Fire-resistance behavior of concrete columns produced with recycled ceramic and silica aggregates: An experimental and numerical approach

Abstract

This article aims to fully assess the fire-resistance behavior of fiber-reinforced concrete (FRC) columns made with recycled ceramic aggregates when subjected to severe thermal loading. In addition, the effects of fiber reinforcements and ceramic recycled aggregates (RAs) on the thermal behavior of concrete columns were addressed and compared with that of the conventional silica-made concrete columns. In this regard, twelve small-scale FRC columns containing recycled ceramic and silica aggregates are prepared and placed in a heating chamber for 90 min. Next, the columns were axially loaded until failure, and variations in compressive stress and axial strain of the specimens were measured, aiming to capture the thermal effects on the load-carrying capacity, axial strain, and failure modes of the concrete columns. The specimens were exposed to high temperatures of 20 °C, 600 °C, and 1000 °C according to ISO 834 Fire Standard, and were tested in humid and dry environmental conditions. Moreover, the failure modes of the columns (e.g., concrete spalling, crack pattern, etc.) are presented in terms of macroscopic imaging. In addition, in-depth analyses of the effects of fibers (steel and polypropylene) and moisture content on the thermal behavior of concrete columns is addresses utilizing scanning electronic microscope (SEM) technique. The results indicate that below the temperature of 600 °C, the axial behavior of the FRC columns with silica and ceramic aggregate are similar. However, as the temperature rises, the reduction in axial load-bearing capacity of the columns with silica aggregates is higher than that of the columns with ceramic aggregates. Also, it was observed that the environmental humidity negatively affects the overall fire-resisting behavior of the columns. Furthermore, a numerical procedure is presented in ABAQUS to estimate the behavior of FRC columns subjected to thermal loading and validated using the experimental results.