Behavior of Confined Self-Compacting Concrete under Compression at Elevated Temperatures

The performance of self-compacting concrete (SCC) is gaining popularity in construction due to its exceptional strength and durability. However, the properties of combined steel and concrete at elevated temperatures lack experimental data from previous research. This study aimed to investigate the behavior of the SCC core with a steel tube at ambient and elevated temperatures varying from 100 °C to 800 °C with 100 °C intervals for each test specimen. Tests were conducted on circular steel tubes filled with SCC for different grades (M25, M30, and M40) under compression at elevated temperatures. Experimental observations revealed that the stress–strain curve increased with increasing the cross-sectional area and grade of concrete. However, increasing the temperature and length-to-diameter ratio reduced the stress–strain curve. At elevated temperatures, confined SCC experienced a smaller decrease in the overall modulus of elasticity when compared to unconfined concrete. Within the compressive elastic region (from 30 °C to 400 °C), there was a significant relationship between lateral strain and longitudinal strain, which was followed by a sudden increase beyond 400 °C. Equations for various design parameters were proposed based on the peak load and confinement factor of confined SCC-filled steel tubes (SCCFSTs) via multiple regression. Moreover, this study developed load–axial shortening curves, identifying significant properties such as the yield strength of confined SCCFSTs, including the load-carrying capacity. The predicted numerical analysis results were well aligned with the experimental results, and the findings contributed valuable insights for designing resilient and durable combined SCC and steel tube infrastructures.

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