Modified mortar coating material for corrosion prevention of sewage concrete pipeline and preparation method of modified mortar coating material

Abstract

The invention belongs to the technical field of sewage concrete pipelines, and discloses a modified mortar coating material for corrosion prevention of a sewage concrete pipeline and a preparation method of the modified mortar coating material. The preparation method comprises the following steps: weighing raw materials according to a preset ratio; uniformly mixing the weighed water supply aluminum sludge ash and the Portland cement dry material to obtain a dry material A; mixing the weighed water, water reducing agent and nano aluminum oxide, and performing water bath ultrasonic treatment to obtain a mixed solution B; and pouring the mixed solution B into the dry material A, stirring, adding tributyl phosphate, and hydrating to obtain the modified mortar coating material. According to the technical scheme, resource utilization of the water supply sludge can be achieved, the service life of the municipal sewage concrete pipeline can be prolonged, and the problems that in the warm and humid environment, due to the fact that microorganisms produce acid, mortar on the surface of the pipeline is damaged and falls off, the pipeline cracks, and steel bars are corroded are effectively solved. And the service life is far lower than the designed service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage concrete pipes, and in particular relates to a modified mortar coating material for sewage concrete pipe corrosion prevention and a preparation method thereof. Background Art

[0002] Currently, urban sewage pipes are predominantly constructed of concrete, and the total length of these pipes continues to grow. The warm and humid environment inside these pipes allows for the growth of microorganisms rich in organic and inorganic nutrients. Sulfur-oxidizing bacteria, in particular, produce biosulfuric acid, which irreversibly corrodes the concrete pipe walls. Over time, this can lead to surface mortar breakage, cracking, and even collapse, causing the pipes to operate far below their designed lifespan.

[0003] When it comes to corrosion protection for sewage concrete pipes, aluminate cement offers superior resistance to microbial corrosion compared to Portland cement. This is primarily due to its four corrosion barrier mechanisms: high acid neutralization capacity, an aluminum-containing gel protective layer, inhibition of acid-producing bacteria, and high wear resistance. In particular, the release of high concentrations of aluminum can inhibit biofilm activity. However, the significantly higher cost of using aluminate cement directly compared to Portland cement has hindered its commercial application. It is worth noting that the coagulation process currently primarily utilizes polyaluminum chloride (PAC), which produces high-aluminum aluminum sludge after coagulation and sedimentation (for illustrative purposes, its main components are alumina and silica, similar to clay, and can be classified as Class N natural pozzolan). Therefore, replacing some Portland cement with solid waste materials to improve the material's corrosion resistance, while also achieving resource utilization of the sludge and reducing carbon emissions to contribute to carbon neutrality, has become a pressing technical challenge. Summary of the Invention

[0004] The present invention aims to provide a modified mortar coating material for corrosion protection of sewage concrete pipes and its preparation method, thereby resolving one or more of the aforementioned technical problems. The technical solution disclosed in the present invention not only achieves resource utilization of water supply sludge but also extends the service life of municipal sewage concrete pipes. This effectively addresses the technical problem of sewage concrete pipes in warm and humid environments, where microbial growth and acid production lead to surface mortar damage and loss, cracking of the pipes, and corrosion of steel bars, resulting in a service life far below the designed lifespan.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for preparing a modified mortar coating material for corrosion protection of sewage concrete pipes, comprising the following steps: Weigh the raw materials according to the preset ratio; wherein, the mass ratio of the aluminum sludge ash, silicate cement, and nano-alumina is (14.25-14.85): (80.75-84.15): (1-5); in addition, weigh water according to a ratio of 35% of the total mass of the aluminum sludge ash, silicate cement, and nano-alumina, weigh a water reducer according to a ratio of 1% of the total mass of the aluminum sludge ash, silicate cement, and nano-alumina, and weigh tributyl phosphate according to a ratio of 0.01% of the total mass of the aluminum sludge ash, silicate cement, and nano-alumina; The weighed aluminum sludge ash from the water supply and the Portland cement dry material were mixed evenly to obtain dry material A; the weighed water, water reducer and nano-alumina were mixed and subjected to water bath sonication to obtain mixed solution B; Pour the mixed liquid B into the dry material A while stirring and adding tributyl phosphate to hydrate to obtain a modified mortar coating material.

