Composite water reducing agent suitable for phosphogypsum-red mud-based cementing material and preparation method of composite water reducing agent

Abstract

The invention discloses a composite water reducing agent suitable for an ardealite-red mud-based cementing material and a preparation method thereof. The composite water reducing agent comprises a modified polycarboxylic acid water reducing agent, an ion complexing agent, an alcohol amine compound, an alcohol compound and the balance of a solvent. According to the modified polycarboxylate superplasticizer disclosed by the invention, a phosphate group, an amide group and a sulfonic group are introduced into the structure of the polycarboxylate superplasticizer as functional groups through a water solution free radical copolymerization method, and then are compounded with small molecular monomers such as an ion complexing agent and the like; the dispersing performance of the water reducing agent and the adaptability of the water reducing agent to an ardealite-slag-red mud system are further improved. The composite water reducing agent is suitable for the phosphogypsum-red mud based cementing material, and has the advantages of enhancing the dispersity of each component in a system, increasing the contact area of phosphogypsum and red mud particles with slag, promoting hydration of the cementing material, and improving the 3d, 7d and 28d strength of the cementing material.

Description

Technical Field

[0001] The present invention belongs to the technical field of water reducing agents, and particularly relates to a composite water reducing agent applicable to a phosphogypsum - red mud based cementitious material and a preparation method thereof. Background Art

[0002] Phosphogypsum is a by - product produced during the production of phosphoric acid in the phosphochemical industry. It is a gray powdery substance, and its main component is calcium sulfate dihydrate (CaSO 4 ·2H 2 0). In addition, it also contains various heavy metals. At present, the utilization rate of phosphogypsum is relatively low, and it is mostly treated in the form of simple stacking, which not only occupies land but also pollutes the environment. How to improve the utilization rate of phosphogypsum has become an urgent problem.

[0003] Red mud is an industrial waste residue produced during the smelting of alumina by the Bayer process. It has poor engineering properties, strong alkalinity, and a high content of harmful substances. Similar to phosphogypsum, the current disposal method of red mud is also mainly simple stacking, with a very low utilization rate. Therefore, the reasonable utilization of red mud is also of great significance.

[0004] At present, many studies have applied phosphogypsum, slag or red mud to cementitious materials. However, various currently popular water reducing agents are not compatible with phosphogypsum - red mud based cementitious materials. In experiments, when using ordinary polycarboxylic water reducing agents as dispersants, problems such as bleeding, poor early strength, slow hydration rate, and poor strength at each age stage occurred in the cementitious material specimens.

[0005] It is difficult to solve the problems existing in the above - mentioned system relying on the existing polycarboxylic water reducing agents. Therefore, it is particularly necessary to modify the polycarboxylic water reducing agent by introducing functional groups suitable for the system through the method of aqueous solution free - radical copolymerization and compound it, so as to invent a composite water reducing agent applicable to phosphogypsum - red mud based cementitious materials. Summary of the Invention

[0006] To solve the above - mentioned technical problems, the present invention provides a composite water reducing agent applicable to a phosphogypsum - red mud based cementitious material and a preparation method thereof.

[0007] The present invention is achieved through the following technical solutions.

[0008] The composite water reducing agent applicable to a phosphogypsum - red mud based cementitious material provided by the present invention, taking weight percentage as the unit, its components include: 22% - 27% modified polycarboxylic water reducing agent, 7% - 12% ionic complexing agent, 6% - 11% alkanolamine compounds, 7% - 15% alcohol compounds, and the rest is solvent.

[0009] Preferably, the modified polycarboxylic water reducing agent is prepared by reacting at 50 - 60 °C for 150 - 180 min.

[0010] Preferably, the components of the modified polycarboxylate water reducer are in parts by mass and include: 40-50 parts of methacrylic acid, 15-20 parts of methylenediphosphonic acid, 18-22 parts of dimethylformamide propane sulfonate, 2-4 parts of a chain transfer agent, 8-10 parts of an oxidant, 1-2 parts of a reducing agent, 40-45 parts of a sodium hydroxide solution, 400-450 parts of solution d, and 380-435 parts of water.

[0011] Preferably, solution d is obtained by mixing allyl polyoxyethylene ether 2400 and ethylene glycol mono vinyl polyethylene glycol ether 2400 in a mass ratio of 1:1, and the mass fraction of the sodium hydroxide solution is 30%.

