14 Structural Studies, Repairs and Maintenance of ...€¦ · SEM OBSERVATIONS: Alteration and/or...

Analysis of existing pathologies in historical

buildings of the Basque Country

C. Romero, M. Zalbide, I. Rodriguez-Maribona

Labien, Technological Research Centre, Cuesta de Olabeaga 16,

Abstract

The main objective of this study has been to assess the degree of stone decay of the historicalbuildings of the province of Vizcaya. For that purpose a comparison between the quarry stone andthe masonry stone has been established, by means of the characterisation of both by laboratorytests.

1 Introduction

The province of Vizcaya has an extension of 217,2 Knr and 1.163.269inhabitants. It limits to the north with the Cantabric Sea, to the west with theprovince of Cantabria, to the East with the province of Guipuzcoa, and to thesouth with the province of Alava.

The climate is rainy for a great part of the year. For the last ten years it hashad an average rainy days of 185 a year, and the mean annual temperature hasbeen 14,5°C.

Concerning air pollution, high concentrations of SO? have been detected atdifferent locations within the Bajo Nervion zone, in the Gran Bilbao area.

The most widely used building stones within this region are cretaceouslimestones and sandstones, being the origin of the formers most commonlyMarkina, Ereno and Manaria. With respect to the sandstones, the commonest arethose from the Duranguesado area.

Historic buildings in Vizcaya are deteriorated due to the environmentalcharacteristics and the external aggressive agents. The response to aggressions aredifferent depending on the types of building stone. However, there is not yet acomprehensive study on this subject.

2 Experimental Method

From the available registered monuments from Vizcaya twelve buildings were

Transactions on the Built Environment vol 26, © 1997 WIT Press, www.witpress.com, ISSN 1743-3509

14 Structural Studies, Repairs and Maintenance of Historical Buildings

originally selected, of which a comprehensive visual inspection of the macroscopicalteration features was carried out. Further on, three of them were selected for adetailed analysis which involved non-destructive testing techniques like: theSchmidt rebound number testing, and extraction of salts from the masonry blocksAdditionally, several samples extracted from the blocks were analysed. Thedifferent analyses carried out were:

- X- ray diffraction.- Petrographical examination of thin section- Scanning electron microscopy

In order to analyse the quarry stone, the source quarries were selectedfollowing proximity criteria, as well ensuring that they belonged to identicalgeological formations.

BUILDING

Sta. Maria Church

Santo TomasApostol Church

Ntra. Senora de laAsuncion Church

LOCATION

Lekeitio

Arratzu

Markina

MATERIAL

Limestone

SandstoneLimestone

Limestone

POSSIBLESOURCE QUARRY

Ereno/Markina

Durango/Ereno

Markina

Several samples were collected from the most representative sandstone andlimestone quarries from Vizcaya, which are summarised as follows:

STONE

Black limestone

Black marble

Grey limestone

Red marble

Sandstone

Sandstone

Sandstone

SOURCE QUARRY

Zubiondo (Ereno)

Altuna (Markina)

Zubiondo (Ereno)

Ereno

Aveleta (Amorebieta)

Lersundi (Durango)

Izarza II (Durango)

SAMPLEN+

1

2

3

4

5

6

7

The following testing programme was carried out:a) Aspect and physical-chemical characterisation:

- Visual inspection.- Moisture content, according with UNE 22172/85- Thin section studies: petrographical analysis- X-ray diffraction- Scanning electron microscopy (SEM)

b) Permeability- Permeability tests were performed on four cubic specimens


Structural Studies, Repairs and Maintenance of Historical Buildings 15

5 cm long for each sample, for the following tests:- Water absorption, in accordance with UNE 22172/85- Capillary suction and bulk density, in accordance with UNE 67031/85.

c) Mechanical strength and strain characteristics- Cylindric specimens, 5 cmin diameter and 15 cm long, were tested, in accordance to thecorresponding standards. The following tests were carried out:- Uniaxial compressive strength, in accordance to UNE22950/90 (part 1), on one specimen for each sample

- Tensional strength, by means of the Brazilian test, according to UNE22950/90 (part 2), on one specimen for each sample.

