Enhancing semi-insulating refractory performance with polymeric microspheres and distinct calcium aluminate cements

Energy-related expenses represent a significant concern for industries engaged in high-temperature processes. In this context, macroporous refractories have garnered notable attention for their potential use as thermal insulators, offering the prospect of energy-savings and decreased production costs across various industrial sectors. This study investigated the physico-thermo-mechanical performance of semi-insulating refractory compositions containing pre-expanded polymeric microspheres as pore-forming additives and different types of calcium aluminate cements (CACs) as binders. Various experimental tests were employed to characterize the prepared samples, including flowability, modulus of rupture, apparent porosity and density, thermal shock resistance, and thermal conductivity measurements, among others. The incorporation of .6 wt.% of polymeric microspheres into the silica-based refractory resulted in specimens with relatively moderate porosity values (34.70%), decreased density (1.51 g/cm3) and limited modulus of rupture (3.04 MPa) after firing at 815 degrees C. The alumina-rich CAC (Secar 71) emerged as the most advantageous binder choice, as the resultant specimens presented mechanical strengths of 9.21 and 4.3 MPa after drying (110 degrees C) and firing (815 degrees C), respectively, enhanced thermal shock resistance and reduced thermal conductivity (.66 W/m K at 800 degrees C). Hence, the designed formulations resulted in semi-insulating ceramic samples with a porous microstructure and favorable attributes for the fabrication of pre-molded components.