Compound high-fluidity concrete pumping agent and preparation method thereof

Abstract

This invention provides a compound high-flowability concrete pumping agent and its preparation method. By weight, the concrete pumping agent comprises: 30-45 parts of polycarboxylate composite water-reducing agent, 28-35 parts of chitosan-phosphate interpenetrating network slow-release agent, 0.1-0.2 parts of water-retaining and impermeable composite gel, 8-15 parts of S95 grade slag powder, 0.04-0.08 parts of alkyl glycoside, 0.03-0.06 parts of polyether-modified polysiloxane, and 72-164 parts of deionized water. The concrete pumping agent prepared by this invention has the advantages of strong adaptability and comprehensive functions. It uses polycarboxylate composite water-reducing agent as the core to improve concrete flowability, combines it with alkyl glycoside to improve workability and assist in smooth pumping, and relies on chitosan-phosphate interpenetrating network slow-release agent to reduce slump loss of concrete during pumping, ensuring good flowability during long-distance pumping.

Description

Technical Field

[0001] This invention relates to the field of concrete pumping agent technology, specifically to a compound high-flowability concrete pumping agent and its preparation method. Background Technology

[0002] In modern construction engineering, concrete pumping is widely used in large-scale projects such as high-rise buildings and large bridges due to its high efficiency and strong adaptability. As a key additive to ensure the smooth progress of pumping operations, the performance of concrete pumping agent directly affects the fluidity of concrete, pumping stability and final structural quality.

[0003] Currently, most commonly used concrete pumping agents in the industry are based on polycarboxylate superplasticizers, which improve the flowability of concrete by using single or simple compounding with other additives. However, as engineering projects continue to increase their requirements for pumping distance, structural durability, and low-carbon environmental protection, higher demands are being placed on the multi-performance synergy of pumping agents.

[0004] While existing concrete pumping agents can improve the initial fluidity of concrete to some extent, they often fail to effectively slow down the cement hydration process during long-distance pumping, leading to excessive slump loss and pumping obstruction. Furthermore, some products, in optimizing pumping performance, either neglect the balance between concrete's water retention, impermeability, and strength, or fail to consider the low-carbon requirements of reduced cement usage. Consequently, they struggle to simultaneously meet the comprehensive requirements of engineering projects for smooth pumping, structural compactness, and environmental performance, thus limiting their application in high-standard, large-scale projects. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a compound high-flowability concrete pumping agent and its preparation method, so as to obtain a concrete pumping agent with strong adaptability, suitable for long-distance concrete transportation, maintaining smooth pumping and dense structure.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This application discloses a compound high-flowability concrete pumping agent, which, by weight, comprises: 30-45 parts of polycarboxylate composite water-reducing agent, 28-35 parts of chitosan-phosphate interpenetrating network slow-release agent, 0.1-0.2 parts of water-retaining and impermeable composite gel, 8-15 parts of S95 grade slag powder, 0.04-0.08 parts of alkyl glycoside, 0.03-0.06 parts of polyether-modified polysiloxane, and 72-164 parts of deionized water.

[0007] By implementing the above technical solutions, polycarboxylate composite water-reducing agent, as the core functional component, can improve the fluidity of concrete, providing basic flow conditions for concrete pumping; chitosan-phosphate interpenetrating network slow-release agent can delay the cement hydration process, reduce slump loss of concrete during pumping, and ensure that concrete still has good fluidity during long-distance pumping; water-retaining and impermeable composite gel can enhance the water retention capacity of concrete, reduce bleeding, and improve the impermeability of concrete, avoiding structural defects in concrete after pumping due to insufficient water retention or poor impermeability; S95 grade slag powder can reduce water content... While reducing the amount of cement used and achieving low carbon emissions, the slurry reacts with cement hydration products to improve concrete strength and ensure the mechanical properties of pumped concrete. Alkyl glycosides can introduce appropriate amounts of microbubbles into concrete, improving its workability, aiding in smooth pumping, and enhancing its frost resistance. Polyether-modified polysiloxanes can eliminate excess large air bubbles in concrete, preventing them from reducing concrete strength and ensuring a dense concrete structure after pumping. Deionized water, as a solvent, ensures uniform dispersion of all components, maintaining the stability of the pumping agent system and thus guaranteeing the uniformity of the concrete mixture, facilitating smooth pumping.

[0008] Preferably, by weight, the polycarboxylate composite water-reducing agent comprises: 25-35 parts of salt-resistant star-shaped polycarboxylate water-reducing agent and 5-10 parts of polycarboxylate water-reducing agent mother liquor, wherein the solid content of the polycarboxylate water-reducing agent mother liquor is 40%.

[0009] By setting up the above technical solutions, the salt-resistant star-shaped polycarboxylate superplasticizer can improve the fluidity of concrete, giving the concrete pumping agent the ability to make the concrete meet the basic conditions for pumping. The polycarboxylate superplasticizer mother liquor with a solid content of 40% can further enhance the water-reducing effect and help enhance the fluidity of concrete. The two work together to help the concrete pumping agent better meet the requirements of good fluidity of concrete during the pumping process, ensuring the smooth progress of pumping operations.

[0010] Preferably, by weight, the salt-resistant star-shaped polycarboxylate superplasticizer comprises: 62-68 parts of acrylic acid, 22-25 parts of 2-acrylamide-2-methylpropanesulfonic acid, 10-12 parts of polyethylene glycol monomethyl ether, and 0.6-0.9 parts of azobisisobutyramidine hydrochloride.

[0011] By setting up the above technical solution, acrylic acid, as a polymerizing monomer, can participate in the formation of the main chain of the water-reducing agent, endowing the main chain with charge-related properties and laying the foundation for water-reducing effect; 2-acrylamide-2-methylpropanesulfonic acid, as a functional monomer, can endow the water-reducing agent with salt resistance, helping the concrete pumping agent to still function stably in possible salt environments; polyethylene glycol monomethyl ether participates in polymerization to form branched chains, which can generate steric hindrance effect, reduce cement particle agglomeration, improve concrete fluidity, and help the pumping agent ensure smooth concrete pumping; azobisisobutyramidine hydrochloride, as an initiator, can initiate the polymerization reaction of each monomer, ensuring the smooth synthesis of salt-resistant star-shaped polycarboxylate water-reducing agent, thereby ensuring that this component can stably play its role in water reduction, salt resistance, and fluidity improvement in the concrete pumping agent, meeting the needs of concrete pumping.

[0012] The preferred method for preparing the salt-resistant star-shaped polycarboxylate superplasticizer is as follows: 1) Mix acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, add an appropriate amount of deionized water to dissolve, and control the total mass concentration of the two small molecule monomers, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, to be 30%-35%. Then add polyethylene glycol monomethyl ether, purge with nitrogen gas of ≥99.9% purity for 30-40 min, add azobisisobutyramidine hydrochloride dropwise at a uniform rate over 20-25 min, raise the temperature to 55-60℃, and react at a constant temperature for 4-4.5 h. 2) After the reaction is complete, cool the temperature to 40-45℃, add an appropriate amount of sodium hydroxide solution with a mass concentration of 10%, neutralize to pH 6.0-7.0, and then vacuum concentrate to a solid content of 40%-45% at a vacuum degree of -0.08 to -0.09 MPa and a temperature of 50-55℃ to obtain salt-resistant star-shaped polycarboxylate superplasticizer.

