A special admixture for super-retarded concrete and preparation method thereof

Abstract

The present application relates to the technical field of concrete, and specifically discloses a special admixture for super-slow concrete and a preparation method thereof, a special admixture for super-slow concrete, which includes the following raw materials in parts by weight: 10-15 parts of modified phosphogypsum powder, 5-10 parts of sodium polyacrylate, 0.01-0.015 parts of hydroxypropyl methylcellulose, 0.5-1 parts of sodium gluconate, 1-3 parts of sodium tripolyphosphate and 6-10 parts of aminosulfonate high-efficiency water reducer; the modified phosphogypsum powder is obtained by modification of ultra-fine basalt powder. The super-slow concrete obtained in this application has a maximum compressive strength of 53.5MPa and 88.2MPa at 7d and 28d, respectively, and a setting time of up to 71h, which prolongs the setting time of concrete while ensuring the strength of concrete.

Description

Technical Field

[0001] The present application relates to the field of concrete admixtures, and more specifically, to a special admixture for ultra-retarded concrete and a preparation method thereof. Background Art

[0002] Concrete refers to an engineering composite material that is made of aggregates bonded together by gel materials. It is a non-homogeneous porous material that is made by mixing cement as gel material, sand and gravel as aggregates with water in a certain proportion, stirring evenly, compacting, curing and hardening. In some large-scale projects, the volume of concrete required to be poured is large and the pouring time is long. Especially in the hot summer, the initial setting time of concrete must be greatly extended to ensure a successful pouring.

[0003] In the related art, in order to achieve a retarding effect, lignin sulfonate retarders are added to concrete. Due to the nature of introducing air, the early strength of concrete is low and hardening is poor, resulting in reduced strength and a short retarding time, which is difficult to meet the requirements of projects with a long pouring time. Summary of the invention

[0004] In order to prolong the setting time of concrete while ensuring the strength of concrete, the present application provides a special admixture for super-slow concrete and a preparation method thereof.

[0005] In the first aspect, the present application provides a special admixture for ultra-retarded concrete, which adopts the following technical solution:

[0006] A special admixture for super-retarded concrete comprises the following raw materials in parts by weight: 10-15 parts of modified phosphogypsum powder, 5-10 parts of sodium polyacrylate, 0.01-0.015 parts of hydroxypropyl methylcellulose, 0.5-1 parts of sodium gluconate, 1-3 parts of sodium tripolyphosphate and 6-10 parts of aminosulfonate high-efficiency water reducing agent; the modified phosphogypsum powder is obtained by modifying ultrafine basalt powder.

[0007] The present application provides a special admixture for super-retarded concrete, and the raw materials can be selected from 10-15 parts of modified phosphogypsum powder, 5-10 parts of sodium polyacrylate, 0.01-0.015 parts of hydroxypropyl methylcellulose, 0.5-1 parts of sodium gluconate, 1-3 parts of sodium tripolyphosphate and 6-10 parts of aminosulfonate high-efficiency water reducer. Any value within the respective ranges can be selected, and the setting time of concrete can be prolonged. When the modified phosphogypsum powder is 13 parts, the sodium polyacrylate is 8 parts, the hydroxypropyl methylcellulose is 0.013 parts, the sodium gluconate is 0.8 parts, the sodium tripolyphosphate is 2 parts and the aminosulfonate high-efficiency water reducer is 8 parts, the effect is best.

[0008] By adopting the above technical scheme, modified phosphogypsum powder is obtained by modifying ultrafine basalt powder, and the soluble impurities in the phosphogypsum powder are neutralized and converted into insoluble calcium phosphate, and harmful soluble phosphorus, fluorine and organic matter are eliminated, thereby reducing the impact of impurities, reducing the harm to cement performance, extending the setting time, and improving cement strength.

[0009] Sodium polyacrylate can significantly improve the anti-dispersion performance. It is easy to hydrolyze phosphate in aqueous solution, which can combine with calcium ions produced during cement hydration to form soluble complexes, reduce the number of free calcium and magnesium ions, hinder the formation rate of cement hydration products tricalcium silicate and dicalcium silicate, and prolong the cement hydration process. Hydroxypropyl methylcellulose can improve the phenomena of super slow setting concrete bleeding and poor workability, and further improve the slow setting performance of concrete.

