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Significant quantities of coconut shell (CS), a by-product of agriculture, can be used as an artificial source of coarse aggregates. In this study, four CSs were used as coarse aggregates replacement in asphalt concrete with 0%, 10%, 20%, 30%, and 40% weight volumes. The particle sizes of the CSs used as main coarse aggregates range from 5 mm to 20 mm. The Marshall Stability test shows that the optimum bitumen content for asphalt mixtures is 5.1%. The engineering properties investigated include the volumetric, dynamic creep, indirect tensile strength, and resilient modulus. Test results show that stability decreases with increasing CS content because of high water absorption. Considering that CSs absorb bitumen, a further detailed investigation is needed to assess the performance of modified bitumen on mixture. Furthermore, the use of CSs as coarse aggregates in asphalt concrete help increase the resilient modulus, stiffness, and indirect tensile strength up to 30%. Generally, a 10% replacement of coarse aggregates with CSs is the optimal limit.

Reclaimed asphalt pavement (RAP) is a waste material generated from pavement milling activity. Rejuvenating agent is introduced to restore the properties of aging bitumen in RAP. Many studies have been investigated the performance of recycled mixture incorporating RAP with oil-based (OB) rejuvenating agent, but there is still limited research on water-based (WB) rejuvenating agent. Therefore, this study evaluated the performance of mixture incorporating RAP with OB and WB rejuvenating agents (RAP-OB and RAP-WB). OB and WB rejuvenating agents were added at recommended content of 0.70% and 52.13% by weight of bitumen, respectively. Indirect tensile strength, resilient modulus, dynamic creep and asphalt pavement analyzer (APA) tests were conducted to assess the resistance of the mixtures toward permanent deformation and fatigue cracking. It was found that the addition of OB rejuvenating agent enhanced the tensile strength, resilient and stiffness modulus by approximately 41%, 94% and 158%, respectively, relative to the control mixture. APA recorded that RAP-OB produced the lowest rut depth, followed by RAP-WB and control mixture. It indicates that RAP-OB produced the highest resistance to permanent deformation and fatigue cracking. Thus, the OB rejuvenating agent significantly improved the performance of the recycled mixture compared to the WB rejuvenating agent.