A corrosion protection coating material for concrete pipes and a method of manufacture

Abstract

The application belongs to the technical field of concrete, and particularly discloses a kind of anticorrosive coating materials applied to concrete pipeline. It is made of raw materials with the following weight percentage: water 22.5%~23.0%, water glass 11.2%~13.2%, water supply aluminum sludge ash 6.4%~6.6%, and Portland cement 57.9%~59.2%. The application also discloses a preparation method of the anticorrosive coating material for concrete pipeline, including the following steps: (1) weighing each raw material according to the weight ratio; (2) mixing the water supply sludge ash and the dry Portland cement uniformly; (3) dissolving the water glass in water; (4) slowly pouring the prepared water glass solution into the mixture and stirring slowly, then stirring rapidly for 1 minute after uniform stirring, to obtain the pipeline anticorrosive coating material. The application has the advantages of energy saving and environmental protection, and the coating has excellent corrosion resistance, which can solve the problem of shortened service life of concrete pipeline caused by chemical corrosion and microbial corrosion inside the pipeline, and prolong the service life of municipal sewage pipeline.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of concrete, and particularly relates to a corrosion-resistant coating material applied to a concrete pipeline and a preparation method. BACKGROUND

[0002] The municipal pipeline construction in China is still being promoted, and the current municipal sewage pipeline network mainly adopts concrete pipelines. The inner wall surface of the concrete pipeline is rough, and is often in a closed and humid environment after being put into use, which is extremely suitable for microbial growth. Long time will cause the pipeline surface mortar to be damaged and fall off, the pipeline to be cracked, and the steel bars to be corroded, and the service life is far lower than the design life. SUMMARY

[0003] (I) Technical problems solved

[0004] In view of the deficiencies of the prior art, the application provides a corrosion-resistant coating material applied to a concrete pipeline and a preparation method, which solves the problem that the concrete pipeline in a closed and humid environment causes the pipeline surface mortar to be damaged and fall off, the pipeline to be cracked, and the steel bars to be corroded, and the service life is far lower than the design life due to microbial growth.

[0005] Compared with Portland cement, aluminate cement can better resist the corrosion of microorganisms in the sewage pipeline, and mainly has four corrosion-resistant protection barrier mechanisms: high neutralization acid capacity, aluminum-containing gel protection layer, inhibition of acid-producing bacteria activity, and high wear resistance. Among them, the high concentration of aluminum elements inhibits the activity of the biofilm, but the direct use of aluminate cement costs much higher than Portland cement.

[0006] Aluminate cement can solve the problem of corrosion of microorganisms in the sewage pipeline, but the high cost of aluminate cement compared with Portland cement is the reason hindering its commercial application. The coagulation process of the water supply plant in China mainly uses polyaluminum chloride (PAC), and the coagulation and sedimentation will produce water supply aluminum sludge with high aluminum content, the main components of which are aluminum oxide and silicon dioxide, similar to clay components, which can be classified as N type natural pozzolan. Therefore, it can be considered to replace part of the Portland cement with solid waste materials to improve the corrosion resistance of the material.

[0007] The application obtains a composite coating material with high aluminum content by replacing part of the Portland cement with pretreated water supply aluminum sludge, which realizes the resource utilization of sludge, reduces the use of Portland cement, reduces carbon emissions, and improves the corrosion resistance of the municipal sewage pipeline to prolong the service life. The application ensures that the content of the water supply aluminum sludge ash at least produces a corrosion-resistant effect, so that the water supply aluminum sludge ash is used to the maximum extent. Therefore, the ratio of the water supply aluminum sludge ash and the Portland cement composition needs to be calculated scientifically and reasonably to achieve the best economic effect.

[0008] (II) Technical Solution

[0009] The application provides a kind of anticorrosive coating material applied to concrete pipeline, and is committed to both realize the resource utilization of sludge, and can prolong the service life of municipal sewage pipeline.

