The Implication of Petrographic Characteristics on the Mechanical Behavior of Middle Eocene Limestone, 15Th May City, Egypt

sustainability

Article The Implication of Petrographic Characteristics on the Mechanical Behavior of Middle Eocene Limestone, 15th May City, Egypt

Abdelaziz El Shinawi 1 , Peter Mésároš 2 and Martina Zele ˇnáková 3,*

1 The Environmental Geophysics Lab (ZEGL), Department of Geology, Faculty of Science, Zagazig University, Zagazig 44511, Egypt; [email protected] 2 Institute of Technology, Economics and Management in Construction, Faculty of Civil Engineering, Technical, University of Košice, 042 00 Košice, Slovakia; [email protected] 3 Institute of Environmental Engineering, Faculty of Civil Engineering, Technical, University of Košice, 042 00 Košice, Slovakia * Correspondence: [email protected]

Received: 19 October 2020; Accepted: 13 November 2020; Published: 20 November 2020

Abstract: The construction purposes of carbonate rocks are considered a major aspect of using these bedrocks based on their mechanical behavior. Accordingly, the physical and mechanical characterization of Middle Eocene Limestone bedrock in the new urban area at the 15th May City, Egypt was studied to assess the suitability of the carbonate rocks for construction. This study has been carried out to investigate the effect of petrographic characteristics on mechanical properties. To achieve this objective, the intact 30 rock core samples from 15 boreholes were selected at different depths. Based on study of the selected samples in thin sections, the limestone in the area was classified as lime-mudstone, wackestone, and grainstone. Additionally, the uniaxial compressive strength (UCS) and Schmidt Rebound Hammer (Rn) were determined to detect the mechanical properties of the limestone bedrock. The measured parameters (UCS and Rn) demonstrated a high direct relationship with mudstone and a poor direct relationship with dolomite and high negative correlation with wackestone and grainstone. Therefore, the Middle Eocene Limestone bedrock is more durable and has medium-strength, which made it suitable for constructions. Regression analysis was performed to find out some linear relationship between mechanical properties (UCS) with petrographic characteristics. The study reveals significant positive correlation between UCS and Rn with mudstone in accordance higher values of regression coefficient (R2 = 0.91 and R2 = 0.036), and an inverse relationship of Rn with dolomite % (R2 = 0.89 and R2 = 0.02), respectively. Consequently, the strong confidence on the mechanical parameters opens the way for engineers to predict the mechanical parameters that are required for engineering properties of limestone for the urban expansion.

Keywords: lime-mudstone; unconﬁned compressive strength; Schmidt hammer; wackestone

1. Introduction Generally, limestone has been considered the main bedrock for roads, bridges, and tunnels construction, slope protection engineering, and water conservancy [1–3]. Recent expansion of the urban area over the surrounding desert land has directed the attention to investigate both the engineering and geological constrains on these new developments. This city was constructed on Eocene limestone beds intercalated with thin beds of clay and very thin beds of salt. In general, the Eocene limestone sediments in Egypt are characterized by karstiﬁcation phenomena causing fractures, cracks, cavities, and land subsidence.

Sustainability 2020, 12, 9710; doi:10.3390/su12229710 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 9710 2 of 15

Peak strength and mechanical deformation characteristics of limestone directly relate to these projects’ stability and is therefore helpful to forecast risk [4–7]. Furthermore, research on the behavior of limestone under natural and experimental conditions is helpful in explaining rheological characteristics of upper crustal rocks, chemical and physical effects of fluid in geologic processes, the meaning of tectonophysics, structural adjustment of the upper crust, and dynamic processes of fault zone formation and evolution with fluid; it is also helpful in explaining seismogenic mechanisms and seismic wave propagation [8–11]. The study area, located at the northern part of 15th May City, 12 km to the southeast of Cairo, is one of the promised cities planned in 1986 by the Egyptian government through its program to withdraw the population from the condensed. It was proposed for the installation of a new industrial zone that shall contain housing and manufacturing facilities. New urban communities are located in the study area, some of which are in close proximity to such quarry locations such as 15th May city, south of Helwan City. Being constructed over a limestone plateau, the city is surrounded by an old quarry, which was moved to a distance of 5 km away from the city (Figure1). Such quarry has been operated on a faulted area with weak zones of brittle materials [12]. The area encompasses seven new cities that have been partially constructed during the last decades. The cities are 10th Ramadan, El Ebour, New Cairo, El Amal, El Sherouk, 15 May, and Badr. Seven factors triggering landslides—slope angles, rock type, faults, elevation, seismic intensity zones, stream density, and land cover—were input to the model to produce a landslide susceptibility map. Such a map was used to examine the susceptibility of the locations of the seven new cities. The result revealed the high vulnerability of the locations of El Amal and 15 May Cities and a few zones including south of Cairo city [13,14]. In geotechnical and engineering projects, rock classifications are based on mechanical parameters such as uniaxial compressive strength (UCS), Point load, and Schmidt Rebound Hammer (Rn). These parameters are most widely used and adequate to characterize the mechanical behavior of rocks. The development of construction occupation increases the demands of construction materials and necessitates study on all sides of petrographic and mechanical properties of various rocks. Mechanical properties of intact rocks are greatly influenced by their textural characteristics. However, many researchers have conducted mineralogical studies on the limestone rocks [15–19]. Aggregate degradation (AD) commonly decreases particle angularity, surface texture, and size, and also diminishes the shear strength and grade of aggregate materials. In this case, AD is one of the main reasons accounting for the failure mechanism of aggregate materials. It is possible to predict AD properties from each kind of rock strength test based on rock types. Accordingly, using the equations obtained by tests to estimate the AD can be more economical and practical, especially in prefeasibility study, to predict the limits of allowable AD values for practical applications [20,21]. On the other hand, the validity of rocks to be used as construction material is the function of its mineralogical composition [16,22]. UCS of rocks aggregate is indirectly related to their mineral constituents, bioclasts, cement, and texture. Physical properties and mechanical behavior of rocks are influenced by modal mineral composition and grain size [23]. Physical properties of construction materials are directly related to UCS, mineralogical, and textural characteristics of rocks. Consequently, tests of the physical and mechanical properties were conducted for the collected rock core samples for determining the relation between mechanical behavior and mineralogical composition [6]. This study has been carried out to investigate the effect of petrographic characteristics on mechanical properties. These relations have their own effect for predicting the rock strength characteristic and their suitability for different engineering structures in 15th May City, southeast Cairo, for construction purposes, which are in close proximity to such quarry locations (Figure1). SustainabilitySustainability 20202020, 12,, x12 FOR, 9710 PEER REVIEW 3 of 15 3 of 14

