Influence of the Ceramic Block Sorptivity on the Adherence of Rendering Mortars

Adherence is one of the main properties of rendering mortars. Pathologies related to the lack of adherence between the mortar and the ceramic block are frequently seen, especially on facades. A complex system with several variables influences adherence, where the sorptivity of the ceramic block can be highlighted. The objective of this work is to verify the influence that the sorptivity of the ceramic block has on the mortar adhesion in different combinations. Ceramic blocks burned at three temperatures with and without the presence of roughcast were used. The ceramic blocks were evaluated by immersion absorption, mechanical strength, and sorptivity tests. Three traces of mortar were used, characterized by water retention and mechanical resistance tests, in addition to adherence with the ceramic block. The adherence results between the materials indicated that the sorptivity influences the adherence with different behaviors, depending on the mortar used.