[0010] To solve the above technical problems, the technical scheme adopted by the application is:

[0011] An anticorrosive coating material applied to concrete pipeline, characterized by being made of the following raw materials in percentage by weight: water 22.5%-23.0%, water glass 11.2%-13.2%, water treatment aluminum sludge ash 6.4%-6.6%, and Portland cement 57.9%-59.2%. 24 Al 22.79 O 96 H 76.8 , CaAl2Si2O8·H2O, Mg6Al2(OH) 16 CO3·4H2O high-polymerization C-A-H and C-A-S-H gel.

[0012] Further, the preferred percentage by weight of each raw material is: water 22.5%, water glass 13.2%, water treatment aluminum sludge ash 6.4%, and Portland cement 57.9%.

[0013] Further, the water is tap water, the water treatment aluminum sludge ash is obtained by mechanical dewatering and pretreatment of chemical flocculation sludge from a municipal tap water company sedimentation tank, the water glass is commercially available, and the Portland cement is commercially available.

[0014] Further, the pretreatment procedure of the water treatment sludge ash includes drying at 105°C for 24 hours, crushing by a crusher, passing through a 200-mesh screen, and calcining at 350°C. The main crystal phases in the aluminum-containing sludge after drying at 105°C are quartz, gibbsite, muscovite, and dolomite. After calcining at 350°C, the quartz diffraction peak shows a “hump” shape, indicating that the sludge particles contain a large amount of amorphous silicon dioxide, the diffraction peaks of kaolinite and mullite begin to appear, the carbonate product diffraction peak disappears, gibbsite is converted into aluminum oxide, and the total organic carbon of the sludge particles is significantly reduced, as shown in Table 1, and the reactivity of the sludge material is improved. Low-temperature calcination greatly reduces the influence of organic matter on the cement hydration process, and the aluminum phase material has better reactivity. In combination with the effect of the alkali activator, the aluminum-silicon phase material in the aluminum-containing sludge ash can be better activated.

[0015] Further, the calcining procedure at 350°C is as follows: heating for 60 minutes at a heating rate of about 5°C / min, maintaining at 350°C for 120 minutes, and naturally cooling down.

[0016] Further, the silicate cement is marked as 425, and the main detected particles of the cement are calcium sulfate dihydrate, tricalcium silicate and dicalcium silicate diffraction peaks.

[0017] Further, the modulus of the water glass is 1.0, and the purity is analytical pure.

[0018] Another aspect of the present application is to provide a preparation method of a corrosion-resistant coating material applied to a concrete pipe, characterized in that it comprises the following steps:

[0019] S1. Weigh each raw material according to the following weight ratio,

[0020] Water 22.5%~23.0%, water glass 11.2%~13.2%, water treatment sludge ash 6.4%~6.6%, silicate cement 57.9%~59.2%;

[0021] S2. Mix the dry water treatment sludge ash and silicate cement evenly;

[0022] S3. Dissolve the water glass in water;

[0023] S4. Slowly pour the prepared water glass solution into the mixture synthesized in step S2, and stir slowly for one minute, then stir quickly for one minute after stirring evenly, and then hydrate to obtain a pipe corrosion-resistant coating material.

[0024] The hydration process of the corrosion-resistant coating material is as follows: first, the water glass solution provides a certain amount of free silicon phase material, and also has free OH - After contacting with the cement particles and sludge particles (DWTS), the continuously precipitated free silicon and aluminum atoms and calcium ions react to form C-S-H / C-A-H / C-A-S-H gel hydration products, and the Ca / Si and Al / Si ratios of the coating material are reduced to promote the lengthening of the average chain length of C-A-S-H / C-A-H and improve the crystallinity, which is beneficial to the improvement of material density and corrosion resistance. The hydration reaction process during the preparation of the coating material is shown in equations 1-4.

