heritage

Article Physical–Mechanical and Mineralogical Properties of Fired Bricks of the Archaeological Site of ,

Hanifi Binici 1 , Fatih Binici 2, Mehmet Akcan 3, Yavuz Yardim 4, Enea Mustafaraj 5 and Marco Corradi 6,7,*

1 Department of Civil Engineering, Ni¸santa¸sıUniversity, 34398 , Turkey; hanifi[email protected] 2 KMS Structure Inspection Company, 46100 Kahramanmara¸s,Turkey; [email protected] 3 Department of Civil Engineering, Kahramanmara¸sSütçü Imam˙ University, 46100 Kahramanmara¸s,Turkey; [email protected] 4 Department of Civil and Environmental Engineering, Edinburgh University, Edinburgh EH9 3FG, UK; [email protected] 5 Department of Civil Engineering, EPOKA University, 1039 Tirana, Albania; [email protected] 6 Department of Mechanical & Construction Engineering, Northumbria University, Newcastle upon Tyne NE1 8ST, UK 7 Department of Engineering, University of Perugia, 06125 Perugia, Italy * Correspondence: [email protected]; Tel.: +44-(0)-191-227-3071

 Received: 11 August 2020; Accepted: 9 September 2020; Published: 10 September 2020 

Abstract: In this study, the physical–mechanical and mineralogical properties of bricks used in historical structures of the site of Harran, Turkey have been investigated. Harran was destroyed by the Mongol army, during the Turkish reconquest campaign around the 1260s. The remains of the buildings and basalt/limestone were recently uncovered almost in their entirety. Several brick samples have been taken from the burial mound, the university, the city walls, the castle, and the great . From the visual analyses, it was noted that the bricks have unique colors such as pottery, desert beige, and canyon. Physical analyses show that the absorption rates of the bricks are between 17.30–38.12%, their densities between 1.33–1.70 g/cm3, and porosities between 8.88–25.31%. For the mechanical analyses, the bending strengths have been found to be between 0.82–1.86 MPa and compressive strengths between 6.69–7.95 MPa. The thin-section images show that the bricks contain calcite, muscovite, and plagioclase quartz and pyroxene minerals.

Keywords: brickwork; mechanical testing; cultural heritage conservation; structural analysis

1. Introduction Conservation, preservation, and restoration of cultural heritage assets and buildings is an emerging topic nowadays. Protection of the heritage created over the thousand-year history of human civilization has become urgent also, considering the increasing numbers of natural and man-made hazards [1–3]. It is a challenging topic and requires a multidisciplinary approach, involving experts of different fields. The implementation of guidelines and procedures was set by the early 20th century, such as Carta del Restauro (Athens Charter for the Restoration of Historic Monuments) [4] in 1931, the Venice Charter [5] in 1964, and in ICOMOS (International Council on Monuments and Sites) concerning research, documentation, and technical support regarding cultural assets [6,7]. The final document of the 1974 UNESCO conference [8] and the European Council guidelines [9] regarding the protection of Architectural Heritage represented a keystone in this area. Recently, new methods and procedures have been developed to study historical constructions by means of visual inspection, in-situ testing,

Heritage 2020, 3, 1018–1034; doi:10.3390/heritage3030055 www.mdpi.com/journal/heritage Heritage 2020, 3 1019 non-destructive techniques, photogrammetry, laser scanning, etc., and very promising and satisfactory results have been obtained [10–27]. Turkey is one of the top few countries in the world in terms of great diversity and vast number of heritage monuments/structures [28,29]. Protection of this heritage is enforced by Turkish law, and several conservation institutes and statutory agencies have been established [30]. However, enacting laws and conservation institutes are not always sufficient to protect historical structures. Active studies based on scientific data need to be made along the legal obligations for protection [31]. Identification of the physical and mechanical parameters of constitutive materials of heritage masonry is an important step for their analysis. Previous studies [32–38] conducted on bricks used in historical structures have shown that the density of bricks used in the Ottoman period in an Anatolian fortress built in the 13–14th centuries is 1.66 g/cm3, their porosity 32.4%, and absorption rate 19.5%. Densities of Ottoman bricks from the 14–15th centuries are determined as 1.7–1.8 g/cm3 and their porosity rates as 33–37% [32]. Weights per unit volume of 13–14th centuries Byzantine period bricks are in the range 1.59–1.85 g/cm3. Their porosity rates are in the range 23–39% and their absorption rates by mass vary in the range 14.4–25.2% [33]. For bricks from the fourth–sixth centuries, from a Serbian archaeological area in Belgrade, the porosity rates of the bricks have been confirmed to be in the range 18.4–19.4% [34]. The bricks of later and longer periods (10–19th centuries) in Toledo, Spain, had water absorption rates in the range 19.0–22.0%, densities in the range 1.60–1.51 g/cm3, and total porosity rates in the range 32.5–43.1% [35]. It was confirmed with various methods that mineral ingredients of the materials also had effects on various properties of the bricks in addition to firing temperature. The water absorption rates of the Roman bricks from the third–fifth centuries in Toledo were found to be in the range 6.7–12.6%, their weight per unit volume in the range 2.0–1.9 g/cm3, and porosities in the range 22.2–25.1% [36]. In a study on the mortars and bricks of the Temple of Serapis in Bergama from the Roman–Byzantine period (seventh century), the porosity rates of the bricks have been found in the range 32–35% and their unit weights in the range 1.6–1.7 g/cm3 [37]. In a study conducted on the bricks of the historical Kutahya Castle, it was found that they had unit weights varying in the range 1.34–1.51 g/cm3, porosity rates in the range 35.9–45.5%, compressive strengths in the range 9.9–13.7 N/mm2, and they had pozzolanic natures [38]. A study has been conducted on 43 different batches of clay bricks by the Turkish Ministry of Development and the Housing General Directorate of Construction Materials Laboratory between 1964 and 1975 [26]. In the compressive strength tests conducted in that study, the average compressive strength was found to be 5.39 MPa; the highest value being 10.29 MPa, and the lowest 2.25 MPa. Clay brick samples were taken from brickyards within Ankara’s provincial borders in accordance with the standards. In some of the compressive strength tests of historical bricks, an average of 1.57–2.65 MPa compressive strength have been determined for 67 different clay bricks. In this study, the aim is to specify the physical–mechanical and mineralogical properties of mortars used in historical structures in the Harran region, namely the university, the city walls, the castle and the great mosque. The final aim will be to set up a scientific source for obtaining suitable bricks for restoration applications to be performed within the region in the light of these data.

2. The Site of Harran Modern Turkey’s Harran is a very old outpost of human civilization, and its masonry structures and infrastructure were constructed, repaired, enlarged, or reduced over a very long period of time. The ancient Harran used to be an important city in the Upper Mesopotamia, whose historical records date back to 5000 BC. In the beginning, it was under the control of Sumerians and , and then, around 2750 BC, the region was conquered by Semites. During the Roman times (first century BC–fifth century AD), Harran, known as Carrhae, was along the border with the Parthian Empire and it was the location of the Battle of Carrhae in 53 BC [39,40], in which the Parthians defeated the Romans under the command of Crassus, who was killed. The city passed under the control of the Eastern Heritage 2019, 3 FOR PEER REVIEW 3

