Influence of steel fiber corrosion on tensile properties and cracking mechanism of ultra-high performance concrete in an electrochemical corrosion environment

Abstract In this paper, the mechanisms by which the tensile mechanical properties of ultra-high performance concrete (UHPC) are influenced by the degree of steel fiber corrosion are investigated via accelerated electrochemical corrosion, direct tensile testing, and acoustic emission (AE) analysis. The elastic modulus is shown to decrease, while the ultimate tensile strength initially increases and subsequently decreases, with increasing corrosion time. Further, an increased degree of corrosion is shown to decrease the crack control capability of the UHPC such that crack widths rapidly increase and a large amount of AE energy is generated. Concurrently, the cracking behavior due to corrosion of the steel fiber network is examined by X-ray computed tomography (X-ray CT), revealing that corrosion cracking and cambium spalling are facilitated by concentration of the steel fibers. In the case of a small amount of corrosion, the chloride ions permeation is found to be small, and the corrosion only occurs on the surface of the specimens. With increased corrosion time, however, chloride ions gradually penetrate into the interior of the specimen, thus increasing the degree of corrosion. Finally, a formula is established for predicting the time of corrosion cracking in the concrete cover, and a parametric analysis is performed.