Estudo da aderência entre concreto e aço de alta resistência

Abstract

Reinforced concrete is the most widely used structural material worldwide, and the search for greater efficiency and sustainability has driven the development of high-performance materials, such as new high-strength steels bars. This paper presents an experimental study on the bond behavior between CA-70 high-strength steel (fyk = 700 MPa) and self-compacting concrete of different strength (C1, C2, and C3), using conventional CA-50 steel as a reference. The main objective was to analyze the bond stresses and failure modes, aiming to provide support for the safe application of this new material, which is not yet covered by the Brazilian standard NBR 6118 (ABNT, 2023-a). To this end, an experimental program was developed with direct pull-out tests on 36 cubic concrete specimens, using straight steel bars of the two categories with diameters of 10 mm, 12.5 mm, and 16 mm. The results indicated that CA-70 steel, in most scenarios, resisted pull-out forces greater than those of CA-50, especially in high-strength concrete (C2 and C3). However, this research observed a change in the mode of failure in conventional strength concrete (C1) for 16 mm bars, while CA-50 steel tended to yield and exhibit ductile failure by tearing, CA-70 steel suffered brittle failure by cracking the concrete with lower applied loads. It is concluded that, although the use of CA-70 steel is promising for optimizing structural designs, its application requires careful analysis of the failure mode, as simply replacing CA-50 can reduce ductility under certain conditions. Keywords: