resulting in the carbonation resistance of C35 self-compacting concrete with a 10% silica fume content inferior to ordinary concrete of the same strength grade;but the better compactness of self-compacting concrete results in less internal damage after the same number of freeze-thaw cycles,and it has a smaller promoting effect on subsequent carbonization,so that it has better resistance to carbonization under the freeze-thaw and carbonation combined effects,Research shows that the durability of self-compacting concrete is better than that of ordinary concrete.Considering the factors such as material,construction,maintenance and reinforcement,the application of self-compacting concrete has better economic benefits,social benefits and ecological benefits than ordinary concrete,so it is worth promoting.