Experimental Analysis of Steel–Concrete Bond Strength Under Varying Material and Geometric Parameters

This study presents the outcomes of a comprehensive experimental investigation focused on the bond behavior between reinforcing steel bars and concrete, assessed through standardized pull-out tests. The primary objective was to evaluate the influence of some key parameters: reinforcement bar diameter, concrete age (and associated compressive strength), steel microfiber content, and bentonite coating on rebar surfaces. Experiments were conducted under controlled laboratory conditions in accordance with relevant standards. Slip between steel and concrete was measured using a sophisticated high-precision optical laser device, enabling accurate assessment of bond characteristics. A large, i.e. statistically sufficient number of specimens was tested, allowing the results to be analyzed using analysis of variance (ANOVA) technique to determine the statistical significance of each parameter. Findings indicate that bentonite suspension coating do not significantly affect bond strength. Similarly, variations in bar diameter and microfiber content showed no statistically significant impact within the tested ranges. In contrast, concrete age — closely related to its compressive strength — exhibited a statistically significant influence, confirming that concrete maturity is a dominant factor in bond development. The results contribute to a better understanding of bond mechanisms in reinforced concrete and thus assist in optimizing design strategies where bond performance is critical.