Usually, the construction of cement mortar fabric should be carried out after laying spiral steel pipes, pressure testing, and compacting the soil according to design requirements. Due to the small stiffness of steel pipes and thin-walled structures, the pipes must be in a stable state during the fabric construction process. If the fabric anti-corrosion layer is first made, then the pipe is lowered. During the construction process, due to significant deformation during lifting, transportation, and soil backflow, the anti-corrosion layer was damaged.
Before constructing the fabric, the inner wall of the pipeline must be cleaned to remove soft floating rust, soil, proportion, grease, welding furnace covers, and other accessories; The protrusion of the inner wall of the steel pipe shall not exceed one-third of the planned thickness of the anti-corrosion layer. The lateral deformation shall not exceed the planned rules and shall not exceed 2% of the inner diameter of the pipeline.
The internal anti-corrosion layer of cement mortar can be constructed by mechanical spraying, manual plastering, dragging, or centrifugal prefabrication. If it is necessary to use prefabricated methods to manufacture internal corrosion resistant layers, protective measures should be taken during transportation, installation, and backfilling.
During the construction process, cement mortar is mainly mixed, with a mass ratio of cement to sand of 1: (1-2). The slump of cement mortar is 60-80 millimeters, and the compressive strength of cement mortar should not be less than 30 MPA.
The internal anti-corrosion layer of cement mortar constructed by mechanical spraying method is smooth, fine, dense, with uniform thickness and good effect. Since the 1960s, foreign countries began using mechanical spraying for buildings in the 1930s, while China used mechanical spraying for buildings in Shanghai, Qingdao, Dalian, and other cities. When using mechanical spraying methods for construction, it is possible to manually paint elbows, special pipe fittings, and pipes on the side of the pipes, and use mechanical spraying fabrics to lubricate sudden changes.
In addition, resistance pipes or centrifugal prefabrication methods are widely used and will not be described in detail here. Regardless of the construction method used, the maintenance process is to ensure that the anti-corrosion layer in the cement mortar is free from cracks and hollow key links. Therefore, after the formation of a corrosion resistant layer in cement mortar, it is necessary to immediately block the pipeline to prevent air convection. After final setup, perform moist maintenance. Usually, the maintenance time of Portland cement should not be less than 7 days, while slag Portland cement should not be less than 14 days; Before watering, it should be continuously blocked and kept moist.