CN116444193A - Special additive for ultra-slow concrete and preparation method thereof - Google Patents

Abstract

The application relates to the technical field of concrete, and in particular discloses an admixture special for ultra-slow concrete and a preparation method thereof, wherein the admixture special for ultra-slow 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 part of hydroxypropyl methyl cellulose, 0.5-1 part of sodium gluconate, 1-3 parts of sodium tripolyphosphate and 6-10 parts of sulfamate high-efficiency water reducer; the modified phosphogypsum powder is obtained by modifying superfine basalt powder. The compressive strength of the ultra-slow concrete 7d and the compressive strength of the ultra-slow concrete 28d obtained by the method are 53.5MPa and 88.2MPa respectively, the maximum setting time can reach 71h, and the setting time of the concrete is prolonged while the strength of the concrete is ensured.

Description

Special additive for ultra-slow concrete and preparation method thereof

Technical Field

The application relates to the field of concrete additives, in particular to an additive special for ultra-slow concrete and a preparation method thereof.

Background

The concrete is an engineering composite material formed by cementing aggregate into a whole by using a gel material, and is a non-homogeneous porous material formed by uniformly stirring, compacting, shaping, curing and hardening cement serving as the gel material and sand serving as the aggregate and water according to a certain proportion. In some large projects, the amount of concrete to be poured is large, the pouring time is long, and especially in hot summer, the initial setting time of the concrete must be greatly prolonged to ensure that one pouring is successful.

In the related art, in order to achieve the retarding effect, lignin sulfonate retarder is added into concrete, and due to the property of introducing air, the early strength of the concrete is lower, the hardening is poor, the strength is reduced, the retarding time is shorter, and the project with longer pouring time is difficult to meet.

Disclosure of Invention

In order to prolong the setting time of concrete under the condition of ensuring the strength of the concrete, the application provides an additive special for ultra-slow concrete and a preparation method thereof.

In a first aspect, the present application provides an admixture for ultra-slow concrete, which adopts the following technical scheme:

an additive special for ultra-slow 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 part of hydroxypropyl methyl cellulose, 0.5-1 part of sodium gluconate, 1-3 parts of sodium tripolyphosphate and 6-10 parts of sulfamate high-efficiency water reducer; the modified phosphogypsum powder is obtained by modifying superfine basalt powder.

The special additive for ultra-slow concrete has the advantages that the raw materials of the special additive can be 10-15 parts of modified phosphogypsum powder, 5-10 parts of sodium polyacrylate, 0.01-0.015 part of hydroxypropyl methyl cellulose, 0.5-1 part of sodium gluconate, 1-3 parts of sodium tripolyphosphate and 6-10 parts of sulfamate high-efficiency water reducer, any value in each range can be selected, the setting time of concrete can be prolonged, and when 13 parts of modified phosphogypsum powder, 8 parts of sodium polyacrylate, 0.013 part of hydroxypropyl methyl cellulose, 0.8 part of sodium gluconate, 2 parts of sodium tripolyphosphate and 8 parts of sulfamate high-efficiency water reducer are used, the effect is optimal.

By adopting the technical scheme, the modified phosphogypsum powder is obtained by modifying the superfine basalt powder, soluble impurities of the phosphogypsum powder are subjected to neutralization reaction and converted into indissolvable calcium phosphate, harmful soluble phosphorus, fluorine and organic matters are eliminated, the influence of the impurities is reduced, the harm to cement performance is reduced, the setting time is prolonged, and the cement strength is improved.

Sodium polyacrylate can significantly improve the anti-discrete performance. Phosphate is easy to hydrolyze in aqueous solution, and can be combined with calcium ions generated in the cement hydration process to generate soluble complex, so that the quantity of free movable calcium and magnesium ions is reduced, the generation rate of tricalcium silicate and dicalcium silicate serving as cement hydration products is hindered, and the cement hydration process is prolonged. The hydroxypropyl methyl cellulose can improve the phenomena of bleeding, poor workability and the like of the super-retarding concrete, and further improve the retarding performance of the concrete.

