Probabilistic Durability Analysis of Cementitious Materials under External Sulfate Attack

Abstract

A probabilistic framework is developed in this dissertation for numerical simulation of the degradation of cementitious materials under external sulfate attack. The model combines detailed approaches for four essential components of degradation: (i) diffusion of ions, (ii) chemical reactions of the cement hydration products with the diffused species, (iii) damage accumulation due to cracking, and (iv) changes in mechanical properties due to mineralogical evolution. The model is calibrated and validated using experimental results available from the literature. Sensitivity analyses are performed to identify the most influential parameters affecting the mineralogical features and the progression of damage in the structure. Uncertainty in the chemical equilibrium model is addressed through Bayesian calibration of the model parameters. The probabilistic framework accounts for various sources of uncertainty – physical variability due to inherent randomness of physical processes and parameters, and data uncertainty due to sparse or imprecise data. Various approaches for statistical representation of the uncertainties are investigated and incorporated in the durability assessment framework. The methodology for assessing the durability of the structure is implemented using nested and single-loop Monte Carlo simulation. Finally, the application of the framework is demonstrated by assessing durability of a concrete vault wall exposed to sulfate solution, incorporating uncertainty in various components of the model.