A high-slump-retention polycarboxylic mother liquor composite admixture suitable for high-fines-content working conditions of limestone dry-process machine-made sand and a preparation method thereof

Abstract

The application discloses a high-slump-retaining polycarboxylic mother liquor composite admixture suitable for a high-powder-content working condition of a limestone dry-method machine-made sand and a preparation method thereof. The high-slump-retaining polycarboxylic mother liquor composite admixture is compounded by a high-water-reducing polycarboxylic mother liquor, a slow-release slump-retaining polycarboxylic mother liquor, a mud-resistant functional additive, a retarding regulator and water. In terms of 40% solid content of the mother liquor, the mass percentage of each component is as follows: the high-water-reducing polycarboxylic mother liquor is 20% to 30%, the slow-release slump-retaining polycarboxylic mother liquor is 10% to 20%, the mud-resistant functional additive is 0.5% to 3%, the retarding regulator is 1% to 4%, and the balance is water. The application adopts a triple synergistic action principle of constructing high-water-reducing dispersion compensation, slow-release continuous slump retention and stone powder targeted shielding, and solves the industry pain points of high-powder-content machine-made sand concrete, such as high stone powder high adsorption of limestone dry-method machine-made sand, fast concrete slump loss and performance short board of a single polycarboxylic mother liquor.

Description

Technical Field

[0001] This invention relates to the field of water-reducing agents for concrete, and in particular to a high-slump-retention polycarboxylate mother liquor composite admixture suitable for high-powder-content dry-process manufactured sand with limestone and its preparation method. Background Technology

[0002] The dry-process limestone sand production process omits the water washing step, resulting in a stone powder content in the finished sand that is generally as high as 8% to 18%. Compared with ordinary manufactured sand and natural river sand, this type of high-powder-content manufactured sand has the characteristics of large specific surface area and strong surface activity, and exhibits a significant adsorption effect on polycarboxylate superplasticizer molecules.

[0003] Currently, most commercially available polycarboxylate admixtures are formulated using high-water-reducing mother liquor. The core design logic of this system lies in achieving instantaneous dispersion through high water reduction, resulting in a high initial water reduction rate, but the dosage of slow-release plasticizing components is relatively insufficient. Under the high-powder content conditions of dry-process manufactured sand, a large number of water-reducing agent molecules are rapidly adsorbed and consumed by stone powder, causing a sharp decline in the slump and spread of concrete in a short period of time, with particularly severe losses after 1 and 2 hours. The resulting deterioration in concrete workability can easily lead to quality and safety problems such as pump blockage and slab cracking during construction.

[0004] However, the industry currently lacks a specific admixture compounding system adapted to dry-process high-silt manufactured sand. Conventional admixtures struggle to achieve an effective balance between the three core properties of "high water reduction rate," "anti-mud adsorption," and "long-term slump retention," resulting in insufficient overall adaptability and an inability to meet actual engineering needs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a high-slump-resistance polycarboxylate mother liquor composite admixture adapted to the high-powder-content conditions of dry limestone manufactured sand and its preparation method.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A high-slump-retaining polycarboxylate mother liquor composite admixture suitable for high-powder-content dry-process limestone sand production is formulated from high-water-reducing polycarboxylate mother liquor, slow-release slump-retaining polycarboxylate mother liquor, anti-mud functional aid, retarder, and water. Based on a 40% solids content mother liquor mass percentage, the component ratios are: high-water-reducing polycarboxylate mother liquor 20%–30%, slow-release slump-retaining polycarboxylate mother liquor 10%–20%, anti-mud functional aid 0.5%–3%, retarder 1%–4%, with the remainder being water. The high water-reducing polycarboxylate mother liquor has a high-density carboxyl comb structure without slow-release ester groups, and its acid-ether molar ratio is 3.8-4.5; the slow-release slump-preserving polycarboxylate mother liquor contains alkaline-hydrolyzable ester functional monomers, and its acid-ether molar ratio is 2.4-3.2.

