Research On Durability Of High Performance Concrete Used For Bridge Structure In Severe Cold Region

In the severe cold region,durability of the bridge structure in the freeze-thaw environment is very important,directly affecting the service life of bridge,and now the bridge is still using ordinary concrete for construction,often appearing freeze-thaw damage phenomenon.Based on the research project on construction quality control technology of high performance concrete,for the road,bridge and tunnel in cold area,the paper proposed to improve the durability of concrete for bridge structure in cold area,by adding diatomite materials.The durability of concrete in freeze-thaw environment is analyzed theoretically.Based on the pore structure of concrete and the freezing law,studied the mechanism of concrete durability under freeze-thaw environment by using the theory of hydrostatic pressure and osmotic pressure.According to the damage law of concrete in freeze-thaw environment,used the damage theory as the framework of concrete durability model.Studied the main factors affecting the frost resistance of concrete,such as water cement ratio,air content,coarse aggregate and admixture,and analyzed the affecting mechanism of these factors on the frost resistance of concrete.Based on the requirements for the mix proportion of the bridge structure concrete of the actual project,considered the factors influencing the durability of concrete in freeze-thaw environment,put forward the mix proportion of the frost resistance test,and tested the frost resistance of concrete,analyzed the durability of ordinary bridge structure concrete in freezing thawing,explored the appearance of damage,quality loss and variation law of relative dynamic elastic modulus of three kinds of concrete,and then summarized the effect of dosage of air entraining agent,fly ash and ratio of water cement on the variation law.The paper studied the durability of bridge structure concrete in freezing and thawing environment,through theories and test results.Carried out the durability test of bridge structure concrete mixing with diatomite materials under freezing and thawing,and respectively doped different amounts of diatomite and calcined diatomite in the ordinary bridge structure concrete,to compare the difference of workability,strength and impermeability grade with ordinary concrete.In terms of the appearance of the concrete damage,quality loss and relative dynamic elastic modulus and so on,analyzed the frost resistance of different dosage of diatomite,calcined diatomite and ordinary concrete,and evaluated the frost resistance in ration,with the frost damage degree as an index.Analyzed the mechanism of improving frost resistance of concrete by adding diatomite materials,established the damage model of concrete in freezing and thawing,using damage theory and Weibull distribution,simulated in section equivalent graph in different acquisition time with the graphic method by using MATLAB,then compared and analyzed the section damage law of ordinary concrete and concrete added with diatomite in the same sampling time.Finally,the paper studied the durability of high performance of bridge structure concrete in severe cold area,through theories,experiments and models.