1.
The protective layer of steel bars is relatively thin.
In a type of environment (indoor dry environment), which is a house that has been inhabited for 50 years, the floor and interior walls are 15mm, and the beams and columns are 20mm.
Of course, the concrete strength here is taken as c30, and the strength is reduced by one level and the protective layer is increased by 5mm.
If the protective layer is thin, chloride ions in air or water can easily penetrate the thin protective layer and corrode the steel bars.
So, what factors can cause the protective layer to be thin?.