- Modulus of elasticity and Poisson's coefficient, according to UNE22950/90 (part 3), on two specimens for each sample

3 Results

3.1 Characterization of the quarry stone

3.1.1 Petrological analysis and microstructureSAMPLE 1 - ZUBIONDO QUARRY (ERENO )

GEOLOGICAL UNIT: Urgonian Complex.AGE: Upper Aptiense - Lower AlbienseCOLOUR: Grey and blackGRAIN SIZE: very fineCOMPOSITION: 8% sparitic cement, 61% micritic matrix cement, 28%bioclasts, 2% pelloids, 1% iron oxides within stylolites.TEXTURE: Mud-supported. Low sorting. No visible porosity.CLASSIFICATION. Fossiliferous reef limestone. Floatstone. Biomicrite.FABRIC: There is no preferential orientation of the grains. Numerousfossils. Weathering: There is no evidence of weathering.FRACTURES: It shows many fractures and veins. Dissolution has takenplace due to the action of watery solutions through the fractures withulterior recrystallization of calcite into them.SEM OBSERVATIONS: Homogeneous rock. An isotropic behaviour canbe expected. Crystalline ultraporosity not very interconnected, andtherefore low permeability.

SAMPLE 2 - ALTUNA QUARRY (MARKINA)GEOLOGICAL UNIT: Urgonian Complex.AGE: Upper Aptiense - Lower AlbienseCOLOUR: BlackGRAIN SIZE: Very fineCOMPOSITION: 3% sparitic cement, 2% microsparitic, 15% micriticmatrix cement, 55% bioclasts, 5% pelloids, 3% intraclasts and extraclasts,15% cortoids and 2% ferric oxides in stylolite.TEXTURE: Mud-supported. No visible porosity.



CLASSIFICATION: Fossiliferous reef limestone. Packstone. Biomicrite.FABRIC: Numerous fossils.WEATHERING: There is not evidence of weathering.SEM OBSERVATIONS: Homogeneous rock. Isotropic behaviour.Slightly interconnected crystalline ultraporosity. A certain permeability.

SAMPLE 3 - ZUBIONDO QUARRY (ERENO )GEOLOGICAL UNIT: Urgonian Complex.AGE: Upper Aptiense - Lower AlbienseCOLOUR: Grey on surface and dark grey in fresh fracture.GRAIN SIZE: FineCOMPOSITION: 4% sparitic cement, 55% micritic matrix cement, 38%bioclasts, 2% pelloids, 1% iron oxides in stylolites.TEXTURE: Mud-supported. Massive. There are a lot of fossils. No visibleporosity.CLASSIFICATION: Floatstone. Biomicrite. Reef limestone.WEATHERING: Small fractures and bioclasts with iron oxides residues.FRACTURES: Many cracks and fissures filled with calcite due todissolution and ulterior recrystallization.SEM OBSERVATIONS: Low porosity. High isotropy.

SAMPLE 4 - ABANDONED QUARRY ( ERENO )GEOLOGICAL UNIT: Urgonian Complex.AGE: Upper Aptiense - Lower AlbienseCOLOUR: Dark red.GRAIN SIZE: Very fineCOMPOSITION. 8% sparitic cement, 62% micritic matrix cement, 26%bioclasts, 1% quartz, 0,5% chlorite and small micas, 2% ferric oxides instylolites.TEXTURE: Mud-supported. Crystalline texture.CLASSIFICATION: Red marble. Floatstone. Biomicrite.FABRIC: There is no preferential orientation of the grains. There are a lotof fossils.WEATHERING: In some zones of the sample, iron oxides can be foundreplacing fossils.FRACTURES: It shows many fractures and veins. Evidence of dissolutionof the carbonate. Some fossils have been substituted by grey limestone.SEM OBSERVATIONS: Homogeneous rock. Relatively high porosity.

SAMPLE 5 - AVELETA QUARRY (AMOREBIETA)GEOLOGICAL UNIT: Supraurgonian Complex.AGE. Upper Albiense - Lower CenomanienseCOLOUR: Brown and ochre.GRAIN SIZE: Very gross.COMPOSITION: 99,16% quartz, 0,1% feldspars, 0,74% rock fragments.TEXTURE: Massive and earthy. It is possible to see small grains of quartz.No visible porosity.CLASSIFICATION: Quartziarenite.



WEATHERING: There is not evidence of weathering nor alteration.SEM OBSERVATIONS: Low porosity (<1%) due to the precipitation ofcement. Lightly compacted.