Sodium gluconate can form complex salt with calcium ions in a system, so that the concentration of calcium ions is reduced, the hydration of tricalcium silicate is inhibited, the cement hydration induction period is prolonged, and the coagulation effect is achieved. The sodium tripolyphosphate can form complex salt with calcium ions in the system, so that the concentration of the calcium ions is reduced, crystallization precipitation of calcium hydroxide is prevented, the complex is adsorbed on the surfaces of cement particles, cement hydration is inhibited, and the retarder has a strong retarding effect. The sodium tripolyphosphate and the sodium gluconate are mixed and added, so that the retarding effect of the concrete can be further improved.

The amino group in the sulfamate high-efficiency water reducing agent molecule contains lone pair electrons to chelate calcium ions, so that the concentration of the calcium ions is reduced, and the sulfamate high-efficiency water reducing agent has a certain retarding effect, and on the other hand, has the adsorption and dispersion effects, so that free water which is not adsorbed or flocculated in the cement paste is increased, and the setting time of the cement is prolonged.

As preferable: an additive special for ultra-slow 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 part of hydroxypropyl methyl cellulose, 0.7-0.9 part of sodium gluconate, 1.5-2.5 parts of sodium tripolyphosphate and 7-9 parts of sulfamate high-efficiency water reducer.

The special additive for ultra-slow concrete is prepared from 12-14 parts of modified phosphogypsum powder, 7-9 parts of sodium polyacrylate, 0.012-0.014 part of hydroxypropyl methyl cellulose, 0.7-0.9 part of sodium gluconate, 1.5-2.5 parts of sodium tripolyphosphate and 7-9 parts of sulfamate high-efficiency water reducer, and can be any value in each range, and the setting time of concrete can be prolonged.

As preferable: the modified phosphogypsum powder is prepared by the following steps:

mixing phosphogypsum powder and superfine basalt powder, stirring uniformly, adding water with the total mass of the phosphogypsum powder and the superfine basalt powder, adding steel slag with the mass of 5-10% of that of the phosphogypsum powder, and stirring uniformly to obtain a mixture A;

and (3) carrying out heat preservation and autoclaved on the mixture A for 3-5 hours at 140-150 ℃ and 0.3-0.5MPa, cooling, drying and crushing to obtain the modified phosphogypsum powder.

By adopting the technical scheme, the phosphogypsum powder soluble impurities are subjected to neutralization reaction and are converted into indissolvable calcium phosphate, harmful soluble phosphorus, fluorine and organic matters are eliminated, the influence of the impurities is reduced, the harm to cement performance is reduced, the setting time is prolonged, and the cement strength is improved. The steel slag is added into the modified phosphogypsum powder, so that the influence of impurities in the phosphogypsum powder on the cement performance can be greatly reduced, and the strength of the modified phosphogypsum powder is improved.

As preferable: the mass ratio of phosphogypsum powder to superfine basalt powder is 1: (3-3.5).

By adopting the technical scheme, the quality ratio of phosphogypsum powder to superfine basalt powder is adjusted, so that the modification effect of the superfine basalt powder on phosphogypsum powder can be improved.

As preferable: the weight ratio of the sodium gluconate to the sodium tripolyphosphate is 1: (2-5).

By adopting the technical scheme, the proportion of the sodium gluconate to the sodium tripolyphosphate in parts by weight is adjusted, so that the retarding effect of the concrete is further improved.

As preferable: the special additive for ultra-slow concrete further comprises the following raw materials in parts by weight: 0.06-0.1 part of molasses solution; the volume ratio of molasses to water in the molasses solution is 1: (0.5-1.5).

By adopting the technical scheme, the molasses solution is added, so that the setting time of the cement can be stabilized, and the strength of the cement can be improved.

As preferable: the weight ratio of molasses to modified phosphogypsum powder is 1: (150-200).

By adopting the technical scheme, the weight part ratio of molasses and modified phosphogypsum powder is adjusted, so that the setting time of cement is further prolonged.

In a second aspect, the present application provides a preparation method of an admixture special for ultra-slow concrete, which is specifically implemented by the following technical scheme:

an admixture special for ultra-slow concrete, which comprises the following operation steps:

and mixing the raw materials, and uniformly stirring to obtain the special additive for ultra-slow concrete.

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

(1) The compressive strength of the ultra-slow concrete 7d and the compressive strength of the ultra-slow concrete 28d are respectively 47.3MPa and 82.1MPa by controlling the types and the mixing amounts of the raw materials of the additive special for the ultra-slow concrete, the setting time is 62-63h, and the setting time of the concrete is prolonged while the strength of the concrete is ensured.

(2) According to the method, the setting time of the ultra-slow concrete is 67h through the mass ratio of phosphogypsum powder to superfine basalt powder in the modified phosphogypsum powder and the mixing amount of steel slag, and the setting time of the concrete is further prolonged.

(3) The molasses is added into the special additive raw material for the ultra-slow concrete, and the weight part ratio of the molasses and the modified phosphogypsum powder is adjusted, so that the setting time of the ultra-slow concrete can reach 71 hours at the longest, and the setting time of the concrete is further prolonged.

Detailed Description

The present application is described in further detail below in connection with specific examples.

The following raw materials are all commercial products, and are fully disclosed in the present application, and should not be construed as limiting the sources of the raw materials. The method comprises the following steps: sodium polyacrylate, the content of active substances is 99.9%; hydroxypropyl methylcellulose, viscosity 20 ten thousand; sodium gluconate with 99% active substance content; sodium tripolyphosphate with 96% active matter content and 100 particle size; sulfamate high-efficiency water reducer with the content of effective substances of 99 percent; phosphogypsum powder with the content of effective substances of 90 percent; superfine basalt powder with the particle size of 1250 mu; steel slag powder with particle size of 325 meshes; molasses, the active substance content is 99%.

The following is a preparation example of modified phosphogypsum

Preparation example 1

The modified phosphogypsum of the preparation example 1 is prepared by the following operation steps:

mixing 10kg of phosphogypsum powder and 28kg of ultrafine basalt powder, uniformly stirring, adding 38L of water, adding 0.5kg of steel slag powder, and uniformly stirring to obtain a mixture A;

and (3) carrying out heat preservation and autoclaved on the mixture A at 145 ℃ and 0.4MPa for 4 hours, cooling, drying and crushing to obtain the modified phosphogypsum powder.

PREPARATION EXAMPLES 2 to 5

The modified phosphogypsum of preparation examples 2 to 5 was the same as the preparation method of preparation example 1, except that the blending amount of the ultrafine basalt powder was 30kg, 32kg, 35kg and 38kg, and the rest was the same as preparation example 1.

Preparation examples 6 to 7

The modified phosphogypsum of preparation examples 6 to 7 was the same as the preparation method of preparation example 1, except that the mixing amount of the slag powder was 0.8kg and 1kg, and the rest of the operations were the same as preparation example 1.

Example 1

The special additive for the ultra-slow concrete is prepared by the following operation steps:

according to the mixing amount of the table 1, the raw materials are mixed and stirred uniformly to obtain the admixture special for ultra-slow concrete.

Examples 2 to 3

The admixture for ultra-slow concrete of examples 2-3 was identical to the preparation method and the kind of raw materials of example 1, except that the blending amounts of the raw materials were different, and the details are shown in Table 1.

TABLE 1 amounts of raw materials (unit: kg) of the admixture for ultra-slow concrete of examples 1 to 3

Raw materials	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
Gluconic acid sodium salt	1	1	1
				Sodium tripolyphosphate	1	1	1
Sulfamate high-efficiency water reducer	8	8	8

Examples 4 to 8

The admixture for ultra-slow concrete of examples 4 to 8 was identical to the preparation method and the kind of the raw materials of example 2 except that the blending amounts of the raw materials were different, and the details are shown in Table 2.

