# A Study on the Applicability of Waste Glass Wool and Waste Mineral Wool as Fiber Reinforcement
## 1 Introduction
In the study to recycle waste mineral wool, it was confirmed that the mixing of waste mineral wool improves explosive behavior of mortar [14]. A study to evaluate the applicability of steel fiber-reinforced concrete (SFRC) to tunnel lining concrete, which is essential for crack control, confirmed that SFRC can be applied to tunnel lining due to its excellent residual strength after cracking and structural spalling according to shrinkage [15]. In recent research cases on fracture properties among the excellent reinforcement effects of fiber-reinforced concrete, the distribution form of steel fibers and volume fracture were applied as variables to analyze double-K fracture model (DKFM), boundary effect model (BEM), fictitious crack model (FCM), effective crack model(ECM), and numerical simulation model (NSM). It was confirmed that the distribution form of the aligned steel fibers had better fracture properties than the random dispersion [16]. In a study to characterize the fracture process of fiber-reinforced concrete, an FE model was proposed based on the mixed-mode cohesive zone model. Experiments and simulation analysis of the model consisting of the interface between fiber and concrete, the potential fracture surface, and the interface between rebar and concrete were conducted. This research mentioned the importance of concrete friction coefficients and failure modes that affect the analysis of the numerical models, and de-bonding behavior induced by diagonal cracks that can reduce fiber reinforcement effects [17]. In addition to steel and glass fibers, which are representative reinforcing fibers, there is a study to examine the effect of various typesand shapes of fibers on fiber-reinforced concrete such as PAN, PP, and PVA. Through the study, it was reviewed that the length of the fiber affects the amount of dry shrinkage reduction and the start of temperature cracks [18]. In a recent study on the reinforcement effect of carbon nanofibers, known as materials that can improve the mechanical and electrical properties of concrete, if fibers in cement are evenly dispersed by ultrasonic dispersion, carbon nanofibers show a bridging and pullout effect. It was inferred that this not only delays the cracking time of a mortar but also affects the improvement of fracture performance [19]. As a result of reviewing the characteristics of high-performance concrete mixed with carbon fiber, PP fiber, and aramide fiber according to volume fracture, it was confirmed that all three types of fibers had a positive effect on the tensile strength and bending strength of concrete. However, it was reviewed that the compressive strength decreased linearly. Mechanical properties of the hybrid fiber-reinforced concrete mixed with three types of fibers were the best. In addition, a uniaxial compression mathematical model for predicting stress and strain of HFRC was reviewed and presented [20]. Since the introduction of FRC, many research cases have been reported to mix various types of fibers into concrete. Discussions on these experimental or theoretical findings have mentioned the effect of steel fiber addition on concrete strength properties, variability in basalt fiber quality that can be problem in mixing concrete, and need to comprehensively study the hybrid fiber for concrete [21]. There are various research cases to apply coconut fibers extracted from coconuts to concrete as sustainable resources in accordance with the recent issue of sustainable construction industry promotion, and the proper addition rate of coconut fibers and reinforcement effect of concrete strength and durability were reviewed [22]. In other FRC-related studies using coconut fiber, studies were conducted to use coconut fiber as a concrete reinforcement while applying crushed door glass as an aggregate. There was no change in the amount of C-S-H gel produced through Fourier transform infra-spectroscopy analysis, and it was confirmed that adding waste glass or coconut fiber at an appropriate level was effective in improving compressive strength [23].