An in-situ phosphogypsum solidification modifier, and a preparation method and application thereof

Abstract

The application belongs to the technical field of phosphogypsum, and relates to a raw phosphogypsum solidification modifier, a preparation method and application thereof. The modifier comprises the following components and weight percentage contents: calcium chloride 30.0-35.0%; polyaluminum chloride 2.5-3.0%; dimethyl silicone oil 2.0-2.5%; polyacrylamide 0.5-1.0%; polyurethane resin 0.5-1.0%; water 57.5-65.5%; and lauryl alcohol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether and methanol. Compared with the prior art, the application effectively fixes free phosphorus elements in the phosphogypsum through the synergistic effect of polyaluminum chloride and dimethyl silicone oil, and effectively fixes free fluorine elements through the reaction of calcium chloride and free fluorine, so that the leaching amount of free phosphorus and free fluorine is significantly reduced, and the application has outstanding environmental friendly characteristics. Meanwhile, the mechanical properties of the phosphogypsum-based material are also significantly improved, so that the application can ensure the wide application of the phosphogypsum-based material in multiple fields, and has important research and application value in the research and development of high-performance and environmentally friendly building materials.

Description

Technical Field

[0001] This invention belongs to the field of industrial solid waste resource utilization and phosphogypsum technology, and relates to a solidification modifier for undisturbed phosphogypsum, its preparation method and application. Background Technology

[0002] Phosphogypsum, a byproduct of wet-process phosphoric acid production, has high resource value. However, it typically suffers from high solubility, strong hygroscopicity, and the presence of large amounts of soluble impurities (such as phosphates and fluorides). This significantly increases its chemical activity, making its mechanical properties and environmental stability far from meeting the demands of demanding engineering applications, thus severely limiting its use in building materials. In particular, the leaching of free phosphorus and fluoride from phosphogypsum seriously affects its environmental safety, causing potential pollution to soil, water sources, and plant growth.

[0003] In recent years, modification techniques for phosphogypsum have been extensively studied to improve its performance in building materials. Existing technologies primarily improve phosphogypsum performance by using modifiers such as mineral admixtures, polymers, and methyl silicone oil. However, these approaches typically focus on single-aspect improvements, lacking a comprehensive enhancement of phosphogypsum's properties. For example, Chinese patent CN104628349B proposes a phosphogypsum-based high-fluidity grouting material that improves fluidity and early strength by combining high-strength phosphogypsum with fly ash, carbide slag, and cement. Meanwhile, Chinese patent CN102173709B utilizes a combination of silicate cement and slag powder to enhance the water resistance and setting time control of phosphogypsum. Despite these technological breakthroughs, shortcomings remain in long-term use and control of free phosphorus and free fluoride leaching.

[0004] Current technologies have not effectively solved the problem of free phosphorus and free fluoride leaching from phosphogypsum, especially in terms of long-term use and the impact of humid environments. Therefore, there is an urgent need for an innovative technical solution that can significantly improve the stability, mechanical properties, and durability of phosphogypsum with a smaller addition amount, particularly by reducing the leaching of free phosphorus and free fluoride, thereby improving overall performance. Summary of the Invention

[0005] The purpose of this invention is to provide a virgin phosphogypsum curing modifier, its preparation method, and its application, to solve the problem of free phosphorus and free fluorine leaching from phosphogypsum. This invention effectively fixes free phosphorus in phosphogypsum through the synergistic effect of polyaluminum chloride and dimethyl silicone oil, and effectively fixes free fluorine through the reaction of calcium chloride with free fluorine, thereby significantly reducing the leaching of free phosphorus and free fluorine and exhibiting outstanding environmentally friendly characteristics. It also significantly improves the mechanical properties of phosphogypsum-based materials, ensuring their wide application in multiple fields, especially possessing significant research and application value in the development of high-performance and environmentally friendly building materials.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A first aspect of the present invention provides a curing modifier for undisturbed phosphogypsum, comprising the following components and weight percentages:

[0008] as well as,

[0009] Lauryl alcohol polyoxyethylene ether, isotridecyl alcohol polyoxyethylene ether and methanol;

[0010] The mass ratio of lauryl alcohol polyoxyethylene ether to isotretinoin polyoxyethylene ether is 1:(2-3), and the total mass of lauryl alcohol polyoxyethylene ether and isotretinoin polyoxyethylene ether is 8-12% of the mass of dimethyl silicone oil.

