A low-shrinkage cement-based grouting material based on clean water sludge and a preparation method thereof

Abstract

The application belongs to the technical field of water purification sludge treatment, and discloses a low-shrinkage cement-based grouting material based on water purification sludge and a preparation method thereof. The grouting material raw materials include, in terms of mass fraction, 67 parts of water purification sludge, 13-16 parts of Portland cement, 16 parts of quartz sand, 0.02-0.04 parts of a deflocculating agent, 0.1-0.3 parts of a coagulant, and 0.2-0.5 parts of a water reducing agent. Each part of the deflocculating agent contains 0.01 part of sodium tripolyphosphate and 0.03 part of sodium citrate. In the preparation, the water purification sludge is uniformly mixed with the deflocculating agent; then the Portland cement and the quartz sand are added and uniformly mixed to obtain a mixed slurry; and then the water reducing agent and the coagulant are added to the mixed slurry and uniformly mixed to obtain the low-shrinkage cement-based grouting material based on water purification sludge. The application can open the cellular structure in the PCA water purification sludge to release free water, and the free water is mixed with cement to obtain a backfill grouting material with high flowability and good setting performance. The preparation method is simple, the material source is wide, the cost is low, there is no toxic effect, and the application has wide practicability.

Description

Technical Field

[0001] This invention belongs to the field of water purification sludge treatment technology, specifically relating to a low-shrinkage cement-based grouting material based on water purification sludge and its preparation method. Background Technology

[0002] Urban water treatment plants, while employing key technologies such as coagulation, sedimentation, filtration, and disinfection to produce purified water that meets drinking water quality standards, face the challenge of handling the sludge generated during the purification process. Water purification sludge, a harmless, high-moisture, brownish-yellow, fluid soil formed through coagulation and sedimentation, has a crystal structure similar to clay and is mainly composed of minerals such as SiO2 and Al2O3.

[0003] If wastewater treatment sludge is not properly treated, direct landfilling will not only cause serious environmental pollution but also waste a large amount of precious water and land resources. Furthermore, due to its generally poor compressibility and high water content, the disposal cost of wastewater treatment sludge will increase further.

[0004] Currently, the main methods for disposing of wastewater treatment sludge include landfill, land application, and utilization in building materials. However, these methods all require complex processes and additional energy consumption. Direct application of wastewater treatment sludge, however, can not only reduce treatment costs but also achieve efficient resource utilization. Therefore, exploring methods for the resource utilization of wastewater treatment sludge is of great significance.

[0005] Chinese invention patent application CN115477382A discloses a method for the resource utilization of iron-rich sludge from water treatment plants. This invention discloses a method for the resource utilization of iron-rich sludge from water treatment plants, which involves processing the sludge into granular or brick-like shapes. The sludge granules are prepared using sludge drying technology, resulting in granular ceramsite, which is used as filler in constructed wetlands. This method avoids secondary pollution caused by conventional sludge disposal methods in water treatment plants, enhances nitrogen and phosphorus removal in constructed wetlands, and simultaneously achieves low-cost phosphorus resource recovery, thereby realizing the mineralization of iron-rich sludge from water treatment plants.

[0006] Chinese invention patent application CN101423321 discloses a method for the resource-based treatment of sludge from water purification tanks. This invention relates to a method for the resource-based treatment of sludge from water plant purification tanks. The method mainly involves settling the sludge into a slurry, filtering out sand and impurities, stirring it in a reflux mixing tank, and then pumping it through a high-pressure pump to a high-temperature sterilization and granulation tower. After hot air sterilization and drying to produce granular sludge particles, the particles are then calcined to stabilize free aluminum ions and other substances within the granular sludge particles into stable and pollution-free artificial sand for resource reuse.

[0007] Chinese invention patent application CN106518150B discloses a composite ceramsite prepared from water purification sludge and diatomaceous earth. This invention relates to a method for preparing composite ceramsite using water purification sludge and diatomaceous earth, belonging to the field of inorganic non-metallic materials. The preparation steps of the composite ceramsite include mixing, pelletizing, drying, preheating, and calcination. This invention utilizes water purification sludge generated during the production process of water supply plants and waste diatomaceous earth generated from filtration aids in breweries as raw materials, effectively solving the treatment and disposal problems of these two solid wastes.