[0006] A further improvement of the preparation method of the present invention is that the hydration process includes: nano-alumina serves as crystal nuclei, and silicate cement particles and water supply aluminum sludge ash sludge particles wrap the nano-alumina, which continuously precipitates free calcium, aluminum and silicon atoms upon contact with water to generate Ca(OH)2, ettringite and CSH / CASH gel hydration products; wherein the water supply aluminum sludge ash sludge particles are used to increase the Al atom content in the hydration product and promote the formation of CASH gel; the nano-alumina is used to fill the gaps between cements, promote the formation of CASH gel, increase the main chain length and improve the degree of polymerization.

[0007] A further improvement of the preparation method of the present invention is that the hydration process equation is: , , , .

[0008] A further improvement of the preparation method of the present invention is that the modified mortar coating material contains CASH gel with a main chain length of 6.01 and an Al[IV] / Si of 0.0639.

[0009] A further improvement of the preparation method of the present invention is that the water supply aluminum sludge ash is obtained by mechanically dehydrating, drying and pre-treating the chemical flocculation sludge in the sedimentation tank of the municipal water company.

[0010] A further improvement of the preparation method of the present invention is that the steps of mechanical dehydration, drying and pretreatment include: drying first, then crushing and screening with a crusher, and finally calcining at 800°C.

[0011] A further improvement of the preparation method of the present invention is that the step of calcining at 800°C specifically includes: starting from room temperature, heating to 800°C at a heating rate of 5°C / min and maintaining for 120 minutes, and then cooling naturally.

[0012] A further improvement of the preparation method of the present invention is that in the steps of drying first, crushing with a crusher and screening, the drying is carried out at a temperature of 105° C., and the screening is carried out through a 200-mesh sieve.

[0013] A further improvement of the preparation method of the present invention is that the water is tap water; the nano-alumina, the water reducer, the tributyl phosphate, and the silicate cement are all commercially available; The average particle size of the nano-alumina is ≤50nm, and the specific surface area is >160m 2 / g, bulk density is 190g / cm 3 , purity ≥99.99%, crystal form is γ phase; the silicate cement grade is 425.

[0014] In a second aspect, the present invention provides a modified mortar coating material for corrosion protection of sewage concrete pipes, which is prepared by the preparation method described in any one of the first aspects of the present invention.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention specifically discloses a method for preparing a modified mortar coating material for corrosion protection of sewage concrete pipes. This method not only realizes the resource utilization of water supply sludge, but also extends the service life of municipal sewage concrete pipes. The prepared product effectively solves the technical problem that sewage concrete pipes in warm and humid environments, due to the growth of microorganisms and acid production, lead to the damage and shedding of mortar on the pipe surface, cracking of the pipe, and rusting of steel bars, resulting in a service life far below the design life. Specifically, in the early stage of cement hydration, due to the large specific surface area of nano-alumina and its stronger adsorption effect, it can provide more nucleation sites. Cement and sludge ash particles will hydrate around the nano-alumina, accelerating the hydration reaction rate. In addition, nano-alumina can absorb free water in the cement slurry, thereby increasing the water demand of the modified mortar coating material. This effect can make the cement in the modified mortar coating material more fully hydrated, thereby increasing the strength of the modified mortar coating material. As a nanomaterial, nano-alumina can effectively fill the tiny pores between cement and sludge particles, reduce the number of capillary harmful pores, reduce the average pore size, and improve the density of concrete. The active SiO2 and Al2O3 in aluminum sludge ash react with the hydration product Ca(OH)2 in cement to form secondary hydration products such as calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH), which can improve the later strength and durability of cement concrete. It is important to emphasize that the present invention's coating material, which uses aluminum sludge and nano-alumina to replace part of the cement, does not introduce heavy metal ions, will not affect subsequent wastewater treatment processes, and is essentially environmentally friendly.

