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.