Effect of severe chloride environment on the flexural behaviour of hybrid concrete systems

Abstract

This paper reports an investigation into the effect of a severe chloride environment on the flexural behaviour and microstructure of concrete composites combining normal- or high-strength concrete and ultra-high-performance fibre-reinforced concrete (UHPFRC). The normal- or high-strength concrete layers were used in the compression area while the UHPFRC, with three different fibre contents (1, 1·5 and 2%), was in tension. The goal was to measure the degradation of the bonding area and to investigate possible physical debonding under long-term exposure to a severe chloride environment. The microstructural properties of the degraded bond zone were examined by scanning electron microscopy, energy dispersive X-ray spectroscopy and backscattered electron imaging after 600 d of cycling exposure. The test results revealed that severe chloride exposure influenced the flexural capacity of the concrete composites. However, the bond between the normal- or high-strength concrete and UHPFRC layers was maintained without any distinctive degradation. In addition, an increase in the fibre volume in the UHPFRC layer significantly improved the mechanical resistance of concrete composite specimens, although higher chloride penetration depths were registered at increased fibre contents.