[0011] This invention combines anhydrous calcium chloride, polyaluminum chloride, dimethyl silicone oil, polyacrylamide, and polyurethane resin to form a composite modifier, utilizing their synergistic effect to effectively improve the performance of phosphogypsum-based materials. Through the synergistic effect of polyaluminum chloride (PAC), dimethyl silicone oil, and calcium chloride, this invention effectively reduces the leaching of free phosphorus and free fluoride from phosphogypsum-based materials, while simultaneously improving the material's mechanical properties, water resistance, and long-term stability. Specifically, the Al in PAC... 3+ Phosphate (PO4) is fixed by complexation. 3- This reduces the release of free phosphorus; dimethyl silicone oil forms a hydrophobic barrier inside the material, reducing the dissolution of phosphate complexes by water migration and further inhibiting phosphorus exudation; calcium chloride releases Ca... 2+ Can be used with F - The combination of calcium chloride and PAC forms a sparingly soluble CaF2 precipitate, effectively reducing the solubility of free fluorine. Simultaneously, calcium chloride promotes the formation of hydration products, working with PAC to optimize the pore structure of the material and improve overall density. Experiments show that when the three components work synergistically in the optimized ratio, the fixation effect of phosphorus and fluorine is significantly better than that of a single component. At the same time, the compressive strength, water resistance, and durability of the material are all improved, providing an efficient modification strategy for the high-performance application of phosphogypsum.

[0012] Furthermore, the addition of auxiliary materials such as polyacrylamide and polyurethane resin further improves the rheological properties, crack resistance, and durability of phosphogypsum, significantly enhancing its stability and workability in humid environments. This composite modification technology provides a novel solution for the widespread application of phosphogypsum in building materials, and has broad application prospects, especially in the development of environmentally friendly and high-performance building materials.

[0013] In some specific embodiments, the calcium chloride is a white powdery solid.

[0014] In some specific embodiments, the polyaluminum chloride contains aluminum oxide (Al2O3) with a mass content of not less than 30%, and is a white powdery solid.

[0015] In some specific embodiments, the dimethyl silicone oil has a viscosity of 4500-5500 cSt and is a colorless and transparent liquid; preferably, the viscosity is 5000 cSt.

[0016] In some specific embodiments, the polyacrylamide has a molecular weight of not less than 5 million and is a white powdery solid.

[0017] In some specific embodiments, the polyurethane resin is an aqueous polyurethane emulsion with a solid content of 50% to 60%.

[0018] In some specific embodiments, the lauryl alcohol polyoxyethylene ether (AEO-9) is a milky white paste with a cloud point of 70-95°C.

[0019] In some specific embodiments, the isomeric tridecyl alcohol polyoxyethylene ether (E1309) is a colorless liquid with a hydroxyl value of 94±5 mgKOH / g.

[0020] In some specific embodiments, the mass ratio of lauryl alcohol polyoxyethylene ether to isotretinoin polyoxyethylene ether is 1:2.5, and the total mass of lauryl alcohol polyoxyethylene ether and isotretinoin polyoxyethylene ether accounts for 10% of the total mass of dimethyl silicone oil.

[0021] In some specific embodiments, the methanol is a colorless, odorless, volatile liquid with a purity greater than 99%, and the amount used is 0.3 to 0.8% of the mass of dimethyl silicone oil, preferably 0.5% of the mass of dimethyl silicone oil.

[0022] A second aspect of the present invention provides a method for preparing the undisturbed phosphogypsum curing modifier as described above, comprising: heating and stirring calcium chloride, polyaluminum chloride, dimethyl silicone oil, polyacrylamide, polyurethane resin, water, lauryl alcohol polyoxyethylene ether, isotridecyl alcohol polyoxyethylene ether, and methanol at 80-85°C, and then allowing it to stand to obtain the product.

