The effect of time on the performance of fly ash as backfill materials for embankment construction

Fly ash, the by-products of coal burning to produce electricity, has been used for many years in construction. High shear strength, low compressibility, self-hardening, and relatively lightweight of compacted fly ash makes the material to be suitable as a replacement for backfill material in embankment construction. This paper investigates the effect of time on the performance of fly ash embankment model constructed on very soft soil and hard soil foundations. The model tests were carried out using mini-centrifuge modelling of 0.5m radius. Embankment, constructed using residual soils, was used as a comparison to the fly ash embankment. The paper concludes that the use of fly ash as backfill material for embankment on hard soil can give a tremendous effect in terms of decreased settlement and increased height of prototype, safety factor and time of failure, compared to the residual soils embankment. Comparing the settlement of fly ash embankment at 28 days with residual soils embankment, it is observed that the settlement was reduced by about 6% for embankments on very soft soils and 75% for embankment on hard soils.