Red coloured plaster mortars and a masonry mortar sample dated from 5th c. BC to 3rd c.
BC were collected from Aiani’s archaeological site, northern Greece. The mineralogical
composition of the bulk mortars and the mortar surfaces were determined by μRaman
spectroscopy and X-Ray Diffraction (XRD) techniques. Calcite, quartz, feldspars, dolomite, Tioxides
(anatase/rutile) and clay minerals consisted the mortar samples. Serpentine, a mineral
characteristic for its local provenance was found, which is related to the ophiolithic complex and
the ultramafic rocks of the surrounding area. The red colour of the mortar surfaces is attributable
to hematite, the raw material being iron oxides and hydroxides either from an ochre deposit or
an iron-rich clay deposit. Black inclusions identified by Raman spectroscopy may be associated
with carbonaceous material of an amorphous character and iron oxides and hydroxides
(hematite/goethite). The presence of micaceous and clay minerals, corroborates the origin of the
raw material from local Fe-rich clays

Guinea, Javier Garcia

Iordanidis, Andreas

Epoka University

2nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.1010Mineralogical study of different mortar types from historical monuments ofnorthern GreeceAndreas Iordanidis1, Javier Garcia-Guinea21 Department of Geotechnology and Environmental Engineering, Technological Educational Institute (TEI) ofWestern Macedonia, Kila, 50100 Kozani, Greece2 Museo Nacional Ciencias Naturales, CSIC, C/ José Gutierrez Abascal 2, Madrid 28006, SpainABSTRACTRed coloured plaster mortars and a masonry mortar sample dated from 5th c. BC to 3rd c.BC were collected from Aiani’s archaeological site, northern Greece. The mineralogicalcomposition of the bulk mortars and the mortar surfaces were determined by μRamanspectroscopy and X-Ray Diffraction (XRD) techniques. Calcite, quartz, feldspars, dolomite, Ti-oxides (anatase/rutile) and clay minerals consisted the mortar samples. Serpentine, a mineralcharacteristic for its local provenance was found, which is related to the ophiolithic complex andthe ultramafic rocks of the surrounding area. The red colour of the mortar surfaces is attributableto hematite, the raw material being iron oxides and hydroxides either from an ochre deposit oran iron-rich clay deposit. Black inclusions identified by Raman spectroscopy may be associatedwith carbonaceous material of an amorphous character and iron oxides and hydroxides(hematite/goethite). The presence of micaceous and clay minerals, corroborates the origin of theraw material from local Fe-rich clays.INTRODUCTIONMortars are composite materials, composed of hydraulic or aerial binding material or amixture of binding materials, aggregates and additives [1-3]. Different kinds of mortars exist:masonry mortars between bricks or stones, mortars as wall finishing materials internally orexternally, mortars as foundations for flooring, rubble mortars for the infillings of walls etc. [4].The chemical, mineralogical and structural characterisation of ancient mortars can shed light tothe provenance of raw materials and the production processes, but can also help to matchmaterials from currently accessible sources in the process of renovation or reconstruction of thebuildings [5].The employment of interdisciplinary chemical, geological and physical analyticaltechniques in the study of archaeological artefacts, such as mortars, is a common practicenowadays. Several analytical methods, both destructive and non-destructive, have been used forthe qualitative and quantitative characterisation of ancient mortars, like SEM/EDX, FTIR,DSC/TGA/DTA, microprobe, optical microscopy, XRD, XRF etc. [1, 6-9]. Amongst them, awell established analytical technique used for the analysis of art objects through a nondestructive approach is Raman spectroscopy, which has been widely used in the last decades[10,11].In the present study, the investigation of various types (plaster and masonry) of mortars,collected from the ancient