Impacts of Curing Time and Moisture Content on Engineering Properties of Cold In-Place Recycling Mixtures Using Foamed or Emulsified Asphalt

Abstract

A cold in-place recycling (CIR) layer is typically overlaid by hot-mix asphalt (HMA) to protect it from water ingress and traffic load. Most public agencies have different curing requirements that specify the number of curing days or the maximum moisture content for the CIR layer before placing the HMA overlay. However, these criteria are not well-founded on sound engineering principles and are often challenged by contractors, especially in inclement weather conditions. This study was performed to explore technically sound ways to identify the minimum in-place CIR properties necessary to permit the placement of an HMA overlay. The primary objective of this research was to determine how curing time and moisture content affect the development of indirect tensile strength, dynamic modulus, and flow number of CIR mixtures composed of foamed asphalt (CIR-foam) or emulsified asphalt (CIR-emulsion). On the basis of the limited test results, the indirect tensile strength of CIR specimens did not increase during an early stage of curing but increased during a later stage of curing, usually when the moisture content was less than 1.5%. Given the same curing time, CIR-foam specimens exhibited more tensile strength and less moisture content than CIR-emulsion specimens. Both dynamic modulus and flow numbers increased as the curing time increased and the moisture content decreased. Given the same moisture content, CIR-foam specimens exhibited higher dynamic modulus and larger flow numbers than CIR-emulsion specimens.