Composite solidifying agent, preparation method and application in waste mud subgrade filler

Abstract

The application relates to the technical field of mud solidifying agents, and discloses a composite solidifying agent, a preparation method and application in waste mud roadbed fillers, wherein the composite solidifying agent comprises 16-25 parts of quicklime, 75-84 parts of phosphoric acid modified carbide slag, 12-22 parts of a polyacrylic acid copolymer solution and 0.12-0.17 parts of urea; in the solidifying process, the hydroxyl groups of the polyacrylic acid copolymer and the phosphate groups bonded on the surface of the carbide slag undergo a dehydration condensation reaction, so that the polyacrylic acid and the carbide slag form a continuous and stable chemical crosslinking network in the solidified material filler, play the role of an organic cementing solidifying agent, form an organic-inorganic composite solidifying effect, and enhance the mechanical strength of the filler. After a large number of phosphate groups are introduced on the surface of the carbide slag, the dispersibility of the carbide slag is improved, the carbide slag is not prone to agglomeration, and the mechanical properties of the roadbed filler are improved.

Description

Technical Field

[0001] This invention relates to the field of mud curing agent technology, specifically to a composite curing agent, its preparation method, and its application in waste mud roadbed filler. Background Technology

[0002] In recent years, with the continuous development of my country's construction engineering technology, the construction technology of bored cast-in-place concrete piles has become increasingly sophisticated. Due to its strong applicability, simple process, easy quality control, and reasonable cost, it has been widely used. The positive circulation construction process for bored cast-in-place piles requires the use of mud of a certain relative density for borehole wall maintenance. However, after multiple circulations, a large amount of waste mud is inevitably generated. Because of the high fluidity of the waste mud and the limited usable area on the construction site, the storage and treatment of waste mud has a certain impact. In highway bridge construction, due to the terrain and topography, the problem of mud treatment is difficult to solve. Generally, sedimentation tanks are built to store waste mud. However, because waste mud is a colloidal system and relatively stable, natural sedimentation makes solid-liquid separation difficult, resulting in a significant risk of spillage during storage, which can cause water and soil pollution.

[0003] Therefore, considering the technical and economic feasibility of resource utilization of engineering waste mud and solid waste materials, as well as the environmental and safety issues it brings, this approach not only reduces the disposal costs of waste mud and slag and the purchase costs of raw materials such as bentonite, but also absorbs a large amount of construction waste and industrial waste residue. This avoids environmental pollution from transporting waste mud and slag, improving environmental benefits while reducing engineering costs, and realizing the resource utilization of waste mud and solid waste materials, which has significant economic value and environmental significance. Current mud solidification systems mainly include inorganic cementitious solidification systems such as lime, cement, and fly ash, as well as organic polymer cementing systems. This invention aims to utilize lime-carbide slag as an inorganic cementitious solidifying agent, combined with polyacrylic acid-based organic cementitious solidifying agents, to improve the mechanical strength of waste mud solidification fillers. Summary of the Invention

[0004] This invention solves the problem of low mechanical strength of waste mud roadbed filler.

[0005] The technical solution of this invention is: A composite curing agent, its preparation method, and its application in waste mud roadbed filler, wherein the composite curing agent comprises, by weight, 16-25 parts quicklime, 75-84 parts phosphoric acid modified carbide slag, 12-22 parts polyacrylic acid copolymer solution, and 0.12-0.17 parts urea; The preparation method of polyacrylic acid copolymer solution is as follows: add acrylic acid, hydroxyethyl acrylate, and initiator to water, stir to carry out polymerization reaction, add sodium hydroxide to adjust pH, stir, and obtain polyacrylic acid copolymer solution.

[0006] Preferably, the polymerization reaction is carried out at 60-75°C for 3-5 hours.

[0007] Preferably, by weight, acrylic acid is 88-95 parts, hydroxyethyl acrylate is 5-12 parts, and initiator is 1.8-2.4 parts.

[0008] Preferably, the initiator is ammonium persulfate or potassium persulfate.

[0009] Preferably, the pH of the polyacrylic acid copolymer solution is 6-7.

[0010] The preferred method for preparing phosphoric acid modified calcium carbide slag is as follows: Calcium carbide slag is ground and pulverized, added to tetrahydrofuran, stirred and dispersed, phosphorus trichloride and triethylamine are added dropwise in an ice bath, the mixture is stirred and reacted, water is added for dilution, hydrolysis is carried out, sodium hydroxide is added to control the pH, the mixture is filtered, washed with water, and dried to obtain phosphoric acid modified calcium carbide slag; by weight, calcium carbide slag is 100 parts, phosphorus trichloride is 10-40 parts, and triethylamine is 15-70 parts; the stirring reaction is carried out at 70-80℃ for 12-18 hours; the hydrolysis is carried out at 60-70℃ for 2-3 hours; and the pH is controlled at 7-8.

