The role of tile adhesives and grout mortars to withstand daily and seasonal thermal cycles

R. Zurbriggen, Nouryon Chemicals AG, Sempach Station, Switzerland
In many climate zones, externally applied building materials are exposed to temperature changes in the order of 40°C. Especially facade or flooring composite-systems with layers of different materials undergo thermal stresses at their adhesive interfaces.
This study investigates thermally induced tensile stresses in ceramic tilings.
Daily and seasonal thermal cycles, as well as, rare but extreme events, such as a hail storm striking a warmed up terrace tiling, were (i) studied in the field and (ii) numerically modeled. Field surveys on external floors and walls delivered dimensional changes
and temperature gradients across tilings as a function of weather conditions, daytime, season and direction of exposure. Thereby it was found that the grouts accommodate most of the strain. Numerical modeling of thermal stresses clearly indicates that the grouts, especially those grouts at the periphery of the tiling field, may suffer critical loads. However, the long-term field experiment revealed that thermal stresses can be endured by a tiling, which is applied according to existing technical recommendations.
But, if additional loads (e.g. substrate shrinkage) or a weakening of the adhesion strength (e.g. by a strong skin formation) meets strong thermal stresses, then micro-cracks may form. Therefore, lowering elastic moduli of the adhesive and grouting mortars by adding polymers is an approach to reduce tensile and shear stresses at the material interfaces.