[0023] A third aspect of the present invention provides an application of the unprocessed phosphogypsum curing modifier as described above, comprising using the unprocessed phosphogypsum curing modifier to prepare phosphogypsum-based materials.

[0024] In some specific implementations, the application method includes: mixing phosphogypsum with cementing materials and undisturbed phosphogypsum curing modifier evenly, and letting it stand for a certain period of time to allow the modifier to react with the phosphogypsum.

[0025] In some specific implementations, the application method includes the following steps:

[0026] (1) Stir phosphogypsum and cement or other cementitious materials at low speed, weigh the curing modifier and add it to the mixture;

[0027] (2) Stir quickly until the curing modifier and phosphogypsum are fully in contact and evenly mixed;

[0028] (3) After stirring, let it stand for a certain period of time to ensure that the modifier and phosphogypsum react fully. Finally, adjust the operability and apply it to the construction site.

[0029] In some specific embodiments, the amount of the original phosphogypsum curing modifier added is 1 to 3% of the mass of phosphogypsum.

[0030] In the system of this invention, complex physicochemical interactions exist among the components, such as ionic reactions, interfacial modification, and regulation of gelling properties. Therefore, the following key parameters are limited:

[0031] Calcium chloride content (30.0–35.0%):

[0032] Calcium chloride can promote the coagulation of phosphogypsum particles, improve early strength, and help stabilize free phosphorus by regulating the ion balance of the system through chloride ions.

[0033] If the content is too low (<30%), Ca 2+ Insufficient supply, phosphate (PO4) 3- The reduced fixation capacity of phosphorus leads to increased free phosphorus leaching and slower early strength development.

[0034] If the content is too high (>35%), it may cause a large amount of CaCl2 to precipitate, forming easily soluble salts, increasing the material's hygroscopicity and dissolution risk, and affecting its durability.

[0035] Polyaluminum chloride (PAC, 2.5–3.0%):

[0036] PAC via Al 3+ Complexation enhances the stability of the system and effectively reduces the free phosphorus content.

[0037] If the content is too low (<2.5%), Al 3+ Insufficient phosphorus ions prevent phosphate from being fully precipitated or fixed, leading to increased leaching of free phosphorus.

[0038] If the content is too high (>3%), the excess Al in the system 3+ Possibly related to Ca 2+ Competition for adsorption sites affects the formation of hydration products, thereby reducing the overall mechanical properties of the material.

[0039] Dimethyl silicone oil (2.0–2.5%) and its viscosity (5000 cSt):

[0040] As a hydrophobic modifier, dimethyl silicone oil can improve the moisture resistance and durability of phosphogypsum-based materials and improve their pore structure.

[0041] Dimethyl silicone oil content is too low (<2.0%):

[0042] Phosphogypsum still has strong hygroscopic properties, which can lead to strength deterioration and affect durability due to humidity changes during long-term service.

[0043] Excessive dimethyl silicone oil content (>2.5%):

[0044] Due to the hydrophobic nature of silicone oil, excessive addition may affect the molding performance of the material, preventing it from being evenly distributed in the system, leading to increased porosity, decreased interfacial bonding, and thus reduced compressive strength.

[0045] In addition, excessive silicone oil content will reduce the hydrophilicity of the material, which will worsen the bonding interface between the subsequent cementing material and phosphogypsum and affect the early strength development.

[0046] Polyurethane resin (0.5–1.0%), solid content (≥60%):

[0047] As a reinforcing agent, waterborne polyurethane can improve the toughness and crack resistance of materials and enhance the density of the gel.

[0048] If the polyurethane resin content is too low (<0.5%):

[0049] Due to insufficient modification, the material has poor crack resistance and may develop microcracks during long-term service, reducing its durability.

[0050] If the polyurethane resin content is too high (>1.0%):

[0051] Excessive polyurethane may form a polymer-rich phase, leading to phase separation, which reduces the uniformity of the material and affects the hydration reaction, resulting in reduced strength.