[0025] Equation 1

[0026] Equation 2

[0027] Equation 3

[0028] Equation 4

[0029] (Three) beneficial effects

[0030] (1) The coating material of the present application presents strong alkalinity, mainly because a certain amount of alkali activator is put in during preparation, and Ca(OH)2 crystals are generated during curing of the coating material. When the coating is applied to a sewage pipe environment, a certain amount of alkaline substances will first be precipitated, constantly maintaining the surface pH of the coating to inhibit the growth and reproduction of acidophilic sulfur-oxidizing bacteria. Secondly, the water supply sludge ash is introduced as a supplementary cementitious material to introduce more aluminum phase substances, and more C-A-H and C(Na)-A-S-H hydration gel products are generated during hydration. The decomposition of this kind of hydration product will form Al(OH)3 acid-resistant gel, which can better inhibit the penetration of acid corrosion solution, and after the barrier fails, aluminum ions will penetrate into the surface biofilm, and after the accumulation of time, it has the ability to inhibit the acid production of sulfur-oxidizing bacteria. Therefore, the coating material can prolong the formation time of the biofilm inside the sewage pipe and inhibit the growth of bacteria with corrosion effect, prolonging the service life of the pipe.

[0031] (2) The present application uses water supply aluminum sludge to replace part of the cement to prepare the coating material, without introducing heavy metal ions, which will not affect the subsequent sewage treatment process and has little pollution to the environment.

[0032] (3) The present application uses water supply aluminum sludge as raw material, which reduces the pressure of sludge treatment in water treatment plants, realizes the resource utilization of sludge, and the pretreatment method of low-temperature calcination is more green and environmentally friendly.

[0033] (4) The raw materials are easy to obtain and can be locally sourced; the process is simple, industrialized production can be realized, has good stability and corrosion resistance, and has a broad market prospect. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a schematic diagram of each component of the present application;

[0035] Figure 2 is a schematic diagram of the application effect of the coating of the present application.

[0036] Figure 3 is the XRD diffraction pattern of the silicate cement particles, 105℃ dried sludge and 350℃ calcined sludge of the present application.

[0037] Figure 4 is the XRD diffraction image of the coating material of the present application cured for 7 days and 28 days.

[0038] Figure 5 is the thermogravimetric curve of the coating material of the present application after curing for 28 days.

[0039] Figure 6 is the surface pH change graph of the coating acid corrosion process of the present application.

[0040] Figure 7is a diagram of the concentration change of calcium ions in the acid solution in the coating acid corrosion process of the application.

[0041] Figure 8 is a diagram of the concentration change of aluminum ions in the acid solution in the coating acid corrosion process of the application.

[0042] In the figure: 1 - water supply sludge ash; 2 - Portland cement; a - sewage concrete pipeline; b - coating material. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the application will be apparently and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0044] Please refer to Figures 1-8 A kind of anticorrosive coating material applied to concrete pipeline is made of the following raw materials by weight percentage: water 22.5%-23.0%, water glass 11.2%-13.2%, water supply sludge ash 6.4%-6.6%, Portland cement 57.9%-59.2%.

[0045] In the application, the water is tap water, which is convenient to obtain and low in cost. The tap water can adjust the workability and stability of the mixture and prevent the mixture from appearing flash setting due to the too low content of tap water, which leads to the high pH of water glass solution.

[0046] The water supply sludge ash 1 is obtained after a series of pretreatments and is the residual sludge generated after coagulation treatment in a water supply plant. The water supply sludge ash is dewatered by a belt filter, dried, crushed, sieved, and calcined at 350℃ to obtain a solid waste with certain pozzolanic activity. The main components of the water supply sludge ash are SiO2 and Al2O3, which have certain pozzolanic activity and can be used as a supplementary cementitious material of Portland cement under the action of an alkali activator.

[0047] Table 1 Total organic carbon content of sludge particles

[0048]

[0049] The Portland cement 2 is a commercially available grade, which is made of clay and limestone as raw materials, calcined at high temperature to obtain clinker with calcium silicate as the main component, and then ground with 0%-5% of mixed materials and an appropriate amount of gypsum to obtain a hydraulic cementitious material. The grade is 425, the main mineral components are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite, which have good cementitious properties, and the strength is ≥42.5MPa after 28 days of curing. The composition of the Portland cement and the water supply sludge ash is shown in Table 1.

[0050] Table 2 Cement and sludge particle XRF composition analysis table

[0051]

[0052] The water glass is provided by Tianjin Kemio Chemical Reagent Co., Ltd., which is ISO9001 international quality management system certified, and the molecular formula is Na2SiO3·5H2O, the relative molecular mass is 212.14, and the modulus is 1.03±0.03.

