Evaluation of Fly Ash and Soil Mixtures for Use in Highway Embankments

Abstract

Fly ash has a potential to be beneficially used in roadway constructions, including embankments and pavement structural layers such as base/sub-base layers, shoulders, asphalt concrete, and Portland cement concrete, to create longer lasting and sustainable infrastructure. The paper describes a laboratory study of the optimization of fly ash-soil mixture for highway embankment construction. The fly ash was collected from a utility power plant in Mississippi. Tests were conducted on soils and fly ash-soil mixtures prepared at optimum water content, including compaction, unconfined compressive strength (qu), and shear strength tests. Addition of fly ash into soil resulted in appreciable increases in the qu of the clay soil. After 14 days of curing, the qu of the samples compacted from the fly ash-soil mixtures ranged between 940 kPa and 4300 kPa, whereas the soil alone had a qu of 317 kPa. The shear strength of fly ash-soil mixture is improved due to the addition of fly ash. Friction angle increase up to 2-3 times for different fly ash-soil mixtures. A optimum mixing ratio of 60% fly ash and 40% soil is recommended to have the higher compressive strength and shear strength.