[0010] Sodium gluconate can form complex salts with calcium ions in the system, reduce calcium ion concentration, inhibit tricalcium silicate hydration, prolong cement hydration induction period and play a coagulation role. In addition, there are a large number of hydroxyl groups in the molecular structure of sodium gluconate, some of which can be adsorbed on the surface of cement particles through hydrogen bonds, and other hydroxyl groups can associate with water molecules to form a stable solvated water film on the surface of cement particles, thereby inhibiting the hydration process of cement. Sodium tripolyphosphate can form complex salts with calcium ions in the system, reduce calcium ion concentration, hinder the crystallization and precipitation of calcium hydroxide, and the complex is adsorbed on the surface of cement particles, inhibiting cement hydration, and has a strong retarding effect. The mixed addition of sodium tripolyphosphate and sodium gluconate can further improve the retarding effect of concrete.

[0011] The amino group in the aminosulfonate high-efficiency water-reducing agent molecule contains lone pair electrons that can chelate calcium ions, reducing the calcium ion concentration and having a certain retarding effect. On the other hand, it has an adsorption and dispersion effect, which increases the amount of free water that is not adsorbed or flocculated in the cement paste and prolongs the setting time of the cement.

[0012] Preferably: a special admixture for super-retarded concrete comprises the following raw materials in parts by weight: 12-14 parts of modified phosphogypsum powder, 7-9 parts of sodium polyacrylate, 0.012-0.014 parts of hydroxypropyl methylcellulose, 0.7-0.9 parts of sodium gluconate, 1.5-2.5 parts of sodium tripolyphosphate and 7-9 parts of aminosulfonate high-efficiency water reducer.

[0013] The present application discloses a special admixture for super-retarded concrete, wherein the raw materials include 12-14 parts of modified phosphogypsum powder, 7-9 parts of sodium polyacrylate, 0.012-0.014 parts of hydroxypropyl methylcellulose, 0.7-0.9 parts of sodium gluconate, 1.5-2.5 parts of sodium tripolyphosphate and 7-9 parts of aminosulfonate high-efficiency water reducing agent. Any value within the respective ranges can be selected, and the setting time of concrete can be prolonged.

[0014] Preferably, the modified phosphogypsum powder is prepared by the following steps:

[0015] Mix the phosphogypsum powder and the ultrafine basalt powder, stir evenly, add water equal to the total mass of the phosphogypsum powder and the ultrafine basalt powder, add 5-10% of the mass of the phosphogypsum powder in steel slag, stir evenly, and obtain a mixture A;

[0016] The mixture A is heat-insulated and autoclaved at 140-150°C and 0.3-0.5MPa for 3-5h, cooled, dried and crushed to obtain modified phosphogypsum powder.

[0017] By adopting the above technical solution, the soluble impurities in the phosphogypsum powder are neutralized and converted into insoluble calcium phosphate, and harmful soluble phosphorus, fluorine and organic matter are eliminated, the impact of impurities is reduced, the harm to cement performance is reduced, the setting time is extended, and the strength of cement is improved. Adding steel slag to the modified phosphogypsum powder can greatly reduce the impact of impurities in the phosphogypsum powder on cement performance and improve the strength of the modified phosphogypsum powder.

[0018] Preferably, the mass ratio of the phosphogypsum powder to the ultrafine basalt powder is 1:(3-3.5).

[0019] By adopting the above technical solution and adjusting the mass ratio of phosphogypsum powder to ultrafine basalt powder, the modification effect of ultrafine basalt powder on phosphogypsum powder can be improved.

[0020] Preferably, the weight ratio of the sodium gluconate to sodium tripolyphosphate is 1:(2-5).

[0021] By adopting the above technical solution and adjusting the weight ratio of sodium gluconate to sodium tripolyphosphate, the retarding effect of concrete can be further improved.

[0022] Preferably, the special admixture for ultra-retarded concrete further comprises the following raw materials in parts by weight: 0.06-0.1 parts of molasses solution; the volume ratio of molasses to water in the molasses solution is 1:(0.5-1.5).