[0053] The application is described in detail through the following examples.

[0054] Example

[0055] The weight percentage of each component of the concrete pipeline anticorrosion coating material in examples 1 and 2 is shown in table 3.

[0056] Table 3 Weight percentage of each component of the concrete pipeline anticorrosion coating material

[0057]

[0058] The preparation method of the concrete pipeline anticorrosion coating material described in examples 1 and 2 comprises the following steps:

[0059] (1) The tap water, water glass, water supply aluminum sludge ash and portland cement are weighed according to the weight ratio of each component and prepared for use;

[0060] (2) The dry materials of water supply aluminum sludge ash and portland cement are put into the mixing site for dry mixing, which can be assisted by manual mixing to ensure uniform mixing of the dry materials;

[0061] (3) The water glass is dissolved in water to ensure complete dissolution;

[0062] (4) The prepared water glass solution is slowly poured and slowly stirred for one minute, and then quickly stirred for one minute after uniform stirring, to obtain the pipeline anticorrosion coating material.

[0063] The coating material prepared in examples 1 and 2 is covered on the surface of the sewage concrete pipeline a, and is placed in a curing box to maintain T=20℃±2℃, RH≥95% for 28 days, to obtain the anticorrosion coating b.

[0064] The cured coating material is soaked in a sulfuric acid solution, and 98% concentrated sulfuric acid is selected, and 1% of the solvent mass of sulfuric acid is added, that is, 1g of concentrated sulfuric acid is added to 100g of water to prepare an acid corrosion solution, and the solution is soaked at a ratio of solution volume: test block volume = 10:1, and the solution is replaced every 7 days, and the test blocks without coating and with coating are soaked for 90 days.

[0065] Table 4 Mass loss rate (%) of concrete pipe and coating material after 90 days of corrosion

[0066]

[0067] As can be seen from Table 4, the mass loss rate of the test block with coating protection is significantly less than that of the ordinary Portland cement test block, which shows that the coating material can improve the acid corrosion resistance of the pipe material.

[0068] Figure 6 The surface pH change curve of the test block soaked for 90 days with or without coating is shown in the figure. It can be seen from the figure that the surface pH of Example 2 is higher than that of the ordinary concrete sewage pipe test block, and can still remain at about 4 after 90 days of corrosion. The pH value is still at the minimum pH value for inhibiting the growth and reproduction of sulfur-oxidizing bacteria.

[0069] Figure 7 and Figure 8 respectively are the changes of calcium ion and aluminum ion concentration of the corrosion solution after 90 days of corrosion. As can be seen from the figure, with the extension of corrosion time, the ordinary concrete sewage pipe test block continuously erodes the C-S-H gel and AFt crystal on the surface of the test block, and the concentration of calcium ion and aluminum ion continuously increases. The overall precipitation amount of calcium ion of the test block coated with Example 2 is less than that of the ordinary concrete sewage pipe test block during the corrosion process, and the concentration of aluminum ion is maintained at about 40 mg / L from 35 to 63 days. This is mainly because the C-A-H and C(Na)-A-S-H hydrated gel products on the surface of the coating continuously decompose and precipitate aluminum ion, and the aluminum ion enrichment forms an acid-resistant barrier of Al(OH)3gel, which inhibits the acid corrosion process. When the corrosion time is 70 days, the concentration of aluminum ion rapidly rises, at which time the acid-resistant barrier loses its effect, and a large amount of aluminum ion is released into the corrosion solution.