FigureFigure 1. 1.LocationLocation map map of thethe studystudy area area and and the the drilled drilled boreholes. boreholes. 2. Geologic Setting 2. Geologic Setting Topographically, the area has two plateaua separated by a topographically low area. Gabal Mokattam Topographically,forms the northern plateau the area and is has separated two plateau from thea southern separated plateau by by a atopographically topographically low low area area. that Gabal Mokattamis occupied forms by El-Maadi-Qatamia the northern road plateau [24]. and is separated from the southern plateau by a topographicallyThe northern low area plateau that slopes is occupied gently northwards by El-Maadi where-Qatamia it disappears road under[24]. the Oligocene sands and gravels of Gebel El-Ahmer. A relatively high escarpment and its northern side mark the southern The northern plateau slopes gently northwards where it disappears under the Oligocene sands plateau. It is known here as Tura-Hof-Observatory plateau. The Middle Eocene beds are mainly and gravelscomposed of ofGebel limestone. El-Ahmer. These bedsA relatively are found high to be eitherescarpment unfossiliferous and its or northern containing side badly mark preserved the southern plateau.fossils. It is These known beds here were as divided Tura-Hof into-Observatory two formations plate fromau. bottom The Middle to top: The Eocene Gebel beds Hof are and mainly composedObservatory of limestone. Formations. These A brief beds description are found of both to formations be either is as unfossiliferous follows. or containing badly preservedThe fossils. stratigraphic These successionbeds were of divided the study into area istwo subdivided formations into thefrom Mokattam bottom and to Maaditop: T Groups.he Gebel Hof and ObservatoryThe Mokattam Formations. group is composed A brief of description the Gebel Hof of both Formation; formations it is the is oldestas follows exposed. rock unit Thein the stratigraphic study area. It succession accomplishes of about the study 121 m thick area and is subdivided is composed into of white the limestone,Mokattam ﬁne and to Maadi medium, hard, and medium to thick bedded lithological unit (Figure2). Observatory Formation: Groups. The Mokattam group is composed of the Gebel Hof Formation; it is the oldest exposed rock Stratigraphically, it is the highest formation of the Middle Eocene age. It is mainly composed of chalky unit inand the marly stud limestoney area. It formingaccomplishes the main about quarrying 121 m horizons thick and at Helwan is composed town and of white the neighborhood. limestone, fine to medium,This formation hard, and is typically medium developed to thick belowbedded the Helwanlithological Observatory, unit (Figure forming 2). the Observatory entire Observatory Formation: Stratigraphically,plateau and extending it is the to highest the north formation where it is of thrown the Middle down against Eocene the age.Gebel It Hof is Formation.mainly composed It is of chalkymade and up marlyof 136 m limestone limestone and forming chalky limestone the main of di quarryingﬀerent lithologies horizons and textures. at Helwan It is burrowed, town and the neighborhood.laminated, thinThis bedded, formation and is weathered. typically Consequently,developed below in the the Maadi Helwan group, Observatory, these Upper Eocene forming the entiresediments Observatory are overlying plateau theand Middle extending Eocene to Mokattam the north group where in theit is study thrown area. down It is dividedagainst into the Gebel three formations; Qurn Formation is composed of 97 m thick sequence of marly and chalky limestone Hof Formation. It is made up of 136 m limestone and chalky limestone of different lithologies and alternating with shales, sandy marls. Wadi Garawi Formation is composed of a 25 m thick poorly textures. It is burrowed, laminated, thin bedded, and weathered. Consequently, in the Maadi group, fossiliferous sandy shale section with a hard highly fossiliferous middle bed. Wadi Hof Formation is thesemade Upper up Eocen of thee Late sediments Eocene sediments are overlying that are the composed Middle ofEocene limestone, Mokattam clays, marl, group and in sandstone, the study area. It is divided65 m thick. into three formations; Qurn Formation is composed of 97 m thick sequence of marly and chalky limestone alternating with shales, sandy marls. Wadi Garawi Formation is composed of a 25 m thick poorly fossiliferous sandy shale section with a hard highly fossiliferous middle bed. Wadi Hof Formation is made up of the Late Eocene sediments that are composed of limestone, clays, marl, and sandstone, 65 m thick. Sustainability 2020, 12, 9710 4 of 15 Sustainability 2020, 12, x FOR PEER REVIEW 4 of 14

Figure 2. ((aa)) Geologic Geologic map map of of the the northern northern part part of of 15th 15th May May City City and and ( (bb)) s stratigraphictratigraphic column column showing showing the geological setting [[13].13].