[0012] Preferably, the chain transfer agent includes at least one of mercaptopropionic acid and mercaptoacetic acid; the reducing agent is ascorbic acid, and the oxidant is a mixture of hydrogen peroxide and ammonium persulfate in a mass ratio of 1:5.

[0013] Preferably, the alkanolamine compound includes at least one of triethanolamine and triisopropanolamine, and the ionic complexing agent is hydroxyethane diphosphonic acid.

[0014] Preferably, the alcohol compound includes at least one of polyethylene glycol and polyvinyl alcohol, and the solvent is water.

[0015] Preferably, the pH of the modified polycarboxylate water reducer is 6.5-7.5, and the solid content is 30-55%.

[0016] Preferably, the dosage of the composite water reducer is 1.0-1.4% of the mass of the phosphogypsum-red mud based cementitious material.

[0017] A preparation method of a composite water reducer includes the following steps:

[0018] S1: Mix the alkanolamine and alcohol compounds, add them to water, and stir well to dissolve to form a solution;

[0019] S2: Take the modified polycarboxylate water reducer and the ionic complexing agent, add them to water in sequence, and stir well to form a solution;

[0020] S3: Mix the solutions obtained in steps S1 and S2 evenly to obtain the composite water reducer.

[0021] The beneficial effects of the present invention are as follows:

[0022] The composite water reducer of the present invention can enhance the dispersibility of each component in the system, increase the contact area between phosphogypsum and red mud particles and slag, promote the hydration of the cementitious material, and improve the 3d, 7d, and 28d strengths of the cementitious material.

[0023] Phosphogypsum, as a cementitious material, has the characteristics of slow hydration rate, slow setting, and poor early strength. The water reducer prepared by the present invention has the advantages of accelerating the hydration of phosphogypsum, accelerating the setting rate, and improving the early strength.

[0024] The utilization of iron and aluminum phases in red mud is relatively difficult, and the dispersion effect of ordinary polycarboxylic acid-based water reducers on it is generally poor. The water reducer prepared by the present invention has a good dispersion effect on red mud, and hydroxyethylidene diphosphonic acid and alkanolamine organic compounds are added, which promote the hydration of components such as iron phase and aluminum phase in red mud, and can better utilize red mud. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the process flow chart of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0026] The technical solution of the present invention will be further described below, but the scope of protection is not limited thereto.

[0027] As Figure 1 shown, a composite water reducer applicable to phosphogypsum-red mud-based cementitious materials, its components by weight percentage include: 22%-27% modified polycarboxylic acid water reducer, 7%-12% ion complexing agent, 6%-11% alkanolamine compounds, 7%-15% alcohol compounds, and the rest is solvent.

[0028] The modified polycarboxylic acid water reducer is prepared by reacting at 50-60 °C for 150-180 min.

[0029] The modified polycarboxylic acid water reducer, by mass, its components include: 40-50 parts of methacrylic acid, 15-20 parts of methylene diphosphonic acid, 18-22 parts of dimethylformamide propane sulfonate, 2-4 parts of chain transfer agent, 8-10 parts of oxidant, 1-2 parts of reductant, 40-45 parts of sodium hydroxide solution, 400-450 parts of solution d, and 380-435 parts of water.

[0030] The solution d is obtained by mixing allyl polyoxyethylene ether 2400 and ethylene glycol mono vinyl polyethylene glycol ether 2400 in a mass ratio of 1:1, and the mass fraction of the sodium hydroxide solution is 30%.

[0031] The chain transfer agent includes at least one of mercaptopropionic acid and mercaptoacetic acid; the reductant is ascorbic acid.

[0032] The oxidant is a mixture of hydrogen peroxide and ammonium persulfate in a mass ratio of 1:5.

[0033] The alkanolamine compounds include at least one of triethanolamine and triisopropanolamine, and the ion complexing agent is hydroxyethylidene diphosphonic acid.

[0034] The alcohol compound includes at least one of polyethylene glycol and polyvinyl alcohol, and the solvent is water.

[0035] The pH of the modified polycarboxylate water reducer is 6.5 - 7.5, and the solid content is 30 - 55%. Preferably, the pH is 7 and the solid content is 45%.

