Cement mortar lined anti-corrosion steel pipe

Cement mortar lined anti-corrosion steel pipe is a special type of anti-corrosion pipe material that undergoes anti-corrosion and wear-resistant treatment with cement mortar inside the pipe body. The mixed cement mortar is applied to the cleaned inner wall of the pipe in one or multiple times according to the design thickness requirements. After a certain period of curing, a high-strength circular shell lining layer is formed that is tightly bonded to the inner wall of the pipe.

Main components and ratios

Cement mortar is made by mixing cement, sand, and water. The commonly referred 1:3 cement mortar is a mixture of 1 part cement and 3 parts sand, and the actual water ratio is generally around 0.6, which should be 0.6:1:3. However, the mix proportion may vary depending on the different raw materials and mortar applications. For example, taking the commonly used 42.5 ordinary Portland cement and medium sand mixed with 100 (M10) masonry mortar as an example: cement 305kg: sand 1.10m ³: water 183kg. When in use, additives such as foaming agents and waterproof powders should be frequently added in proportion to improve its workability and viscosity.

Construction technology

Construction method

Centrifugal method: a construction process that uses equipment such as centrifuges to rotate cement mortar at high speed with steel pipes, generating a large centrifugal force and uniformly adhering to the inner wall of the steel pipe. It is generally suitable for anti-corrosion construction in pipelines with a diameter of less than 400mm.

Spraying method: The construction process of using a spraying machine to apply cement mortar inside the steel pipe and press it smooth is generally suitable for anti-corrosion construction inside pipelines with a diameter of 700mm or more. For large-diameter pipelines with a diameter of over 800, it is necessary to add wire mesh to enhance the strength of the cement mortar and prevent cracks from falling off during anti-corrosion treatment.

Operation process using spraying method as an example

Preparation before anti-corrosion: The anti-corrosion of the cement mortar inside the steel pipe can be carried out centrally in the steel pipe factory or on-site pipe yard, or as a whole after the steel pipe is installed and welded in place. During centralized construction, sufficient welding areas should be reserved at both ends of the steel pipe, and the anti-corrosion layer should be completed after installation and welding are completed.

Trial mix mortar and test its performance: Before starting construction, it is necessary to first test mix mortar and verify its performance indicators, including workability, slump, compressive strength, and other aspects.

Equipment connection and trial operation: Place the concrete pump on the slightly lower side of the sprayer and connect the two with a pumping concrete pipeline. Connect the power and add water to the hopper for trial operation to wet the hopper and confirm that the equipment is in good working condition. For electrical safety, intact and seamless waterproof wires should be used, and if any damage is found, they should be replaced immediately.

Mortar mixing: Cement mortar can be mixed in a centralized mixing station or on-site using a mobile rolling hole mixer.

Spraying operation: Turn on the spraying machine and concrete pump, fill the mortar into the concrete pump, and start the spraying operation. Adjust the mortar flow rate and pressure device when the nozzle starts to dispense slurry to achieve satisfactory spraying effect.

Air drying process

After the completion of the cement mortar work, it needs to be air dried for 2-3 days in a natural state, mainly to prevent cracks in the cement mortar caused by bumps during transportation.

Performance characteristics

Corrosion Resistance

It can isolate the inner wall of the steel pipe from water or air, forming a dense protective layer, thereby suppressing oxidation and corrosion of the inner wall of the steel pipe. By utilizing the alkalinity of cement mortar, a passive film is formed on the inner surface of the pipeline for protection. And after the steel pipe is put into operation, the cement mortar continues to harden in water for a long time, which can automatically close the cracks without affecting the anti-corrosion effect.

hydraulic condition

After actual testing, it has been proven that the anti-corrosion inside the cement mortar is smooth and uniform, and can cover all the unevenness and welds on the inner wall of the steel pipe. Its surface can form a layer of slippery material containing manganese, thereby reducing frictional resistance. Its roughness coefficient is about 0.012, and it will gradually decrease with the extension of service life. The roughness coefficient of steel pipes and cast iron pipes is about 0.016-0.024.

Fire resistance performance

Due to the concrete filling inside the steel pipe, it can absorb a large amount of heat energy. Therefore, the distribution of temperature field in the cross-section of the pipe column during a fire is very uneven, which increases the fire resistance time of the column, slows down the heating rate of the steel column, and once the steel column yields, the concrete can bear most of the axial load, preventing structural collapse. The fire resistance of composite beams will also be improved, as the temperature of the steel beams will be reduced by transferring heat from the top flange to the concrete. Experimental statistical data shows that meeting the requirement of a first level fire resistance of 3 hours can save 1/3-2/3 or even more fireproof coatings compared to steel columns. As the diameter of the steel pipe increases, more coatings are saved.

Other features

It also has the characteristics of corrosion resistance, non leakage, high toughness, excellent flexibility, good scratch resistance, and good resistance to rapid crack propagation. It has a long service life and can be used for more than 50 years in environments above 60 degrees Celsius.

Execution standards

The implementation standard is CECS10:89 or GB50268-2008, which involves equipment such as steel pipe shot blasting and rust removal machine, three PE winding equipment, PE pipe black and yellow jacket pulling machine, sandblasting and rust removal equipment, polyurethane low-pressure marking machine, foaming platform, fiberglass winding machine, two PE coating, cement mortar spraying machine and other anti-corrosion and insulation supporting testing equipment.

purpose

Suitable for municipal engineering pipelines such as water supply for high-rise buildings, heating networks, water supply projects, gas transmission, and buried water transmission; Process pipelines for transporting corrosive media in industries such as petroleum transportation pipelines, chemical pharmaceuticals, and printing and dyeing; Anti corrosion engineering for sewage treatment discharge pipes, sewage pipes, and biological tanks; Agricultural irrigation pipes, deep well pipes, drainage pipes, and other agricultural networks.