[0013] By setting up the above technical solution, controlling the total mass concentration of the two small molecule monomers, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, and adding polyethylene glycol monomethyl ether, the monomers can be fully dissolved and mixed, laying the foundation for subsequent uniform polymerization. Nitrogen protection can prevent oxygen from interfering with the polymerization reaction, reduce the generation of impurities, and ensure the stable formation of the effective components of the water-reducing agent. The uniform dropwise addition of azobisisobutyramidine hydrochloride and the constant temperature reaction at 55-60℃ can regulate the polymerization reaction rate and product structure, helping to form a star-shaped polymer, which endows the water-reducing agent with water-reducing and salt-resistant properties. Cooling and neutralizing to pH 6.0-7.0 after the reaction can adjust the pH of the water-reducing agent, making it more stable in the concrete system. The combined effect of each preparation step finally yields a stable, salt-resistant star-shaped polycarboxylate water-reducing agent with water-reducing and salt-resistant capabilities. This water-reducing agent can play a role in concrete pumping agents, helping to improve concrete fluidity and ensuring the smooth operation of concrete pumping.

[0014] Preferably, the chitosan-phosphate interpenetrating network sustained-release agent comprises, by weight, 15-20 parts chitosan, 3-5 parts diammonium hydrogen phosphate, 0.08-0.16 parts epichlorohydrin, and 170-380 parts acetic acid solution with a mass concentration of 2%-3%.

[0015] By setting up the above technical solution, chitosan is the basic component for forming the slow-release structure. It can participate in the construction of a structure that is conducive to delaying cement hydration through its own groups, providing a basis for the slump-preserving function of the slow-release agent. Diammonium hydrogen phosphate can provide reactive groups and work synergistically with chitosan to help form a component with slow-release characteristics, providing support for delaying cement hydration and reducing concrete slump loss. Epichlorohydrin, as a crosslinking agent, can promote the formation of an interpenetrating network structure between chitosan and diammonium hydrogen phosphate, enhancing the structural stability and slow-release effect of the slow-release agent. This slow-release agent can ultimately play a long-term slump-preserving function in concrete pumping agents, reducing slump loss of concrete during pumping, ensuring that concrete maintains good fluidity, and facilitating smooth pumping operations.

[0016] Preferably, the degree of deacetylation of chitosan is ≥90%, and the molecular weight is 50,000-80,000 Da.

[0017] By setting the above technical solution, the degree of deacetylation of chitosan is ≥90%, which ensures that its molecule contains a sufficient amount of amino groups (-NH2). These groups can effectively form hydrogen bonds with the hydroxyl groups (-OH) on the surface of cement particles, providing a key functional basis for the chitosan-phosphate ester interpenetrating network slow-release agent to play a role in delaying cement hydration. The molecular weight of chitosan is 50,000-80,000 Da. This molecular weight range allows chitosan to have good solubility in acetic acid solution with a mass concentration of 2%-3%. At the same time, it can react stably with diammonium hydrogen phosphate and epichlorohydrin to form an interpenetrating network structure, avoiding the problems of difficult dissolution due to large molecular weight or fragile network structure due to small molecular weight.

[0018] Preferably, the preparation method of the chitosan-phosphate interpenetrating network sustained-release agent includes the following steps: a1. Add chitosan to acetic acid solution, stir to dissolve, prepare a chitosan solution with a mass concentration of 5%-8%, then add diammonium hydrogen phosphate, stir at 50-55℃ for 1-1.5h, add epichlorohydrin, raise the temperature to 65-70℃, and react at a constant temperature for 5-5.5h to form an interpenetrating network gel. a2. Place the interpenetrating network gel in an appropriate amount of deionized water and dialyze it for 48-60 hours using a dialysis membrane with a molecular weight cutoff of 10000 Da to remove unreacted impurities. Then, vacuum dry the dialyzed gel at 60-65℃ for 8-10 hours and pulverize it to a particle size of 5-10 μm to obtain the chitosan-phosphate interpenetrating network sustained-release agent.

[0019] By setting up the above technical solution, chitosan is added to an acetic acid solution to prepare a chitosan solution with a mass concentration of 5%-8%, which ensures that the chitosan is uniformly dispersed, providing a homogeneous system for the subsequent full reaction with diammonium hydrogen phosphate and epichlorohydrin. By stirring at 50-55℃ and heating to a constant temperature of 65-70℃, the reaction process can be controlled, ensuring that chitosan, diammonium hydrogen phosphate, and epichlorohydrin stably form a structurally complete interpenetrating network gel, laying the structural foundation for the long-term slump retention performance of the slow-release agent. Dialysis using a dialysis membrane with a molecular weight cutoff of 10000 Da can remove unreacted impurities, improve the purity of the slow-release agent, and avoid impurities interfering with its role in the concrete system. Vacuum drying at 60-65℃ and pulverization to a particle size of 5-10μm can ensure that the slow-release agent can be easily and uniformly mixed with other components in the concrete pumping agent. The preparation steps together yield a stable chitosan-phosphate interpenetrating network slow-release agent, which can effectively delay cement hydration in concrete pumping agents, reduce slump loss over 1 hour during concrete pumping, maintain good concrete fluidity, and facilitate smooth pumping operations.

[0020] Preferably, the water-retaining and impermeable composite gel, by weight, comprises: 40-45 parts straw cellulose, 6-9 parts nano silica fume, 35-40 parts sodium hydroxide solution with a mass concentration of 5%-8%, 1.0-1.5 parts silane coupling agent KH-550, and 45-65 parts calcium chloride solution with a mass concentration of 2%-3%.

[0021] By implementing the above technical solutions, straw cellulose serves as the basic water-retaining component, and its own structure can participate in the formation of a water-retaining network. A 5%-8% sodium hydroxide solution modifies the straw cellulose, helping it to better perform its water-retaining function. Nano-silica fume fills cement pores, providing support for improving impermeability. The silane coupling agent KH-550 enhances the compatibility between straw cellulose and nano-silica fume, ensuring their synergistic effect. A 2%-3% calcium chloride solution acts as a crosslinking agent, promoting the formation of a structurally stable composite gel. These components work together to effectively reduce concrete bleeding and improve the impermeability grade of concrete in concrete pumping agents, preventing structural defects caused by insufficient water retention or poor impermeability. This ensures that the concrete retains good performance after pumping, contributing to the quality of pumping operations and subsequent projects.

