Increasing bending strength and flexibility of fiber concrete matrix by laboratory method (with volume changes of all kinds of fibers).

By adding fibers as well as additional materials in concrete, the properties of concrete can be increased in terms of durability, flexibility and tensile strength. Another use of artificial fibers to improve mechanical properties and reduce shrinkage of fresh and hardened concrete, increase energy absorption and resistance to impact and explosion can be mentioned. The use of fiber concrete has many advantages compared to the use of reinforced concrete, while it also has disadvantages, such as the lack of uniform distribution of fibers in the concrete matrix and the lack of proper adhesion between polymer fibers in cement mortar. Generally, fiber concrete is used in concrete parts due to smaller cracks and less width and more durability in case of uniform distribution of fibers. Research shows that fibers significantly increase the tensile strength, plasticity of mortar and concrete. In fact, after cracking, the fibers bridge between the crack plates and cause a significant increase in toughness and energy absorption capacity. Adding artificial fibers to concrete brings advantages such as reducing plastic grip cracks, reducing plastic drop cracks, increasing impact resistance and increasing resistance to crushing. In this research, the effect of different types of fibers with different volume percentages on the compressive, bending and tensile strength of the samples at different ages compared to the control sample has been measured by laboratory method. All kinds of samples have been tested to determine the resistance against surface explosions.