TABLE 2 amounts of raw materials (unit: kg) of the admixture for ultra-slow concrete of examples 4 to 8

Examples 9 to 14

The ultra-slow concrete admixture of examples 9 to 14 was the same as the preparation method of example 6, except that phosphogypsum powder prepared in preparation examples 2 to 7 was used as the modified phosphogypsum powder, and the types and blending amounts of the remaining raw materials were the same as those of example 6.

Examples 15-19

The ultra-slow concrete special additive of examples 15-19 is identical to the preparation method of example 13 and the types of raw materials, except that a molasses solution is added into the raw materials, and the volume ratio of molasses to water in the molasses solution is 1:1, see table 3 for details.

TABLE 3 amounts of raw materials (unit: kg) of the admixture for ultra-slow concrete of examples 15 to 19

Raw materials	Example 15	Example 16	Example 17	Example 18	Example 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
Gluconic acid sodium salt	0.5	0.5	0.5	0.5	0.5
						Sodium tripolyphosphate	1.75	1.75	1.75	1.75	1.75
Sulfamate high-efficiency water reducer	8	8	8	8	8
						Molasses solution	0.1	0.08	0.08	0.06	0.06

Comparative example 1

The admixture for ultra-slow concrete of comparative example 1 was exactly the same as the preparation method of example 1, except that: the raw materials of the additive special for ultra-slow concrete are not added with modified phosphogypsum powder, and the rest raw materials and the mixing amount are the same as those of the example 1.

Comparative example 2

The admixture for ultra-slow concrete of comparative example 2 was exactly the same as the preparation method of example 1, except that: the modified phosphogypsum powder in the additive raw materials special for ultra-slow concrete is replaced by phosphogypsum powder in equal quantity, and the rest raw materials and the mixing amount are the same as those in the example 1.

Comparative example 3

The preparation method of the ultra-slow concrete special additive of the comparative example 3 is exactly the same as that of the example 1, except that: the sodium gluconate in the raw materials of the additive special for ultra-slow concrete is replaced by sodium tripolyphosphate in equal quantity, and the rest raw materials and the mixing quantity are the same as those in the example 1.

Comparative example 4

The ultra-slow concrete admixture of comparative example 4 was exactly the same as the preparation method of example 1, except that: sodium tripolyphosphate in the raw materials of the additive special for ultra-slow concrete is replaced by sodium gluconate in an equivalent amount, and the rest raw materials and the mixing amount are the same as those in the example 1.

Comparative example 5

The ultra-slow concrete admixture of comparative example 5 was exactly the same as the preparation method of example 1, except that: the sulfamate high-efficiency water reducer in the additive raw material special for ultra-slow concrete is replaced by the polycarboxylic acid high-efficiency water reducer in the same amount, and the rest raw materials and the mixing amount are the same as those in the example 1.

Comparative example 6

The ultra-slow concrete admixture of comparative example 6 was exactly the same as the preparation method of example 1, except that: hydroxypropyl methylcellulose is not added into the raw materials of the special additive for ultra-slow concrete, and the rest raw materials and the mixing amount are the same as those in the example 1.

Comparative example 7

The ultra-slow concrete admixture of comparative example 7 was exactly the same as the preparation method of example 1, except that: sodium polyacrylate is not added into the raw materials of the additive special for ultra-slow concrete, and the other raw materials and the mixing amount are the same as those in the example 1.

