Compound water reducing agent for concrete and concrete

Abstract

The application discloses a compound water reducing agent for concrete and the concrete, wherein the compound water reducing agent for concrete comprises the following raw materials in parts by mass: 100 parts of polycarboxylic acid water reducing agent, 0.2-0.5 parts of hydroxylated cucurbituril, 0.05-0.15 parts of defoaming agent, 20-30 parts of water, and 0.2-0.5 parts of polyaspartate salt, wherein the polyaspartate salt has a molecular weight of 3000-5000 Da. The hydroxylated cucurbituril and the polyaspartate salt are compounded in the polycarboxylic acid water reducing agent, thereby achieving efficient passivation of clay, liberating a large amount of polycarboxylic acid water reducing agent originally adsorbed on the surface of the clay, and making the polycarboxylic acid water reducing agent act on cement particles preferentially. As a result, the tolerance of the water reducing agent to the clay content of the concrete raw materials is significantly improved, the dispersion efficiency of the cement particles is maximized, the dispersion is uniform, the slump retention is significantly improved, and the failure problem of the traditional water reducing agent under high clay content is solved.

Description

Technical Field

[0001] This application relates to the field of concrete, and in particular to a composite water-reducing agent for concrete and concrete. Background Technology

[0002] In the field of construction engineering, concrete is an indispensable basic material, and its performance directly affects the quality and safety of building structures. With the continuous development of the construction industry, the performance requirements for concrete are also increasing, especially in terms of water reduction, enhanced workability, and adaptability to complex raw material conditions. Water-reducing agents, as an important concrete admixture, can significantly improve the fluidity, plasticity, and durability of concrete, playing a key role in improving the overall performance of concrete. The rational use of water-reducing agents can effectively reduce the water-cement ratio, improve the strength and impermeability of concrete, while reducing cement usage and lowering costs, resulting in significant economic and environmental benefits. Therefore, the development of high-performance water-reducing agents has always been an important direction in concrete materials research.

[0003] Currently, polycarboxylate superplasticizers are commonly used in concrete preparation to improve concrete performance. Due to their unique molecular structure and comb-like branched chains, polycarboxylate superplasticizers can form significant steric hindrance and strong electrostatic repulsion on the surface of cement particles, effectively dispersing them.

[0004] In actual concrete production, raw materials and construction processes can cause clay to be mixed into the concrete. For example, river sand and manufactured sand are easily mixed with riverbed silt and clay minerals from differentiated rock layers during mining. During the crushing process of crushed stone aggregate, if the parent rock contains clay interlayers, clay will also adhere to the surface of the aggregate. Aggregates stored in the open during construction may also be contaminated by rainwater washing away sand or by soil mixing into the site. High-quality aggregates are more expensive, and some projects may use aggregates that are not thoroughly cleaned in order to control costs or because the project environment is limited and cannot match the use of high-quality aggregates.

[0005] Existing polycarboxylate superplasticizers improve the workability of concrete, but they often fail when dealing with concrete raw materials with high clay content. This is because clay has a high specific surface area and cation exchange capacity, which causes it to adsorb a large number of superplasticizer molecules. This prevents the superplasticizer, which is originally used to disperse cement particles, from functioning properly. Consequently, the cement particles cannot be fully dispersed, the flowability and slump retention of the concrete deteriorate, and the workability of the concrete is severely affected. Summary of the Invention

[0006] To address the problem of traditional water-reducing agents failing at high mud content, a compound water-reducing agent for concrete and concrete are provided.

[0007] The first inventive objective of this invention is achieved through the following technical solution:

[0008] A compound water-reducing agent for concrete comprises the following raw materials in parts by weight:

[0009] 100 parts of polycarboxylate superplasticizer

[0010] Hydroxylated cucurbituril 0.2–0.5 parts,

[0011] Defoamer 0.05-0.15 parts,

[0012] 20-30 parts water

[0013] 0.2 to 0.5 parts of polyaspartic acid salt, with a molecular weight of 3000 to 5000 Da.

[0014] By adopting the above technical solution, this application uses a compound of hydroxylated cucurbita (H-CB) and polyaspartate (PASP) in polycarboxylate superplasticizer (PCE) to achieve efficient passivation of clay;

[0015] PASP diffuses rapidly, preferentially occupying low-energy sites at the clay edge, and chelates Ca at the clay edge via carboxyl groups. 2+ / Al 3 +, neutralizes the positive charge at the edge of the clay and prevents the clay lamellae from re-aggregating;

[0016] H-CB encapsulates high-energy sites between clay layers, selectively encapsulating K-energy sites between clay layers via cavities. + / Na + This inhibits clay lattice expansion; thus, H-CB (interlayer) and PASP (edge) form a three-dimensional protective network, establishing a double blockade of interlayer + edge, covering all active sites of clay, and reducing the ineffective adsorption of PCE by clay;

[0017] Then, H-CB and PASP adsorbed on the clay form reversible hydrogen bonds with the terminal hydroxyl groups of H-CB and the carboxyl groups of PASP when PCE comes into contact with the clay, constructing a "H-CB-PASP-PCE" ternary complex, which hinders the active adsorption of PCE on the clay.

[0018] In addition, the negative charge of PASP complements the charge neutrality of H-CB, avoiding slurry flocculation caused by local charge overload;

[0019] This releases a large amount of PCE that was originally adsorbed on the surface of clay. PCE then acts preferentially on cement particles, solving the problem of traditional water-reducing agents failing under high mud content. This significantly improves the water-reducing agent's tolerance to mud content in concrete raw materials and its slump retention.

[0020] Optionally, it may also include lignin sulfonate-polyoxyethylene ether graft, wherein the amount of lignin sulfonate-polyoxyethylene ether graft is 10 to 20 parts.

[0021] By adopting the above technical solution, the lignin sulfonate-polyoxyethylene ether graft (LS-POE) has POE chain and sulfonic acid group;

[0022] POE chains have long-chain steric hindrance, which can form a complementary steric hindrance layer with PCE side chains, covering particles of different sizes, thereby increasing the adsorption of water-reducing agents on cement particles.

[0023] Sulfonic acid groups adsorb Al at the edge of clay via charge. 3+ / Ca 2+ In the three-dimensional protective net formed by H-CB and PASP, it enhances the double sealing between layers and edges, reduces the ineffective adsorption of PCE by clay, further improves the tolerance of water-reducing agent to the mud content in concrete raw materials, and after adsorbing on clay, the POE chain of LS-POE prevents clay lamellae from re-aggregating and reduces the yield stress of the slurry.

