Fabrication of hollow microspheres filled fly ash based foam geopolymers with ultra-low thermal conductivity and relative high strength

Abstract

Fabrication of lightweight inorganic thermal insulation materials with high strength and ultra-low thermal conductivity is a great challenge and is receiving growing attention worldwide. Herein, a kind of geopolymer based materials with excellent performance were successfully fabricated by simultaneous incorporation of air foams and hollow microspheres in geopolymer matrix. Mechanical strength, bulk density, and thermal conductivity, were conducted as the key performance indexes for the evaluation of prepared samples in this study. On the other hand, materials foam structures, in terms of porosity, pore diameter, and through-hole rate, were analyzed by means of “image-fitting” method in this work. Compared to pure foamed geopolymer specimen (P-series), hollow microspheres filled foam geopolymers (H-series) behaved much better performance in strength and thermal insulation properties in same density levels. The optimal performances in terms of density versus compressive strength and thermal conductivity are as follows: (300 kg/m3 vs. 2.84 MPa vs. 0.0711 W/(m·K)), (250 kg/m3 vs. 1.57 MPa vs. 0.05509 W/(m·K)), and (200 kg/m3 vs. 1.06 MPa vs. 0.05223 W/(m·K)). The incorporation of hollow microspheres lead to the much thicker foam walls of H-series sample than P-series, which is regarded as the key reason of its highly improved performance.