[0022] Preferably, the preparation method of the water-retaining and impermeable composite gel includes the following steps: b1. Add straw cellulose to sodium hydroxide solution and soak for 2-3 hours. Then wash with an appropriate amount of deionized water until the pH is 6.5-7.0. Dry at 60-65℃ for 4-5 hours to obtain modified straw cellulose. b2. Add nano silica fume and silane coupling agent KH-550 to the modified straw cellulose, stir at 60-65℃ for 2-2.5h, then add calcium chloride solution, crosslink at 50-55℃ for 1.5-2h, and then ultrasonically disperse the system at 300-400W for 20-30min to obtain water-retaining and impermeable composite gel.

[0023] By setting up the above technical solution, soaking and washing straw cellulose in sodium hydroxide solution until the pH reaches 6.5-7.0 and then drying it can modify the straw cellulose, laying the foundation for its subsequent water-retention function. Adding nano-silica fume and silane coupling agent KH-550 to the modified straw cellulose and stirring at 60-65℃ can enhance the compatibility between the modified straw cellulose and nano-silica fume, helping them synergistically improve the impermeability. Adding calcium chloride solution and crosslinking at 50-55℃ can form a structurally stable gel system. Then, ultrasonic dispersion at 300-400W power for 20-30 minutes can prevent the agglomeration of nano-silica fume and ensure the uniformity of gel components. These steps work together to obtain a stable water-retaining and impermeable composite gel. This gel can effectively reduce concrete bleeding and improve the impermeability grade of concrete in concrete pumping agents, avoid structural defects in concrete due to insufficient water retention or poor impermeability, ensure that the concrete still has good performance after pumping, and help the pumping operation to proceed smoothly and the quality of subsequent projects.

[0024] This application also discloses a method for preparing a compound high-flowability concrete pumping agent, comprising the following steps: S1. Place the S95 grade slag powder in a 60-65℃ oven and dry for 30-40 minutes, then set aside. S2. Add deionized water to the reactor and stir continuously at a speed of 300-400 r / min. Slowly add dried S95 grade slag powder and stir for 10-15 min to form a suspension. Maintain the stirring speed, add polycarboxylate composite water-reducing agent and stir for 20-25 min. Then add chitosan-phosphate interpenetrating network slow-release agent and stir for 20-25 min. S3. Continue stirring the mixture obtained in S2 at a speed of 450-500 r / min, add the water-retaining and impermeable composite gel and stir for 15-20 min, then add alkyl glycoside and polyether modified polysiloxane, and continue stirring at the same speed for 20-25 min. S4. Control the system temperature at 25-30℃, stir at 300-400r / min for 30-40min to obtain a uniform transparent or light yellow liquid. Take a sample for testing to verify that the solid content of the system is 35%-42% and the pH is 6.5-7.5. After passing the test, stop stirring to obtain the compound high-flowability concrete pumping agent.

[0025] By setting up the above technical solution, the surface adsorbed water of S95 grade slag powder can be removed after drying, avoiding the influence of moisture on the uniformity of subsequent component dispersion. Adding water-retaining and impermeable composite gel at a speed of 450-500 r / min and stirring can prevent gel agglomeration and ensure uniform dispersion. Subsequent addition of alkyl glycosides and polyether-modified polysiloxane and stirring can integrate auxiliary functional components with the system, ensuring the performance of air-entraining and defoaming functions. Controlling the system temperature at 25-30℃ and stirring at 300-400 r / min, along with testing the solid content (35%-42%) and pH (6.5-7.5), can ensure the stability of the system and that the concentration of effective components meets the standards and the acidity and alkalinity are suitable. Finally, a uniform, transparent or light yellow compound high-flowability concrete pumping agent is obtained, with uniform distribution of each functional component and stable performance, which can effectively endow concrete with high fluidity, long-term slump retention, water retention and impermeability.

[0026] The beneficial effects of this invention are as follows: Polycarboxylate composite water-reducing agent, as the core functional component, can improve the fluidity of concrete and provide basic flow conditions for concrete pumping; chitosan-phosphate interpenetrating network slow-release agent can delay the cement hydration process, reduce slump loss of concrete during pumping, and ensure that concrete still has good fluidity during long-distance pumping; water-retaining and impermeable composite gel can enhance the water retention capacity of concrete, reduce bleeding, and improve the impermeability of concrete, avoiding structural defects in concrete after pumping due to insufficient water retention or poor impermeability; S95 grade slag powder can reduce cement usage and achieve... While being low in carbon, it reacts with cement hydration products to enhance concrete strength and ensure the mechanical properties of pumped concrete. Alkyl glycosides can introduce appropriate amounts of microbubbles into concrete, improving its workability, aiding in smooth pumping, and enhancing its frost resistance. Polyether-modified polysiloxanes can eliminate excess large air bubbles in concrete, preventing them from reducing concrete strength and ensuring a dense concrete structure after pumping. Deionized water, as a solvent, ensures uniform dispersion of all components, maintaining the stability of the pumping agent system and thus guaranteeing the uniformity of the concrete mixture, facilitating smooth pumping.

[0027] Acrylic acid, as a polymerizable monomer, participates in the formation of the main chain of the water-reducing agent, endowing the main chain with charge-related properties and laying the foundation for its water-reducing effect. 2-Acrylamido-2-methylpropanesulfonic acid, as a functional monomer, can endow the water-reducing agent with salt resistance, helping the concrete pumping agent to function stably in potentially salty environments. Polyethylene glycol monomethyl ether participates in polymerization to form branched chains, which can generate steric hindrance effects, reduce cement particle agglomeration, improve concrete fluidity, and contribute to ensuring smooth concrete pumping. Azobisisobutyramidine hydrochloride, as an initiator, can initiate the polymerization reaction of various monomers, ensuring the smooth synthesis of salt-resistant star-shaped polycarboxylate water-reducing agent, thereby ensuring that this component can stably play its role in water reduction, salt resistance, and fluidity improvement in the concrete pumping agent, meeting the needs of concrete pumping.

[0028] Chitosan is the basic component for forming the slow-release structure. It can participate in the construction of a structure that helps delay cement hydration through its own groups, providing a basis for the slump-retaining function of the slow-release agent. Diammonium hydrogen phosphate can provide reactive groups and work synergistically with chitosan to help form a component with slow-release characteristics, providing support for delaying cement hydration and reducing concrete slump loss. Epichlorohydrin, as a crosslinking agent, can promote the formation of an interpenetrating network structure between chitosan and diammonium hydrogen phosphate, enhancing the structural stability and slow-release effect of the slow-release agent. Ultimately, this slow-release agent can play a long-term slump-retaining role in concrete pumping agents, reducing slump loss of concrete during pumping, ensuring that concrete maintains good fluidity, and facilitating smooth pumping operations. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1: This embodiment discloses a compound high-flowability concrete pumping agent, which, by weight, comprises: 30 parts of polycarboxylate composite water-reducing agent, 28 parts of chitosan-phosphate interpenetrating network slow-release agent, 0.1 parts of water-retaining and impermeable composite gel, 8 parts of S95 grade slag powder, 0.04 parts of alkyl glycoside, 0.03 parts of polyether modified polysiloxane, and 72 parts of deionized water.