[0036] The dosage of the composite water reducer is 1.0 - 1.4% of the mass of the phosphogypsum - red mud - based cementitious material.

[0037] The modified polycarboxylate water reducer plays a major water - reducing effect. In addition to having a certain dispersing effect, the other components of the composite water reducer mainly promote the participation of iron, aluminum and other mineral phases in the red mud in the hydration reaction.

[0038] The modified polycarboxylate water reducer adopted in the present invention uses methacrylic acid as the polymer main chain, connects the unsaturated polyether side chain to the main chain through a chain transfer agent, and then introduces phosphate groups, amide groups and sulfonic acid groups under the initiation of an oxidation - reduction initiator.

[0039] The dosage of methacrylic acid will affect the length of the main chain of the water reducer, thereby affecting the side - chain density. When the dosage of methacrylic acid is too small, the length of the copolymer main chain generated is too short, and the number of introduced anionic groups is insufficient, resulting in too small a zeta negative potential, which is not conducive to the adsorption of the water reducer on the cementitious material particles; when the dosage of methacrylic acid is too large, the length of the copolymer main chain generated is too long, resulting in a decrease in the density of the unsaturated polyether side chain, which has an adverse effect on the dispersing effect of the water reducer. In the present invention, the dosage of methacrylic acid is controlled to be n 1 (methacrylic acid):n 2 (polyether side chain)=4.0 - 5.0.

[0040] The chain transfer agent can graft the unsaturated polyether side chain onto the methacrylic acid main chain. The dosage of the chain transfer agent will affect the length of the main chain of the water reducer, and too long or too short main chains will have an adverse effect on the dispersing performance. To maintain good dispersibility, in the present invention, the dosage of the chain transfer agent is controlled to be n 1 (chain transfer agent):n 2 (polyether side chain)=0.4 - 0.6.

[0041] The oxidant can provide the initial free radicals required for the reaction, open the carbon - carbon double bonds in methacrylic acid and the unsaturated polyether side chain, thereby initiating a free - radical chain reaction. However, the usage amount of the oxidant needs to be controlled. Too many initial free radicals will increase the active sites in the copolymer molecular structure, reduce the molecular weight of the water reducer, and reduce its dispersing performance. In the present invention, the dosage of the oxidant is controlled to be m 1 (oxidant):m 2 (polyether side chain)=1.2% - 1.25%.

[0042] The reducing agent forms a redox initiation system in cooperation with the oxidizing agent in the system, forming a certain number of free radicals. Therefore, its application rules are similar to those of the oxidizing agent. If the dosage is too much, it will affect the initiation effect of the redox system and make the dispersion effect of the water reducer worse. In the present invention, the dosage of the reducing agent is controlled to be m 1 (reducing agent):m 2 (polyether side chain)=0.3% - 0.45%.

[0043] The functional monomers used in the present invention are sodium dimethylformamide propane sulfonate and methylene diphosphonic acid, which provide amide groups, sulfonic acid groups and phosphonic acid groups for the modified polycarboxylate water reducer respectively.

[0044] Under the initiation of the redox agent and heating, methylene diphosphonic acid undergoes a chemical reaction with the unsaturated double bond on the polyether side chain, thereby introducing a phosphoric acid group into the water reducer molecule. The presence of the phosphoric acid group provides a higher absolute value of the zeta potential, which can better combine with cations in the cementitious material system and improve the dispersion performance. At the same time, the phosphoric acid group has a better complexing ability with calcium ions, which ensures the dispersion of phosphogypsum.

[0045] Sodium dimethylformamide propane sulfonate provides amide groups and sulfonic acid groups for the water reducer copolymer under the initiation. The introduction of the amide group can shorten the setting time of the cementitious material, complex metal ions, promote the hydration of each component and the formation of hydration products, and has a promoting effect on the early strength; the presence of the sulfonic acid group can effectively target the red mud component in the system, improve the dispersion effect on red mud and the hydration rate of the mineral phase. At the same time, the presence of the sulfonic acid group will change the morphology of the early-formed ettringite into short needles and arrange them more densely, which has a positive impact on the setting speed and early strength.

[0046] In the present invention, when preparing the modified polycarboxylate water reducer, the reaction temperature is controlled at 50 - 60°C. Maintaining a certain temperature is beneficial to better break the ionic bond and accelerate the reaction rate. In order not to affect the molecular structure of the copolymer, the reaction temperature cannot be too high, so the reaction temperature is controlled at 50 - 60°C.

