Prestressed pipe pile suitable for underground sulfate corrosion environment and preparation method thereof
Technical Field
The invention relates to a prestressed pipe pile, in particular to a prestressed pipe pile suitable for an underground sulfate corrosion environment and a preparation method thereof.
Background
Pile foundations have been widely used in today's various projects because they can overcome the effects of adverse geological conditions and provide high bearing capacity. The tubular pile is used as an important pile foundation form, and due to the characteristics of low water cement ratio centrifugal forming, prestressed reinforcement cage inclusion, industrial control production and the like, the tubular pile has good pile body forming quality and high strength, and is convenient and rapid to construct and can meet the requirements of various engineering geological bearing capacities. With the rapid development of economic construction in China and the continuous promotion of urbanization and coastal large development, the demand of the tubular pile is huge, and by the incomplete statistics of relevant data, the annual production of the tubular pile in China is nearly 2.5 million meters and the production value reaches more than 300 million yuan RMB by the end of 2007; by the end of 2011, more than 500 tubular pile production enterprises exist in China, the annual output exceeds 3.5 hundred million meters, and the tubular pile production method becomes the country with the highest tubular pile production in the world.
China has wide territory, complex and various natural environments, complex and various service environments of pile foundations, and very common marine and offshore chloride ion corrosion environments and inland salt lakes and saline-alkali soil sulfate corrosion environments. The degree and mechanism of the corrosion damage of the concrete structure in different corrosion environments are different, the concrete structure deterioration in the marine and offshore chloride corrosion environments is mainly rust swelling cracking damage caused by steel bar corrosion, but the durability deterioration of the concrete structure in the salt lake and saline-alkali soil sulfate corrosion environments is mainly sulfate crystallization swelling cracking damage. The corrosive action of the corrosive ions under the environmental conditions can cause considerable damage to the pile body, the quality of the pile body is seriously affected, the bearing capacity and various performances of the pile body are endangered, the damage phenomenon is continuously aggravated along with the prolonging of time, serious potential safety hazards are brought, and the safety of the upper structure is seriously threatened.
Therefore, the industrial building anti-corrosion design code GB50046-2008 stipulates that SO is a problem that the prestressed reinforcement of the pipe pile is sensitive to corrosion and the pipe wall is thin4 2-And Cl < - > are strong corrosive media, the prestressed concrete pipe pile in a sulfate corrosion environment is not adopted, and the prestressed concrete pipe pile in a chloride corrosion environment is not easy to adopt. The standard limitation undoubtedly brings crisis to the development of the pipe pile industry, and the urgent requirement is also metPile shapes more meeting the industry requirements are designed to serve the development of the building industry.
Geopolymer materials are a new type of inorganic non-metallic materials which are newly developed in recent years, and are the most promising type of alkali-activated cementing materials. The material is a gelled material bonded by aluminosilicate gelling components, and is prepared by taking natural aluminosilicate minerals or industrial solid wastes as main raw materials, fully mixing the natural aluminosilicate minerals or industrial solid wastes with other mineral admixtures and alkali silicate solutions, and then curing, forming and hardening the mixture at normal temperature or under a steam curing condition. Compared with the traditional portland cement, the geopolymer material has the advantages of high strength (the compressive strength can reach 60-150 MPa), acid and alkali corrosion resistance (the material is soaked in a sulfate solution for a long time, the performance is stable, the corrosion is avoided), compact microstructure and extremely low permeability (the permeability coefficient is less than one percent of that of portland cement), and the like; is an environment-friendly green building material. If the outer wall of the geopolymer protective layer is added on the surface of the pipe pile, the sulfate corrosion resistance of the pipe pile can be greatly improved, and therefore the pipe pile is applied to a sulfate corrosion environment.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a prestressed pipe pile suitable for an underground sulfate corrosion environment and a preparation method thereof so as to meet the requirement on the durability of a pile body under the underground sulfate corrosion condition.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
the prestressed pipe pile suitable for underground sulfate erosion environment comprises a pipe body. The pipe body is a double-layer pipe body, the outer layer of the pipe body is a fiber-reinforced geopolymer-based composite material protective layer, and the inner layer is a reinforced concrete pipe layer; the interior of the pipe body is filled with hardened foam concrete.
The fiber-reinforced geopolymer-based composite material is composed of a powder material and organic fibers, wherein the fibers account for the powder material in percentage by mass: 3 to 8 percent.
The powder material comprises the following components in percentage by mass: 50-70% of granulated blast furnace slag micro powder; volcanic ash material 10-30%; 5-15% of Portland cement; sodium silicate excitant (measured by Na2O contained in it) 4-8%.
The organic fiber is polypropylene fiber, polyacrylonitrile fiber, ultra-high molecular weight polyethylene fiber, polyvinyl alcohol fiber, polyester fiber or polyformaldehyde fiber.