[0007] In one embodiment, the high water-reducing polycarboxylate mother liquor comprises the following raw materials in parts by weight: 100 parts isopentenyl alcohol polyoxyethylene ether or isobutylenyl alcohol polyoxyethylene ether macromonomer, 5.8–7.2 parts acrylic acid with an acid-ether ratio of 0.058–0.072, 1.2–1.8 parts hydrogen peroxide with a concentration of 27.5%, 0.20–0.35 parts ascorbic acid, and 0.25–0.40 parts mercaptopropionic acid; the high water-reducing polycarboxylate mother liquor is synthesized from the raw materials by oxidation-reduction under low-temperature conditions; the high water-reducing polycarboxylate mother liquor is free of hydroxyethyl acrylate and hydroxypropyl acrylate slow-release monomers; the high water-reducing polycarboxylate mother liquor has a weight-average molecular weight of 38,000–45,000 and a solid content of 40% ± 1%.

[0008] In one embodiment, the slow-release, slump-retaining polycarboxylate mother liquor comprises the following raw materials in parts by weight: 100 parts polyether macromonomer, 2.4–2.8 parts acrylic acid, 1.2–1.6 parts hydroxyethyl acrylate, and 0.8–1.2 parts hydroxypropyl acrylate; the copolymer in the slow-release, slump-retaining polycarboxylate mother liquor has hydrolyzable ester groups on its molecular backbone; the weight-average molecular weight of the slow-release, slump-retaining polycarboxylate mother liquor is 32,000–38,000, and the solid content is 40% ± 1%.

[0009] In one embodiment, the raw materials of the anti-mud functional additive include a compound of unsaturated phosphate ester modified monomer and sodium methacrylate, wherein the mass ratio of unsaturated phosphate ester modified monomer to sodium methacrylate is 2:1 to 3:1, and the anti-mud functional additive is compounded from the raw materials.

[0010] In one embodiment, the raw materials of the retarding regulator include sodium gluconate and sucrose, with the mass ratio of sodium gluconate to sucrose being 3:1 to 5:1, and the retarding regulator is formulated from the raw materials.

[0011] This application also provides a method for preparing the high-slump-resistance polycarboxylate mother liquor composite admixture adapted to the high-powder-content conditions of dry limestone manufactured sand, including the following steps: S1. Preparation of high water-reducing polycarboxylate mother liquor: Polyoxyethylene ether macromonomer and water are added to a reaction vessel and stirred at a constant temperature of 30-38℃ until completely dissolved. Hydrogen peroxide is added for pre-activation. A double-dropping process is used to uniformly add acrylic acid aqueous solution and ascorbic acid + mercaptopropionic acid mixed aqueous solution. The acrylic acid is added for 120-150 min, and the ascorbic acid + mercaptopropionic acid mixed aqueous solution is added for 150-180 min. After the addition is completed, the temperature is maintained at 35℃ for 60-90 min, and then cooled to below 30℃. The solution is neutralized to pH 6.0-7.0 with 30% liquid alkali and filtered for later use. S2. Preparation of slow-release, slump-resistant polycarboxylate mother liquor: Using HPEG-2400 polyether macromonomer as the main chain raw material, a low acid-ether molar ratio of 2.4–3.2 was adopted for molecular structure design; a ternary compound of acrylic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate was used as the copolymer functional monomer; the polymerization process adopted the same low-temperature redox initiation system as S1, specifically: hydrogen peroxide was pre-added to the bottom of the reactor, and then a mixed functional monomer solution composed of acrylic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate and a reducing agent solution composed of ascorbic acid and mercaptopropionic acid were simultaneously added dropwise to the reactor through independent flow paths to initiate polymerization simultaneously; after the dropwise addition was completed, a heat preservation and ripening stage was performed to reduce the residual monomer content, and finally, the slow-release, slump-resistant polycarboxylate mother liquor was obtained after neutralization with liquid alkali and filtration; S3. Compounding and molding: Under normal temperature and pressure, high water-reducing mother liquor and slow-release slump-preserving mother liquor are added to the mixing tank in sequence and stirred at a uniform speed for 10-15 minutes; then anti-sludge functional additive and retarder are added, and stirring is continued for 20-30 minutes; finally, water is added to adjust the solid content, and after stirring evenly, the mixture is filtered out to obtain the finished additive.

