Avaliação da biotransformação dos produtos da reação álcali-sílica por Bacillus clausii e Bacillus thuringiensis

Abstract

Currently, there are several ways to reduce the possibility of the occurrence of the alkali-silica reaction (ASR), when measures are adopted to attenuate the favorable conditions for its occurrence, avoiding possible damage to concrete structures. However, after the ASR is installed in a concrete structure, there is no fully efficient and economically viable solution to mitigate the expansive effects of the ASR. In the present research, the ability of Bacillus clausii and Bacillus thuringiensis microorganisms to biotransform RAS products was studied, and thus contribute to an initial study and proposition of an alternative, to solve problems caused by expansions in structures affected by ASR. The ASR products were synthesized under controlled laboratory conditions, from sources of amorphous (pyrex) and crystalline (pebble) silica and inoculated with microorganisms for a period of 40 days, being submitted to microstructural characterization using the DRX and FTIR techniques in periods of 10, 20, 30 and 40 days. The results showed that the bacteria B. clausii and B. thuringiensis were able to biotransform the ASR products, reducing to values greater than 80% of the initial product. The bacterias showed to be more efficient in the biotransformation of the RAS products produced from the amorphous aggregate (pyrex), biotransforming the products at values greater than 98% of the initial product, indicating that the mineralogy of the aggregates influences the biotransformation process. B. clausii proved to be more efficient in the process of biotransformation of RAS than B. thuringiensis, mainly because it presented a similar population growth in both samples produced with different sources of silica.