[0023] By adopting the above technical solution and adding molasses solution, the setting time of cement can be stabilized and the strength of cement can be improved.

[0024] Preferably, the weight ratio of the molasses to the modified phosphogypsum powder is 1:(150-200).

[0025] By adopting the above technical solution and adjusting the weight ratio of molasses to modified phosphogypsum powder, the setting time of cement can be further prolonged.

[0026] In the second aspect, the present application provides a method for preparing a special admixture for super-retarded concrete, which is specifically achieved through the following technical solutions:

[0027] A special admixture for super-retarded concrete, comprising the following operating steps:

[0028] The raw materials are mixed and stirred evenly to obtain a special admixture for super-retarded concrete.

[0029] In summary, the present application includes at least one of the following beneficial technical effects:

[0030] (1) This application controls the types and dosages of the raw materials of the special admixture for super-retarded concrete, so that the compressive strength of the super-retarded concrete at 7d and 28d is 47.3MPa and 82.1MPa respectively, and the setting time is 62-63h, thereby extending the setting time of the concrete while ensuring the strength of the concrete.

[0031] (2) The present application makes the setting time of the ultra-slow concrete 67h by adjusting the mass ratio of phosphogypsum powder to ultra-fine basalt powder and the amount of steel slag added in the modified phosphogypsum powder, thereby further extending the setting time of the concrete.

[0032] (3) The present application adds molasses to the raw materials of the special admixture for super-slow concrete and adjusts the weight ratio of molasses to modified phosphogypsum powder, so that the setting time of the super-slow concrete can be as long as 71 hours, thereby further extending the setting time of the concrete. DETAILED DESCRIPTION

[0033] The present application is further described in detail below in conjunction with specific embodiments.

[0034] The following raw materials in this application are all commercially available products, and are intended to make the raw materials of this application fully disclosed, and should not be understood as limiting the source of the raw materials. Specifically: sodium polyacrylate, effective substance content of 99.9%; hydroxypropyl methylcellulose, viscosity 200,000; sodium gluconate, effective substance content of 99%; sodium tripolyphosphate, effective substance content of 96%, particle size of 100; aminosulfonate high-efficiency water reducer, effective substance content of 99%; phosphogypsum powder, effective substance content of 90%; ultrafine basalt powder, particle size of 1250 mu; steel slag powder, particle size of 325 mesh; molasses, effective substance content of 99%.

[0035] The following is an example of the preparation of modified phosphogypsum

[0036] Preparation Example 1

[0037] The modified phosphogypsum of Preparation Example 1 is prepared by the following steps:

[0038] 10 kg of phosphogypsum powder and 28 kg of ultrafine basalt powder were mixed and stirred evenly, 38 L of water was added, 0.5 kg of steel slag powder was added and stirred evenly to obtain a mixture A;

[0039] The mixture A was steam-pressed at 145°C and 0.4 MPa for 4 h, cooled, dried and crushed to obtain modified phosphogypsum powder.

[0040] Preparation Example 2-5

[0041] The modified phosphogypsum of Preparation Examples 2-5 is prepared in the same manner as that of Preparation Example 1, except that the dosage of ultrafine basalt powder is 30kg, 32kg, 35kg and 38kg, and the remaining operations are the same as those of Preparation Example 1.

[0042] Preparation Example 6-7

[0043] The modified phosphogypsum of Preparation Examples 6-7 is prepared in the same manner as that of Preparation Example 1, except that the amount of steel slag powder added is 0.8 kg and 1 kg, and the rest of the operations are the same as those of Preparation Example 1.

[0044] Example 1

[0045] A special admixture for super-retarded concrete is prepared by the following steps:

[0046] According to the dosage in Table 1, the raw materials are mixed and stirred evenly to obtain a special admixture for super-retarded concrete.

[0047] Example 2-3

[0048] The preparation method and raw material types of the special admixture for ultra-retarded concrete of Example 2-3 are exactly the same as those of Example 1, except that the dosage of each raw material is different, as shown in Table 1 for details.