3. Materials and Methods The mechanical behavior of the limestone samples was performed by the field field and laboratory work. The field field workwork represents rock samplingsampling alongalong thethe studystudy areaarea (Figure(Figure1 1).). A totaltotal ofof 30 30 continuous continuous core core samples, samples intended, intended to beto representativebe representative of the of foundationthe foundation bedrock, bedrock, 50 to 7050 mmto 70 in mm diameter, in diameter, were extracted were extracted from 15 from boreholes 15 boreholes with depths with that depths ranged that between ranged 10between and 30 meters10 and using30 meters diamond using corediamond bit fixed core on bit rotary fixed drillingon rotary machine. drilling Anmachine. extensive An extensive laboratory laboratory testing program testing wasprogram encountered was encountered to define the to physical, define mechanical the physical, properties, mechanical and petrographicproperties, and characteristics petrographic of thecharacteristics rock material of the for rock the foundation material for bedrock. the foundation Consequently, bedrock. the Cons physicalequently, properties the physical of the properties limestone samplesof the limestone along the samples study site along were the performed; study site water were contentperformed [25],; water density content [26], and [25], specific density gravity [26], [and27]. Furthermore,specific gravity the [27]. mechanical Furthermore, parameters the mechanical of the limestone parameters intact of corethe limestone samples were intact determined core samples by usingwere determined the Schmidt reboundby using hammerthe Schmidt and uniaxial rebound compressive hammer and strength. uniaxial The compressive Schmidt hammer strength. test wasThe performedSchmidt hammer within test 5◦ of was vertical performed with the within bottom 5° of thevertical piston with at rightthe bottom angles of to, the and piston in firm at contactright angles with, theto, and surface in firm of thecontact test specimenwith, the surface [28]. The of Schmidtthe test specimen rebound hammer[28]. The testSchmidt was performedrebound hammer on N-type test rockwas performed core specimens. on N Rock-type corerock specimens core specimens were steadily. Rock core fixed specimens in a steel cradlewere steadily with a semifixed cylindrical in a steel machinedcradle with slot a semi of the cylindrical same radius machined as the core, slot orof firmlythe same seated radius into as a the steel core, V-shaped or firmly block. seat Coreed into rock a samples,steel V-shaped with a length-to-diameterblock. Core rock samples, ratio of 2.5–3.0, with a werelength prepared-to-diameter and flattened ratio of up2.5 to–3.0, 0.02 were mm withprepared both sidesand flattened smooth forup uniaxialto 0.02 mm compression with both testing sides smooth following for the uniaxial specifications compression of previous testing authors following [29 ,30the]. Since all the UCS tests were conducted on an NX sized core (54 1 mm), all results were corrected by specifications of previous authors [29,30]. Since all the UCS tests± were conducted on an NX sized core using(54 ± 1 relation mm), all [31 results] to rule were out corrected the influence by using of specimen relation volume. [31] to rule Selected out the representative influence of intact specimen core specimensvolume. Selected of Middle representative Eocene limestones intact core were specimens prepared of and Middle tested Eocene for measuring limestones their were mechanical prepared propertiesand tested underfor measuring uniaxial compression.their mechanical A universal properties testing under machine uniaxial (Instron, compression. Model A 1128) universal was used testing for thesemachine tests. (Instron, The loading Model system 1128) of was this used machine for these is a controlled tests. The strain loading type system giving of deformation this machine speeds is a fromcontrolled 0.05 mmstrain/min type to giving 500 mm deformation/min. The compressivespeeds from 0.05 force mm/min produced to 500 by mm/min. this machine The compressive ranges from 10force gm produced to 50 Kg. by The thi testings machine machine ranges is from provided 10 gm with to 50 a plotterKg. The for testing producing machine testing. is provided Additionally, with a theplotter petrographical for producing study testing. of the Additionally, selected samples the petrographical was performed study whereby of the five selected thin sections samples were was performed whereby five thin sections were prepared, examined under a microscope, and the limestone samples were classified. The limestones were examined by a Laboval-3 optical microscope Sustainability 2020, 12, 9710 5 of 15 Sustainability 2020, 12, x FOR PEER REVIEW 5 of 14 prepared, examined under a microscope, and the limestone samples were classified. The limestones in transmittedwere examined plane by- (PPL) a Laboval-3 and cross optical-polarized microscope light in transmitted(XPL) to perform plane- (PPL)a semi and-quantitative cross-polarized analysis of thelight components (XPL) to perform (texture, a semi-quantitative matrix composition analysis, and of grain the components types). Micrographs (texture, matrix were composition, simultaneously acquiredand grain by types).a Nikon Micrographs Coolpix were 990 simultaneouslydigital camera acquired at 1.2 by megapixel. a Nikon Coolpix Limestone 990 digital samples camera were categorizedat 1.2 megapixel. according Limestone to the classification samples were of categorized depositional according textures to theof carbonate classification rocks of depositional proposed [29]. textures of carbonate rocks proposed [29]. 4. Results 4. Results

4.1. Study4.1. Study Site SiteDescription Description ThreeThree main main rock rock types types of of layers layers were were observed from from the the boreholes boreholes and and the crossthe cross sections sections (Figure (Figure3) 3) as asfollow follows.s.

FigureFigure 3. ( 3.a) (a D)rilled Drilled boreholes boreholes locations locations and and cross cross sections; sections (b) composite; (b) composite log from the log drilled from boreholes the drilled boreholesin the in study the sitestudy based site on based collected on collected intact rock intact samples. rock samples.