Parthian Empire and it was the location of the Battle of Carrhae in 53 BC [39,40], in which the Parthians defeated the Romans under the command of Crassus, who was killed. The city passed under the control of the Eastern Roman Empire (in that period the city was known as Ἑλληνόπολις or Κάρραι) and, finally, in 750 AD, the Arabs invading the region ended the Byzantine dominance. After the settlement of the Turkish states of Fatimids, Zengids, Ayyubids, and Seljuks [41], the city Heritagewas conquered2020, 3 by the Mongols around the 1260s. In this long period of time, the city flourished 1020and was a major urban agglomerate in the region. The city and its monuments are cited in a large number of old documents and historic records. When the Mongols were expelled in 1270 by the λλην π λι ρραι (inTurkish that period army, the the city city was was known partially as E destroyed:ó o theς or mosque, Kα´ ) the and, city finally, walls in, and 750 thAD,e castle the Arabs were invadinghighly damaged the region by the ended Mongols. the Byzantine dominance. After the settlement of the Turkish states of Fatimids,The most Zengids, impor Ayyubids,tant monuments and Seljuks of the [41 city], the are: city was conquered by the Mongols around the 1260s.Burial In this Mound long period: This of monumenttime, the city which flourished has partiallyand was a survived major urban until agglomerate today is located in the region. in the Thecenter city of and the its historic monuments site of areHarran, cited has in a a large height number of 22 ofm, oldand documents is spread over and historica fairly large records. area. When This themonument Mongols haswere been expelled continually in 1270 by used the from Turkish the army, 3rd century the city was BC untilpartially the destroyed: 13th century the AD.mosque, The themasonry city walls, ruins and it the contains castle werebelong highly to various damaged periods. by the It Mongols. is worth noting that several samples of cuneiformThe most scripts important were f monumentsound here, dating of the cityits construction are: to the Sumerian period. According to a hypothesisBurial Mound:difficult Thisto prove monument at the whichmoment, has partiallythe burial survived mound until should today be isidentified located in with the center a moon of thetemple. historic A sitemoon of Harran, cult ruled has a the height Plains of 22 of m, Harran and is spreadfor several over acenturies, fairly large before area. theThis diffus monumention of hasChristianity been continually and Islam. used More from evidence the 3rd about century this BC monument until the 13th could century be found AD. in The the masonry near future, ruins also it containsconsidering belong that to the various burial periods. mound is It actually is worth an noting active that excavation several samples site [42]. of cuneiform scripts were foundCastle here, dating: The exact its construction date of construction to the Sumerian of this period. masonry According structure to a hypothesis is not known. diffi cult Recently, to prove an atancient the moment, Greek theinscription burial mound was found should near be identifiedthe south- witheast a gate: moon this temple. could A help moon with cult dating ruled the(the PlainsByzantine of Harran period for of severalthe four centuries,th–seventh before century). the di However,ffusion of it Christianity is likely that, and inIslam. the nin Moreth century, evidence the aboutCastle, this after monument the conquest could of bethe found Arabs in (seven the nearth century), future, also was considering enlarged and that restored. the burial According mound isto actuallyprofessor an Ö active nal from excavation Harran site University [42]. [42], this was initially a palace, and it was turned into a castleCastle-like :structure The exact with date ofpolygonal construction towers of this during masonry the turbulent structure isperiods not known. of invasions Recently, of an Mongols ancient Greekand the inscription Crusades was (11 found–13th near centuries). the south-east In fact, gate: the this city could of Harran help with was dating near (the the Byzantine border with period the ofChristian the fourth–seventh state of the century). County However,of Edessa it (today is likely Şanlıurfa that, in thein Turkey). ninth century, According the Castle, to the after historic the conquestrecords, of the the Castle Arabs was (seventh heavily century), damaged was andenlarged almost and destroyed restored. According during the to Mong professorolian Önal invasions from Harran(13th century). University [42], this was initially a palace, and it was turned into a castle-like structure with polygonalThe site towers is in during the process the turbulent of being periods added ofto invasionsUNESCO’s of World Mongols Heritage and the Temporary Crusades (11–13thList [43]. centuries).Recently, excavations In fact, the cityhave of been Harran carried was out near at thethe bordercastle and with nearby the Christian buildings state with of thethe Countysupport ofof Edessathe Turkish (today Ministry ¸Sanlıurfain of Cu Turkey).lture and According Tourism. to The the excavations historic records, carried the out Castle on the was second heavily floor damaged of the andPalace almost revealed destroyed a three during-domed the Mongolian bath: the invasions cold, warm (13th, and century). furnace sections of the bath were completelyThe site uncovered. is in the process Part of of the being Castle added was to recentlyUNESCO’s re-constructed World Heritage using Temporary similar stonework List [43]. Recently,(Figure 1). excavations The archeological have been site carriedof Harran out is at not the yet castle fully and open nearby to public: buildings according with theto professor support ofÖ nalthe [42] Turkish the site Ministry was supposed of Culture to andbe accessible Tourism. at The the excavationsend of 2019, carried but the outCovid on- the19 pandemic second floor has oflikely the Palacedelayed revealed this. a three-domed bath: the cold, warm, and furnace sections of the bath were completelyAccording uncovered. to the Partdetailed of the survey Castle wasby Rice recently [44], re-constructed carried out around using similar 1950, the stonework Castle (Figureis a three1).- Thestory archeological building, with site tens of Harran of rooms. is not The yet masonry fully open material to public: is mainly according cut to stones professor (basalt Önal and [42 limestone] the site wasblocks supposed of varying to be sizes, accessible some of at thethem end over of 2019,a meter but long). the Covid-19 pandemic has likely delayed this.

Figure 1. Harran Castle was partially reconstructed in 2013.

According to the detailed survey by Rice [44], carried out around 1950, the Castle is a three-story building, with tens of rooms. The masonry material is mainly cut stones (basalt and limestone blocks of varying sizes, some of them over a meter long). Heritage 2019, 3 FOR PEER REVIEW 4

Figure 1. Harran Castle was partially reconstructed in 2013. Heritage 2020, 3 1021 City Walls: The exact date of the elliptical walls surrounding Old Harran is not known. Recent excavations (2012–2013) of the Şanlıurfa Museum Directorate, under the consultancy of Professor City Walls: The exact date of the elliptical walls surrounding Old Harran is not known. Recent Mehmet Ö nal [45], carried out excavation works for restoration purposes on the western part of the excavations (2012–2013) of the ¸SanlıurfaMuseum Directorate, under the consultancy of Professor city wall, uncovering the city walls, several brickwork towers, and bastions. In excavations in the Mehmet Önal [45], carried out excavation works for restoration purposes on the western part of the northern part of the Castle, a gallery was discovered on the west side. It is likely that the city wall, uncovering the city walls, several brickwork towers, and bastions. In excavations in the construction of the walls dates back to the Roman–Byzantine period: near the south-east gate, an northern part of the Castle, a gallery was discovered on the west side. It is likely that the construction inscription in ancient Greek was found set in a wall. In 2016, excavations were carried out on the of the walls dates back to the Roman–Byzantine period: near the south-east gate, an inscription in city wall (west of the southern, “Raqqa” Gate), revealing part of the wall and leading to the ancient Greek was found set in a wall. In 2016, excavations were carried out on the city wall (west discovery of a broken statue of a woman with a Syriac inscription and a male relief, both used as of the southern, “Raqqa” Gate), revealing part of the wall and leading to the discovery of a broken spolia in the wall. In the 2014–2016 excavations carried out in the west side of the Castle, a statue of a woman with a Syriac inscription and a male relief, both used as spolia in the wall. In the crenellated corridor belonging to a second defense system adjacent to the wall of the Castle 2014–2016 excavations carried out in the west side of the Castle, a crenellated corridor belonging to (between the polygonal and rectangular towers) was uncovered. a second defense system adjacent to the wall of the Castle (between the polygonal and rectangular Great Mosque: The great mosque is considered the oldest mosque built in as part of towers) was uncovered. the Islamic architecture. This mosque is known as the Paradise Mosque. It is a stone and brickwork Great Mosque: The great mosque is considered the oldest mosque built in Anatolia as part of masonry construction, built by the last Ummayad caliph Mervan II in 744–750. The plan of the the Islamic architecture. This mosque is known as the Paradise Mosque. It is a stone and brickwork building has the dimensions of 104 × 107 m. The mosque was recently unearthed during the masonry construction, built by the last Ummayad caliph Mervan II in 744–750. The plan of the building excavations led by Dr Nurettin Yardimer [45]. These excavations are currently being carried out has the dimensions of 104 107 m. The mosque was recently unearthed during the excavations led by also outside the northern× and western gates. Only small portions of the mosque remain standing Dr Nurettin Yardimer [45]. These excavations are currently being carried out also outside the northern today: the 33.3 m tall , the fountain, the mihrab, and the eastern wall. The masonry and western gates. Only small portions of the mosque remain standing today: the 33.3 m tall minaret, members have gone through several restoration processes. The mosque, which is located at the the fountain, the mihrab, and the eastern wall. The masonry members have gone through several eastern foothill of the burial mound, is also known by the names Cami el-Firdevs and Cuma Camisi restoration processes. The mosque, which is located at the eastern foothill of the burial mound, is also (Friday Mosque). known by the names Cami el-Firdevs and Cuma Camisi (Friday Mosque). A historic copper map of the region is given in Figure 2. It can be noted that the site of Harran, A historic copper map of the region is given in Figure2. It can be noted that the site of Harran, 44 kilometers southeast of Şanlıurfa, is located in a strategic region near the historic and modern 44 km southeast of ¸Sanlıurfa,is located in a strategic region near the historic and modern border with border with Mesopotamia, Syria, and Persia, under the Southeastern Anatolia mountain range. Mesopotamia, Syria, and Persia, under the Southeastern Anatolia mountain range.

Figure 2. The map of the studied region in a historic copper engraving from the 18th century. Heritage 2020, 3 1022 Heritage 2019, 3 FOR PEER REVIEW 5

Figure 2. The map of the studied region in a historic copper engraving from the 18th century. 3. Materials and Methods 3. Materials and Methods 3.1. Materials 3.1. Materials Five brick samples were taken from different historical ruins of the city: the burial mound, the university,Five brick the citysamples walls, were the taken castle from and different the great historical mosque, ruins from of undisturbed the city: the partsburial of m theseound, buildings.the Whileuniversity, extracting the the city brick walls, samples, the castle special and attention the great was mosque, paid not from to spoil undisturbed the unique parts structures of these of the bricksbuildings. and photos While of extracting places from the where brick samples,the samples special were attention taken, and was photos paid not of to the spoil taken the brick unique samples structures of the bricks and photos of places from where the samples were taken, and photos of the were filed. The five selected buildings are shown in Figure3. A detail of a wall of the burial mound is taken brick samples were filed. The five selected buildings are shown in Figure 3. A detail of a wall given in Figure4. of the burial mound is given in Figure 4.

(a) (b)

(c) (d)

(e)

Figure 3. Iconic monuments in the historic city of Harran: (a) burial mound, (b) university, (c) city walls, (d) castle, (e) great mosque. Heritage 2019, 3 FOR PEER REVIEW 6

HeritageFigure2020, 33. Iconic monuments in the historic city of Harran: (a) burial mound, (b) university, (c) city 1023 walls, (d) castle, (e) great mosque.