[0008] Chinese invention patent application CN114057416A discloses a method for preparing silicate cement clinker using sludge incineration ash. This invention relates to the field of cement technology, specifically to a method for preparing silicate cement clinker using sludge incineration ash. This invention utilizes sludge incineration ash from urban wastewater treatment as an iron-containing corrective agent in the preparation of cement clinker. Furthermore, it provides technical support for using cement kilns to co-process urban wastewater sludge incineration ash, promoting the reduction of urban sludge volume and the resource utilization of sludge incineration ash.

[0009] Chinese invention patent application CN106946434A discloses a method for the resource utilization of manganese, aluminum, and iron-containing sludge from a water treatment plant. The method includes the following steps: using the sludge as raw material, first dewatering it to obtain dry sludge, then sequentially adding fly ash from a power plant and sulfuric acid for acidification treatment to obtain an acidified material; then adding kaolin, adjusting the silicon:aluminum mass ratio in the silicified material to 1:1 using sodium silicate, allowing it to stand for 7 days, and then air-drying or baking to obtain a dry material; finally, heating the dry material to 400-500℃ and calcining it for 1 hour, followed by natural cooling to obtain a material with adsorption capacity.

[0010] The main drawbacks of these patent applications are concentrated in the following aspects:

[0011] Table 1

[0012]

[0013] In summary, the shortcomings of the existing patent applications mainly lie in the limitations of raw materials and applications, energy consumption and cost issues, technical feasibility and stability, and environmental friendliness. In practical applications, these factors need to be comprehensively considered to seek more economical, efficient, and environmentally friendly solutions for sludge treatment and resource utilization. Summary of the Invention

[0014] To address the problems existing in the prior art, the present invention aims to provide a low-shrinkage cement-based grouting material based on PCA (Polycarbonate Acid) sludge and its preparation method. The present invention can open the cellular structure in PCA sludge to release free water, which is then mixed with cement to obtain a backfill grouting material with high fluidity and good setting properties. The present invention does not have the energy consumption problems of the prior art. In addition, the preparation method of the present invention is simple, the required materials are widely available, the cost is low, and it has no toxic effects, thus having wide applicability.

[0015] The technical solution adopted in this invention is as follows:

[0016] A low-shrinkage cement-based grouting material based on wastewater treatment sludge, comprising, by weight, the following raw materials:

[0017] 67 parts of clean water sludge, 13-16 parts of silicate cement, 16 parts of quartz sand, 0.02-0.04 parts of flocculant, 0.1-0.4 parts of coagulant, and 0.2-0.5 parts of water-reducing agent;

[0018] The flocculant comprises sodium tripolyphosphate and sodium citrate, with each part of the flocculant containing 0.01 to 0.03 parts of sodium tripolyphosphate and 0.01 to 0.03 parts of sodium citrate.

[0019] Preferably, by mass percentage, the water purification sludge contains minerals such as SiO2 and Al2O3, which are similar in composition to clay. Specifically, the solid component of the water purification sludge contains 87% to 94% SiO2, 6% to 12% Al2O3, and the remainder is other impurities. The main elements of the water purification sludge are Si, Al, Fe, O, and C, and the water content of the water purification sludge can reach up to 260%.

[0020] Preferably, the silicate cement is P·O 42.5R cement.

[0021] Preferably, the quartz sand is ISO standard sand.

[0022] Preferably, the water-reducing agent is a naphthalene-based water-reducing agent.

[0023] Preferably, the sodium tripolyphosphate is of industrial grade with a purity of 99% or higher.

[0024] The sodium citrate used is of industrial grade with a purity of 99% or higher.

[0025] Preferably, the coagulant is anhydrous sodium sulfate.

[0026] Preferably, the coagulant is industrial-grade anhydrous sodium sulfate with a purity of 99% or higher.

[0027] The preparation method of the low-shrinkage cement-based grouting material based on water purification sludge according to the present invention includes the following steps:

[0028] The sludge from the water treatment plant is mixed with a flocculant; then silicate cement and quartz sand are added and mixed to obtain a mixed slurry; water-reducing agent and coagulant are added to the mixed slurry and mixed to obtain the low-shrinkage cement-based grouting material based on the sludge from the water treatment plant.