Surface layer characterizes overburden materials and composed of weathered limestone. Surface layer characterizes overburden materials and composed of weathered limestone. The The average thickness of this layer varies between 0.7 and 3 m. The middle layer is composed averageof argillaceous thickness limestone of this layer facies varies with thickness between ranges 0.7 and between 3 m. 0.5The to m 30iddle m. The layer bottom is composed layer is of argillaceouscharacterized limestone by highly facies argillaceous with thickness limestone rangesbedrock betweenwith pockets 0.5 of to marl 30 intercalations m. The bottom layer is characterized by highly argillaceous limestone bedrock with pockets of marl intercalations

4.2. Petrographic Characteristics and Depositional Environment The investigated Middle Eocene limestone rock samples were texturally classified according to [29] into lime-mudstone, wackestone, and grainstone (Table 1). The major component, lime- mudstone, shows a high percentage of mud and fine materials, which varied in the range of 43% to 85% with a mean of 63.8% and a standard deviation of 13.64. However, wacketone was represented with a high percentage of grains in the range of 4% to 28% with a mean of 15.1% and a standard Sustainability 2020, 12, 9710 6 of 15

4.2. Petrographic Characteristics and Depositional Environment The investigated Middle Eocene limestone rock samples were texturally classified according to [29] into lime-mudstone, wackestone, and grainstone (Table1). The major component, lime-mudstone, shows a high percentage of mud and fine materials, which varied in the range of 43% to 85% with a mean of 63.8% and a standard deviation of 13.64. However, wacketone was represented with a high percentage of grains in the range of 4% to 28% with a mean of 15.1% and a standard deviation of 7.09. The lime-mudstones are argillaceous and made up of shells from 1% to 7%. The matrix contains micrite with fine-grained materials, and secondary fissures are visible as white spots (Figure4a). On the other hand, the wackestone carbonate rocks contained more than 10% calcite grains informed in micritic matrix and the matrix was recrystallized into sparry calcite (Figure4b). The percent of grainstone ranged from 8% to 30% with and the Mean is 18.8%. The grainstone are argillaceous and made up of shells (10–40%) set in a micritic matrix. (Figure4c). Dolomite was presented with a very low percent in fine material matrix, which varied in the range of 0% to 3% with a mean of 2.01 and a standard deviation of 2.01 (Figure4d).

Table 1. Middle Eocene Limestone composition, uniaxial compressive strength (UCS) and Schmidt Rebound Hammer (Rn) values.

Limestone Composition Sample Classiﬁcation UCS Depth Location Rn No. Grains Grains Dol Lacks Mud Name (MPa) <10% >10% (%) (%) S1 20 BH4 7 78 7 8 Mudstone 40.29 31 S2 15 BH2 10 70 0 19 Wackestone 38.55 30 S3 7 BH5 13 65 2 20 Wackestone 37.11 28 S4 12 BH10 16 50 5 28 Wackestone 35.22 26 S5 20 BH15 20 55 2 23 Wackestone 35.00 26 S6 5 BH3 12 60 0 18 Wackestone 36.44 27 S7 2 BH6 10 69 0 19 Wackestone 38.15 30 S8 23 BH7 20 57 2 21 Wackestone 34.26 25 S9 15 BH9 25 45 2 28 grainstone 32.69 25 S10 22 BH5 4 82 1 13 Wackestone 36.25 31 S11 2 BH8 16 50 5 28 Wackestone 35.22 26 S12 16 BH3 10 75 4 9 Mudstone 39.16 32 S13 18 BH14 5 85 0 9 Mudstone 35.66 32 S14 5 BH2 15 68 3 14 Wackestone 37.2 28 S15 4 BH5 26 51 0 23 grainstone 34.66 25 S16 14 BH11 28 47 2 23 grainstone 31.66 26 S17 16 BH3 6 79 0 15 Wackestone 41.55 33 S18 22 BH7 17 68 3 14 Wackestone 36.52 27 S19 27 BH10 23 47 0 30 grainstone 31.50 25 S20 6 BH9 15 65 3 17 Wackestone 36.27 27 S21 9 BH15 5 85 0 9 Mudstone 34.26 32 S22 3 BH13 17 70 6 9 Mudstone 38.82 32 S23 7 BH9 26 49 0 25 Wackestone 34.66 25 S24 12 BH1 7 75 2 16 Wackestone 40.22 31 Mudstone- S25 2 BH1 5 84 1 10 43.22 31 wackestone S26 28 BH15 25 45 3 27 Wackestone 33.52 24 S27 4 BH14 26 51 0 23 Wackestone 34.66 25 S28 6 BH1 8 76 1 15 Wackestone 38.55 30 S29 1 BH7 27 43 0 30 grainstone 29.16 23 S30 12 BH1 9 70 0 21 Wackestone 38.27 29 Mean - - 15.10 63.80 1.8 18.08 - 36.29 28.07 Stdev 7.09 13.64 2.01 (UCS) uniaxial compressive strength and (Rn) Schmidit rebound hammer. Sustainability 2020, 12, x FOR PEER REVIEW 6 of 14 deviation of 7.09. The lime-mudstones are argillaceous and made up of shells from 1% to 7%. The matrix contains micrite with fine-grained materials, and secondary fissures are visible as white spots (Figure 4a). On the other hand, the wackestone carbonate rocks contained more than 10% calcite grains informed in micritic matrix and the matrix was recrystallized into sparry calcite (Figure 4b). Sustainability 2020, 12, x FOR PEER REVIEW 6 of 14 The percent of grainstone ranged from 8% to 30% with and the Mean is 18.8%. The grainstone are argillaceousdeviation and of made 7.09. The up lime of -shellsmudstone (10s% are–40 argillaceous%) set in anda micritic made up matrix. of shells ( fromFigure 1% 4cto ).7 %Dolomite. The was presentedmatrix with contains a very micrite low percent with fine in-grained fine material materials ma, andtrix secondary, which fissur variedes are in visiblethe range as white of 0 spots% to 3% with (Figure 4a). On the other hand, the wackestone carbonate rocks contained more than 10% calcite a mean of 2.01 and a standard deviation of 2.01 (Figure 4d). grainsSustainability informed2020, 12 in, 9710micritic matrix and the matrix was recrystallized into sparry calcite (Figure 74b of). 15 The percent of grainstone ranged from 8% to 30% with and the Mean is 18.8%. The grainstone are argillaceous and made up of shells (10%–40%) set in a micritic matrix. (Figure 4c). Dolomite was presented with a very low percent in fine material matrix, which varied in the range of 0% to 3% with a mean of 2.01 and a standard deviation of 2.01 (Figure 4d).