[0016] This invention uses aluminum sludge from water supply plants as raw material, alleviating the burden of sludge treatment at water plants and achieving resource utilization. The pretreatment method, calcined at 800°C, is environmentally friendly and closely aligned with my country's current efforts to promote high-quality ecological progress. Furthermore, the raw materials are readily available and can be sourced locally; the process is simple, enabling industrialized production. The product exhibits excellent stability and corrosion resistance, and has broad market prospects. Further explaining this, pozzolanic activity test results and cement hydration characteristics analysis indicate that when DWTS is treated below 400°C, its high organic matter content inhibits hydration, resulting in poor pozzolanic activity. Within the 400°C to 600°C range, DWTS is suitable as a supplementary cementitious material in cement hydration. Within this temperature range, amorphous SiO2 participates in hydration, forming CSH in an alkaline environment. Due to dehydroxylation at 600°C, the sludge exhibits higher reactivity than at 400°C. 800°C is the optimal heat treatment temperature, as the sludge contains a large amount of poorly crystallized γ-Al2O3 and amorphous SiO2, which participate in hydration to form CASH as the primary component. Further illustrating this, between 1000°C and 1200°C, γ-Al2O3 converts to α-Al2O3 upon calcination, combining with SiO2 to form stable mullite, which serves solely as a filler in the DWTS-cement cementitious system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below; obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of the components of the present invention.

[0019] Figure 2 This is a schematic diagram of the coating application effect of the present invention; wherein a is a sewage concrete pipe and b is an anti-corrosion coating.

[0020] Figure 3 This is the XRD diffraction pattern of the nano-alumina of the present invention.

[0021] Figure 4 The invention discloses an XRD diffraction pattern of the water supply aluminum sludge ash after calcination at 800°C.

[0022] Figure 5 These are the XRD diffraction images of the coating material of the present invention after curing for 1 day, 7 days and 28 days.

[0023] Figure 6It is a schematic diagram of the change of calcium ion concentration in the acid solution during the acid corrosion process of the coating of the present invention.

[0024] Figure 7 It is a schematic diagram of the change of aluminum ion concentration in the acid solution during the acid corrosion process of the coating of the present invention.

[0025] The explanations of the reference numerals in the figures are as follows: 1. nano-alumina; 2. silicate cement; 3. water supply aluminum sludge ash. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments and technical solutions are only part of the embodiments of the present invention, not all of the embodiments.

[0027] All other embodiments obtained by persons of ordinary skill in the art based on the technical solutions disclosed in the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, products, or apparatuses.

[0028] See also Figure 1 and Figure 2 An embodiment of the present invention provides a modified mortar coating material for sewage concrete pipe corrosion protection, comprising nano-alumina (1), Portland cement (2), and water supply aluminum sludge ash (3). The specific raw material ratio is as follows: the mass ratio of water supply aluminum sludge ash, Portland cement, and nano-alumina is (14.25-14.85): (80.75-84.15): (1-5). In addition, water is weighed to 35% of the total mass of the water supply aluminum sludge ash, Portland cement, and nano-alumina; a water reducer is weighed to 1% of the total mass of the water supply aluminum sludge ash, Portland cement, and nano-alumina; and tributyl phosphate is weighed to 0.01% of the total mass of the water supply aluminum sludge ash, Portland cement, and nano-alumina. In a further preferred technical solution, the modified mortar coating material comprises a high-polymerization CASH gel (calcium aluminum silicate hydrate gel) with a main chain length of 6.01 and an Al[IV] / Si ratio of 0.0639. In a specific exemplary technical solution, when the coating material is applied, the coating material is applied to the surface of the sewage concrete pipe a to form an anti-corrosion coating b, such as Figure 2 shown.

