The focus of this study is to critically review the physiochemical and engineering properties of the fly ash and its applications in various fields. The utilization of fly ash has become a widespread area, but the amount of utilization is still a serious issue. It has many beneficial qualities (such as pozzolanic property, fineness, spherical shape, lightweight, etc.), which enhance its properties and make it suitable for its utilization as a new construction material. For the bulk utilization of fly ash, it should be employed in the areas independent of any other parameters. So that, the disposal problem can be reduced significantly. The knowledge of its physiochemical characteristic helps in the judgment of appropriate fly ash for any particular type of work. Fly ash can be utilized in other areas such as asphalt concrete, geopolymer concrete, ground improvement, agricultural sector, roller compacted concrete, brick, etc. that will reduce the existing ashes, and also the disposal problem can be solved appreciably. The implementation of fly ash must be avoided below the natural ground water level and below 4 °C temperature conditions.

The present study mainly focuses on the evaluation of dynamic properties of silt-rich fly ash from Renukoot, India, under large and small strain conditions using cyclic triaxial and bender element test, respectively. The influence of confining pressure, loading frequency, relative compaction, and shear strain amplitude on dynamic properties of fly ash under small strain and large strain condition has also been studied. The dynamic shear modulus (G) found experimentally from cyclic triaxial test shows the decay in a nonlinear manner with the increment of loading frequency and cyclic shear strain. The increment in dynamic shear modulus of fly ash was noticed with the increment of relative compaction and confining pressure. Similarly, the increase in small strain shear modulus (G max ) was observed with the increment of confining pressure, relative compaction, and frequency of the waveform. The decrease in damping ratio was observed with an increase in shear strain, especially for higher strain side (i.e., γ > 0.5%) but vice versa is not true for lower strain side (γ < 0.5%). Therefore, irrespective of the soil type, there exists a threshold strain beyond which damping ratio decreases with an increase in shear strain. All the parameters except loading frequency have a prominent impact on G and G max is sensitive to the entire considered factors. Finally, empirical correlations were developed between normalized shear modulus ratio (G/G max ) and damping ratio (D) of silt-rich fly ash with cyclic shear strain (γ) at different confining pressure, relative compaction, and loading frequency. The developed correlations can be helpful in calculating the dynamic properties of Renukoot fly ash at different strain levels. The developed correlations will also assist in the safe design of structures with fly ash as geo-material in the seismic-prone regions.

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