[0049] Table 1 The dosage of each raw material of the special admixture for ultra-retarded concrete of Examples 1-3 (unit: kg)

[0050] raw material Example 1 Example 2 Example 3 Modified phosphogypsum powder 10 13 15 Sodium polyacrylate 8 8 8 Hydroxypropyl methylcellulose 0.03 0.03 0.03 Sodium Gluconate 1 1 1 Sodium tripolyphosphate 1 1 1 Aminosulfonate high efficiency water reducer 8 8 8

[0051] Embodiment 4-8

[0052] The preparation methods and raw material types of the special admixtures for ultra-retarded concrete of Examples 4-8 are exactly the same as those of Example 2, except that the dosage of each raw material is different, as shown in Table 2 for details.

[0053] Table 2 The dosage of each raw material of the special admixture for ultra-retarded concrete of Examples 4-8 (unit: kg)

[0054]

[0055]

[0056] Examples 9-14

[0057] The preparation methods of the special admixtures for ultra-retarded concrete of Examples 9-14 are the same as those of Example 6, except that the modified phosphogypsum powder is the phosphogypsum powder prepared in Preparation Examples 2-7, respectively, and the types and dosages of other raw materials are the same as those of Example 6.

[0058] Examples 15-19

[0059] The preparation methods and raw material types of the special admixtures for ultra-retarded concrete of Examples 15-19 are exactly the same as those of Example 13, except that molasses solution is added to the raw materials, and the volume ratio of molasses to water in the molasses solution is 1:1, as shown in Table 3 for details.

[0060] Table 3 The dosage of each raw material of the special admixture for ultra-retarded concrete of Examples 15-19 (unit: kg)

[0061] raw material Embodiment 15 Example 16 Embodiment 17 Embodiment 18 Embodiment 19 Modified phosphogypsum powder 10 12 14.4 12 15 Sodium polyacrylate 8 8 8 8 8 Hydroxypropyl methylcellulose 0.03 0.03 0.03 0.03 0.03 Sodium Gluconate 0.5 0.5 0.5 0.5 0.5 Sodium tripolyphosphate 1.75 1.75 1.75 1.75 1.75 Aminosulfonate high efficiency water reducer 8 8 8 8 8 molasses solution 0.1 0.08 0.08 0.06 0.06

[0062] Comparative Example 1

[0063] The preparation method of the special admixture for super-retarded concrete in Comparative Example 1 is exactly the same as that in Example 1, except that: modified phosphogypsum powder is not added to the raw materials of the special admixture for super-retarded concrete, and the other raw materials and dosages are the same as those in Example 1.

[0064] Comparative Example 2

[0065] The preparation method of the special admixture for ultra-retarded concrete in Comparative Example 2 is exactly the same as that in Example 1, except that an equal amount of modified phosphogypsum powder in the raw materials of the special admixture for ultra-retarded concrete is replaced by phosphogypsum powder, and the remaining raw materials and dosages are the same as those in Example 1.

[0066] Comparative Example 3

[0067] The preparation method of the special admixture for ultra-retarded concrete of Comparative Example 3 is exactly the same as that of Example 1, except that an equal amount of sodium gluconate in the raw materials of the special admixture for ultra-retarded concrete is replaced by sodium tripolyphosphate, and the remaining raw materials and dosages are the same as those of Example 1.

[0068] Comparative Example 4

[0069] The preparation method of the special admixture for ultra-retarded concrete of Comparative Example 4 is exactly the same as that of Example 1, except that an equal amount of sodium tripolyphosphate in the raw materials of the special admixture for ultra-retarded concrete is replaced by sodium gluconate, and the remaining raw materials and dosages are the same as those of Example 1.

[0070] Comparative Example 5

[0071] The preparation method of the special admixture for super-retarded concrete in Comparative Example 5 is exactly the same as that in Example 1, except that an equal amount of aminosulfonate high-efficiency water-reducing agent in the raw materials of the special admixture for super-retarded concrete is replaced by polycarboxylic acid high-efficiency water-reducing agent, and the remaining raw materials and dosages are the same as those in Example 1.

[0072] Comparative Example 6

[0073] The preparation method of the special admixture for super-retarded concrete in Comparative Example 6 is exactly the same as that in Example 1, except that hydroxypropyl methylcellulose is not added to the raw materials of the special admixture for super-retarded concrete, and the remaining raw materials and dosages are the same as those in Example 1.

