Introduction

Natural stones whether igneous, sedimentary, or metamorphic in origin are widely used as ornamental stones worldwide for various purposes such as flooring, paving, cladding, funeral monuments, and statues due to the great variety of their appearances, high durability, and compactness (Morales Demarco et al. 2013; Wahab et al. 2019; Alzahrani et al. 2022). The durability of the natural stones is a primary parameter that evaluates the performance of the ornamental stones; it could be enhanced by the polishing processes that reduce their ability for water vapor absorption. These processes also improve their aesthetic features, such as color and texture, influencing their commercial value (Hoffmann and Siegesmund 2007; Fort et al. 2013; Sitzia et al. 2022). Therefore, natural stones have been widely used as a building material for a long time in ancient heritage constructions and historical monuments such as pyramids, castles, palaces, and old historical cities (Careddu 2019; Wahab et al. 2019; ASTM C119 2014; Mosch et al. 2007; Ludovico-Marques et al. 2012; Fort et al. 2013; Vigroux et al. 2021; Freire-Lista 2021, 2022; Sitzia et al. 2021). The use of dimension stones in traditional constructions is closely related to the distribution of rock outcrops (Ludovico-Marques et al. 2012) and the vicinity of the geological resources in addition to the abundance of quarrying techniques and transporting links (Fort et al. 2013).

Natural stones, such as granite, marble, limestone, slate, travertine, or sandstone, are formed by nature and are not artificial. There are two main categories of natural stones were defined, which are siliceous stones and calcareous stones: the first category includes all igneous rocks, such as granite, basalt, gneisses, gabbro, syenites, serpentine, and slate, while the second category includes all carbonaceous stones, such as limestone, marble, onyx, and travertine, which are durable but more sensitive to acids and alkaline compounds (Marble Institute of America 2011). These groups are the main subdivision of the ornamental stones, and other stones, such as quartzite, are also included (Wahab et al. 2019; Gomes et al. 2020).

Dimension stones are any natural stones that can be cut to specific sizes or shapes. They should fulfill the normal requirements such as color, texture, and surface finish in addition to their polishing ability and durability performance for use as building facing, paving stone, curbing, monuments and memorials, and other industrial products (Marble Institute of America 2011; ASTM C119 2014; Careddu 2019; USGS 2022; Wahab et al. 2019).

The production of dimension stones for decorative purposes is increasing rapidly due to the massive expansion of building construction projects due to the continuous increase in the population (Mashaly et al. 2016; Wahab et al. 2019). The worldwide net production of dimension stones reached about one hundred fifty million tons in 2017 by 27 countries (Ericsson 2019), with major sharing of about 72% by China, India, Turkey, Iran, and Italy (Rana et al. 2016; Singh et al. 2019).

In Egypt, a wide variety of natural stones are distributed all over the country of more than fifty brands that can be utilized as dimension and ornamental stones (Sadek et al. 2016; Rashwan and Abd El-Shakour 2022), making it one of the most essential ten countries producing ornamental stones worldwide, with a sharing level estimated by 3.6% (5.25 Million tons annually) (Mashaly et al. 2016; Ericsson 2019). The Precambrian basement rocks of Egypt that represent the northwestern part of the Arabian-Nubian Shield (ANS) and consisting parts of the older crust cover a major sector (around 100,000 km2) of the country (Lasheen et al. 2021; Saleh et al. 2022a, b). They encompass the Eastern Desert, the southern part of the Sinai Peninsula, and smaller areas in the southern part of the Western Desert (Uweinat district) (Azer et al. 2016; Khaleal et al. 2022a, b; Hamdy et al. 2022).

The Egyptian granites of the Late Cryogenian-Ediacaran age represent the most plutonic rocks within the continental crust (Johnson et al. 2011; Lehmann et al. 2020) and can be used as ornamental stone (Bonin 2007).

The granitic rocks are most abundant in the northern sector of the Eastern Desert that represents the western part of the Arabian-Nubian Shield (ANS) and constituting about 60% of the basement rocks of Egypt (Kamar et al. 2022; Alharshan et al. 2022; Khaleal et al. 2023). These rocks were recorded in different tectonic regimes that range from older (grey granite) of a syn-orogenic tectonic setting (850–610 Ma) to younger (pink granite) of a late post-orogenic tectonic setting (610–550 Ma) with I- to A-types (Azer et al. 2020; Lasheen et al. 2022a, b; Sami et al. 2022). The heterogeneity of the Egyptian granites is related to their different geological settings, mineralogical constitutions, and geochemical composition. The substantial variations in the chemical and mineralogical composition of the granitic rocks, as a result of different tectonic settings, are considered to be the essential functions that affect their thermal, radioactive, reflectance, and physico-mechanical behaviors and consequently, their performances in various applications (Alzahrani et al. 2022).

Texture, grain size, deformation and alteration degree, and mineral constituents are the main petrological characteristics of rocks. They are the most important parameters for evaluating the physico-mechanical properties and durability performance of stones and their rate of degradability (Dreesena and Dusar 2004; Gupta and Ahmed 2007; Abd El– Hamid et al. 2015; Yusofa and Zabidi 2016; Eroğlu and Çalik 2023).

Ribeiro et al. (2007) investigated the influence of rock mineralogy and texture on the efficiency of the sawing operation of siliceous granitic blocks. They concluded that the greater roughness texture of the rock-cut face significantly slowed the sawing rate and consequently increased the cost of polished slab production.

Hemmati et al. (2020) investigated the relationship between the strength properties of different crystalline igneous rocks and their mineralogy and texture. They concluded a significant relationship between the size ratio of quartz to feldspar of the stones and their compressive and tensile strengths. They also concluded that the rock’s strength was significantly influenced by its grain size more than its grain shape or mineral content.

