Effect of mineralogical variations on physico-mechanical and thermal properties of granitic rocks

Abstract

The present study aims to explain the geochemical and mineralogical details of the granitic rock types in Gabal EL-Faliq area, South Eastern Desert of Egypt, in relation to geotechnical engineering and their suitability as dimension stones. The objective of the current research was achieved through two steps; the first step involved geological studies such as the petrographic, geochemical, and mineralogical investigations. The second and applicable step involved the geotechnical assessment of the studied rocks by measuring their engineering properties such as physical, mechanical, and thermal expansion properties. The petrographic investigation revealed that the studied granitic rocks are divided into two main classes: (1) gneissose granites (Biotite–Perthite) of medium to fine-grained size and (2) alkali-feldspar granites of coarse to medium-grained size. Mineralogically, the studied rocks are composed mainly of albite, orthoclase and quartz in varying proportions, along with some accessory minerals such as apatite and rutile in addition to some minor quantities of iron-group minerals such as hematite and ilmenite. The engineering properties showed that the maximum water absorption and apparent porosity values are 0.34% and 0.77%, respectively, while the minimum bulk density is 2604.03 kg/m3. The compressive strength ranges from 999.68 to 2469.10 kg/cm2, while the abrasion resistance varies from 29.67 to 54.64 Ha. The increase in albite content led to an increase in water absorption while a decrease in bulk density and compressive strength. The increase in the grain size led to an increase in apparent porosity and a decrease in mechanical properties. A Great variation in the expansion coefficient as well as the length change, occurs under changes in temperature, mineral composition, and physical properties. The increase in heating temperatures caused an insignificant increase in linear thermal expansion with a maximum value of 0.0385% at 100 °C. These results indicated the suitability of the studied granites as dimension stones for use in indoor and outdoor decorative purposes (cladding/paving) under variable temperature conditions.

Reducing Water Absorption and Improving Flexural Strength of Aluminosilicate Ceramics by MnO2 Doping

“…As listed in Table 4 , the decreased trends of apparent density and pore volume occurred to the ceramic samples with MnO 2 doping. And the M-0.5-1150 sample has the lowest apparent density, indicating that a number of closed pores formed inside it [ 34 ]. This is probably because the liquid-phase MnO 2 forming in the sintering process filled the gaps between grains, generating more closed pores.…”

Physico-mechanical properties and shielding efficiency in relation to mineralogical and geochemical compositions of Um Had granitoid, Central Eastern Desert, Egypt

“…They have grey, pink, and white (leucogranites) colors and range from calc alkaline (syncollision) to alkaline (post-collision) as well as from metaluminous to strongly peraluminous in composition (Gharib, 2012;Abuamarah et al, 2022;. Notably, they are abundant, straddle about sixty percent of the total crystalline rocks in Egypt, and have high economic significance due to their high durability and aesthetic appearance (Alzahrani et al, 2022;Lasheen et al, 2023). Their distribution percent increases from the South to the North-Eastern Desert of Egypt (Stern and Hedge, 1985).…”