(a) (b)

Figure 4.FigureFigure Photomicrographs 4. 4. PhotomicrographsPhotomicrographs showing showing showing ( a(a, (b,ab,)b) l)limeime lime-Mudstone--MudstoneMudstone C.N.; C.N.; C.N.; (c ()c ) s(parry sparryc) sparry calcite calcite calcite Wackestone Wackestone Wackestone C.N.; C.N.; C.N.; (d(d) )g grainstonerainstone and and dolomite dolomite crystals crystals in in fine fine-grained-grained ground mass C.N. (for(for all thin thin (d) grainstone and dolomite crystals in fine-grained ground mass C.N. (for all thin sectionssections,, C.N C.N Crossed Crossed Nichols Nichols).). sections, C.N Crossed Nichols). Additionally,Additionally, lime lime-mudstone-mudstone is is the the most most abundant abundant microfacies microfacies type type in in the the Middle Middle Eocene Eocene Additionally,Limestone.Limestone. It It limeshows shows-mudstone a ahigh high percentage percentage is the of of most mud mud up abundant up to to 85 85%% and and microfacies a arare rare presen presence typece of of inshells shells the and and Middle some some Eocene Limestone.skeletalskeletal It showsdebris debris [32]. [a32 high]. The The secondpercentage second microfacies microfacies of mud is wackestone is wackestone,up to 85, while% whileand grains a grains rare are arethepresen themai mainnce component of component shells up and some up to 79%. Wackestone reflects that the sediments in this depositional environment were pointed skeletal todebris 79%. Wackestone[32]. The second reflects microfaciesthat the sediments is wackestone in this depositional, while grains environment are the were mai pointedn component to up moderatelyto moderately agitated agitated water water conditions conditions and and fair fair circulation. circulation. Consequently, Consequently, mudstone mudstone-wackestone-wackestone is to 79%. Wackestone reflects that the sediments in this depositional environment were pointed to mainlyis mainly composed composed of of fine fine to to medium medium grains grains embedded embedded in in fine fine materials materials matrix. matrix. Mudstone Mudstone is is moderatelyrecrystallizedrecrystallized agitated into intowater sparry sparry conditions calcite calcite and and wackestoneand wackestone fair circulation. with with dark dark patches Consequently, patches of iron of iron oxides. oxides. mudstone Furthermore, Furthermore,-wackestone the is mainly depositional composedthe depositional environments of environments fine to were medium weredistinguished distinguished grains by embedded the by studying the studying inof the fine performed of thematerials performed thin matrix.sections. thin sections. ThreeMudstone is recrystallizedtexturalThree texturalinto classes sparry classes were calcitedetected; were detected; and firstly, wackestone firstly, mudstone mudstone waswith wasdeposited dark deposited patches near near the of the shore iron shore underoxides. under quiet quietFurthermore, water, water, the shallow depths, and poor circulation as a result of the fine-grained nature of their sediments [12,14]. depositionalshallow environments depths, and poor were circulation distinguished as a result by of thethe fine studying-grained ofnature the performedof their sediments thin [sections.12,14]. Three TheThe Middle Middle Eoeene Eoeene limestone limestone is is characterized characterized by by a amicritic micritic groundmass, groundmass, fossils fossils,, and and microfractures microfractures,, textural classes were detected; firstly, mudstone was deposited near the shore under quiet water, whichwhich are are filled filled with with calcite calcite crystals. crystals. This This Middle Middle Eocene Eocene unit unit was was apparently apparently deposited deposited in in a a shallowtransgressive, transgressive,depths, and open openpoor sublittoral, sublittoral, circulation warm, warm, as anda and result quiet quiet seaof sea the [21]. [21 ].fine -grained nature of their sediments [12,14]. The Middle Eoeene limestone is characterized by a micritic groundmass, fossils, and microfractures, 4.3. Physical Rock Properties which are filled with calcite crystals. This Middle Eocene unit was apparently deposited in a transgressive,The open index sublittoral, properties of warm, the limestone and samplesquiet sea along [21]. the study site were distinguished. The natural water content ranged from 7.61% to 8.93%. Further, the bulk and dry density were in the range of (2.17–2.19%) and (2.05–2.08%). The specific gravity of the limestone samples ranged from 2.53% to 2.97% (Table2). Consequently, the absorption rate for the limestone samples ranged from 3.07% to 8.71%. The samples that have low water absorption rates and low saturation degrees are, in general, relatively more durable [33]. Sustainability 2020, 12, 9710 8 of 15

Table 2. Index properties of the Middle Eocene limestone samples. Sustainability 2020, 12, x FOR PEER REVIEW 8 of 14 Index Properties Unit Result with wackestone (R2 = 0.822). The Speciﬁcstrength gravity values (Gs) from - the Schmidt 2.53–2.97 hammer ranges between 30 and Water content (Wc) % 7.61–8.93 60 MPa and were classified as lowbulk to medium density (γwet) strengthg/cm according3 2.17–2.19 to [34]. Dry density (γwet) g/cm3 2.05–2.08 Absorption % 3.07–8.71 Table 2. Index properties of the Middle Eocene limestone samples.

