Prediction of the mechanical behavior of the Oporto granite using data mining techniques

The determination of mechanical properties of granitic rocks has a great importance to solve many engineering problems. Tunnelling, mining and excavations are some examples of these problems. The purpose of this paper is to apply Data Mining (DM) techniques such as multiple regressions (MR), artificial neural networks (ANN) and support vector machines (SVM), to predict the uniaxial compressive strength and the deformation modulus of the Oporto granite. This rock is a light grey, two-mica, medium-grained, hypidiomorphic granite and is located in Oporto (Portugal) and surrounding areas. Begonha (1997) and Begonha et al. (2002) studied this granite in terms of chemical, mineralogical, physical and mechanical properties. Among other things, like the weathering features, those authors applied correlation analysis to investigate the relationships between two properties either physical or mechanical or physical and mechanical. This study took the data published by those authors to build a database containing 55 rock sample records. Each record contains the free porosity (N48), the dry bulk density (d), the ultrasonic velocity (v), the uniaxial compressive strength (σc) and the modulus of elasticity (E). It was concluded that all the models obtained from DM techniques have good performances. Nevertheless, the best forecasting capacity was obtained with the SVM model with N48 and v as input parameters.Fundação para a Ciência e a Tecnologia (FCT

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

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 specifically with the presence of halite (NaCl) and gypsum (CaS04.2H2O). 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 bewashed away from buildings façades. These observations further highlight that decay processes are primarily controlled by microclimatic conditions.<br>Com o objetivo de se avaliar os controles ambientais na formação de crostas e deterioração de rochas ornamentais em fachadas de prédios históricos, uma série de mapeamentos e análises fisicas e químicas foram realizados em granitos da fachada de uma igreja histórica numa área poluída no centro da cidade do Rio de Janeiro. Estas técnicas destacam a ameaça crescente dos danos causados pela desagregação granular e esfoliação da rocha que é fortemente percebido por se tratar de um material de alta durabilidade usado na fachada do prédio em áreaslocalizadas ao nível do chão. O exercício de mapeamento possibilitou a demarcação e observação das áreas afetadas pela formação de crosta negra sobre toda a fachada do prédio, principalmente concentradas em áreas abrigadas da ação da chuva. As análises demonstraram a influência de aerosóis marinhos, composição das rochas e argamassas e dos poluentes atmosféricos na deterioração e formação de crostas no granito. Muito da deterioração é associado especificamente a presença de sais, tais como halita (NaCl) e gipsita (CaS0(4).2H2O). O fato da crosta negra de gipsita ser capaz de se desenvolver sobre toda a fachada do prédio, em um ambiente sub-tropical úmido é testemunha da eficácia dos altos níveis de poluição local, especialmente da deposição de particulados, e da reduzida lavagem pela chuva em um micro-ambiente protegido,em ruas estreitas, que funcionam como corredores de poluição, impedindo a tendência da gipsita ser lavada das fachadas dos prédios históricos. Essa observação destaca que os processos de intemperismo operante, são principalmente controlados por condições microclimáticas

Decay effects of pollutants on stony materials in the built environment

This review discuss the effects that pollutants have on stony materials applied on the built environment, illustrating different macroscopical products (pathologies) that can affect historical and modern architectural works. The impact of the decay processes is related to the susceptibility of the materials, environmental conditions and the kind of pollutants that degrade building materials. Here are reviewed the main decay processes resulting from the actions of gases, particulate matter and solutions (from wet deposition to capillary rising and including circulating waters such as run-off), showing that besides atmospheric pollution, also pollutants rising from the ground can cause important deterioration on building materials. Following, the use of tracers is considered for the study of pollutant sources and migration, including neoformation minerals (that might also constitute markers of environmental conditions) and chemical tracers, giving special attention to isotopic tracers, namely to proposals regarding the use of some stable and radioactive isotopes for the study of pollutants that have strong potential but have not been tested yet are also presented. At the end of this chapter, some final considerations are made on the problem of durability assessment of materials in the built environment and also on the use of tracers to assess the origin of damaging compounds in the built environment.Fundação para a Ciência e a Tecnologia (FCT). Portuguese-Spanish collaboration Project ―Ação Integrada E-141/10‖ (Fundação das Universidades Portuguesas)/Acción Integrada PT2009-0077‖ (Ministerio de Ciencia e Innovación)