Physical-mechanical properties of a granite used in the UNESCO World Heritage of the north of Portugal after high-temperature pretreatment

Abstract

This paper studies the evolution of physical and mechanical properties of 46 cubic samples of a granite widely used in the UNESCO World Heritage of the north of Portugal pre-treated at different temperatures (between 105 and 700 °C) and cooled under different conditions (i.e., aircooled and water-cooled). The results showed that specific gravity and mineralogy did not exhibit significant changes after the thermal pre-treatment. In contrast, density, porosity, ultrasonic properties, uniaxial compressive strength and elastic modulus showed important variations, mainly at temperatures higher than 500 ºC. The SEM analyses clearly show an increase in the density of cracks, as well as in the width and length of the cracks from 500 ºC. Furthermore, it was observed an amplification of the damage in those samples cooled by water immersion. These results are of relevance for the evaluation of the integrity level of buildings built using this rock after a fire.