Durability Prediction Method For Fly Ash Concrete In Natural Climate Environment

Durability degradation models (including carbonation depth prediction, chloride ionerosion rate prediction, reinforced bar corrosion rate prediction) related tomicro-environment were established by combining natural climate environment withmicro-environment response in fly ash concrete, so as to achieve durability service lifeprediction of fly ash concrete structures in natural climate environment.Microstructure of fly ash concrete cement paste at different ages was studied bymicroscopic instrument; the effect of fly ash replacement on pore structure of fly ashconcrete was researched by mercury intrusion method; the impact of fly ash replacement onpore solution pH value was studied by theoretical analysis and experimental verification.Micro-environment temperature response, micro-environment relative humidityresponse and basic physical quantities (including thermal conductivity, wet mass diffusioncoefficient and pore water saturation) of fly ash concret were tested in artificially controlledclimate environment, to analysis micro-environment response law in fly ash concrete; themodels predicting micro-environment temperature and relative humidity response in fly ashconcrete were created by combining the basic theory of mass transfer process, heat transferprocess with test results; at the same time, with the role of natural climate temperaturespectra and relative humidity spectra, the methods predicting micro-environment response infly ash concrete in natural climate environment were studied.The models predicting full carbonation length and partial carbonation length wereraised based on carbonizable substances contents andCO2diffusion rate in fly ash concrete,and verified by carbonation tests in artificially controlled climate environment; the methodpredicting carbonation depth in fly ash concrete in natural climate environment wasestablished, and verified through on-site long-term test.The effects of ocean environment(including ocean atmospheric environment, seawaterenvironment and ocean tidal environment) and fly ash replacement on chloride ion erosionrate were studied experimentally in artificially simulated ocean environment, and the modelpredicting chloride ion erosion rate in ocean atmospheric environment was set up accordingto chloride ion erosion mechanism in unsaturated concrete and test results; the methodpredicting chloride ion erosion rate in fly ash concrete in natural ocean atmosphericenvironment was established, and verified through on-site long-term test.The critical conditions of reinforced bar depassivation in carbonatinon and chloride ionerosion environment were determined experimentally in artificially controlled climate environment; reinforced bar corrosion at free expansion stage, rust expansion forcedistribution before concrete surface craking were studied theoretically based onnon-uniform reinforced bar corrosion distribution model, as well as rebar critical corrosionwhen concrete surface cracks due to rust expansion; prediction method of reinforced barcorrosion rate in fly ash concrete in natural climate environment was established accordingto reinforced bar corrosion rate time-varying mode, and verified through on-site long-termtest.Based on above research results, durability service life prediction methods of reinforcedbar depassivation in carbonation and chloride ion erosion environment, as well as rustexpansion cracking service life were studied respectively, and specific numerical exampleswere given.