Cement mortar coated steel pipes are designed to provide both structural integrity and corrosion resistance. These pipes are filled with a cement-based mortar that has excellent thermal properties, allowing it to absorb significant amounts of heat energy. As a result, when exposed to fire, the temperature distribution within the pipe column becomes uneven, which can significantly increase the fire resistance time of the structure. This uneven heating helps slow down the rate at which the steel column is heated, and if the steel yields, the surrounding concrete can take on most of the axial load, preventing catastrophic collapse. Additionally, the presence of concrete in composite beams reduces the temperature of the steel beam, enhancing its fire resistance. Studies have shown that using this type of coating can reduce the amount of fireproof material needed by up to two-thirds or more while still meeting a 3-hour fire resistance requirement.

The strength grades of cement mortar used in these applications include M3, M5, M7.5, M10, M12.5, M15, M20, M25, M30, and M40. Depending on the application, the mortar is categorized into masonry, plastering, and jointing, but these classifications are not directly related to the grade. After the mortar work is completed, an essential step is air drying, which typically takes 2–3 days under natural conditions. This process helps prevent cracks caused by impacts during transportation, ensuring long-term durability.

Steel components are also affected by external forces, which can influence their deformation, stability, and fatigue resistance. For example, hot-rolled steel products may experience dimensional changes due to thermal expansion and contraction. Even if the dimensions are within tolerance at the time of production, they may shrink slightly after cooling. The larger the width and thickness of the steel, the more pronounced this effect becomes. Therefore, for large steel sections, precise measurements of edge width, thickness, length, angles, and edges are challenging to achieve.

Internal corrosion protection for cement mortar coated steel pipes includes several methods:

• Three-layer polyethylene (3PE) and two-layer polyethylene (2PE) coatings for oil and gas pipelines.
• Single-layer and double-layer fused epoxy (FBE) coatings for oil and gas applications.
• IPN8710 non-toxic macromolecular coatings for water supply pipelines.
• High-density polyethylene polyurethane foam insulation for thermal protection.
• Cement mortar lining for internal corrosion resistance in water supply systems.
• Epoxy coal tar fiberglass cloth coatings for added durability.

These cement mortar coated steel pipes are widely used in various industries:

1. Municipal Engineering: Suitable for high-rise building water supply, heating networks, tap water systems, gas transmission, and buried water pipelines.
2. Petroleum and Chemical Industries: Used in process pipelines for transporting corrosive media, as well as in pharmaceuticals, printing, and dyeing sectors.
3. Sewage Treatment: Ideal for sewage discharge lines, drainage pipes, and anti-corrosion projects in biological pools.
4. Agriculture: Offers superior corrosion resistance compared to traditional steel structures, making it ideal for irrigation, deep well, and drainage systems. It also enhances the fire resistance and safety of steel pipes.

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