Studies on SMA Mixes with Partial Rap Replacement in Addition with Fiber

Stone Mastic/Matrix Asphalt (SMA) is a gap graded mix, consisting of high percentage of coarse aggregate, binder and fiber additives as stabilizers. High concentration of coarse aggregate maximizes the stone-on-stone contact and the interlocking in the mix which provides strength and the rich mortar provides durability. The stabilizing additives are added to the mix to prevent bitumen draindown from the mix. When compared to dense graded mixes, SMA has higher stability against permanent deformation and has the potential for long term performance and durability. In the present study an attempt has been made to study the engineering properties of the SMA Mix with Polymer Modified Bitumen (PMB) 70 bitumen and how it behaves on replacement of Reclaimed Asphalt Pavement (RAP) aggregates to virgin aggregates with addition of cellulose fiber. Comparative studies on engineering properties have been carried out on the conventional SMA Mix and the Reclaimed Asphalt Pavement (RAP) +Virgin aggregate SMA mixes with fiber. The binders, RAP and fibers are used in different proportions for preparation of mixes with the selected aggregate grading. Marshall specimens are prepared of conventional SMA mix and mixture of normal and RAP aggregates to determine the optimum bitumen content (OBC) for conventional SMA mix and SMA mix with optimized RAP and fiber, optimum RAP replacement and optimum fiber (OFC) addition. OBC, OFC and RAP replacement are determined on the various Marshall properties carried out. After this, the draindown, moisture susceptibility and rutting tests on the specimens are carried out. It was observed that 16 % RAP replacement and 0.3 % Fiber addition prove to show good results in the mix when compared to other percentages. The results showed that SMA Mix with optimized RAP and fiber, had better resistance to Engineering properties when compared to conventional SMA Mix.