Description

AASHTO PP 59 – Standard Practice for Coal Combustion Fly Ash for Embankments

This practice covers the use of coal combustion fly ash (typically but not limited to non-selfhardeningash) as a fill material for the construction of embankments.

When properly processed, hauled, spread, and compacted on a prepared grade to appropriatedensity standards, coal combustion fly ash used alone, or blended with traditional soil aggregate orother approved aggregate materials, can be expected to provide a lighter-than-normal weight fillmaterial (85 to 100 pcf, 1360 to 1600 kg/m³) with adequate stability and load support for use asroad or highway embankment.

The technique described in this practice uses containment berms, cover fill material, andsometimes a liner and leachate system to isolate the fly ash and any resulting effluent. This is aconservative approach to the environmental issues raised by the use of fly ash as fill, and may notbe required for all fly ashes or for all regulatory requirements.

This practice recognizes that since fly ash is a by-product of the burning of coal in electricityandsteam-generating facilities, various state, county, and local environmental laws andregulations apply if fly ash is used as an alternative embankment material. Aspects of fly ashthat are of environmental concern are identified. Therefore, this standard discusses elementssuch as impermeable layers and leachate collection, as they may be required according to theenvironmental regulations affecting the proposed installation.