## 1 Introduction  
Due to the development of the industry, the increase in the distribution volume and production of various goods has resulted in the new construction, extensions of buildings and the continued renovation of industrial facilities (collectively called distribution centers and factories) [1; 2; 3; 4]. The owners of such industrial facilities are required to complete the construction of durable buildings as soon as possible. In general, reducing the construction duration requires simplification and complexation of the main processes. Ground reinforcement in industrial facilities is one of the important processes for the initial shortening of the construction period. Depending on the site conditions, various requiredperformances--such as damp proof property, waterproofness, chemical resistance, and chloride invasion resistance--are required [5; 6; 7]. Existing industrial facilities are mainly built in fill-up or coastal areas. In most industrial facilities, ground reinforcing gypsum or the cement replacement method is applied to prevent defects such as cracking and breakage caused by deflection of the floor slabs by fixed and moving loads [8; 9]. Such alternatives do not take into account durability, such as chemical resistance and salt resistance. Therefore, the floor slab is continuously damaged [10; 11; 12; 13]. Industrial facilities need to secure alternatives that satisfy various requirements based on the necessary performance by analyzing the ground environment before construction.  
In specimens incorporating polyolefin fiber, there was a significant increase in fracture energy and ductility [14]. In particular, in the case of polyolefin fiber-reinforced concrete incorporating 10 kg/m\({}^{3}\), the tensile strength improved by almost 30%. The process of transferring applied loads from the concrete matrix to the distributed fibers after the initial cracking tended to be quite different from that of the steel fiber-incorporated specimen. The shapes of the load-deflection curves were smooth and had characteristic linear trends during the post-cracking process. Two characteristic turning points showed in the minimum load after the first softening branch and the maximum remaining load for larger deformations. In order to increase the flexural toughness and durability (chemical and salt resistance) [15; 16; 17; 18; 19; 20; 21; 22; 23; 24], it is necessary to apply the fiber reinforced concrete and the reinforcing materials to the lower surface of the concrete to evaluate the effects of the flexural performance [25; 26; 27].  
The purpose of this study was to research the effects of reinforced layers (protective materials with waterproofing ability) on the flexural toughness of concrete. In addition, the experiment program consists of checking the residual stress (\(R_{e3}\)) according to the type of fiber mixing in the same conditions. The protective materials with waterproofing ability were installed in the concrete bottom during the mixing process, and the flexural strength test was carried out. When a crack occurs in concrete from the increasing load, the flexural toughness and the residual stress (\(R_{e3}\)) were checked to evaluate the performance of the applied protective materials and reinforced different fibers.