[0024] This results in improved mud content tolerance, initial water reduction rate, and slump retention.

[0025] Optionally, the grafting rate of polyoxyethylene ether onto the lignin sulfonate benzene ring in the lignin sulfonate-polyoxyethylene ether graft is 40-50%.

[0026] By adopting the above technical solution, the combined effect of LS-POE hydrophilicity balance and adsorption competition optimization at this grafting rate is optimal, and the mud volume tolerance and slump retention are better. If the grafting rate is too low, the proportion of its hydrophobic benzene ring is too high, which can easily cause flocculation. If the grafting rate is too high, too many POE chains are easy to entangle with each other, which can hinder the steric hindrance effect and may also encapsulate the PCE side chains, resulting in a reduction in the water-reducing agent effect.

[0027] Optionally, it may also include 0.1 to 0.25 parts of cyclodextrin-tannic acid complex.

[0028] By employing the aforementioned technical solution and adding a cyclodextrin-tannic acid complex (CD-TA), CD encapsulates the K+ between clay layers through the cavity. + / Na + It inhibits clay lattice expansion, but its efficiency is low. Furthermore, CD cannot effectively chelate Al at the clay edge. 3 +, Incomplete edge blunting results in weak filling ability of cement pores;

[0029] TA neutralizes positive charges by chelating aluminum ions at the edge of clay with its catechol groups, thereby effectively dispersing clay; its phenolic hydroxyl groups can also fill some capillary pores through hydrogen bonding, making the structure dense; however, TA is easily oxidized and deactivated in the high-alkali environment of cement, and has a strong retarding effect on cement hydration, which leads to excessive retarding. It also has problems with poor solubility and easy agglomeration, which limit its practical application effect.

[0030] By forming a cyclodextrin-tannic acid complex (CD-TA), the phenolic hydroxyl groups of TA extend into the cavity of CD, forming a host-guest complex: CD against Ca 2+ The inclusion capacity is improved; the hydrophilic groups on the outer edge of CD enhance the solubility of TA, its cavity protects the phenolic hydroxyl groups of TA from oxidation, and regulates the retardation effect of TA to avoid excessively long initial setting time;

[0031] The two work together to form a target for Ca at the edge of clay particles. 2+ (CD) and Al 3 The dual passivation mechanism of +(TA), combined with the encapsulation of interlayer intercalating agents, strengthens the three-dimensional sealing of "interlayer-edge", effectively inhibits clay damage, and further improves the tolerance of mud content and slump retention; the nanoscale size matches the cement capillary pores, optimizes the filling effect, and can improve the impermeability of concrete.

[0032] Optionally, it may also include 0.1 to 0.18 parts of sodium citrate.

[0033] By adopting the above technical solution, the addition of sodium citrate can chelate free calcium ions, which has a positive effect on slump retention, and also acts as a pH buffer to inhibit the oxidation of TA in CD-TA, thus maintaining its effectiveness.

[0034] Optionally, the polycarboxylate superplasticizer has an EO of 48 and a carboxyl group density of 1.0 mmol / g.

[0035] By adopting the above technical solution, the EO chain and the POE chain of LS-POE form a better complementary steric hindrance effect under these parameters, reducing clay adsorption; the appropriately low carboxyl density reduces competition for clay surface sites with polyaspartic acid salts and reduces hydrogen bonding with hydrogen cucurbitacin, resulting in a higher initial water reduction rate and mud content tolerance.

[0036] Optionally, the molecular weight distribution of the polyaspartate is 4500±200 Da.

[0037] By employing the above technical solution, polyaspartic acid salts at this molecular weight can rapidly diffuse to the edge of the clay and chelate Al. 3+ / Ca 2+ Furthermore, it avoids the entanglement of high molecular weight chains with PCE side chains, thereby maximizing clay passivation efficiency and exhibiting high tolerance for mud content.

[0038] The second objective of this invention is achieved through the following technical solution:

[0039] A type of concrete, the raw materials of which include aggregates, cement, sand, the above-mentioned concrete compound water-reducing agent and water.

[0040] By adopting the above technical solution, the concrete of this application has a high tolerance for mud content.

[0041] In summary, the invention of this application has the following beneficial effects:

[0042] 1. Through the synergistic effect of hydroxylated cucurbituril (H-CB) and polyaspartate (PASP), a "layer-edge" dual blockade is formed, which inhibits clay adsorption and improves the adaptability of water-reducing agent to mud-containing concrete;

[0043] 2. Lignosulfonate-polyoxyethylene ether graft (LS-POE) and cyclodextrin-tannic acid complex (CD-TA) enhance dispersibility and impermeability, while sodium citrate optimizes the retarding effect to ensure workability;

[0044] 3. The molecular weight (3000-5000 Da) of polyaspartate balances the diffusion rate and steric hindrance, maximizing the clay passivation efficiency. Detailed Implementation

[0045] raw material

[0046] The defoamer is a commercially available product, specifically polydimethylsiloxane-polyoxypropylene ether, nonionic, with an HLB value of 7.2 and an active ingredient content of ≥98.5 wt%.

[0047] Cucurbita[6]urea is an Aladdin reagent with a purity >98%.

[0048] Tannic acid is an Aladdin reagent with a purity >99%.

[0049] Tetrabutylammonium bromide and β-cyclodextrin were purchased from Sinopharm Group.

[0050] Propylene oxide, sodium lignosulfonate, and sodium citrate are all commercially available products.

[0051] Polyoxyethylene ether glycidyl ether, EO=15, Mn=700, hydroxyl value is 4.6mg KOH / g.

[0052] The parameters of polyaspartate and polycarboxylate superplasticizer are as follows.

[0053] Preparation of hydroxypropyl cucurbituril (H-CB)

[0054] Hydroxypropyl cucurbituril (H-CB) is prepared as follows:

[0055] Take 10g of cucurbit[6]urea, dissolve it in 100mL of 1mol / L NaOH solution, add 25g of propylene oxide, react at 70℃ for 6h; dialysis purification, freeze drying, and obtain white powder.

[0056] Preparation of lignin sulfonate-polyoxyethylene ether graft (LS-POE) with a grafting rate of 30%

[0057] The preparation method of lignin sulfonate-polyoxyethylene ether graft (LS-POE) is as follows:

[0058] Take 20g of sodium lignosulfonate, dissolve it in 200mL of deionized water, add 15g of polyoxyethylene ether glycidyl ether and 0.25g of tetrabutylammonium bromide, and react at 80℃ and pH=9.5 for 5h.