[0031] Specifically, by weight, the polycarboxylate composite water-reducing agent includes: 25 parts of salt-resistant star-shaped polycarboxylate water-reducing agent and 5 parts of polycarboxylate water-reducing agent mother liquor, wherein the solid content of the polycarboxylate water-reducing agent mother liquor is 40%.

[0032] It should be noted that, by weight, the salt-resistant star-shaped polycarboxylate superplasticizer comprises: 62 parts acrylic acid, 22 parts 2-acrylamide-2-methylpropanesulfonic acid, 10 parts polyethylene glycol monomethyl ether, and 0.6 parts azobisisobutyramidine hydrochloride. The preparation method of the salt-resistant star-shaped polycarboxylate superplasticizer is as follows: 1) Mix acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, add an appropriate amount of deionized water to dissolve, and control the total mass concentration of the two small molecule monomers, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, to be 30%. Then add polyethylene glycol monomethyl ether, purge with nitrogen gas of ≥99.9% purity for 30 min, add azobisisobutyramidine hydrochloride dropwise at a uniform rate over 20 min, raise the temperature to 55℃, and react at a constant temperature for 4 h. 2) After the reaction is complete, cool down to 40°C, add an appropriate amount of sodium hydroxide solution with a mass concentration of 10%, neutralize to pH 6.0, and then vacuum concentrate to a solid content of 40% under vacuum of -0.08MPa and temperature of 50°C to obtain salt-resistant star-shaped polycarboxylate superplasticizer.

[0033] It should be noted that, by weight, the chitosan-phosphate interpenetrating network sustained-release agent comprises: 15 parts chitosan, 3 parts diammonium hydrogen phosphate, 0.08 parts epichlorohydrin, and 285 parts a 2% (w / w) acetic acid solution. The degree of deacetylation of chitosan is 90%, and its molecular weight is 50,000 Da. The preparation method of the chitosan-phosphate interpenetrating network sustained-release agent includes the following steps: a1. Add chitosan to acetic acid solution, stir to dissolve, prepare a 5% chitosan solution, add diammonium hydrogen phosphate, stir at 50℃ for 1 hour, add epichlorohydrin, heat to 65℃, and react at a constant temperature for 5 hours to form an interpenetrating network gel. a2. Place the interpenetrating network gel in an appropriate amount of deionized water and dialyze it for 48 hours using a dialysis membrane with a molecular weight cutoff of 10000 Da to remove unreacted impurities. Then, vacuum dry the dialyzed gel at 60°C for 8 hours and pulverize it to a particle size of 5 μm to obtain the chitosan-phosphate interpenetrating network sustained-release agent.

[0034] It should be noted that, by weight, the water-retaining and impermeable composite gel comprises: 40 parts straw cellulose, 6 parts nano silica fume, 35 parts of a 5% sodium hydroxide solution, 1.0 part of silane coupling agent KH-550, and 45 parts of a 2% calcium chloride solution. The preparation method of the water-retaining and impermeable composite gel includes the following steps: b1. Add straw cellulose to sodium hydroxide solution and soak for 2 hours. Then wash with an appropriate amount of deionized water until the pH is 6.5. Dry at 60℃ for 4 hours to obtain modified straw cellulose. b2. Add nano silica fume and silane coupling agent KH-550 to the modified straw cellulose, stir at 60℃ for 2h, then add calcium chloride solution, crosslink at 50℃ for 1.5h, and then ultrasonically disperse the system at 300W for 20min to obtain water-retaining and impermeable composite gel.

[0035] This embodiment also discloses a method for preparing a compound high-flowability concrete pumping agent, comprising the following steps: S1. Place the S95 grade slag powder in a 60℃ oven and dry for 30 minutes, then set aside. S2. Add deionized water to the reactor and stir continuously at 300 r / min. Slowly add dried S95 grade slag powder and stir for 10 min to form a suspension. Maintain the stirring speed, add polycarboxylate composite water-reducing agent and stir for 20 min. Then add chitosan-phosphate interpenetrating network slow-release agent and stir for 20 min. S3. Continue stirring the mixture obtained in S2 at a speed of 450 r / min, add the water-retaining and impermeable composite gel and stir for 15 min, then add alkyl glycoside and polyether modified polysiloxane, and continue stirring for 20 min while maintaining the stirring speed. S4. Control the system temperature at 25℃, stir at 300r / min for 30min to obtain a uniform transparent or light yellow liquid. Take a sample for testing to verify that the solid content of the system is 35%-42% and the pH is 6.5-7.5. After passing the test, stop stirring to obtain the compound high-flowability concrete pumping agent.

[0036] Example 2: This embodiment discloses a compound high-flowability concrete pumping agent, which, by weight, comprises: 45 parts of polycarboxylate composite water-reducing agent, 35 parts of chitosan-phosphate interpenetrating network slow-release agent, 0.2 parts of water-retaining and impermeable composite gel, 15 parts of S95 grade slag powder, 0.08 parts of alkyl glycoside, 0.06 parts of polyether modified polysiloxane, and 90 parts of deionized water.

[0037] Specifically, by weight, the polycarboxylate composite water-reducing agent includes: 35 parts of salt-resistant star-shaped polycarboxylate water-reducing agent and 10 parts of polycarboxylate water-reducing agent mother liquor, wherein the solid content of the polycarboxylate water-reducing agent mother liquor is 40%.

[0038] It should be noted that, by weight, the salt-resistant star-shaped polycarboxylate superplasticizer comprises: 68 parts acrylic acid, 25 parts 2-acrylamide-2-methylpropanesulfonic acid, 12 parts polyethylene glycol monomethyl ether, and 0.9 parts azobisisobutyramidine hydrochloride. The preparation method of the salt-resistant star-shaped polycarboxylate superplasticizer is as follows: 1) Mix acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, add an appropriate amount of deionized water to dissolve, and control the total mass concentration of the two small molecule monomers, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, to be 35%. Then add polyethylene glycol monomethyl ether, purge with nitrogen gas of ≥99.9% purity for 40 min, add azobisisobutyramidine hydrochloride dropwise at a uniform rate over 25 min, raise the temperature to 60℃, and react at a constant temperature for 4.5 h. 2) After the reaction is completed, cool down to 45°C, add an appropriate amount of sodium hydroxide solution with a mass concentration of 10%, neutralize to pH 7.0, and then vacuum concentrate to a solid content of 45% under vacuum of -0.09MPa and temperature of 55°C to obtain salt-resistant star-shaped polycarboxylate superplasticizer.