Figure 4. Brick sample taken from the burialburial moundmound (HBM). 3.2. Methods 3.2. Methods Brick samples were used for testing purposes. In detail, samples were subjected to visual analysis,Brick water samples absorption were used and weight for testing density purposes. measurements, In detail bending, samples and were compressive subjected testing, to visual and mineralogicalanalysis, water analysis. absorption Table and1 shows weight the density test matrix. measurements, The reader bending should and be alerted compressive to the limited testing, experimentaland mineralogical data base analysis. (also considering Table 1 shows that the the test test results matrix. lack The the r statisticaleader should properties) be alerted from whichto the theselimited analyses experimental started. data base (also considering that the test results lack the statistical properties) from which these analyses started. Table 1. Test matrix. Table 1. Test matrix. Location Sample Visual Water Wei Bending Compr. Mineral. Locationof Sample DesignationSample AnalysisVisual AbsorptionWater ghtDensityWei StrengthBending StrengthCompr. AnalysisMineral. of SampleBurial Designation Analysis Absorption ghtDensity Strength Strength Analysis HBM √ √ √ √ √ √ BurialMound HBM √ √ √ √ √ √ MoundUniversity HU √ √ √ √ √ √ UniversCity Wallsity HCWHU √√ √√ √√ √√ √√ √ √ Castle HC √ √ √ √ √ √ City GreatWalls HCW √ √ √ √ √ √ HGM √ √ √ √ √ √ CastleMosque HC √ √ √ √ √ √ Great HGM √ √ √ √ √ √ 3.2.1.Mosque Visual Analyses

3.2.1.In Visual order Analyses to obtain prior information about the properties of the brick samples taken from the historical structures, visual analysis of the brick samples was performed. Initially, inconsistent material on theIn surfaces order to of obtain the brick prior samples information was removed about the by meansproperties of an of air the compressor. brick samples After taken cleaning from their the surfaces,historical brick structures, samples visual were analysis examined of thoroughly. the brick samples It is common was performed. to find natural Initially, fibers inconsistent embedded intomaterial the structureon the surfaces of solid of bricks the brick from samples this period was and removed region. by However, means of this an was air notcompressor. the case inAfter the brickscleaning extracted their surfaces, in Harran: brick there samples were no were natural examined fibers (organic thoroughly. additive) It present is common in the to tested find samples natural (Tablefibers 1embedded). In order tointo determine the structure the original of solid colors bricks of thefrom brick this samples, period and which region. surface However, dusts, the this colors was ofnot the the brick case samplesin the bricks were extra determinedcted in Harran: using a colorimeterthere were no (model natural X-Rite fibers RM200), (organic and additive) the color present codes foundin the tested out were samples specified (Tab byle the1). In corresponding order to determine colors onthe the original color chart.colors of the brick samples, which surface dusts, the colors of the brick samples were determined using a colorimeter (model X-Rite 3.2.2.RM200) Physical, and the Analyses color codes found out were specified by the corresponding colors on the color chart. The test for water absorption is generally a good indication of the freeze/thaw resistance, and it provides important information about the durability of bricks. Water absorption is measured by how 3.2.2. Physical Analyses much a brick increases in weight after it has been soaked in water. In order to determine the water absorptionThe test rates for ofwater the bricksabsorption used atis generally Harran, a a series good of indication laboratory of tests the freeze/thaw were conducted resistance [46]. Initially, and it inconsistentprovides import material,ant information traces of organic about and the durability inorganic materials of bricks. (lime Water mortar, absorption mold, is etc.) measured had been by removedhow much from a brick the brick increases samples in weight via an airafter compressor. it has been Subsequently, soaked in water. the brick In order samples to determine were dried the in anwater oven absorption for 48 h atrates 60 ◦ ofC andthe bricks cooled used in a at desiccator. Harran, a Theseries samples of laboratory were dried tests untilwere theconducted weight gain[46]. remained unchanged. At the end of this procedure, the samples’ dry weights were recorded. Then, Heritage 2019, 3 FOR PEER REVIEW 7

Initially inconsistent material, traces of organic and inorganic materials (lime mortar, mold, etc.) Heritagehad been2020, 3removed from the brick samples via an air compressor. Subsequently, the brick samples1024 were dried in an oven for 48 h at 60 °C and cooled in a desiccator. The samples were dried until the weight gain remained unchanged. At the end of this procedure, the samples’ dry weights were brickrecorded. specimens Then, were brick soaked specimens for 48 were hours soaked in water, for 48 after hours which in water their,water-logged after which their and water underwater-logged weightsand underwater were recorded. weights were recorded. TheThe aim aim of of this this investigation investigation was was also also to to calculate calculate the the density density of of the the bricks bricks used used at at the the site site of of Harran.Harran. ItIt is is well-known well-known that that density density is is an an elementary elementary physical physical property, property, and, and, for for a a homogeneous homogeneous object,object, it it is is defined defined as as the the ratio ratio of of its its mass mass ( m(m)) to to its its volume volume ( V(V).). However, However, due due to to the the amorphous amorphous formform of of the the brick brick samples, samples, apparent apparent density density was was initially initially calculated calculated using using the the results results of of the the water water absorptionabsorption tests tests [ 47[47,48,48],], by by considering considering the the volume volume and and weights weights of of the the brick brick specimens, specimens, in in their their dry dry andand water-impregnated water-impregnated states. states. However,However, pycnometer pycnometer tests tests were were also also conducted conducted in order in order to measure to measure the real the densities real densities of the brickof the samplesbrick samples [49]. Furthermore, [49]. Furthermore, to calculate to calculate the porosity the porosity values values of the of brick the samples,brick samples, compactness compactness was calculatedwas calcula fromted thefrom test the results test results in terms in terms of the of apparent the apparent and the and real the densities real densities [50]. [50]. 3.2.3. Mechanical and Mineralogical Analyses 3.2.3. Mechanical and Mineralogical Analyses Samples were prepared by reducing the bricks to the dimensions of 40 40 160 mm with a Samples were prepared by reducing the bricks to the dimensions of 40× × 40× × 160 mm with a hacksaw. Prepared samples were placed on the testing machine on one of the lateral surfaces upon the hacksaw. Prepared samples were placed on the testing machine on one of the lateral surfaces upon support cylinders in such a way that the longitudinal axis would be normal to the support cylinders the support cylinders in such a way that the longitudinal axis would be normal to the support (Figure5). The load was applied normal to the lateral surface of the prism via the loader cylinder, cylinders (Figure 5). The load was applied normal to the lateral surface of the prism via the loader with its axis normal to the longitudinal axis of the specimen, and the load was increased gradually at cylinder, with its axis normal to the longitudinal axis of the specimen, and the load was increased the rate of (50 10) N/s until the sample was broken [51]. gradually at the± rate of (50 ± 10) N/s until the sample was broken [51].

FigureFigure 5. 5.Bending Bending test test arrangement (units (units in in mm). mm).

TheThe compressive compressive strengths strengths of of the the brick brick samples samples were were determined determined by by measuring measuring the the uniaxial uniaxial compressivecompressive strength, strength, applying applying the the compressive compressive load load on on the the prismatic prismatic samples samples obtained obtained from from the the brokenbroken halves halves of of the the bending bending strength strength test test specimens specimens [52 [52].]. The The bending bending strength strength (s bend(sbend)) was was initially initially calculatedcalculated using: using: 3FsdL0 σbend = 3FL, (1)   2bdsd2 0 bend 2bd 2 (1) where Fsd is the maximum bending load, L0 is the bending, span (100 mm), b and d are the width and height of the brick specimen (40 mm). where Fsd is the maximum bending load, L0 is the bending span (100 mm), b and d are the width and heightAnd of the the compressive brick specimen strength (40 mm). (scompr ): And the compressive strength (scompr): F σ = sc , (2) compr bdF   sc compr bd (2) where Fsc is the maximum compressive load. ,

