# A Study on the Applicability of Waste Glass Wool and Waste Mineral Wool as Fiber Reinforcement
## 1 Introduction  
Glass wool and mineral wool fibers are materials used in inorganic insulation, and are widely used in various industrial fields such as automobiles, ships, and appliances due to their excellent sound absorption and soundproofing performance. However, these fiber materials require periodic replacement in order to maintain good performance, as their insulation and sound absorption performance decrease, respectively, over the period of use. In general, materials with significantly poor performance or a replacement cycle are sent to factories or companies where they can be reprocessed. However, the types of recycled fibers are also limited to synthetic fibers such as polyester, and a large amount of waste fibers are still processed through landfill and incineration. During this process, the incineration process discharges air pollutants such as dioxin and carbon dioxide, and in the landfill process, it is accompanied by soil pollution. Recently, as interest in resourcerecycling has increased, studies on various methods for recycling these waste fibers have been continuously conducted, and the developed technology is being used according to the use in each industry. In the civil engineering industry, concrete has advantages in various aspects such as economic and durability, and is used as the most representative structural material used in various infrastructure such as roads, buildings, dams, and railroads. However, concrete generally shows good resistance to compressive loads, but supports only up to 12% of tensile or bending loads compared to compressive loads [1]. As a result, concrete is known to be vulnerable to tensile and easily cracks due to tensile load [2; 3; 4; 5]. This low resistance of concrete to tensile and bending loads leads to brittle behavior of concrete. In addition to brittleness behavior, concrete has the disadvantages of low fracture resistance, impact resistance, and high weight [6]. Therefore, studies have been continuously conducted to overcome these problems. One of the ways developed to improve the brittle matrix of ordinary concrete is the addition of high tensile fibers to concrete as reinforcing materials [7; 8]. Fiber-reinforced concrete (FRC) was first introduced and developed in the 1960s, and it was found to have advantages such as reducing crack generation and improving long-term mechanical properties through reform of internal structure [9]. The results of these fiber reinforcement are achieved by increasing the bonding force of the cement matrix and ultimately increasing the bending capacity of concrete due to the high tensile strength and elastic modulus characteristics of the fiber [1]. After fiber was found to have an excellent effect on concrete reinforcement, various types of fibers, such as steel fibers, artificial fibers, glass fibers, and natural fibers, have been used to reinforce concrete, and research on the characteristics of the concrete mixed with the fibers has been actively conducted [10]. In addition, among the studies on various reinforcing fibers, there are research cases in which adding polypropylene fibers to concrete reduces shrinkage cracks and improves impact resistance [11]. In another study, basalt fibers that are free from environmental pollution and have high elasticity and destructive energy were added to concrete, and it was confirmed that reinforced concrete with basalt fibers suppresses initial micro crack generation and improves mechanical properties such as permeability and freezing-thawing resistance [12]. The residual strength of reinforced concrete with latex and rock wool fibers after high temperature exposure was evaluated to examine the resistance to fire that could occur depending on the use of the structure, and it was found that fiber could improve the resistance of high temperature [13]. As the insulation performance of the structure becomes more important, the amount of waste mineral wool generated during the construction and demolition process also increased.