4.4. Schmidt Rebound HammerIndex Properties Unit Result Schmidit ReboundSpecific hammer gravity Rn-values (Gs) varied in the- range of 23–332.53 with–2.97 amean of 28 and a standard deviationWater of 3.66 content (Table1). (Wc) Rn-values have a% high positive7.6 correlation1–8.93 with mudstone 2 2 (R = 0.898) and a poorbulk positive density correlation (γwet) with dolomiteg/cm (R 3= 0.020) (Figure2.17–52a,b),.19 while Figure4c,d indicates moderate inverse relationships with grainstone (R2 = 0.747) and a high negative correlation Dry density (γwet) g/cm3 2.05–2.08 with wackestone (R2 = 0.822). The strength values from the Schmidt hammer ranges between 30 and 60 MPa and were classiﬁedAbsorption as low to medium strength according% to [34].3.07–8.71

50 45 40 35 30 25 y = -0.451x + 44.04

20 R² = 0.840 UCS (Mpa) UCS 15 10 5 0 0 5 10 15 20 25 30 Wackestone (%)

(a)

y = 0.242x + 12.86 R² = 0.898

30 Rn values Rn

20 30 50 70 90 Mudstone (%)

(b)

Figure 5. Cont.

(c) Sustainability 2020, 12, x FOR PEER REVIEW 8 of 14 with wackestone (R2 = 0.822). The strength values from the Schmidt hammer ranges between 30 and 60 MPa and were classified as low to medium strength according to [34].

Table 2. Index properties of the Middle Eocene limestone samples.

Index Properties Unit Result Specific gravity (Gs) - 2.53–2.97 Water content (Wc) % 7.61–8.93 bulk density (γwet) g/cm3 2.17–2.19 Dry density (γwet) g/cm3 2.05–2.08 Absorption % 3.07–8.71

50 45 40 35 30 25 y = -0.451x + 44.04

20 R² = 0.840 UCS (Mpa) UCS 15 10 5 0 0 5 10 15 20 25 30 Wackestone (%)

(a)

y = 0.242x + 12.86 R² = 0.898

30 Rn values Rn

20 30 50 70 90 Mudstone (%)

Sustainability 2020, 12, 9710 9 of 15 (b)

Sustainability 2020, 12, x FOR PEER REVIEW 9 of 14

(c)

20 Rn values Rn y = -0.367x + 34.98 R² = 0.747 15

10 5 10 15 20 25 30 35 Grainstone (%)

(d)

Figure 5Figure. Mean 5. SchmidtMean Schmidt Rebound Rebound hammer hammer values values (Rn) withwith percent percent of ( aof) mudstone,(a) mudstone (b) dolomite,, (b) dolomite, (c) (c) wackestone, and (d) grainstone. wackestone, and (d) grainstone. 4.5. Uniaxial Compressive Strength 4.5. Uniaxial TheCompressive UCS for the Strength Middle Eocene Limestone ranges between 29.16 and 43.22 MPa with a mean of 36.29 MPa with a standard deviation of 3.18 (Table2). The collected samples of the Middle The UCS for the Middle Eocene Limestone ranges between 29.16 and 43.22 MPa with a mean of Eocene foundation bedrock were classified according to the engineering classification of [34] as low to 36.29 MPamedium with strength.a standard deviation of 3.18 (Table 2). The collected samples of the Middle Eocene foundation bedrockThe initial were part of classified the curve according tends to be toslightly the engineeringconcave upward classification reflecting the of closing [34] of as low to mediummicrofractures strength. and vugs within the cores (Figure6). The measured strains during this stage for MiddIe TheEocene initial Iimestones part of represent the curve 40% tends of total strains.to be slightlyThe curves concave become steeper upward at higher reflecting strains, and the the closing of sample exceeds the linear elastic limit giving a nonlinear relationship with gradually reduced values of microfractures and vugs within the cores (Figure 6). The measured strains during this stage for deformation up to failure. At the end of the curve, large lateral deformations were also clear, compared MiddIe Eoceneto those Iimestones experienced inrepresent the initial 40% part. of The total UCS strains. shows The a high curves and poor become direct steeper relationship at higher with strains, and the samplemudstone exceeds and dolomite the linear (R2 = 0.918elastic and limit 0.036), giving respectively a nonlinear (Figure relationship7a,b). However, with UCS gradually indicates a reduced values ofhigh deformation negative correlation up to failure. with wackestone At the end and of grainstone the curve, (R2 = large0.840 lateral and 0.722) deformations (Figure7c,d). The were UCS also clear, comparedwas to plotted those withexperienced Rn values in (Figure the initial8). UCS part. can The be determined UCS shows from a Rn;high consequently, and poor direct a positive relationship correlation was estimated between UCS and Rn values. The plots of UCS with Rn indicate a high linear with mudstone and dolomite (R2 = 0.918 and 0.036), respectively (Figure 7a,b). However, UCS indicates a high negative correlation with wackestone and grainstone (R2 = 0.840 and 0.722) (Figure 7c,d). The UCS was plotted with Rn values (Figure 8). UCS can be determined from Rn; consequently, a positive correlation was estimated between UCS and Rn values. The plots of UCS with Rn indicate a high linear relationship (R2 = 0.885); on the whole, results were measured realistically to inspect their confidence on the mineralogical constituents of limestone.

Figure 6. Representative results of uniaxial compressive tests. Sustainability 2020, 12, x FOR PEER REVIEW 9 of 14

20 Rn values Rn y = -0.367x + 34.98 R² = 0.747 15

10 5 10 15 20 25 30 35 Grainstone (%)

(d)

Figure 5. Mean Schmidt Rebound hammer values (Rn) with percent of (a) mudstone, (b) dolomite, (c) wackestone, and (d) grainstone.