[0059] Slowly add 3 times the volume of anhydrous ethanol to the reaction solution while stirring until flocculent precipitate appears. Let stand for 30 minutes. After the precipitation is complete, centrifuge at 4000 r / min for 10 minutes and discard the supernatant.

[0060] The precipitate was washed twice with 50wt% ethanol aqueous solution, dried under vacuum at 60℃ to constant weight, crushed to obtain the product, and the grafting rate of POE on the benzene ring of LS-POE was found to be 30±2%.

[0061] Preparation of lignosulfonate-polyoxyethylene ether graft (LS-POE) with a grafting rate of 40%

[0062] The preparation method of lignin sulfonate-polyoxyethylene ether graft (LS-POE) is as follows:

[0063] Take 20g of sodium lignosulfonate, dissolve it in 200mL of deionized water, add 24g of polyoxyethylene ether glycidyl ether and 0.4g of tetrabutylammonium bromide, and react at 80℃ and pH=10.2 for 6h.

[0064] Slowly add 3 times the volume of anhydrous ethanol to the reaction solution while stirring until flocculent precipitate appears. Let stand for 30 minutes. After the precipitation is complete, centrifuge at 4000 r / min for 10 minutes and discard the supernatant.

[0065] The precipitate was washed twice with 50wt% ethanol aqueous solution, dried under vacuum at 60℃ to constant weight, crushed to obtain the product, and the grafting rate of POE on the benzene ring of LS-POE was found to be 40±2%.

[0066] Preparation of lignosulfonate-polyoxyethylene ether graft (LS-POE) with a grafting rate of 45%

[0067] The preparation method of lignin sulfonate-polyoxyethylene ether graft (LS-POE) is as follows:

[0068] Take 20g of sodium lignosulfonate, dissolve it in 200mL of deionized water, add 30g of polyoxyethylene ether glycidyl ether and 0.5g of tetrabutylammonium bromide, and react at 80℃ and pH=10.5 for 8h.

[0069] Slowly add 3 times the volume of anhydrous ethanol to the reaction solution while stirring until flocculent precipitate appears. Let stand for 30 minutes. After the precipitation is complete, centrifuge at 4000 r / min for 10 minutes and discard the supernatant.

[0070] The precipitate was washed twice with 50wt% ethanol aqueous solution, dried under vacuum at 60℃ to constant weight, crushed to obtain the product, and the grafting rate of POE on the benzene ring of LS-POE was found to be 45±2%.

[0071] Preparation of lignin sulfonate-polyoxyethylene ether graft (LS-POE) with a grafting rate of 50%

[0072] The preparation method of lignin sulfonate-polyoxyethylene ether graft (LS-POE) is as follows:

[0073] Take 20g of sodium lignosulfonate, dissolve it in 200mL of deionized water, add 36g of polyoxyethylene ether glycidyl ether and 0.6g of tetrabutylammonium bromide catalyst, and react at 80℃ and pH=10.8 for 10h.

[0074] Slowly add 3 times the volume of anhydrous ethanol to the reaction solution while stirring until flocculent precipitate appears. Let stand for 30 minutes. After the precipitation is complete, centrifuge at 4000 r / min for 10 minutes and discard the supernatant.

[0075] The precipitate was washed twice with 50wt% ethanol aqueous solution, dried under vacuum at 60℃ to constant weight, crushed to obtain the product, and the grafting rate of POE on the benzene ring of LS-POE was found to be 50±2%.

[0076] Preparation of lignosulfonate-polyoxyethylene ether graft (LS-POE) with a grafting rate of 60%

[0077] The preparation method of lignin sulfonate-polyoxyethylene ether graft (LS-POE) is as follows:

[0078] Take 20g of sodium lignosulfonate, dissolve it in 200mL of deionized water, add 45g of polyoxyethylene ether glycidyl ether and 0.8g of tetrabutylammonium bromide, and react at 80℃ and pH=10.8 for 12h.

[0079] Slowly add 3 times the volume of anhydrous ethanol to the reaction solution while stirring until flocculent precipitate appears. Let stand for 30 minutes. After the precipitation is complete, centrifuge at 4000 r / min for 10 minutes and discard the supernatant.

[0080] The precipitate was washed twice with 50wt% ethanol aqueous solution, dried under vacuum at 60℃ to constant weight, crushed to obtain the product, and the grafting rate of POE on the benzene ring of LS-POE was found to be 60±2%.

[0081] Preparation of cyclodextrin-tannic acid complex (CD-TA)

[0082] The preparation method of the cyclodextrin-tannic acid complex (CD-TA) is as follows:

[0083] Take 11.35 g (0.01 mol) of β-cyclodextrin and 17.01 g (0.01 mol) of tannic acid, dissolve them in 300 mL of pH 6.5 phosphate buffer, and stir magnetically at 25 °C for 24 h.

[0084] The mixture was filtered through a 0.22 μm filter membrane and freeze-dried to obtain the complex.

[0085] Preparation of polyaspartic acid salt with a molecular weight of 3000 Da

[0086] Polyaspartic acid salt, prepared by the following method:

[0087] Mix 100g of aspartic acid with 0.5g of H3PO4 and react at 180℃ for 2h (nitrogen protection, flow rate 50mL / min); cool the product to 60℃, add 200mL of deionized water and stir to disperse, slowly add 10wt% NaOH solution until pH 12.5-13.0, heat to 80℃ and stir to react for 1h.

[0088] The hydrolyzed PASP solution was rotary evaporated at 60℃ until the solid content was 20%-30%.

[0089] Add 95% ethanol at a ratio of 1:3 (v / v) and cool in an ice bath to 5°C;

[0090] Centrifuge at 4000 rpm for 15 min, discard the supernatant, wash the precipitate twice with 70% ethanol, and vacuum dry at 60℃ for 24 h. The molecular weight of the obtained polyaspartic acid salt was determined to be 3000±200 Da.

[0091] Preparation of polyaspartic acid salt with a molecular weight of 4000 Da

[0092] Polyaspartic acid salt, prepared by the following method:

[0093] 100g of aspartic acid was mixed with 0.3g of H3PO4 and reacted at 190℃ for 3h (nitrogen protection, flow rate 50mL / min); the product was cooled to 60℃, 200mL of deionized water was added and stirred to disperse, 10wt% NaOH solution was slowly added dropwise until pH 12.5-13.0, and the temperature was raised to 80℃ and stirred to react for 1h.

[0094] The hydrolyzed PASP solution was rotary evaporated at 60℃ until the solid content was 20%-30%.