[0052] In addition, the solid content of waterborne polyurethane emulsion is ≥60% to ensure sufficient modification effect. If the solid content is lower than this value, the effective components are insufficient, which will affect the mechanical improvement effect of the material.

[0053] Compared with the prior art, the present invention has the following characteristics:

[0054] Fixation of free phosphorus and free fluorine: This invention effectively reduces the leaching of free phosphorus and free fluorine in phosphogypsum-based materials through the synergistic effect of polyaluminum chloride, dimethyl silicone oil, and calcium chloride. Experiments show that the free phosphorus leaching of phosphogypsum-based materials prepared with the curing modifier of this invention is <0.09 mg / L and the free fluorine leaching is <0.20 mg / L, exhibiting outstanding environmentally friendly characteristics.

[0055] Significant improvement in mechanical properties: Through the synergistic effect of polyaluminum chloride and dimethyl silicone oil, this invention not only significantly improves the mechanical properties of phosphogypsum-based materials, achieving a 7-day compressive strength of 3–3.8 MPa and a 28-day compressive strength of 17–22 MPa, but also significantly surpasses the 7-day compressive strength of 1.5 MPa and the 28-day compressive strength of 8.2 MPa of unmodified phosphogypsum-based materials. The 28-day compressive strength is 107–168% higher than that of unmodified materials, ensuring its wide application in multiple fields.

[0056] In summary, this invention proposes a simple and economical modification method, employing a synergistic composite modification technology of polyaluminum chloride, dimethyl silicone oil, and calcium chloride to comprehensively improve the overall performance of phosphogypsum, particularly in terms of mechanical properties and environmental stability. This effectively solves common problems in phosphogypsum-based materials during use, such as strength degradation, poor moisture resistance, and environmental safety issues, thereby significantly enhancing its engineering application performance and ensuring its widespread application in multiple fields. It holds significant research and application value, especially in the development of high-performance and environmentally friendly building materials, and provides a scientific basis and strong support for the resource utilization of phosphogypsum. Detailed Implementation

[0057] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0058] The following are more detailed implementation examples, which further illustrate the technical solution of the present invention and the technical effects that can be obtained.

[0059] In the following embodiments, unless otherwise specified, the raw materials, reagents or processing techniques are all conventional commercial products or conventional processing techniques in the art.

[0060] In the following examples, phosphogypsum was purchased from Guizhou Gaobang Building Materials Co., Ltd., ordinary silicate concrete was purchased from Anhui Conch Cement Co., Ltd., anhydrous calcium chloride was product 100043-52-4 from Tianjin Damao Chemical Reagent Partnership (Limited Partnership), polyaluminum chloride was product PA05093 from Haichuangsai Technology Co., Ltd., dimethyl silicone oil was product LC-200DM5000 from Jinan Longcheng Organosilicon Co., Ltd., polyacrylamide was product 9003-05-8 from Tianjin Damao Chemical Reagent Partnership (Limited Partnership), polyurethane resin was product 2099 from Guangdong Yuemei Chemical Co., Ltd., lauryl alcohol polyoxyethylene ether AEO-9 was purchased from Jiangsu Haian Petrochemical Plant, and isomeric tridecyl alcohol polyoxyethylene ether E-1309 was purchased from Jiangsu Haian Petrochemical Plant.

[0061] Example 1:

[0062] A curing modifier for undisturbed phosphogypsum, the preparation method of which includes the following steps:

[0063] S1: The following components by weight percentage are used as raw materials:

[0064] Anhydrous calcium chloride: 30%;

[0065] Polyaluminum chloride: 2.8%;

[0066] Dimethyl silicone oil: 2.3%;

[0067] Water: 63.4%;

[0068] Polyacrylamide: 0.7%;

[0069] Polyurethane resin: 0.8%;

[0070] It also includes a cosolvent: the mass ratio of AEO-9 to E1309 is 1:2.5, and the total mass of AEO-9 and E1309 accounts for 10% of the total mass of dimethyl silicone oil;

[0071] Methanol: 0.5% of the mass of dimethyl silicone oil;

[0072] S2: Preheating and Preparation

[0073] Set the constant temperature water bath to 80°C and clean and dry the reaction beaker;

[0074] S3: Adding ingredients and initial mixing:

[0075] Add water to the beaker and start the high-speed stirring.

