Influence of Pore System Characteristics on Limestone
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Environ Geol (2008) 54:1271–1281 DOI 10.1007/s00254-007-0909-1 ORIGINAL PAPER Influence of pore system characteristics on limestone vulnerability: a laboratory study G. Cultrone Æ L. G. Russo Æ C. Calabro` Æ M. Urosˇevicˇ Æ A. Pezzino Received: 30 April 2007 / Accepted: 20 June 2007 / Published online: 12 July 2007 Ó Springer-Verlag 2007 Abstract Hyblean limestone of Oligo-Miocene age was Keywords Limestones Á Pore system Á Crystallization widely used as a construction material in the architectural pressure Á Durability heritage of Eastern Sicily (Italy). Among them, the so- called Pietra Bianca di Melilli (Melilli limestone) and Calcare di Siracusa (Syracuse limestone) were prized for Introduction their attractive appearance, ease of quarrying, and work- ability. Syracuse limestone shows general weathering, Hyblean limestone was the main construction material whereas Melilli limestone is better preserved, and only used in the Architectural Heritage of Eastern Sicily (Ita- differential erosion or superficial exfoliation can be de- ly). All the lithotypes, belonging to various geological tected in monuments. The cause of the different behavior formations, are commercially known as ‘‘Pietra di Sira- of these two limestones was investigated from the petro- cusa’’ (Syracuse stone). This is because, in the past, graphic and petrophysical points of view. The saturation names were not associated with the petrologic features of coefficient is higher in Melilli limestone, and ultrasound the stone, but with the location of quarries. Within the measurements indicate that it is less compact than Syracuse family of Syracuse stone, the Oligo-Miocene limestone of limestone, so that Melilli limestone could deteriorate more the Monti Climiti Formation was extensively used to easily than Syracuse limestone. However, pore intercon- build important artistic monuments in the Syracuse and nections and the size of very small pores play the main role Catania districts, which today suffer from various kinds of in the durability of both materials. The ‘‘irregularity’’ of the deterioration. Syracuse pore system and its greater number of micropores The Monti Climiti Formation is divided into two geo- hinder water flow through the exterior, promote stress in logical members: pore structure, and favor the development of scaling, as 1. Syracuse limestone member, still known as Pietra di confirmed by salt crystallization tests. In Melilli limestone, Siracusa. the low concentration of micropores and fast water evap- 2. Melilli member, also known as Pietra Bianca di oration allow solutions to reach the surface more easily, Melilli (Melilli white stone). resulting in less damaging efflorescence. Syracuse limestone (henceforth SL) has an older origin as a construction material, and was indeed used to build G. Cultrone (&) Á M. Urosˇevicˇ monuments of Greek and Roman age in the city of Syra- Department of Mineralogy and Petrology, cuse. In chronological order, we mention the Temple of University of Granada, Avda, Fuentenueva, 18002 Granada, Spain Apollo (early sixth century BC), the Temple of Athena e-mail: [email protected] (mid-sixth century BC), the Greek Theatre (fifth century BC) and the Castle of Eurialo (402–397 BC). L. G. Russo Á C. Calabro` Á A. Pezzino The ancient quarries from which SL comes are known as Department of Geology, University of Catania, latomie (i.e., stone quarries). There are 12 latomie, all Corso Italia 57, 95100 Catania, Italy located around the city of Syracuse. 123 1272 Environ Geol (2008) 54:1271–1281 After the earthquake of 1693, which destroyed the with restricted fauna (Pectinidae and Cardidae) (Grasso eastern area of Sicily, Melilli limestone (henceforth ML) and Lentini 1982; Yellin-Dror et al. 1997). was quarried to build civic and religious monuments in Melilli (e.g., Mother Church, Church of the Holy Ghost and City Council building), and in Syracuse (e.g., Old Materials and methods Market Palace, Municipal Theatre). The aims of this work are to characterize the limestones Study methods include two steps: of these two geological members from the mineralogical (a) macroscopic observation of the monuments in the and petrophysical points of view, and to identify the causes cities of Syracuse and Melilli to identify lithotypes, to of the different decay in ancient monuments. recognize decay forms, and to establish the degree of deterioration; (b) mineralogical and petrophysical analyses on samples Geological setting collected from quarries. Two historical quarries were selected near Melilli: ‘‘Palombara’’ for Syracuse The Hyblean Plateau is a thick Triassic to Quaternary car- limestone and ‘‘Pirrera di Melilli’’ for Melilli lime- bonate platform in the SE part of Sicily (Grasso 1997), rep- stone. These are the only quarries in the area in which resenting an emerging portion of African continental crust the two lithotypes were excavated in blocks. (Catalano et al. 2000) forced back down under the Appen- nine-Maghrebian thrust belt (Grasso et al. 1982). Two main The mineralogy and texture of limestone samples were fault systems crosscut this plateau: one, extensional trends analyzed under a Zeiss Axiolab polarized optical micro- NE-SW, the other, trending NNW-SSE, mostly consists of scope. Thin sections were prepared and observed with strike-slip faults (Ragg et al. 1999). The Hyblean plateau is parallel and crossed nicols. mainly composed of Oligo-Miocene sedimentary sequences Insoluble limestone residues were studied as follows: (1) belonging to the Ragusa Formation to the west and to the CaCO3 was removed by a dilute sodium acetate–acetic acid Sortino Group (Grasso et al. 1982), which comprises the solution (pH 5) on finely milled samples; (2) insoluble formations of the Monti Climiti, Carlentini and Monte residues were granulometrically divided into sand Carrubba Formations, to the east (Fig. 1). (2 mm<˘<62.5 lm), silt (62.5 lm<˘<4 lm) and clay The Ragusa Formation is divided in two members: (˘<2 lm) fractions using an ALCÒ PK 110 spin-drier; (3) Leonardo and Irminio (Rigo and Barbieri 1959). The the resulting mineralogical composition of the fractions Leonardo Member (Oligocene to Aquitanian in age) con- was determined by powder X-ray diffraction (Siemens D- sists of well-bedded alternating sequences of whitish-gray 5000 XRD), with automatic slit and CuKa radiation. to cream planktonic foraminifera biomicrite with marly Analysis conditions were 0.02° 2h s–1 goniometer speed; 5 planctonic foraminifera biomicrite. The Irminio Member to 45° 2h explored area for ˘>2 lm fraction, and 3 to 35° (Aquitanian-Burdigalian) shows a regular succession be- 2h for ˘<2 lm fraction. The XRD of the clay fraction was tween marl and biomicrite (Pedley 1981). Gradually, sed- performed using oriented aggregates: air-dried (untreated), imentation evolved from the Middle Miocene marl of the solvated for 48 h at 60°C with ethylene glycol (Bruton Tellaro Formation, which is partially heterotopic, to the 1955) and heated for 1 h at 550°C (Moore and Reynolds Tortonian biocalcarenite of the Palazzolo Formation 1989). (Grasso et al. 1979). The parameters associated with water uptake and The Monti Climiti Formation (Upper Oligocene–Lower transport inside limestone pores were determined by hydric Miocene) is composed of two members: the lower, Melilli, tests. Since the degree of mechanical resistance and decay consists of yellowish wackstone with planktonic forami- processes often depend on water circulation inside porous nifera; the higher, Syracuse, comprises white coloured solids (Charola and Lazzarini 1986; Kowalski 1975), these packstones with molluscs, echinoids and sporadic porites tests were important to determine the durability of these (Pedley 1981). limestones. Water absorption (NORMAL 7/81 1981), Basaltic volcanic activity occurred intermittently, with drying (NORMAL 29/88 1988) and capillary uptake (UNI- carbonate depositions, from the late Triassic to the early EN1925 2000) were determined by weighing the samples Pleistocene, in an environment characterized by eustatic (three samples per lithotype) at regular intervals. The and isostatic sea-level fluctuations and active tectonism absorption coefficient, drying index, real and apparent (Carbone and Lentini 1981). Lastly, in the early Messinian, density, saturation coefficient, degree of pore intercon- the area was affected by progressive subsidence and the nectivity, and open porosity were calculated from the deposition of the Monte Carrubba Formation, a limestone values thus obtained. 123 Environ Geol (2008) 54:1271–1281 1273 Fig. 1 Geological map of SE Sicily (from Pedley 1981, modified) Salt crystallization test provided information on the Distributions of pore access size and pore volume were damaging effects of soluble salts that are usually con- determined on a mercury intrusion porosimeter (MIP, tained in water. Among these salts, commonly detected Micromeritics Autopore 9410) with a maximum injection in historical buildings (Price 1996), sodium sulphate pressure of 414 MPa. This apparatus can measure pores which can exist as either the anhydrous phase, thenar- with diameters between 0.003 and 360 lm. Fresh and dite, or the decahydrate mirabilite, is considered one of deteriorated cut limestone chips of about 2 cm3 were oven- the most dangerous because of its strong crystallization dried for 24 hat 110°C and then analyzed. Two MIP pressure in pores and fissures (La Iglesia et al. 1997). measurements per sample were carried out. Following UNI-EN12370 (2001), 15 test cycles of salt Of the techniques