SAMPLE 6 - LERSUNDI QUARRY (DURANGO )GEOLOGICAL UNIT: Supraurgonian Complex.AGE: Upper Albiense - Lower CenomanienseCOLOUR: Light brown and grey.GRAIN SIZE: Gross.COMPOSITION: 73,82% quartz, 19,04% feldspars, 7,14% rockfragments.TEXTURE: Massive and earthy. Small grains of micas visible to the nakedeye.CLASSIFICATION: Feldspatic grauwacke.WEATHERING: There is no evidence of weathering nor alteration.SEM OBSERVATIONS: Alteration and/or dissolution of the grains ofpotassic feldspar. High intergranular porosity due to dissolution. Mediumcompactness.

SAMPLE 7 - IZARZAII QUARRY (DURANGO )GEOLOGICAL UNIT: Supraurgonian Complex.AGE: Upper Albiense - Lower CenomanienseCOLOUR: Light brown and grey.GRAIN SIZE: Gross.COMPOSITION: 87,14% quartz, 8,58% feldspars, 4,28% rock fragments.TEXTURE: Massive and earthy. Visible small grains of micas.CLASSIFICATION: Feldspatic grauwacke.WEATHERING: Neither weathering nor alteration.SEM OBSERVATIONS: Alteration and/or dissolution of the grains ofpotassic feldspar. Low porosity (1%). Medium compactness.

3.1.2 Mechanical characteristicsThe results obtained from the mechanical tests carried out are summarised in thefollowing Table, where:

- D, Density (g/nf) Sample 1: U. limestone- A, Absorption (%) Sample 2: U. limestone- SC, Suction (x 10*) Sample 3:U. limestone- UCS, Uniaxial compressive strength (MPa) Sample 4: U. limestone- ME, Modulus of elasticity (MPa x 10*) Sample 5: SU. sandstone- PC, Poisson's coefficient Sample 6: SU sandstone- BT, Brazilian test. Tensile strength (MPa) Sample 7: SU. sandstone

U: UrgonianSU : Supraurgonian



SAMPLE N

1

2

3

4

5

6

7

»

2706

26,87

26,86

-

22,44

22,84

21,27

A

0,12

016

0.24

-

156

3.71

5.25

SC

2,51

0.74

114

-

36

23

67

ucs

67,1

81.6

11,7

66.7

28.1

59.5

40

ME

45,7

691

74.2

579

7.6

7.1

-

PC

0,25

0.31

0.30

0.20

016

013

-

BT

1094

1231

1116

645

588

728

-

3.2 Characterisation of the masonry blocks

3.2.1 Visual inspectiona) Sta Maria de Lekeitio

LOCATION

Village,besides theport.Founded onsand. Mainaxe: East-West

POLLUTION

Local roadadjacent to thechurch. Gasstation veryclose.

RESTORATION

In the s.XIX, twoaisles weredemolished and thecorridor around thePresbytery and thearcade were built.In the eighties, theinside was cleanedand painted.

PATHOLOGIES

Heavy erosions,socketing and lossof section insandstones.Dampness bycapillarity in lowercourses. Patinasand deposits ofsalt.Fissures in centralvault and lateralchapels.Colonization bymosses, lichensand plants.



b) Nuestra Sra de la Asuncion - Markina

LOCATION

Village at thebottom of avalley.

POLLUTION

There is a carpark andvarious localroads

RESTORATION

Some repairworks werecarried out on theroof.Project for the belltower.

PATHOLOGIES

Sandstone: loss ofmaterial in sculpturesand importantsocketing in ashlars.Dampness, patinasand deposits of salt.Colonization bymosses, lichens andplants.

c) Santo Tomas Apostol - Arratzu

LOCATION

Small villageon a hill, 5km fromGernika.

POLLUTION

There are nosources ofpollution.

RESTORATION

Restoration of thearcades.

PATHOLOGIES

Vertical fissures onwalls.Dampness, depositsof salt andcolonization bymosses and lichens.The stucco is dampand swollen.

3.2.2 Petrological analysis and microstructureSAMPLE 3 - Santa Maria de Lekeitio

GEOLOGICAL UNIT: Urgonian ComplexAGE: Upper Aptiense- Lower to Middle AlbienseCOMPOSITION: 10 % sparitic cement, 60 % micritic matrix cement, 2%microsparite, 26% bioclasts, 2% cortoids, 0.x % iron oxides in styloliteTEXTURE: Mud-supported. Not visible porosityCLASSIFICATION: Feldspatic grauwacke.WEATHERING: There is no evidence of weathering nor alteration.SEM OBSERVATIONS: Carbonate rock, micrite, well cemented,isotropic. In spite of being compact, it can be susceptible to be dissolveddue to its calcitic composition.