[0029] Explanatory note: Compared to Portland cement, aluminate cement offers better resistance to microbial corrosion in sewage pipes. It possesses four key corrosion protection mechanisms: high acid neutralization capacity, an aluminum-containing gel protective layer, inhibition of acid-producing bacteria, and high wear resistance. The primary mechanism is the release of high concentrations of aluminum, which inhibits biofilm activity. However, the cost of using aluminate cement directly is significantly higher than that of Portland cement. While aluminate cement can address microbial corrosion in sewage pipes, its higher cost hinders its commercial application. The technical solution of the present embodiment replaces part of the Portland cement with solid waste materials to improve the material's corrosion resistance. Further illustrative note: The coating material in the present embodiment exhibits improved density, primarily due to the addition of a small amount of nano-alumina during the preparation process. This fills the gaps between cement and sludge particles through a filling action, while also promoting hydration, resulting in a longer main chain length CASH gel with a higher degree of polymerization than CSH gel. This significantly improves overall density and reduces permeability, making it more difficult for microbial acids in sewage concrete pipes to penetrate the concrete. In addition, the aluminum provided by the water supply aluminum sludge ash and nano-alumina helps to inhibit the growth of microorganisms on the surface of sewage concrete pipes. In view of the above factors, the coating material of the embodiment of the present invention can prolong the formation time of the biofilm inside the sewage pipe and inhibit the growth of bacteria with corrosive effects, thereby extending the service life of the pipe. It should be emphasized that the technical solution of the embodiment of the present invention replaces part of the cement with water supply aluminum sludge to prepare the coating material without introducing heavy metal ions, which will not affect the subsequent sewage treatment process and is basically pollution-free to the environment. The embodiment of the present invention uses water supply aluminum sludge as raw material, which reduces the pressure on the water supply plant to treat sludge and realizes the resource utilization of sludge. In the technical solution of the embodiment of the present invention, the raw materials are easy to obtain and can be obtained locally; the process is simple, and industrial production can be realized. It has good stability and corrosion resistance and has broad market prospects.

[0030] In the technical solution of the embodiments of the present invention, pretreated aluminum sludge from water supply replaces part of the Portland cement to produce a high-aluminum composite coating material. This not only achieves resource utilization of the sludge, but also reduces the use of Portland cement, reducing carbon emissions and achieving carbon neutrality. It also improves the corrosion resistance of municipal sewage pipes, thereby extending their service life. While ensuring that the content of aluminum sludge ash from water supply is at least sufficient to produce an anti-corrosion effect, the present invention maximizes the use of aluminum sludge ash from water supply, and the ratio of aluminum sludge ash to Portland cement components is scientifically and rationally calculated to achieve optimal economic results.

[0031] As a preferred embodiment of the present invention, the water is tap water, the aluminum sludge ash from the water supply is obtained by mechanical dehydration, drying and pretreatment of chemical flocculation sludge from the municipal water company's sedimentation tank, the nano-alumina, water reducer and tributyl phosphate are commercially available, and the silicate cement is commercially available. In a specific exemplary technical solution, the pretreatment procedure for the aluminum sludge ash from the water supply includes drying at 105°C for 24 hours, crushing with a crusher, passing through a 200-mesh sieve, and calcining at 800°C. The main crystalline phases in the aluminum-containing sludge after drying at 105°C are quartz, gibbsite, muscovite and dolomite. After activation by calcination at 800°C, the bimodal structure of the albite begins to change. In addition, the muscovite is dehydrated and dehydroxylated, decomposing into Al2O3 and SiO2. The total organic carbon of the sludge particles is significantly reduced, and the reactivity of the sludge material is improved. Calcination significantly reduces the impact of organic matter on cement hydration and enhances the reactivity of aluminum phases. Combined with the action of an alkaline activator, this can further activate the aluminum-silicon phases in aluminum-containing sludge ash. In a specific exemplary technical solution, the 800°C calcination procedure involves starting from room temperature, increasing the temperature at a rate of 5°C / min to 800°C, holding for 120 minutes, and then cooling naturally.

