Effects of centrifugal forming and steam curing on the fracture behavior of PHC pipe pile concrete

Abstract PHC pipe pile concrete is characterized by high strength but pronounced brittleness, which makes it susceptible to cracking during the pile-driving process. To elucidate the effect of centrifugal forming and steam curing on the fracture properties of PHC pipe pile concrete, this study prepared centrifuged prismatic specimens using a self-designed centrifuge and carried out three-point bending fracture experiments combined with digital image correlation (DIC) and acoustic emission (AE) techniques. The results show that reducing the delay period to 2 h from 4 h, or extending the duration beyond 12 h at 80 °C, induces significant steam-related damage in concrete. This leads to a decrease in flexural strength and crack initiation toughness, as well as increased branching and irregularity in crack propagation paths. The AE ringing counts and energy decrease, showing a uniform distribution throughout the fracture process. In contrast, under proper steam curing conditions, the post-peak descending stage exhibits an explosive increase in both ringing counts and energy. Centrifugal forming compacts the concrete mixture, lowers the water-cement ratio, enhances initial strength, and mitigates the negative effects of steam curing. This provides a theoretical basis for reducing the delay period by approximately 2 h compared to conventional concrete, thereby improving production efficiency in the PHC pipe pile manufacturing process.