Condutividade térmica de rochas: uma aplicação para granitos ornamentais

This dissertation focuses on rock thermal conductivity and its correlations with petrographic, textural, and geochemical aspects, especially in granite rocks. It aims at demonstrating the relations of these variables in an attempt to enlighten the behavior of thermal effect on rocks. Results can be useful for several applications, such as understanding and conferring regional thermal flow results, predicting the behavior of thermal effect on rocks based upon macroscopic evaluation (texture and mineralogy), in the building construction field in order to provide more precise information on data refinement on thermal properties emphasizing a rocky material thermal conductivity, and especially in the dimension stone industry in order to open a discussion on the use of these variables as a new technological parameter directly related to thermal comfort. Thermal conductivity data were obtained by using Anter Corporation s QuicklineTM -30 a thermal property measuring equipment. Measurements were conducted at temperatures ranging between 25 to 38 OC in samples with 2cm in length and an area of at least 6cm of diameter. As to petrography data, results demonstrated good correlations with quartz and mafics. Linear correlation between mineralogy and thermal conductivity revealed a positive relation of a quartz percentage increase in relation to a thermal conductivity increase and its decrease with mafic minerals increase. As to feldspates (K-feldspate and plagioclase) they show dispersion. Quartz relation gets more evident when compared to sample sets with >20% and <20%. Sets with more than 20% quartz (sienogranites, monzogranites, granodiorites, etc.), exhibit to a great extent conductivity values which vary from 2,5 W/mK and the set with less than 20% (sienites, monzonites, gabbros, diorites, etc.) have an average thermal conductivity below 2,5 W/mK. As to textures it has been verified that rocks considered thick/porphyry demonstrated in general better correlations when compared to rocks considered thin/medium. In the case of quartz, thick rocks/porphyry showed greater correlation factors when compared to the thin/medium ones. As to feldspates (K-feldspate and plagioclase) again there was dispersion. As to mafics, both thick/porphyry and thin/medium showed negative correlations with correlation factor smaller than those obtained in relation to the quartz. As to rocks related to the Streckeisen s QAP diagram (1976), they tend to fall from alcali-feldspates granites to tonalites, and from sienites to gabbros, diorites, etc. Thermal conductivity data correlation with geochemistry confirmed to a great extent mineralogy results. It has been seen that correlation is linear if there is any. Such behavior could be seen especially with the SiO2. In this case similar correlation can be observed with the quartz, that is, thermal conductivity increases as SiO2 is incremented. Another aspect observed is that basic to intermediate rocks presented values always below 2,5 W/mK, a similar behavior to that observed in rocks with quartz 20% (granites). For all the other cases, correlation factors are always low and present opposite behavior to Fe2O3, CaO, MgO, and TiO2. As to Al2O3, K2O, and Na2O results are not conclusive and are statistically disperse. Thermal property knowledge especially thermal conductivity and its application in the building construction field appeared to be very satisfactory for it involves both technological and thermal comfort aspects, which favored in all cases fast, cheap, and precise results. The relation between thermal conductivity and linear thermal dilatation have also shown satisfactory results especially when it comes to the quartz role as a common, determining phase between the two variables. Thermal conductivity studies together with rocky material density can function as an additional tool for choosing materials when considering structural calculation aspects and thermal comfort, for in the dimension stone case there is a small density variation in relation to a thermal conductivity considerable variationCoordenação de Aperfeiçoamento de Pessoal de Nível SuperiorEsta dissertação aborda o tema condutividade térmica de rochas e sua correlação com aspectos petrográficos, texturais e geoquímicos principalmente em rochas graníticas. O intuito é demonstrar as relações destas variáveis tentando elucidar o comportamento do efeito térmico nas rochas. Os resultados poderão ser úteis em diversas aplicações, por exemplo, no entendimento e aferição de resultados de fluxo térmicos regionais, na predição do comportamento térmico de rochas baseados na avaliação macroscópica (textura e mineralogia), no segmento de construção civil com o objetivo de fornecer informações mais precisas no que diz respeito ao refinamento de dados sobre propriedades térmicas enfatizando a condutividade térmica de materiais rochosos e ainda especialmente na indústria de rochas ornamentais com o objetivo de se abrir uma discussão sobre a utilização destas variáveis como novo parâmetro tecnológico diretamente relacionado ao conforto térmico. Os dados de condutividade térmica foram obtidos a partir de um equipamento medidor de propriedades térmicas da marca Anter Corporation, modelo QuicklineTM -30. As medidas foram realizadas a temperaturas variando entre 25 e 38 OC em amostras com 2cm de espessura e área com pelo menos 6cm de diâmetro. Quanto aos dados petrográficos os resultados demonstraram haver boas correlações com o quartzo e máficos. A correlação linear entre a mineralogia e a condutividade térmica revelou uma relação positiva do aumento da condutividade térmica em função do aumento da percentagem de quartzo e diminuição com o aumento de minerais máficos. Já os feldspatos (K-feldspato e plagioclásio) mostram dispersão. A relação do quartzo fica mais evidente quando são comparados os conjuntos de amostras com >20% e