The greater the thickness of concrete protective layer, the better the bond and anchorage performance, durability and fire resistance of reinforced concrete members. However, if the protective layer is too thick, the crack width will be too large, which will affect its performance, and it will also cause economic waste.

When there is a cushion, the thickness of the protective layer of the reinforcement at the bottom of the foundation should be calculated from the top surface of the cushion, and should not be less than 40mm；; Without cushion, it should not be less than 70 mm, and the thickness of reinforced protective layer on the ground of pile cap should not be less than the length of pile head buried in pile cap.

Extended data:

The thickness of the protective layer at the end of reinforced concrete flexural members should not be less than10 mm; ; The protective layer thickness of the main reinforcement of precast ribbed slab should be selected according to the numerical value of the beam.

The protective layer thickness of steel bars distributed in plates, walls and shells should be reduced by 10mm and should not be less than10 mm; The protective layer thickness of stirrups and structural reinforcement in beams and columns should not be less than15 mm.

When the thickness of concrete protective layer of longitudinal reinforcement in beams and columns is greater than 40mm, effective anti-crack structural measures should be taken for the protective layer.