city of Aiani and dated back to archaic/classical (6th c. BC) andhellenistic (3rd c. BC) times is attempted. The study is focused on the mico-molecular and2nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.1011mineralogical characteristics, in an attempt to investigate the raw material used and thetechnology applied for these types of mortars.SAMPLING AND ANALYTICAL METHODOLOGYThree characteristic mortar samples were collected from different places within thearchaeological site of Aiani, northern Greece. K5 sample, a red-coloured plaster mortar, wascollected from the afore-mentioned cistern. K9, another red-coloured plaster mortar sample wascollected from one large public building known as Large Blocks (Megaloi Domoi). Finally, K15sample, a cream-coloured masonry mortar, was collected from the royal cemetery (in particularfrom Tomb A, the largest built tomb found). All samples are dated back to archaic/classical andhellenistic periods [12]. The macroscopic views (both surfaces and cross sections) of thesesamples are shown in Figure 1.X-Ray Diffraction (XRD) was employed for the semi-quantitative mineral identificationof the coloured surfaces and the bulk mortar samples. Samples were carefully placedhorizontally on a special self-made holder, so as to analyse non-destructively the colouredsurfaces of the mortars. Moreover, ground aliquots were used for the bulk mortar analyses. APhilips PW-1710 powder diffractometer with CuKα radiation was used. Patterns were obtainedby step scanning from 3o to 63o 2θ, with a goniometer speed of 0.03o/sec, operating at 30kV and10 mA. The XPOWDER analytical software was used for the semi-quantitative determination ofthe mineral phases.The Raman spectroscopic study was carried out with a Thermo Scientific DXR RamanMicroscope. Several experiments were conducted on the surfaces of the mortar samples,applying different power values, laser beams, bleaching time, number of exposures and exposuretime, in order to obtain the optimum analytical parameters. The average spectral resolution in theRaman shift range of 100-3000 cm-1 was 5 cm-1 (grating 400 lines/mm, spot size 2μm). Ramanimages were obtained using the 20X objective of the con-focal microscope. A 780 nm laserbeam was used, and the power value of the of the sample irradiation was 12 mW. Otheranalytical parameters were as follows: 30sec bleaching time; 5 exposures of 10 sec exposuretime. Under the Raman microscope the mortar surfaces could be clearly seen and the area oftheir spectra could be precisely determined.2nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.1012Figure 1. Macroscopic views of the external surfaces and the cross-sections of the plastermortar samples collected from the cistern (K5) and a building (K9) and a masonry mortarcollected from a tomb (K15) from Aiani archaeological site, ancient Upper Macedonia, northernGreece.Table 1. Semi-quantitative mineralogical composition, using non-destructive X-Ray Diffractionfor the mortar surfaces and powder XRD for the bulk samples of the three ancient mortars (K5,K9 and K15) analysed in this study.Surface BulkK5 K9 K15 K5 K9 K15Quartz (%)SiO228.6 0.5 24.9 36.7 10.0 23.7Calcite (%)CaCO337.1 16.5 59.6 43.8 44.7 61.1Feldspars (%)(K,Na,Ca)AlSi3O827.0 - 10.9 13.0 4.0 8.8Dolomite (%)CaMg(CO3)26.0 68.8 3.6 - 36.1 -Hematite (%)Fe2O3- 6.5 - - - -Kaolinite (%)Al2Si2O5(OH)4- 6.2 - - - -Illite(%)(K,H3O)(Al,Mg,Fe)2(Si,Al)4O10(OH)2,(H2O)- - - 3.0 1.0 2.0Serpentine (%)Mg3Si2O5(OH)4- - - 3.0 3.0 4.0Amorphous (%) 1.3 1 0.9 0.5 1.2 0.42nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.1013RESULTS AND DISCUSSIONThe mineralogical composition of both the bulk mortar samples and their outer surfacesis shown in Table 1. The main identified minerals in the bulk samples are quartz [SiO2],feldspars [(K,Na,Ca)AlSi3O8], calcite [CaCO3], dolomite [CaMg(CO3)2] and illite[(K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)]. The semi-quantitative results for the bulkmortars are: K5 (36.7% quartz, 43.8% calcite, 