[0012] Compared with the prior art, this application has at least the following beneficial effects: This application adopts the principle of a triple synergistic effect of high water-reducing dispersion compensation, slow-release continuous plasticity retention, and stone powder targeted shielding. This application employs a high acid-to-ether ratio, non-slow-release ester group-free, high-water-reducing polycarboxylate mother liquor. Relying on high-density carboxyl anchoring groups, it achieves rapid dispersion of cement particles, providing a high initial water-reducing effect. This compensates for the significant ineffective adsorption loss of polycarboxylate molecules by dry-process manufactured sand and gravel powder, ensuring the initial fluidity and low water-cement ratio of the concrete, and guaranteeing the mechanical properties of the matrix. Secondly, the high-water-reducing polycarboxylate mother liquor is combined with a slow-release, slump-retaining polycarboxylate mother liquor containing hydrolyzable ester groups. The slow-release, slump-retaining polycarboxylate mother liquor has low initial anchoring activity and is not easily rapidly adsorbed and consumed by stone powder. In the strongly alkaline environment of the cement paste, it can slowly hydrolyze over time, continuously generating carboxyl active sites. The system continuously replenishes the effective dispersed components consumed by the hydration reaction and stone powder, effectively inhibiting slump decay and solving the slump loss problem under high temperature and long-term transportation conditions. Finally, it combines phosphate ester anti-mud additives and composite retarder. The anti-mud additives can preferentially adsorb on the surface of highly active stone powder particles, occupy ineffective adsorption sites, and form a targeted shielding layer, which greatly reduces the adsorption consumption of stone powder on polycarboxylate mother liquor molecules and improves the anti-mud compatibility of the system. The composite retarder can gently regulate the cement hydration rate and form a synergistic effect with the slow-release mother liquor, avoiding early rapid solidification of the slurry and further optimizing the workability and slump stability of concrete.

[0013] High-water-reducing mother liquor ensures initial dispersion and water-reducing capacity, offsetting stone powder adsorption loss and guaranteeing concrete strength. The slump-retaining mother liquor provides long-lasting, slow-release replenishment of dispersion sites, completely solving the rapid slump loss problem caused by high powder content in dry-process manufactured sand, making it suitable for high-temperature and long-distance transportation conditions. Excellent anti-mud performance: Special phosphate ester anti-mud additives preferentially adsorb stone powder, blocking ineffective adsorption. Compared to traditional admixtures, it improves compatibility under high powder content conditions, eliminating bleeding, sticking, and bottoming phenomena. Stable performance and high tolerance: The mother liquor is prepared using a low-temperature polymerization process, resulting in a uniform molecular weight distribution and strong stability in the compound system. It is compatible with dry-process manufactured sand with a stone powder content of 8%–18%, increasing the duration of concrete workability retention. While ensuring long-term slump retention, it does not delay the later-stage strength development of concrete, possessing excellent pumpability and workability, suitable for various scenarios such as precast components, commercial concrete pouring, and large-scale infrastructure projects.

[0014] This application adopts the principle of triple synergistic effect of high water-reducing dispersion compensation + slow-release continuous plasticity retention + stone powder targeted shielding to solve the industry pain points of high stone powder adsorption of limestone dry-process manufactured sand concrete, rapid concrete slump loss, and the short performance of single polycarboxylate mother liquor from the perspective of molecular structure and macroscopic compatibility. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below through specific embodiments. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0016] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0017] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms and should not be construed as indicating or implying relative importance. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0018] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical connection or internal connection between two components. They can be direct connection or indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0019] To better understand the technical solution of the present invention, the present invention will be described in detail below.

[0020] In this example, one ton of high-slump-retaining polycarboxylate mother liquor composite admixture suitable for high-powder-content dry-process manufactured limestone sand was prepared. The high-slump-retaining polycarboxylate mother liquor composite admixture was composed of high-water-reducing polycarboxylate mother liquor, slow-release slump-retaining polycarboxylate mother liquor, anti-mud functional aid, retarder, and water. Based on the mass percentage of mother liquor with a solid content of 40%, the component ratios were as follows: high-water-reducing polycarboxylate mother liquor 26%, slow-release slump-retaining polycarboxylate mother liquor 15%, anti-mud functional aid 3%, retarder 4%, and water 52%. The preparation ratios of each raw material are shown in Table 1.

