Análise da fluência à compressão de concretos com fibras metálicas com classes de resistências de 25 e 50 MPa

Abstract

The time dependent properties of materials, such as creep and retraction, are directly related to the durability, safety and performance of structures. The creep of the concrete is defined as the deformation observed over time caused by a constant tension applied to the element. Such deformation is caused mainly by the movement or removal of water in the cement paste. It is objective of this work to analyze the influence of the addition of steel fibers on concretes with resistance class of 25 and 50 MPa about creep when subjected to compression. For this, an experimental apparatus was used to determine the creep in concrete specimens in a simplified way, discarding the use of internal extensometers in concrete and complex devices, remaining within the precepts of ACI 209.2R, CEB MC90-99 and ABNT NBR 8224:2012. Conventional concretes with compressive strength of 25 and 50 MPa were tested with addition of steel fibers in the contents of 30, 40, 50 and 60 kg/m³, wich correspond to 0.38%, 0.50%, 0.6% and 0.77% by volume. The test was performed in concrete test specimens aged 28 days, submitted to compression stress equivalent to 35 % of the estimated ultimate resistance, in a room with controlled temperature and relative humidity conditions. The duration of the test was 90 days, with daily data collection.