Application of pyrophyllite in building and refractory ceramic materials

Abstract

Phyllosilicate mineral pyrophyllite possesses talc’s characteristic softness and crystalline structure, but it also exhibits high refractoriness. Pyrophyllite is predominantly being used in the ceramic materials (tiles, porcelain) as a replacement of quartz, clay or feldspar. Due to its thermal transformation into mullite, pyrophyllite is stable at elevated temperatures. Its ion-exchanging properties are crucial for stabilization of the toxic elements in building materials. In this study pyrophyllite is used as a mineral additive for two types of construction products: traditional ceramic materials and refractory mortars. The experimental samples were prepared using 50 % of pyrophyllite and 50 % of refractory clay, ceramic clay, and carbonate brick clay, respectively. The samples were formed into discs or tiles using the compression method. The following characteristics have been investigated: resistance to firing (900 – 1300°C), carbonate content, plasticity coefficient, dimensional changes after drying at 105°C and upon firing, water absorption, and mechanical strength. Refractory samples were prepared using andalusite as aggregate, ordinary Portland cement and/or high aluminate cement as binder, and pyrophyllite as an additive (10 %, 20 %, and 30 %). Compressive and flexural strength both at normal and at elevated temperature were tested on the samples, along with the refractoriness. The changes that pyrophyllite addition brings to the material’s mineral composition, microstructure, as well as to bonding/sintering mechanisms were monitored using instrumental techniques (DTA, TGA, XRD). The aim of the investigation was to prove potential suitability of pyrophyllite as efficient and sustainable resource for the production of ceramic and refractory materials.