[0032] In the embodiment of the present invention, the silicate cement is graded 425, and the main diffraction peaks detected in the cement particles are calcium sulfate dihydrate, tricalcium silicate and dicalcium silicate. The average particle size of nano-alumina is ≤50nm, and the specific surface area is >160m 2 / g, bulk density = 190g / cm 3 , purity is 99.99%, and the crystal form is γ phase.

[0033] An embodiment of the present invention provides a method for preparing a modified mortar coating material for sewage concrete pipe corrosion prevention, comprising the following steps: The raw materials were weighed according to a preset ratio; wherein the mass ratio of water, aluminum sludge ash from water supply, Portland cement, nano-alumina, and water reducer was 35: (14.25-14.85): (80.75-84.15): (1-5): 1; in addition, tributyl phosphate was weighed in a ratio of 0.01% of the total mass of aluminum sludge ash from water supply, Portland cement, and nano-alumina; The weighed aluminum sludge ash from the water supply and the Portland cement dry material were mixed evenly to obtain dry material A; the weighed water, water reducer and nano-alumina were mixed and subjected to water bath sonication to obtain mixed solution B; Pour the mixed solution B into the dry material A, stir, and add tributyl phosphate at the same time to hydrate to obtain a modified mortar coating material; Among them, water is tap water, which is easy to obtain and low in cost. Tap water can adjust the workability and stability of the mixture; tributyl phosphate acts as a defoaming agent, which can prevent the generation of bubbles during hydration and cause harmful pores in concrete; nano-alumina is of commercial grade, and its physical and chemical properties can be seen in Table 1.

[0034] Table 1. Main properties of nano-alumina

[0035] Aluminum sludge from the Xi'an Qujiang Water Plant is obtained after a series of pretreatments. This is the residual sludge generated after the waterworks' coagulation treatment. It is dehydrated and discharged through a belt filter press. After drying, crushing, screening, and calcination at 800°C, the resulting solid waste exhibits a certain degree of pozzolanic activity. Its main components are SiO2 and Al2O3. See Table 2 for details.

[0036] Table 2. Total organic carbon content of sludge particles

[0037] Commercially available Portland cement is made from clay and limestone, calcined at high temperature to produce a clinker primarily composed of calcium silicate. 0% to 5% of mixed materials and an appropriate amount of gypsum are added to the ground cement to create a hydraulic binder. The main mineral components are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite. It exhibits excellent cementing properties and a strength of 42.5 MPa or higher after 28 days of curing. The composition of Portland cement and aluminum sludge ash from water supply is shown in Table 3.

[0038] Table 3. XRF composition analysis of cement and sludge particles

[0039] The water reducer is PCEA polycarboxylic acid high-performance water reducer produced by Jiangsu Subote New Materials Co., Ltd., with a solid content of 20% and a water reduction rate of about 30%.

[0040] In the specific embodiments of the present invention, the weights of the components of the modified mortar coating materials in Examples 1, 2, and 3 are shown in Table 4.

[0041] Table 4. Weight of each component of modified mortar coating material

[0042] In Examples 1, 2, and 3, the method for preparing the anti-corrosion coating material for concrete pipes comprises the following steps: (1) Weigh the raw materials according to the weight in Table 4; (2) Mix the aluminum sludge ash from water supply and the dry material of Portland cement evenly; (3) Mix water, water reducer and nano-alumina and ultrasonicate in a water bath for 10 min; (4) After the ultrasonic treatment, the mixture was slowly poured into the dry material and stirred slowly while adding tributyl phosphate. The mixture was stirred at a low speed of 125 rpm for 3 min and then stirred at a high speed of 250 rpm for 1 min to obtain the pipeline anti-corrosion coating material.

[0043] The coating material prepared in the above embodiment is covered on the surface of the sewage concrete pipe a, and placed in a curing box to maintain T = 20 ° C ± 2 ° C, RH ≥ 95% for 28 days to obtain an anti-corrosion coating b; illustratively, as Figure 2 shown.