[0047] In the present invention, when preparing the modified polycarboxylate water reducer, the reaction time is controlled at 150 - 180 min by the method of uniform dropping. If the reaction time is too short, the reaction will be incomplete, affecting the dispersion performance of the water reducer. The raw materials are divided into three groups. The first group is methacrylic acid and the chain transfer agent, the second group is the reducing agent, and the third group is methylene diphosphonic acid, sodium dimethylformamide propane sulfonate, allyl polyoxyethylene ether, ethylene glycol mono vinyl polyethylene glycol ether and the oxidizing agent. After the three groups are dissolved in water respectively, the first and second groups are uniformly dropped into the third group within 150 - 180 min.

[0048] Ionic complexing agents can thicken the diffusion layer of micelles, increase the zeta potential, improve the dispersibility, and avoid the problem that the components of red mud are difficult to continuously hydrate due to agglomeration. At the same time, hydroxyethylidene diphosphonic acid, as an ionic complexing agent, can complex Ca 2+ 、Fe 3+ and other metal ions in the cementitious material, accelerate the dissolution of metal ions, promote the participation of red mud mineral phases in the hydration reaction, thereby accelerating the setting rate of the system and improving the early strength of the cementitious material.

[0049] Alkanolamine compounds are organic compounds containing hydroxyl and amino groups. The molecular structure has both hydrophilic and hydrophobic groups at the same time. This structure makes alkanolamine compounds have a good dispersion effect and can accelerate the early hydration of the system. The effect of alkanolamine compounds is greatly affected by the type of sulfate carrier. In the cementitious system targeted by the present invention, sulfate mainly exists in the form of calcium sulfate dihydrate, and its dissolution rate is slow during hydration. In this case, alkanolamine compounds have a strong promoting effect on the dissolution of iron and aluminum phases in red mud and slag, and improve the strength at each age.

[0050] In the present invention, alkanol compounds are added as anti-freezing components. Compared with inorganic salt anti-freezing agents, alkanol compounds have a lower dosage, good anti-freezing effect, and no damage to the durability of the cementitious material. At the same time, alkanol compounds can promote the dissolution of mineral phases in each component, accelerate hydration, and have a promoting effect on the strength development of the cementitious material at each age.

[0051] The preparation steps of the composite water reducer are as follows:

[0052] S1: Mix alkanolamine and alkanol compounds and add them to water, and stir well to dissolve them to form a solution;

[0053] S2: Take a modified polycarboxylate water reducer and an ionic complexing agent, add them to water in turn and stir well to form a solution;

[0054] S3: Mix the solutions obtained in steps S1 and S2 evenly, and the mixed solution is the composite water reducer.

[0055] The composite water reducer is applicable to phosphogypsum-red mud-based cementitious materials. Considering comprehensively from the perspectives of environmental protection, solid waste utilization and strength, the effect is better when the phosphogypsum content in this kind of cementitious material is 40%-45%, the slag content is 30%-35%, the red mud content is 10%-20%, and the quicklime content is 1%-2%.

[0056] Example 1

[0057] This embodiment provides a preparation scheme of a modified polycarboxylate water reducer, which is made from the following raw materials in corresponding mass parts: 65 parts of methacrylic acid, 430 parts in total of allyl polyoxyethylene ether 2400 and ethylene glycol mono vinyl polyethylene glycol ether 2400 in a mass ratio of 1:1, 17 parts of methylene diphosphonic acid, 19 parts of dimethylformamide propane sulfonate, 6 parts of mercaptopropionic acid, 1 part of hydrogen peroxide, 5 parts of ammonium persulfate, 2 parts of ascorbic acid, 42 parts of 30% sodium hydroxide alkaline solution, and 422 parts of water.

[0058] The preparation steps are as follows:

[0059] S1: Prepare the raw materials, and weigh the above raw materials according to the mass ratio with a beaker and an electronic scale for later use.

[0060] S2: Add methylene diphosphonic acid, dimethylformamide propane sulfonate, allyl polyoxyethylene ether, ethylene glycol mono vinyl polyethylene glycol ether, hydrogen peroxide and ammonium persulfate into water, and stir well to dissolve to obtain solution a.

