Cold In-Place Recycling (CIR) has been used widely in rehabilitating the rural highways because it improves a long-term pavement performance. 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 based on the number of curing days ormaximum moisture contents for the CIR before placing the overlay. However, these criteria are not well founded on the sound engineering principles and often challenged by contractors especially under inclement weather conditions. If the CIR layer is subjected to traffic for an unnecessary period of time before the wearing surface is placed, it would increase the riskof a premature failure in both CIR layer and overlay. The main objective of this research is to quantify the impacts of curing time and moisture content on the development of the indirect tensile strength, dynamic modulus, and flow number of CIR mixtures using foamed or emulsified asphalt during the curing process. This study was performed to explore technically sound ways to identify minimum in-place CIR properties necessary to permit placement of the HMA overlay. Based our laboratory test results, the indirecttensile 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 falls below 1.5%. For the same curing time, CIR-foam specimens exhibited the higher tensile strength and less moisture content than CIR-emulsion. For the given moisture content, the covered CIR-foam specimens exhibited the slightly higher indirect tensile strength than the coveredCIR-emulsion specimens. Dynamic modulus and flow number increased as curing time increased and moisture contents decreased. Dynamic moduli of CIR-foam specimens were higher than those of CIR-emulsion specimens. This mighthave been caused by the higher moisture content in CIR-emulsion specimensthan CIR-foam specimens for the equivalent curing time. The laboratory test results concluded that the method of curing, curing temperature and length of the curing period significantly affect the engineering properties of the CIR mixtures.
Abstract