Manhole cover materials should be selected based on the actual usage scenario. The main types and technical parameters are as follows:
Cast Iron:
Gray cast iron: Tensile strength not less than 150 MPa, hardness 170-230 HBW (conforms to GB/T9439 standard);
Ductile cast iron: Tensile strength not less than 420 MPa, elongation not less than 10%, requires hot-dip galvanizing treatment (coating thickness not less than 70 μm, conforms to GB/T1348 standard).
Composite materials: Resin matrix + glass fiber reinforcement (content not less than 30%), compressive strength not less than 30 MPa, acid and alkali corrosion resistance (no deformation after immersion in pH 2-12 solution for 72 hours).
Reinforced concrete: Good load-bearing performance, low cost, suitable for low-load areas such as green belts and suburban roads.