[0044] Table 5. Coating materials 29 Si NMR spectrum fitting results

[0045] As can be seen from Table 5, Q 2b The appearance of (1Al)-silicon tetrahedra is attributed to the substitution of active Al from the aluminum sludge ash and nanoalumina for Si in the Q2b-silicon tetrahedra. These results demonstrate that the addition of aluminum sludge ash and nanoalumina to cement hydration promotes the formation of CASH gels. Compared to Example 3, the increased backbone length (MCL) and Al[IV] / Si ratio in Example 1 indicate greater aluminum absorption at bridging sites. This also suggests a higher degree of polymerization of the silica tetrahedra, which underpins the improved mechanical properties of the C-(A)-SH gel.

[0046] The cured coating material was immersed in a sulfuric acid solution. Concentrated sulfuric acid with a mass fraction of 98% was selected and added at 1% of the solvent mass. That is, 1 g of concentrated sulfuric acid was added to 100 g of water to prepare an acid corrosion solution. The solution volume: specimen volume = 10:1 was used for immersion. The solution was replaced every 7 days. The uncoated and coated specimens were immersed for 56 days at the same time. The measured mass loss rate is shown in Table 6.

[0047] As can be seen from Table 6, the mass loss rate of the test block protected by the coating is significantly lower than that of the ordinary Portland cement test block, indicating that the coating material can improve the acid corrosion resistance of the pipeline material.

[0048] Table 6 Mass loss rate of concrete pipes and coating materials after 56 days of corrosion (%)

[0049] See also Figure 3 , Figure 3 This is the XRD diffraction pattern of nano-alumina. In the XRD pattern, characteristic diffraction peaks 2θ=30.99°, 37.05°, 39.47°, 45.56°, and 67.32°, indicating that the crystal form of the alumina is γ phase.

[0050] See also Figure 4 , Figure 4This is the XRD diffraction pattern of the water supply aluminum sludge ash after calcination at 800°C. After activation by calcination at 800°C, Al2O3 crystals transform into less crystalline γ-Al2O3 and crystalline SiO2 transforms into amorphous, increasing the amorphous content of the water supply aluminum sludge ash to 63.31%. Sodium feldspar has a bimodal structure (albite high on the left, albite low on the right). When the temperature rises above 800°C, the bimodal structure shifts from the albite low diffraction peak to the albite high peak as the dominant peak. This indicates that the crystal structure of the water supply aluminum sludge undergoes a fundamental change at 800°C.

[0051] See also Figure 5 , Figure 5 The XRD diffraction images of the coating material of the present invention after curing for 1 day, 7 days and 28 days are shown in the figure, and the test range of 2θ is 5°~75°. Figure 5 As can be seen from the results, compared to ordinary concrete, the samples in Examples 1 and 2 did not exhibit any new diffraction peaks, indicating that the addition of NA to the modified cement did not result in the formation of new hydration products. After hydration of the modified cement for one and seven days, the peak intensity of tricalcium silicate (C3S) in ordinary concrete, Examples 1, and 2 gradually decreased with increasing NA content in the modified cement. Furthermore, the peak intensity of calcium hydroxide (Portlandite) at 2θ = 18.02° increased with increasing NA content in the modified cement. C3S, the main component of cement, reacts chemically upon contact with water to form CSH gel and calcium hydroxide. This suggests that the NA in the modified cement accelerates the early hydration reaction of cement. This is because in the early stages of cement hydration, NA acts as nucleation sites, known as "crystal nuclei," promoting the formation of hydration products.

