Coordenação de Apoio Tecnológico à Micro e Pequena Empresa - CATE Centro de Tecnologia Mineral Ministério da Ciência, Tecnologia e Inovação WEATHERING OF SOAPSTONE THAT COVERS THE “CHRIST REDEEMER” STATUE, RIO DE JANEIRO, BRAZIL Roberto Carlos da Conceição Ribeiro Pesquisador - Eng° Químico Núria Fernández Castro Pesquisadora – Eng° de Minas Rio de Janeiro Julho/2012 CAC -004-00-12 – Contribuição técnica realizada para o Global Stone Congress, realizado em Borba – Portugal, de 16 a 20 de julho de 2012. WEATHERING OF SOAPSTONE THAT COVERS THE “CHRIST REDEEMER” STATUE, RIO DE JANEIRO, BRAZIL 1Ribeiro, R. C.C. & 1Castro, N. F. 1. Coordenação de Apoio Tecnológico a Micro e Pequenas Empresas – CATE, Centro de Tecnologia Mineral – Cetem, Av. Pedro Calmon, 900, Ilha da Cidade Universitária, Rio de Janeiro – RJ, [email protected] e [email protected] Keywords: Christ Redeemer, alterability of rocks, soapstone. Abstract The “Christ Redeemer” monument, built between 1926 and 1931 at the top of the Corcovado Hill, South of the Rio de Janeiro city is one of the New Seven Wonders of the World. However, years of exposure to the environment results in severe damages and loss of parts. It is located at 710 meters above sea level, surrounded by the Tijuca Forest National Park, the world’s largest urban forest, close to the sea and exposed to strong winds, rain, rays and sun, typical of tropical climate. In addition, helicopters and airplanes use to pass by to offer a good view of the monument to the tourists. The statue is made of concrete and covered by a steatite (soapstone) mosaic, chosen by its durability and easy use, and largely used in monuments and buildings of Minas Gerais historical cities. Several restoration works have been undertaken on the monument and many original tesserae of the mosaic had been already replaced by new ones from the same or other quarries. In order to assess the last restoration of the statue, in 2010, this study was done to evaluate the conservation product selected by the restoration technicians and to verify the similarity of the tesserae selected to substitute old pieces. So, several characterization and weathering tests and analyses, colorimetric determinations and some water behavior tests were carried out on new and old tesserae, with and without protective. Even though it should deserve a much deeper study, the need for a quick restoration, as it is the most visited touristic place of Brazil, didn’t allow doing so. However results showed that the soapstone is extremely damaged and many tesserae had to be replaced. It’s believed that wind and water acted as transport means for microorganisms, probably from the forest, which generate acids that deteriorate the soapstone, so it was concluded the real need to protect the monument from water. The conservation product chosen performed successfully in laboratory tests and didn’t alter the color or superficial texture of the soapstone, even in aging tests. Introduction Rocks Restoration The restoration of architectural monuments and art arises from the need to preserve records that mark not only moments in the history of a society, as well as styles of bygone eras, religious beliefs and rituals, therefore, a work of vital importance both within cultural and scientific [1]. Technological Characterization The technological characterization of rocks is done through testing and analysis, whose main objective is to obtain parameters petrographic, chemical, physical and mechanical properties of the material, allowing the characterization of rock for use in the coating of buildings [2]. 1 Monument of Christ Redeemer The monument of Christ Redeemer to fit these previously mentioned aspects, and its construction was suggested in the late nineteenth century by the priest Pedro Maria Boss recommending to Princess Isabel to build such a monument. The statue is covered with a mosaic of soapstone or steatite, in which each piece that composes it is designated as tesserae (Figure 1). Figure 1: Aspect of tesserae. Soap-Stone The soapstone is a metamorphic mafic rock or carbonate source consisting essentially of talc is a mineral of secondary origin, formed by the alteration of magnesium-rich silicate minerals such as olivine-type fosterita, and constitutes almost the entire rock mass. This rock is characterized by not very porous, have silky shine and be greasy to the touch [3]. Objectives The present work aims at characterizing technologically rocks of soapstone covering the Christ the Redeemer, to determine inherent pathologies, check problems imposed by the environment and, from the set of data obtained through laboratory tests, to compare the behavior of the rock face of weathering conditions in its natural state and application of protective water repellent and thus identify the agents that cause the greatest degradation in the monument and thus provide technical support for the restoration and preservation of the monument, making the restoration work is more efficient and lasting. Methodology Sampling The selection of tesserae