[0061] S3: Add methacrylic acid and mercaptopropionic acid into water, and stir well to dissolve to obtain solution b.

[0062] S4: Add ascorbic acid into water, and stir well to dissolve to obtain solution c.

[0063] S5: Heat solution a to 50 °C and keep the temperature constant. Slowly and uniformly drip solutions b and c into solution a at the same time, control the dripping time within 150 min, and keep stirring for 30 min after the titration is completed to allow the components to react fully and undergo an aqueous solution free radical copolymerization reaction.

[0064] S6: After the reaction is completed, add 30% sodium hydroxide alkaline solution to the solution to neutralize it to pH = 7, and then add water to make the solid content 45% to obtain the modified polycarboxylate water reducer.

[0065] Example 2

[0066] This embodiment provides a preparation scheme of modified polycarboxylic acid, which is made from the following raw materials in corresponding mass parts: 62 parts of methacrylic acid, 450 parts in total of allyl polyoxyethylene ether 2400 and ethylene glycol mono vinyl polyethylene glycol ether 2400 in a mass ratio of 1:1, 20 parts of methylene diphosphonic acid, 20 parts of dimethylformamide propane sulfonate, 6 parts of mercaptoacetic acid, 0.8 part of hydrogen peroxide, 4 parts of ammonium persulfate, 2 parts of ascorbic acid, 45 parts of 30% sodium hydroxide alkaline solution, and 430 parts of water.

[0067] The preparation steps are as follows:

[0068] S1: Prepare the raw materials, and weigh the above raw materials according to the mass ratio with a beaker and an electronic scale for later use.

[0069] S2: Add methylenediphosphonic acid, sodium dimethylaminopropanesulfonate, methyl allyl polyoxyethylene ether, ethylene glycol mono vinyl polyethylene glycol ether, hydrogen peroxide and ammonium persulfate into water, and stir well to dissolve to obtain solution a.

[0070] S3: Add methacrylic acid and mercaptoacetic acid into water, and stir well to dissolve to obtain solution b.

[0071] S4: Add ascorbic acid into water, and stir well to dissolve to obtain solution c.

[0072] S5: Heat solution a to 60 °C and keep the temperature constant. Slowly and uniformly drip solutions b and c into solution a at the same time, control the dripping time within 180 min, and keep stirring for 30 min after the titration is completed to allow the components to react fully and undergo an aqueous solution free radical copolymerization reaction.

[0073] S6: After the reaction is completed, add an alkaline solution of 30% sodium hydroxide to the solution to neutralize it to pH = 7, and then add water to make the solid content 45% to obtain a modified polycarboxylic acid type water reducing agent.

[0074] Example 3

[0075] This example provides a composite water reducing agent applicable to a phosphogypsum - red mud based cementitious material, including by weight percentage: 22.5% modified polycarboxylic acid water reducing agent, 7.5% hydroxyethylidene diphosphonic acid, 10% triethanolamine, 9% polyethylene glycol, 51% water.

[0076] The modified polycarboxylic acid water reducing agent used in this example is prepared from Example 1.

[0077] The compounding steps of the composite water reducing agent are as follows:

[0078] S1: Add triethanolamine and polyethylene glycol into water and stir well to dissolve to form a solution.

[0079] S2: Take the modified polycarboxylic acid water reducing agent and hydroxyethylidene diphosphonic acid, and add them into water in sequence and stir well to form a solution.

[0080] S3: Mix the solutions obtained in the two steps evenly, and the mixed solution is the composite water reducing agent.

[0081] The raw materials of the phosphogypsum - red mud based cementitious material include by weight percentage: 45% phosphogypsum, 33% slag, 20% red mud, 2% quicklime.

[0082] The dosage of the composite water reducing agent is 1.3ωt% of the dosage of the cementitious material, and the water - binder ratio is 0.30.

[0083] Example 4

[0084] This embodiment provides a composite water reducer applicable to phosphogypsum - red mud - based cementitious materials. The raw materials include, by weight percentage: 25% modified polycarboxylic acid - type water reducer, 9% hydroxyethylidene diphosphonic acid, 9% triisopropanolamine, 13% polyvinyl alcohol, and 44% water.