[0052] See also Figure 6 and Figure 7 , Figure 6 and Figure 7 The graph shows the changes in calcium and aluminum ion concentrations in the corrosion solution after 56 days of corrosion. As can be seen from the figure, as the corrosion time of the ordinary concrete sewage pipe test block increases, the sulfuric acid solution continuously erodes the CSH gel and AFt crystals on the surface of the test block, and the concentrations of calcium and aluminum ions continue to increase. However, the overall precipitation of calcium and aluminum ions during the corrosion process of the test blocks coated with Examples 1 and 2 is less than that of the ordinary concrete sewage pipe test block. This is mainly because the CAH and CASH hydration gel products on the coating surface continuously decompose and precipitate aluminum ions, and the aluminum ions are enriched to form an acid-resistant barrier of Al(OH)3 gel, which inhibits the acid corrosion process.

[0053] Specifically and exemplarily, an embodiment of the present invention further provides a method for preparing a modified mortar coating material for corrosion protection of sewage concrete pipes, comprising the following steps: Weigh the raw materials according to a preset ratio; wherein the mass ratio of water, aluminum sludge ash from water supply, Portland cement, nano-alumina, and water reducer is 35:14.5:82:3.5:1; in addition, weigh tributyl phosphate at a ratio of 0.01% of the total mass of aluminum sludge ash from water supply, Portland cement, and nano-alumina; and evenly mix the aluminum sludge ash from water supply and the Portland cement dry materials to obtain dry material A; Mixing water, a water reducing agent and nano-alumina and subjecting the mixture to ultrasonic treatment in a water bath to obtain a mixed solution B; Pour the mixed liquid B into the dry material A while stirring and adding tributyl phosphate to hydrate to obtain a modified mortar coating material.

[0054] The hydration process includes: nano-alumina as crystal nucleus, silicate cement particles and sludge particles When the encapsulated nano-alumina comes into contact with water, it continuously precipitates free calcium, aluminum and silicon atoms to generate Ca(OH)2, ettringite and CSH / CASH gel hydration products; among them, sludge particles are used to increase the Al atom content in the hydration products and promote the formation of CASH gel; nano-alumina is used to fill the gaps between cements, promote the formation of CASH gel, increase the main chain length and improve the degree of polymerization.

[0055] The hydration process equation is: , , , .

[0056] The technical solution provided by the embodiment of the present invention has the following main features in terms of performance: (1) Greatly improve the corrosion resistance and service life of the concrete pipes of the municipal sewage network; Explanatoryally, the coating material of the embodiment of the present invention has better density, mainly because a small amount of nano-alumina is added during the preparation process, which extends the service life of the pipe.

[0057] (2) The resource utilization of water supply sludge is achieved. Explanatoryally, the coating material of the embodiment of the present invention uses the residual water supply sludge produced by the treatment process of the municipal water supply plant as a supplementary cementitious material. Currently, the treatment of this sludge is mainly landfill, which will cause certain harm to the environment. The present invention can reduce the pressure on the water supply plant to treat the sludge and achieve the resource utilization of the sludge. Compared with the pretreatment method of obtaining more active aluminum-containing sludge ash by high-temperature calcination, the method of low-temperature calcination combined with an alkaline activator is more environmentally friendly and closely follows the current background of high-quality ecological civilization construction.

[0058] (3) Non-toxic. Explanatoryally, the main components of water supply sludge are aluminum oxide and silicon dioxide, without the introduction of heavy metal ions. Even if it corrodes after application, no toxic or harmful substances are precipitated, which will not affect the subsequent sewage treatment process and is basically non-polluting to the environment.

[0059] (4) Not subject to geographical restrictions. Explanation: The current urbanization process has led to large-scale water supply plants in all prefecture-level cities, and most of them use PAC as a coagulant. Therefore, sludge raw materials are easily available and the output is large. It can be sourced locally, and the market prospects are broad.

