Abstract
Currently, there are several ways to reduce the possibility of the occurrence of the alkali-silica reaction (ASR), when measures are adopted that attenuate the favorable conditions for its occurrence, avoiding possible damage to concrete structures. However, after ASR has been installed in the concrete structure, does not exist a completely efficient and economically viable solution that attenuate the expansive effects of ASR. In the present research, the ability of Alkalihalobacillus clausii (formerly Bacillus clausii) and Bacillus thuringiensis microorganisms to biotransform ASR products was studied, and thus contribute to an initial study and proposition of an alternative, to solve problems caused by expansions in concrete structures affected by ASR. The ASR products were synthesized under controlled laboratory conditions, from sources of amorphous (pyrex) silica and inoculated with microorganisms for a period of 40 days, being submitted to microstructural characterization using the XRD, DTG/TG and FTIR techniques in periods of 10, 20, 30 and 40 days. The results showed that the A. clausii and B. thuringiensis bacteria were able to biotransform the ASR products. XRD's showed that there was biotransformation of the elements contained in the samples due to the reduction in the degree of crystallinity of the samples inoculated with bacteria. Thermal analyzes showed that there was biotransformation of ASR products from reducing weight loss in samples inoculated with bacteria compared to non-inoculated samples. The FTIR's showed that the bacteria are capable of biotransforming the ASR products, reducing the vibration bands associated with the ASR products to values greater than 98 % of the initial product. The FTIR analyzes also showed that the diversity of elements present in the mineralogy of the aggregates and that are part of the metabolism of the bacteria can influence, depending on their availability, in the efficiency of the biotransformation process of the ASR products.
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