Estudo da influência de fibras metálicas no comportamento da aderência entre barras de aço e concreto de alto desempenho.

Abstract

To be possible for reinforced concrete to play structural role, there must be adequate stress transfer and strain compatibility between steel and concrete. Bond is the phenomenon that provides this solidarity between this two materials and its behavior is influenced by numerous factors, from those related to the fundamental components of the material, such as concrete strength and bar diameter, to variables whose uses are not essential for its mobilization, as the use of steel fibers in the composite. The aim of this work is to study the behavior of bond between steel bars

and high strength concrete with the addition of steel fibers. For this purpose, a push- out test was developed using cubic specimens with 20 cm of edge, pierced by ribbed

steel bars with different diameters (10, 12.5 and 16 mm), and produced with concrete with 60 MPa of compressive strength at 28 days. Bond length equal to 2.5 times the bar diameter was adopted and the tests were performed at 21 days. The steel fibers employed had a length of 60 mm in the volumetric ratio ranging from 0 to 0.75%. The experimental results demonstrated that the incorporation of steel fibers in the concrete leads an increase in the maximum bond strength, and this increase became more significant when the bar diameter was reduced. It was also evidenced that the theoretical values obtained with the expressions of NBR 6118:2014 underestimate the maximum bond strength in high performance concretes.