[0095] The hydrolysate was rotary evaporated (60°C) to a solid content of 20%–30%, and 95% ethanol was added at a ratio of 1:3 (v / v). The mixture was then cooled to 5°C in an ice bath.

[0096] Centrifuge at 4000 rpm for 15 min, discard the supernatant, wash the precipitate twice with 70% ethanol, and vacuum dry at 60℃ for 24 h. The molecular weight of the obtained polyaspartic acid salt was determined to be 4500±200 Da.

[0097] Preparation of polyaspartic acid salt with a molecular weight of 5000 Da

[0098] Polyaspartic acid salt, prepared by the following method:

[0099] 100g of aspartic acid was mixed with 0.1g of H3PO4 and reacted at 200℃ for 4h (nitrogen protection, flow rate 50mL / min); the product was cooled to 60℃, 200mL of deionized water was added and stirred to disperse, 10wt% NaOH solution was slowly added dropwise until pH 12.5-13.0, and the temperature was raised to 80℃ and stirred for 1h.

[0100] The hydrolyzed PASP solution was rotary evaporated at 60℃ until the solid content was 20%-30%.

[0101] The hydrolysate was rotary evaporated (60°C) to a solid content of 20%–30%, and 95% ethanol was added at a ratio of 1:3 (v / v). The mixture was then cooled to 5°C in an ice bath.

[0102] Centrifuge at 4000 rpm for 15 min, discard the supernatant, wash the precipitate twice with 70% ethanol, and vacuum dry at 60℃ for 24 h. The molecular weight of the obtained polyaspartic acid salt was determined to be 5000±250 Da.

[0103] Preparation of polyaspartic acid salt with a molecular weight of 10000 Da

[0104] Polyaspartic acid salt, prepared by the following method:

[0105] Mix 100g aspartic acid and 0.05g H3PO4 and react at 220℃ for 8h (nitrogen protection, flow rate 10mL / min); cool the product to 60℃, add 200mL deionized water and stir to disperse, slowly add 10wt% NaOH solution until pH 12.5-13.0, heat to 80℃ and stir to react for 1h;

[0106] The hydrolyzed PASP solution was rotary evaporated at 60℃ until the solid content was 20%-30%.

[0107] The hydrolysate was rotary evaporated (60°C) to a solid content of 20%–30%, and 95% ethanol was added at a ratio of 1:4 (v / v). The mixture was then cooled to 5°C in an ice bath.

[0108] Centrifuge at 4000 rpm for 15 min, discard the supernatant, wash the precipitate twice with 70% ethanol, and vacuum dry at 60℃ for 24 h. The molecular weight of the obtained polyaspartic acid salt was determined to be 10000±300 Da.

[0109] Preparation Example 1 of Polycarboxylate Superplasticizer (PCE)

[0110] Polycarboxylate superplasticizer (PCE), EO=45, acid-ether ratio (AA:TPEG molar ratio)=3.0:1.

[0111] The ingredients are as follows:

[0112] Methyl allyl polyoxyethylene ether (TPEG), Mn = 22000 Da (EO = 45);

[0113] Acrylic acid (AA), electronic grade, polymerization inhibitor ≤30ppm;

[0114] Chain transfer agent (CPAD), 4-cyano-4-(phenylthiocarbonyl)valeric acid;

[0115] Initiator (V-50), azobisisobutyramidine hydrochloride;

[0116] Deionized water, resistivity ≥18MΩ·cm.

[0117] The preparation process is as follows:

[0118] Add 1100g TPEG to 500mL of deionized water and stir in a 60℃ water bath until completely dissolved; dissolve 108g AA and 3.0g CPAD in 100mL of water in an ice bath and cool to below 5℃ to obtain an AA / CPAD mixture; dissolve 4.4g V-50 in 100mL of water to obtain a V-50 solution, and store it protected from light.

[0119] The TPEG solution was stirred and heated to 65°C under nitrogen protection. AA / CPAD mixture (dropping rate: 2.16 g / min) and V-50 solution (dropping rate: 0.68 g / min) were added dropwise simultaneously. After the addition was complete, the reaction was maintained at 65°C for 2.5 h.

[0120] Cool the reaction solution to 25°C, then add 30 wt% NaOH solution dropwise to adjust the pH to 6.8.

[0121] Slowly add 3.6L of anhydrous ethanol while stirring, let stand for 30 minutes, and then filter.

[0122] The precipitate was washed three times with 500 mL of 70 wt% ethanol each time, and then dried under vacuum at 60 °C for 24 h to obtain PCE.

[0123] The PCE Mn obtained by testing was 37200±1000 Da, and the carboxyl density was 1.05 mmol / g.

[0124] Preparation Example 2 of Polycarboxylate Superplasticizer (PCE)

[0125] Polycarboxylate superplasticizer (PCE), EO = 48, acid-ether ratio (AA:TPEG molar ratio) = 3.2:1.

[0126] The ingredients are as follows:

[0127] Methyl allyl polyoxyethylene ether (TPEG), Mn = 2350 Da (EO = 48);

[0128] Acrylic acid (AA), electronic grade, polymerization inhibitor ≤30ppm;

[0129] Chain transfer agent (CPAD), 4-cyano-4-(phenylthiocarbonyl)valeric acid;

[0130] Initiator (V-50), azobisisobutyramidine hydrochloride;

[0131] Deionized water, resistivity ≥18MΩ·cm.

[0132] The preparation process is as follows:

[0133] Add 864g of TPEG to 400mL of deionized water and stir in a 60℃ water bath until completely dissolved; dissolve 129.6g of AA and 3.0g of CPAD in 100mL of water in an ice bath and cool to below 5℃ to obtain an AA / CPAD mixture; dissolve 4.8g of V-50 in 100mL of water to obtain a V-50 solution, and store it protected from light.

[0134] The TPEG solution was stirred and heated to 65°C under nitrogen protection. AA / CPAD mixture (dropping rate: 2.16 g / min) and V-50 solution (dropping rate: 0.68 g / min) were added dropwise simultaneously. After the addition was complete, the reaction was maintained at 65°C for 2.5 h.

[0135] Cool the reaction solution to 25°C, then add 30 wt% NaOH solution dropwise to adjust the pH to 6.8.

[0136] Slowly add 3.6L of anhydrous ethanol while stirring, let stand for 30 minutes, and then filter.

[0137] The precipitate was washed three times with 500 mL of 70 wt% ethanol each time, and then dried under vacuum at 60 °C for 24 h to obtain PCE.

