Prediction of microstructural evolution in fly ash-modified cementitious system: A computational study

Abstract The intricate interaction between supplementary cementitious materials (SCMs) and cementitious systems profoundly influences the performance and sustainability of cementitious composites. This study explores the microstructural evolution of fly ash (FA)-modified cement paste by employing a three-dimensional cement hydration and microstructure development (CEMHYD3D) modeling package. Through comprehensive simulations, the influence of varying FA content on hydration phase evolution and pore structure within the cementitious system is revealed. As the proportion of FA within the cementitious mixtures increases, there is a substantial enhancement in the rate of hydration. Notably, the incorporation of FA introduces a significant augmentation in the hydration rate, a phenomenon with potential implications for the long-term performance of FA-modified cementitious materials. The prediction results also highlight that increasing FA substitution in cement leads to finer and more interconnected pore networks due to the pozzolanic reaction. These perceptions hold significant implications for optimizing cementitious mixes and advancing sustainable construction practices. The model-predicted results have been validated with experiments, and they are successful in predicting the microstructural evolution in FA-modified cement paste. In summary, the prediction model bridges the theoretical and practical implementation gaps by providing a thorough understanding of the microstructural evolution of FA-modified cement paste. Furthermore, it provides invaluable guidance for tailoring FA-blended cement compositions, thus promoting their enhanced performance and sustainability in the realm of cementitious materials.