Technical Paper ISSN 1997-1400 Int. J. Pavement Res. Technol. 5(2):75-83 Copyright @ Chinese Society of Pavement Engineering Vol.5 No.2 Mar. 2012 International Journal of Pavement Research and Technology 75 Evaluation of Foamed Warm-Mix Asphalt Incorporating Recycled Asphalt Pavement for Volumetric and Mechanical Properties Andrew M. Kasozi 1+ , Elie Y. Hajj 1 , Peter E. Sebaaly 1 , and John C. Elkins 2 ─────────────────────────────────────────────────────── Abstract: This study evaluated mixes obtained from a warm-mix asphalt (WMA) pilot project in Reno, Nevada, in the United States, in which the Ultrafoam® technology was used to produce the WMA. The evaluated mixtures included 15% recycled asphalt pavement (RAP). The study addressed the impact of curing time on volumetric properties of foamed WMA in addition to including a sample reheating study. Additionally, the field-produced WMA mixes were evaluated for moisture damage, permanent deformation and thermal cracking resistance. It was recommended that production testing for volumetric properties should be conducted within four hours of manufacturing foamed WMA at the plant. The mix should be cured in a sealed container at the expected lay-down/compaction temperature. Overall in the laboratory, the WMA mix showed no significant additional reduction in moisture damage resistance although the reverse was true for permanent deformation resistance. The WMA exhibited better thermal cracking resistance than the hot mix asphalt (HMA). A distress survey conducted after thirteen months of service showed no distresses in the WMA pavement despite its relatively lower rutting resistance observed in the laboratory. Key words: Curing; Foamed Asphalt; Hot Mix Asphalt; Moisture Damage; Performance; QC/QA; Reheating; Warm Mix. ─────────────────────────────────────────────────────── Introduction 12 The most critical part of constructing the hot mix asphalt (HMA) layer is to obtain a uniform and durable layer that can withstand the combined actions of traffic loads and environmental conditions. These desirable properties have been achieved through effective design, uniform mixing and coating during the manufacturing process and effective compaction during lay-down operations. For HMA mixtures, mixing and compacting at elevated temperatures (typically 135-175C) have been necessary to achieve these properties. This however, is at the expense of the constantly increasing asphalt binder prices and energy costs. Therefore, by reducing the energy required to produce and construct the HMA layer, significant cost savings can be realized. The past few years have seen the introduction of warm mix asphalt (WMA) technologies in efforts to achieve this. WMA is produced at temperatures 30-75C lower than those required for HMA [1], and this is directly related to savings in the energy required for production. Whatever the economical, practical, and environmental benefits of using WMA technologies, the produced WMA must be highly resistant to moisture damage, cracking, and permanent deformation in addition to being adaptable to use of recycled asphalt pavement (RAP) in the mixtures. Among the WMA technologies available today, this study evaluated the Ultrafoam® technology. It is a water-based technology that uses a foaming nozzle to inject a percentage of water (usually about 1-2% by weight of binder) into the asphalt 1 Department of Civil & Environmental Engineering, University of Nevada Reno/ MS257, Reno, Nevada 89557, USA. 2 Granite Construction Company, Nevada Region. + Corresponding Author: E-mail akasozi@gmail.com Note: Submitted May 13, 2011; Revised August 2, 2011; Accepted September 6, 2011. binder flow line. Three mixes; one lab-produced HMA and two field-produced WMA mixes were evaluated. Both field-produced WMA mixes were obtained from a pilot project that was laid down along Chism Street in Reno, Nevada in the United States. In a study of impact of curing time on mixtures’ volumetrics, one WMA mix was compacted right on delivery to the laboratory while the other was compacted later in a sample reheating study. HMA samples are often reheated for a variety of acceptance and performance tests. However since the Ultrafoam® WMA technology produces foamed asphalt, which is an irreversible component, reheated samples should not be used for volumetric acceptance [2]. Nevertheless, reheated samples can be used to evaluate the mechanical properties of WMA mixtures provided the reheating effect on WMA is similar to that for HMA. Therefore, the evaluation of impact of curing time on volumetric properties was conducted to determine a convenient cap on curing time. The cap was based on how long foamed WMA may be cured prior to compaction at WMA temperatures and still meets the requirements for volumetric properties. This was also motivated by the understanding that foamed WMA loses its foaming effect with time. The results of this evaluation would therefore be helpful in performing quality control/quality assurance on similar mixtures. All mixes were evaluated for resistance to moisture damage, permanent deformation and thermal cracking using dynamic modulus testing, repeated load triaxial (RLT) and thermal stress restrained specimens testing (TSRST), respectively. 2D planar image processing was also used in an attempt to distinguish between performances of the evaluated mixtures. Objectives The overall objectives of this study are summarized below:  Evaluate the rheological properties of asphalt binder recovered from the WMA mix.