whereIn thisFsc is analysis, the maximum whichhelps compressive the determination load. of the texture and minerals of brick samples, at first the samplesIn this inanalysis, bulk, which which would helps representthe determination the petrographic of the texture properties and minerals of the material, of brick were samples, dried at for 2 h under 105 5 C after the dusts on them had been brushed away. The dried samples were first the samples ±in bulk◦ , which would represent the petrographic properties of the material, were firstdried let for to absorb 2 h under epoxy 105 polymer ± 5 °C after under the pressure dusts on and them let to had dry. been Then, brushed they were away cut. The in thin dried sections samples in a section-preparation device and were glued with epoxy polymer. After the necessary cutting and thinning processes in the thin-section device, they were polished. The texture of the sample, bounding HeritageHeritage 20192019,,, 33 FORFOR PEERPEER REVIEWREVIEW 88 werewere firstfirst letlet toto absorbabsorb epoxyepoxy polymerpolymer underunder pressurepressure andand letlet toto dry.dry. Then,Then, theythey werewere ccutut inin thinthin sectionssections inin aa sectionsection-preparation--preparation devicedevice andand werewere gluedglued withwith epoxyepoxy polymer.polymer. AfterAfter thethe necessarynecessary cutting and thinning processes in the thin--section device, they were polished. The texture of the cuttingHeritage 2020 and, 3 thinning processes in the thin-section device, they were polished. The texture of 1025 the sample,sample, boundingbounding aggregateaggregate ratios,ratios, boundingbounding aggregaaggregatetete phases,phases, aggregateaggregate types,types, shapesshapes andand sizessizes ininin the the the prepared prepared prepared polished polished polished sections sections sections were were were determined determined determined via via via a a a stereo stereo stereo microscope microscope microscope (single (single (single nicol). nicol). nicol). Later, Later, Later, thesetheseaggregate sectionssections ratios, wentwent bounding throughthrough aggregate thinningthinning phases, andand polishingpolishing aggregate processesprocesses types, shapes soso thatthat and theythey sizes couldcould in the bebe prepared examinedexamined polished underunder thethesections polarizingpolarizing were determinedmmicroscope.icroscope.icroscope. via WorkingWorkingWorking a stereo ononon microscope thethethe sectionsectionsection (singlepreparedpreparedprepared nicol). bybyby thinningthinningthinning Later, these untiluntiluntil sections thethethe thicknessthicknessthickness went through ofofof 303030 μμμ waswasthinning reached,reached, and thethe polishing definitedefinite processes identificationidentification so that ofof theyminerals,minerals, could decomposition,decomposition, be examined under newlynewly the createdcreated polarizing mineralsminerals microscope. andand thethe texturaltexturalWorking propertiesproperties on the section formedformed prepared byby themthem by werewere thinning examinedexamined until byby the usingusing thickness thethe polarizingpolarizing of 30 µ was microscopemicroscope reached, (two(two the definite nicols)nicols) [53][53][53].identification.. of minerals, decomposition, newly created minerals and the textural properties formed by them were examined by using the polarizing microscope (two nicols) [53]. 4.4. Results Results andand DiscussionDiscussion 4. Results and Discussion 4.1.4.1. VisualVisual AnalysesAnalyses 4.1. Visual Analyses TheThe ccolorsolors ofof bondingbonding agentagent andand aggregates,aggregates, quantityquantity andand typetype ofof aggregatesaggregates withinwithin brick,brick, and,and, The colors of bonding agent and aggregates, quantity and type of aggregates within brick, and, ififif present,present,present, organicorganicorganic additivesadditivesadditives withinwithinwithin brickbrickbrick ingredientsingredientsingredients werewerewere determineddetermineddetermined bybyby qualitativequalitative observationsobservations if present, organic additives within brick ingredients were determined by qualitative observations (Tab(Tablelele 2).2). (Table2).

TableTable 2.2. VisualVisual analysesanalyses ofof thethe brickbrick samplessamples... Table 2. Visual analyses of the brick samples. SampleSample ColourColour OrganicOrganic Sample Designation Colour of SampleUsedUsed Used inin in Organic Additives DesignationDesignation ofof SampleSample AdditivesAdditives HBM HBM WallsWalls No No HBM Walls No

HU HU PartitionPartition walls walls No No HU Partition walls No HCW HCW PartitionPartition walls walls No No HCW Partition walls No

HC HCHC PartitionPartitionPartition wallswalls walls NoNo No

HGM Partitions of the mosque No HGM HGM PartitionsPartitions of the of themosque mosque No No

TheThe s specificpecific colors colors of of thethe brick brick samples samples are are close close to to those those of of thethe clays clays contained contained therein. therein. In In The specific colors of the brick samples are close to those of the clays contained therein. In terms termsterms ofof strength,strength, thethe brickbrick samplessamples areare strongstrong enoughenough suchsuch thatthat theythey cannotcannot bebe brokenbroken byby hand.hand. of strength, the brick samples are strong enough such that they cannot be broken by hand. The shapes TheThe sshapeshapes ofof thethe brickbrick samplessamples areare rectangularrectangular andand square.square. RectangularRectangular andand squaresquare shapesshapes enableenable of the brick samples are rectangular and square. Rectangular and square shapes enable easier and easiereasier andand regularregular buildingbuilding ofof walls.walls. regular building of walls. 4.2.4.2. PhysicalPhysical AnalysesAnalyses 4.2. Physical Analyses PhysicalPhysicalPhysical analysesanalyses analyses allowedallowed allowed usus totous determinedetermine to determine thethe waterwater the water absorptionabsorption absorption ratesrates rates byby weightweight by weight andand and byby volume byvolume volume ofof thetheof the brickbrick brick samples.samples. samples. ApartApart Apart fromfrom from thethe the compressivecompressive compressive strstrstrength, strength,ength, itit it isis is wellwell-known well-known--known thatthat that waterwater water absorptionabsorption absorption isis anan importantimportant propertyproperty inin brickworkbrickwork masonry.masonry. masonry. ThisThis This propertyproperty property cancan can affectaffect affect thethe qualityquality ofof thethe brickbrick itselfitself andand the the bond bond bond strength strength strength between between between the the the brick brick brick and and andmortar mortar mortar in masonry in in masonry masonry structures structures structures and can and and result can can in result resultreducing in in reducingreducingits strength its its properties. st strengthrength properties. properties. The authors The The [25 ] authors authors have previously [25] [25] have have conducted previously previously an experimental conducted conducted an an investigation experimental experimental to investigationinvestigationinvestigationassess the physical, tototo assessassessassess mineralogical, thethethe physical,physical,physical, and mineralogicalmineralogicalmineralogical, chemical properties,, andand chemicalchemical of the limepropertiesproperties mortars ofof used thethe limelime in the mortarsmortars monuments usedused inininof thethethe Harran. monumentsmonumentsmonuments The test ofofof results Harran.Harran.Harran. carried TheTheThe testtest outtest onresultsresultsresults the lime carriedcarriedcarried mortar outoutout onon andon thethethe on limelimelime the units mortarmortarmortar (i.e., andand the onon bricks) thethe unitsunits could (i.e.(i.e., be,, thethecritical bricks)bricks) for anycouldcould future bebe criticalcritical conservation forfor anyany measure futurefuture conservationconservation and assessment measuremeasure of the andand structural assessmentassessment safety ofof of thethe the structuralstructural masonry safetysafetystructures ofof thethe of masonry themasonry site of structuresstructures Harran: this ofof couldthethe sitesite highly ofof Harran:Harran: facilitate thisthis the couldcould estimation highlyhighly of facilitatefacilitate the mechanical thethe estimationestimation properties ofof thetheofthe mechanical mechanical brickwork properties properties masonry. Water of of the the absorption brickwork brickwork rates masonry. masonry. by weight W WWaterater and absorption absorption by volume rates rates of the by by samples weight weight are and and given by by volumevolumein Table 3ofof. Figurethethe samplessamples6 shows areare the givengiven tested inin specimenTableTable 3.3. FigureFigure during 66 soaking showsshows thethe in water. testedtested specimenspecimen duringduring soakingsoaking inin water.water.

Heritage 2019, 3 FOR PEER REVIEW 9

Table 3. Water absorption rates by weight and by volume of the samples.

Water Absorption Water Absorption Sample Designation by Weight (%) by Volume (%) HBM 32.35 41.16 HU 25.46 33.35 HCW 17.30 26.64 HC 18.49 25.54 HGM 38.12 45.43

HeritageThe2020 water, 3 absorption rates of the brick samples by weight vary between 17.30% and 38.12%.1026 The lowest water absorption rate by weight was obtained from brick samples taken from the city walls. The highestTable water 3. Waterabsorption absorption rate ratesby weight by weight was and obtained by volume from of br theick samples. samples taken from the great mosque. The water absorption rates by volume of the brick samples vary between 25.54% and 45.43%.Sample Brick Designationsamples taken from Water the Absorption castle have by Weight the lowest (%) water Water Absorptionabsorption byrate Volume by volume. (%) A mortar sampleHBM taken from the great mosque 32.35 has the highest water absorption 41.16 rate by volume. When the water absorptionHU rates of the brick samples 25.46 are evaluated in accordance 33.35with Turkish Standard 704 [54], it is seenHCW that the water absorption 17.30 rates are high. The reason for this 26.64 might be the method HC 18.49 25.54 or the ingredientsHGM used during their production. 38.12 45.43

FigureFigure 6.6. WaterWater absorptionabsorption tests.tests.