The effect of mineralogical and petrographic characteristics of ultrabasic rocks, in terms of secondary to primary minerals ratios, on their engineering properties was investigated by (Rigopoulos et al. 2012). They found a correlation between the mechanically weaker rocks and their content of secondary alteration minerals.

Natural stones of the great variation in mineralogical constituents (particularly igneous rocks) may be highly influenced by temperature changes, due to the variation in the thermal behavior of their constitutive minerals (Vigroux et al. 2021). They stated that the exposure of natural stones to heat generally results in irreversible changes in their microstructures and, accordingly on their physical and mechanical properties.

Many researchers studied the exposure of different types of stones, including granitic stones, to high-temperature heat and its influence on their physico-mechanical properties (Houpert and Homand-Etienne 1979; Zeisig et al. 2002; Sippel et al. 2007; Mosch and Siegesmund 2007; Siegesmund and Dürrast 2011; Morales Demarco et al. 2013; Heap et al. 2013; Ozguven and Ozcelik 2014; Liu and Xu 2015; Vazquez et al. 2011, 2018; Biró et al. 2019; Vigroux et al. 2021).

The variation in temperature-condition represented in freezing and thawing affect the rock’s durability, strength and stability for engineering purposes (Mousavi et al. 2019, 2020a, b, Mousavi and Rezaei 2022). They attributed the degradation rate of the physico-mechanical properties of rocks to their mineralogical components and internal microstructure.

Thermal expansion is a physical property that occurs under the change in temperatures in all materials, where most of the materials expand and contract upon heating and cooling, respectively (Siegesmund et al. 2018). During this phenomenon, the substances’ shape, length, and volume change with changing temperature (Huotari and Kukkonen 2004). Despite the minor effects of the thermal expansion of the rocks on their volume or bulk density change, the variations in the characteristics of thermal expansion of different minerals in the assemblage of mineral grains can cause structural damage upon heating the rock.

Due to the badly heat conductivity of granitic rocks, the thermal action on the stone surface is more intense than in its interior that develops a tension force causing cracks in the outer surface of the stone (Ramana and Sarma 1980; de Castro et al. 2004). Therefore, due to the variation in the minerals constitutes and texture of natural stones, most multi-mineralogical dimension stones, such as granites, exhibited an anisotropic thermal characteristic (Siegesmund and Dürrast 2011; Heuze 1983; Fredrich and Wong 1986; Gräf et al. 2013; Freire-Lista et al. 2016; Siegesmund et al. 2018).

The role of mineralogical and chemical composition in the thermal expansion and physico-mechanical behaviors of some commercial granitic rocks was investigated by Alzahrani et al. (2022). They reported an insignificant change in the linear thermal expansion of different granitic types under normal temperature conditions. Moreover, they found that the high content of iron and/or low content of quartz exhibited a high performance of physical and mechanical properties. de Castro et al. (2004) found that the thermal expansion coefficient of granitic rocks was affected by their quartz content and apparent porosity, where the increase in quartz content and apparent porosity resulted in an increase and decrease in thermal coefficient; respectively. The heating rate, thermal cycling, mineral composition, grain orientation, and crack porosity are the most important functions affecting the linear thermal expansion of granitic rocks (Ramana and Sarma 1980). Due to the variation in the dilatation behavior of rock-forming minerals, they are considered one of the main factors, in addition to the rock fabric, affecting the thermal expansion characteristics of the rocks (Siegesmund et al. 2018).

Some of the geotechnical properties of rocks, such as compressive strength and porosity, can be very important for evaluating the drillability of rocks by predicting their drilling rate index (Capik et al. 2017; Kamran 2021; Shahani et al. 2022). Also, some geotechnical parameters, such as petrography and physico-mechanical properties of rocks, can be useful for calculating the penetration and wear rate of the rock-engaging tools (Majeed et al. 2020).

Study significance

Due to the significant variations of the granitic rocks in the study area, in addition to the lack of studies about the suitability of these rocks as dimension stones, the present work aims at evaluating some varieties of the granitic stone types at Homrit Waggat area, Central Eastern Desert, Egypt, and their suitability for using as dimension stones. Moreover, the global climatic changes accompanied by the increase in temperatures significantly impact the engineering properties of these rocks. The main objective of this article is to study the effect of the chemical and mineralogical variations of the selected types on their thermal expansion behaviors and physico-mechanical properties. Additionally, the results of these properties were compared to the international standard specifications related to dimension stones. This objective was achieved using different analyses, including petrographic investigation using a polarizing light microscope and chemical analysis using X-ray fluorescence (XRF). The linear thermal expansion analysis using a dilatometer, physical properties (water absorption, bulk density, and apparent porosity), and mechanical properties (compressive strength) using the ASTM standard test methods were also performed.

Geological setting of the study area

The Cryogenian-Ediacaran age of Egyptian granites is most abundant in the northern sector of the Eastern Desert that constituting about 60% of the basement rocks of Egypt (Kamar et al. 2022; Alharshan et al. 2022; Khaleal et al. 2023). Homrit Waggat area is a separated ring-like area that lies northwest of Mersa Alam city, Central Desert, Egypt and is delineated by 25° 08′–25° 11′ Lat. and 34° 16′–34° 21′ Long., as shown in (Fig. 1). This area was studied geochemically and mineralogically by researchers, such as (Azer et al. 2020). They classified it into three main rock units from the oldest to the youngest as follows: (I) island‐arc assemblages that are represented by volcani-sedimentary and metagabbro-diorite rocks complex and forming the northern part of the examined area; (II) older granites of fine-grained, exfoliated, grey color rocks that are forming low hills with an oval shape and are intruded by several pegmatite veins; and III) Younger granitic rocks, which are the dominant unit and cover about 50 km2 forming separated sides of the area and are intruded by pegmatite and quartz veins.