The following is the application of the admixture special for ultra-slow concrete in concrete

Application example 1

Application example 1 the application method of the admixture special for ultra-slow concrete in concrete is as follows: the ultra-slow concrete admixture obtained in example 1 was applied to concrete. The concrete comprises the following raw materials: 336kg of Portland cement, 74kg of fly ash, 51kg of mineral powder, 450kg of artificial sand, 450kg of natural sand, 939kg of broken stone and 50.1kg of special additive for mild concrete. Wherein, the cement is P.O 42.5.42.5 cement; the fly ash is class-F II fly ash; mineral powder with particle size of 325 meshes; natural sand, machine-made sand fineness modulus 2.8; crushed stone with 5-25 mm continuous graded crushed stone.

Application examples 2 to 19

The application method of the admixture special for ultra-slow concrete of application examples 12 to 19 is the same as application example 1, except that: the ultra-slow concrete special additive obtained in examples 2 to 19 was used, and the rest of the operations were the same as in application example 1.

Performance detection 1

The following detection criteria or methods were used to detect the basic properties of the ultra-slow concretes obtained in different application examples 1 to 19 and comparative examples 1 to 7, respectively, and the detection results are shown in Table 4.

Coagulation time: the setting time of the concrete is recorded according to GB/T50080-2016 Standard for Performance test of common concrete mixtures.

Compressive strength: the compressive strength of the concrete 7d and 28d was measured according to GB/T50081-2019 Standard of test method for physical mechanical Properties of concrete.

Number of cracks: the number of cracks per square meter measured after 24 hours of concrete pouring is detected according to GB/T50081-2019 Standard of test method for physical and mechanical Properties of concrete.

TABLE 4 Performance test results for different ultra-slow concretes

The test results in Table 4 show that the compressive strengths of the ultra-slow concrete 7d and 28d obtained by the method are 53.5MPa and 88.2MPa at the highest, the ultra-slow concrete has higher compressive strength, the number of cracks in unit area is 3.4 at the lowest, and the ultra-slow concrete has higher crack resistance; meanwhile, the setting time of the ultra-slow concrete obtained by the method can reach 71 hours at the longest, and the setting time of the concrete is prolonged while the strength of the concrete is ensured.

In application examples 1 to 3, the compressive strength of the ultra-slow concrete 7d and 28d of application example 2 is 45.1MPa and 79.2MPa respectively, and the setting time of the ultra-slow concrete is 60h, which is longer than that of application examples 1 and 3, which shows that the mixing amount of the modified phosphogypsum in the raw materials of the additive special for the ultra-slow concrete in application example 2 is proper, and the setting time of the concrete is prolonged. The modified phosphogypsum powder can be obtained by modifying the superfine basalt powder, soluble impurities of the phosphogypsum powder are subjected to neutralization reaction and converted into indissolvable calcium phosphate, harmful soluble phosphorus, fluorine and organic matters are eliminated, the influence of the impurities is reduced, the harm to cement performance is reduced, the setting time is prolonged, and the cement strength is improved.

In application examples 4 to 8, the setting time of the ultra-slow concrete of application examples 5 to 7 is 62 to 63 hours, which is longer than that of application examples 4 and 8, and the weight part ratio of sodium gluconate to sodium tripolyphosphate in the admixture special for the ultra-slow concrete is 1: and (2-5), the setting time of the concrete is prolonged. It may be related to adjusting the weight proportion of sodium gluconate and sodium tripolyphosphate to further improve the retarding effect of the concrete.

In application examples 9 to 12, the compressive strength of the ultra-slow concrete 7d and 28d of application examples 9 to 11 is respectively 48.2 to 49.3MPa and 83.3 to 84.2MPa, which are higher than that of application example 12, and the setting time of the ultra-slow concrete is 65 to 66 hours, which is longer than that of application example 12, which shows that when the mass ratio of phosphogypsum powder to superfine basalt powder in the modified phosphogypsum powder is 1: and (3-3.5), the setting time of the concrete is prolonged, and the strength of the concrete is ensured. The modification effect of the superfine basalt powder on the phosphogypsum powder can be improved possibly by adjusting the mass ratio of the phosphogypsum powder to the superfine basalt powder.

