Abstract : This research studies the possibilities of applying unsaturated polyester coating in civil engineering. Unsaturated polyester coating is used as a polymeric material on concrete or cement mortar to improve its mechanical properties such as compressive and shear strength of concrete. Due to the brittle behavior of concrete, shear strength is one of the most important factors to be considered in structural concrete design. The model used for the geometry and loading configuration was selected to generate the shear stress state. A partially merged triplex concrete cubes is one of elements form of a shear area due to the presence of the span shear subject to direct shear force. This research focuses on describing the experimental test using samples of polyester to determine its mechanical properties. Standard concrete cubes were prepared to determine the compressive strength that concrete will withstand before and after polyester coating. As well as Partially merged triplex concrete cubes used to know the direct shear stress that the model will withstand before and after the polyester coating. This paper presents the differences between all results based on the different thicknesses of polyester coating layers on the concrete surface. The uses of unsaturated polyester with different thicknesses 13μm, 25.5μm, 38μm and 60μm as a coating on the outer surface of the concrete led to a decrease in the displacement of the concrete component by 5%, 11.4%, 20.3% and 31.8% respectively compared to samples without coating. The results showed that when using unsaturated polyester with different thicknesses of 13μm, 25.5μm, 38μm and 60μm as coating on the outer surface of concrete, the shear strength of the concrete component increased by 6%, 18%, 28% and 37% respectively Compared to samples without coating.