Experimentally supported meso-scale Reactive Transport upscaling modeling of cementitious materials under acid attack (ExpeRTa II)

• Applicants: Professor Dr.-Ing. Frank Dehn; Professor Eduardus Koenders, Ph.D.; Neven Ukrainczyk, Ph.D.
• Subject Area: Construction Material Sciences, Chemistry, Building Physics
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 426807554

The ExpeRTa II project aims to experimentally and numerically investigate the mechanisms of mortar and concrete degradation due to acetic acid attack, emphasizing meso-scale heterogeneities that influence dissolution-diffusion characteristics. Building on the high-fidelity chemistry model developed in ExpeRTa I, this project will transition towards a meso-scale modeling approach that explicitly captures the interactions among the binder matrix, aggregate types and sizes, and the interfacial transition zone (ITZ). To achieve this, a stepwise upscaling methodology will be implemented, starting with detailed chemical interactions and progressively increasing geometric complexity in the meso-scale models. This approach enables a comprehensive examination of reaction thermodynamics and kinetics relative to transport phenomena, optimizing the composition and size distribution of concrete components. The findings from meso-scale modeling will inform homogenized inputs for engineering models, allowing for predictions of acetic acid attack on mortar and concrete under varying pH levels, exposure durations, grain-size distributions, and aggregate types. This collaborative effort between the Technical University of Darmstadt (TUDa) and the Karlsruhe Institute of Technology (KIT) will leverage the complementary strengths of both teams. The TUDa group will develop new durability models for mortar and concrete based on meso-scale reactive transport computations, which will be calibrated and validated through specialized experimental investigations of acetic acid attack conducted by the KIT team. The synergy between computational and experimental activities will enhance the accuracy of durability predictions by employing established scientific extrapolation principles based on accelerated durability testing. Special emphasis will be placed on delineating driving mechanisms through batch tests devoid of diffusion to obtain aggregate-ITZ dissolution kinetics. This will progressively transition to bulk dissolution-diffusion tests that incorporate aggregate effects, ultimately bridging the gap to realistic mortar and concrete durability.

• DFG Programme: Research Grants