[0138] The PCE Mn was measured to be 34850±1000 Da and the carboxyl density was 1.01 mmol / g.

[0139] Preparation Example 3 of Polycarboxylate Superplasticizer (PCE)

[0140] Polycarboxylate superplasticizer (PCE), EO=50, acid-ether ratio (AA:TPEG molar ratio)=2.8:1.

[0141] The ingredients are as follows:

[0142] Methyl allyl polyoxyethylene ether (TPEG), Mn = 2400 Da (EO = 50);

[0143] Acrylic acid (AA), electronic grade, polymerization inhibitor ≤30ppm;

[0144] Chain transfer agent (CPAD), 4-cyano-4-(phenylthiocarbonyl)valeric acid;

[0145] Initiator (V-50), azobisisobutyramidine hydrochloride;

[0146] Deionized water, resistivity ≥18MΩ·cm.

[0147] The preparation process is as follows:

[0148] Add 800g TPEG to 300mL of deionized water and stir in a 60℃ water bath until completely dissolved; dissolve 67.2g AA and 3.0g CPAD in 100mL of water in an ice bath and cool to below 5℃ to obtain an AA / CPAD mixture; dissolve 3.5g V-50 in 100mL of water to obtain a V-50 solution, and store it protected from light.

[0149] The TPEG solution was stirred and heated to 65°C under nitrogen protection. AA / CPAD mixture (dropping rate: 2.16 g / min) and V-50 solution (dropping rate: 0.68 g / min) were added dropwise simultaneously. After the addition was complete, the reaction was maintained at 65°C for 2.5 h.

[0150] Cool the reaction solution to 25°C, then add 30 wt% NaOH solution dropwise to adjust the pH to 6.8.

[0151] Slowly add 3.6L of anhydrous ethanol while stirring, let stand for 30 minutes, and then filter.

[0152] The precipitate was washed three times with 500 mL of 70 wt% ethanol each time, and then dried under vacuum at 60 °C for 24 h to obtain PCE.

[0153] The PCE Mn obtained by testing was 48100±1000 Da, and the carboxyl density was 0.81 mmol / g.

[0154] Example 1

[0155] A compound water-reducing agent for concrete, the raw materials of which are polycarboxylate superplasticizer (PCE), hydroxypropyl cucurbituril (H-CB), polyaspartate, defoamer, and water.

[0156] Polycarboxylate superplasticizer (PCE), EO = 48, acid-ether ratio (AA:TPEG molar ratio) = 3.2:1, Mn = 34850±1000 Da, carboxyl density 1.01 mmol / g.

[0157] The molecular weight distribution of polyaspartic acid salt is 4500±200 Da.

[0158] The preparation method is as follows:

[0159] Add 3.5g of polyaspartic acid salt to 250g of deionized water and stir in a water bath at 40±5℃ for 30 minutes until completely transparent;

[0160] Add 1000g PCE and 3.5g H-CB sequentially, maintain a constant temperature water bath of 50±2℃, and mechanically stir at 300r / min for 30min; cool down to 25±3℃, add 1g defoamer, and disperse using a homogenizer at 1500r / min for 5min;

[0161] Transfer to a sealed container and let stand at 25°C in the dark for 24 hours to obtain the compound water-reducing agent.

[0162] Example 2

[0163] A compound water-reducing agent for concrete differs from Example 1 in the amount of raw materials used, specifically 2g of polyaspartic acid salt, 200g of deionized water, 1000g of PCE, 5g of H-CB, and 0.5g of defoamer.

[0164] Example 3

[0165] A compound water-reducing agent for concrete differs from Example 1 in the amount of raw materials used, specifically 5g of polyaspartic acid salt, 300g of deionized water, 1000g of PCE, 2g of H-CB, and 1.5g of defoamer.

[0166] Example 4

[0167] A compound water-reducing agent for concrete, the raw materials of which are polycarboxylate superplasticizer (PCE), hydroxypropyl cucurbituril (H-CB), polyaspartate, lignin sulfonate-polyoxyethylene ether graft (LS-POE), defoamer, and water.

[0168] Polycarboxylate superplasticizer (PCE), EO = 48, acid-ether ratio (AA:TPEG molar ratio) = 3.2:1, Mn = 34850±1000 Da, carboxyl density 1.01 mmol / g.

[0169] The molecular weight distribution of polyaspartic acid salt is 4500±200 Da.

[0170] Lignosulfonate-polyoxyethylene ether graft (LS-POE), grafting rate 30±2%.

[0171] The preparation method is as follows:

[0172] Add 3.5g of polyaspartic acid salt to 250g of deionized water and stir in a water bath at 40±5℃ for 30 minutes until completely transparent;

[0173] Add 1000g PCE, 3.5g H-CB and 150g LS-POE in sequence, maintain a constant temperature water bath of 50±2℃, and mechanically stir at 300r / min for 30min;

[0174] Cool to 25±3℃, add 1g of defoamer, and disperse using a homogenizer at 1500r / min for 5min;

[0175] Transfer to a sealed container and let stand at 25°C in the dark for 24 hours to obtain the compound water-reducing agent.

[0176] Example 5

[0177] A compound water-reducing agent for concrete, which differs from Example 4 in that the grafting rate of LS-POE used is 40±2%.

[0178] Example 6

[0179] A compound water-reducing agent for concrete, which differs from Example 4 in that the grafting rate of LS-POE used is 45±2%.

[0180] Example 7

[0181] A compound water-reducing agent for concrete, which differs from Example 4 in that the grafting rate of LS-POE used is 50±2%.

[0182] Example 8

[0183] A compound water-reducing agent for concrete, which differs from Example 4 in that the grafting rate of LS-POE used is 60±2%.

[0184] Example 9

[0185] A compound water-reducing agent for concrete, the raw materials of which are polycarboxylate superplasticizer (PCE), hydroxypropyl cucurbita (H-CB), polyaspartate, cyclodextrin-tannic acid complex (CD-TA), defoamer, and water.

[0186] Polycarboxylate superplasticizer (PCE), EO = 48, acid-ether ratio (AA:TPEG molar ratio) = 3.2:1, Mn = 34850±1000 Da, carboxyl density 1.01 mmol / g.

[0187] The molecular weight distribution of polyaspartic acid salt is 4500±200 Da.

