Bond characteristics of recycled scrap metal based milled reinforcing steel bars with reference to deformations of self-compacted concrete beams in sustainable construction

The interaction between reinforcing steel and its surrounding concrete plays a decisive role in the strength, safety, and service life of reinforced concrete structures. In this study, the bond–slip behavior of steel bars manufactured in Ghana was examined when embedded in self-compacting concrete (SCC) and normal concrete (NC). Controlled pull-out tests were carried out using 12 mm, 16 mm, and 20 mm diameter bars to evaluate stress–slip responses, bond efficiency, and bond energy absorption. The results demonstrated that SCC consistently outperformed NC, achieving peak bond stresses that were 12–28% higher, depending on bar size and mix proportions. In addition, SCC specimens exhibited up to 35% greater bond energy absorption, reflecting improved toughness and enhanced slip mobilization. The findings also confirmed that compressive strength alone cannot reliably predict bond capacity; instead, factors such as bar diameter, rib geometry, and concrete rheology exert a more significant influence. Overall, the study provides the first detailed evidence of how reinforcing steel bars recycled from scrap metals interacts with SCC, highlighting its potential for durable and resilient construction.