SAMPLE 4 - Santa Maria de LekeitioGEOLOGICAL UNIT: Urgonian ComplexAGE: Upper Aptiense- Lower to Middle AlbienseCOMPOSITION: 8 % sparitic cement, 24 % micritic matrix cement, 3%microsparite, 64% bioclasts, 1% cortoids, 0.x % iron oxides in stylolites



TEXTURE, mud-supported. Not visible porosityCLASSIFICATION: Boundstone. BiomicriteWEATHERING: There is no evidence of weathering nor alteration.SEM OBSERVATIONS: Carbonate rock , micrite, well cemented,isotropic. Very compacted. Microcrystalline porosity <3%. In spite ofbeing a compact rock, it can be susceptible to be dissolved due to itspredominant calcitic composition.

This sample is very similar to the quarry samples n° 1 and 3.Efflorescences (Sta Maria de Lekeitio): A quick and expansive growth of the

salty sediments has taken place in the form of carbonated efflorescences which areintegrated of impermeable layers. A rapid precipitation and occlusion of theoriginal pores of the rock has been generated, with the associated ventilatingproblems for the material.

SAMPLE 8 - Nuestra Senora de La Asuncion. MarkinaGEOLOGICAL UNIT: Urgonian ComplexAGE: Upper Aptiense- Lower to middle AlbienseCOMPOSITION: 4% sparitic cement, 2% microsparite, 69% micriticmatrix cement, 23% bioclasts, 1% cortoids, 1% small crystals of ironoxides, 0.1%iron oxides within styloliteTEXTURE: Mud supported. Porosity cannot be appreciated.CLASSIFICATION: Wackestone- Floatstone. BiomicriteWEATHERING: There is no evidence of weathering nor alteration.SEM OBSERVATIONS: Very fine grain carbonate rock, not very porous,isotropic. Evidence of dissolution, biologic colonizations. The high contentof calcite makes it extremely susceptible to dissolution processes,reprecipitation and organic colonization.

Efflorescences (Nuestra Sra. de La Asuncion, Markina): Calciticefflorescences, integrated by impermeable layers, with predominance of nodularevaporitic textures. A rapid precipitation and occlusion of the original pores of therock has been generated, with the associated ventilating problems for the material.

SAMPLE 5 - Sto. Tomas ArratzuGEOLOGICAL UNIT: ?AGE: ?COMPOSITION: Q: 76.57 %, Fd: 0.11%, Fr: 23.32 %COLOUR: reddish ochreTEXTURE: Zones with loose skeleton, surrounded by clayey matrixCLASSIFICATION: SublithareniteWEATHERING: There is no evidence of weathering nor alteration.SEM OBSERVATIONS: Medium to gross Iron sandstone,homogeneously cemented by iron oxides. Very low porosity. Susceptibleto oxidising superficial processes, with disintegration of the siliciclasticskeleton.SAMPLE 7 - Sto. Tomas ArratzuGEOLOGICAL UNIT: ?AGE: ?



COMPOSITION: Q: 90.01 %, Fd: 4.43 %, Fr: 5.56 %COLOUR: Ochre

TEXTURE: Sutured contacts between grains. Good sorting, Roundedgrains

CLASSIFICATION: SubarcoseWEATHERING: There is no evidence of weathering nor alteration.SEM OBSERVATIONS: Quartz rich rock, with minority unstablecomponents. Practical absence of porosity. Syntaxial cementation andstrong saturation. Precipitation of matrix and degree of compaction rendera very strong material.

3.2.3 Mechanical characterizationIn order to determine the Uniaxiai Compressive Strength of the matrix rockwhich forms the masonry rocks, non-destructive testing with the Schmidthammer, according to the ISRM recommendations, was carried out. The resultsobtained are summarised in the following Table:

LOCATION

Sta. Maria deLekeitio

Nuestra Sra. de LaAsuncion Markina

Sto. Tomas ApostolArratzu

MATERIAL

U. Limestone

SU. Sandstone

U. Limestone

U.Limestone

Sandstone

U.C.S(MPa)

2000

800

1800

1020

630

DESCRIPTION**

STRONG ROCK

STRONG ROCK

MODERATELYSTRONG ROCK

MODERATELYSTRONG ROCK

* The indicated values of Uniaxiai Compressive Strength correspond to themean values. They have been obtained through their calibration curves. Themeasurement have been made horizontally, perpendicular to the surface of theashlars. A density of 27 KN/nf has been assumed for the limestones and 22 KN/nffor the sandstones.

