Influence of microfractures and porosity on the physico-mechanical properties and weathering of ornamental granites

Abstract

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

Durability Assessment of Clay-Bearing Soft Rocks By Using New Decay Index

“…These observations are consistent with the results of Irfan and Dearman [25]. Water absorption index has both direct and indirect effects on most of the physical properties of clay bearing rocks and is, therefore, considered the most important clay bearing rock parameter [26][27][28]. The calculated values of water absorption of the studied rocks are reported in Table 2.…”

Granite fracture index to check suitability of granite outcrops for quarrying

“…These granites are medium to coarse grained. Some of them have a porphyritic texture (Sousa et al, 2005), and others have been exploited for dimension stone (Sousa, 2000).…”

Afyonkarahisar Yöresi Tüflerinin Fiziko-Mekanik Özelliklerinin Ultrases Dalga Hızı ile İlişkisinin İncelenmesi

“…Büyük çaplı örneklerde P-dalga hızının arttığı gözlenmiştir. Bunların yanı sıra birçok yazar yine aynı şekilde kayaçların mekanik özellikleri ile P-dalga hızının yayılması arasında yakın ilişki olduğunu tespit etmiştir [11][12][13][14][15][16][17] …”