The combination of the performance detection data of the ultra-slow concrete of the application example 10 and the ultra-slow concrete of the application examples 13 and 13-14 shows that the setting time of the ultra-slow concrete of the application example 13 is 67h and longer than that of the application examples 10 and 14, so that the mixing amount of the steel slag in the modified phosphogypsum of the application example 13 is proper, and the setting time of the concrete is prolonged. The method can be related to adjusting the mixing amount of the steel slag, greatly reducing the influence of impurities in phosphogypsum on the cement performance and improving the strength of the modified phosphogypsum.

In application examples 15 to 19, the setting time of the ultra-slow concrete of application examples 16 to 18 is 70 to 71 hours, which is longer than that of application examples 15 and 19, and the weight part ratio of molasses and modified phosphogypsum in the admixture special for the ultra-slow concrete is 1: and (150-200), the setting time of the concrete is prolonged. It may be related to adjusting the weight part ratio of molasses and modified phosphogypsum powder, further prolonging the setting time of the concrete.

According to the combination of the performance detection data of the ultra-slow concrete of the application comparative examples 1-7 and the application example 1, modified phosphogypsum, sodium gluconate, sodium tripolyphosphate, sulfamate high-efficiency water reducer, hydroxypropyl methyl cellulose and sodium polyacrylate are added into the raw materials of the special additive for the ultra-slow concrete, so that the setting time of the concrete is prolonged, and the engineering with longer pouring time can be satisfied.

The present embodiment is merely illustrative of the present application and is not intended to be limiting, and those skilled in the art, after having read the present specification, may make modifications to the present embodiment without creative contribution as required, but is protected by patent laws within the scope of the claims of the present application.

Claims (8)

1. The special additive for the ultra-slow concrete is characterized by comprising 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 part of hydroxypropyl methyl cellulose, 0.5-1 part of sodium gluconate, 1-3 parts of sodium tripolyphosphate and 6-10 parts of sulfamate high-efficiency water reducer; the modified phosphogypsum powder is obtained by modifying superfine basalt powder.

2. The admixture for ultra-slow concrete according to claim 1, which is characterized by comprising 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 part of hydroxypropyl methyl cellulose, 0.7-0.9 part of sodium gluconate, 1.5-2.5 parts of sodium tripolyphosphate and 7-9 parts of sulfamate high-efficiency water reducer.

3. The admixture for ultra-slow concrete according to claim 1, wherein the modified phosphogypsum powder is prepared by the following steps:

mixing phosphogypsum powder and superfine basalt powder, uniformly stirring, adding water with the total mass of the phosphogypsum powder and the superfine basalt powder, adding steel slag powder with the mass of 5-10% of that of the phosphogypsum powder, and uniformly stirring to obtain a mixture A;

and (3) carrying out heat preservation and autoclaved on the mixture A for 3-5 hours at 140-150 ℃ and 0.3-0.5MPa, cooling, drying and crushing to obtain the modified phosphogypsum powder.

4. The admixture for ultra-slow concrete according to claim 3, wherein: the mass ratio of phosphogypsum powder to superfine basalt powder is 1: (3-3.5).

5. The admixture for ultra-slow concrete according to claim 1, wherein the weight ratio of the sodium gluconate to the sodium tripolyphosphate is 1: (2-5).

6. The admixture for ultra-slow concrete according to claim 1, wherein: the special additive for ultra-slow concrete further comprises the following raw materials in parts by weight: 0.06-0.1 part of molasses solution; the volume ratio of molasses to water in the molasses solution is 1: (0.5-1.5).

7. The admixture for ultra-slow concrete according to claim 6, wherein: the weight ratio of the molasses solution to the modified phosphogypsum powder is 1: (150-200).

8. A method for preparing the admixture special for ultra-slow concrete according to any one of claims 1 to 7, comprising the following steps of:

and mixing the raw materials, and uniformly stirring to obtain the special additive for ultra-slow concrete.