[0029] The present invention has the following beneficial effects:

[0030] This invention relates to a low-shrinkage cement-based grouting material based on treated sludge, in which a flocculant is added. This flocculant includes sodium tripolyphosphate and sodium citrate. The addition of sodium tripolyphosphate causes it to hydrolyze into phosphate ions and sodium ions. The sodium ions generated by hydrolysis replace aluminum ions in the treated sludge. The aluminum ions chelate with phosphate ions to form soluble complexes, disrupting the cellular structure of the sludge flocs and compensating for steric hindrance. This results in higher fluidity and more uniform dispersion of the treated sludge in less water. The phosphate ions generated after the hydrolysis of sodium tripolyphosphate replace the aluminum ions from the hydrolyzed and flocculated PAC (polyaluminum chloride) in the treated sludge, forming new soluble substances. This disrupts the original colloidal structure of aluminum hydroxide generated by aluminum ion hydrolysis, releasing the trapped free water. Cement is then added, which acts as a coagulant to solidify the sludge. However, due to the high sludge moisture content, residual flocculants, and the retarding effect of sodium tripolyphosphate on cement, the cement setting and hardening time is severely weakened. It can only form a shape after 7 days but still cannot set. Therefore, an accelerator is added in this invention. The accelerator can quickly react with the cement hydration to form Ca(OH)2, generating gypsum and alkali. The newly generated fine-grained dihydrate gypsum reacts with cement much faster than the gypsum added during cement grinding, and the hydration reaction produces hydrated calcium sulfoaluminate crystals. Simultaneously, the above reaction also accelerates the hydration of C3S. Accelerating the hydration process improves the early strength without affecting its flowability. The initial flowability of the mixed slurry should be greater than 290 mm, and the loss after 30 minutes should not be less than 260 mm, meeting the basic process requirements of grouting materials. The 28-day strength should be above 1.5 MPa.

[0031] In the preparation method of this invention, the prepared deflocculating agent is first added to the flocculated sludge and stirred to destroy the cellular structure and release free water. Then, cement and additives are added and stirred to mix thoroughly.

[0032] In summary, this invention can open the cellular structure in PCA water purification sludge to release free water, which, after mixing with cement, yields a backfill grouting material with high fluidity and good setting properties. This invention does not have the energy consumption problems of the prior art mentioned in the background section. In addition, the preparation method of this invention is simple, the required materials are widely available, the cost is low, and it has no toxic effects, thus having wide applicability. Attached Figure Description

[0033] Figure 1This is a flowchart of the preparation method of the low-shrinkage cement-based grouting material based on water purification sludge according to the present invention. Detailed Implementation

[0034] The technical solution of the present invention is described below with reference to specific implementation examples. Each embodiment is an experimental example and provides real performance test data. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] This invention relates to a low-shrinkage cement-based grouting material based on purified sludge, comprising the following raw materials in the indicated weight proportions: 67 parts purified sludge, 13-16 parts silicate cement, 16 parts quartz sand, 0.02-0.04 parts flocculant, 0.1-0.4 parts coagulant, and 0.2-0.5 parts water-reducing agent. The flocculant comprises sodium tripolyphosphate and sodium citrate, with each part of flocculant containing 0.01-0.03 parts of sodium tripolyphosphate and 0.01-0.03 parts of sodium citrate.

[0036] Among them, the silicate cement used is P·O 42.5R cement, the quartz sand used is ISO standard sand, the water-reducing agent used is naphthalene-based water-reducing agent, the sodium tripolyphosphate is 99% or higher industrial grade, the sodium citrate is 99% or higher industrial grade, and the accelerator is 99% or higher industrial grade anhydrous sodium sulfate.

[0037] Reference Figure 1 The preparation method of the low-shrinkage cement-based grouting material based on water purification sludge of the present invention includes the following process:

[0038] Weigh out the following components according to the specified proportions: ordinary silicate cement, water purification flocculation sludge, flocculant, quartz sand, water-reducing agent, and setting accelerator.

[0039] Place the purified sludge into an NJ-160A mixer, then pour the flocculant into the NJ-160A mixer and mix. The mixer rotates at a low speed of 65 r / min for 240 seconds until uniform, to obtain high-fluidity flocculant sludge.

[0040] Then, ordinary silicate cement and quartz sand are added to the NJ-160A mixer. The mixer is rotated at a low speed of 65 r / min for 120 seconds until uniform, and a mixed slurry is obtained.

[0041] Next, pour the water-reducing agent and the setting accelerator into the NJ-160A mixer, and mix the cement paste mixer at a high speed of 130 r / min for 120 seconds until uniform, to obtain the low-shrinkage cement-based grouting material based on clean water sludge of the present invention.

