AASHTO PP 59-09 (2013) PDF Download

The AASHTO PP 59-09 (2013) standard provides guidance on the use of coal combustion fly ash as a fill material for construction of embankments.

The practice emphasizes that when coal combustion fly ash is processed, transported, spread, and compacted properly on a prepared grade, it can be used alone or blended with other approved aggregate materials to provide a lightweight fill material with adequate stability and load support for road or highway embankments. The standard specifies a density range of 85 to 100 pounds per cubic foot (pcf) or 1360 to 1600 kilograms per cubic meter (kg/m3) for the fly ash fill.

The practice also addresses the environmental concerns associated with the use of fly ash as fill. It outlines a conservative approach that involves the use of containment berms, cover fill material, and potentially a liner and leachate system to isolate the fly ash and any resulting effluent. However, the applicability of these measures may vary depending on the specific properties of the fly ash and the regulatory requirements in a given location.

The standard recognizes that the use of fly ash in embankments is subject to various state, county, and local environmental laws and regulations. It highlights the need to consider aspects of fly ash that are of environmental concern, such as impermeable layers and leachate collection, as required by the environmental regulations affecting the installation.