Laboratory-scale Method to Assess the Durability of Rendering Mortar and Concrete Adhesion Systems

The adhesion failure of the interface between concrete and rendering mortars often leads to the degradation of the reinforced concrete building envelopes. Although several methods to improve the adhesion properties between concrete and rendering mortar have been proposed, there is no system to evaluate the effectiveness of these methods from the perspective of durability. To this end, this study proposed an experimental method to evaluate the durability of rendering mortar and concrete adhesion systems at the laboratory level. In this technique, a cyclic thermal load is applied to a part of the rendering mortar surface to accelerate the degradation; this part represents an external wall subjected to solar radiation. Subsequently, appropriate constraints are applied to the loaded part of the mortar to reproduce the actual degradation mechanism. Numerical simulation and experimental results support the effectiveness of the proposed accelerated degradation method. Considering the rate of decrease in the bond strength as a criterion to evaluate the durability, the influence of several known factors on the durability can be explicitly ranked. The durability assessment method can facilitate the comparison of novel solutions during the development stage.