Adherence of Granite Plates by Mortar Adhesion: Influence of Temperature

Abstract

The objective of this work was to study the effect of temperature variation on the adherence of granite plates fixed with adhesive mortars on external flooring and exterior cladding. The rock selected was a commercially well accepted syenogranite, known as Vermelho Capao Bonito, which has excellent technological qualities and high aesthetic value. Tensile bond strength and pullout tests were performed according to the techniques proposed for ceramic materials, in view of the lack of standards for dimension stones. The test specimens were set on standard substrates with two types of mortars, one commercially manufactured by a leader company and the other developed in laboratory. After normal curing conditions (28 days at 23°C and relative humidity of 65%), the adhesion tests were performed at the following temperatures: 23oC, 30°C, 40°C, 50°C and 60°C. With increasing temperature the results indicated a decrease in adhesion values of 48% to 42%, from 2.04 to 1.13 MPa for the one developed in the laboratory and from 1.92 to 1.12 MPa for the commercial mortar. The behavior of the microstructure on the standard substrate-mortar-rock interfaces were also investigated by optical microscopy, and no signs of reaction or penetration of mortars into the rock (anchoring) were observed. With regard to the adhesion values, temperature variation was an important factor to its decrease, offering important perspectives for new experiments with other types of granites, for studies of displacements and pathologies commonly observed in external cladding made with plates of these materials.