[0011] Preferably, the composite curing agent is applied to waste mud roadbed filler: quicklime, phosphate-modified carbide slag, polyacrylic acid copolymer solution, and urea are added to construction waste mud, stirred and mixed, vibrated to degas, cured and maintained to obtain waste mud roadbed filler.

[0012] Preferably, the curing temperature is 100-120℃ and the time is 20-30 minutes.

[0013] Preferably, the curing temperature is 20-25℃ and the time is 3-90 days.

[0014] The advantages and beneficial effects of this invention are as follows: A phosphoric acid-modified calcium carbide slag is obtained by reacting an active P-Cl bond of phosphoric acid with the hydroxyl groups on the surface of calcium hydroxide and silicate components in the slag. The remaining P-Cl bonds then hydrolyze to form P-OH bonds. This process combines the slag with lime (used as waste slurry) in an inorganic activation-solidification system to form hydrated calcium silicate (CSH) and hydrated calcium aluminate (CAH) gels. The addition of a polyacrylic acid copolymer, containing hydroxyl groups, allows it to undergo dehydration condensation with the phosphate groups bonded to the slag surface during solidification. This creates a continuous and stable chemical cross-linked network between the polyacrylic acid and the slag within the solidified filler, acting as an organic binder and solidifier. This organic-inorganic composite solidification enhances the mechanical strength of the filler. The introduction of numerous phosphate groups onto the slag surface improves its dispersibility and reduces agglomeration, further enhancing the mechanical properties of the roadbed filler. Detailed Implementation

[0015] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0016] The following construction waste mud comes from waste mud generated during the construction of bored piles, with a solid content of approximately 57%. Calcium carbide slag comes from waste residue generated by high-temperature electric furnaces in calcium carbide production plants.

[0017] Example 1 (1) Add 9.2g acrylic acid, 0.8g hydroxyethyl acrylate and 0.2g ammonium persulfate to 20mL of water, heat to 65℃, stir for 5h, add sodium hydroxide to adjust the pH to 6, stir, and obtain polyacrylic acid copolymer solution.

[0018] (2) Grind 50g of carbide slag into powder, add it to 2L of tetrahydrofuran, stir and disperse for 30min, add 10g of phosphorus trichloride and 16g of triethylamine dropwise in an ice bath, heat to 80℃, stir and react for 12h, add 3L of water to dilute, stir and react for 3h at 60℃, add sodium hydroxide to adjust pH to 8, filter, wash with water, dry, and obtain phosphoric acid modified carbide slag.

[0019] (3) Add 19g quicklime, 81g phosphoric acid modified carbide slag, 15g polyacrylic acid copolymer solution and 0.14g urea to 1kg construction waste mud, stir and mix, vibrate to degas, heat cure at 110℃ for 30min, and cure at 20℃ for 3 days to obtain waste mud roadbed filler.

[0020] Example 2 (1) Add 8.8g acrylic acid, 1.2g hydroxyethyl acrylate and 0.24g potassium persulfate to 20mL of water, heat to 70℃, stir and react for 4h, add sodium hydroxide to adjust the pH to 6, stir, and obtain polyacrylic acid copolymer solution.

[0021] (2) Grind 50g of carbide slag into powder, add it to 3L of tetrahydrofuran, stir and disperse for 20min, add 20g of phosphorus trichloride and 35g of triethylamine dropwise in an ice bath, heat to 70℃, stir and react for 18h, add 3L of water to dilute, stir and react for 3h at 65℃, add sodium hydroxide to adjust pH to 7, filter, wash with water, dry, and obtain phosphoric acid modified carbide slag.

[0022] (3) Add 25g quicklime, 75g phosphoric acid modified carbide slag, 12g polyacrylic acid copolymer solution and 0.12g urea to 1kg construction waste mud, stir and mix, vibrate to degas, heat solidify at 100℃ for 30min, and cure at 20℃ for 7 days to obtain waste mud roadbed filler.

[0023] Example 3 (1) Add 9.5g acrylic acid, 0.5g hydroxyethyl acrylate and 0.18g ammonium persulfate to 25mL of water, heat to 60℃, stir for 5h, add sodium hydroxide to adjust the pH to 6, stir, and obtain polyacrylic acid copolymer solution.