TheFurthermore, water absorption the volumes rates of of the the brick brick samples samples have by weightbeen determined vary between via water 17.30% absorption and 38.12%. test Thesince lowest they werewater not absorption prismatic rate in byshape. weight Then, was apparent obtained densities from brick of the samples brick taken samples from have the been city walls.compiled The (Tab highestle 4). water absorption rate by weight was obtained from brick samples taken from the great mosque. The water absorption rates by volume of the brick samples vary between 25.54% and 45.43%. Brick samplesTable 4. The taken apparent from the and castle real densities have the and lowest porosity water values absorption of the brick rate samples. by volume. A mortar sample taken from the great mosque hasApparent the highest density water absorption Real density rate by volume.Porosity When the water Sample Designation absorption rates of the brick samples are evaluated(g/cm³) in accordance(g/cm³) with Turkish(%) Standard 704 [54], it is seen that the waterHBM absorption rates are high.1.27 The reason for1.70 this might be25.31 the method or the ingredients used duringHU their production. 1.31 1.46 10.28 Furthermore, theHCW volumes of the brick samples1.54 have been determined1.69 via water8.88 absorption test since they were not prismaticHC in shape. Then,1.38 apparent densities1.58 of the brick12.65 samples have been compiled (Table4). HGM 1.19 1.33 10.53

Table 4. The apparent and real densities and porosity values of the brick samples. The real densities of the brick samples vary between 1.33–1.70 g/cm3. The brick sample with theSample highest Designation real density valueApparent is the Density one taken (g/cm from3) the Real burial Density mound. (g/cm The3) brick Porositysample (%)with the lowest realHBM density value is the one 1.27taken from the great mosque. 1.70 Real density values 25.31 of the brick samples areHU within the range specified 1.31 by Turkish Standard 1.46 704 (1.20–2.00 g/cm 10.283) [54]. Real densities HCWof the brick samples falling 1.54 within the range specified 1.69 in the Turkish Standard 8.88 indicates that a seriousHC controlled production procedure 1.38 has been used for 1.58 making them. 12.65 HGM 1.19 1.33 10.53

The real densities of the brick samples vary between 1.33–1.70 g/cm3. The brick sample with the highest real density value is the one taken from the burial mound. The brick sample with the lowest real density value is the one taken from the great mosque. Real density values of the brick samples are within the range specified by Turkish Standard 704 (1.20–2.00 g/cm3)[54]. Real densities of the brick samples falling within the range specified in the Turkish Standard indicates that a serious controlled production procedure has been used for making them. Porosity values of the brick samples were calculated using their apparent densities and real densities. During the firing of the bricks, infinite microscopic cracks, cavities, and gaps are formed (pores) [55]. These pores are, especially, effective in the failures of the bricks. In general, when the Heritage 2019, 3 FOR PEER REVIEW 10

Porosity values of the brick samples were calculated using their apparent densities and real Heritagedensities.2020 ,During3 the firing of the bricks, infinite microscopic cracks, cavities, and gaps are formed1027 (pores) [55]. These pores are, especially, effective in the failures of the bricks. In general, when the porosityporosity ofof aa brickbrick goesgoes aboveabove 25%,25%, itsits compressivecompressive strengthstrength graduallygradually decreases.decreases. OneOne ofof thethe mostmost significantsignificant factorsfactors whichwhich aaffectedffected thethe durabilitydurability ofof thethe brickbrick samplessamples isis theirtheir porosity.porosity. SinceSince harmfulharmful liquidsliquids easily penetrate penetrate into into the the brick brickss with with higher higher porosity porosity values, values, their their durability durability decrease decreases.s. The Theporosity porosity values values of the of thebrick brick samples samples vary vary between between 8.88% 8.88% and and 25.31%. 25.31%. The The brick brick sample sample with thethe highesthighest porosityporosity valuevalue isis thethe oneone takentaken fromfrom thethe burialburial mound.mound. The sample with the lowest porosity valuevalue isis thethe oneone takentaken fromfrom the the city city walls. walls. Since Since porosity porosity value value a ffaffectsects the the strength strength and and durability durability of of a brick,a brick, the the porosity porosity must must be kept be below kept below a particular a particular value so value that a so desired that bricka desired quality brick is guaranteed. quality is Asguaranteed. the porosity As values the porosity of the bricksvalues studied of the inbricks this researchstudied arein this low, research that must are be low, the reasonthat must why be these the historicalreason why structures these historical have survived structures to date. have survived to date. CompressiveCompressive strength strength test testss on on the the fired fired brick brick samples samples were were carried carried out to out determine to determine the load the- load-carryingcarrying capacity capacity of bricks, of bricks, together together with with analysis analysis of of the the lime lime mortar mortar [25] [25 ] to to estimate the the compressivecompressive strengthstrength ofof thethe brickworkbrickwork masonry.masonry. Because Turkey is oneone ofof thethe mostmost activeactive seismicseismic regionsregions inin EuropeEurope andand AsiaAsia (Figure(Figure7 7),), itit waswas decideddecided toto measuremeasure thethe bendingbending strengthstrength ofof thethe bricks.bricks. ThisThis mechanicalmechanical propertyproperty couldcould bebe usefuluseful forfor anan estimationestimation ofof thethe tensiletensile andand shearshear strengthsstrengths ofof thethe brickworkbrickwork masonrymasonry usedused atat thethe monumentsmonuments ofof Harran,Harran, thisthis providingproviding interestinginteresting informationinformation aboutabout thethe seismicseismic vulnerabilityvulnerability of of Harran Harran buildings. buildings. Unfortunately, Unfortunately, given given the the high high level level of protectionof protection by theby Turkishthe Turkish authority authority over over the site the ofsite Harran, of Harran, it was it notwas possible not possibl to conducte to conduct more more exhaustive exhaustive or full-scale or full- testingscale testing on the onbrickwork the brickwork masonry. masonry. The bending The and bending compressive and compressive strengths of strengths the brick of samples the brick are givensamples in Tableare given5. in Table 5.

Figure 7. Seismic risk map of Turkey [56], in terms of the ratio between peak ground acceleration Figure 7. Seismic risk map of Turkey [56], in terms of the ratio between peak ground acceleration ag a and g (g = acceleration of gravity), for a probability of exceedance of 10% in 50 years (475 years andg g (g = acceleration of gravity), for a probability of exceedance of 10% in 50 years (475 years return period). return period). Table 5. The bending and compressive strengths of the brick samples. A large amount of information is available about the geology of the region of Harran. This is Bending Strength σ Compressive Strength σ located inSample the basin Designation of the Balikh river. This joins the Euphratesbend at the modern city of Raqqa.compr Figure (MPa) (MPa) 8 shows a geology map of the area of Harran: it can be noted that the rocks of the valley belong to the Quaternary HBMperiod, being the most recently 1.86 laid geologic strata. Based on 7.95 the low seismic risk of HU 1.36 7.18 the area of HarranHCW and its geology, with likely 1.24 a low local amplification over 6.69 a rocky soil, we can conclude that theHC seismic hazard for the site 1.26of Harran is relatively low. However, 7.43 the site deserves a more in-depthHGM analysis, also considering haza 0.82rds from climate change (heavy 7.21 rain falls, flooding, etc.) and their combined effects on the masonry monuments of Harran. A large amount of information is available about the geology of the region of Harran. This is located in the basin of the Balikh river. This joins the Euphrates at the modern city of Raqqa. Figure8 shows a geology map of the area of Harran: it can be noted that the rocks of the valley belong to the Heritage 2019, 3 FOR PEER REVIEW 11

Heritage 2020, 3 1028

Quaternary period, being the most recently laid geologic strata. Based on the low seismic risk of the area of Harran and its geology, with likely a low local amplification over a rocky soil, we can conclude that the seismic hazard for the site of Harran is relatively low. However, the site deserves a more in-depth analysis, also considering hazards from climate change (heavy rain falls, flooding, etc.) and Heritage 2019, 3 FOR PEER REVIEW 11 their combined effects on the masonry monuments of Harran.

Figure 8. Geology of the area of Harran.

Table 5. The bending and compressive strengths of the brick samples.

Bending Strength Compressive Strength Sample Designa- bend compr tion (MPa) (MPa) HBM 1.86 7.95 HU 1.36 7.18 HCW 1.24 6.69 HC 1.26 7.43 HGM Figure 8. Geology0.82 of the area of Harran. 7.21 Figure 8. Geology of the area of Harran. Figure 99 showsshows several brick specimens specimens before before these these were were reduced reduced to to the the standard standard testing testing di- Table 5. The bending and compressive strengths of the brick samples. dimensions.mensions. This This figure figure also also shows shows the the testing testing instrument instrument used used for for both both bending and compression compression tests. The bending strengths σ of the brick samples vary between 0.82 and 1.86 MPa. The brick tests. The bending strengths bend of theBending brick Strengthsamples vary betweenCompressive 0.82 and Strength 1.86 MPa. The brick sample with theSample highest Designa- bending strength is the one taken from the burial mound. The brick sample sample with the highest bending strength is thebend one taken from the burialcompr m ound. The brick sample tion with the lowestlowest bendingbending strengthstrength isis thethe oneone(MPa) takentaken fromfrom thethe greatgreat mosque.mosque.(MPa) HBM 1.86 7.95 HU 1.36 7.18 HCW 1.24 6.69 HC 1.26 7.43 HGM 0.82 7.21

Figure 9 shows several brick specimens before these were reduced to the standard testing di- mensions. This figure also shows the testing instrument used for both bending and compression tests. The bending strengths bend of the brick samples vary between 0.82 and 1.86 MPa. The brick sample with the highest bending strength is the one taken from the burial mound. The brick sample Figure 9. Specimen preparation and instrumentation used for bending and compression tests. with the lowest bending strength is the one taken from the great mosque.

The compressive compressive strengths strengthsσ comprcomprof of the the brick brick samples samples vary vary between between 6.69 6.69 and 7.95and MPa. 7.95 MPa. The brick The samplebrick sample with the with highest the highest compressive compressive strength strength value is value the one is takenthe one from taken the burialfrom the mound. burial Figure mound. 10 showsFigure a10 brick shows specimen a brick before speci beingmen subjectedbefore being to the subjected compressive to the load: compressive the underlying load: brick the debrisunderlying from previousbrick debris tests from clearly previous demonstrate tests thatclearly the demonstrate samples’ failure that mode the samples’was due to failure crumbling mode/pulverization was due to ofcrumbling/pulverization the tile material. This isof a the well-known tile material. failure This mechanism is a well-known that is failure normal mechanism for low-strength, that is n porousormal masonryfor low-strength, materials porous [57]. masonry materials [57].