[0039] It should be noted that, by weight, the chitosan-phosphate interpenetrating network sustained-release agent comprises: 20 parts chitosan, 5 parts diammonium hydrogen phosphate, 0.16 parts epichlorohydrin, and 230 parts a 3% acetic acid solution. The degree of deacetylation of chitosan is 94%, and its molecular weight is 80,000 Da. The preparation method of the chitosan-phosphate interpenetrating network sustained-release agent includes the following steps: a1. Add chitosan to acetic acid solution, stir to dissolve, prepare chitosan solution with a mass concentration of 8%, then add diammonium hydrogen phosphate, stir at 55℃ for 1.5h, add epichlorohydrin, heat to 70℃, and react at a constant temperature for 5.5h to form interpenetrating network gel. a2. Place the interpenetrating network gel in an appropriate amount of deionized water and dialyze it for 60 hours using a dialysis membrane with a molecular weight cutoff of 10000 Da to remove unreacted impurities. Then, vacuum dry the dialyzed gel at 65°C for 10 hours and pulverize it to a particle size of 10 μm to obtain the chitosan-phosphate interpenetrating network sustained-release agent.

[0040] It should be noted that, by weight, the water-retaining and impermeable composite gel comprises: 45 parts straw cellulose, 9 parts nano silica fume, 40 parts 8% sodium hydroxide solution, 1.5 parts silane coupling agent KH-550, and 65 parts 3% calcium chloride solution. The preparation method of the water-retaining and impermeable composite gel includes the following steps: b1. Add straw cellulose to sodium hydroxide solution and soak for 3 hours. Then wash with an appropriate amount of deionized water until the pH is 7.0. Dry at 65℃ for 5 hours to obtain modified straw cellulose. b2. Add nano silica fume and silane coupling agent KH-550 to the modified straw cellulose, stir at 65℃ for 2.5h, then add calcium chloride solution, crosslink at 55℃ for 2h, and then ultrasonically disperse the system at 400W for 30min to obtain water-retaining and impermeable composite gel.

[0041] This embodiment also discloses a method for preparing a compound high-flowability concrete pumping agent, comprising the following steps: S1. Place the S95 grade slag powder in a 65℃ oven and dry for 40 minutes, then set aside. S2. Add deionized water to the reactor and stir continuously at 400 r / min. Slowly add dried S95 grade slag powder and stir for 15 min to form a suspension. Maintain the stirring speed, add polycarboxylate composite water-reducing agent and stir for 25 min. Then add chitosan-phosphate interpenetrating network slow-release agent and stir for 25 min. S3. Continue stirring the mixture obtained in S2 at a speed of 500 r / min, add the water-retaining and impermeable composite gel and stir for 20 min, then add alkyl glycoside and polyether modified polysiloxane, and continue stirring at the same speed for 25 min. S4. Control the system temperature at 30℃, stir at 400r / min for 40min to obtain a uniform transparent or light yellow liquid. Take a sample for testing to verify that the solid content of the system is 35%-42% and the pH is 6.5-7.5. After passing the test, stop stirring to obtain the compound high-flowability concrete pumping agent.

[0042] Example 3: This embodiment discloses a compound high-flowability concrete pumping agent, which, by weight, comprises: 35 parts of polycarboxylate composite water-reducing agent, 32 parts of chitosan-phosphate interpenetrating network slow-release agent, 0.15 parts of water-retaining and impermeable composite gel, 12 parts of S95 grade slag powder, 0.06 parts of alkyl glycoside, 0.04 parts of polyether modified polysiloxane, and 72 parts of deionized water.

[0043] Specifically, by weight, the polycarboxylate composite water-reducing agent includes: 30 parts of salt-resistant star-shaped polycarboxylate water-reducing agent and 7 parts of polycarboxylate water-reducing agent mother liquor, wherein the solid content of the polycarboxylate water-reducing agent mother liquor is 40%.

[0044] It should be noted that, by weight, the salt-resistant star-shaped polycarboxylate superplasticizer comprises: 65 parts acrylic acid, 23 parts 2-acrylamido-2-methylpropanesulfonic acid, 11 parts polyethylene glycol monomethyl ether, and 0.7 parts azobisisobutyramidine hydrochloride. The preparation method of the salt-resistant star-shaped polycarboxylate superplasticizer is as follows: 1) Mix acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, add an appropriate amount of deionized water to dissolve, and control the total mass concentration of the two small molecule monomers, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, to be 32%. Then add polyethylene glycol monomethyl ether, purge with nitrogen gas of ≥99.9% purity for 35 min, add azobisisobutyramidine hydrochloride dropwise at a uniform rate over 22 min, raise the temperature to 57℃, and react at a constant temperature for 4.2 h. 2) After the reaction is completed, the temperature is lowered to 42°C, and an appropriate amount of sodium hydroxide solution with a mass concentration of 10% is added to neutralize to pH 6.5. Then, the solution is vacuum concentrated to a solid content of 42% under a vacuum of -0.085MPa and a temperature of 52°C to obtain the salt-resistant star-shaped polycarboxylate superplasticizer.

[0045] It should be noted that, by weight, the chitosan-phosphate interpenetrating network sustained-release agent comprises: 17 parts chitosan, 4 parts diammonium hydrogen phosphate, 0.12 parts epichlorohydrin, and 220 parts a 2.5% acetic acid solution. The degree of deacetylation of chitosan is 92%, and its molecular weight is 65,000 Da. The preparation method of the chitosan-phosphate interpenetrating network sustained-release agent includes the following steps: a1. Add chitosan to acetic acid solution, stir to dissolve, prepare a chitosan solution with a mass concentration of 7.2%, then add diammonium hydrogen phosphate, stir at 52℃ for 1.2h, add epichlorohydrin, raise the temperature to 67℃, and react at a constant temperature for 5.2h to form an interpenetrating network gel. a2. Place the interpenetrating network gel in an appropriate amount of deionized water and dialyze it for 55 hours using a dialysis membrane with a molecular weight cutoff of 10000 Da to remove unreacted impurities. Then, vacuum dry the dialyzed gel at 62°C for 9 hours and pulverize it to a particle size of 7 μm to obtain the chitosan-phosphate interpenetrating network sustained-release agent.

[0046] It should be noted that, by weight, the water-retaining and impermeable composite gel comprises: 42 parts straw cellulose, 7 parts nano silica fume, 37 parts sodium hydroxide solution with a mass concentration of 6%, 1.2 parts silane coupling agent KH-550, and 55 parts calcium chloride solution with a mass concentration of 2.5%. The preparation method of the water-retaining and impermeable composite gel includes the following steps: b1. Add straw cellulose to sodium hydroxide solution and soak for 2.5 h. Then wash with an appropriate amount of deionized water until pH 6.7, and dry at 62℃ for 4.5 h to obtain modified straw cellulose. b2. Add nano silica fume and silane coupling agent KH-550 to the modified straw cellulose, stir at 62℃ for 2.2h, then add calcium chloride solution, crosslink at 52℃ for 1.7h, and then ultrasonically disperse the system at 350W for 25min to obtain water-retaining and impermeable composite gel.

