Investigation of the Microstructural and Mechanical Properties of Fiber-Reinforced Roller-Compacted Concrete Under High-Temperature Exposure

In this study, the effects of different fiber types on improving the high-temperature performance of roller-compacted concrete (RCC) were comprehensively investigated. For this purpose, 60 mm long steel (S), polypropylene (PP), and environmentally sustainable waste steel (WS) fibers were incorporated into RCC at volumetric ratios of 0%, 0.25%, 0.50%, 0.75%, 1.00%, and 1.25%. The prepared specimens were exposed to controlled conditions at 25 °C (room temperature), 300 °C, 600 °C, and 900 °C, and the influence of thermal exposure on compressive strength and permeability characteristics was thoroughly evaluated. The findings revealed that high temperatures led to significant changes in the physical and mechanical properties of the concrete. Notably, at elevated temperatures such as 600 °C and 900 °C, S and WS fibers were found to reduce strength loss by limiting the propagation of microcracks within the concrete matrix. However, PP fibers were observed to lose their effectiveness at high temperatures due to melting in the range of approximately 160-170 °C, which negatively affected mechanical performance. One of this study's key findings is that waste steel fibers offer a sustainable alternative while exhibiting comparable performance to conventional steel fibers. These results highlight the potential of recycling industrial waste to reduce environmental impact and lower overall costs.