Thermal, ceramic and technological properties of clays used in production of roofing tiles – Principal component analysis

Abstract

This research describes a study of 11 selected samples of brick clays applied in roofing tile production, by using simultaneous thermal analysis. Additionally, the laboratory-sized samples were prepared and fired (850-950 °C) and technological properties were determined. Mathematical analysis was applied to sum all the experimental results and help discriminate the samples by their behavior during firing. The samples, very similar according to mineralogical and chemical content, as well as granulometry tests, were successfully grouped using principal component analysis (PCA). The PCA was used to explore and easily visualize the differences between samples. The PCA performed for differential thermal analysis (DTA), differential scanning calorimetry (DSC) and differential thermogravimetry (DTG) curves clearly showed that the heat flow was mainly influenced by carbonate content and its grain size, while DTG discriminated samples according to the contents of clay minerals and carbonates. In addition, dilatometry analysis revealed which samples underwent the highest densification during the firing process. The PCA analysis of fired products properties showed that the highest correlations were between water absorption with firing shrinkage and compressive strength.