The granulated blast furnace slag micro powder is S95-grade granulated blast furnace slag micro powder, and is prepared by carrying out magnetic separation and iron removal on granulated blast furnace slag and grinding the granulated blast furnace slag to ensure that the specific surface area is more than or equal to 400 m2/kg, wherein the superfine granulated blast furnace slag micro powder with the particle size of less than 30 mu m accounts for more than 90 percent of the total mass;
the volcanic ash material is silica fume, kaolin or fly ash.
The sodium silicate excitant is sodium silicate which is prepared by adjusting sodium hydroxide to sodium silicate, has the modulus of 1.0-2.0 and the baume degree of 37-41 degrees.
The foam concrete is a novel light heat-insulating material containing a large number of closed air holes, which is formed by fully foaming a foaming agent in a mechanical mode through a foaming system of a foaming machine, uniformly mixing foam and cement slurry, then carrying out cast-in-place construction or mould forming through a pumping system of the foaming machine and carrying out natural maintenance.
The tubular pile is produced by a secondary centrifugal process, the outer wall of the sulfate erosion resistant protective layer is formed by centrifugation for the first time, the isolation and containment function is mainly played, and the reinforced concrete pipe body is formed by centrifugation for the second time, and the stress bearing function is mainly played. The outer wall of the anti-corrosion protective layer formed for the first time is used for isolating the internal bearing pipe body from the external corrosion environment, so that the damage of the structural integrity of the internal bearing pipe body in the corrosion environment and the decline of various performances are avoided. The water consumption is preferably slurry liquid-solid ratio =0.3-0.5
The invention relates to a preparation method of a prestressed pipe pile suitable for an underground sulfate corrosion environment, which comprises the following steps:
step 1, adding water to prepare fiber-reinforced polymer-based composite material slurry according to the liquid-solid mass ratio = 0.3-0.5.
Step 2. preparation of sulfate erosion resistant pipe body
Placing a reinforcement cage in a centrifuge die; then, injecting fiber-reinforced geopolymer-based composite material slurry, wrapping a fiber-reinforced geopolymer-based composite material protective layer on the outer surface of the centrifugal casting pipe body, curing with a mold for a set time, and performing primary molding; and then distributing the concrete mixture of the pipe body, tensioning the prestressed tendons according to the construction process of the existing prestressed pipe pile, performing centrifugal molding again, and performing autoclaved curing to obtain the sulfate erosion resistant pipe body.
Step 3. core filling protection
After pile sinking on the construction site, foam concrete is filled into the sulfate erosion resistant pipe body, and the pipe pile is obtained after the foam concrete is hardened. The foam concrete does not bear load, and mainly plays a filling role to prevent underground water containing aggressive media from permeating into the pipe through the pipe pile joint and directly generating erosion damage to the inner part of the pipe body.
The size of the sulfate erosion resistance of the tubular pile is closely related to the performance of the outer wall of the protective layer formed by centrifugation for the first time, and the concrete characteristics are as follows: with the increase of the erosion resistance of the outer wall (material) and the thickness of the outer wall, the higher the erosion resistance of the tubular pile. In actual engineering, materials and wall thickness can be reasonably adjusted and designed according to the specific corrosion degree of the underground sulfate environment.
The time interval of two centrifugation of rational control, after the protective layer outer wall of first centrifugal forming is congealed and reaches certain intensity for the beginning, just can continue the feed and carry out the centrifugal forming for the second time, concrete intensity numerical value should be in order to guarantee that the tubular pile outer wall is not damaged in the centrifugal forming process for the second time and carry out the reasonable arrangement design as the basis. Thereby satisfying and making primary molded's outer wall and post forming's body zonulae occludens on the basis of not producing the damage to the outer wall furthest.
The tubular pile has the following beneficial effects:
(1) high anti-corrosion ability of sulfate and durability.
The protective layer outer wall structure of the product is prepared by adopting a fiber reinforced geopolymer material with high sulfate corrosion resistance. Through the protective layer outer wall structure of first centrifugal molding for the reinforced concrete structure of inside bearing avoids the interference of outside aggressive factors. Meanwhile, foam concrete is poured into the pipe, so that the corrosion of the inner wall of the pipe pile caused by the invasion of underground water is prevented. The two components act together to ensure that the bearing capacity of the pile body is stable, all the performances do not decline, and the requirement on the durability of the pile body in an erosion environment is met. The sulfate erosion resistance of the underground concrete structure construction requirement can be met through preliminary tests.
(2) Can meet the underground environment with different sulfate erosion degrees.
According to the difference of the sulfate ion content of the underground environment, the requirements of the underground erosion environment with different degrees on the durability of the pile body can be met by reasonably designing the wall thickness of the outer wall of the protective layer formed by first centrifugal molding. I.e. the greater the concentration of aggressive media in the underground environment, the more aggressive the attack and the thicker the centrifugally formed outer wall should be.