[0076] Add polyaluminum chloride, dimethyl silicone oil, polyacrylamide, and polyurethane resin in that order, then add AEO-9, E1309, and methanol.

[0077] S4: High-speed stirring and dissolving:

[0078] Stir for 20 minutes to ensure all components are completely dissolved and a homogeneous, transparent liquid is formed. Ensure the solution is stable and check for homogeneity to prevent precipitation.

[0079] S5: Cooling and Post-treatment:

[0080] After stirring, cool the mixture to room temperature and let it stand for 1 hour.

[0081] Example 2:

[0082] A curing modifier for undisturbed phosphogypsum, the preparation method of which differs from that of Example 1 only in that the following components by weight percentage are used as raw materials:

[0083] Anhydrous calcium chloride: 31.0%;

[0084] Polyaluminum chloride (PAC): 2.7%;

[0085] Dimethyl silicone oil (organosilicon): 2.2%;

[0086] Water (solvent): 62.6%;

[0087] Polyacrylamide (PAM): 0.9%;

[0088] Polyurethane resin: 0.6%;

[0089] Cosolvent: The mass ratio of AEO-9 to E1309 is 1:2.5, and the total mass of AEO-9 and E1309 accounts for 10% of the total mass of dimethyl silicone oil;

[0090] Methanol: 0.5% of the mass of dimethyl silicone oil.

[0091] The rest is the same as in Example 1.

[0092] Example 3:

[0093] A curing modifier for undisturbed phosphogypsum, the preparation method of which differs from that of Example 1 only in that the following components by weight percentage are used as raw materials:

[0094] Anhydrous calcium chloride: 32.0%;

[0095] Polyaluminum chloride (PAC): 2.5%;

[0096] Dimethyl silicone oil (organosilicon): 2.0%;

[0097] Water (solvent): 62.2%;

[0098] Polyacrylamide (PAM): 0.6%;

[0099] Polyurethane resin: 0.7%;

[0100] Cosolvent: The mass ratio of AEO-9 to E1309 is 1:2.5, and the total mass of AEO-9 and E1309 accounts for 10% of the total mass of dimethyl silicone oil;

[0101] Methanol: 0.5% of the mass of dimethyl silicone oil.

[0102] The rest is the same as in Example 1.

[0103] Example 4:

[0104] A curing modifier for undisturbed phosphogypsum, the preparation method of which differs from that of Example 1 only in that the following components by weight percentage are used as raw materials:

[0105] Anhydrous calcium chloride: 33.0%;

[0106] Polyaluminum chloride (PAC): 2.9%;

[0107] Dimethyl silicone oil (organosilicon): 2.4%;

[0108] Water (solvent): 60.4%;

[0109] Polyacrylamide (PAM): 0.8%;

[0110] Polyurethane resin: 0.5%;

[0111] Cosolvent: The mass ratio of AEO-9 to E1309 is 1:2.5, and the total mass of AEO-9 and E1309 accounts for 10% of the total mass of dimethyl silicone oil;

[0112] Methanol: 0.5% of the mass of dimethyl silicone oil.

[0113] The rest is the same as in Example 1.

[0114] Comparative Example 1:

[0115] A curing modifier for undisturbed phosphogypsum, the preparation method of which differs from that in Example 3 only in that:

[0116] Anhydrous calcium chloride was not added, and the relative amounts of the remaining components remained unchanged.

[0117] The rest is the same as in Example 1.

[0118] Comparative Example 2:

[0119] A curing modifier for undisturbed phosphogypsum, the preparation method of which differs from that in Example 3 only in that:

[0120] No polyaluminum chloride was added, and the relative amounts of the remaining components remained unchanged.

[0121] The rest is the same as in Example 1.

[0122] Comparative Example 3:

[0123] A curing modifier for undisturbed phosphogypsum, the preparation method of which differs from that in Example 3 only in that:

[0124] No dimethyl silicone oil was added, and the relative amounts of the remaining components remained unchanged.

