Surface modification of a granite building stone in central Rio de Janeiro

Abstract

In order to evaluate environmental controls on the soiling formation and decay of building stones a set of mapping and physical and chemical analyses were carried out on granite from a historical church in the polluted centre of Rio de Janeiro. These techniques highlight the increasing of threatening damage on generally perceived as a durable building material, caused by granular disaggregation and contour scaling in areas close to ground level. Mapping also indicated the formation of black crusts over entire building façades, concentrated on areas sheltered from rain-wash. Analyses demonstrated the influence of marine aerosols, rock and mortar composition and mostly of the atmospheric pollutants on the decay and soiling of the granite. Much of the decay is associated specifi cally with the presence of halite (NaCl) and gypsum (CaS0 4 .2H 2 O). The fact that black, gypsum crusts are able to develop over entire façades in a humid subtropical environment is testimony to the high levels of local pollution, especially particulate deposition. Reduced rainwash, in sheltered micro-environments of narrow, canyon-like streets, overcomes the gypsum tendency to be washed away from buildings façades. These observations further highlight that decay processes are primarily controlled by microclimatic conditions.

Analytical Investigations of Disintegrated Granite Surface from the Un-finished Obelisk in Aswan

“…Consequently, it could be argued that the fi nal red weathering crusts and their related deterioration forms and micro-fi ssures are essentially direct results of heavy external stress and internal strains dominating between all mineralogical components of granite particularly quartz and feldspar grains (Baptista, 2006), (fi g. 5-c). Within the same context, diff erent chemical analytical techniques, qualitative and quantitative, represented in (fi g. 6 and 7) proved that these crusts brown or red resulted from aggressive deterioration factors dominating in the study area through oxidation, kaolinization and rusting mechanisms, in addition to other chemical changes.…”

Phenyl 3,5-di-tert-butyl-2-hydroxybenzoate

“…The structure is closely related to that of the unsubstituted 2-hydroxybenzoic acid phenyl ester (Baptista, 1966;Bilgram et al 1982;Hammond et al, 2002), where the carboxylate group is almost coplanar to the phenyl ring where is attached (C-C-O-C less than 2° deviated from 180°) and the benzoate phenyl almost perpendicular to the carboxylate (C-O-C-C 75.8° and -100.5°).…”

“…For similar molecules, see: Baptista (1966); Bilgram et al (1982); Hammond et al (2002). Table 1 Hydrogen-bond geometry (Å , ).…”

Degradação de gnaisse e granito em fachadas de edifícios históricos no centro do Rio de Janeiro

“…No exterior dos edi� cios, o impacto dos gases ambientais, par� culas liberadas pela combustão de combus� veis fósseis e de organismos biológicos aéreos leva à formação de crostas negras e outros efeitos esté� cos indesejáveis, podendo também comprometer a integridade dos materiais (Esbert et al, 2001;Moropoulou et al, 2001;Bonazza et al, 2005;Sanjurjo Sánchez et al, 2009;Xu et al, 2010). A formação de crostas de intemperismo em pedras naturais em áreas urbanas é considerada fator importante na decomposição das pedras (Amoroso & Fassina, 1983;Török, 2003, Bap� sta Neto et al, 2006. Durante a decomposição de um edi� cio de pedra, além das caracterís�cas intrínsecas do próprio material de construção (composição química e mineralógica, propriedades petro� sicas etc.…”