[0085] The modified polycarboxylic acid used in this embodiment is prepared from Example 1.

[0086] The compounding steps of the composite water reducer are as follows:

[0087] S1: Add triisopropanolamine and polyvinyl alcohol to water and stir well to dissolve them to form a solution.

[0088] S2: Take the modified polycarboxylic acid water reducer and hydroxyethylidene diphosphonic acid, and add them to water in sequence and stir well to form a solution.

[0089] S3: Mix the solutions obtained from the two steps evenly, and the mixed solution is the composite water reducer.

[0090] The raw materials of the phosphogypsum - red mud - based cementitious materials include, by weight percentage: 45% phosphogypsum, 33% slag, 20% red mud, and 2% quicklime.

[0091] The dosage of the composite water reducer is 1.2ωt% of the cementitious material dosage, and the water - cement ratio is 0.30.

[0092] Example 5

[0093] This embodiment provides a composite water reducer applicable to phosphogypsum - red mud - based cementitious materials. The raw materials include, by weight percentage: 24% modified polycarboxylic acid - type water reducer, 8% hydroxyethylidene diphosphonic acid, 12% triethanolamine, 10% polyvinyl alcohol, and 46% water.

[0094] The modified polycarboxylic acid used in this embodiment is prepared from Example 2.

[0095] The compounding steps of the composite water reducer are as follows:

[0096] S1: Add triethanolamine and polyvinyl alcohol to water and stir well to dissolve them to form a solution.

[0097] S2: Take the modified polycarboxylic acid water reducer and hydroxyethylidene diphosphonic acid, and add them to water in sequence and stir well to form a solution.

[0098] S3: Mix the solutions obtained from the two steps evenly, and the mixed solution is the composite water reducer.

[0099] The raw materials of the phosphogypsum - red mud - based cementitious materials include, by weight percentage: 45% phosphogypsum, 33% slag, 20% red mud, and 2% quicklime.

[0100] The dosage of the composite water reducer is 1.2ωt% of the dosage of the cementitious material, and the water-cement ratio is 0.30.

[0101] Example 6

[0102] This example provides a composite water reducer applicable to phosphogypsum-red mud-based cementitious materials. The raw materials include, by weight percentage: 27% modified polycarboxylic acid type water reducer, 10% hydroxyethylidene diphosphonic acid, 7% triisopropanolamine, 8% polyvinyl alcohol, and 48% water.

[0103] The modified polycarboxylic acid used in this example is prepared from Example 2.

[0104] The compounding steps of the composite water reducer are as follows:

[0105] S1: Add triisopropanolamine and polyvinyl alcohol to water and stir well to dissolve them to form a solution.

[0106] S2: Take the modified polycarboxylic acid water reducer and hydroxyethylidene diphosphonic acid, and add them to water in sequence and stir well to form a solution.

[0107] S3: Mix the solutions obtained in the two steps evenly, and the mixed solution is the composite water reducer.

[0108] The raw materials of the phosphogypsum-red mud-based cementitious material include, by weight percentage: 45% phosphogypsum, 33% slag, 20% red mud, and 2% quicklime.

[0109] The dosage of the composite water reducer is 1.0ωt% of the dosage of the cementitious material, and the water-cement ratio is 0.30.

[0110] Comparative Example 1

[0111] Comparative Example 1 selects the polycarboxylic acid water reducer of model ZY-HPWR-S with methacrylic acid as the main chain and unsaturated ethers as the side chains. The dosage is 0.1ωt% of the cementitious material, and the water-cement ratio is 0.35.

[0112] The raw materials of the cementitious material include, by weight percentage: 45% phosphogypsum, 33% slag, 20% red mud, and 2% quicklime.

[0113] Comparative Example 2

[0114] Comparative Example 2 selects a composite water reducer obtained by compounding the polycarboxylic acid water reducer of model ZY-HPWR-S with methacrylic acid as the main chain and unsaturated ethers as the side chains and hydroxyethylidene diphosphonic acid. The dosages are 0.1ωt% and 0.05ωt% of the cementitious material respectively, and the water-cement ratio is 0.35.

[0115] The raw materials of the phosphogypsum-red mud-based cementitious material include, by weight percentage: 45% phosphogypsum, 33% slag, 20% red mud, and 2% quicklime.