[0024] (2) Grind 50g of carbide slag into powder, add it to 2L of tetrahydrofuran, stir and disperse for 30min, add 5g of phosphorus trichloride and 7.5g of triethylamine dropwise in an ice bath, heat to 75℃, stir and react for 18h, add 3.5L of water to dilute, stir and react for 3h at 60℃, add sodium hydroxide to adjust the pH to 8, filter, wash with water, dry, and obtain phosphoric acid modified carbide slag.

[0025] (3) Add 16g quicklime, 84g phosphoric acid modified carbide slag, 22g polyacrylic acid copolymer solution and 0.17g urea to 1kg construction waste mud, stir and mix, vibrate to degas, heat cure at 110℃ for 30min, and cure at 20℃ for 28 days to obtain waste mud roadbed filler.

[0026] Example 4 (1) Add 9g acrylic acid, 1g hydroxyethyl acrylate and 0.2g ammonium persulfate to 20mL of water, heat to 75℃, stir and react for 3h, add sodium hydroxide to adjust the pH to 7, stir, and obtain polyacrylic acid copolymer solution.

[0027] (2) Grind 50g of carbide slag into powder, add it to 3L of tetrahydrofuran, stir and disperse for 20min, add 15g of phosphorus trichloride and 25g of triethylamine dropwise in an ice bath, heat to 80℃, stir and react for 12h, add 3L of water to dilute, stir and react at 70℃ for 2h, add sodium hydroxide to adjust pH to 7, filter, wash with water, dry, and obtain phosphoric acid modified carbide slag.

[0028] (3) Add 22g quicklime, 78g phosphoric acid modified carbide slag, 20g polyacrylic acid copolymer solution and 0.15g urea to 1kg construction waste mud, stir and mix, vibrate to degas, heat cure at 120℃ for 20min, and cure at 20℃ for 60 days to obtain waste mud roadbed filler.

[0029] Example 5 (1) Add 8.8g acrylic acid, 1.2g hydroxyethyl acrylate and 0.2g ammonium persulfate to 20mL of water, heat to 75℃, stir for 3h, add sodium hydroxide to adjust the pH to 7, stir, and obtain polyacrylic acid copolymer solution.

[0030] (2) Grind 50g of carbide slag into powder, add it to 3L of tetrahydrofuran, stir and disperse for 20min, add 22g of phosphorus trichloride and 35g of triethylamine dropwise in an ice bath, heat to 80℃, stir and react for 12h, add 3L of water to dilute, stir and react for 3h at 60℃, add sodium hydroxide to adjust the pH to 7, filter, wash with water, dry, and obtain phosphoric acid modified carbide slag.

[0031] (3) Add 18g quicklime, 82g phosphoric acid modified carbide slag, 21g polyacrylic acid copolymer solution and 0.15g urea to 1kg construction waste mud, stir and mix, vibrate to degas, heat cure at 120℃ for 20min, and cure at 20℃ for 90 days to obtain waste mud roadbed filler.

[0032] Comparative Example 1 The difference from Example 1 is that a polyacrylic acid solution is used instead of a polyacrylic acid copolymer solution.

[0033] (1) Add 9.2g of acrylic acid and 0.2g of ammonium persulfate to 20mL of water, heat to 65℃, stir for 5h, add sodium hydroxide to adjust the pH to 6, stir, and obtain polyacrylic acid solution.

[0034] (2) Add 19g quicklime, 81g phosphoric acid modified carbide slag, 15g polyacrylic acid solution and 0.14g urea to 1kg construction waste mud, stir and mix, vibrate to degas, heat solidify at 110℃ for 30min, and cure at 20℃ for 3 days to obtain waste mud roadbed filler.

[0035] Comparative Example 2 The difference from Example 1 is that carbide slag is used instead of phosphoric acid modified carbide slag.

[0036] (1) Add 19g quicklime, 81g carbide slag, 15g polyacrylic acid copolymer solution and 0.14g urea to 1kg construction waste mud, stir and mix, vibrate to degas, heat cure at 110℃ for 30min, and cure at 20℃ for 3 days to obtain waste mud roadbed filler.

[0037] Comparative Example 3 The main difference from Example 1 is that phosphoric acid is used instead of phosphorus trichloride.

[0038] (1) Grind 50g of carbide slag into powder, add it to 2L of water, stir and disperse for 30min, add 11.8mL of aqueous solution containing 10g of phosphoric acid in an ice bath, heat to 80℃, stir for 12h, add 3L of water to dilute, stir at 60℃ for 3h, add sodium hydroxide to adjust pH to 8, filter, wash with water, and dry to obtain phosphoric acid modified carbide slag.