(3) Reasonable structure combination form and high bearing capacity
The outer wall of the protective layer and the filled foam concrete which are centrifugally formed for the first time play a role in isolation and protection, and also play a role in lateral restraint on the prestressed reinforced concrete pipe body, so that the mechanical property of the pipe body can be better played when the pipe body bears pressure, and the mechanical bearing capacity of the pipe pile is obviously higher than that of an equivalent prestressed pipe pile through tests.
(4) High production efficiency, high quality and low cost
The invention is suitable for large-scale industrialized and mechanized production, and has the advantages of high production efficiency, high molding quality, convenient construction, good durability, durability and high economic value.
Detailed Description
The present invention will be described in further detail with reference to examples.
Embodiment 1 is applicable to the prestressing force tubular pile of underground sulfate erosion environment, and its body is the reinforced concrete body. And wrapping a fiber-reinforced polymer-based composite material protective layer on the outer surface of the pipe body, and filling hardened foam concrete into the pipe body.
The fiber-reinforced geopolymer-based composite material of the fiber-reinforced geopolymer-based composite material protective layer is composed of a powder material and organic fibers, wherein the fibers account for the powder material in percentage by mass: 5 percent.
The powder material comprises the following components in percentage by mass: 60% of granulated blast furnace slag micro powder; 20% of volcanic ash material; 10% of Portland cement; sodium silicate trigger (measured as Na2O contained therein) 8%.
The organic fiber is polypropylene fiber.
The granulated blast furnace slag micro powder is S95-grade granulated blast furnace slag micro powder, and is prepared by carrying out magnetic separation and iron removal on blast furnace granulated slag and grinding the slag to ensure that the specific surface area is more than or equal to 400 m2/kg, wherein the superfine granulated blast furnace slag micro powder with the particle size of less than 30 mu m accounts for more than 90% of the total mass.
The volcanic ash material is silica fume.
The sodium silicate excitant is sodium silicate regulated by sodium hydroxide, and has a modulus of 1.5 and a baume degree of 39 degrees.
The foam concrete is a novel light heat-insulating material containing a large number of closed air holes, which is formed by fully foaming a foaming agent in a mechanical mode through a foaming system of a foaming machine, uniformly mixing foam and cement slurry, then carrying out cast-in-place construction or mould forming through a pumping system of the foaming machine and carrying out natural maintenance.
The preparation process of the tubular pile of the embodiment is as follows:
step 1, adding water to prepare fiber-reinforced polymer-based composite material slurry according to the liquid-solid mass ratio = 0.3-0.5.
Step 2. preparation of sulfate erosion resistant pipe body
Placing a reinforcement cage in a centrifuge die; then, injecting fiber-reinforced geopolymer-based composite material slurry, wrapping a fiber-reinforced geopolymer-based composite material protective layer on the outer surface of the centrifugal casting pipe body, maintaining the centrifugal casting pipe body with a mould for a set time, and forming; and then distributing the concrete mixture of the pipe body, tensioning the prestressed tendons according to the construction process of the existing prestressed pipe pile, performing centrifugal molding again to obtain the sulfate erosion resistant pipe body, and maintaining and molding.
Step 3. core filling protection
After pile sinking on the construction site, foam concrete is filled into the sulfate erosion resistant pipe body, and the pipe pile is obtained after the foam concrete is hardened.
Example 2, essentially the same as example 1, except that: the fiber of the fiber-reinforced geopolymer-based composite material accounts for the mass percentage of the powder material as follows: 3 percent.
The powder material comprises the following components in percentage by mass: 50% of granulated blast furnace slag micro powder; 30% of volcanic ash material; 15% of Portland cement; sodium silicate trigger (measured as Na2O contained therein) 5%.
The organic fiber is polyacrylonitrile fiber, ultra-high molecular weight polyethylene fiber, polyvinyl alcohol fiber, polyester fiber or polyformaldehyde fiber.
The volcanic ash material is kaolin or fly ash.
The sodium silicate excitant is sodium silicate regulated by sodium hydroxide, the modulus of which is 1.0 and the baume degree of which is 37 degrees.
Example 3 is essentially the same as example 1, except that: the fiber-reinforced geopolymer-based composite material is composed of a powder material and organic fibers, wherein the fibers account for the powder material in percentage by mass: 8 percent.
The powder material comprises the following components in percentage by mass: 70% of granulated blast furnace slag micro powder; pozzolanic material 10%; 15% of Portland cement; sodium silicate trigger (measured as Na2O contained therein) 5%.
The sodium silicate excitant is sodium silicate regulated by sodium hydroxide, and has a modulus of 2.0 and a baume degree of 41 degrees.