Abstract
The “Rosa Arronches” granite (RA) is a natural stone quarried in the Santa Eulália region (SE Portugal) traded and exported to several countries in the world. This granite has been used as ornamental and as dimension stone. In order to assess the behaviour of this natural stone when submitted to frost and sodium chloride atmosphere, sound samples were exposed to these two aggressive environments. Petrographic and major mechanical properties (water absorption under vacuum, water absorption at atmospheric pressure, flexural strength under concentrated load and uniaxial compressive strength) were determined, before and after the artificial weathering, in order to analyse the variations that might occur in their characteristic values. The results revealed a decrease in the characteristics of all the properties evaluated. However, this decrease does not compromise its use as dimension stone, regarding the European standardization, although some chromatic changes were observed and may have an impact when used as ornamental stone. Moreover, the degradation curve obtained for the mass loss results that have been caused by salt mist decay, has revealed the development of the stone decay over time in this aggressive atmosphere. The results obtained represent a new insight into the mechanical response of this granite, to be considered especially in those regions affected by these two decay mechanisms.
Natural stone has been used by man since the early Stone Age till nowadays, both as a construction material and as a substance full of symbolism, with great plastic beauty and resistant to weathering. However, despite the common held belief that granite is not as prone to weathering as other natural stones, even granite is susceptible to it when exposed to aggressive environments, such as, for instance, soluble salts present in coastal areas, or in climatic conditions characterized by regular periods of negative temperatures and cyclically subjected to ice-melting action.
The durability of a stone element is the time period in which the properties of the element remain unchanged, in the best scenario, during its life service (I-STONE, 2006). Nevertheless, natural stone, when used as a construction material, is subjected to very different conditions from those present at its genesis, giving sometimes rise to significant changes in relation to the initial expectation when selected. The main goal of the present work is to analyse and quantify the level and development in time of the damages that might occur in the RA granite, when subjected to accelerated ageing tests to simulate the frost action and salt mist, as well as to check the maintenance of their conformity with the requirements for the use as construction material.