** according to ISRM U: Urgonian SU:Supraurgonian

4. Conclusions

The most commonly used building materials in the Basque country are urgonianlimestones and supraurgonian sandstones. Concerning their mechanical properties,the sandstones have lower densities, and exhibit absorption and suction indexes tentimes greater than those of the limestones, due to their higher porosity. The



unconfined compressive strength of the formers is slightly lower, because of theirminor degree of compaction. However, supraurgonian sandstones are lessdeformable than urgonian limestone, because they are mostly made of quartz, andtheir tensile strength is approximately half of limestones, due to the fact that theircohesive elements are less effective. The good geomechanical properties of bothmaterials, in general, are mainly owed to a well interlaced texture.

The urgonian limestones which have been studied show low permeabilitiesand are very homogeneous, therefore isotropic. These materials are, in general,little porous and hardly weathered, their most outstanding alteration being thedevelopment of salt crusts on their surfaces.

The supraurgonian sandstones studied present a remarkable porosity (up to3.5%) and are slightly compacted, i.e. scarcely consolidated, which renders aneasily removable matrix and, therefore, a rock which is highly susceptible to bemechanically disintegrated on its surface.

The results obtained with the Schmidt Hammer Test on the masonry blocksproved to be rather unreliable.

The church of Sta.Maria de Lekeitio, located at the seaside, is made out ofurgonian limestone, which is a low permeable but highly soluble rock. It exhibitsextensive salt crusts developed on its surface, due to the exposure to a highlyaggressive environment (high concentrations of salts, wind, etc).This results in thecrystallisation of salts on the surface of the building, and in a greater mechanicalattack by the wind and water. Additionally, the fact that the church is locatedadjacent to a local road and a gas station, and that many cars park at two of itssides, results in an increase of contaminants levels. The SO? accelerates thedeterioration processes, depending on the temperature and on the humidity. TheSO, is a pollutant derived from SC , which disintegrates the limestone,producing mechanical stresses and fractures. Moreover, the foundations of thebuilding on sand result in a highly potentially capillary base, a fact which willcertainly enhance the water absorption and alteration at the base of its masonryblocks.

The church of Nuestra Senora de la Asuncion, at Markina, made out ofsimilar urgonian limestone than mentioned above, is located at the bottom of avalley, which means that it is at a point of concentration of drainage nets, a factthat would trigger or enhance the pathologies associated to humidity. The presenceof a car park opposite to its main entrance results in higher concentrations ofcontaminants, thus the importance of the efflorescences at this location.Additionally, the high content of calcite results in extreme susceptibility todissolution, reprecipitation and organic colonization processes.

The church of Sto. Tomas Apostol, made out of supraurgonian sandstone,at Arratzu, is immersed in a less aggressive environment. However, it exhibitsseveral pathologies which are related to the local humidity and to an environmentwhich is highly favourable for the development of vegetation and organic life ingeneral. The zones of loose weft surrounded by clayey matrix as observed throughthe microscope, verified by observation with SEM, explain the rock susceptibilityto superficial oxidation, with disintegration of its siliciclastic skeleton.



References

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2. Esbert, R.M., Ordaz, J., Alonso, F.J., Ruiz de Argandona, V.G.,Montoto, M., Marcos, R. & Valdeon, L. Petrophysicalcharacterization and weatherability of the stones of the SevilleCathedral, Materiales de Construccion, 1988, 38, 5-23

3. Kolaiti, E & Papadopoulos, Z. Evaluation of Schmidt ReboundHammer Testing: A critical approach, Bulletin of the InternationalAssociation of Engineering Geology, 1993, 48, 69-76

4. Lewin, Susceptibility of masonry decay through crystallization ofsalts, Conservation of Historic Stone Buildings and Monuments.National Academy of Sciences, 1981.

5. ISRM, Rock characterization testing and monitoring, ISRMsuggested methods, Pergamon Press, 1981.

6. AENOR, UNE, Mechanical properties of rocks. Strengthdetermination tests. Parts I, 2 and 3, 1990

7. Adams, A.E.; Mackenzie, W.S. & Guilford, C. Atlas of sedimentaryrocks under the Microscope, Longman. Harlow, 1984.

8. Pettijohn, F.J.; Potter, P.E. & Siever, R. Sand and sandstone, SpringerVerlag, New York, 1987.

9. Scholle, P.A. A Colour Illustrated Guide to Carbonate RockConstituents, Textures, Cements and Porosities, AmericanAssociation of Petroleum Geologists, Memoir 27, Tulsa, 1978.

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