Pile is divided into post-tensioned prestressed pipe pile and pre-tensioned prestressed pipe pile, prestressed concrete pipe pile (PC pipe pile), prestressed concrete thin-wall pipe pile (PTC pipe pile) and high strength prestressed concrete pipe pile (PHC pipe pile). Prestressed pipe pile is a kind of thin concrete precast member with hollow cylinder made by prestressed process and centrifugal forming method. It is mainly composed of cylindrical pile body, end plate and steel hoop. According to the concrete strength grade and wall thickness, the pipe pile is divided into prestressed concrete pipe pile, prestressed high-strength concrete pipe pile code is PC, and prestressed high-strength concrete pipe pile code is PHC. The concrete strength of thin-walled pipe pile code PTC.PC pile shall not be lower than C50 concrete, the strength grade of thin-walled pipe pile shall not be lower than C60, and the concrete strength grade of PHC pile shall not be lower than C80. PC piles and PTC piles are generally maintained by atmospheric steam, which can be beaten only after 28 days. For PHC pile, after the release, it needs to be steamed in autoclave. After autoclaved curing at 10 atmospheres and about 180 degrees, the concrete strength level reaches C80. The shortest time from forming to using is only three or four days.
The application of fluoropgypsum to pipe piles can improve the strength at the early stage, and the particles of fluoropgypsum can repair the strength at the later stage. The use of fluoropgypsum as admixture of pipe piles can save the cost of steam maintenance and cement。The life of pipe piles with other admixtures is generally 50-60 years, and can reach 100 years with fluoropgypsum instead