4.5. Uniaxial Compressive Strength The UCS for the Middle Eocene Limestone ranges between 29.16 and 43.22 MPa with a mean of 36.29 MPa with a standard deviation of 3.18 (Table 2). The collected samples of the Middle Eocene foundation bedrock were classified according to the engineering classification of [34] as low to medium strength. The initial part of the curve tends to be slightly concave upward reflecting the closing of microfractures and vugs within the cores (Figure 6). The measured strains during this stage for MiddIe Eocene Iimestones represent 40% of total strains. The curves become steeper at higher strains, and the sample exceeds the linear elastic limit giving a nonlinear relationship with gradually reduced values of deformation up to failure. At the end of the curve, large lateral deformations were also clear, compared to those experienced in the initial part. The UCS shows a high and poor direct relationship with mudstone and dolomite (R2 = 0.918 and 0.036), respectively (Figure 7a,b). However, UCS 2 Sustainabilityindicates2020 a ,high12, 9710 negative correlation with wackestone and grainstone (R = 0.840 and 0.722)10 (Figure of 15 7c,d). The UCS was plotted with Rn values (Figure 8). UCS can be determined from Rn; consequently, a positive correlation was estimated between UCS and Rn values. The plots of UCS with Rn indicate 2 relationshipa high linear (R =relationship0.885); on the (R whole,2 = 0.885); results on the were whole, measured results realistically were measured to inspect realistically their conﬁdence to inspect on thetheir mineralogical confidence on constituents the mineralogical of limestone. constituents of limestone.

Sustainability 2020, 12, x FOR PEER REVIEW 10 of 14 FigureFigure 6. Representative 6. Representative results results of uniaxial of uniaxial compressive compressive tests. tests.

50 45 40 35 30 25 y = -0.451x + 44.04

20 R² = 0.840 UCS (Mpa) UCS 15 10 5 0 0 5 10 15 20 25 30 Wackestone (%)

(a)

(b)

Figure 7. Cont.

(c)

UCS (Mpa) UCS 30

25 y = -0.476x + 46.18 R² = 0.722 20 5 10 15 20 25 30 35 Grainstone (%)

(d)

Figure 7. Mean UCS with percent of (a) mudstone, (b) dolomite, (c) wackestone, and (d) grainstone. Sustainability 2020, 12, x FOR PEER REVIEW 10 of 14 Sustainability 2020, 12, x FOR PEER REVIEW 10 of 14

50 4550 4045 3540 3035 2530 y = -0.451x + 44.04 2025 R² = 0.840 UCS (Mpa) UCS y = -0.451x + 44.04

1520 R² = 0.840 UCS (Mpa) UCS 1015 510 0 5 00 5 10 15 20 25 30 0 5 10 15 20 25 30 Wackestone (%) Wackestone (%)

(a) (a)

Sustainability 2020, 12, x FOR PEER REVIEW 11 of 14

5. Discussion The physical properties of the selected samples from the Middle Eocene Limestone foundation bedrock were determined (Table 2). These include bulk density; specific gravity, water content, and Sustainability 2020, 12, 9710 11 of 15 absorption rate. The results of these properties point((bb)) to the fact that water will be unable to make its way into limestone, therefore unable to promote damage in construction model structure [30], which proved that the building material′s surface with a low degree of water absorption and porosity will be little or not affected by weathering agents such as wind or rainfall. Supplementarily, the mechanical properties of the Middle Eocene Limestone foundation bedrock were determined by measuring the uniaxial compressive strength and Rn values. UCS and Rn in a straight line interrelated to mudstone, dolomite contents, and vary inversely with wackestone and grainstone (Figure 4). Additionally, mechanical properties are exposing a plain correlation with limestone constituents, but there are interactions with complementary characteristics. Mudstone has an individual express influence and effect on the mechanical behavior of the limestone (Table 1). The highest UCS of 43.22 MPa related to a maximum mudstone content of 85%. Petrographically, the foundation bedrock was texturally classified according to [29] into lime mudstone, wackestone, and mudstone-wackestone. Consequently, the mudstone is the result of cementation of carbonate muds, which consisted of varying percent of aragonite and calcite. Disbanding of aragonite in the argillaceous limestone provided the carbonate for the lithification and cementation of the limestones. (c) The marls, which already underwent a volume (decreasec) by aragonite decrease, lacked cement and became more compacted [22], which indicated high suitability for any construction. However, grainstone and wackestone50 have had an unhelpful effect on the mechanical properties of the Middle Eocene Limestone. 50 45 Accordingly, the45 lowest UCS (29.16%) value is linked to the highest percentage of grainstone (30%). Furthermore, the40 break-in grain size between mudstone and microspar is related to the 40 mineralogical composition35 of the original Limestone-marl alternations, which are widespread forms

of carbonate rocks [3(Mpa) UCS 355,36]. Limestones in these alternations show asymmetrical structure with the 30

highest carbonate content,(Mpa) UCS a very low degree of compaction, and decrease the mechanical properties 30 of the limestone, which25 leads to unsuitability for constructions.y = -0.476 xOn + 46 the.18 other hand, dolomite content R² = 0.722 individually does not25 20 expose the individual behavior y with = -0.476 mechanicalx + 46.18 properties of the Middle R² = 0.722 Eocene Limestone owing20 5to the lower10 percentage15 of20 it. Further,25 the contrasting30 35 characteristics such as Mudstone + Dolomite5 result in10 a high positive15 Grainstone effect20 on(%) the25 mechanical30 properties35 of the Middle Eocene Limestone. All previous interactions between limestone mineral constituents and mechanical Grainstone (%) parameters exposed moderate to high correlation. These interactions represent an attempt to

construct a relationship and a consequential correlation(d) between these parameters for similar rock FiguretypesFigure in7. Meandifferent 7. Mean UCS locations. UCSwith with percent percent of of(a ()a m) mudstone,udstone(d,) (( bb)) dolomite,dolomite, (c )( wackestone,c) wackestone, and (andd) grainstone. (d) grainstone. Figure 7. Mean UCS with percent of (a) mudstone, (b) dolomite, (c) wackestone, and (d) grainstone.