[0116] Comparative Example 3

[0117] The composite water reducer used in Comparative Example 3 was obtained by compounding a polycarboxylate water reducer of model ZY-HPWR-S with unsaturated ethers as side chains, polyethylene glycol, and triethanolamine, and the dosages were 0.1ωt%, 0.085ωt%, and 0.08ωt% of the cementitious material respectively, and the water-cement ratio was 0.35.

[0118] The raw materials of the phosphogypsum-red mud based cementitious material include, by weight percentage: 45% phosphogypsum, 33% slag, 20% red mud, and 2% quicklime.

[0119] The property comparison table of the examples and comparative examples is as follows:

[0120]

[0121] It can be seen from the data in the above table that compared with the existing water reducers used in Comparative Examples 1-3, when the phosphogypsum-red mud based cementitious system uses the composite water reducer prepared in the present invention, the water-cement ratio is lower, the fluidity is stronger, the setting time of the system is shorter, the early hydration rate is faster, and the 3d, 7d, and 28d strengths of the cementitious material are significantly improved.

Claims

1. A composite water reducing agent suitable for phosphogypsum-red mud-based cementitious materials, characterized in that: The components include, by weight percentage, 22%-27% of modified polycarboxylic acid water-reducing agent, 7%-12% of ion complexing agent, 6%-11% of alcoholamine compound, 7%-15% of alcohol compound, and the rest is solvent.

2. A composite water reducing agent suitable for phosphogypsum-red mud-based cementitious materials according to claim 1, characterized in that: The modified polycarboxylic acid water-reducing agent is prepared by reaction at 50-60° C., and the reaction time is 150-180 minutes.

3. A composite water reducing agent suitable for phosphogypsum-red mud-based cementitious materials according to claim 1, characterized in that: The modified polycarboxylic acid water-reducing agent comprises, by weight, 40-50 parts of methacrylic acid, 15-20 parts of methylene diphosphonic acid, 18-22 parts of sodium dimethylformamide propane sulfonate, 2-4 parts of a chain transfer agent, 8-10 parts of an oxidant, 1-2 parts of a reducing agent, 40-45 parts of a sodium hydroxide solution, 400-450 parts of a solution d, and 380-435 parts of water.

4. A composite water reducing agent suitable for phosphogypsum-red mud-based cementitious materials as claimed in claim 3, characterized in that: The solution d is obtained by mixing methyl allyl polyoxyethylene ether 2400 and ethylene glycol monoethylene polyethylene glycol ether 2400 in a mass ratio of 1:1, and the mass fraction of the sodium hydroxide solution is 30%.

5. A composite water reducing agent suitable for phosphogypsum-red mud-based cementitious materials as claimed in claim 3, characterized in that: The chain transfer agent includes at least one of mercaptopropionic acid and thioglycolic acid; the reducing agent is ascorbic acid, and the oxidizing agent is a mixture of hydrogen peroxide and ammonium persulfate in a mass ratio of 1:

5.

6. A composite water reducing agent suitable for phosphogypsum-red mud-based cementitious materials according to claim 1, characterized in that: The alcoholamine compound includes at least one of triethanolamine and triisopropanolamine, and the ion complexing agent is hydroxyethylidene diphosphonic acid.

7. A composite water reducing agent suitable for phosphogypsum-red mud-based cementitious materials according to claim 1, characterized in that: The alcohol compound includes at least one of polyethylene glycol and polyvinyl alcohol, and the solvent is water.

8. A composite water reducing agent suitable for phosphogypsum-red mud-based cementitious materials according to claim 1, characterized in that: The modified polycarboxylic acid water-reducing agent has a pH value of 6.5-7.5 and a solid content of 30-55%.

9. A composite water reducing agent suitable for phosphogypsum-red mud-based cementitious materials according to claim 1, characterized in that: The addition amount of the composite water reducing agent is 1.0-1.4% of the mass of the phosphogypsum-red mud based cementitious material.

10. A method for preparing the composite water reducing agent according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: adding the alcohol amine and alcohol compound into water and stirring them thoroughly to dissolve them to form a solution; S2: Take a modified polycarboxylate water-reducing agent and an ion complexing agent, add them into water in sequence and stir them thoroughly to form a solution; S3: The solutions obtained in steps S1 and S2 are mixed evenly to obtain a composite water reducing agent.

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