oa Use Of Finite Element Method To Predict The Cooling Curves Of Newly Paved Hma And Wma

With the development of practices towards green pavements, many agencies are shifting from the use of the conventional hot mix asphalt (HMA) towards new technologies of warm mix asphalt (WMA). The different techniques of WMA are recently developed to improve many aspects of asphalt works of which to reduce the mixing and compaction temperature, reduce the required energy for production, lessen the emissions and fumes, and extend the construction seasons. Thus, WMA is becoming commonly used in critical paving projects at cold weather or projects with short time-windows where the roadway cannot be closed from traffic for a long period of time. Based on this, it is important to know the cooling characteristics of freshly paved asphalt mats for these projects. The cooling time is a critical factor affecting the completion time of the paving operations where enough time needs to be given for the asphalt layer to cool down and gain the required stiffness to carry the traffic load. Lowering the cooling time will reduce user delays and interruption of services which decreases the accompanied financial and environmental costs. This requires the accurate estimation of the cooling time prior to construction to set more efficient rehabilitation paving operations. To achieve this, a predictive finite element model (FEM) using the ADINA (Automated Dynamic Incremental Nonlinear Analysis) package, is developed to simulate the actual cooling of newly paved asphalt layers. The model is founded on principles of thermodynamics and heat transfer to simulate the effects of conduction, convection, and radiation to predict the cooling rates of pavements. This study provides an accurate and mechanistic prediction tool for asphalt cooling that incorporates the various factors influencing the cooling rate such as layer thickness, air temperature, solar flux, wind speed, time of the day, time of the year, and properties of the paving material. The model is validated using measured data and used to assess the effect of certain critical parameters on cooling rates and impact on paving operations. This tool allows its user to simulate cooling of different types of asphalt concrete of which HMA and WMA are two options. Also, WMA has a time-dependent curing at a relatively short period of time after construction where the asphalt binder regains its original viscosity and/or a certain amount of entrapped moisture is evaporated from the WMA where insufficient curing time can lead to the deterioration of WMA at early stages. So, this tool will be used to predict the cooling time of WMA at different conditions where it will be compared with WMA curing time and thus decide whether the cooling or curing time determines the time to open to traffic for WMA projects.