[0047] This embodiment also discloses a method for preparing a compound high-flowability concrete pumping agent, comprising the following steps: S1. Place the S95 grade slag powder in a 62℃ oven and dry for 35 minutes, then set aside. S2. Add deionized water to the reactor and stir continuously at 350 r / min. Slowly add dried S95 grade slag powder and stir for 12 min to form a suspension. Maintain the stirring speed, add polycarboxylate composite water-reducing agent and stir for 22 min. Then add chitosan-phosphate interpenetrating network slow-release agent and stir for 22 min. S3. Continue stirring the mixture obtained in S2 at a speed of 475 r / min, add the water-retaining and impermeable composite gel and stir for 17 min, then add alkyl glycoside and polyether modified polysiloxane, and continue stirring at the same speed for 22 min. S4. Control the system temperature at 27℃, stir at 350r / min for 35min to obtain a uniform transparent or light yellow liquid. Take a sample for testing to verify that the solid content of the system is 35%-42% and the pH is 6.5-7.5. After passing the test, stop stirring to obtain the compound high-flowability concrete pumping agent.

[0048] Comparative Example 1: A compound high-flowability concrete pumping agent and its preparation method are disclosed. The only difference between this concrete pumping agent and Example 3 is that salt-resistant star-shaped polycarboxylate superplasticizer is not added, but replaced with ordinary polycarboxylate superplasticizer (commercially available with 40% solid content).

[0049] Comparative Example 2: A compound high-flowability concrete pumping agent and its preparation method are disclosed. The only difference between this concrete pumping agent and Example 3 is that the chitosan-phosphate interpenetrating network slow-release agent is replaced with a commercially available single phosphate slump retainer.

[0050] Comparative Example 3: A compound high-flowability concrete pumping agent and its preparation method are disclosed. The only difference between this concrete pumping agent and Example 3 is that the water-retaining and anti-seepage composite gel is not added, but replaced with a commercially available hydroxypropyl methylcellulose water-retaining agent.

[0051] Comparative Example 4: A compound high-flowability concrete pumping agent and its preparation method are disclosed. The only difference between this concrete pumping agent and Example 3 is that S95 grade slag powder is replaced with an equal weight of cement.

[0052] Comparative Example 5: A compound high-flowability concrete pumping agent and its preparation method are disclosed. The only difference between this concrete pumping agent and Example 3 is that the ultrasonic dispersion step is omitted in the preparation of the water-retaining and impermeable composite gel.

[0053] Comparative Example 6: A compound high-flowability concrete pumping agent and its preparation method are disclosed. The only difference between this concrete pumping agent and Example 3 is that the alkyl glycoside is replaced with a commercially available common triterpenoid saponin air-entraining agent.

[0054] Comparative Example 7: A compound high-flowability concrete pumping agent and its preparation method are disclosed. The only difference between this concrete pumping agent and Example 3 is that in the preparation of the water-retaining and impermeable composite gel, the straw cellulose was not treated with NaOH solution (straw cellulose was used directly).

[0055] Comparative Example 8: A compound high-flowability concrete pumping agent and its preparation method are disclosed. The only difference between this concrete pumping agent and Example 3 is that no nano silica fume is added to the water-retaining and impermeable composite gel (only modified straw cellulose is used).

[0056] Perform performance tests on the concrete pumping agents obtained in the above Examples 1-3 and Comparative Examples 1-8, including initial slump and 1-hour slump loss, air content, bleeding rate, 28-day compressive strength and strength loss after salt corrosion, impermeability grade, pumping pressure, and strength loss after 50 freeze-thaw cycles. The test methods and standards for each performance are as follows: (1) Initial slump and 1-hour slump loss The reference standard is GB / T 50080-2016 "Standard Test Method for Properties of Ordinary Concrete Mixtures". Specific steps: Prepare a concrete mixture according to the mix ratio of water-cement ratio 0.45 and cement dosage of 400 kg / m 3 . Divide the mixture into three layers and pour it into a standard slump cone (cone height 300 mm, upper diameter 100 mm, lower diameter 200 mm). Use a metal rod with a diameter of 16 mm and a length of 600 mm to insert and tamp evenly 25 times for each layer (the tamping depth penetrates the lower layer, and the upper layer is tamped to the surface); after tamping, use a trowel to scrape off the excess mixture at the cone mouth to make the cone mouth surface flat, and then vertically and steadily lift the slump cone (the lifting time of the cone is controlled within 5-10 s to avoid shaking); after the mixture stops flowing, use a steel ruler to measure the vertical distance from the bottom of the slump cone to the highest point of the mixture, which is the initial slump; leave the remaining mixture to stand for 1 hour in an environment with room temperature (20±2°C) and relative humidity ≥50%, repeat the above slump test steps, and calculate the 1-hour slump loss (the initial slump value minus the slump value after 1 hour).

[0057] (2) Air content The reference standard is GB / T 50080-2016 "Standard Test Method for Properties of Ordinary Concrete Mixtures". Specific steps: Use a pneumatic air content tester (volume 5L). First, seal the empty bucket of the instrument and check the airtightness according to the instrument operation instructions (the pressure drop ≤0.01 MPa / 5 min is qualified); divide the prepared concrete mixture into two layers and pour it into the instrument bucket. Use a rod to insert and tamp 25 times for each layer (the lower layer is tamped to the bottom of the bucket, and the upper layer is tamped to half of the lower layer). After vibration, use a trowel to level the bucket mouth, cover the upper cover of the instrument and seal it; open the air inlet valve, inflate the instrument to the specified pressure (0.1 MPa), close the air inlet valve, let it stand for 10 s and then open the exhaust valve. After the pressure is stable, read the air content value, which is the initial air content; leave the mixture to stand for 30 min, repeat the above operation to read the air content, and calculate the 30-min air content fluctuation value (the absolute value of the difference between the two air content values).

[0058] (3) Bleeding rate The reference standard is GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". Specific steps: Take 10L of the prepared concrete mixture and fill it into a graduated cylindrical measuring cylinder (150mm in diameter, 300mm in height). Gently vibrate the cylinder (to avoid segregation of the mixture) and record the initial volume V1. Place the measuring cylinder in a room temperature (20±2℃) environment, cover it (leaving a vent), and observe and record the volume V2 of water seeping from the bottom of the measuring cylinder at 15min, 30min, 45min, and 60min respectively (pour out the seeping water after each reading to avoid double counting). Stop the test after 60min and calculate the bleeding rate (bleeding rate = total bleeding volume V2 within 60min / total water content in the mixture × 100%, where the total water content of the mixture is calculated based on the concrete mix proportion).

[0059] (4) 28-day compressive strength and strength loss after salt corrosion The reference standard is GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". Specific steps: Prepare 100mm×100mm×100mm cubic test blocks according to the concrete mix proportion, with 3 blocks per group; place the test blocks in a standard curing chamber (temperature 20±2℃, relative humidity ≥95%) for 28 days. After curing, remove them and test their compressive strength using a pressure testing machine (range 0-3000kN) at a loading rate of 0.5-1.0MPa per second. Take the average strength of the 3 test blocks as the 28-day compressive strength; take another group of identical test blocks, cure them under standard conditions for 28 days, and then immerse them in a 5% (mass concentration) NaCl solution (the solution should cover the test blocks by more than 50mm, and the solution should be changed every 7 days). After immersion for 28 days, remove them, rinse the surface salt with clean water, wipe them dry, and then determine the strength according to the above compressive strength test method. Calculate the strength loss after salt corrosion (strength loss = (28-day standard curing strength - salt corrosion strength) / 28-day standard curing strength × 100%).