[0060] In summary, the technical solution of the embodiment of the present invention, compared with traditional concrete materials, is green and environmentally friendly, low-cost, and has significantly improved stability and corrosion resistance by using water supply aluminum sludge ash as a supplementary cementitious material. In addition, the raw material composition is simple, the process is simple, and it is easy to construct. The technical solution of the present invention is not restricted by geographical location, has broad market prospects, and is suitable for large-scale production. Furthermore, in addition to applying the coating material to municipal sewage pipes, it can also be applied to concrete structures in sewage treatment plants and some acid-corrosion-resistant places, thereby extending the service life of materials or equipment.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a modified mortar coating material for sewage concrete pipe corrosion protection, characterized in that: The following steps are involved: Weigh the raw materials according to the preset ratio; wherein, the mass ratio of the aluminum sludge ash, silicate cement, and nano-alumina is (14.25-14.85): (80.75-84.15): (1-5); in addition, weigh water according to a ratio of 35% of the total mass of the aluminum sludge ash, silicate cement, and nano-alumina, weigh a water reducer according to a ratio of 1% of the total mass of the aluminum sludge ash, silicate cement, and nano-alumina, and weigh tributyl phosphate according to a ratio of 0.01% of the total mass of the aluminum sludge ash, silicate cement, and nano-alumina; The weighed aluminum sludge ash from the water supply and the Portland cement dry material were mixed evenly to obtain dry material A; the weighed water, water reducer and nano-alumina were mixed and subjected to water bath sonication to obtain mixed solution B; Pour the mixed liquid B into the dry material A while stirring and adding tributyl phosphate to hydrate to obtain a modified mortar coating material.

2. The method for preparing a modified mortar coating material for sewage concrete pipe corrosion protection according to claim 1, characterized in that: The hydration process includes: nano-alumina acts as a crystal nucleus, and silicate cement particles and water supply aluminum sludge ash sludge particles wrap the nano-alumina, which continuously precipitates free calcium, aluminum and silicon atoms when it comes into contact with water, generating Ca(OH)2, ettringite and CSH / CASH gel hydration products; among them, the water supply aluminum sludge ash sludge particles are used to increase the content of Al atoms in the hydration products and promote the formation of CASH gel; nano-alumina is used to fill the gaps between cements, promote the formation of CASH gel, increase the main chain length and improve the degree of polymerization.

3. The method for preparing a modified mortar coating material for sewage concrete pipe corrosion protection according to claim 2, characterized in that: The hydration process equation is: ， ， ， 。 4. The method for preparing a modified mortar coating material for sewage concrete pipe corrosion protection according to claim 1, characterized in that: The modified mortar coating material includes CASH gel with a main chain length of 6.01 and an Al[IV] / Si ratio of 0.0639.

5. The method for preparing a modified mortar coating material for sewage concrete pipe corrosion protection according to claim 1, characterized in that: The water supply aluminum sludge ash is obtained by mechanically dehydrating, drying and pre-treating chemical flocculation sludge from a municipal water company's sedimentation tank.

6. The method for preparing a modified mortar coating material for sewage concrete pipe corrosion protection according to claim 5, characterized in that: The mechanical dehydration and pretreatment steps include: drying first, then crushing and screening with a crusher, and finally calcining at 800°C.

7. The method for preparing a modified mortar coating material for sewage concrete pipe corrosion protection according to claim 6, characterized in that: The steps of the 800° C. calcination treatment specifically include: starting from room temperature, heating to 800° C. at a heating rate of 5° C. / min and maintaining for 120 minutes, and then cooling naturally.

8. The method for preparing a modified mortar coating material for sewage concrete pipe corrosion protection according to claim 6, characterized in that: In the steps of drying first, crushing with a crusher and screening, the drying is carried out at a temperature of 105° C., and the screening is carried out through a 200-mesh sieve.

9. The method for preparing a modified mortar coating material for sewage concrete pipe corrosion protection according to claim 1, characterized in that: The water is tap water; the nano-alumina, the water reducer, the tributyl phosphate, and the silicate cement are all commercially available; The average particle size of the nano-alumina is ≤50nm, and the specific surface area is >160m 2 / g, bulk density is 190g / cm 3 , purity ≥99.99%, crystal form is γ phase; the silicate cement grade is 425.

10. A modified mortar coating material for anti-corrosion of sewage concrete pipes, characterized in that: The preparation method according to any one of claims 1 to 9 is used.

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