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Since the last decennium, there is an expanding interest to assess the possibility of recycling materials from the construction sector. The increasing interest to recycle materials is due to the environmental advantages such as conserving existing pristine natural resources and minimizing the overall quantity of materials destined to end up in landfills. One such material which has recently gained importance is the Reclaimed Asphalt Pavement from the demolished flexible pavement, referred to as RAP. The RAP material has been widely experimented with as a potential replacement for pristine aggregates (both Coarse and fine aggregate) in the construction of concrete pavements. Its strength and durability parameters are assessed in comparison to conventional concrete. However, is RAP a promising alternate material for pristine aggregates as it seems to be? With this question, this review paper aims to understand the feasibility and constraints of RAP usage in concrete pavements. The review attempted to refer all possible research materials available online and offline. Conference materials, technical reports, IRC code books, books and book chapters, etc were studied to understand the RAP concrete for future research. The literature reviews are based on the growth phases that the RAP material has taken in the construction industry. Furthermore, it was observed that very few efforts were taken by the researchers to improve the strength of RAP-concrete and there is a need for more attempts to enhance and enrich the potential usage of RAP in concrete pavements. This review is expected to expose the new dimensions required by academicians and researchers to effectively utilize RAP for sustainable concrete pavements in India.

Over the years stone matrix asphalt (SMA) mixtures have evolved significantly and research works have presented some promising results. This made the paving industries to increase the usage of SMA mixtures in the pavement construction. However, SMA mixtures have certain challenges or setbacks, which require comprehensive understanding. The aim of the review paper is to present some of the challenges in SMA mixtures and their mitigations measures. It is observed that several challenges (i.e., aggregate gradation, stone-on-stone contact, drain down and stabilizing agents) related to SMA mixtures are addressed by the researchers. Many agencies have suggested their own aggregate gradation based on their experience, location, climatic conditions and available manufacturing facilities, and they are working exceptionally. Stone-on-stone contact is achieved with proper aggregate gradation and failure to meet the same will reduce the performance. Drain down is major concern in the SMA mixtures since it controls overall mixture performance. Therefore, researchers shown out the most importance to curtail the same. Several researchers followed ASTM D6390 and National Cooperative Highway Research Program (NCHRP No. 424) procedure to evaluate the drain down and concluded that drain down should be less than 0.3% (by weight of mixture). Apart from that, researchers are trying different stabilizing agents to reduce the drain down. Especially, stabilizing agents such as fibers and polymers have a positive impact. Recently, suitable waste and recycle products are used as stabilizing agent to reduce drain down and environmental pollution. Out of which coconut fiber has shown some promising results, however, comprehensive research is required in this regard. On the other hand, 0.3% of cellulose fiber is working as a good stabilizing agent and can be used without conducting drain down test. The review paper provides a complete knowledge about different stabilizing agents used in SMA mixtures to minimize the drain down.