[0060] (5) Permeability grade The reference standard is GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". Specific steps: Prepare 175mm×185mm×150mm impermeability test blocks, 6 blocks per group, and cure under standard conditions for 28 days; apply paraffin wax to the sides of the test blocks and place them into the mold of the impermeability tester (ensuring a seal and no leakage); use a stepwise pressurization method, with an initial pressure of 0.1MPa, increasing by 0.1MPa every 8 hours until water seepage appears on the bottom surface of the test block; record the pressure value P (MPa) of the previous pressure level when water seepage occurs. The impermeability grade is calculated using P=10H-1 (H is the pressure value when water seepage occurs, e.g., 0.1MPa corresponds to P1, 0.2MPa corresponds to P2, and so on). Take the impermeability grade corresponding to the highest pressure of the 4 test blocks that did not seepage out of the 6 test blocks as the final result.

[0061] (6) Pumping pressure The reference standard is GB / T 8076-2008 "Concrete Admixtures". Specific steps: Using a concrete pumping simulation device (125mm pipe diameter, 50m horizontal conveying distance, smooth inner wall of the conveying pipe), prepare sufficient mixture according to the concrete mix proportions; pour the mixture into the hopper of the pumping device, start the pumping equipment, and adjust the pumping speed to 3m / s. 3 / h (simulating the actual construction pumping speed), after the pumping stabilizes (pressure display fluctuation <±0.05MPa), record the pressure value displayed by the pressure sensor, record 5 times consecutively, and take the average value as the pumping pressure.

[0062] (7) Strength loss after 50 freeze-thaw cycles The reference standard is GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". Specific steps: Prepare 100mm×100mm×400mm prism specimens, 3 specimens per group, and cure under standard conditions for 28 days; place the specimens in a freeze-thaw test chamber and use the rapid freeze-thaw method. The freeze-thaw cycle parameters are: freezing at -20℃ for 4 hours (center temperature of the specimen ≤ -15℃), thawing at 20℃ for 4 hours (center temperature of the specimen ≥ 10℃), completing one freeze-thaw cycle; after a total of 50 freeze-thaw cycles, remove the specimens, wipe off surface moisture, and test their compressive strength according to GB / T 50081-2019 standard; simultaneously test the strength of a group of standard-cured specimens that have not undergone freeze-thaw cycles, and calculate the strength loss after freeze-thaw (strength loss = (unfrozen strength - frozen-thawed strength) / unfrozen strength × 100%).

[0063] The results are shown in Table 1.

[0064] Table 1 Performance parameters of concrete pumping agents obtained in Examples 1-3 and Comparative Examples 1-8 Example 1 270 ≤6 2.5 0.2 56.5 5.0 P12 1.5 2.5 Example 2 280 ≤5 2.8 0.15 58.8 4.5 P12 1.4 2.2 Example 3 290 ≤4 3.0 0.1 61.2 4.0 P12 1.3 2.0 Comparative Example 1 200 25 2.0 0.8 45.3 28.5 P8 2.3 13.5 Comparative Example 2 255 19 2.6 0.3 52.1 8.2 P10 1.9 3.8 Comparative Example 3 260 8 2.7 1.6 50.5 7.5 P8 1.8 4.2 Comparative Example 4 265 7 2.8 0.4 52.8 6.0 P10 1.7 3.5 Comparative Example 5 230 15 2.6 0.9 48.6 12.0 P9 2.1 8.5 Comparative Example 6 268 7 3.5 0.3 49.8 6.5 P10 1.9 12.8 Comparative Example 7 258 9 2.7 2.1 46.9 8.8 P7 1.9 6.3 Comparative Example 8 265 7 2.8 0.6 49.2 9.5 P9 1.7 4.8 Referring to Table 1, and taking Example 3 as a reference: In Comparative Example 1, without the addition of salt-resistant star-shaped polycarboxylate superplasticizer, the initial slump decreased to 200 mm (a decrease of 31.0%), the strength loss after salt corrosion increased to 28.5% (an increase of 24.5 percentage points), and the pumping pressure increased to 2.3 MPa (an increase of 76.9%). The reason is that ordinary polycarboxylate superplasticizers lack -N... + (CH3)3 / -SO3 - The positive and negative charge centers cannot form an "anti-salinization film" in a salt environment, leading to cement particle agglomeration, a sharp drop in fluidity, intensified salt corrosion damage, and a significant increase in pumping resistance.

[0065] In Comparative Example 2, replacing the chitosan-phosphate interpenetrating network slow-release agent with a commercially available monophosphate ester resulted in a slump loss of 19 mm after 1 hour (an increase of 375%), and a strength loss after salt corrosion of 8.2% (an increase of 4.2 percentage points). Because the monophosphate ester lacks the hydrogen-bonding stabilizing effect of chitosan, phosphate ester hydrolysis alone cannot maintain long-term slump retention. Insufficient dispersion film stability leads to excessively rapid slump loss and decreased salt corrosion resistance.

[0066] In Comparative Example 3, replacing the water-retaining and impermeable composite gel with hydroxypropyl methylcellulose increased the bleeding rate to 1.6% (an increase of 1500%), and the impermeability grade dropped to P8. Because hydroxypropyl methylcellulose cannot form the three-dimensional hydrogen-bonded water-retaining network of straw cellulose and lacks the pore-filling effect of nano-silica fume, its water retention capacity is sharply reduced, and the increased porosity leads to a significant decrease in impermeability.

[0067] In Comparative Example 4, replacing S95 slag powder with cement reduced the 28-day compressive strength to 52.8 MPa (a decrease of 13.7%) and the impermeability grade to P10. Replacing slag with cement resulted in the loss of the reinforcing effect of CSH gel generated during secondary hydration, and the micro-filling effect of slag was also absent, leading to a decrease in strength and impermeability, and also contradicting the low-carbon concept.

[0068] In Comparative Example 5, the ultrasonic dispersion step was omitted, resulting in an initial slump of 230 mm (a decrease of 20.7%), an increase in pumping pressure to 2.1 MPa (an increase of 61.5%), and a decrease in the impermeability grade to P9. This was because the nano-silica fume agglomerates formed rigid particle clusters, hindering the flow of cement particles and increasing pumping resistance. Furthermore, the agglomerates could not effectively fill the pores, leading to a decrease in impermeability.

[0069] In Comparative Example 6, replacing alkyl glycosides with common triterpenoid saponins increased the gas content to 3.5% (an increase of 16.7%), but the freeze-thaw loss increased to 12.8% (an increase of 540%), and the impermeability grade dropped to P10. The bubbles generated by common air-entraining agents have uneven particle size and poor stability. During freeze-thaw cycles, large bubbles cause internal cracking, resulting in a sharp increase in strength loss. At the same time, the increased porosity reduces impermeability.