Figure 9. Specimen preparation and instrumentation used for bending and compression tests.

The compressive strengths compr of the brick samples vary between 6.69 and 7.95 MPa. The brick sample with the highest compressive strength value is the one taken from the burial mound. Figure 10 shows a brick specimen before being subjected to the compressive load: the underlying brick debris from previous tests clearly demonstrate that the samples’ failure mode was due to crumbling/pulverization of the tile material. This is a well-known failure mechanism that is normal for low-strength, porous masonry materials [57].

Heritage 2019, 3 FOR PEER REVIEW 12 Heritage 2020, 3 1029 Heritage 2019, 3 FOR PEER REVIEW 12

Figure 10. Compression test: the crumbling failure mode of brick specimens subjected to a compressiveFigure 10. Compression loading can test: be noted the crumbling. This was failure the consequence mode of brick of specimens the low compressive subjected to astrength compressive and Figure 10. Compression test: the crumbling failure mode of brick specimens subjected to a porosity.loading can be noted. This was the consequence of the low compressive strength and porosity. compressive loading can be noted. This was the consequence of the low compressive strength and porosity. TheThe sample sample with with the the lowest lowest compressive compressive strength strength value value is is the the one one taken taken from from the the c cityity w walls.alls. AccordingAccording to to previous previous studies studies [58], [58], it it is is possible possible to to say say that that the the compressive compressive strength strength values values of of the the The sample with the lowest compressive strength value is the one taken from the city walls. brickbrick samples samples are are very very similar similar and and in in a limited range (6.69 (6.69–7.95–7.95 MPa). This This could could suggest suggest that that the the According to previous studies [58], it is possible to say that the compressive strength values of the HarranHarran monuments, constructed constructed in in di differentfferent periods periods of time, of time, have have been beenmanufactured manufactured using a using similar a brick samples are very similar and in a limited range (6.69–7.95 MPa). This could suggest that the similaror non-time-varying or non-time-varying technology, technology, labor, resources, labor, resources, and environmental and environmental conditions. conditions. This could This strengthen could Harran monuments, constructed in different periods of time, have been manufactured using a strengththe hypothesisen the hypothesis that local skills, that local construction skills, construction materials, andmaterials methods, and were methods passed were down passed from down father similar or non-time-varying technology, labor, resources, and environmental conditions. This could fromto son father for generations to son for in generations family brick in companies, family brick also consideringcompanies, alsothe frequent considering changing the frequent of rulers strengthen the hypothesis that local skills, construction materials, and methods were passed down changing(from Parthians of rulers to (from Romans, Parthians from to Byzantines Romans, from to Arabs, Byzantines and finally to Arabs, to theand Mongolsfinally to andthe Mo Turkish).ngols from father to son for generations in family brick companies, also considering the frequent andThe Turkish). thin-section The images thin-section of the fiveimages brick of samples the five takenbrick fromsamples the historicaltaken from structures the historical are quite structures similar changing of rulers (from Parthians to Romans, from Byzantines to Arabs, and finally to the Mongols areto eachquite other similar (Figure to each 11). other (Figure 11). and Turkish). The thin-section images of the five brick samples taken from the historical structures are quite similar to each other (Figure 11).

FigureFigure 11. 11. DetailDetail of of the the brick brick cross cross-section.-section. Figure 11. Detail of the brick cross-section. InIn order order to scanscan thethe minerals minerals and and the the pores pores in in the the brick brick samples samples more more clearly, clearly, single- single and- two-Nicoland two- Nicolprism prism filters filters were usedwere toused capture to capture the images. the images. There There is an excessiveis an excessive amount amount of calcite of calcite mineral mineral in the In order to scan the minerals and the pores in the brick samples more clearly, single- and two- inHBM the brickHBM sample.brick sample. Also, itAlso, can beit notedcan be that noted it contains that it contains muscovite, muscovite, plagioclase, plagioclase and oxide, and minerals. oxide Nicol prism filters were used to capture the images. There is an excessive amount of calcite mineral minerals.These minerals These mi arenerals bonded are with bonded calcite with (Figure calcite 12 (Fig). Excessiveure 12). Excessive amounts amounts of calcite of mineral calcite mineral are also in the HBM brick sample. Also, it can be noted that it contains muscovite, plagioclase, and oxide arepresent also in present the HU in brickthe HU sample. brick It sample. was also It concludedwas also concluded that it has that a porous it has structure, a porous containing, structure, minerals. These minerals are bonded with calcite (Figure 12). Excessive amounts of calcite mineral are also present in the HU brick sample. It was also concluded that it has a porous structure,

Heritage 2020, 3 1030 Heritage 2019, 3 FOR PEER REVIEW 13 incontaining, addition to in calcite addition minerals, to calcite plagioclase minerals, and plagioclase quartz minerals. and quartz Plenty minerals. of quartz Pl andenty calcite of quartz minerals and arecalcite present minerals in the are HCW present brick in sample,the HCW consisting brick sam ofple, tiny consisting grains. of tiny grains.

Figure 12. 12. PhotoPhoto micro micro graphs graphs of polished of polished thin thin sections sections of the of HH the brick HH sample, brick sample, (a) in cross-polarized (a) in cross- lightpolarized and (lightb) in and plane-polarized (b) in plane- lightpolarized (P: Pore, light Cal: (P: Pore, Calcite). Cal: Calcite).

It couldcould bebe interesting interesting to to compare compare the the brick brick mechanical mechanical properties properties of the of Harranthe Harran monuments monuments with thewith ones the ofones other of sitesother in sites the region.in the region. Because Because most of most these of sites these are sites listed are and listed protected and protected it is very rareit is tovery find rare these to valuesfind these in the values scientific in the literature, scientific given literature, the destructive given the character destructive of these character tests. of Table these6 showstests. Table these 6 data shows for these a limited data number for a limited of sites number located of in sites located and in Turkey. Greece It and can Turkey. be noted It that can the be compressivenoted that strengthsthe compressive of Harran strength bricks ares consistentof Harran with bricks the mechanical are consistent characteristics with the of mechanical the Serapis templecharacteri ofstics of the (secondSerapis temple century), of inPergamon Bergama, (seco Turkey,nd century), and with in the Bergama, ones of Turkey, Ottoman and Ördekli with Bath,the ones Bursa, of Turkey, Ottoman but Ösmaller rdekli compared Bath, Bursa, to the Turkey, compressive but smaller strengths compared of some Roman to the and compressive Byzantine masonrystrengths monumentsof some Roman located and in Byzantine Filippi, Greece. masonry monuments located in Filippi, Greece. On the other hand, the density of Harran bricks seems significantly smaller compared to the Table 6. Comparison of test results on bricks of other sites in Minor, Southern Europe, and density of bricks used in Turkey in historic brickwork constructions. For example, the porosity of Northern Africa. the bricks of the Serapis temple, Pergamon; Agia Sophia, Istanbul; and Ottoman Ö rdekli Bath, Compressive Strength Bursa, are 35, 45, andSite 39%, respectively (Table 5). Harran bricks exhibitedDensity (g/cm a3) porosityPorosity ranging (%) σ (MPa) between 8.88 and 25.31 %, with a mean value of aboutcompr 13% (Table 4). Serapis temple, Pergamon, 2nd century, Bergama, Turkey [59] 6.0 1.65 35 Agia Sophia, Istanbul, Turkey, 6th century [60] - 1.55–1.90 45 OttomanTable Ördekli 6. Comparison Bath, Bursa, Turkey, of test 14th results century [ on61] bricks of other8.9–10.1 sites in Asia Minor, 1.70Southern Europe 38-39.8, and Filippi,Northern Greece, 2nd Africa. century [62] 18.78 1.678 22.02 Galerius Palace, Greece, 4th century [62] 19.80 1.756 15.78 Site of Dion, Greece, 4th century [62] 4.62 1.638 22.38 Site of Palatiano, Greece, 4th centurySite [62] 20.72Compressive 1.69Density Porosity 15.96 Byzantine monuments, Thessaloniki, Greece, 7–11th century [62] 4.5–16.08Strength 1.46–1.84(g/cm³) 16.02–29.8(%) Roman Babylon of Egypt, 4th century, [63] 1.6–9.2 1.4–1.8 17.3–43.2 compr (MPa) Serapis temple, Pergamon, 2nd century, Bergama, 6.0 1.65 35 TurkeyOn the[59] other hand, the density of Harran bricks seems significantly smaller compared to the densityAgia Sophia, of bricks Istanbul, used inTurkey, Turkey 6th in century historic [60] brickwork constructions.- For example,1.55-1.90 the porosity45 of theOttoman bricks ofÖ rdekli the Serapis Bath, temple,Bursa, Turkey, Pergamon; 14th Agia century Sophia, [61] Istanbul;8.9–10.1 and Ottoman1.70 Ördekli Bath,38-39.8 Bursa, areFilippi, 35, 45, Greece, and 39%, 2nd respectivelycentury [62] (Table5). Harran bricks exhibited18.78 a porosity ranging1.678 between22.02 8.88 andGalerius 25.31 %,Palace, with Greece, a mean 4th value century of about [62] 13% (Table4). 19.80 1.756 15.78 Site Byof Dion, comparing Greece, the 4th mechanical century [62] properties of the bricks and the4.62 mortar used1.638 in Harran with22.38 other archeologicalSite of Palatiano, monuments Greece, 4th in thecentury macro-Mediterranean [62] region,20.72 critical information1.69 can be obtained.15.96 ForByzantine example, monuments, conservation interventions successfully implemented4.5–16.08 in other1.46 sites,–1.84 based16.02 on–29.8 their propertyThessaloniki, similarity Greece, with 7– the11th masonry century materials, [62] can be adopted with more confidence. Conservation of archeologicalRoman Babylon monuments of Egypt, requires 4th century, a deep knowledge of structures1.6– and9.2 constituent1.4–1.8 materials, 17.3 of–43.2 their properties,[63] context features and use conditions, and of the possible state of damage and its causes. Prevention and rehabilitation measures can be successfully accomplished only if a proper analysis and diagnosisBy comparing has been the formulated, mechanical so properties that masonry of the heritage bricks buildings and the mortar can be preservedused in Harran as much with as possibleother archeological as historic documents monuments of our in the past. macro-Mediterranean region, critical information can be obtained.For the For Harran example, site, severalconservation questions interventions remain without successfully answers: implemented this relates to in the other sites sites,from where based theon theirinhabitants property of Harran similarity collected with the the raw masonry materials materials, used for can brick be production, adopted with the more technologies confidence. they Conservation of archeological monuments requires a deep knowledge of structures and constituent

