Recycling part or all of the pavement materials in an existing road during reconstruction is an attractive
construction alternative. When reconstructing roads surfaced with hot mix asphalt (HMA), the HMA, underlying
base, and a portion of the existing subgrade often are pulverized to form a new base material referred to as recycled
pavement material (RPM). Compacted RPM is overlain with a new HMA layer to create a reconstructed or
rehabilitated pavement. This process is often referred to as full-depth reclamation. Similarly, when an unpaved
road with a gravel surface is upgraded to a paved road, the existing road surface gravel (RSG) is blended and
compacted to form a new base layer that is overlain with an HMA surface. Recycling pavement and road materials
in this manner is both cost effective and environmentally friendly. However, recycled base materials may contain
asphalt binder, fines, and/or other deleterious materials that can adversely affect strength and stiffness. To address
this issue, chemical stabilizing agents can be blended with RPM or RSG. Use of industrial material resources for
stabilization (e.g., cementitious coal fly ash) is particularly attractive in the context of sustainability. The purpose
of this study was to develop a practical method to design local roadways using stabilized RPM or SRSG as the base
layer and Class C fly ash as the stabilizing agent. The design method was developed in the context of the “gravel
equivalency” (GE) design methodology employed for local roads in Minnesota.
Benson, Craig; Edil, Tuncer; Bloom, Paul; Ebrahimi, Ali; Kootstra, Brian; Li, Lin.
Use of Fly Ash for Reconstruction of Bituminous Roads.
Minnesota Department of Transportation.
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