[0070] In Comparative Example 7, the straw cellulose was not treated with NaOH, resulting in a water bleeding rate of 2.1% (an increase of 2000%), a decrease in impermeability grade to P7, and a 28-day strength of 46.9 MPa (a decrease of 23.4%). The lignin that was not removed encapsulated the hydroxyl groups, preventing the formation of an effective water-retaining network. This led to an unstable composite gel structure, resulting in increased water bleeding and decreased pulp density.

[0071] In Comparative Example 8, without the addition of nano-silica fume, the impermeability grade dropped to P9, and the strength loss after salt corrosion increased to 9.5% (an increase of 137.5%). The lack of pore-filling effect from nano-silica fume increased the capillary porosity of the cement, allowing salt ions to easily penetrate and corrode the reinforcing steel, thus reducing impermeability and salt corrosion resistance. However, the water-retaining effect of straw cellulose remained unaffected, and the bleeding rate decreased slightly.

[0072] In summary, the concrete pumping agent prepared by this invention has the advantages of strong adaptability and comprehensive functions. It uses polycarboxylate composite water-reducing agent as the core to improve the fluidity of concrete, combines it with alkyl glycosides to improve workability to assist smooth pumping, and relies on chitosan-phosphate interpenetrating network slow-release agent to reduce the slump loss of concrete during pumping, thus ensuring good fluidity during long-distance pumping.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A compound high-flowability concrete pumping agent, characterized in that, By weight, the concrete pumping agent comprises: 30-45 parts of polycarboxylate composite water-reducing agent, 28-35 parts of chitosan-phosphate interpenetrating network slow-release agent, 0.1-0.2 parts of water-retaining and impermeable composite gel, 8-15 parts of S95 grade slag powder, 0.04-0.08 parts of alkyl glycoside, 0.03-0.06 parts of polyether modified polysiloxane, and 72-164 parts of deionized water; By weight, the polycarboxylate composite water-reducing agent comprises: 25-35 parts of salt-resistant star-shaped polycarboxylate water-reducing agent and 5-10 parts of polycarboxylate water-reducing agent mother liquor, wherein the solid content of the polycarboxylate water-reducing agent mother liquor is 40%; By weight, the raw materials for the salt-resistant star-shaped polycarboxylate superplasticizer include: 62-68 parts acrylic acid, 22-25 parts 2-acrylamide-2-methylpropanesulfonic acid, 10-12 parts polyethylene glycol monomethyl ether, and 0.6-0.9 parts azobisisobutyramidine hydrochloride. The preparation method of salt-resistant star-shaped polycarboxylate superplasticizer is as follows: 1) Mix acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, add an appropriate amount of deionized water to dissolve, and control the total mass concentration of the two small molecule monomers, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, to be 30%-35%. Then add polyethylene glycol monomethyl ether, purge with nitrogen gas of ≥99.9% purity for 30-40 min, add azobisisobutyramidine hydrochloride dropwise at a uniform rate over 20-25 min, raise the temperature to 55-60℃, and react at a constant temperature for 4-4.5 h. 2) After the reaction is complete, cool the temperature to 40-45℃, add an appropriate amount of sodium hydroxide solution with a mass concentration of 10%, neutralize to pH 6.0-7.0, and then vacuum concentrate to a solid content of 40%-45% at a vacuum degree of -0.08 to -0.09 MPa and a temperature of 50-55℃ to obtain salt-resistant star-shaped polycarboxylate superplasticizer. The raw materials for the chitosan-phosphate interpenetrating network sustained-release agent, by weight, include: 15-20 parts chitosan, 3-5 parts diammonium hydrogen phosphate, 0.08-0.16 parts epichlorohydrin, and 170-380 parts acetic acid solution with a mass concentration of 2%-3%. The preparation method of the chitosan-phosphate interpenetrating network sustained-release agent includes the following steps: a1. Add chitosan to acetic acid solution, stir to dissolve, prepare a chitosan solution with a mass concentration of 5%-8%, then add diammonium hydrogen phosphate, stir at 50-55℃ for 1-1.5h, add epichlorohydrin, raise the temperature to 65-70℃, and react at a constant temperature for 5-5.5h to form an interpenetrating network gel. a2. Place the interpenetrating network gel in an appropriate amount of deionized water and dialyze it for 48-60 hours using a dialysis membrane with a molecular weight cutoff of 10000 Da to remove unreacted impurities. Then, vacuum dry the dialyzed gel at 60-65℃ for 8-10 hours and pulverize it to a particle size of 5-10 μm to obtain the chitosan-phosphate interpenetrating network sustained-release agent.

2. The compound high-flowability concrete pumping agent according to claim 1, characterized in that, Chitosan has a degree of deacetylation ≥90% and a molecular weight of 50,000-80,000 Da.

3. The compound high-flowability concrete pumping agent according to claim 1, characterized in that, By weight, the water-retaining and impermeable composite gel comprises: 40-45 parts straw cellulose, 6-9 parts nano silica fume, 35-40 parts sodium hydroxide solution with a mass concentration of 5%-8%, 1.0-1.5 parts silane coupling agent KH-550, and 45-65 parts calcium chloride solution with a mass concentration of 2%-3%.

4. The compounded high-flowability concrete pumping agent according to claim 3, characterized in that, The preparation method of the water-retaining and impermeable composite gel includes the following steps: b1. Add straw cellulose to sodium hydroxide solution and soak for 2-3 hours. Then wash with an appropriate amount of deionized water until the pH is 6.5-7.

0. Dry at 60-65℃ for 4-5 hours to obtain modified straw cellulose. b2. Add nano silica fume and silane coupling agent KH-550 to the modified straw cellulose, stir at 60-65℃ for 2-2.5h, then add calcium chloride solution, crosslink at 50-55℃ for 1.5-2h, and then ultrasonically disperse the system at 300-400W for 20-30min to obtain water-retaining and impermeable composite gel.

5. A method for preparing a compound high-flowability concrete pumping agent according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Place the S95 grade slag powder in a 60-65℃ oven and dry for 30-40 minutes, then set aside. S2. Add deionized water to the reactor and stir continuously at a speed of 300-400 r / min. Slowly add dried S95 grade slag powder and stir for 10-15 min to form a suspension. Maintain the stirring speed, add polycarboxylate composite water-reducing agent and stir for 20-25 min. Then add chitosan-phosphate interpenetrating network slow-release agent and stir for 20-25 min. S3. Continue stirring the mixture obtained in S2 at a speed of 450-500 r / min, add the water-retaining and impermeable composite gel and stir for 15-20 min, then add alkyl glycoside and polyether modified polysiloxane, and continue stirring at the same speed for 20-25 min. S4. Control the system temperature at 25-30℃, stir at 300-400r / min for 30-40min to obtain a uniform transparent or light yellow liquid. Take a sample for testing to verify that the solid content of the system is 35%-42% and the pH is 6.5-7.

5. After passing the test, stop stirring to obtain the compound high-flowability concrete pumping agent.