[0039] (2) Add 19g quicklime, 81g phosphoric acid modified carbide slag, 15g polyacrylic acid copolymer solution and 0.14g urea to 1kg construction waste mud, stir and mix, vibrate to degas, heat cure at 110℃ for 30min, and cure at 20℃ for 3 days to obtain waste mud roadbed filler.

[0040] The unconfined compressive strength and flexural strength of the waste mud roadbed filler were tested according to the method of JTG E51-2009, as shown in Table 1.

[0041] Table 1 Performance Tests

[0042] After testing, the waste mud roadbed fillers in Examples 1-5 showed higher compressive strength and flexural strength. This was mainly because the introduction of a large number of phosphate groups on the surface of the carbide slag improved its dispersibility and made it less prone to agglomeration. This improved the mechanical properties of the solidified filler. At the same time, the added polyacrylic acid copolymer contained hydroxyl groups. During the curing process, it underwent a dehydration condensation reaction with the phosphate groups bonded to the surface of the carbide slag, causing the polyacrylic acid and carbide slag to form a continuous and stable chemical cross-linking network in the solidified filler. This allowed the polyacrylic acid to act as an organic binder and curing agent, forming an organic-inorganic composite curing effect, which further enhanced the mechanical strength of the filler.

[0043] The polyacrylic acid in Comparative Example 1 does not contain hydroxyl groups and cannot react with phosphate groups on the surface of carbide slag. Therefore, it cannot act as an organic curing agent and does not form a continuous and stable chemical cross-linking network. As a result, the compressive strength and flexural strength of the filler are relatively low.

[0044] Comparative Example 2: The unmodified carbide slag had poor dispersibility and could not react with the hydroxyl groups of polyacrylic acid, thus failing to form a continuous and stable chemical cross-linking network. As a result, the filler had low compressive strength and flexural strength.

[0045] Comparative Example 3 uses phosphoric acid to modify carbide slag. The modification effect is lower than that of phosphoric acid in terms of active P-Cl bonds. It is difficult to bond a large number of phosphate groups on the surface, resulting in lower compressive strength and flexural strength of the filler.

[0046] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a composite curing agent, characterized in that, By weight, the composite curing agent comprises 16-25 parts quicklime, 75-84 parts phosphoric acid modified carbide slag, 12-22 parts polyacrylic acid copolymer solution, and 0.12-0.17 parts urea; The method for preparing the polyacrylic acid copolymer solution is as follows: add acrylic acid, hydroxyethyl acrylate, and an initiator to water, stir to react, add sodium hydroxide to adjust the pH, and stir to obtain the polyacrylic acid copolymer solution.

2. The method for preparing the composite curing agent according to claim 1, characterized in that, The reaction was carried out at 60-75°C for 3-5 hours.

3. The method for preparing the composite curing agent according to claim 1, characterized in that, By weight, the acrylic acid is 88-95 parts, the hydroxyethyl acrylate is 5-12 parts, and the initiator is 1.8-2.4 parts.

4. The method for preparing the composite curing agent according to claim 3, characterized in that, The initiator is ammonium persulfate or potassium persulfate.

5. The method for preparing the composite curing agent according to claim 1, characterized in that, The pH of the polyacrylic acid copolymer solution is 6-7.

6. The method for preparing the composite curing agent according to claim 1, characterized in that, The preparation method of the phosphoric acid modified carbide slag is as follows: 100 parts by weight of carbide slag are ground and crushed, added to tetrahydrofuran, stirred and dispersed, 10-40 parts of phosphorus trichloride and 15-70 parts of triethylamine are added dropwise in an ice bath, heated to 70-80℃, stirred and reacted for 12-18h, diluted with water, stirred and reacted at 60-70℃ for 2-3h, sodium hydroxide is added to adjust the pH to 7-8, filtered, washed with water, and dried to obtain phosphoric acid modified carbide slag.

7. A composite curing agent obtained by the preparation method according to any one of claims 1-6.

8. The application of the composite curing agent as described in claim 7 in waste mud roadbed filler, characterized in that, The preparation method of the waste mud roadbed filler is as follows: quicklime, phosphate-modified carbide slag, polyacrylic acid copolymer solution, and urea are added to the construction waste mud, stirred and mixed, vibrated to degas, solidified, and cured to obtain the waste mud roadbed filler.

9. The application of the composite curing agent according to claim 8 in waste mud roadbed filler, characterized in that, The curing temperature is 100-120℃ and the time is 20-30 minutes.

10. The application of the composite curing agent according to claim 8 in waste mud roadbed filler, characterized in that, The curing temperature is 20-25℃, and the time is 3-90 days.

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