Fig. 1
figure 1

a Location map of Homrit Waggat study area, Central Eastern Desert of Egypt; b Geologic map of Homrit Waggat area modified after (Azer et al. 2020)

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Experimental program

Materials

Twenty samples were selected from different locations in Homrit Waggat area, as shown in Fig. 1. These samples were collected from the unweathered surfaces of plutons using big hummers. The collected samples were cut into cubic shapes (Fig. 2) suitable for physical and mechanical tests and cylindrical shapes for thermal expansion tests. The surfaces of the specimens were polished for visual illustration (Fig. 3). The samples were petrographically described using a polarizing microscope to recognize their mineralogical components and their textural relationships as well. Representative samples were pulverized to less than 75-µm size to determine their major oxides using XRF (X-ray fluorescence, Axios, PANalytical 2005). The detection of element concentrations was carried out with Sequential WD-XRF Spectrometer using a standard guide for elemental analysis (ASTM E-1621) by wavelength-dispersive X-ray fluorescence Spectrometer. The loss on ignition (LOI) was measured according to the standard test method ASTM D-7348. Figure 4 illustrates the flow chart of the experimental program of the present study.

Fig. 2
figure 2

Photographs showing cubic specimens of the studied granitic stone (syenogranites, alkali-feldspar granites, albitized granites, granodiorites, and tonalites are selected from Homrit Waggat area

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Fig. 3
figure 3

Polished hand specimens of the studied granitic stones (syenogranites, alkali-feldspar granites, albitized granites, granodiorites, and tonalites are selected from Homrit Waggat area

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Fig. 4
figure 4

Flow-chart of the experimental study of the magamtic rock types

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Methods

Coefficient of linear thermal expansion

The coefficient of linear thermal expansion (αL) of the studied stone types and thermal strain (dL/Lo) were measured using the Dilatometer instrument (NETZSCH DIL 402 PC model) at NRC. The samples were prepared in cylindrical shapes with dimensions of around 20 mm in length and 5 mm in diameter. These cylinders were dried in an oven dryer at around (60 °C) until a constant mass was reached. They were then put inside the chamber of the dilatometer, and the heat was raised from the room temperature to 1000 °C at a rate of 5 °C/min.

Physical properties

The water absorption, apparent porosity, dry bulk density, and saturated – surface dry (SSD) or wet bulk density are the main physical parameters that were measured for the selected rock samples. The specimens of nearly cubic-shaped dimensions (50 × 50 × 50 mm) were prepared using a rock-cutting machine. These physical parameters were measured by applying the requirements of the international standard test methods (EN 1936; ASTM C97/C97M 2015) based on Archimedes method (Siegesmund and Dürrast 2011; Mosch and Siegesmund 2007) that were achieved in the Marble and Granite Testing Lab (MGTL) at NRC. According to these test methods, the samples were dried in a ventilated oven at around (60 °C) until the constant mass was reached. After drying, they were cooled for about 30 min, and then the dry weight was recorded to the nearest 0.01 g. The samples were then gradually immersed in a tap water bath (room temperature) for about two days until complete saturation. The saturated samples were removed from the water bath, and their surfaces were dried with a dumped cloth and the saturated – surface dry (SSD) weight was recorded to the nearest 0.01 g. After then they were suspended in water and their suspended weight was then recorded to the nearest 0.01 g.

The water absorption, apparent density, dry bulk density, and saturated – surface dry bulk density were calculated according to the following equations:

$$\mathrm{Water \;absorption, \;\% = 100 \times (SSD\; weight -Dry \;weight)\, / \,Dry \;weight}$$
(1)
$$\mathrm{Apparent\; porosity, \;\% = 100 \times (SSD \;weight- \;Dry \;weight)\, / \,(SSD \;weight -\;Suspended \;weight})$$
(2)
$$\mathrm{Dry \;Bulk \;density, \;kg/m^{3}} = 1000 \times \mathrm{Dry \;weight \,/ \,(SSD \;weight -Suspended \;weight)}$$
(3)
$$\mathrm{SSD \;Bulk \;density, \;kg/m^{3}} = 1000 \times \mathrm{SSD \;weight / (SSD\; weight \;Suspended \;weight)}$$
(4)

Mechanical properties

The compressive strength property of the rocks is the most important mechanical property that measures their loading capacity. Similar to the physical properties, cubic samples of dimensions (50 × 50 × 50 mm) were prepared, and the compressive strength test was carried out according to the requirements of the international standard test method (ASTM C170/C170M 2015). According to this test method, the prepared samples were completely dried in a ventilated oven at around (60 °C) until they reached constant mass. The loading area of the samples were then calculated to the nearest 0.1 mm2, then the samples were centered between the upper and lower plates, and the load was applied at a rate of 0.5 MPa/s until sample failure. The compressive strength is then calculated according to the equation:

$$\mathrm{Compressive \;strength, \;MPa} = \mathrm{Total \;load \;(N)\, / \,Loading \;area \;(mm^{2})}$$
(5)

Results and discussions

Petrography

The studied granitic rocks exhibited later deformation processes; these deformation processes resulted from local and regional stresses, as well as physical and mechanical weathering. The presence of different types of plans of weakness, such as cleavage, bedding, schistosity, fractures, and joints, influence the strength of the rock mass. All these plans of weakness also increase the effect of chemical weathering. Rock texture is also an important parameter for evaluating the physical and mechanical behaviors of the affected rocks. Although the grain size such as “aphanitic, phaneritic” or “coarse-grained, fine-grained” are used to describe the size of mineral constituents, the weathering conditions in terms of the types of the resulted secondary minerals and alteration products, all together are also reflected in the engineering properties of the rocks. According to the mineralogical composition under the polarized light microscope, the examined samples could be subdivided into five rock types based upon IUGS classification (Streckeisen 1976) and they are presented from older to younger as follows:

Tonalite

It is characterized by coarse-grained, hypidiomorphic texture. It consists mainly of plagioclase, quartz, and hornblende with a minor potash feldspar. Tabular, subhedral, and coarse-grained plagioclase crystals show an extensive kaolinitization and saussuritizaion processes (Fig. 5a). Quartz occurs as coarse - to fine-grained crystals. The coarse-grained quartz reveals a wavy extension as a result of outer deformation. Hornblende crystals are wholly altered to chlorite (Fig. 5b). Potash feldspars are represented mainly by patchy perthite crystals that are commonly fractured.

Fig. 5
figure 5

Photomicrographs showing a Completely saussuritized plagioclase (Pl) in tonalite; b hornblende (Hb) partially altered to chlorite in tonalite; c pristine-zoned plagioclase in granodiorite; d association of microcline (Mc) crystals exhibiting pristine cross hatching (Pl) crystal in syenogranites; e coarse-grained muscovite (Ms) corroded by plagioclase in alkalifeldspar granites; and f tabular albitic plagioclase in albitized granites

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Granodiorite

It is characterized by medium- to coarse-grained crystals, composed essentially of K – feldspar, plagioclase, and quartz; zircon, apatite, and titanite are encountered as the main accessory minerals. K – feldspars are represented by patchy perthite crystals characterized by turbid surfaces and poikilitically engulfing small plagioclase crystals. Plagioclase occurs as subhedral crystals exhibiting both lamellar twinned and zoned crystals (Fig. 5c). A slight turbid surface is found due to kaolinizaion processes. Quartz presents as fine- to medium-grained crystals. Biotite occurs as flaky crystals, partially to completely altered to chlorite. A wedge-like shaped titanite occurs as disseminated and/or clustered crystals. Fine-grained zircon crystals are mostly enclosed in biotite lattice.

Syenogranite

This type is characterized by medium- to coarse-grained crystals with a perfect hypidiomorphic texture. It consists mainly of K-feldspar, quartz, and plagioclase; allanite, zircon, and iron oxide are recorded as the main accessory minerals. Orthoclase–perthite (patchy type) and microcline (well cross-hatching) are the dominant K – feldspar crystals (Fig. 5d), sometimes exhibiting slightly turbid surfaces due to kaolinizaion processes. Quartz reveals a normal extension that is mostly enclosed in plagioclase crystals, giving rise to a graphic texture. Biotite flaky crystals are partially altered to chlorite. A high relief of zircon crystals is mostly hosted in mafic minerals exhibiting pleochroic halos.

Alkali-feldspar granite

It is characterized by medium- to coarse-grained crystals. It is similar to syenogranite rock type in mineralogical composition, where Quartz, K – feldspars, plagioclase, and muscovite are the main essential minerals. Kaolinized microcline and orthoclase perthite exhibit both patchy and flamy textures. Occasionally, K-feldspars found enclosing plagioclase crystals. Quartz occurs as fine- to medium-grained with normal extension. Tabular crystals of albitic plagioclase also happen. The partial alteration of biotite to chlorite is certainly observed along its peripheries. Flaky muscovite is of fine—to coarse-grained that is corroded by plagioclase (Fig. 5e).

Albitized granite

It is characterized by white color in hand specimen and fine—to medium-grained texture. It consists dominantly of plagioclase (albite), quartz, and K-feldspar. Albite exists as tabular and subhedral crystals. Rarely albite is fractured and saussuritized (Fig. 5f). Zircon is the main accessory mineral that reveal pleochroic haloes and is embedded in albite crystals. Biotite is the main mafic mineral that is slightly altered to chlorite.

The petrographic description of the studied granites exhibited deformation effects expressed as fragmentation along the borders between the adjacent plagioclase crystals (Fig. 5a). Moreover, corrosion between plagioclase and muscovite crystals was observed (Fig. 5e). Parallel cracks in plagioclase crystals without a remarked displacement in the lamellar twinning were also observed, resulting in alteration at the core of the crystal, masking its lamellae (Fig. 5f). The presence of mica minerals (biotite and muscovite) with their planes of weakness in granodiorite, syenogranite, alkali-feldspar granite, and albitized granite may weaken their physical properties by increasing the porosity. Moreover, the physico-mechanical properties may also be affected by the alteration processes, such as the kaolinization and chlorite formation.

Geochemistry

The five different granitic stones of Homrit Waggat area were chemically analyzed for their major oxide contents, as given in (Table 1), to distinguish their petrological characterization. It is noticeable that the analyzed samples revealed a variation in their chemical composition. The granodiorite contains the least SiO2 content (av. 65.61%) and the highest concentrations of Al2O3 (av. 16.72%), CaO (4.25%), and Fe2O3t (4.82%) relative to other types. On the other hand, the syenogranite exhibits the highest concentration of SiO2 (av. 76.92%) and K2O (av. 4.81%) and the least Al2O3 (av. 13.12%) and Na2O (2.27%). In addition, the albitized granites are characterized by the highest Na2O content (4.33%) and normative albite content (up to 38.85%), which is ascribed to albitization processes.