[0125] The rest is the same as in Example 1.

[0126] Comparative Example 4:

[0127] A curing modifier for undisturbed phosphogypsum, the preparation method of which differs from that in Example 3 only in that:

[0128] Anhydrous calcium chloride was added, but polyaluminum chloride and dimethyl silicone oil were not added, and the relative amounts of the remaining components remained unchanged.

[0129] The rest is the same as in Example 1.

[0130] Comparative Example 5:

[0131] A curing modifier for undisturbed phosphogypsum, the preparation method of which differs from that in Example 3 only in that:

[0132] Polyaluminum chloride was added, but anhydrous calcium chloride and dimethyl silicone oil were not added, and the relative amounts of the remaining components remained unchanged.

[0133] The rest is the same as in Example 1.

[0134] Comparative Example 6:

[0135] A curing modifier for undisturbed phosphogypsum, the preparation method of which differs from that in Example 3 only in that:

[0136] Dimethyl silicone oil was added, but anhydrous calcium chloride and polyaluminum chloride were not added, and the relative amounts of the remaining components remained unchanged.

[0137] The rest is the same as in Example 1.

[0138] Comparative Example 7:

[0139] A curing modifier for undisturbed phosphogypsum, the preparation method of which differs from that in Example 3 only in that:

[0140] Anhydrous calcium chloride, polyaluminum chloride, and dimethyl silicone oil were not added, and the relative amounts of the remaining components remained unchanged.

[0141] The rest is the same as in Example 1.

[0142] Application Examples:

[0143] This embodiment is used to examine the application effect of the above embodiments and comparative examples in phosphogypsum. The test methods include:

[0144] A method for adding a curing modifier to undisturbed phosphogypsum includes the following steps:

[0145] 1) Mix 5.7g of undisturbed phosphogypsum curing modifier with 570g of phosphogypsum with a water content of 25% and 30g of concrete to obtain mixed soil; wherein, based on the principle that the amount of water in the modifier is consistent with the amount of phosphogypsum, the amount of modifier in comparative examples 1-7 is determined according to the amount in example 3.

[0146] 2) Sample Preparation Process: A clay sampler (model 39.1mm, including a three-part membrane, compaction hammer, base, top cap, guide sleeve, etc.) purchased from Anhui Hengboli Instrument Technology Co., Ltd. was used to prepare the test blocks. The designed test block specifications were cylindrical remolded soil blocks with a diameter of 39.1mm and a height of 80mm. The specific preparation steps are as follows:

[0147] 2-1) Preparation of sample materials:

[0148] Mix all components thoroughly to ensure uniform material distribution.

[0149] 2-2) Sample layer filling:

[0150] Using a clay sampler, the mixed soil is divided into four layers, with an appropriate amount of material added to each layer to ensure that each layer is of uniform thickness.

[0151] 2-3) Layered compaction:

[0152] Each layer of material is compacted 15 times using a standard compaction hammer to ensure soil density and reduce voids between layers. Relevant parameters are as follows:

[0153] Hammer weight: 2.5kg;

[0154] Hammer base diameter: 39.1mm (matching the three valves);

[0155] Free fall height: 300mm;

[0156] Specimen block height: 80mm;

[0157] Number of fill layers: 4;

[0158] Thickness of each filler layer (before loosening): approximately 20mm;

[0159] Thickness of each filler layer (after compaction): approximately 18-19 mm;

[0160] 2-4) Demolding of test blocks:

[0161] After compaction, demold and ensure that the surface of the test block is smooth and free of cracks or defects.

[0162] 2-5) Maintenance process:

[0163] After demolding, the specimen is wrapped and sealed with plastic film and placed in a constant temperature and humidity curing chamber to maintain suitable temperature and humidity conditions (20℃, 95% relative humidity) to ensure the stability of the specimen.

[0164] The testing standards include:

[0165] Compressive strength: The test standard is based on GB / T 17671-2021 "Test Method for Strength of Cement Mortar";

[0166] Free fluoride content: Sample extraction was performed using the HJ 557-2010 horizontal oscillation method to ensure that the test results met the solid waste leaching toxicity evaluation standards; ion-selective electrode method (ISE) was used, combined with an A214 ISE main unit + 9609BNWP fluoride ion electrode, to efficiently determine free fluoride.