Heritage 2020, 3 1031 applied to make and fire the bricks. It could be very interesting to study how far they transported raw resources and final products after furnace treatments, considering that a crucial point was the nearby availability of timber, water, and sandy soils without stones. This paper aims to provide a limited, but significant contribution to these critical issues.

5. Conclusions In this paper the physical–mechanical and mineralogical properties of bricks used in historical masonry structures of the ancient city of Harran were investigated. At the end of the study, the following conclusions can be drawn:

1. The visual analyses of the bricks allowed to describe them based on their colors. Importantly, this is a potential source of cultural and heritage information and can provide useful information about the identity, chronology, technology, labor, resources, and environmental conditions of the site of Harran, in Turkey. 2. The mechanical properties (compressive and bending strengths), porosity, and density of the bricks have been compared with the scarce existing data for other sites in the macro-region (Asia minor, southern Europe, northern Africa). Also taking into account the limited experimental base, it can be concluded that the mechanical properties are consistent with the ones of other sites, even if a large scattering of results was noted from one site to another. It seems that bricks’ mechanical characteristics from Roman times for sites in Greece are higher (18–20 MPa for the compressive strength) compared with the compressive strength of the buildings constructed in the Late Antiquity (3rd–10th century). 3. It is also possible to note that the compressive and bending strength values of the tested brick samples are very similar and in a limited range (6.69–7.95 MPa for compressive strength, and 0.82–1.86 MPa for bending strength). This could suggest that the Harran masonry monuments, constructed in different periods of time, have been manufactured using a similar or a non-time-varying technology, labor, resources, and environmental conditions. This could strengthen the hypothesis that local skills, construction materials, and methods were passed down from father to son for generations in the family brick companies and were not shattered by the destructions and devastation from frequent wars, changing of rulers, natural disasters that affected the area of Harran. 4. The mechanical characterization of the masonry constituent materials (bricks and mortar) of several Harran monuments represents a critical information for future analyses regarding the seismic vulnerability, and the implementation of conservation interventions. 5. The minerals seen in the thin-section images of the bricks are cryptocrystals, quartz, ferro magnesium, calcite, and opaque minerals. It can be said that the ferro magnesium minerals within the bricks provide a binding material support to the bricks by decomposition.

These structures in Harran Area, which were built centuries ago (since 5000 BC), provided great services. These structures are extremely valuable as cultural heritage. Thus, before it is too late, they need to be restored and put under protection. With planned restorations on these structures, by taking into consideration the scientific studies conducted on them, being our cultural heritage, they must be handed on to the coming generations.

Author Contributions: Conceptualization, H.B. and Y.Y.; methodology, F.B. and M.A.; formal analysis, H.B.; writing—original draft preparation, M.C. and E.M.; writing—review and editing, M.C. and Y.Y. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Conflicts of Interest: The authors declare no conflict of interest. Heritage 2020, 3 1032

References

1. Mustafaraj, E. Assessment of Historical Structures, A Case Study of Five Ottoman in Albania; LAP Lambert Academic Publishing: Saarbrucken, , 2014. 2. Borri, A.; Corradi, M. Architectural heritage: A discussion on conservation and safety. Heritage 2019, 2, 41. [CrossRef] 3. Yardım, Y.; Mustafaraj, E. Selected Assessment and Retrofitting Application Techniques for Historical Unreinforced Masonry Buildings. In Handbook of Research on Seismic Assessment and Rehabilitation of Historic Structures; Asteris, P.G., Plevris, V., Eds.; IGI Global: Hershey, PA, USA, 2015; pp. 525–545. 4. Lorusso, S.; Carbonara, G.; Gentile, M.T. Architectural restoration: different conceptions during centuries. Conserv. Sci. Cult. Herit. 2002, 2, 56–83. 5. Venice Charter. International Charter for the Conservation and Restoration of Monuments and Sites; ICOMOS Archnet-IJAR: Venice, Italy, 1964; Volume 12, pp. 334–346. 6. Elia, R.J. ICOMOS adopts archaeological heritage charter: text and commentary. J. Field Archaeol. 1993, 20, 97–104. [CrossRef] 7. ICOMOS–ISCARSAH Committee. ICOMOS Charter—Principles for the analysis, conservation and structural restoration of architectural heritage. In Proceedings of the ICOMOS 14th General Assembly and Scientific Symposium, Victoria Falls, Zimbabwe, 27–31 October 2003. 8. The General Conference of the United Nations Educational, Scientific and Cultural Organization meeting in Paris from 17 October to 21 November 1972, at its seventeenth session. In Proceedings of the Convention for the Protection of the Architectural Heritage of Europe, Granada, Spain, 3 October 1985. 9. Akoz, F.; Yuzer, N. Investigation of Material Properties of Ayasofya Mosque- Sts Sergius and Bacchus-in Istanbul by Using Non-destructive Methods. In Proceedings of the Conference STREMA 95, Structural Studies Repairs and Maintenance of Historical Buildings, Crete, Greece, 4 May 1995; pp. 163–170. 10. Borri, A.; Corradi, M.; Castori, G.; De Maria, A. A method for the analysis and classification of historic masonry. Bull. Earthq. Eng. 2015, 13, 2647–2665. [CrossRef] 11. Mustafaraj, E.; Yardım, Y. Repair and Strengthening of Historical Structures: Naziresha’s Mosque in Elbasan. In Proceedings of the 3rd Annual International Conference on Civil Engineering, Athens, Greece, 10–13 June 2013. 12. Soyluk, A.; Ilerisoy, Z.Y. Dynamic analysis of Dolmabahce masonry clock tower. Gradevinar 2013, 65, 345–352. 13. Betti, M.; Galano, L. Seismic analysis of historic masonry buildings: The Vicarius Palace in Pescia (Italy). Buildings 2012, 2, 63–82. [CrossRef] 14. Lourenço, P.B. Assessment, diagnosis and strengthening of Outerio church, Portugal. Constr. Build. Mater. 2005, 19, 634–645. [CrossRef] 15. Faella, C.; Martinelli, E.; Nigro, E.; Paciello, S. Tuff masonry walls strengthened with a new kind of C-FRP sheet: Experimental tests and analysis. In Proceedings of the 13th World Conference on Earthquake Engineering, Vancouver, BC, Canada, 1–6 August 2004. 16. Yardım, Y.; Mustafaraj, E. Effects of soil settlement and deformed geometry on a historical structure. Nat. Hazards Earth Syst. Sci. 2013, 1, 5911–5934. [CrossRef] 17. Anzoni, A.; Binda, L.; Carpinteri, A.; Invarnizzi, S.; Lacidogna, G. A multilevel approach for the damage assessment of historic masonry towers. J. Cult. Herit. 2009, 11, 459–470. [CrossRef] 18. Van Aarle, M.; Schellen, H.; van Schijndel, J. Hygro thermal simulation to predict the risk of frost damage in masonry; effects of climate change. Energy Procedia 2015, 78, 2536–2541. [CrossRef] 19. Franzoni, E. State-of-the-art on methods for reducing rising damp in masonry. J. Cult. Herit. 2018, 31, S3–S9. [CrossRef] 20. Franzoni, E.; Gentilini, C.; Graziani, G.; Bandini, S. Mechanical properties of fired-clay brick masonry models in moist and dry conditions. Key Eng. Mater. 2014, 624, 307–312. 21. Amde, A.M.; Martin, J.V.; Colville, J. The effects of moisture on compressive strength and modulus of brick masonry. In Proceedings of the 13th International Brick and Block Masonry Conference, Amsterdam, The Netherlands, 4–7 July 2004; p. 15043442. 22. Graubohm, M.; Brameshuber, W. Rehabilitation of Masonry constructions temporarily submerged by Water-influence of Water on the properties of Masonry and Facings, Drying Methods and their Effect. In Proceedings of the 11th Canadian Masonry Symposium, Toronto, ON, Canada, 31 May–3 June 2009. Heritage 2020, 3 1033

