Influence of steel fibers on the reinforcement bond of straight steel bars

Resumen

Bonding between steel bars and concrete makes the two materials compatible, enabling the use of reinforced concrete as a construction material. If the bond is good, there will be fewer cracks, and the reinforcing bar will be better protected by the surrounded concrete. The aim of this research was to analyze the influence of steel fibers on concrete-steel bond strength. Therefore, pull-out tests were performed with thirty-three prismatic specimens measuring 200 mm x 300 mm x 150 mm. The variables analyzed were: bar diameter (10 mm, 12.5 mm, 16 mm and 20 mm); bond length (five and ten times the diameter); and the volume of steel fibers added to the concrete (1% and 2%). Short, steel, hooked fibers were used, 35 mm in length and with aspect ratio of 65. Based on the pull-out tests assays, the failure type and maximum load was determined for each specimen; computer simulations of the specimens were also performed with bars of 100 mm in diameter. Both the results of the experimental tests and the modeling showed that the addition of fibers had little effect on the bond strength between the bar and the concrete. On the other hand, when the bond failure occurred by splitting of the concrete cover, the influence of the steel fibers was significant.