Study On Preparation And Durability Of Marine High-Performance Concrete For Beihai Sea Crossing Bridge

The sea crossing bridge is often damaged prematurely due to the poor service environment,and it’s easy to cause major economic losses and safety accidents.In order to ensure the safe use of the sea crossing bridge within the design life,it is very important to design and study the performance of the marine concrete used in the sea crossing bridge.According to the marine environment of the Beihai Xicun Port sea crossing bridge,the raw materials of the marine concrete used are selected,and the concrete mix design is improved and optimized.At the same time,protective measures such as adding crystalline waterproof materials and graphene admixtures are used to improve the durability of marine concrete.The main research contents and conclusions are as follows:(1)Study on preparation and properties of admixture modified marine concreteMetakaolin and microbead admixtures with different structures and better pozzolanic activity were introduced into C45 and C50 concrete basing on the traditional formula.The composition and mixing ratio of admixtures were optimized and designed,the physical gradation of five admixtures was realized,and the concrete mix proportion design is improved.C45 and C50 marine concrete with 28 d compressive strength of 69.8 MPa,electric flux of 197.62 C and 28 d compressive strength of 71.5 MPa and electric flux of 179 C were prepared respectively.From the particle characteristics and chemical characteristics of mineral admixtures,it is revealed that the mechanism of improving the durability of admixtures modified marine concrete lies in the combined filling effect of admixtures and the pozzolanic activity effect.(2)Study on preparation and properties of marine concrete modified by waterproof agentCement and quartz sand were took as basic materials,sodium silicate,nano silica,hydrated lime,glutamic acid and calcium lignosulfonate were took as main raw materials of waterproof agent active substances.According to the two principles of precipitation reaction and complex precipitation reaction,the cement-based permeable crystalline waterproof agent is designed and made,and it is added into marine concrete to evaluate the improvement effect of waterproof agent on the performance of marine concrete.The experimental results show that the self-made cement-based crystalline waterproof agent can significantly improve the compressive strength,impermeability and durability of concrete samples.The waterproof mechanism of cement-based permeable crystalline waterproof agent is analyzed theoretically.(3)Study on preparation and properties of graphene modified concreteGraphene aqueous dispersion was prepared by mechanical stirring and ultrasonic dispersion,graphene nanosheets with diameter of 10 μm and thickness of 2 nm is raw materials and different kinds of surfactants is dispersants.Then graphene aqueous dispersion was added to concrete to prepare graphene modified concrete.The effects of different dispersants on the dispersion of graphene aqueous solution were evaluated.The influence and mechanism of graphene on mechanical properties and durability of concrete were studied.The results show that sodium lignosulfonate,sodium dodecylbenzene sulfonate and naphthalene water reducer have the best dispersion effect on graphene.And compared with the blank sample,the 56 d compressive strength of graphene modified concrete sample is increased by 24.04%and the electric flux is reduced by 51.97%.It is analyzed from the microstructure that the mechanism of graphene modification lies in the filling effect of graphene and its lamellar structure.