EXPERIMENTAL ANALYSIS OF MECHANICAL RESISTANCE IN CONCRETE STRUCTURES WITH FORMATION OF COLD JOINTS INCORPORATED WITH STEEL FIBERS

Cold joints are formed due to the interruption of concreting at the moment of launching and mixing (Torres, 2016). The formation of cold joints besides directly influencing the properties of the hardened concrete represents a common occurrence during the concreting phase in the works. As stated by Harsem (2005), the formation of the cold joints can directly affect the structural performance of the parts, reducing the mechanical characteristics of supported tension, and deformation. For Sampaio (2010) it is fundamental that the surface of the joint is treated properly so that the constructive discontinuity that the joint creates does not translate into structural discontinuity. In this sense, a material that has been widely used in the present day for concrete reinforcement is steel fibers, which can be applied in cases of joint formation. According to Banthia (2007), these fibers can be effective in arresting cracks at both micro and macro levels. Thus, the present article seeks to analyze the influence of cold joints on concrete parts and to evaluate, through an experimental study, the performance of the use of steel fibers in the bonding between concretes of different ages, aiming to improve the adhesion in the region of union among them, as well as to verify possible elevations of their resistance in the areas known as fragile planes. The results of this work show that in some cases CRF can improve its performance by up to 25%. The steel fibers were effective in the relief of pebbles in the joint joints and had a mechanism of rupture in the generalized cases that were used.