[0021] The high-water-reducing polycarboxylate mother liquor is a high-density carboxyl comb-like structure without slow-release ester groups. Its acid-ether molar ratio is 4, weight-average molecular weight is 42,000, solid content is 40%, and it contains no slow-release ester monomers. The high-water-reducing polycarboxylate mother liquor comprises the following raw materials in parts by weight: 100 parts isopentenyl alcohol polyoxyethylene ether or isobutylenyl alcohol polyoxyethylene ether macromonomer, 6 parts acrylic acid with an acid-ether ratio of 0.062, 1.2 parts hydrogen peroxide with a concentration of 27.5%, and 0.20... The product contains 0.25 parts ascorbic acid and 0.25 parts mercaptopropionic acid; the slow-release, slump-preserving polycarboxylic acid mother liquor contains alkaline hydrolyzable ester functional monomers with an acid-ether molar ratio of 2.8, a weight-average molecular weight of 35,000, and a solid content of 40%. The slow-release, slump-preserving polycarboxylic acid mother liquor includes the following raw materials in parts by weight: 100 parts polyether macromonomer, 2.5 parts acrylic acid, 1.2 parts hydroxyethyl acrylate, and 1 part hydroxypropyl acrylate; the anti-mud functional additive is a compound of unsaturated phosphate ester modified monomer and sodium methacrylate in a mass ratio of 2:1; the retarding regulator is a compound of sodium gluconate and sucrose in a mass ratio of 3:1.

[0022]

[0023] The preparation method of the high-slump polycarboxylate mother liquor composite admixture in this embodiment includes the following steps: S1. Preparation of high water-reducing polycarboxylate mother liquor: Polyoxyethylene ether macromonomer and water are added to a reaction vessel and stirred at a constant temperature of 30-38℃ until completely dissolved. Hydrogen peroxide is added for pre-activation. A double-dropping process is used to uniformly add acrylic acid aqueous solution and ascorbic acid + mercaptopropionic acid mixed aqueous solution. The acrylic acid is added for 120-150 min, and the ascorbic acid + mercaptopropionic acid mixed aqueous solution is added for 150-180 min. After the addition is completed, the temperature is maintained at 35℃ for 60-90 min, and then cooled to below 30℃. The solution is neutralized to pH 6.0-7.0 with 30% liquid alkali and filtered for later use. S2. Preparation of slow-release, slump-resistant polycarboxylate mother liquor: Using HPEG-2400 polyether macromonomer as the main chain raw material, a low acid-ether molar ratio of 2.4–3.2 was adopted for molecular structure design; a ternary compound of acrylic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate was used as the copolymer functional monomer; the polymerization process adopted the same low-temperature redox initiation system as S1, specifically: hydrogen peroxide was pre-added to the bottom of the reactor, and then a mixed functional monomer solution composed of acrylic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate and a reducing agent solution composed of ascorbic acid and mercaptopropionic acid were simultaneously added dropwise to the reactor through independent flow paths to initiate polymerization simultaneously; after the dropwise addition was completed, a heat preservation and ripening stage was performed to reduce the residual monomer content, and finally, the slow-release, slump-resistant polycarboxylate mother liquor was obtained after neutralization with liquid alkali and filtration; S3. Compounding and molding: Under normal temperature and pressure, high water-reducing mother liquor and slow-release slump-preserving mother liquor are added to the mixing tank in sequence and stirred at a uniform speed for 10-15 minutes; then anti-sludge functional additive and retarder are added, and stirring is continued for 20-30 minutes; finally, water is added to adjust the solid content, and after stirring evenly, the mixture is filtered out to obtain the finished additive.

[0024] Temperature is controlled below 40℃ throughout S1 and S2; after thorough mixing in S3, the material is filtered through a 100-mesh filter before being discharged.