[0188] The preparation method is as follows:

[0189] Add 3.5g of polyaspartic acid salt to 250g of deionized water and stir in a water bath at 40±5℃ for 30 minutes until completely transparent;

[0190] Add 1000g PCE, 3.5g H-CB, and 2g CD-TA sequentially, maintain a constant temperature water bath of 50±2℃, and mechanically stir at 300r / min for 30min;

[0191] Cool to 25±3℃, add 1g of defoamer, and disperse using a homogenizer at 1500r / min for 5min;

[0192] Transfer to a sealed container and let stand at 25°C in the dark for 24 hours to obtain the compound water-reducing agent.

[0193] Example 10

[0194] A compound water-reducing agent for concrete, based on Example 9, differs in that sodium citrate is also added to the raw materials.

[0195] The preparation method is as follows:

[0196] Add 3.5g of polyaspartic acid salt to 250g of deionized water and stir in a water bath at 40±5℃ for 30 minutes until completely transparent;

[0197] Add 1000g PCE, 3.5g H-CB, 2g CD-TA, and 1.5g sodium citrate in sequence, maintain a constant temperature water bath of 50±2℃, and mechanically stir at 300r / min for 30min;

[0198] Cool to 25±3℃, add 1g of defoamer, and disperse using a homogenizer at 1500r / min for 5min;

[0199] Transfer to a sealed container and let stand at 25°C in the dark for 24 hours to obtain the compound water-reducing agent.

[0200] Example 11

[0201] A compound water-reducing agent for concrete, based on Example 6, differs in that a cyclodextrin-tannic acid complex (CD-TA) is also added to the raw materials.

[0202] The preparation method is as follows:

[0203] Add 3.5g of polyaspartic acid salt to 250g of deionized water and stir in a water bath at 40±5℃ for 30 minutes until completely transparent;

[0204] Add 1000g PCE, 3.5g H-CB, 150g LS-POE, and 2g CD-TA in sequence, maintain a constant temperature water bath of 50±2℃, and mechanically stir at 300r / min for 30min;

[0205] Cool to 25±3℃, add 1g of defoamer, and disperse using a homogenizer at 1500r / min for 5min;

[0206] Transfer to a sealed container and let stand at 25°C in the dark for 24 hours to obtain the compound water-reducing agent.

[0207] Example 12

[0208] A compound water-reducing agent for concrete, based on Example 6, differs in that it also contains cyclodextrin-tannic acid complex (CD-TA) and sodium citrate in the raw materials.

[0209] The preparation method is as follows:

[0210] Add 3.5g of polyaspartic acid salt to 250g of deionized water and stir in a water bath at 40±5℃ for 30 minutes until completely transparent;

[0211] Add 1000g PCE, 3.5g H-CB, 150g LS-POE, 2g CD-TA, and 1.5g sodium citrate in sequence, maintain a constant temperature water bath of 50±2℃, and mechanically stir at 300r / min for 30min.

[0212] Cool to 25±3℃, add 1g of defoamer, and disperse using a homogenizer at 1500r / min for 5min;

[0213] Transfer to a sealed container and let stand at 25°C in the dark for 24 hours to obtain the compound water-reducing agent.

[0214] Example 13

[0215] A compound water-reducing agent for concrete, based on Example 12, differs in that the raw materials contain polycarboxylate superplasticizer (PCE), EO = 45, acid-ether ratio (AA:TPEG molar ratio) = 3.0:1, Mn = 37200±1000 Da, and carboxyl density 1.05 mmol / g.

[0216] Example 14

[0217] A compound water-reducing agent for concrete, based on Example 12, differs in that the raw materials contain polycarboxylate superplasticizer (PCE), EO=50, acid-ether ratio (AA:TPEG molar ratio)=2.8:1, Mn=48100±1000Da, and carboxyl density 0.81mmol / g.

[0218] Example 15

[0219] A compound water-reducing agent for concrete, based on Example 1, differs in that the molecular weight of polyaspartic acid salt in the raw materials is 3000±200 Da.

[0220] Example 16

[0221] A compound water-reducing agent for concrete, based on Example 1, differs in that the molecular weight of polyaspartic acid salt in the raw materials is 5000±250 Da.

[0222] Example 17

[0223] A compound water-reducing agent for concrete differs from that in Example 12 in the amount of raw materials used. Specifically, it consists of 2g polyaspartic acid salt, 200g deionized water, 1000g PCE, 5g H-CB, 0.5g defoamer, 100g LS-POE, 2.5g CD-TA, and 1g sodium citrate.

[0224] Example 18

[0225] A compound water-reducing agent for concrete differs from that in Example 12 in the amount of raw materials used. Specifically, it contains 5g polyaspartic acid salt, 300g deionized water, 1000g PCE, 2g H-CB, 1.5g defoamer, 200g LS-POE, 1g CD-TA, and 1.8g sodium citrate.

[0226] Comparative Example 1

[0227] A water-reducing agent, the raw materials of which are polycarboxylate superplasticizer (PCE), defoamer, and water.

[0228] Polycarboxylate superplasticizer (PCE), EO = 48, acid-ether ratio (AA:TPEG molar ratio) = 3.2:1, Mn = 34850±1000 Da, carboxyl density 1.01 mmol / g.

[0229] The preparation method is as follows:

[0230] Add 1000g PCE to 250g deionized water at 40℃, maintain a constant temperature water bath at 50±2℃, and mechanically stir at 300r / min for 30min;

[0231] Cool to 25±3℃, add 1g of defoamer, and disperse for 5min at 1500r / min using a homogenizer.

[0232] Transfer to a sealed container and let stand at 25°C in the dark for 24 hours to obtain the water-reducing agent.

[0233] Comparative Example 2

[0234] A compound water-reducing agent for concrete, the raw materials of which are polycarboxylate superplasticizer (PCE), polyaspartate, defoamer, and water.

[0235] Polycarboxylate superplasticizer (PCE), EO = 48, acid-ether ratio (AA:TPEG molar ratio) = 3.2:1, Mn = 34850±1000 Da, carboxyl density 1.01 mmol / g.

[0236] The molecular weight distribution of polyaspartic acid salt is 4500±200 Da.

[0237] The preparation method is as follows:

[0238] Add 7g of polyaspartic acid salt to 250g of deionized water and stir in a water bath at 40±5℃ for 30 minutes until completely transparent.

[0239] Add 1000g PCE, maintain a constant temperature water bath of 50±2℃, and mechanically stir at 300r / min for 30min;

[0240] Cool to 25±3℃, add 1g of defoamer, and disperse for 5min at 1500r / min using a homogenizer.

[0241] Transfer to a sealed container and let stand at 25°C in the dark for 24 hours to obtain the compound water-reducing agent.