[0074] Comparative Example 7

[0075] The preparation method of the special admixture for super-retarded concrete in Comparative Example 7 is exactly the same as that in Example 1, except that sodium polyacrylate is not added to the raw materials of the special admixture for super-retarded concrete, and the remaining raw materials and dosages are the same as those in Example 1.

[0076] The following is the application of special admixtures for super-retarded concrete in concrete

[0077] Application Example 1

[0078] Application Example 1 The application method of the special admixture for super-retarded concrete in concrete is as follows: apply the special admixture for super-retarded concrete obtained in Example 1 to concrete. The concrete includes the following raw materials: 336kg of silicate cement, 74kg of fly ash, 51kg of mineral powder, 450kg of artificial sand, 450kg of natural sand, 939kg of crushed stone and 50.1kg of special admixture for slow concrete. Among them, the cement is PO 42.5 cement; the fly ash is F class II fly ash; the mineral powder has a particle size of 325 mesh; the natural sand has a machine-made sand fineness modulus of 2.8; the crushed stone has a continuous graded crushed stone of 5 to 25 mm.

[0079] Application Example 2-19

[0080] The application method of the special admixture for super-retarded concrete of Application Examples 12-19 is the same as that of Application Example 1, except that: the special admixture for super-retarded concrete is the special admixture for super-retarded concrete obtained in Examples 2-19, and the rest of the operations are the same as those of Application Example 1.

[0081] Performance test (I)

[0082] The following testing standards or methods were used to test the basic performance of the ultra-slow concrete obtained from different application examples 1-19 and application comparison examples 1-7. The test results are detailed in Table 4.

[0083] Setting time: Record the setting time of concrete in accordance with GB / T50080-2016 "Standard for Test Methods for Performance of Ordinary Concrete Mixtures".

[0084] Compressive strength: The compressive strength of concrete at 7d and 28d is tested in accordance with GB / T50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete".

[0085] Number of cracks: The number of cracks per square meter is measured 24 hours after concrete pouring in accordance with GB / T50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete".

[0086] Table 4 Performance test results of different super-retarded concrete

[0087]

[0088]

[0089] The test results in Table 4 show that the compressive strength of the super-slow concrete obtained in the present application at 7d and 28d is 53.5MPa and 88.2MPa respectively, which has a high compressive strength, and the number of cracks per unit area is as low as 3.4, which has a high crack resistance; at the same time, the setting time of the super-slow concrete obtained in the present application can be up to 71h, which prolongs the setting time of the concrete while ensuring the strength of the concrete.

[0090] In Application Examples 1-3, the compressive strength of the ultra-retarded concrete in Application Example 2 at 7d and 28d is 45.1MPa and 79.2MPa respectively, and the setting time of the ultra-retarded concrete is 60h, which is longer than that in Application Examples 1 and 3, indicating that the modified phosphogypsum content in the raw material of the special admixture for ultra-retarded concrete in Application Example 2 is more appropriate, which prolongs the setting time of the concrete. It may be that the modified phosphogypsum powder is obtained by modifying the ultra-fine basalt powder, and the soluble impurities in the phosphogypsum powder are neutralized and converted into insoluble calcium phosphate, and harmful soluble phosphorus, fluorine and organic matter are eliminated, the influence of impurities is reduced, the harm to cement performance is reduced, the setting time is prolonged, and the cement strength is improved.

[0091] In Application Examples 4-8, the setting time of the super-retarded concrete of Application Examples 5-7 is 62-63h, which is longer than that of Application Examples 4 and 8, indicating that when the weight ratio of sodium gluconate to sodium tripolyphosphate in the special admixture for super-retarded concrete is 1:(2-5), the setting time of the concrete is prolonged. This may be related to adjusting the weight ratio of sodium gluconate to sodium tripolyphosphate to further improve the retarding effect of the concrete.