13% feldspars, 3% serpentinite and 3% illite,), K9(10% quartz, 44.7% calcite, 36.1% dolomite, 4% feldspars, 3% serpentine and 1% illite), K15(23.7% quartz, 61.1% calcite, 8.8% feldspars, 4% serpentine and 2% illite). Calcite, quartz andfeldspars are the most abundant minerals in all mortars with minor differentiations in theirpercentages in each sample. It is evident that these mortars were prepared by crushing localcalcareous sedimentary rocks. Secondary calcite may occur due to post-burial depositionalprocesses [13]. During post-burial period, Mg-rich waters could also have replaced Ca andproduced dolomite along with calcite. The presence of white colour magnesite deposits in thesurrounding area of Aiani is a clear evidence for the magnesium abundance [14,15]. The non-destructive application of XRD technique on the mortar surfaces revealed the followingmineralogical composition: Calcite is the most common mineral found in all samples (withconcentrations ranging from 16.5 to 59.6 %), while quartz and feldspars are present mainly inK5 and K15 samples. Hematite (with a content of 6.5%) comprised the red-coloured surface ofK9 sample, while the other red-coloured mortar K5 did not show the presence of Fe-richminerals. The high contents of iron in K9 sample may also be related to the presence of iron notonly in the pictorial but also to the outer preparation layer, as evidenced in the macroscopicimages of Figure 1. The absence of hematite on the XRD results from the K5 red-colouredmortar sample does not necessarily show that it does not exist, since hematite in low quantities(<1%) is adequate for giving a red hue on the ceramics. Phyllosilicate minerals (e.g. (kaolinite)are also present in the K9 mortar sample and might be related to the use of local clays [13, 15-17]. The presence of Mg-rich dolomite minerals in high amounts (68.8 %) is found in onesample (K9) and could be related to the local Mg-rich deposits found in the surrounding area [9,17] and may be attributed either to a dolomitic lime binder, obtained by the calcinations ofdolomitic limestone or to secondary carbonates, due to post-burial depositional processes.  Itshould be noted that some minor mineral phases might not have been identified and the XRDresults could not directly be correlated with the results of the other analytical methodologies,since it was not always the same surface area analyzed.Table 2. Raman peaks assignment (refer to Figure 2) to specific minerals from the surfaces ofthe three ancient mortars (K5, K9 and K15) analysed in this study.2nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.1014SAMPLE ID Peaks (cm-1) Mineral assignmentK5 227,294,411,502,614,697,13261088HematiteCalciteK5 black inclusion 228,274,487,618,383,548,6941407,1498,1588HematiteGoethiteCarbon blackK9 145227,294,412,498,6141087Anatase/RutileHematiteCalciteK15 white 157,283,714,1088 CalciteK15 grey 158,287,714,1088397,621509CalciteSerpentineFeldsparThe Raman spectra of all the analysed mortar surfaces along with characteristic micrographs ofthe red-coloured surfaces of K5 and K9 samples and the cream-coloured surface of K15 sampleusing the Raman microscope are shown in Figure 2. The identified mineral phases are alsopresented in Table 2, indicating the characteristic Raman peaks of each mineral. The red-coloured mortar surface of K5 sample seems to be composed of different proportions of hematiteand calcite mineral phases. Hematite reveals its main peaks at 227, 294, 411, 502, 614 and 1326cm-1 and calcite is clearly inferred from the 1088 cm-1 Raman peak. A black-coloured inclusionis observed on the surface of K5 sample. This black coloured inclusion is comprised of hematite(228, 274, 487, 618 cm-1) and goethite (383, 548, 694 cm-1). Raman peaks at 1407, 1498 and1588 cm-1 are probably attributable to black carbon present in the inclusion. Most probably, redclays rich in iron oxide and hydroxides were carefully mixed with a proper amount of Ca (andoccasionally Mg) rich carbonates and organic