[0042] The specific mechanism of the technical solution of the present invention will be explained below:

[0043] The technical problem this invention aims to solve is to open the cellular structure of PCA (polyaluminum chloride) sludge, release free water, and mix it with cement to obtain a backfill grouting material with high fluidity and good coagulation performance. A flocculant prepared from sodium tripolyphosphate and sodium citrate in a specific ratio is added to the sludge. The addition of sodium tripolyphosphate allows the phosphate ions from sodium tripolyphosphate hydrolysis to exchange with aluminum ions in the sludge through ion exchange. The aluminum ions then chelate with the phosphate ions to form soluble complexes, disrupting the flocculated cellular structure of the sludge and compensating for steric hindrance. This results in higher fluidity and more uniform dispersion of the sludge in less water. The phosphate ions generated after the hydrolysis of sodium tripolyphosphate replace the aluminum ions from the hydrolysis and flocculation of PAC (polyaluminum chloride) in the sludge, forming new soluble substances. This disrupts the original aluminum hydroxide gel structure generated by aluminum ion hydrolysis, releasing the trapped free water. Then, silicate cement is added, which acts as a coagulant and solidifies the sludge. However, due to the high sludge moisture content, residual flocculants, and the retarding effect of sodium tripolyphosphate on cement, the cement setting and hardening time is severely weakened. It can only form a shape after 7 days but still cannot set. Therefore, this invention also adds a setting accelerator – anhydrous sodium sulfate. Sodium sulfate reacts quickly with cement hydration to form Ca(OH)2, generating gypsum and alkali. The newly generated fine-grained dihydrate gypsum reacts with cement much faster than the gypsum added during cement grinding, forming hydrated calcium sulfoaluminate crystals. Simultaneously, the above reaction also accelerates the hydration of C3S. Accelerating the hydration process improves early strength without affecting its flowability. The initial flowability of the mixed slurry should be greater than 290 mm, and the loss after 30 minutes should not be less than 260 mm, meeting the basic process requirements for grouting materials. The 28-day strength should be above 1.5 MPa.

[0044] As can be seen from the above mechanism, compared with the prior art, the present invention solves the problems of additional energy input and complex process in the resource utilization of water purification sludge.

[0045] The following detailed description, in conjunction with specific embodiments, further illustrates that the water purification sludge used in the following embodiments of the present invention is water purification sludge produced by a water treatment plant. By mass percentage, the solid components of the water purification sludge contain: 93% SiO2, 6.5% Al2O3, and the remainder being other impurities; the water content of the water purification sludge is 260%.

[0046] Example 1:

[0047] This embodiment is based on a low-shrinkage cement-based grouting material made from purified sludge. By weight, its raw materials include: 67 parts purified sludge, 13 parts silicate cement, 16 parts quartz sand, 0.02 parts flocculant, 0.1 parts anhydrous sodium sulfate, and 0.2 parts naphthalene-based water-reducing agent. Each part of flocculant contains 0.01 parts sodium tripolyphosphate and 0.03 parts sodium citrate.

[0048] In this embodiment, the low-shrinkage cement-based grouting material based on water purification sludge is prepared according to the above preparation method.

[0049] Example 2:

[0050] This embodiment is based on a low-shrinkage cement-based grouting material made from purified sludge. By weight, its raw materials include: 67 parts purified sludge, 14 parts silicate cement, 16 parts quartz sand, 0.03 parts flocculant, 0.2 parts anhydrous sodium sulfate, and 0.3 parts naphthalene-based water-reducing agent. Each part of flocculant contains 0.02 parts sodium tripolyphosphate and 0.02 parts sodium citrate.

[0051] In this embodiment, the low-shrinkage cement-based grouting material based on water purification sludge is prepared according to the above preparation method.

[0052] Example 3:

[0053] This embodiment is based on a low-shrinkage cement-based grouting material made from purified sludge. By weight, its raw materials include: 67 parts purified sludge, 15 parts silicate cement, 16 parts quartz sand, 0.04 parts flocculant, 0.3 parts anhydrous sodium sulfate, and 0.4 parts naphthalene-based water-reducing agent. Each part of flocculant contains 0.03 parts sodium tripolyphosphate and 0.01 parts sodium citrate.

[0054] In this embodiment, the low-shrinkage cement-based grouting material based on water purification sludge is prepared according to the above preparation method.

