Construction and Performance of Fly Ash-Stabilized Cold In-Place Recycled Asphalt Pavement in Wisconsin

Abstract

Cold in-place recycling (CIR) is a common rehabilitation practice used in Wisconsin to improve the ride quality and structural capacity of deteriorated asphalt pavements. In recent years, increased emphasis has been placed on incorporating stabilizers into the CIR materials to improve the structural capacity of the CIR base layer. This improvement can serve to increase the performance life of the completed pavement or to allow for a reduced hot-mix asphalt (HMA) surface thickness. The city of Mequon, Wisconsin, included asphalt emulsion and fly ash CIR stabilization over a portion of its CIR projects in 1997. Presented are the findings relating to the constructability of the fly ash–stabilized CIR pavement as well as performance trends for the CIR pavements based on distress and deflection testing results. CIR is a common rehabilitation practice used in Wisconsin to improve the ride quality and structural capacity of deteriorated asphalt pavements. In one type of CIR application, existing HMA layers are pulverized, graded, and compacted, then used as a base layer for a new HMA surface. The pulverization process is completed to provide uniformity of support to the HMA surface and to significantly reduce or eliminate the occurrence of reflection cracking of the HMA surface. In most CIR applications, pulverization is completed through the full thickness of the existing HMA layers, as well as through the top 25 to 50 mm of aggregate base. Penetration into unbound aggregate base materials aids in cooling of the bits on the pulverizer mandrel. After pulverization, graders typically are used to spread the materials to the desired width and shape. Compaction is achieved by using vibrating steel drum and pneumatic-tire rollers. The moisture content of the CIR materials is adjusted, as necessary, by surface spraying from a water tanker truck.

Sustainable Construction Case History: Fly Ash Stabilization of Recycled Asphalt Pavement Material

“…Thus, methods to enhance the strength and stiffness of RPM are being considered, including the addition of stabilizing agents such as asphaltic oils, cements, and self-cementing coal fly ash (a residue from coal combustion that is normally landfilled). The increased stiffness obtained by stabilization is believed to increase the service life of the rehabilitated pavement or permit a thinner HMA layer (Turner 1997;Crovetti 2000;Mallick et al 2002;Wen et al 2003;Robinson et al 2004). The use of fly ash for stabilization is particularly attractive because fly ashes traditionally have been disposed in landfills.…”

An Overview of an Electric Utility’s Combustion Products Utilization Program

“…Self cementing Class C fly ash has also been utilized for the full depth in-place reclamation of asphalt pavements, and for the stabilization of difficult soils for use as a sub-base and base material for pavements, parking lots and building slabs on grade [Crovetti 1998] [Wen et al 2004] [Wen,Tharaniyil, Ramme 2003].…”

Fly Ash - An Important Ingredient for use in Hot-Mix ASHphalt Concrete

“…The use of fly ash in bitumen materials is attractive as it improves performance and reduces costs and environmental impacts [Tapkin 2008]. The advantages of fly ash in asphalt include improved mixing, placing and compaction, stability, resistance to water damage, rutting resistance, flexibility, and resistance to freeze-thaw damage [Carpenter 1952] [Warden et al 1952 Self-cementing Class C fly ash has also been utilized for full depth in-place reclamation of asphalt pavements, and for the stabilization of difficult soils used as a sub-base and base material for pavements, parking lots, and building slabs on grade [Crovetti 1998] [Wen 2003 and2004].…”