Results of long-term exposure tests of steel fiber-reinforced concrete structures are reported. Comparisons are made between fibers bridging cracks and fibers fully embedded in the concrete, after which fibers were analyzed by electron microscopy. Reference testing was performed at 6, 12, and 18 months. No decrease of strength could be detected after 18 months of exposure. Electrochemical measurements on the sensors show negligible corrosion, confirmed by the microscopic analysis.