The addition of fibers to refractory castables can improve their dry-out behavior by two main mechanisms: permeability increase or mechanical reinforcement. Steel fibers present a great potential as reinforcement, because their tensile strength and modulus of elasticity are maintained even at high temperatures. In this work, the mechanical behavior and the resistance to spalling on the drying of a refractory castable containing short and long steel fibers (from 2 to 25 mm long) were evaluated, and compared to the behavior of the same castable with polyaramid (PAr) fibers. The steel fibers improved the work-of-fracture but were not efficient in avoiding damage upon drying. Their volume, about one thousand times that of the polymeric fibers, results in a lower number of fibers per unit volume of the castable. Therefore, localized stress fields in the matrix cannot have full benefit from the reinforcement provided by these fibers. The results attested the need of taking into account the magnitude of the expected stress fields in order to define the size and shape of the reinforcement particles that will lead to an optimum performance.
work-of-fracture; spalling resistance; refractory castable; steel fibers; drying