carbon of plant origin and coat the outer surface ofthe mortars. The other red-coloured mortar surface2nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.101522729441150261469710881326 0 20 40 60 80 100 120 140 160 180 200 220 240Int 500 1000 1500 2000 2500Raman shift (cm-1)228274383487548618694140714981588-5 0 5 10 15 20 25 30 35 40 45 50 55 60 65Int 500 1000 1500 2000 2500Raman shift (cm-1)1452272944124986141087-0 50 100 150 200 250 300 350 400Int 500 1000 1500 2000 2500Raman shift (cm-1)1572837141088-0 50 100 150 200 250 300 350 400 450 500Int 500 1000 1500 2000 2500Raman shift (cm-1)1582873975096217147358178419671088-0 50 100 150 200 250 300 350 400 450 500 550Int 500 1000 1500 2000 2500Raman shift (cm-1)K5K5 BLACK INCLUSIONK9K15 GREYK15 WHITEAnHeHeHeHeHeHeCaCaCaCaCaCaCaCaCaCaHeHeHeGoGoCHeHeHeHeFdSeSeGoFigure 2. Raman spectra and microphotographs of the red pigments from K5 and K9 samplesand the white and grey surface material of K15 mortar sample. (Laser wavelength 780 nm,objective 20X). Labels: He=hematite, Go=goethite, Fd=feldspar, Ca=calcite, An= anatase,C=black carbon, Se=serpentine.2nd International Balkans Conference on Challenges of Civil Engineering, BCCCE, 23-25 May 2013, Epoka University, Tirana, Albania.1016(K9) has shown a Raman peak at 145 cm-1, which is attributed to the vibrational modes of theTi-oxides (rutile or anatase), being present as an ancillary component of silicates [18]. Hematiteis also present with its characteristic peaks at 227, 294, 412, 498, 614 cm-1 and calcite with itsmain Raman band at 1087 cm-1 [19-21]. Based on these results, a mixture of ironoxides/hydroxides is proposed for the manufacture of the red coloured plaster. It could beassumed that the different colours are attributed to different percentages of the same minerals.Two hues were evident on the cream-coloured K15 mortar surface, a grey one and a white one.Calcite was prominent by its Raman bands at 157, 283, 714 and 1088 cm-1 for the white hue.The grey hue seems to be composed of various minerals. Calcite is the predominant, as shownby its bands at 158, 287, 714 and 1088 cm-1. The bands at 397 and 621 cm-1 are probablyattributed to serpentine [22, 23] and the one at 509 cm-1 to feldspars.CONCLUSIONSTwo ancient plaster mortars and one masonry mortar from Aiani’s archaeological site, northernGreece were comprehensively analysed in this study, using complementary methodologies. Theconcluding remarks are as follows: The bulk mortar samples are composed of calcite, quartz,feldspar and dolomite. Provenance characteristic minerals, such as serpentine has also beendetermined and is attributable to the ultramafic rocks of the surrounding area. The Ramanspectra of all the red-coloured mortar surfaces revealed hematite as the main constituent. Blackinclusions identified by Raman spectroscopy may be associated with carbonaceous material ofan amorphous character and iron oxides and hydroxides (hematite/goethite). The raw materialfor the red painting derives probably from iron oxides and hydroxides either from a local ochredeposit or an iron-rich clay deposit. The presence of mica and clay minerals is consistent with aprovenance of local Fe-rich clays.REFERENCES[1] Moropoulou A, Bakolas A, Bisbikou K. (2000) Investigation of the technology ofhistoric mortars. Journal of Cultural Heritage, 1, 45-58.[2] Moropoulou A, Bakolas A, Anagnostopoulou S. (2005) Composite materials in ancientstructures. Cement and Concrete Composites, 27, 295-300.[3] Velosa AL, Coroado J, Veiga MR, Rocha F. 2(006) Characterisation of roman mortarsfrom Conimbriga with respect to their repair. Materials Characterization, 58, 1208-1216.[4] Elsen J. 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Mineralogical study of different mortar types from historical monuments of northern Greece

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Mineralogical study of different mortar types from historical monuments of northern Greece

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