Experimental evaluation on interfacial bond performance between <scp>C30</scp> phosphogypsum‐based concrete and steel tubular

Abstract Phosphogypsum‐based concrete filled steel tubular (PGBC‐FST) was designed to improve the interface bond property. The experimental and theoretical studies were conducted on the cement‐based concrete filled steel tubular (CBC‐FST) and PGBC‐FST to compare the interfacial bond properties. The bond mechanisms of PGBC‐FST were discussed by experimental F‐S curve, to verify the better bond properties of the PGBC‐FST structure. Moreover, the effects of cement substitution rate, raw phosphogypsum/hemihydrate phosphogypsum (RPG/HPG), and wall thickness of steel tubular on the average bond strength and critical relative slip of PGBC‐FST were discussed using a single‐factor experiment. Simultaneously, the prediction models of average bond strength and critical slip displacement of PGBC‐FST were presented depending on the effects of cement substitution rate, RPG/HPG and steel tubular wall thickness. The results showed that PGBC‐FST had a higher average bond strength than CBC‐FST, and the highest value was 1.149 MPa. The average bond strength of PGBC‐FST increased with the increase of the cement substitution rate of PGBC, increased first and then decreased with the increase of HPG dosage, and decreased with the decrease of steel tubular wall thickness. The bond stress on the outer wall of the PGBC‐FST steel tubular presented a “V” shape distribution below the critical sliding load, and produced stress redistribution after the overall relative slip. The prediction models of average bonding strength and critical relative slip of PGBC‐FST exhibited good accordance with experimental results.