Bond failure of corroded rebar embedded in rubberized geopolymer concrete: Experimental evaluation

Reinforcement corrosion significantly limits the interfacial bond behavior of reinforced concrete (RC) structures in harsh environments. Developing concrete materials with erosion resistance and high toughness is critical for improving structural durability. Therefore, a total of 96 central pull-out specimens were tested to systematically investigate the combined effects among corrosion, geopolymer concrete type, and rubber replacement ratio on the bond behavior. The test results show that slag-based geopolymer (SG) specimens tend to crack, leading to the significant corrosion of internal steel bar, and no apparent enhancement in bond strength compared with that of ordinary Portland cement (OPC) specimens. Metakaolin-based geopolymer (MKG) specimens present a 37.5% higher bond strength than OPC in the uncorroded state. However, they demonstrate a pronounced sensitivity to corrosion, leading to a 31.6% reduction in bond strength. The water-repellency of hydrophobic metakaolin-based geopolymer (HMKG) alleviates the steel corrosion and results in a high bond strength retention of 80.8% under erosion conditions. The incorporation of rubber effectively enhances the toughness for all types of geopolymer concrete, which suppresses the corrosion-induced cracks and thereby improves durability and deformation capacity of interface. However, the compressive strength of the concrete decreases by 6.7–51.8% with rubber replacement ratio increasing, which aggravates the bond strength deterioration. The models of bond strength and ultimate slip were proposed by considering these factors, with MAPE values restricted to 11% and 7%, respectively. Then, the design formula of ultimate anchorage length was derived based on the bond-slip differential equation. This study provides an experimental and theoretical basis for structural concrete design with high durability.