Influence of the Mineralogical and Mortar Components on the Adherence of Some “Granites”

Rock plate setting can be performed with metal inserts or by mortar adhesion. For mortar setting, the adhesion bond strength values, as a rule, should be above 1 MPa. In the present work, tests with eight types of “granite” tiles were performed to compare the adherence of five types of mortars. The rocks chosen were: Red Brasilia (syenogranite), Black Indian (migmatite), Green Labrador (charnockite), Black Sao Gabriel (hypersthene diorite), Rose Jacaranda (nebulitic migmatite syenogranite), Fantastic Blue (biotite monzogranite megaporphyritic serial gneissified), Grey Swallow (monzogranite) and Yellow Ornamental (garnet porphyroblastic gneiss), which do not have similar petrographic and sawability characteristics, thereby resulting in different initial roughness values of the plates obtained by breaking apart the blocks on the gangsaw machine, which use granulated steel as an abrasive element. The adherence of these rocks with the mortars was determined in the rough surface as well as in the polished surface by the pullout traction test, standardized for ceramics. The results showed that the mortar adhesion is related to roughness, to mineralogy and to the texture of these rocks. To verify this relationship, tensile bond strength tests were performed with the main mineral components of these rocks using single crystals with known optical orientation. Moreover, the microstructure study of the standard substrate/mortar/rock set was also performed.