Research On The Durability Of Sewage Pipe Network Concrete Under The Action Of Freeze-thaw Cycles And Sulfate Attack

The number of the urban underground sewage networks which as an important supporting infrastructure is becoming more and more in the aspects of its construction and utilization under the background of rapid development of urbanization.As the key link of sewage collection and centralized treatment,the sewage network underground plays a very important role in urban construction,production development and urban ecological environment.In actual production and common life,the concrete of the urban underground pipeline-network will be affected by the acidity,alkalinity and sulfide under the sewage environment,which will lead to the decrease of the durability of concrete structure and the hidden danger to the safety and reliability of the underground pipeline structure.Urban sewage networks carry the transportation of domestic sewage and industrial waste water.As the erosion medium in the sewage environment will have an deteriorated effect on the concrete structure,which can cause the corrosion and the decrease of the durability of the concrete structure.Especially in cold region,concrete structures are severely deteriorated by both erosion medium attack and freeze-thaw damage,and the degradation damage to the concrete caused by the interaction between the two factors is more complicated and serious.Based on the actual subject,the paper studies the durability of the concrete of typical geological environment from urban underground pipe networks caused by the sulfate attack and freeze-thaw damage,which will have an important economic and social significance in ensuring the complete infrastructure of the underground networks and maintaining the safe operation of the city.The main research contents are as follows.1?First,the durability experiment of concrete members under the sulfate attack and dry-wet process is carried out.Based on the experiment,the paper not only analyzes the influence of different factors such as the water-binder ratio,soaking age,concentration of sulfate on the relative dynamic elasticity modulus,resistivity and mass-loss rate of concrete,etc,but also the deterioration of concrete.The results show that the water-binder ratio and soaking age have a great influence on the durability of concrete compared to other factors.2?Second,the paper chooses three types of concrete durability tests which are freeze-thaw cycle(GSaD1),sulfate attack before freeze-thaw cycle(GScD1),interaction of sulfate attack and freeze-thaw cycle(GSbD2)and then analyzing the influence of the water-binder ratio,pre-soaking age,test condition on the relative dynamic elasticity modulus,resistivity and mass-loss rate of concrete.The results show that the effect of water-binder ratio on the mass-loss rate and resistivity of3?concrete is confined to the early stage of freeze-thaw cycle,and not obvious to the later stage;but the pre-soaking age has a great effect on the frost resistance of concrete.4?Last,the paper analyzes the change rules of the appearance of concrete after freeze-thaw.The result shows that concrete degradation is serious under the combined action of sulfate attack and freeze-thaw damage(GSbD2),and part of the specimens have been completely collapsed when the freeze-thaw cycle times up to 100 times,under this condition,the frost resistance of concrete is poor.