Figure 8. Relationship between a UCS and Rn values values.. Sustainability 2020, 12, 9710 12 of 15

5. Discussion The physical properties of the selected samples from the Middle Eocene Limestone foundation bedrock were determined (Table2). These include bulk density; specific gravity, water content, and absorption rate. The results of these properties point to the fact that water will be unable to make its way into limestone, therefore unable to promote damage in construction model structure [30], which proved that the building material0s surface with a low degree of water absorption and porosity will be little or not affected by weathering agents such as wind or rainfall. Supplementarily, the mechanical properties of the Middle Eocene Limestone foundation bedrock were determined by measuring the uniaxial compressive strength and Rn values. UCS and Rn in a straight line interrelated to mudstone, dolomite contents, and vary inversely with wackestone and grainstone (Figure4). Additionally, mechanical properties are exposing a plain correlation with limestone constituents, but there are interactions with complementary characteristics. Mudstone has an individual express influence and effect on the mechanical behavior of the limestone (Table1). The highest UCS of 43.22 MPa related to a maximum mudstone content of 85%. Petrographically, the foundation bedrock was texturally classified according to [29] into lime mudstone, wackestone, and mudstone-wackestone. Consequently, the mudstone is the result of cementation of carbonate muds, which consisted of varying percent of aragonite and calcite. Disbanding of aragonite in the argillaceous limestone provided the carbonate for the lithification and cementation of the limestones. The marls, which already underwent a volume decrease by aragonite decrease, lacked cement and became more compacted [22], which indicated high suitability for any construction. However, grainstone and wackestone have had an unhelpful effect on the mechanical properties of the Middle Eocene Limestone. Accordingly, the lowest UCS (29.16%) value is linked to the highest percentage of grainstone (30%). Furthermore, the break-in grain size between mudstone and microspar is related to the mineralogical composition of the original Limestone-marl alternations, which are widespread forms of carbonate rocks [35,36]. Limestones in these alternations show asymmetrical structure with the highest carbonate content, a very low degree of compaction, and decrease the mechanical properties of the limestone, which leads to unsuitability for constructions. On the other hand, dolomite content individually does not expose the individual behavior with mechanical properties of the Middle Eocene Limestone owing to the lower percentage of it. Further, the contrasting characteristics such as Mudstone + Dolomite result in a high positive effect on the mechanical properties of the Middle Eocene Limestone. All previous interactions between limestone mineral constituents and mechanical parameters exposed moderate to high correlation. These interactions represent an attempt to construct a relationship and a consequential correlation between these parameters for similar rock types in different locations.

6. Conclusions This study was carried out to investigate the effect of petrographic characteristics on mechanical properties. Three layers were observed. They were composed of a surface layer that characterizes overburden materials that vary between 0.7 and 3 m. The middle layer is characterized by an argillaceous limestone with thickness ranges between 0.5 to 30 m. The bottom layer is composed of highly argillaceous limestone. The physical properties proved that the building material0s surface has a low degree of water absorption and saturation and is, in general, relatively more durable; the water will be unable to make its way into limestone, therefore unable to promote damage in construction and will be little to not affected by weathering agents such as wind or rainfall. Petrographically, the investigated Middle Eocene limestone rock samples are texturally classified into lime-mudstone, wackestone, and mudstone-wackestone in different proportions with a high percent of Mudstone. Analysis of the mechanical properties of the Middle Eocene foundation bedrock indicates low to medium compressive strength (29.16 to 43.22 MPa). It is mainly composed of white, hard limestone Sustainability 2020, 12, 9710 13 of 15 together with a few thin beds of soft marl. The limestone beds are characterized by a low rate of absorption (3.07–8.71), and low water content indicates more durable, evading further compaction, making it suitable for construction. The UCS shows a high and poor direct relationship with lime-mudstone and dolomite (R2 = 0.918 and 0.036), respectively. Furthermore, it indicates a high negative correlation with wackestone and grainstone (R2 = 0.840 and 0.722) Rn-values have a high positive correlation with mudstone (R2 = 0.898) and a very poor positive correlation with dolomite (R2 = 0.020). Furthermore, it indicates inverse relationships with grainstone (R2 = 0.747) and wackestone (R2 = 0.822). The Schmidit Rebound Hammer values demonstrated a high direct relationship with lime-mudstone and a poor direct relationship with dolomite and a high negative correlation with Wackestone and Grainstone. As a final point, the mineral constituents are considered a major aspect of using them as construction materials as well as the mechanical behavior of limestone. Consequently, petrographic and mechanical properties are dependable for suitability assessment in manufacturing activities.

Author Contributions: Conceptualization, A.E.S. and P.M.; methodology, A.E.S.; software, A.E.S.; validation, A.E.S, P.M., and M.Z.; formal analysis, M.Z.; investigation, A.E.S.; resources, P.M.; data curation, A.E.S.; writing—original draft preparation, A.E.S.; writing—review and editing, M.Z.; visualization, A.E.S.; supervision, P.M.; project administration, M.Z.; funding acquisition, P.M. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Acknowledgments: I am grateful to thank Zagazig Environmental Geophysics Lab (ZEGL) for helping us to perform the laboratory testing. A, El Shinawi would like to express appreciation to Samir Abdeltawab for discussions and valuable great support. Also I would like to thank an anonymous reviewer for suggestions and helpful comments. Thank for the support of project KEGA 059TUKE-4/2019 M-learning tool for intelligent modeling of building site parameters in a mixed reality environment. This work was supported by the Slovak Research and Development Agency under the contract no. APVV-17-0549. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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