[0055] Example 4:

[0056] This embodiment is based on a low-shrinkage cement-based grouting material made from treated sludge. By weight, its raw materials include: 67 parts treated sludge, 16 parts silicate cement, 16 parts quartz sand, 0.02 parts flocculant, 0.4 parts anhydrous sodium sulfate, and 0.5 parts naphthalene-based water-reducing agent. Each part of flocculant contains 0.015 parts sodium tripolyphosphate and 0.035 parts sodium citrate.

[0057] In this embodiment, the low-shrinkage cement-based grouting material based on water purification sludge is prepared according to the above preparation method.

[0058] The performance tests of the low-shrinkage cement-based grouting materials based on purified sludge prepared in Examples 1 to 4 above showed that the fluidity conformed to the current national standard GB / T2419 "Determination of Flowability of Cement Mortar", with an initial fluidity range of 330-290 mm and a 30-minute fluidity range of 260-290 mm. The 28-day density and shrinkage were tested according to GB / T 29417-2012 "Test Method for Drying Shrinkage Cracking Performance of Cement Mortar and Concrete". The compressive strength test was conducted according to the relevant provisions of the current national standard GB / T17671 "Test Method for Strength of Cement Mortar (ISO Method)", with a range of 0.5-2.5 MPa. Specific test results are shown in Table 2.

[0059] Table 2

[0060]

[0061]

[0062] As shown in Table 1, in each embodiment, the water-cement ratio of the paste decreases relatively with the increase of cement proportion, and the fluidity decreases accordingly. The initial fluidity ranges from 310 to 290 mm, and the fluidity loss over time ranges from 260 to 290 mm. The density also increases accordingly with the increase of solid content, ranging from 0.83 to 0.90 g / kg·m³. -3 The compressive strength increases with the increase of cement ratio and the increase of hydration products, with a strength range of 0.9 to 1.8 MPa, which meets the fluidity and strength standards of grouting materials.

[0063] The shrinkage rate tests of the materials prepared in Examples 1 to 4 above are shown in Table 3.

[0064] Table 3

[0065]

[0066] As shown in Table 2, with the increase of cement content, the solid content of the grout also increases accordingly, and the shrinkage rate decreases accordingly, ranging from 2.55% to 3.85%, which meets the shrinkage standard of cement grouting materials.

Claims

1. A low-shrinkage cement-based grouting material based on wastewater treatment sludge, characterized in that, The raw materials, by mass, include: 67 parts of clean water sludge, 13-16 parts of silicate cement, 16 parts of quartz sand, 0.02-0.04 parts of flocculant, 0.1-0.4 parts of coagulant, and 0.2-0.5 parts of water-reducing agent; The flocculant comprises sodium tripolyphosphate and sodium citrate, with each part of the flocculant containing 0.01 to 0.03 parts of sodium tripolyphosphate and 0.01 to 0.03 parts of sodium citrate; By mass percentage, the solid components of the water purification sludge contain: 87%~94% SiO2, 6%~12% Al2O3, with the remainder being other impurities. The water content of the water purification sludge reaches a maximum of 260%. The preparation method of the low-shrinkage cement-based grouting material based on water purification sludge includes the following steps: The sludge from the water treatment plant is mixed with a flocculant; then silicate cement and quartz sand are added and mixed to obtain a mixed slurry; water-reducing agent and coagulant are added to the mixed slurry and mixed to obtain the low-shrinkage cement-based grouting material based on the sludge from the water treatment plant.

2. The low-shrinkage cement-based grouting material based on purified sludge according to claim 1, characterized in that, The silicate cement used is P·O 42.5R cement.

3. The low-shrinkage cement-based grouting material based on water purification sludge according to claim 1, characterized in that, The quartz sand used is ISO standard sand.

4. The low-shrinkage cement-based grouting material based on water purification sludge according to claim 1, characterized in that, The water-reducing agent is a naphthalene-based water-reducing agent.

5. The low-shrinkage cement-based grouting material based on water purification sludge according to claim 1, characterized in that, The sodium tripolyphosphate used is of industrial grade with a purity of 99% or higher.

6. The low-shrinkage cement-based grouting material based on water purification sludge according to claim 1, characterized in that, The sodium citrate used is of industrial grade with a purity of 99% or higher.

7. A low-shrinkage cement-based grouting material based on wastewater treatment sludge according to claim 5 or 6, characterized in that, The coagulant used is anhydrous sodium sulfate.

8. The low-shrinkage cement-based grouting material based on water purification sludge according to claim 1, characterized in that, The coagulant used is industrial-grade anhydrous sodium sulfate with a purity of 99% or higher.

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