[0025] In the comparative example, a commercially available polycarboxylate superplasticizer with the same solid content as the high-slump polycarboxylate superplasticizer in the above examples was selected.

[0026] The high-slump-retaining polycarboxylate mother liquor composite admixture adapted for high-powder-content limestone dry-process manufactured sand in the examples and the commercially available polycarboxylate superplasticizer in the comparative example were used to prepare dry-process sand mortar according to Appendix A of GB 50119-2013 "Technical Specification for Application of Concrete Admixtures". The sand was limestone dry-process manufactured sand with a powder content of 12%. The fluidity and time loss of the two dry-process sand mortars were tested. The test results are shown in Table 2.

[0027]

[0028] The above test methods are all test methods stipulated by national and industry standards, and there are no special features or special explanations.

[0029] Results analysis: A mortar flow loss test was conducted using dry-process manufactured sand with a stone powder content of 12%. The initial mortar spread was controlled at 370×370mm, and the change in flowability at different times was tested. As shown in Table 2, the flowability of the commercially available water-reducing polycarboxylate system in the comparative example decreased rapidly over time, with the mortar spread being only 270×270mm after 3 hours, indicating a severe loss of flowability. In contrast, the compound system of this invention, due to the continuous release of anchoring groups and anti-mud additives through alkaline hydrolysis of the slow-release slump-preserving mother liquor, saw its mortar spread increase to 390×390mm after 1 hour, and maintained the initial flowability of 370×370mm after 3 hours, showing no significant flow loss over time. Tests have shown that the dual-mother liquor compound system of this application, in coordination with the retarding and anti-sludge additive, can effectively resist the ineffective adsorption of water-reducing agent molecules by dry-process manufactured sand and gravel powder. It has excellent long-term slump retention and post-plasticization performance, and is suitable for high-temperature, long-distance transportation of high-stone-powder concrete projects. The high-slump-retention polycarboxylate mother liquor composite admixture is suitable for dry-process manufactured sand concrete with a stone powder content of 12%, with an initial slump of 235mm, a slump loss of ≤15mm in 1 hour, a slump retention rate of 93% in 2 hours, excellent workability of the slurry, no bleeding or pump blockage, and meets the strength standards at 3 days and 28 days, satisfying the multiple requirements of engineering for workability, mechanical properties and slump retention effect.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A high-slump-retention polycarboxylate mother liquor composite admixture suitable for high-powder-content dry-process manufactured sand production of limestone, characterized in that: It is a compound of high water-reducing polycarboxylate mother liquor, slow-release slump-preserving polycarboxylate mother liquor, anti-sludge functional additive, retarder, and water; based on the mass percentage of the mother liquor with 40% solid content, the proportions of each component are: high water-reducing polycarboxylate mother liquor 20%–30%, slow-release slump-preserving polycarboxylate mother liquor 10%–20%, anti-sludge functional additive 0.5%–3%, retarder 1%–4%, and the balance being water; The high water-reducing polycarboxylate mother liquor has a high-density carboxyl comb structure without slow-release ester groups, and its acid-ether molar ratio is 3.8-4.5; the slow-release slump-preserving polycarboxylate mother liquor contains alkaline-hydrolyzable ester functional monomers, and its acid-ether molar ratio is 2.4-3.

2.

2. The high-slump-resistance polycarboxylate mother liquor composite admixture according to claim 1, characterized in that, The high water-reducing polycarboxylate mother liquor comprises the following raw materials in parts by weight: 100 parts isopentenyl alcohol polyoxyethylene ether or isobutylenyl alcohol polyoxyethylene ether macromonomer, 5.8–7.2 parts acrylic acid with an acid-ether ratio of 0.058–0.072, 1.2–1.8 parts hydrogen peroxide with a concentration of 27.5%, 0.20–0.35 parts ascorbic acid, and 0.25–0.40 parts mercaptopropionic acid; the high water-reducing polycarboxylate mother liquor is synthesized from the raw materials by oxidation-reduction under low-temperature conditions; the high water-reducing polycarboxylate mother liquor is free of hydroxyethyl acrylate and hydroxypropyl acrylate slow-release monomers; the high water-reducing polycarboxylate mother liquor has a weight-average molecular weight of 38,000–45,000 and a solid content of 40% ± 1%.

