The purpose of this paper is to demonstrate the influence porosity and fissuration exert on the physico-mechanical properties and durability of nine Portuguese ornamental granites with different petrographical and physical characteristics. Scanning electron microscopy (SEM) allows the type of cracks (intergranular, intragranular and transgranular) to be identified. A microfracture index was calculated based on the collected data. This index is called linear crack density (LCD) and is defined by the number of cracks per length unit. The results reveal that intragranular cracks are the most frequent and represent between 62.9% and 82.3% of all the cracks observed. A physical weathering classification system based on linear crack density values of the studied granites is presented. The voids included in these types of rocks are predominantly microfractures and correlate closely with open porosity and linear crack density. Uniaxial compressive strength and P-wave velocity (V P ) appear to decrease as linear crack density increases, albeit with low correlation coefficients. This may be due to the fact that linear crack density does not take into account possible preferential crack orientation and both properties are strongly dependent on this preferential orientation. Other textural characteristics, such as grain size and preferential orientation of certain minerals, may contribute to these low correlation coefficients. In ageing tests, the salt crystallization test demonstrated greater material loss in granites with higher linear crack densities and thermal shock testing proved that thermal cracks have a greater influence on V P in rocks with lower linear crack densities. In light of the ageing tests results, precaution is recommended when using granites with effective porosities greater than 3% as dimension stone out-of-doors in polluted continental or marine areas. D

No abstract

No abstract

No abstract

No abstract

No abstract

Water plays a fundamental role in rock weathering processes. Its penetration and movement inside rocks greatly influences the nature and intensity of damage affecting building stones. X-ray computed tomography (CT) is a useful technique for non-destructive mapping of water penetration. For the reported study, CT was used to investigate the internal structure and water penetration patterns for the Piedramuelle Stone, a Cretaceous limestone used as building material in the Oviedo Cathedral (North of Spain).X-ray CT provides good images of the internal structure of the samples: the sedimentary layering due to differences in composition and porosity is clearly seen, as well as other textural features. The movement and penetration rate of water was monitored during standard free absorption water tests. The images that were obtained show a clear difference between dry and wet zones in the interior of the sample. Water movement is related to the petrographic characteristics of the rock, mainly to layering which controls the direction of water penetration. Hounsfield Unit numbers provide a quantitative approach for assessing the penetration rate of water.

No abstract