Abstract
The aim of the present study is to link the thermal expansion, spectral reflectance, and physico-mechanical aspects of different types of commercial granitic rocks with their mineralogical and chemical composition. The granitic rock types were characterized using several analyses, including petrography, chemical, mineralogical, and thermo-gravimetrical analysis using XRF, XRD, and TG/DTG/DSC techniques. The rock types were subjected to several performance tests, such as tests of their thermal expansion, spectral reflectance, and physico-mechanical properties. The results revealed that quartz, albite, and potash feldspar with minor amounts of mica (biotite/muscovite/annite) are the main mineralogical constitutes, in addition to some alteration minerals, such as kaolinite, saussorite, and prehnite. The studied granitic rocks were classified as monzogranite/syenogranite of high K-calc-alkaline and peraluminous characters and are related to late- to post-collisional settings. The thermogravimetrical analysis revealed that the overall mass loss over the whole temperature range up to 978 °C did not exceed 3% of the initial weight for all studied rocks. The results of thermal expansion revealed that the maximum change in linear thermal expansion for all rock types did not exceed 0.015% of their initial lengths at an unusual air temperature of 50 °C. The spectral analysis revealed that iron and hydroxyl ions are the main spectral absorption features that appeared in the VIS-NIR and SWIR regions, in addition to the appearance of the common and distinctive absorption peaks of the main mineral composition. Furthermore, the spectral reflectance demonstrated that the granitic rock types of low iron oxide content achieved a high reflectivity percent in the VIS-NIR and SWIR spectral regions compared with those of high iron content. As a general trend, the granitic rock types of high iron content and/or lower quartz content exhibited a high performance regarding their physical and mechanical properties, such as water absorption, apparent porosity, bulk density, compressive strength, and abrasion resistance. The results of water absorption, density, strength, and abrasion resistance of the studied granitic rocks are in the range of 0.14–0.31%, 2582–2644 kg/m3, 77.85–222.75 MPa, and 26.27–55.91 Ha, respectively, conforming to the requirements of ornamental stones according to the ASTM standard.
Highlights
Ornamental stones are natural stones of igneous, sedimentary, and metamorphic origins that can be cut into blocks and slabs and used for flooring, paving, cladding, funeral monuments, and statues due to the varieties of their colors in addition to their soundness and compactness
A significant mass loss was observed at various temperatures less than 200 ◦C for all rock types that represented the evaporation of physically and chemically bonded water that was liberated at 300 ◦C [34–37]
The results revealed that the density of the studied granitic rock types ranged from 2582 kg/m3 to 2645 kg/m3
Summary
Ornamental stones are natural stones of igneous, sedimentary, and metamorphic origins that can be cut into blocks and slabs and used for flooring, paving, cladding, funeral monuments, and statues due to the varieties of their colors in addition to their soundness and compactness. Marble and granite are the most famous types, but other stones such as quartzite, which is a metamorphic rock composed entirely of quartz, are included [1]. According to the UN international classification of exchanged goods, the granite and marble definitions are intended on commercial terms [2], where the “Marble” term comprises the whole class of carbonate rocks amenable to sawing and polishing, going beyond the limits of the mere lithologic characterization, while the “Granite” term includes the whole set of eruptive igneous rocks having a granular structure with a poly-mineral composition, irrespective of the content of quartz. The increase in world production in 2018, as reported by Montani [4], reached about 152 million tonnes. These ornamental stones were produced by twenty-seven countries with various share percentages. Due to the high distribution of natural stones such as granitic rocks and sandstones, they have been widely used as construction and building materials in historical and cultural heritage [5]
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