Mechanical properties of recycled aggregate concrete reinforced with conventional and recycled steel fibers and exposed to high temperatures

The widespread use of concrete has significantly impacted the environment, resulting in substantial greenhouse gas emissions and strain on natural resources. This study investigated the mechanical properties of concrete made with recycled aggregate, conventional steel fibers and recycled steel fibers subjected to high temperatures. This is a crucial consideration in practical applications, such as structures exposed to fires or high temperature environments, and it is an integral part of assessing the durability and safety of alternative construction materials. The following variables were studied: three percentages of recycled aggregate substitution (0, 50 and 100 %), three quantities of conventional and recycled fibers (0, 40 and 80 kg/m3), four temperature steps (20, 200, 400 and 600 degrees C). The recycled steel fibers came from used tires. The studied variables were the consistency, the hardened density, the compressive strength, the dynamic and static elasticity modulus, the thermal conductivity, the flexural strength and the stress-strain behavior. Besides, scanning electron microscopy photographs were taken to analyze in detail the concrete structure. The main result obtained is that concrete with all recycled aggregate and recycled fibers underwent, in general, the same mechanical properties as a conventional concrete (without fibers and without recycled aggregate) for any temperature step.