[0242] Comparative Example 3

[0243] A compound water-reducing agent for concrete, the raw materials of which are polycarboxylate superplasticizer (PCE), hydroxypropyl cucurbita (H-CB), defoamer, and water.

[0244] Polycarboxylate superplasticizer (PCE), EO = 48, acid-ether ratio (AA:TPEG molar ratio) = 3.2:1, Mn = 34850±1000 Da, carboxyl density 1.01 mmol / g.

[0245] The preparation method is as follows:

[0246] Add 1000g PCE and 7g H-CB sequentially to 250g deionized water at 40℃, maintain a constant temperature water bath at 50±2℃, and mechanically stir at 300r / min for 30min.

[0247] Cool to 25±3℃, add 1g of defoamer, and disperse for 5min at 1500r / min using a homogenizer.

[0248] Transfer to a sealed container and let stand at 25°C in the dark for 24 hours to obtain the compound water-reducing agent.

[0249] Comparative Example 4

[0250] A compound water-reducing agent for concrete, based on Example 1, differs in that the molecular weight of polyaspartic acid salt in the raw materials is 10000±300 Da.

[0251] Comparative Example 5

[0252] A compound water-reducing agent for concrete, based on Example 9, differs in that 0.8g of β-cyclodextrin (0.0007mol) and 1.2g of tannic acid (0.007mol) are used instead of 2g of CD-TA.

[0253] The water-reducing agents obtained in Examples 1-18 and Comparative Examples 1-5 were tested.

[0254] Water reduction rate:

[0255] The water reduction rates of Examples 1-18 and Comparative Examples 1-5 were tested according to GB 8076-2008.

[0256] Slump retention:

[0257] According to GB / T 50080-2016, montmorillonite was added to cement paste to simulate clay pollution. The slump retention rate was tested after 1 hour by comparing the mud content of 0% and 5% in Examples 1-18 and Comparative Examples 1-5.

[0258] Mud content tolerance:

[0259] Montmorillonite was added to cement paste to simulate clay contamination. The fluidity of the paste was tested according to GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures". The amount of clay added in Examples 1-18 and Comparative Examples 1-5 when the water-reducing agent failed was determined.

[0260] Impermeability:

[0261] According to GB / T 50082-2009, Examples 1-18 and Comparative Examples 1-5 were tested. The concrete mix proportions were: 300 kg cement, 1100 kg crushed stone, 750 kg sand, 180 kg water, 3 kg water-reducing agent, and 37.5 kg montmorillonite (simulated clay); the cement was 42.5 ordinary Portland cement; the crushed stone was continuously graded from 5 to 25 mm, and the residue rate on a 16 mm sieve was 40 wt%; the fineness modulus of the sand was 2.5-2.9.

[0262] Initial / Final Setting Time: The initial / final setting time of Examples 1, 6, 9-12 and Comparative Example 5 were tested according to GB / T 1346-2011. The concrete mix proportions were: 300 kg cement, 1100 kg crushed stone, 750 kg sand, 180 kg water, 3 kg water-reducing agent, and 37.5 kg montmorillonite (simulated clay). The cement was 42.5 ordinary Portland cement. The crushed stone was continuously graded from 5 to 25 mm, with a 16 mm sieve residue of 40 wt%. The fineness modulus of the sand was 2.5 to 2.9.

[0263] The test results are shown in Tables 1 and 2.

[0264] Table 1. Detection results of Examples 1-18 and Comparative Examples 1-4

[0265]

[0266]

[0267] Table 2. Initial setting time / final setting time test table for Examples 1, 6, 9-12, and Comparative Example 5

[0268] Initial setting time (min) Final setting time (min) Example 1 245 325 Example 6 225 305 Example 9 220 300 Example 10 215 295 Example 11 210 290 Example 12 205 285 Comparative Example 5 310 410

[0269] Based on Tables 1 and 2, comparing Example 1 with Comparative Examples 1 to 3, the initial water reduction rate of Example 1 is significantly greater than that of Comparative Examples 1 to 3. The 1-hour slump retention rate of Example 1 is significantly greater than that of Comparative Examples 1 to 3 at both 0% and 5% mud content. The critical value of mud content tolerance of Example 1 is significantly greater than that of Comparative Examples 1 to 3. The impermeability grade of Example 1 is also better than that of Comparative Examples 1 to 3.

[0270] Therefore, it can be seen that this application uses a combination of hydroxylated cucurbita (H-CB) and polyaspartate (PASP) in polycarboxylate superplasticizer (PCE) to achieve efficient passivation of clay. H-CB (interlayer) and PASP (edge) form a three-dimensional protective network, establishing a double blockade between interlayer and edge, covering all active sites of clay, and reducing the ineffective adsorption of PCE by clay.

[0271] Then, H-CB and PASP adsorbed on the clay form reversible hydrogen bonds with the carboxyl groups of PASP, and construct a "H-CB-PASP-PCE" ternary complex when PCE comes into contact with the clay, which hinders the adsorption of PCE on active clay.

[0272] In addition, the negative charge of PASP complements the charge neutrality of H-CB, avoiding slurry flocculation caused by local charge overload;

[0273] This releases a large amount of PCE that was originally adsorbed on the surface of clay. PCE then acts preferentially on cement particles, solving the problem of traditional water-reducing agents failing under high mud content. This significantly improves the water-reducing agent's tolerance to mud content in concrete raw materials and its slump retention.

[0274] Furthermore, the polyaspartic acid salt used in this application needs to have a low molecular weight to meet the requirements of this application. As can be seen from Examples 1, 15-16, and Comparative Example 4, the polyaspartic acid salts used in Examples 1 and 15-16 have a molecular weight of 3000-5000 Da, and their performance is significantly better than that of Comparative Examples 1-3. However, the polyaspartic acid salt in Comparative Example 4 has a molecular weight of 10000 Da, and its performance is significantly lower than that of Comparative Examples 1-3. The excessively high molecular weight will cause entanglement with the PCE, reducing the effectiveness of the PCE and preventing the beneficial effects of H-CB and PASP from being effectively realized.

[0275] Comparing Examples 1 and Examples 4-8, Examples 4-8 have better initial water reduction rate, 1-hour slump retention rate, mud content tolerance critical value, and impermeability grade than Example 1. This is because Examples 4-8 have added lignin sulfonate-polyoxyethylene ether graft (LS-POE) compared to Example 1.

[0276] Lignosulfonate-polyoxyethylene ether graft (LS-POE) has POE chains and sulfonic acid groups;

[0277] POE chains have long-chain steric hindrance, which can form a complementary steric hindrance layer with PCE side chains, covering particles of different sizes, thereby increasing the adsorption of water-reducing agents on cement particles.