3. The high-slump-resistance polycarboxylate mother liquor composite additive according to claim 2, characterized in that, The sustained-release, slump-retaining polycarboxylate mother liquor comprises the following raw materials in parts by weight: 100 parts polyether macromonomer, 2.4–2.8 parts acrylic acid, 1.2–1.6 parts hydroxyethyl acrylate, and 0.8–1.2 parts hydroxypropyl acrylate; the copolymer in the sustained-release, slump-retaining polycarboxylate mother liquor has hydrolyzable ester groups on its molecular backbone; the weight-average molecular weight of the sustained-release, slump-retaining polycarboxylate mother liquor is 32,000–38,000, and the solid content is 40% ± 1%.

4. The high-slump-resistance polycarboxylate mother liquor composite admixture according to claim 1, characterized in that, The raw materials of the anti-mud functional additive include a compound of unsaturated phosphate ester modified monomer and sodium methacrylate, with a mass ratio of unsaturated phosphate ester modified monomer to sodium methacrylate of 2:1 to 3:

1. The anti-mud functional additive is compounded from the raw materials.

5. The high-slump-resistance polycarboxylate mother liquor composite admixture according to claim 1, characterized in that, The raw materials of the retarding regulator include sodium gluconate and sucrose, with a mass ratio of sodium gluconate to sucrose of 3:1 to 5:

1. The retarding regulator is formulated from the raw materials.

6. The method for preparing high-slump-resistance polycarboxylate mother liquor composite admixture according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Preparation of high water-reducing polycarboxylate mother liquor: Polyoxyethylene ether macromonomer and water are added to a reaction vessel and stirred at a constant temperature of 30-38℃ until completely dissolved. Hydrogen peroxide is added for pre-activation. A double-dropping process is used to uniformly add acrylic acid aqueous solution and ascorbic acid + mercaptopropionic acid mixed aqueous solution. The acrylic acid is added for 120-150 min, and the ascorbic acid + mercaptopropionic acid mixed aqueous solution is added for 150-180 min. After the addition is completed, the temperature is maintained at 35℃ for 60-90 min, and then cooled to below 30℃. The solution is neutralized to pH 6.0-7.0 with 30% liquid alkali and filtered for later use. S2. Preparation of slow-release, slump-resistant polycarboxylate mother liquor: Using HPEG-2400 polyether macromonomer as the main chain raw material, a molecular structure design with a low acid-ether molar ratio of 2.4–3.2 is adopted; a ternary compound of acrylic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate is used as the copolymer functional monomer; the polymerization process adopts the same low-temperature redox initiation system as S1. Specifically, hydrogen peroxide is pre-added to the bottom of the reactor, and then a mixed functional monomer solution composed of acrylic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate and a reducing agent solution composed of ascorbic acid and mercaptopropionic acid are simultaneously added dropwise to the reactor through independent flow paths to initiate polymerization simultaneously; after the dropwise addition is completed, a heat preservation and ripening stage is performed to reduce the residual monomer content, and finally, the slow-release, slump-resistant polycarboxylate mother liquor is obtained after neutralization with liquid alkali and filtration. S3. Compounding and molding: Under normal temperature and pressure, high water-reducing mother liquor and slow-release slump-preserving mother liquor are added to the mixing tank in sequence and stirred at a uniform speed for 10-15 minutes; then anti-sludge functional additive and retarder are added, and stirring is continued for 20-30 minutes; finally, water is added to adjust the solid content, and after stirring evenly, the mixture is filtered out to obtain the finished additive.

7. The method for preparing high-slump-resistance polycarboxylate mother liquor composite admixture according to claim 6, characterized in that, Temperature is controlled below 40℃ throughout S1 and S2; after thorough mixing in S3, the material is filtered through a 100-mesh filter before being discharged.

8. A dry-process manufactured sand concrete, characterized in that, The water-reducing agent in the dry-process manufactured sand concrete raw material is a high-slump-retention polycarboxylate mother liquor composite admixture as described in any one of claims 1-5.

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