[0092] In application examples 9-12, the compressive strength of the super-retarded concrete of application examples 9-11 at 7d and 28d was 48.2-49.3MPa and 83.3-84.2MPa, respectively, which was higher than that of application example 12, and the setting time of the super-retarded concrete was 65-66h, which was longer than that of application example 12, indicating that when the mass ratio of phosphogypsum powder to ultrafine basalt powder in the modified phosphogypsum powder was 1:(3-3.5), the setting time of the concrete was prolonged and the strength of the concrete was guaranteed. This may be related to the fact that adjusting the mass ratio of phosphogypsum powder to ultrafine basalt powder can improve the modification effect of ultrafine basalt powder on phosphogypsum powder.

[0093] Combining the performance test data of the super-retarded concrete of Application Example 10 and Application Examples 13-14, it is found that the setting time of the super-retarded concrete of Application Example 13 is 67h, which is longer than that of Application Examples 10 and 14, indicating that the amount of steel slag in the modified phosphogypsum powder of Application Example 13 is more appropriate, which prolongs the setting time of the concrete. This may be related to the fact that adjusting the amount of steel slag can greatly reduce the impact of impurities in the phosphogypsum powder on cement performance and improve the strength of the modified phosphogypsum powder.

[0094] In Application Examples 15-19, the setting time of the super-retarded concrete of Application Examples 16-18 is 70-71h, which is longer than that of Application Examples 15 and 19, indicating that when the weight ratio of molasses to modified phosphogypsum powder in the special admixture for super-retarded concrete is 1: (150-200), the setting time of the concrete is prolonged. This may be related to adjusting the weight ratio of molasses to modified phosphogypsum powder to further prolong the setting time of the concrete.

[0095] Combining the performance test data of the super-slow concrete of application examples 1-7 and application example 1, it was found that adding modified phosphogypsum, sodium gluconate, sodium tripolyphosphate, aminosulfonate high-efficiency water reducer, hydroxypropyl methylcellulose and sodium polyacrylate to the special admixture raw materials for super-slow concrete prolonged the setting time of concrete and could meet the needs of projects with longer pouring time.

[0096] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A special admixture for super slow concrete, characterized in that: The method comprises the following raw materials in parts by weight: 10-15 parts of modified phosphogypsum powder, 5-10 parts of sodium polyacrylate, 0.01-0.015 parts of hydroxypropyl methylcellulose, 0.5-1 parts of sodium gluconate, 1-3 parts of sodium tripolyphosphate and 6-10 parts of aminosulfonate high-efficiency water reducing agent; The modified phosphogypsum powder is obtained by modifying ultrafine basalt powder; the modified phosphogypsum powder is prepared by the following steps: 10 kg of phosphogypsum powder and ultrafine basalt powder were mixed and stirred evenly, 38 L of water was added, and 5-10% of the weight of the phosphogypsum powder was added with steel slag powder, and stirred evenly to obtain a mixture A; The mixture A is heat-insulated and autoclaved at 140-150° C. and 0.3-0.5 MPa for 3-5 hours, cooled, dried and crushed to obtain modified phosphogypsum powder; The mass ratio of the phosphogypsum powder to the ultrafine basalt powder is 1:(3-3.5); The weight ratio of the sodium gluconate to sodium tripolyphosphate is 1:(2-5).

2. The special admixture for ultra-slow concrete according to claim 1, characterized in that: The invention comprises the following raw materials in parts by weight: 12-14 parts of modified phosphogypsum powder, 7-9 parts of sodium polyacrylate, 0.012-0.014 parts of hydroxypropyl methylcellulose, 0.7-0.9 parts of sodium gluconate, 1.5-2.5 parts of sodium tripolyphosphate and 7-9 parts of aminosulfonate high-efficiency water reducing agent.

3. The special admixture for ultra-slow concrete according to claim 1, characterized in that: The special admixture for super-retarded concrete also includes the following raw materials in parts by weight: 0.06-0.1 parts of molasses solution; the volume ratio of molasses to water in the molasses solution is 1: (0.5-1.5).

4. The special admixture for ultra-slow concrete according to claim 3, characterized in that: The weight ratio of the molasses solution to the modified phosphogypsum powder is 1:(150-200).

5. A method for preparing the special admixture for ultra-retarded concrete according to any one of claims 1 to 4, characterized in that: The steps include: The raw materials are mixed and stirred evenly to obtain a special admixture for super-retarded concrete.

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