An improved concrete mix composition and its associated method of manufacture. A traditional concrete mix is created by mixing cementitious material with sand, aggregate, admixture chemicals and water. After the traditional mix has been thoroughly mixed, reinforcement fibers of polyvinyl alcohol are added to the mix. The reinforcement fibers chemically bond to the cementitious material, thereby chemically integrating the reinforcement fibers into the mixture. The reinforcement fibers are supplied in multiple sizes. The reinforcement fibers include both long thick fibers and short thin fibers. In this manner, the smaller reinforcement fibers can fill voids around the larger, thicker reinforcement fibers. This helps prevent the development of stress cracks in the concrete and significantly increases the strength, durability, and life expectancy of the concrete.