[0278] Sulfonic acid groups adsorb Al at the edge of clay via charge. 3+ / Ca 2+ In the three-dimensional protective net formed by H-CB and PASP, it enhances the double sealing between layers and edges, reduces the ineffective adsorption of PCE by clay, further improves the tolerance of water-reducing agent to the mud content in concrete raw materials, and after adsorbing on clay, the POE chain of LS-POE prevents clay lamellae from re-aggregating and reduces the yield stress of the slurry.

[0279] This improves the tolerance for mud content, the initial water reduction rate, and the slump retention, and then enhances the impermeability of concrete through the action of water-reducing agents.

[0280] Further comparative analysis of Examples 4 to 8 shows that the initial water reduction rate is better in Examples 6 and 7, the 1-hour slump retention rate (0% mud content) is better in Examples 6 and 7, the 1-hour slump retention rate (5% mud content) is better in Examples 6 and 5, and the mud content tolerance is better in Examples 6 and 7. Therefore, in this application, the LS-POE grafting rate is better at 40-50%, with 45% being the best.

[0281] Compared with Examples 1, 9-10, and Comparative Example 5, Comparative Example 5 had a worse initial water reduction rate, 1-hour slump retention rate, critical value of mud content tolerance, and impermeability grade than Example 1. Furthermore, the initial setting time and intermediate and final setting time of Comparative Example 5 were significantly longer than those of Examples 1 and 9-10. The initial water reduction rate, 1-hour slump retention rate, critical value of mud content tolerance, and impermeability grade of Examples 9-10 were better than those of Example 1.

[0282] The reason for the use of Comparative Example 5 is that its cyclodextrin (CD) alone has problems such as low efficiency and incomplete clay passivation, while its tannic acid (TA) alone has problems such as easy oxidation and deactivation, excessive retardation, poor solubility and easy agglomeration.

[0283] In contrast to Example 1, Example 9 incorporates a cyclodextrin-tannic acid complex (CD-TA).

[0284] CD forms a complex with TA, and the phenolic hydroxyl groups of TA extend into the cavity of CD, forming a host-guest complex: CD with Ca 2+ The inclusion capacity is improved; the hydrophilic groups on the outer edge of CD enhance the solubility of TA, its cavity protects the phenolic hydroxyl groups of TA from oxidation, and regulates the retarding effect of TA, avoiding excessively long initial setting time and overcoming the defects of using it alone; moreover, the two work synergistically to form a target for Ca at the edge of clay particles. 2+ (CD) and Al 3 The dual passivation mechanism of +(TA), combined with the encapsulation of interlayer intercalating agents, strengthens the three-dimensional sealing of "interlayer-edge", effectively inhibits clay damage, and further improves the tolerance of mud content and slump retention; the nanoscale size matches the cement capillary pores, optimizes the filling effect, and can improve the impermeability of concrete.

[0285] Compared to Example 9, Example 10 also added sodium citrate to buffer the pH value and chelate calcium ions in the cement, which can improve the effect of CD-TA. The initial water reduction rate, 1-hour slump retention rate (5% mud content), and mud content tolerance threshold of Example 10 are higher than those of Example 9.

[0286] In combination with Examples 11-12, the CD-TA improvement system and LS-POE improvement system of this application can coexist and achieve better improvement effects. Examples 11-12 show better initial water reduction rate, 1-hour slump retention rate (5% mud content), mud content tolerance critical value, and impermeability grade than Example 10.

[0287] Comparing Examples 12-14, the performance parameters of the polycarboxylate superplasticizer used in this application also affect the performance of the final composite superplasticizer. The performance parameters of the polycarboxylate superplasticizers used in Examples 12-14 are different. In the test results, Example 12 showed better initial water reduction rate, 1-hour slump retention rate (5% mud content), and mud content tolerance critical value than Examples 13-14. Therefore, in this application, a polycarboxylate superplasticizer with EO=48 and a carboxyl density of 1.0 mmol / g is preferred.

[0288] Furthermore, in conjunction with Examples 1-3, 6, 9-12, and 17-18, it can be seen that the mass fraction of the compound water-reducing agent of this application is controlled as follows: 100 parts of polycarboxylate water-reducing agent, 0.2-0.5 parts of hydroxylated cucurbita, 0.05-0.15 parts of defoamer, 20-30 parts of water, 0.2-0.5 parts of polyaspartate, 10-20 parts of lignin sulfonate-polyoxyethylene ether graft, 0.1-0.25 parts of cyclodextrin-tannic acid complex, and 0.1-0.18 parts of sodium citrate. This achieves the effect of significantly improving the tolerance of the water-reducing agent of this application to the mud content of concrete raw materials, maximizing the dispersion efficiency of cement particles, ensuring uniform dispersion, and significantly improving slump retention.

[0289] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of protection claimed by the present invention, they are protected by patent law.

Claims

1. A compound water-reducing agent for concrete, characterized in that, The raw materials include the following parts by weight: 100 parts of polycarboxylate superplasticizer Hydroxylated cucurbituril 0.2~0.5 parts, Defoamer 0.05~0.15 parts, 20-30 parts water 0.2 to 0.5 parts of polyaspartic acid salt, with a molecular weight of 3000 to 5000 Da.

2. The composite water-reducing agent for concrete according to claim 1, characterized in that, It also includes lignin sulfonate-polyoxyethylene ether grafts, with an amount of 10-20 parts.

3. The composite water-reducing agent for concrete according to claim 2, characterized in that, The grafting rate of polyoxyethylene ether onto the benzene ring of lignin sulfonate in lignin sulfonate-polyoxyethylene ether grafts is 40-50%.

4. The composite water-reducing agent for concrete according to claim 1, characterized in that, It also includes 0.1 to 0.25 parts of cyclodextrin-tannic acid complex.

5. The composite water-reducing agent for concrete according to claim 4, characterized in that, It also includes 0.1 to 0.18 parts of sodium citrate.

6. The composite water-reducing agent for concrete according to claim 1, characterized in that, The polycarboxylate superplasticizer has an EO=48 and a carboxyl group density of 1.0 mmol / g.

7. The composite water-reducing agent for concrete according to claim 1, characterized in that, The molecular weight distribution of polyaspartate is 4500±200 Da.

8. A type of concrete, characterized in that, The raw materials include aggregates, cement, sand, the concrete compound water-reducing agent as described in any one of claims 1 to 7, and water.

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