You should first identify the purpose of using fiber reinforced concrete (FRC), what it is for, and what it is to improve, then how to achieve the goal.
In the attached article, it states:
" Fiber-reinforced concrete is used to overcome the difficulty of plain cement concrete which gives very low tensile strength, low ductility strength, and a little strength to cracking. Also in plain cement concrete is a chance of brittle fracture because of the propagation of micro-cracks present in the concrete that makes poor tensile strength."
However, it continues to state:
"By using conventional in first steel bars and by applying restraint techniques engineers and scientists want to improve the tensile property of concrete. Both of the above meters increase compressive strength to concrete members but do not increase the inherent tensile strength of concrete in their own way."
Next, you need to know the different types of fibers, their properties, and advantages and disadvantages.
Other than the type of fiber, one of the most important properties of fiber reinforced concrete is the "aspect ratio" of the fiber.
"The aspect ratio (ratio of its length to its diameter) (l/d) of the fibre is one of the important properties. Its value is in the range of 30 to 150. The properties and behavior of the fiber composite are also dependent upon the aspect ratio. According to research the relation between aspect ratio and ultimate strength of the composite is linear up to an aspect ratio of 75. But more than 75 of the aspect ratio relative strength and toughness is reduced. As shown in the table below."
Also, "The strength and toughness of the fiber and cement composite are depended upon the volume of the fibers used, the relation is generally linear, means a form of fibers increases the strength and toughness of the composite also increases. The drawbacks of the large value of fiber cause segregation of concrete and mortar."
The above are excerptions from the linked article, https://cementconcrete.org/concrete/fiber-reinforced-concrete-frc/2524/