Several discrimination diagrams could be used to differentiate between the examined stone types. In terms of R1–R2 diagram (De la Roche et al. 1980), the alkali-feldspar granite, syenogranites, and albitized granite samples plot in the granite field; in contrast, the granodiorite and tonalite lie in the granodiorite field (Fig. 6a). On (Ab-Or-An) ternary diagram (Streckeisen 1976), the alkali-feldspar granites, syenogranites and albitized granite samples plot within the field of alkali-feldspar granite, syenogranite and monzogranite, respectively, while granodiorite and tonalite samples lie on the boundaries between granodiorite and tonalite field (Fig. 6b).

According to ACNK ternary diagram (De la Roche et al. 1980), the examined samples exhibit per-aluminous affinity (Fig. 6c), where Al2O3/CaO + Na2O + K2O ranges from 1.54 to 2.27. It is noticeable that the studied syenogranite has a high‐K calc‐alkaline affinity, whereas the other types are a calc‐alkaline nature (Shand 1951) (Fig. 6d). According to the SiO2-P2O5 binary diagram (Li et al. 2007), the examined granites could be further subdivided into I-type and A-type granites. The studied older granites (granodiorite and tonalite) correlate negatively with the I- (igneous) type trend. In contrast, the other types exhibit relatively constant P2O5 values with respect to SiO2, reflecting A-type (an orogenic) granite (Fig. 6e).

Several tectonic discrimination diagrams can be used to detect the tectonic regime for the examined granitic stones. The alkali-feldspar and syenogranite plot within the later calc-alkaline granites phase (III field) of late to post-collisional setting (Fig. 6f). In contrast, the studied granodiorite and tonalite types plot within the early phase of younger granites (II field). On the other hand, the albitized granites lie close to the later phase of calc-alkaline granites (III field) .

Fig. 6
figure 6

Ra1–R2 diagram of (De la Roche et al. 1980); b Ab-Or-An normative diagram of (Streckeisen 1976); c CaO-(Na2O + K2O)-Al2O3 ternary diagram of (Shand 1951); d SiO2 vs K2O binary diagram of (Rickwood 1989); e SiO2-P2O5 binary diagram (Li et al. 2007); and f Na2O-K2O-CaO of the Egyptian granitoids (Hassan and Hashad 1990), III = late subphaseof calc‐alkaline (younger granites) phase, II = early subphase of younger granites, I = calc‐alkaline diorite and metagabbro

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Table 1 Chemical composition [major (wt, %)] and normative mineral composition (wt, %) of granitic rocks in Homrit Waggat area
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Mineralogical composition

Based on the chemical analysis by XRF (Table 1), the normative mineral composition of the studied granites by CIPW (Streckeisen 1976), revealed a variation in the essential rock-forming minerals such as quartz and feldspars; and the accessory minerals such as titanite, zircon, rutile, and iron oxide minerals. As mentioned in the "Petrography" section, the plans of weakness, such as cleavages in feldspars (the most abundant minerals), may negatively affect the physical and mechanical properties of the studied granites. It is observed from the statistical distribution of the normative chemical composition as shown in (Table 2) that the least normative quartz content was recorded in granodiorite (av. 31.70%), while the highest content was recorded in syenogranite (av. 43.53%). The highest total content of normative feldspars was detected in the albitized granite (av. 55.40%), reflecting its high alkali oxides, particularly Na2O (av. 4.83%). On the contrary, the lowest feldspar content was seen in the tonalite (av. 45.71%), which reflects its lowest alkali oxides content (4.31%). The granitic rocks exhibiting the highest quartz and lowest feldspar contents, respectively, may reveal an improvement in their physical and mechanical properties. The ferromagnesian mafic minerals may also have a reverse effect on the physical and mechanical properties of the granitic rocks. This effect may result from the perfect two sets of cleavage (e.g., hypersthene mineral), which are considered plans of weakness. The highest content of the normative mafic minerals was recorded in granodiorite samples (av. 8.58%), reflecting its high contents of Fe2O3t (4.83%) and MgO (1.46%). On the contrary, the low contents of iron and magnesium oxides, as recorded in alkali-feldspar granite (0.42% and 0.10%) and albitized granite (0.62% and 0.03%), confirmed the low contents of their normative mafic minerals (av. 0.78% and 0.77%); respectively.

Table 2 Statistical distribution of major oxides and normative minerals of granitic stone types in Homrit Waggat area
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Linear thermal expansion coefficient

The increase in linear dimensions, such as length under, the temperature effect, could be used to measure the material’s expansion. Therefore, the fractional increase in the specimen’s length (linear dimension) per unit rise in temperature can be called the linear thermal expansion coefficient (James et al. 2001).

Siegesmund and Dürrast (2011) mentioned that the coefficient of thermal expansion depends mainly on the temperature range, especially at higher temperature range up to 1000 °C due to the transition of (α-β) quartz phase near 600 °C for the quartz-bearing rocks.

The numerical formula for calculating the coefficient of linear thermal expansion could be grouped into two broad categories; the first one is “temperature range-dependent expansion,” while the second is “single temperature-dependent expansion” (James et al. 2001) as follows: The first category is defined as “the average or the mean coefficient of linear thermal expansion (αm)” over a temperature range (James et al. 2001; Wang et al. 2020; ASTM E 228; ASTM E 289) according to the following general equation:

$${\boldsymbol{\alpha }}_{{\varvec{m}}}=\frac{({{\varvec{L}}}_{2}-{{\varvec{L}}}_{1})/{{\varvec{L}}}_{{\varvec{o}}}}{{{\varvec{T}}}_{2}-{{\varvec{T}}}_{1}}=\left(\frac{1}{{{\varvec{L}}}_{{\varvec{o}}}}\right)\boldsymbol{*}\boldsymbol{ }\left(\frac{\Delta {\varvec{L}}}{\Delta {\varvec{T}}}\right)$$
(6)

where αm is related to the slope of the chord between two points on the curve of length against temperature (Fig. 7) (James et al. 2001; Wang et al. 2020). It represents the expansion over a particular temperature range from T1 to T2; Lo represents the initial specimen’s length at temperature To (reference temperature) that expands to L1 at temperature T1 then to L2 at temperature T2, while ΔL is the change in specimen’s length for the temperature change ΔT.

