Researches On Carbonation And Life Prediction Of Concrete Under Freeze-thaw Environment

Concrete structures in cold regions with harsh environment will suffer fromfreeze-thaw cycle and carbon dioxide as well as other corrosive substances, and thedurability damage mechanism will be much more complex. In this paper, thecarbonation law and life prediction method for concrete structures under the freeze-thawenvironment has been studied, which will lay a theoretical foundation for the durabilitydesign and assessment of the concrete structures in cold regions.Based on the mechanism of concrete carbonation, the paper analyzed the effect ofthe freeze-thaw cycles on the concrete pores and gas diffusion. And according to therelationship between carbonation reaction rate and the concentration of carbonizablematerial established by Papadakis, the concrete porosity and pH variation under thecoupling effect of carbonation and freeze-thaw cycles is studied by numerical methods.In this paper, the completely carbonized zone and the partial carbonation zone isdefined according to the variation of pH value. Based on the results of numericalcalculation for pH value, the influencing factors of concrete carbonation are analyzedand the prediction model of concrete carbonation depth which validated by measureddata is established.The initial corrosion condition of the reinforcement under freeze-thaw environmentis proposed based on the corrosion mechanism, and the length calculation formula ofpartial carbonation zone is given. On this basis, this paper also proposes a life predictionmethod of carbonation life prediction for concrete structures under freeze-thawenvironment.