ABSTRACT
Micromechanical models provide powerful tools for estimating the bulk properties of complex, heterogeneous materials like recycled aggregate concrete (RAC). This is achieved by considering their hierarchical microstructure, from the nanoscale of hydration products to the macroscale of the concrete composite. However, these models inherently rely on various input parameters, each carrying uncertainties that stem from experimental variability, natural fluctuations, or measurement inaccuracies. A rigorous quantification of these uncertainties and an assessment of their propagation through micromechanical models are essential for robust predictions of compressive strength in cementitious materials, with a particular focus on the critical role of the Interfacial Transition Zone (ITZ).
This study leverages a semi-analytical micromechanical multiscale model, which explicitly accounts for the spatially varying properties of ITZ. Unlike conventional approaches that simplify the ITZ as a uniform layer, the adopted model integrates non-uniform characteristics (thickness, porosity distribution) based on experimental insights derived from techniques like nanoindentation and SEM-EDX analyses. To quantify the inherent uncertainties associated with RAC, particularly those arising from varying recycled aggregate properties, hydration processes, and internal curing phenomena, a variance-based global sensitivity analysis is incorporated.
To overcome the significant computational expense using detailed micromechanical models, a key strategic component of this investigation involves developing an efficient surrogate model which helps to drastically reduce computational effort without significantly compromising accuracy. Furthermore, an assessment of the model uncertainty is integrated, potentially by comparing predictions based on alternative constitutive assumptions or hydration models, providing a holistic evaluation of prediction capability.