Fig. 7
figure 7

Linear thermal expansion behavior of different granitic stones (green: syenogranite, red: alkali-feldspar granite, blue: albitized granite, purple: granodiorite, brown: tonalite) under increasing temperatures

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The second category is termed “true coefficient of linear thermal expansion (αT) that is related to the derivative (dL/dT) at a single temperature (James et al. 2001; Wang et al. 2020), which can be defined according to the following equation:

$${\boldsymbol{\alpha }}_{{\varvec{T}}}=\frac{{\varvec{d}}{\varvec{L}}/{\varvec{L}}{\varvec{o}}}{{\varvec{d}}{\varvec{T}}}=\boldsymbol{ }\boldsymbol{ }\frac{1}{{\varvec{L}}{\varvec{o}}}\frac{{\varvec{d}}{\varvec{L}}}{{\varvec{d}}{\varvec{T}}}$$
(7)

where αT is the tangent’s slope to the length curve against temperature (James et al. 2001), and dL/Lo is the derivative of thermal strain (Gautam et al. 2019).

The results of the coefficient of linear thermal expansion (α), as well as the change in specimen’s length as functions of temperature change for the studied granitic types were graphically illustrated in (Figs. 7 and 8).

Fig. 8
figure 8

a Caoefficient of linear thermal expansion (αm, K−1), b mean thermal strain (dL/Lo, %), of granitic stone types at Homrit Waggat area at different temperatures

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As shown in (Fig. 7), the thermal strain (dL/Lo, %) of the studied granites can be subdivided into three temperature ranges: the first range lies between the reference (starting) temperature up to 100 °C, the second range lies between 100 °C up to 600 °C, while the third range lies between 600 °C and 1000 °C. In the first range, the different granites recorded an insignificant increase in the thermal strain by 0.049%, 0.018%, 0.017%, 0%, and 0.019% for syenogranite, alkali-feldspar granite, albitized granite, granodiorite, and tonalite; respectively. Through the second temperature range, the thermal strain increased exponentially and reached at the end of this range (600 °C) 1.519%, 1.555%, 1.699%, 2.099%, and 1.607% for the respective types. The explanation of this variation could be attributed to the thermal strain variations in proportions of the mineralogical composition and the variance in their thermal expansion as well (Gautam et al. 2019). Through the last temperature range, the thermal strain increased gradually for all respective rocks except for granodiorite, which showed a continuously exponential increase that reached up to 1000 °C to 4.987%. This increase may be due to its high feldspar content which reached about 53.67% compared to its low quartz content (31.7%), in addition to the high content of total iron oxide (4.73%) that are represented by high content of normative mafic minerals (8.58%).

It can be noticed from (Fig. 7) that the increase in temperature up to (600 °C) led to an increase in the mean linear thermal expansion coefficient (αm), with very similar values ranging from (26.42 × 10–6 / K−1 to 29.37 × 10−6 / K−1) followed by a decrease in coefficient values by increasing the temperature over 600 °C, which is similar to the results reported by (Alzahrani et al. 2022). This phenomenon was recorded in the syenogranites, alkali-feldspar granites, albitized granites, and tonalities except for granodiorite, as shown in (Fig. 8a). This indicates that the granites of higher normative quartz content exhibited lower thermal expansion coefficient values above the phase transition temperatures (α-β) of quartz that appear near 600 °C (Plevova et al. 2016).

On the other hand, it is also observed from (Fig. 7) that all the investigated granites showed at least one sharp peak (increase) in the single temperature-dependent linear thermal expansion coefficient (True coefficient, αT) curve with variable (αT) values depending on their mineralogical composition. The first sharp peak starts at 525 °C and ends at 575 °C, with a central point at 550 °C. This sharp peak appears in the thermal behavior of all granites with variable αT values of 105, 170, 190, 225, and 270 (× 10−6 /K−1) for syenogranite, alkali-feldspar granite, albitized granite, granodiorite, and tonalite, respectively. The variation in these values may be connected with the variable proportions of quartz and feldspar minerals (orthoclase, albite, and anorthite) between the studied samples, as given in (Table 1). The first sharp peak, as shown in (Fig. 7), is well matching with the transitional state of both (αm and dL/Lo) curves at the same temperature ranges that express the (α-β phase transition) of quartz mineral at around 573 °C (Wang et al. 2020). The second jump or increase in the thermal coefficient curve was detected at variable temperature ranges of 800 to ≈ 900 °C, 600 to 750 °C, and 900 to 1000 °C for alkali-feldspar granite, granodiorite, and tonalite, respectively. Similar to the first sharp peak, the second peak matches with the transitional state of thermal strain (dL/Lo) curve as well as the average thermal coefficient (αm) curve at the same temperature ranges. The variation in the temperature ranges for the second sharp peak between the respective types may be attributed to the significant variation in their mineralogical composition mainly quartz and feldspar contents, as presented in (Table 1).

As shown in (Fig. 8b), the change in long dimension relative to the initial length (expressed as thermal strain, dL/Lo, %), increases with increasing the temperature difference (dT). The granodiorite recorded the longest expansion with 4.987% thermal strain, while syenogranites exhibited the lowest long expansion with a thermal strain value of 1.923% at 1000 °C. This may be attributed to the high SiO2 content (Table 1) that forms the main mineral constituents of the studied granitic stones (quartz and feldspar). Also, it may be related to the high content of iron oxide (4.73%) of granodiorite compared to syenogranite (1.70%).

