Our Prestressed Concrete Quality Control Process

The quality of prestressed concrete piles and slabs is not the result of any single step, but the sum of standards controlled from raw-material selection through to the final stage of production. This article summarizes the core standards our company applies to every piece of prestressed concrete we manufacture.

It starts with concrete strength, which must be at least 350 kg/cm² (tested on a 6"×12" cylinder sample) or at least 450 kg/cm² (tested on a cube sample) at 28 days, using Portland cement Type I or Type III at a minimum of 400 kg/m³ — fixed values applied to every production run.

Next is the prestressing (PC) wire, which carries the structure's primary tensile load. Wire at 4.0 and 5.0 mm must reach a minimum tensile strength of 17,500 kg/cm², while 7.0 mm wire must reach at least 17,000 kg/cm². During tensioning in the mould, the wire is never stressed beyond 75% of its ultimate tensile strength, preserving a safety margin throughout the process. Reinforcing steel used alongside it must have a yield strength of at least 2,400 kg/cm².

One of the most critical steps is prestress transfer, which only takes place once the concrete in the mould has reached a minimum strength of 280 kg/cm². Waiting for the concrete to reach this strength before releasing tension from the PC wire protects the internal structure of the piece from the outset, and is checked every time before the step proceeds.

Throughout production, the company relies on modern machinery paired with computerized production control, with rigorous quality checks at every stage — from raw-material selection and concrete mixing to forming, prestress transfer, and inspection of the finished product — so that every piece delivered to a customer consistently meets the standard set out above.

These standards are not limited to piles alone — they apply equally to every prestressed slab type the company manufactures. Whichever product a customer chooses, the concrete strength, PC wire tension, and prestress-transfer procedure are held to the same standard every time.