## 1 Introduction  
Presently, numerous countries throughout the world are confronting a large deficiency of landfills to discard huge amounts of various construction and demolition wastes due to huge development of infrastructure. In nations, where development is emerging quickly also increased infrastructure construction and demolition wastes, which leads to increased generation of CDW [1]. In developing nations, a significant part of CDW is causing landfills because of the lack of appropriate reusing methods, which makes social complexities and environmental issues. In 2018 it was calculated that 40 developing nations around the plant, created more than 3000 million tons of CDW [2, 3]. Using appropriate crushing techniques, CDW could be changed into recycled aggregate. Land pollution can be significantly reduced by substituting normal weight aggregates with recycled concrete aggregates. Author is study revealed successful utilization of RAC in various pavement and building structures [4]. Currently, cement production is increasing quickly to meet the request for infrastructure development. Cement production was approximately 4111.1 million tonsannually in 2018 and this demand is rapidly rising [5,6]. Presently, more than 5% of worldwide CO2 emission is because of the cement industry [7,8]. Supplementary cementitious materials can be used as partial replacement materials to meet the cement demands. SCMs such as silica fume could be used to decrease the carbon footprint of cement effectively [9]. Comparatively recycled aggregate concrete has lesser mechanical strength as compared to normal aggregate concrete NWA [10]. To enhance the RAC behavior, authors [9,11] have suggested using chemical admixtures and mineral additives (such as fly ash, chemical plasticizers, silica fume, GGBFS, etc. ), fibers (such as nylon, steel, glass, etc.) Silica fume offers great potential to be used as a mineral additive attributable to its overall accessibility at a less expensive cost. Different researchers have assessed the RAC performance with silica fume. These investigations disclose that silica fume credits more to the RAC properties when compared to normal aggregate concrete NAC. Authors in a study [9] observed that utilization of both silica fume and RCA is not favorable to concrete compressive strength but at reasonable levels for example at the same level of workability, 3% reduction was noted in compressive strength of 90 days when 100% normal aggregate concrete NAC was substituted with RAC, while 4% reduction was observed when cement was 30% substituted with silica fume. In pozzolanic reaction, silica fume may react with C-H which is a cement hydration primary product existing in RAC old paste of binder and new paste of binder, this is the reason silica fume contributes more to the RAC hardened properties. Researchers [12,13] revealed that silica fume also adds more to the durability of RAC as compared to NWA concerning chloride penetration, sorptivity, water absorption. Most of researches on fiber reinforced concrete were performed on steel fibers [12,14,15,16,17,18,19,20]. Very few researches were performed on nylon fibers [21,22,23] according to the author's knowledge. Nylon fibers are utilized in the production of different products such as carpets, rope, clothes, tires, and other durable materials. Nylon is a synthetic material. Nylon is thermoplastic silky material that can be melted and processed\" into different shapes such as \"films, fibers, or shapes\" [24]. The reason for adopting nylon fiber is that it has good hardness, resilience, and durability characteristics; and it is readily accessible in various colors, can be dyed, resistant to soil and dirt, good abrasion properties, and also accessible in different cross-sections [25]. The nylon fibers affect the environment and the discarding of these fibers in a usable way will reduce its detrimental effect on the environment [26]. Nylon is heat stable, hydrophilic, relatively inactive, and resistant to a wide variety of materials.