Figure 9a, b illustrate the effect of mineralogical composition on the thermal behavior of the samples at different temperatures. It is observed that the linear thermal expansion coefficient and, consequently, thermal strain increase with increasing quartz/quartz + feldspar content at low temperatures (100 °C), similar to the results obtained by (de Castro 2004; Siegesmund et al. 2018). On the contrary, a reduction in the thermal coefficient and thermal strain with increasing quartz/quartz + feldspar content was observed (Fig. 9c, d) at higher temperatures exceeding (α-β) phase transition temperatures of quartz (> 600 °C) (Siegesmund and Dürrast 2011; Vigroux et al. 2021). These findings were similar to the results obtained by Plevova et al. (2016). Unlike the other rock types, the granodiorite type, showed an increase in the linear thermal expansion coefficient and thermal strain above 600 °C. This behavior may be attributed to its high content of iron oxide (av. 4.83%), besides the presence of high contents of magnesium oxide (av. 1.46%) and calcium oxide (av. 4.25%) that act as fluxing agents.

Fig. 9
figure 9

Linear thermal expansion coefficient (αm) and thermal strain (dL/Lo) as a function of mineral composition (quartz and feldspar content) at different temperatures

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Physico-mechanical properties

Evaluating any rock for various applications, such as dimension stones, requires knowing several parameters, such as physical and mechanical properties.

The results of physical properties (water absorption, apparent porosity, bulk density) and mechanical properties (compressive strength) of the studied magmatic rock types were presented in (Table 3) and graphically illustrated in (Fig. 10). The measured properties of 20 representative stone samples of the different magmatic rocks were statistically distributed using average (mean), standard deviation, minimum, and maximum parameters as shown in (Table 3).

Table 3 Statistical distribution of physico-mechanical properties of granitic stone types at Homrit Waggat area
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Fig. 10
figure 10

Physical and mechanical properties of different granitic stone types at Homrit Waggat area: a water absorption; b apparent porosity; c dry and saturated -surface dry (SSD) bulk density; d density & iron content relationship; e compressive strength; f compression & normative quartz + feldspar content relationship

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Physical properties

It is observed from (Fig. 10a) that the minimum water absorption value was recorded in tonalite by 0.14%, corresponding to 0.39% apparent porosity. These low values could be related to the lower content of feldspar minerals compared to the other granites. On the contrary, the maximum absorption values were recorded in the other types with close ratios ranging from 0.44% in syenogranite to 0.52% in alkali-feldspar granite, corresponding from 1.14 to 1.36% apparent porosity values, respectively. The petrographic description of these types exhibits the presence of mica minerals (biotite and muscovite), in addition to their partial or wholly alteration to chlorite. Furthermore, a type of the studied granite (alkali-feldspar granite) exhibits a corrosion between plagioclase and muscovite crystals (Fig. 4e). Another type (albitized granite) displays parallel cracks in plagioclase crystals resulting in alteration at the core of the crystal (Fig. 4f). These features confirm the high apparent porosity and water absorption of some types of the studied granites. As seen in (Fig. 11), the water absorption increases with increasing the apparent porosity exhibiting a significantly positive correlation coefficient (r = 0.99). Compared with other studies, Alzahrani et al. (2022) found that some Egyptian commercial granites achieved water absorption and apparent porosity values ranging from 0.14–0.31% to 0.36–0.82%, respectively, which are nearly similar to the present study. On the contrary, a high range of water absorption values of 0.78–3.53% (Freire-Lista et al. 2022) and apparent porosity values of 1.12–6.66% (Freire-Lista et al. 2022) and 0.3–3.37% (Siegesmund et al. 2018) were recorded in other granitic stones.

Fig. 11
figure 11

The relationship between physico-mechanical properties of different magmatic rock types

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Regarding bulk density, tonalite and granodiorite are the densest types, with 2748.23 kg/m3 and 2724.35 kg/m3, respectively. On the other hand, syenogranite, albitized granite, and alkali-feldspar granite revealed lower density values with 2617.07 kg/m3, 2612.28 kg/m3, and 2590.42 kg/m3, respectively, as shown in (Fig. 10c). From the chemical and normative mineralogical composition of the studied granites (Table 1), it can observe that the densest types have higher iron oxide and mafic minerals contents than the others. These confirm the strong relationship between the bulk density and the iron oxide content (Fe2O3t, %) (Fig. 10d) with a strong positive correlation coefficient by (r = 0.92). The bulk density was negatively affected by the porosity, where the increase in the apparent porosity reduces the dry and wet bulk densities, as plotted in (Fig. 11) with a negative correlation coefficient (r =  − 0.69). It can also be seen that the bulk density of granodiorite is lower than tonalite despite its higher iron oxide content. The explanation can be attributed to its high apparent porosity (1.26%) compared to tonalite (0.39%). Compared the density values with other studies, many researchers studied various types of granitic stones. A similar range of bulk density of 2.58–2.68 g/cm3 (Török and Török 2015) and 2.55–2.84 g/cm3 (Mosch and Siegesmund 2007; Siegesmund and Dürrast 2011; Morales Demarco et al. 2013) were attained. Conversely, ranges of the density of 2.48–2.63 g/cm3 (Dionísio et al. 2021) and 2461–2649 kg/m3 (Freire-Lista et al. 2022) were found to be slightly low.

