The influence of waste perlite dust on the thermal properties of silicate materials

The research concept assumed the development of silicate materials with better thermal properties than traditional sand-lime brick. This effect was to be achieved by completely or partially replacing the traditional quartz sand aggregate with microaggregate in the form of waste perlite dust [WPD]. The aim of the first stage of the research was utilization assessment of waste perlite dust as a substitute for quartz sand in mixtures with variable amounts of binder and microaggregate, with CaO/SiO2 molar ratios of 0.09 and 0.17. The resulting autoclaved silicate brick materials had favorable thermal insulation properties, similar to those of aerated concrete. Their low compressive strength necessitates the classification of these materials as thermal insulation materials, rather than structural materials. In the second stage of the research, an attempt was made to increase the strength of the composites by introducing a high-strength aggregate: quartz sand. These materials were obtained from masses with varying amounts of raw material mixtures intended for the production of lime-perlite and lime-sand materials. Both types of mixtures were prepared at a CaO/SiO2 molar ratio of 0.09. The characteristics of these materials indicate that with appropriately selected quantitative proportions of waste perlite dust to quartz sand, an autoclaved material equivalent to silicate brick can be obtained. This material, with an acceptable reduction in strength properties to a level that guarantees the preservation of structural properties [minimum 5 MPa], is characterized by a relatively low thermal conductivity coefficient λ [in the range of 0.11–0.25 W/(m∙K)].