Thermal insulation and X-ray attenuation properties of fired clay-perlite composites

In this work, the expanded perlite (EP) was used as an additive in local Hang Dong (HDC) and San Kham Phang (SPC) clays from Chiang Mai province, Thailand, for wall tile manufacturing and its influence on various properties were investigated. All samples were fabricated by drying and sintering the mixtures at 1100 °C for 8 h. Fired bulk density, shrinkage, water absorption and modulus of rupture were measured. With increasing perlite content, the density showed a decreasing trend (2.16–1.62 g/cm 3 for HDC clay and 2.13 to 1.37 g/cm 3 for SPC clay) with the corresponding reduction in the modulus of rupture. Both types of clays showed higher water absorbability when more perlite was added, indicating the hygroscopic properties of porous perlite particles. Phase and chemical composition indicated the uniform distribution of pea-pod-like perlite structure in clay matrix with strong interfacial bonding due to chemical reaction between perlite additive and clay matrix. X-ray attenuation coefficient was found to decrease in correspondence with the decreasing trend in density values. The thermal conductivity of perlite-added Hang Dong clay exhibited at least 10 times reduction compared to pure clay, suggesting the excellent insulation behavior. The HDC with 100 and 200 cm 3 perlite showed good performance in terms of rupture strength, water absorbability, X-ray attenuation with additional insulation properties. Based on this perlite-clay composite study, the sample could be further optimized for its X-ray shielding application by infiltration with elemental or alloy particles.