Positive effects of aligned steel fiber on bond behavior between steel rebar and concrete

Abstract

A new steel fiber reinforced concrete (SFRC) structure is proposed to improve the bond performance between steel rebars and concrete by aligning the limited steel fibers closely around the magnetized rebar, which is achievable to have both adequate steel fibers around rebar for high steel-concrete bonding and appropriate fiber content for good fluidity of concrete. An experimental test is performed to verify the effectiveness of the new structure. 41 specimens are designed and subjected to pull-out test to observe the effects of rebar magnetization, concrete consolidating condition and steel fiber content on bond behavior between steel rebars and SFRC. Results verify the positive effects of the new structure on bond behavior under the suitable conditions. Steel fibers can be aligned closely around the magnetized steel rebar and consequently increase bond behavior. In the present test, the average increments of bond strength are 28.2% and 20.8% for pull-out and splitting specimens as the magnetization intensity increased form 0 mT–30 mT, respectively. The maximum increment is up to 50.0%. Steel fiber shows dual roles to bond strength since it increases the concrete strength with deteriorated fluidity. The recommended content of steel fiber is about 0.25%–0.75% for the proposed structure. And, self-consolidating concrete with good fluidity is required for the movement of steel fiber under the attracted force from the magnetized rebar.