Effect of polymeric fiber reinforcement on thermal gradients and physical properties in refractory castables

This study evaluates how adding 0.2 wt% EMSIL-DRY™, a commercial low-melting burn-out polymeric multifilament fiber used to enhance permeability during dry-out, affects the pore-network evolution, thermal-gradient development, and ultrasonic integrity of ultra-low cement castables (ULCCs). Cubic specimens (6″ and 11″) were heat-treated at 350°C, 560°C, and 730°C to assess porosity evolution, thermal gradients, and integrity. Mercury intrusion porosimetry showed increased total porosity, especially intraparticle, with fiber addition. Interparticle porosity rose at intermediate temperatures due to fiber burnout but decreased at 730°C. A secondary pore network (0.1–2 μm) improved vapor release and reduced internal thermal gradients by up to 23.75% at 560°C. Despite a decrease in P-wave velocity (4120 m/s to 3880 m/s), structural integrity was preserved. Larger specimens exhibited more pronounced effects, highlighting scale-dependent behavior. Overall, fiber addition improved thermal dissipation by enhancing pore connectivity and permeability while preserving ultrasonic integrity, offering practical insights for optimizing refractory castables in high-temperature industrial environments.