To understand the long-term performance degradation of asphalt, ultraviolet (UV) photo-oxidation has been used to accelerate the aging process. Three types of asphalt binders extracted from reclaimed asphalt pavements (RAPs) and one extracted from fresh hot-mix asphalt (HMA) were aged under continuous UV exposure and UV/moisture/condensation exposure. After accelerated aging tests, the weight percentage of oxygen (WPO) in all samples were measured by using energy-dispersive X-ray (EDX) spectroscopy. The testing results indicate that the aging rates of the asphalt binder under both UV and UV/moisture/condensation are fast at the beginning and stabilize after a certain period. Experimental results were also modeled by two classic asphalt aging models, namely, the fast rate–constant rate (FRCR) and nonlinear differential dynamic (NDD) models. Although the NDD model exhibits acceptable agreement with the experimental results from both the UV aging and UV/moisture/condensation aging samples, the FRCR model fits the UV/moisture/condensation aging better and thus is recommended for future UV/moisture/condensation aging performance prediction. Additionally, although exposed under UV for the same time, the WPO in samples after UV/moisture/condensation aging were lower than those in samples after continuous UV aging. This indicates that condensation and moisture reduce the UV-induced photo-oxidative aging rate.

The purpose of this study is to evaluate and quantify the construction costs, energy costs, and environmental benefits of using cold in-place recycling (CIR) as a pavement rehabilitation technique. For this study, the costs of using CIR mixes prepared using either asphalt emulsion (CIR-E) or foamed asphalt (CIR-F) were compared with conventional 5.1-cm (2-in.) hot-mix asphalt (HMA) mill and overlays. Three different costs were considered for the production of each pavement rehabilitation technique: (1) construction, (2) energy, and (3) environmental costs. To facilitate the cost comparisons, an equivalent pavement structural analysis was conducted between each pavement rehabilitation technique using a standard design method. The results of the study showed that initial construction costs of using CIR are less than the conventional HMA mill and overlay. The energy and environmental costs were also found to be much lower for CIR mixtures compared with the HMA mill and overlay, with energy savings of up to 63%. Overall, when considering all costs, the use of CIR has lower costs compared with traditional HMA overlays. Cost savings of approximately $34,000–$39,000 were observed when using CIR with HMA overlays, with a total cost savings between 41% and 47% over traditional HMA mill and overlays. This study gives an overall procedure for assessing the economic and environmental costs of different pavement rehabilitation techniques and provides further evidence of the cost benefits associated with CIR to practitioners.