Prediction of Consolidation and Shear Behavior of Fly Ash–Soil Mixtures Using Mixture Theory

Fly ash is the most generated coal combustion by-product (CCP) and causes the most substantial disposal issues. The current practice of landfilling these materials is costly and ultimately reduces available landfill space. The most desirable alternative to disposal is utilization. This alternative provides the economic benefit of the reduction or elimination of landfilling costs and supports sustainability through the reutilization of materials that would otherwise be considered wastes. Although the use of fly ash–soil mixtures as embankment fill is gaining more acceptance, traditionally there has not been wide use of these materials in other than small-scale applications. A primary reason for the limited use of fly ash–soil mixtures is that the geotechnical behavior of soil when mixed with fly ash is poorly understood. This paper presents the results of a study to develop generalized theory that can adequately predict the behavior of fly ash–soil mixtures. A mixture theory model was developed to predict engineering properties of mixtures based on the properties of the individual constituents. The developed mixture model implicitly considers the influences of physicochemical properties of the fly ash. Also, mixture theory–based consolidation and shear predictive models were developed to specifically predict geotechnical behavior of remolded fly ash–soil mixtures. Verification analyses indicate mixture theory is an effective approach to predicting consolidation and shear behavior of fly ash–soil mixtures.