[0070] The present invention has the following main features in terms of performance: (1) Improves the corrosion resistance and service life of concrete pipes in municipal sewage pipe networks. The anti-corrosion coating material is strongly alkaline. During the corrosion process, a certain amount of alkaline substances can be released on the surface to neutralize the acid corrosion, and a relatively high pH value can be maintained to inhibit the growth and reproduction of acidophilic sulfur oxidizing bacteria, thereby slowing down the corrosion process of concrete pipes and extending the service life of pipes. (2) Realizes the resource utilization of water supply sludge. The anti-corrosion coating material selects the residual water supply sludge produced by the municipal water supply plant treatment process as a supplementary cementing material. Currently, its treatment is mainly landfill, which will cause certain harm to the environment. This invention can reduce the pressure of water supply plant to treat sludge and realize the resource utilization of sludge. Compared with the pretreatment method of obtaining aluminum-containing sludge ash with higher activity by high-temperature calcination, the form of low-temperature calcination combined with alkaline activator is more green and environmentally friendly. (3) Non-toxic. The main components of water supply sludge are alumina and silicon dioxide. No heavy metal ions are introduced. Even if corrosion occurs after application, no toxic or harmful substances are released. It will not affect the subsequent sewage treatment process and has basically no pollution to the environment. (4) Not limited by geographical location. The current urbanization process has resulted in large water supply plants in all prefecture-level cities, and most of them use PAC as a coagulant. Therefore, sludge raw materials are readily available and produced in large quantities, and can be sourced locally, with broad market prospects.

[0071] Compared to traditional concrete materials, this invention uses sewage sludge as a supplementary cementing material, making it green and environmentally friendly, low in cost, and significantly improving stability and corrosion resistance. Furthermore, the raw material composition is simple, the process is easy, and construction is convenient.

[0072] This invention is not limited by geographical location, has broad market prospects, and is suitable for large-scale production. Besides applying this coating material to municipal sewage pipes, it can also be applied to concrete structures in sewage treatment plants and some acid-resistant environments, thereby extending the service life of materials or equipment.

[0073] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

[0074] It should be noted that, in this document, terms such as "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0075] While embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and variations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A corrosion protection coating material for concrete pipes, characterized in that, The corrosion-proof coating material is made of raw materials with the following weight percentages: water 22.5%-23.0%, water glass 11.2%-13.2%, water treatment aluminum sludge ash 6.4%-6.6%, and silicate cement 57.9%-59.2%; the corrosion-proof coating material contains Ca 24 Al 22.79 O 96 H 76.8 , CaAl2Si2O8·H2O, Mg6Al2(OH) 16 CO3·4H2O high-polymerization C-A-H and C-A-S-H gel; the water is tap water, the water treatment aluminum sludge ash is obtained by mechanical dehydration and pretreatment of chemical flocculation sludge from a municipal tap water company sedimentation tank, the water glass is commercially available, and the silicate cement is commercially available; the pretreatment procedure of the water treatment aluminum sludge ash includes drying at 105°C for 24 hours, crushing by a crusher, passing through a 200-mesh screen, calcining at 350°C, and calcining at 350°C, wherein the calcining procedure at 350°C is as follows: heating for 60 min at a heating rate of about 5°C / min, maintaining at 350°C for 120 min, and naturally cooling down.

2. The anticorrosive coating material for concrete pipes according to claim 1, characterized by, The raw materials are prepared by the following weight percentages: water 22.5%, water glass 13.2%, water treatment aluminum sludge ash 6.4%, and Portland cement 57.9%.

3. The anticorrosive coating material for concrete pipes according to claim 1, characterized by: The Portland cement is marked as 425.

4. The anticorrosive coating material for concrete pipes according to claim 3, characterized by: The water glass modulus is 1.0, and the purity is analytical pure.

5. The method of claim 1, wherein the anticorrosive coating material for concrete pipes is prepared by mixing 100 parts by weight of the anticorrosive coating material for concrete pipes according to claim 1, 0.1 to 10 parts by weight of a curing agent, and 0.1 to 10 parts by weight of a catalyst. The method comprises the following steps: S1. The raw materials are weighed according to the following weight ratio, water 22.5%-23.0%, water glass 11.2%-13.2%, water treatment aluminum sludge ash 6.4%-6.6%, and Portland cement 57.9%-59.2%; S2. The water treatment aluminum sludge ash and the Portland cement are mixed evenly; S3. The water glass is dissolved in water; S4. The prepared water glass solution is slowly poured into the mixture prepared in step S2, and stirred slowly for one minute, then stirred quickly for one minute, and the corrosion-proof coating material for concrete pipes is obtained by hydration.

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