Modeling the Variation in Hydration and Strength of Blended Cement–Fly Ash Systems

Abstract

Variations in the properties of fly ashes from various sources can lead to large variations in the performance of fly ash–blended cement systems. The current study combines analytical and numerical modeling approaches to predict such variations in the hydration behavior of cement paste and compressive strength of mortars with different fly ashes. A microstructural modeling software was used to model the hydration of cement and fly ash. Fly ash parameters such as particle size distribution and reactive content were used to model the variation in fly ash hydration. The fit parameters were determined based on the experimental results obtained from isothermal calorimetry and X-ray diffraction. Heat of hydration and compressive strength results obtained from the modeling agree well with the experimental results. The results also show that modeling can be used not only to determine deterministic quantities such as heat of hydration and compressive strength but also probabilistic quantities like variation in heat of hydration and strength. Such models could be useful for safety parameters in probabilistic design. The model was further used to predict the reduction in variation due to blending of fly ashes from various sources.