Mechanical properties

Figure 10e illustrates the compressive strength results of different magmatic rock types. The value of compressive strength of any rock type is one of the most important data in many fields of engineering such as mining, tunneling and road planning (Shahani et al. 2021). Moreover, the values of compressive strength can be used to evaluate the drillability of rocks through predicting their drilling rate index (Shahani et al. 2022; Kamran 2021).

As illustrated in Fig. 10e, the highest compressive strength value was recorded in alkali-feldspar granite by 628.75 kg/cm2 (61.66 MPa), while the lowest value was recorded in tonalite by 314.17 kg/cm2 (30.81 MPa). In addition, intermediate ratios of the compressive strengths were achieved in granodiorite, syenogranite, and albitized granite with 390.58 kg/cm2, 487.7 kg/cm2, and 383.62 kg/cm2, respectively. The fragmentation along the borders between the adjacent plagioclase crystals and their extensive kaolinization and saussuritizaion (Fig. 4a), in addition to the complete alteration of hornblende to chlorite (Fig. 4b), could be the main causes that interpret the low compressive strength of tonalite. The effect of normative mineral composition and physical properties on the compressive strength of the studied granites are well illustrated in Figs. 10f and 11). As shown in Fig. 10f, it was found that the values of compressive strength increase with increasing the amount of normative quartz and feldspar content. In the same line, as plotted (Fig. 11, there is a coherent relationship between the compressive strength of the studied granite and their bulk densities exhibiting a negative correlation coefficient (r = -0.76). Comparing the present results of compressive strength with the previous studies, Török and Török (2015) attained similar results in the range of (39.1–74.3 MPa) on a pinkish granite type.

Comparing the results of bulk density of the studied granites with the specification limits of granite dimension stone according to (ASTM C615/C615M 2011), it was found that all samples comply with the requirements of bulk density of a minimum limit (2560 kg/m3). Although the compressive strength results of the studied granites did not achieve the minimum requirement of the same specification (131 MPa), the present compressive strength values could be acceptable for interior use and the light-duty purposes of exterior use as facades and cladding.

Regarding the water absorption results, the present values of studied samples (0.44–0.52%) are slightly higher than the maximum specification limit (0.40%) and considered insignificant in countries with arid conditions.

Conclusions

Different granitic rock types were selected from Homrit Waggat area, Central Eastern Desert, Egypt. They were studied from mineralogical, physico-mechanical, and thermal expansion points of view to assess their suitability as dimension stones and the main findings are drawn as follows:

  1. (a)

    The petrographic investigation of the studied granites revealed the following:

    • Tonalite is characterized by coarse-grained crystals with a hypidiomorphic texture. It consists mainly of plagioclase, quartz, and hornblende with a minor potash feldspar. Granodiorite is characterized by medium to coarse-grained crystals and is composed essentially of K – feldspar, plagioclase, and quartz; zircon, apatite, and titanite are encountered as the main accessory minerals. Syenogranite is characterized by medium- to coarse-grained crystals with a perfect hypidiomorphic texture. It consists mainly of K-feldspar, quartz, and plagioclase; allanite, zircon, and iron oxide are the main accessory minerals. Alkali-feldspar granite is similar to syenogranite in mineralogical composition with more microcline and orthoclase perthite. Albitized granite consists dominantly of plagioclase (albite), quartz and K-feldspar.

    • The studied granitic rocks suffered from various degrees of deformation. These deformation processes resulted from local and regional stresses and physical and mechanical weathering expressed as fragmentation and corrosion along the borders between the adjacent crystals. These deformations resulted in cracks with/without a remarked displacement in the lamellar twinning of plagioclase crystals. Moreover, these deformations led to the formation of plans of weakness, facilitating the alteration processes for the existing primary minerals.

  2. (b)

    The chemical discrimination diagrams revealed that each rock sample plotted in its equivalent classification field. The CIPW norm calculation revealed that syenogranite, alkali-feldspar granite, and albitized granite are more enriched in quartz and feldspars (95.24%, 93.70%, and 94.09%), respectively, instead of (88.59% and 85.37%) in tonalite and granodiorite. The iron-rich minerals (e.g., hypersthene, magnetite, ilmenite, and hematite) are more abundant in granodiorite and tonalite (8.58% and 5.17%) than the other samples. The geochemical characteristics of the present granitic rocks revealed that syenogranites, alkali-feldspar granite, and albitized granites evolved at an-orogenic tectonic suits (A-type). In contrast, granodiorite and tonalite samples are more related to subduction-related magmatism (orogenic).

  3. (c)

    The thermal behavior of the studied granites exhibited a great variation toward the thermal coefficient and thermal strain under variable temperatures and mineral composition as follows:

    • The quartz and feldspar-rich samples exhibited a much higher linear thermal expansion coefficient and consequently thermal strain at low temperatures (100 °C) with a significant correlation coefficient (r = 0.79). On the contrary, above 600 °C, a reduction in the thermal expansion coefficient and thermal strain was noticed with a significant correlation coefficient (r =  − 81).

    • The amount of thermal strain is in significant up to 100 °C, as it did not exceed 0.049% for all samples, which is convenient for using in regions with high temperature conditions.

  4. (d)

    The physico-mechanical properties of the studied granites seemed to be affected by their mineral composition and petrographic features, such as deformation processes, that led to the development of plans of weakness, and consequently, facilitated the alteration processes. A positive relationship between bulk density and the amount of iron-rich minerals with significant correlation coefficient (r = 0.92) and a positive relationship between compressive strength and normative quartz and feldspar content (r = 0.56). However, the studied granites satisfied the requirements of dimension stone in terms of bulk density, and to some extent water absorption. Although the compressive strength values did not achieve the minimum requirements, they could be acceptable for the interior use and the light duty purposes of the exterior use such as facades and cladding.