removed was carried out jointly by the Center of Mineral Technology (Cetem) and representatives of the Institute of Historical and Artistic Heritage (IPHAN). Were taken for laboratory tests nine (9) tesserae sides of North, South, East and West. Colorimetry The evaluation was conducted in standard color tesserae. For the determination of the chromatic pattern was used colorimeter whose brand is Technidyne Color Touch 2 Model ISO. The reading of the result is based on the values represented by the axes a *, b * and L * as shown in Figure 2, 2 where the a * axis indicates the change in color from green to red, blue b * axis and the axis yellow L * white to black. Figure 2: Graphic of colorimetric distribution. Mineralogical Characterization The mineralogical analysis were determined by the powder method using a Bruker equipment of the mark-D4 Endeavor qualitative and interpretations of these mineral phases was performed by comparison with standards contained in the database. Petrographic Characterization The petrographic analysis, according to ABNT. NBR 12.768/92 [4] was performed through the interpretation of thin sections of the original samples, with the aim of observing texture, mineral composition, state microfissural, nature of rock and mineral changes. Physical Indices By this test it was possible to determine the specific mass, dried and saturated, porosity and absorption by means of water according to the formulas specified ABNT. NBR 12.766/92 [5]. In this test the specimens were weighed dry after 24 hours in an oven at 70ºC providing the equivalent of dry weight. Subsequently, they were immersed in distilled water for 24 hours so obtaining the weights saturated and immersed using a precision balance. Alterability Tests a) Salt spray attach This trial aims to reproduce the effects caused by exposure to salt spray so that the bodies are subjected to vapor concentrations of sodium chloride. According to the ABNT. NBR 8094/83 [6], the samples were rinsed with distilled water so that the surface residues were removed, after been dried at an average temperature of 75 ° C and then weighed. Later, the bodies were placed in the chamber of salinity and subjected to 30 cycles, equivalent to 360 hours. Upon completion of test, the samples were immersed in deionized water so that the deposited salts were removed. Then they were again dried and weighed in greenhouses. Finally, we determined the pattern color and have been visual inspection. 3 b) Water Attack According to ABNT. NBR 8095/83 [7], the bodies were initially weighed and had their initial color observed after drying at 70 ° C. The bodies were hung by a nylon thread for 10 cycles within the humidity chamber. With the conclusion of the test bodies were dried, weighed and had their color rechecked. c) SO2 Attack According to the ABNT. NBR 8096/83 [8], the specimens were washed and dried. Then taken to the chamber, whose main feature is to simulate the effect of acid rain, where the SO2 is injected and the atmosphere inside the chamber. After eight hours, the chamber was opened for ventilation 16 hours characterizing the completion of a cycle. Performed a total of 30 cycles totaling 720 hours. At the end, the bodies were washed, dried, weighed and had their color index measured. d) Water repellency The hydrophobic polymers are generally based on silicone which in turn are formed by an inorganic matrix with non-polar radical responsible for water repellency. Therefore, have a surface tension less than water and therefore hydrophobic characteristics [9]. The water exerts an important influence on the characteristics of stone monuments reducing its thermal performance, causing efflorescence and accelerating the growth of microorganisms. Their affinity to the surface of these materials is due to surface tension that varies with the medium in which is in contact and, therefore, the use of resin causes this voltage is reduced. For the tests we used the water repellent brand Wacker-Chemical of Brazil in a 1:9 ratio being 14 days of healing, as was stated by the manufacturer. Results and Discussion Colorimetry The results of the colorimetric assay show that there is a tendency to light yellowish-green coloration, due to the average values for the axes a *, b * and L *, respectively, -0.11 (green), 5.3 (yellow) and 53 (white). Petrographic Characterization The tesserae which looks massive and with a high degree of degradation due to stains, discoloration, dark spots and loss of material causing rounding the edges of tesserae. Under the microscope (Figure 3) shows no microcracks, the average level of change is observed and minerals are: talc, chlorite, calcite, tremolite, actnolita. 4 Figure 3: Photomicrographs of petrographic evaluation. Mineralogical Characterization The mineralogical analysis was evaluated for interpreting the diffractogram as shown in Figure 4, where, in general, the peaks of greater intensity can be represented by the following minerals: talc, tremolite, calcite, chlorite, thus confirming the analysis Petrographic.