Multi-scale simulation analysis of sulfate transport in concrete structures coupled with multiple factors
A multiscale simulation and analysis method for sulfate transport in concrete structures coupled with multiple factors was proposed.Based on Fick's second law and chemical reaction kinetics,a multi-factor coupled sulfate transport model was proposed,which simultaneously includes the ion concentration gradient effect,chemical reaction consumption considering ion activity,calcium dissolution,ettringite expansion and temperature.Firstly,the concrete structure was modeled as a homogeneous material,the sulfate transport law of homogeneous concrete structure was investigated from the macroscopic scale,and the transport model was verified in comparison with the experimental data.Subsequently,employing the Monte Carlo method and Fuller's grading curve,a stochastic aggregate concrete model was established to authentically reflect the randomness and heterogeneity of concrete.This model allows for the investigation of the characteristics of sulfate transport in concrete structures influenced by the random sizes and positions of aggregates at a mesoscopic scale.The results show that the mass fraction of sulfate ions in concrete significantly increases with greater external sulfate ion mass fractions,higher temperatures,and higher calcium ion concentrations in the pore solution.The shift in solid-liquid equilibrium due to calcium leaching has a more pronounced impact on the transport of sulfate ions than changes in the porosity of the concrete caused by leaching.Moreover,the sulfate transport model at the mesoscopic scale effectively demonstrates the randomness and unevenness in the distribution of sulfate ions caused by the randomness of aggregate sizes and positions.The presence of aggregates results in a higher accumulation of sulfate ions on the sides near the erosion boundary,while the sides of aggregates away from the erosion boundary have lower mass fraction of sulfate ions.
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