Experimental assessments of methanol-based foaming agent in latex modified foamed binders and warm asphalt mixtures

Latex is one of the natural rubbers that is used to enhance the performance of asphalt pavement for the last few decades. The presence of latex, which is categorized as an elastomer, helps to improve pavement performance and durability. Conversely, higher viscosity of latex modified asphalt binder increases the production-temperatures of asphalt mixture, thus consuming higher energy during asphalt mixture’s production stage. In this study, the effectiveness of methanol as an energy-efficient foaming agent was assessed to reduce the viscosity and enhance the workability of the modified asphalt binder. The basic and rheological properties of the asphalt binders were determined through multiple laboratory tests including expansion ratio and half-life, rotational viscosity, softening point, torsional recovery, and dynamic shear rheometer. The properties of asphalt mixtures were assessed through the service characteristics, mechanical performance, and moisture resistance criteria. It was found that the presence of latex results in an approximately twofold higher expansion ratio and a lower half-life of the asphalt binder at about the same ratio. Through the rotational viscosity test, the application of methanol into asphalt binder decreased the viscosity and led to better workability, despite the addition of latex as an asphalt modifier. The application of methanol into asphalt binder improved the workability of mixture samples and lowered the compaction energy of the compaction process, which are the crucial criteria for a better mixing and compaction process. Methanol foamed asphalt mixtures with latex show much higher resistance to moisture damage and stiffness than control sample even though they were prepared at a lower temperature.