# Effect of SIRRCCs with Varying Steel Fiber Volume Fractions on Flexural Behavior
## 1 Introduction  
Conventional concrete is a brittle material with a low tensile strength as a result of compressive strength and tensile strain. To prevent the brittle fracturing of concrete materials while improving tensile behavior and energy dissipation capacity, high-performance fiber-reinforced cementitious composites (HPRCCs) has been actively researched [(1; 2; 3; 4; 5; 6)]. In general, adding steel fibers to concrete can delay the generation of initial cracks and restrain the progress of cracks. Moreover, a large increase in strength and toughness can be expected [(1; 2; 3; 7; 8)].  
Furthermore, owing to the recent rapid development of construction technology, structures are becoming larger, higher, and longer, and the functions of structures are becoming more diversified and complicated, resulting in an increasing trend of unexpected loads such as explosions and fires [(1; 2; 3; 9; 10)]. These structures are usually located in high-traffic and densely populated areas, which can cause difficulties in recovering the structure if the structure is damaged due to an explosion or an extreme load such as a shock or impact, and there is a risk of chain damage [(11; 12; 1)]. Ultra-high-performance concrete (UHPC) is a high-tech material that follows new technological rules regarding composition, production, and mechanical behavior, as well as design and the construction of structures [(13)]. The high packing density, especially of fine aggregates in the binder matrix, reduces the water demand of fresh mixes andincreases compressive strength. Further, the brittleness of UHPC concrete permits a high compressive strength and improved durability [13]. Conventional concrete specimens fail catastrophically as a result of a single crack, and separated into two pieces. On the contrary, fiber-reinforced concrete specimens, even with low fiber volume fractions retain their post-cracking ability to carry out loads [14]. In recent years, different HPFRCCs have been developed to improve the mechanical performance, resilience and durability of concrete structures [15; 16]. HPFRCCs have been expected to improve on the drawbacks of concrete and improve on impact resistance [17]. Most recently, river sand and high-volume supplementary cementitious materials such as fly ash and/or ground-granulated blast slag have been used to reduce material costs and carbon footprints [15; 16].  
The typical defensive design used to respond to unexpected loads in existing structures has been to increase the thickness of concrete walls [11; 12], but high-performance materials such as HPFRCCs provide other advantages that include improving the utilization of structures and the efficient reinforcement of work. However, while HPFRCCs have a high compressive strength, their tensile strength and strain capacity are slightly lower than their compressive strength performance. This may be the biggest issue for the limited fiber volume fraction of HPFCCs [1; 11; 12]. The increasing threat of global terrorism as well as general safety concerns has given rise to a need for reinforced concrete structures that can withstand sudden dynamic loads like impacts and blasts. The energy-absorbing capacity of a material plays an important role in developing protective structures, and fiber-reinforced concrete is becoming popular due to its greater impact-resistance properties [18].  
This study develops a slurry-infiltrated fiber-reinforced cementitious composite (SIFRCCs) that can maximize flexural tensile strength and energy absorption by maximizing the amount of steel fibers needed to increase resistance to very short working loads such as explosions or shocks. SIFRCCs utilize a high-performance slurry to make high fiber-volume fractions possible. Unlike conventional HPFRCCs or fiber-reinforced concrete, SIFRCCs place the fibers first, then fill the high-performance slurry between the steel fibers. This study also analyzes flexural behavior characteristics in respect to steel fiber volume fractions, considering fiber volume fraction of 4%, 5% and 6%.