Corrosion of steel rebar embedded in UHPC beams with cracked matrix

Abstract

Intact ultra-high-performance concrete (UHPC) can properly protect embedded steel rebar from corrosion. However, cracks initiate and propagate in UHPC beams under loading, which will facilitate the corrosion of steel rebar. In this study, UHPC beams made with different steel fiber contents (0.5 vol% and 2.0 vol%) were pre-cracked to generate different primary crack widths (0.1, 0.2 and 0.4 mm) on the tensile surfaces. The electrochemical behaviors and corrosion states of steel rebar embedded in these cracked beams were investigated in 3.5 wt% NaCl solution for 174 days. The results indicated that the corrosion rate of steel rebar in UHPC with cracks was reduced with time, and corrosion was not amplified and was restrained within the initially generated corrosion spots. When the primary crack width in UHPC beams was limited to 0.1 mm, steel rebar likely remained in the uncorroded state. Higher content of steel fibers (2%) could provide better bridging effects to reduce the corrosion rate without introducing galvanic corrosion on steel rebar. Besides, the Stern-Geary coefficients B of steel rebar embedded in UHPC beams with cracked matrix are determined to be 13.5 and 14.1 mV for active and passive corrosion, respectively. Also, this paper found the UHPC has low efficiency in autogenous self-healing.