Non-destructive Evaluation of Fired Bending Strength of Unglazed Ceramic tile Bodies Using Two Parametric Weibull Statistic Distribution Model

Increasingly trend towards producing the larger tiles have been driving force of leading companies to develop the tile industry's technologies in order to meet needs and different tastes of end-users, architectures and building engineers. Apart from technological difficulties (pressing, handling of green and dried tile, applying the engobe, glaze and different decors, firing, surface treatments, sorting), the problems resulting from the being greater tile affect more on strength of tiles in green, dried and fired states. Therefore, designing the tile body formulations with sufficient green, dried and fired strengths having the ability to traverse from press to packaging phases is very important. On the other hand, the consecutive sampling from production line (including measuring the bending strength) is vital to ensure the process validity. Breaking the 20×20 cm2 tile is not a costly test but taking the same test on a large tile (for example 3.20×1.60 m2) is meant that a large area of a valuable product is rejected. The importance of nondestructive procedures is that we can evaluate the fired strengths of produced tile bodies reliably, without rejecting the product. In this paper is presented a nondestructive method based on Weibull statistical distribution model for evaluating the fired three point bending strength of unglazed tiles. Drop in fired strengths of samples tested by this method is negligible and it is possible to return those in production process for sorting and packaging.