Toward the Service-Life Design of Cementitious Materials In Freeze-Thaw Environments: Novel Models, Specifications, and Evaluation Methods
Smith, Scott Howard
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In order to design the service-life of cementitious materials in freeze-thaw environments, advancements in the engineering sciences, analytics, on-site evaluations techniques, and durability specifications must be connected in a coherent manner. Using the fact that there exists a critical saturation above which freezing induces damage, questions and hypotheses are developed to advance the fundamental understanding of how cementitious materials become progressively water-saturated and the underlying physics and material parameters that govern long-term freeze-thaw durability. Two models, termed single- and multi-void dissolution kinetics (SVDK and MVDK), are derived to build upon current knowledge of how single and polydisperse air void systems become water-filled. A novel limit state function is also developed to evaluate the hypothesis that the universal value of critical saturation (~85%) for cementitious materials can be explained by the evolution in mean distance between non-water-filled air voids due to saturation.The limit state model is then probabilistically evaluated to determine the relative influence of common design parameters and the ability of international design specifications to ensure long-term freeze-thaw performance. Recognizing that the derived models are dependent upon common material parameters, a data-science approach is used to form a full process-structure-property linkage for hydrating cement pastes - allowing for the prediction of diffusivity as a function of water-to-cement ratio and total hydration time. Lastly, discrepancies in freeze-thaw design documents established by American Concrete Institute committees are critically reviewed and compared to a database of long-term freeze-thaw tests on concrete. Evidence-based recommendations are made to unify and modernize current requirements to ensure the freeze-thaw durability of concrete in the 21st century.