The current research focuses on the hot recycling of bituminous pavement using fresh bituminous binder and rejuvenator if necessary. Such mix consists of various amounts of the reclaimed asphalt pavement (RAP) material, called a hot recycled bituminous mixture. RAP material is expected to have considerable variability in its gradation and binder content/quality. Such variability influences the mechanical response of the hot recycled bituminous mixture. In addition, the possible interactions among the RAP binder, fresh binder and rejuvenator are unknown and complex. The type/dosage of fresh binder/ rejuvenator also influences the mechanical characterization of the material.
There exists very little understanding of the RAP variability and how it influences the hot recycling mix design and the mechanical response of the hot recycled bituminous mixture. The target binder grade in the final mixture depends on the proportion of RAP used, fresh binder and rejuvenator. The traditional way of finding the optimal proportion of RAP, fresh binder and rejuvenator is a tedious process and irrational. The primary challenge is to find the optimal proportion of the RAP binder, fresh binder and rejuvenator such that the final binder will have required rheological properties. Next, the response of the hot recycled bituminous mixture concerns and it is not clear whether it is loading rate-dependent (bituminous like behaviour) or pressure-dependent (granular like behaviour). Once estimating the proportion of RAP, fresh binder, and rejuvenator at the binder level investigation, a further challenge is to understand the mechanical behaviour of the recycled mixture. Depending on the material response, the next challenge is the choice of material parameter for the design. A rigorous investigation on the applicability of existing test methods and post-processing methods to the hot recycled bituminous mixtures is missing. The last challenge is the performance of the hot recycled bituminous mixture. The material generally exhibits more rut resistance and may fail in fatigue due to the presence of the RAP material, and obtaining the balanced performance is the most challenging task. It is not clear whether existing test protocols of rutting and fatigue characterization for conventional hot mix asphalt (HMA) can be directly used for hot recycled mixtures. Therefore, detailed research is lacking to understand the RAP variability and how variability influences the mix design and the mechanical characterization and performance.
In this seminar, I will concisely introduce “what is the need for recycling and various recycling methods”. Next, I will discuss how RAP variability influences the hot recycling mix design and “why hot recycling mix design is so challenging” with my experimental results in detail. I will also talk about the traditional way of estimating the grade/dosage of the fresh binder and rejuvenator and problems associated with the existing procedure. I will give a brief insight into the design of experiments (DoE). The methodology selected in the current research by utilizing the DoE framework to find the optimal dosage of the RAP, fresh binder and rejuvenator will be discussed in detail with my experimental results. Moreover, the methodology to understand the mechanical behaviour and choice of material parameter and performance characterization will be discussed briefly. In the next seminar, I will be talking about the mechanical response, choice of material parameter and its performance characterization in detail, which are further steps of my research work.