Evolution of the mechanical strength of industrially dried ceramic tiles during storage

Industrially fast-dried ceramic tiles were used to determine the variation of dried tile mechanical strength with storage time in a moisture-free container. Dried tile mechanical strength rose with storage time under these conditions. Under the most favourable conditions. dry mechanical strength increased by up to 60% of the initial value. The reason for the rise in mechanical strength is attributed to the relaxation of stresses that develop during rapid industrial drying. A model was derived making the assumption that on exiting the dryer. the tile acts as a Maxwell linear viscoelastic system. The relation was determined between tile moisture content and mechanical strength, which was shown to be independent of whether tile moisture content was the result of drying wet tiles, or dried tile adsorption of ambient humidity. This relation and the stress relaxation model were used to derive a model that describes the evolution of dried tile mechanical strength during subsequent storage in ambient air very well. (C) 2003 Elsevier Science Ltd. All rights reserved.