Moisture induced length changes of tile adhesive mortars and their impact on adhesion strength

The durability of tilings is affected by the size and type of ceramic tiles. We therefore performed a study on adhesion and shrinkage mechanisms of large-sized fully vitrified tiles (30 cm × 30 cm), which were applied on a concrete substrate using two different polymer-modified tile adhesive mortars (floor and wall application). The spatial distributions of adhesion strength and mortar hydration degree, as well as the length changes of the composite specimen were determined under various curing conditions. The deformations caused by wetting and drying events are restrained by the stiff tile. Thus, stresses result especially at the edges of the tile, which may cause micro-cracking at the interface of tile and mortar resulting in a reduction of adhesion strength.