AvaliaÃÃo petrogrÃfica e experimental de agregados graÃdos afetados por deformaÃÃo tectÃnica, desenvolvimento de minerais de alteraÃÃo e texturas de exsoluÃÃo

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Concrete deterioration due to alkali-aggregate reaction (AAR) represents serious problem throughout the world. Geological structurals such as shear zones are formed from compressive, extentional and shearing tectonics movement. Rocks close to fault zones usualy have mineralogical features unsuitable to be used as aggegate. This research reports on the microstructural features of six samples of rocks from quarries close to fault zones in eastern Pernambuco (Borborema Province). The aim of this study is to evaluate coarse agregates affects by tectonics deformation through petrographical and experimental methods, especially with different deformation and textural patterns. Mean mineralogy, presence of minerals of alteration development and exsolution textures were analyzed in order to find their effect in the AAR. The methods applied were the petrographic analysis and the accelerated mortar-bar test to measured linear alongation of specimes. Petrographic analysis were conducted under an optical microscope by thin section studies. The results indicate that higher reativity was strongly associated with the amount of microcrystalline quartz that has undergone intense dynamic recrystallisation. This samples were closer to fault zones. It was also observed the important role developed by subgrain boundary in the reactivity, and to a smaller degree ondulatory extinction of quartz grains. Nevertheless, relationship between the amount of myrmekite or sericite with the degree of reactivity was not observed. Finnally, microscopic image by SEM and WDS shown presence of silica-alcaline gel coating the surface of the mortar and aggregate

ASSUNTO(S)

minerais de alteraÃÃo reaÃÃo Ãlcali-agregado alkali-aggregate reaction zona de falhas engenharia de minas fault zone alteration minerals

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