[0167] Free phosphorus content: The test standard is HJ 700-2014 "Determination of Phosphate in Water - Ammonium Molybdate Spectrophotometric Method".

[0168] Test principle: The ammonium molybdate spectrophotometric method is used to detect phosphate (PO4) 3- Under acidic conditions, it reacts with ammonium molybdate to form phosphomolybdic heteropoly acid, which then forms a blue complex under the reducing action of ascorbic acid (or benzidine). It can be detected by a UV-Vis spectrophotometer at 880 nm, and the phosphate content can be calculated based on the absorbance.

[0169] Softening coefficient: The test standard is GB / T 50266-2013 "Test Methods for Building Gypsum and its Products";

[0170] Freeze-thaw cycle count: The test standard is GB / T 50082-2009 "Test methods for long-term performance and durability of ordinary concrete".

[0171] The test results are shown in Table 1. The control group consisted of samples prepared by the above-mentioned addition method but without the addition of the original phosphogypsum curing modifier.

[0172] Table 1 Summary of Experimental Results

[0173]

[0174]

[0175] Table 2 Comparison of Existing Phosphogypsum Modification Technologies

[0176]

[0177]

[0178] Table 3 Performance Indicators

[0179]

[0180] Example 4 Analysis – Optimal Formula

[0181] Highest strength: The compressive strength reaches 22MPa after 28 days, far exceeding the control group (8.2MPa), and the relative improvement rate is the highest (168.3%), making it suitable for engineering applications with high strength requirements.

[0182] The material exhibits the best durability: it has the highest softening coefficient (0.8) and the highest number of freeze-thaw cycles (60 times), indicating that it performs well in humid environments and cold regions and has strong resistance to hydrolysis and freeze-thaw damage.

[0183] Overall performance is balanced: the phosphorus and fluorine leaching amounts are slightly higher than those in Examples 1-3, but still much lower than those in the control group, ensuring environmental performance while guaranteeing the strength and durability of the material.

[0184] Optimization points: The higher content of anhydrous calcium chloride (33%) and dimethyl silicone oil (2.4%) improves the hydration reaction efficiency and water resistance of the material, making it more stable in humid and cold environments.

[0185] Conclusion: The formulation in Example 4 balances strength, durability and environmental adaptability, making it the most suitable solution for practical engineering applications, especially performing best in extreme environments such as high humidity and extreme cold.

[0186] Comparative analysis

[0187] Comparative Example 1 (without calcium chloride)

[0188] Impacts: Significant decrease in strength (14 MPa), increased phosphorus and fluorine leaching, and decreased environmental stability.

[0189] Problem: The lack of calcium chloride leads to reduced strength and increased leaching of contaminants.

[0190] Comparative Example 2 (without polyaluminum chloride)

[0191] Impact: Strength decreases more significantly (10 MPa), phosphorus and fluorine leaching increases further, and durability deteriorates.

[0192] Problem: Without PAC, the stability and strength of the material are reduced, and it cannot meet the requirements for high performance.

[0193] Comparative Example 3 (without dimethyl silicone oil)

[0194] Impact: Strength decreases to 16 MPa, durability (softening coefficient and freeze-thaw resistance) decreases, and phosphorus and fluorine leaching increases slightly.

[0195] Problem: The lack of organosilicon leads to poorer water resistance and decreased long-term stability of the material.

[0196] This experimental scheme is superior to traditional modification techniques and national standards in terms of compressive strength, phosphorus fixation, and durability, and has outstanding engineering application value.

[0197] Analysis Conclusion

[0198] The role of calcium chloride (Comparative Example 7 and Comparative Example 4)

[0199] Comparative Example 4 (containing only calcium chloride) was slightly better than Comparative Example 7 (without modifier) ​​in terms of compressive strength, softening coefficient, and freeze-thaw cycle performance, but its phosphorus fixation capacity was insufficient. This indicates that calcium chloride contributes to strength and fluorine curing, but its effect on curing pollutants is limited.