23. Smith, B.M. Moisture Problems in Historic Masonry Walls: Diagnosis and Treatment; U.S. Government Printing Office: Washington, DC, USA, 1984. 24. Borri, A.; Castori, G.; Corradi, M. Determination of shear strength of masonry panels through different tests. Int. J. Archit. Herit. 2015, 9, 913–927. [CrossRef] 25. Uranjek, M.; Bosiljkov, B.V. Influence of freeze–thaw cycles on mechanical properties of historical brick masonry. Constr. Build. Mater. 2015, 84, 416–428. [CrossRef] 26. Binici, H.; Akcan, M.; Aksogan, O.; Resatoglu, R. Physico-chemical and mineralogical study of ancient mortars used in Harran area (Turkey). Adv. Concr. Constr. 2017, 5, 639–658. 27. Somuncu, M.; Yi˘git, T. World heritage sites in Turkey: Current status and problems of conservation and management. CBD 2010, 8, 1–26. 28. Corradi, M.; Borri, A. A database of the structural behavior of masonry in shear. Bull. Earthq. Eng. 2018, 16, 3905–3930. [CrossRef] 29. Ertan, T.; Egercioglu, Y. The impact of UNESCO world heritage list on historic urban city centers and its place in urban regeneration: the case of Melaka, Malaysia and Tire, Turkey. Procedia-Soc. Behav. Sci. 2016, 216, 591–602. [CrossRef] 30. Bonini, B.S.; Shoup, D.; Zan, L. Understanding cultural heritage in Turkey: institutional context and organisational issues. Int. J. Herit. Stud. 2013, 19, 728–748. [CrossRef] 31. Garrecht, H. Climatic Problems at Speyer Cathedral-Monitoring as a Contribution to Preservation, RILEM TC 177-MDT. In Proceedings of the Workshop on On-Site Control and Non-Destructive Evaluation of Masonry Structures, Mantova, Italy, 12–14 November 2001. 32. Kurugol, S.; Gulec, A. Physical and Mechanical Properties of Anadolu Hisarı’s Mortars. In Proceedings of the ISSM 08, 8th International Seminar on Structural Masonry, Istanbul, Turkey, 5–7 November 2008; pp. 513–521. 33. Boke, H.; Akkurt, S.; Ipekoglu, B.; Ugurlu, E. Characteristics of brick used as aggregate in historic brick-lime mortars and plasters. Cem. Concr. Res. 2006, 36, 1115–1122. [CrossRef] 34. Radivojevic, A. Investigation of late antique bricks from archaeological sites of contemporary Serbia as a basis of conservation works. Archit. Civ. Eng. 2005, 3, 185–193. [CrossRef] 35. Lopez-Arce, P.; Garcia-Guinea, J.; Garcia, M.; Obis, J. Bricks in historical buildings of Toledo City: characterization and restoration. Mater. Charact. 2003, 50, 59–68. [CrossRef] 36. Lopez-Arce, P.; Garcia-Guinea, J. Weathering traces in ancient bricks from historic buildings. Build. Environ. 2005, 40, 929–941. [CrossRef] 37. Ozkaya, A.O. Properties of Roman Bricks and Mortars Used in Serapis Temple in Bergama. Master’s Thesis, Graduate School of Engineering and Sciences of Izmir Institute of Technology, Izmir, Turkey, 2005. 38. Akoz, F.; Yuzer, N.; Cakır, O.; Kabay, N. Investigation of Material Properties of Dolmabahce Palace Reception (Muayede) Hall’s Dome and Vaults. Stud. Anc. Struct. 2001, 1, 659–668. 39. Sampson, G. Defeat of Rome in the East: Crassus, the Parthians, and the Disastrous Battle of Carrhae, 53 BC; Pen & Sword Military: Barnsley, UK, 2008. 40. Gray, E.W.; Sherwin-White, S.M.; van der Spek, R.J. Carrhae; Oxford Research Encyclopedia of Classics: Oxford, UK, 2015. 41. Freely, J. A History of Ottoman Architecture; WIT Press: Southampton, UK, 2011. 42. Daily Sabah. Available online: https://www.dailysabah.com/history/2018/12/26/magnificent-harran-palace- revealed-through-excavations (accessed on 10 July 2020). 43. Turkey’s Harran Eyes UNESCO Heritage List. Available online: https://www.aa.com.tr/en/culture-and-art/ turkeys-harran-eyes-unesco-heritage-list/1212521#:~{}:text=SANLIURFA%2C%20Turkey,UNESCO\T1\ textquoterights%20tentative%20list%20since%202000 (accessed on 10 July 2020). 44. Rice, D.S. Medieval Harran: Studies on its Topography and Monuments, I. Anatol. Stud. 1952, 2, 36–84. [CrossRef] 45. Turkish Archaeonews. Available online: https://turkisharchaeonews.net/site/harran (accessed on 10 July 2020). 46. Teutonico, J.M. A Laboratory Manual for Architectural Conservators; ICCROM: Rome, Italy, 1988; pp. 113–118. 47. RILEM. Tentative recommendations, comission-25-PEM, Recommended tests to measure the deterioration of stone and to assess the effectiveness of treatment methods. Mater. Struct. 1980, 13, 173–253. Heritage 2020, 3 1034

48. TS EN 1936. Natural Stones Test. Methods: Real Density, Apparent Density, Total and Open Porosity Determination; The Turkish Standards Institute: Ankara, Turkey, 2001. 49. Candeias, A.E.; Nogueira, P.; Mirao, J.; Silva, A.S.; Veiga Casa, M.; Ribeir, I.; Seruy, A.I. Characterization of Ancient Mortars: Present Methodology and Future Perspectives; (Project CATHEDRAL—POCI/HEC/57915/2004); Chairmen the European Research Councils Chemistry Committees: Brussels, Belgium, 2004. 50. Kozlu, H.H. Features of Characterization of Historic Mortars and Repair Mortars in the Kayseri Region. Ph.D. Thesis, Istanbul Technical University, Institute of Science, Istanbul, Turkey, 2010. 51. TS EN 196-1. Cement Strength Tests; Section 1; Turkish Standards Institute: Ankara, Turkey, 2002. 52. Ugurlu, E.; Boke, H. Features of lime mortar and plaster and brick to be used in Khorasan Conservation to be produced. In Proceedings of the 5th National Congress and Exhibition of Building Materials, Istanbul, Turkey, 3–5 November 2020; 2010; Volume 3, pp. 385–396. 53. Pekmezci, I. Cukurova Region (Cilicia) Historical Characterization of Some Mortars Used in Construction and Repair Mortar for Suggestions. Ph.D. Thesis, Istanbul Technical University, Institute of Science, Istanbul, Turkey, 2012. 54. TS 704. Clay Bricks (Wall Tile); Turkish Standards Institution: Ankara, Turkey, 1979. 55. Binici, H.; Arocena, J.; Kapur, S.; Aksogan, O.; Kaplan, H. Microstructure of red brick dust and ground basaltic pumice blended cement mortars exposed to magnesium sulphate solutions. Can. Civ. Eng. J. 2009, 36, 1784–1793. [CrossRef] 56. Turkey Earthquake Risk Map. Available online: https://deprem.afad.gov.tr/deprem-tehlike-haritasi?lang=en (accessed on 10 July 2020). 57. Vasanelli, E.; Colangiuli, D.; Calia, A.; Sbartai, Z.M.; Breysse, D. Combining non-invasive techniques for reliable prediction of soft stone strength in historic masonries. Constr. Build. Mater. 2017, 146, 744–754. [CrossRef] 58. Binici, H.; Arocena, J.; Kapur, S.; Aksogan, O.; Kaplan, H. Investigation of the physico-chemical and microscopic properties of Ottoman mortars from Erzurum (Turkey). Constr. Build. Mater. 2010, 24, 1995–2002. [CrossRef] 59. Ozkaya, O.A.; Boke, H. Properties of Roman bricks and mortars used in Serapis temple in the city of Pergamon. Mater. Charact. 2009, 60, 995–1000. [CrossRef] 60. Moropoulou, A.; Cakmak, A.; Polikreti, K. Provenance and technology investigation of Agia Sophia bricks, Istanbul, Turkey. J. Am. Ceram. Soc. 2002, 85, 366–372. [CrossRef] 61. Ba˘gbancı,M.B.; Özcan, R.; Ba˘gbancı,Ö.K. Characterization of Materials Used in the Fourteenth Century the early Ottoman Ördekli Bath, Bursa, Turkey. Stud. Conserv. 2010, 55, 301–312. [CrossRef] 62. Stefanidou, M.; Papayianni, I.; Pachta, V. Analysis and characterization of Roman and Byzantine fired bricks from Greece. Mater. Struct. 2015, 48, 2251–2260. [CrossRef] 63. Hemeda, S.; Akarish, I.M.; El-Nagga, A.A. Engineering investigations and durability problems of the construction materials of the Roman Babylon of Egypt. Open J. Geol. 2018, 8, 404–436. [CrossRef]

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