## 1 Introduction  
Concrete, as a popular construction material in the building industry, has several drawbacks, such as a low resistance capacity against tension. Reinforcing the concrete overcomes this defect. Using fibers with different materials is one of these reinforcing methods. Typically, fibers can be made using various polymers, glasses, carbons, or other naturally available materials. Concrete-containing fiber-reinforced materials, such as fiber-reinforced concrete (FRC), can offer superior properties compared to plain concrete. The mechanical characteristics of FRC can be identified based on the type and dosage of fiber and cement matrices, and specifically the geometrical and weight/volumetric percentages of the fibers and cementitious material. Moreover, the fibers' mechanical properties and the available adherence between the cement and fiber matrices can affect the structural resistance of concrete [1; 2]. The fibers reduce the possibility of cracking, and consequently increase the energy absorbed in the fracture process. Furthermore, the implementation of fiber in precast concrete has a positive effect on structures [3; 4; 5]. Several factors, such as length to equivalent diameter of the fiber's ratio, the number of fibers, and their orientation,shape, and spread within the cement matrix affect fiber's efficiency in enhancing the mechanical properties of concrete [6; 7]. In recent decades, the issue of reusing waste plastics has attracted researcher attention, considering the environmental and economic impacts of the construction industry [8; 9]. This plastic waste has the advantage of being available in large quantities at low prices [10; 11]. Polyethylene terephthalate (PET) is one of the subcategories of the large polyethylene family, produced worldwide to a great extent due to various advantages, such as a higher resistance, lighter weight, and lower production cost compared to classical plastics [12]. PET is mainly acquired from plastic container bottles that can be used to store water, beverages, and food packages [1]. To reduce water and land pollution, these plastic bottles are required to be properly recycled. Furthermore, recycling PET waste requires special consideration regarding the process of color changes and degradation impurities of the recycled material. Therefore, incremental costs of recycling are predictable [12; 13]. Moreover, the recycling rate of PET bottles is lower compared to the disposal rate, which is about 60 million bottles per hour [14; 15]. Therefore, the need for efficient and economic solutions regarding the PET bottle waste is inevitable. The use of PET bottles as continuous long strips arranged in grids to reinforce a concrete element can be considered as one of the methods of recycling PET bottles. This requirement of arranging long strips is currently an important obstacle in the discipline of construction materials. In this context, numerous research studies have been conducted. The promising outcomes on improving the mechanical properties of materials encourage further studies to offer novel methods for using these fibers to enhance the structural response of produced concrete mixtures [1; 16]. The prime objective of the presented article is to illustrate the benefits of using PET fiber as a reinforcing method in concrete. This approach is implemented by predicting the mechanical properties of concrete including PET fiber, and by adopting an artificial neural network (ANN) technique. As this machine learning approach has a reasonable accuracy, robustness, and time-saving ability, it was used as a method to estimate the mechanical properties of PFRC. It is worth noting that the main objective is the practical application of ANN in determining the required properties for the concrete industry, as well as an accurate prediction of the mechanical properties of PFRC. In this regard, the understanding about PET fiber reinforced concrete (PFRC) will be improved, and consequently will lead to increasing the incorporation of PRFC in construction practice.