Experimental study on mechanical behavior and bond-slip of historical Chinese rebars during 1912 to 1949

Recognizing the unique construction nature and significance of historical reinforced concrete structures (1912–1949 in China), targeted research is vital for conservation strategies. This study collected and sorted six types of historical steel rebars based on their shape and size parameters. Constant uniaxial tensile tests and dynamic pull-out tests (loading rates of 2, 5, and 10 mm/min) were conducted investigate the tensile and bond-slip behaviors. Metallographic analysis was employed to assess the microstructure. The results indicate that spiral rebars exhibit higher tensile strength and pearlite content up to 48.77%) but with compromise ductility compared to square rebars. Increased pull-out loading rates enhanced bonding strength (up to 8.11%) but accelerated failure. Representative bond-slip curves were developed (average R 2 > 0.93), and a simplified analytical bond-slip model accurately approximating experimental strength was proposed. This work contributes to a deeper understanding of historical steel rebars, establishing a solid foundation for their conservation.