Effects of internal expansion reactions on the mechanical properties of concrete.

Abstract

Among the various deleterious actions that can attack concrete elements is the alkali-aggregate reaction (AAR), which mainly affects the structures of dams, bridges and foundations, the most recurrent of which is the alkali-silica reaction (ASR). Due to the early deterioration of concrete in residential buildings and bridges in the Metropolitan Region of Recife, scientific studies have been carried out over the last decade to find out how this process works, with the aim of developing measures that can provide an acceptable level of performance and durability, in accordance with the regulations in use. One of the main challenges in predicting this phenomenon is understanding how the mechanical properties of concrete are affected, which is the subject of this research. In this master's research, samples made in the laboratory were tested to evaluate the ASR and its effect on the mechanical properties of the concrete samples. The tests carried out were compressive strength, static modulus of elasticity of the concrete and tensile strength, using different cements: CPIV and CPV. Visually, it was possible to identify some cracks on the surfaces of the samples and traces of silica gel. The values of the concrete's mechanical properties showed different results: the concrete's compressive strength was little reduced by the reaction. On the other hand, the static modulus of elasticity was significantly reduced by 35% and 38% for each cement respectively. The tensile strength was reduced by 9% and 30%, but these results must be analyzed carefully, given the conditions in which they were tested. Therefore, the method used to create artificial ASR proved to be effective and has the potential to be used in further ASR studies. The modulus of elasticity also proved to be the most suitable tool for detecting the presence of ASR.