[0200] The role of polyaluminum chloride (comparative example and comparative example 5)

[0201] Comparative Example 5 (containing only polyaluminum chloride) was significantly better than Comparative Example 7 in terms of strength and phosphorus curing, but its effect on fluorine curing was average, indicating that polyaluminum chloride mainly improves strength and significantly reduces phosphorus leaching.

[0202] The role of dimethyl silicone oil (Comparative Example 7 and Comparative Example 6)

[0203] Comparative Example 6 (containing only dimethyl silicone oil) showed improved softening coefficient and freeze-thaw cycle performance, but limited improvement in compressive strength, indicating that dimethyl silicone oil mainly improves durability and does not contribute much to strength.

[0204] Synergistic effect of three components (Example 3 and Comparative Example 1)

[0205] Example 3 (containing calcium chloride + polyaluminum chloride + dimethyl silicone oil) was significantly better than Comparative Example 1 (without calcium chloride), indicating that the polyaluminum chloride + dimethyl silicone oil environment can enhance the effect of calcium chloride, and the synergistic effect of the three can improve strength, durability and contaminant curing ability.

[0206] in conclusion

[0207] The effects of a single component are limited, while the synergistic effect of three components is optimal.

[0208] Calcium chloride performs better in the presence of polyaluminum chloride and dimethyl silicone oil, indicating that its performance is affected by the system environment.

[0209] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A curing modifier for undisturbed phosphogypsum, characterized in that, Includes the following components and their weight percentages: Lauryl alcohol polyoxyethylene ether, isotridecyl alcohol polyoxyethylene ether and methanol; The mass ratio of lauryl alcohol polyoxyethylene ether to isotridecyl alcohol polyoxyethylene ether is 1:(2-3); The total mass of the lauryl alcohol polyoxyethylene ether and isotretinoin polyoxyethylene ether is 8-12% of the mass of dimethyl silicone oil.

2. The undisturbed phosphogypsum curing modifier according to claim 1, characterized in that, The mass content of aluminum oxide in the polyaluminum chloride is not less than 30%.

3. The undisturbed phosphogypsum curing modifier according to claim 1, characterized in that, The viscosity of the dimethyl silicone oil is 4500-5500 cSt.

4. The undisturbed phosphogypsum curing modifier according to claim 1, characterized in that, The molecular weight of the polyacrylamide is not less than 5 million.

5. The undisturbed phosphogypsum curing modifier according to claim 1, characterized in that, The polyurethane resin is an aqueous polyurethane emulsion with a solid content of 50% to 60%.

6. The undisturbed phosphogypsum curing modifier according to claim 1, characterized in that, The mass ratio of lauryl alcohol polyoxyethylene ether to isotretinoin polyoxyethylene ether is 1:2.5, and the total mass of lauryl alcohol polyoxyethylene ether and isotretinoin polyoxyethylene ether accounts for 10% of the total mass of dimethyl silicone oil.

7. The undisturbed phosphogypsum curing modifier according to claim 1, characterized in that, The amount of methanol used is 0.3 to 0.8% of the mass of dimethyl silicone oil.

8. A method for preparing the undisturbed phosphogypsum curing modifier as described in any one of claims 1 to 7, characterized in that, include: The mixture of calcium chloride, polyaluminum chloride, dimethyl silicone oil, polyacrylamide, polyurethane resin, water, lauryl alcohol polyoxyethylene ether, isotridecyl alcohol polyoxyethylene ether, and methanol is heated and stirred at 80–85°C, and then allowed to stand.

9. The application of the undisturbed phosphogypsum curing modifier as described in any one of claims 1 to 7, characterized in that, The unprocessed phosphogypsum curing modifier is used to prepare phosphogypsum-based materials. This includes: mixing phosphogypsum with cementing materials and undisturbed phosphogypsum curing modifier until homogeneous, and then allowing it to stand.

10. The application of the undisturbed phosphogypsum curing modifier according to claim 9, characterized in that, The amount of the original phosphogypsum curing modifier added is 1 to 3% of the mass of phosphogypsum.

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