Attapulgite modified polycarboxylic acid water reducing agent and preparation method thereof

Abstract

The application belongs to the technical field of concrete admixtures, and particularly relates to a modified attapulgite polycarboxylic acid water reducing agent and a preparation method thereof, the water reducing agent being composed of polycarboxylic acid and modified attapulgite; the modified attapulgite is directly grafted into the molecular structure of polycarboxylic acid through active groups; and the preparation method of the water reducing agent comprises the following specific steps: S1. mixing and uniformly reacting silane coupling agent and attapulgite treated by acid and alkali, and then obtaining modified attapulgite through ultrasonic dispersion after the reaction; S2. uniformly mixing and pre-reacting polycarboxylic acid monomer and an initiator, adding modified attapulgite again for reaction after the pre-reaction, and obtaining the attapulgite modified polycarboxylic acid water reducing agent after washing and drying. The grafting modification technology makes the interaction between attapulgite and polycarboxylic acid molecules more stable and effective, and significantly improves the workability of the water reducing agent.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of concrete admixtures, and specifically relates to a modified attapulgite polycarboxylate superplasticizer and a preparation method thereof. BACKGROUND

[0002] Polycarboxylate superplasticizers are widely used in the field of concrete due to their excellent water-reducing effect and good adaptability. However, existing polycarboxylate superplasticizers have poor stability in high-temperature and alkaline environments, and the synthesis process is complex and the cost is high.

[0003] Attapulgite is a clay mineral with unique structure and properties, widely used in various industrial fields. Attapulgite can be used in combination with polycarboxylate superplasticizers to improve the dispersibility, adhesion and water retention of the superplasticizers. Based on the combination of attapulgite and polycarboxylate superplasticizers, some specific advantages are brought, but there are also some disadvantages.

[0004] The specific advantages are as follows: it can improve the dispersibility: attapulgite has a nanoscale fibrous structure and high specific surface area, when used in combination with polycarboxylate superplasticizers, it can provide more adsorption sites, which helps the superplasticizers to disperse better in the concrete system. This dispersion is beneficial to improve the uniform distribution of cement particles and improve the workability of concrete.

[0005] Enhance adhesion: attapulgite has strong adhesion properties and can form a certain cohesive network in the concrete slurry. By combining with polycarboxylate superplasticizers, the cohesiveness of concrete can be improved, the bleeding phenomenon of concrete can be reduced, and the anti-segregation performance of concrete can be improved, especially in high-slump self-compacting concrete.

[0006] Improve water retention: the adsorption capacity of attapulgite enables it to play a role in water retention in concrete, reducing water loss and preventing dry shrinkage cracks in the hardening process of concrete. This is particularly important for concrete construction in high-temperature, dry environments.

[0007] Green and environmentally friendly: attapulgite is a natural mineral material with good chemical stability and low cost. Its environmentally friendly and non-toxic properties meet the current trend of green building materials, reducing the proportion of organic chemicals in the superplasticizer system and improving environmental friendliness.

[0008] However, the existing modified polycarboxylate superplasticizers prepared by mixing method also have the following disadvantages:

[0009] Excessive influence of dispersibility on water-reducing effect: the high adsorption of attapulgite, while improving dispersibility, may also adsorb the active components of polycarboxylate superplasticizers, resulting in a weakening of the effective components of the superplasticizers, affecting their adsorption and dispersion ability on cement particles, and thus leading to a less-than-expected water-reducing effect.

[0010] Negative impact on viscosity: Although the cohesiveness of attapulgite can improve the cohesiveness of concrete, in some cases, this cohesiveness may cause the viscosity of the paste to increase, affecting the fluidity of the concrete and increasing the difficulty of pumping. This may have an adverse effect on concrete that requires high fluidity or self-leveling.

[0011] Compatibility with polycarboxylic acid superplasticizer: Attapulgite is an inorganic material, and its compatibility with organic polymers such as polycarboxylic acid superplasticizer is weak, which may affect the synergy of the two. It is necessary to improve the compatibility of attapulgite through surface modification or functionalization treatment, otherwise it may cause the material system to be unstable.

[0012] Effect on early strength: The water retention of attapulgite may slow down the hydration reaction rate of concrete, especially in low temperature environment, which may cause the growth rate of early strength of concrete to slow down, affecting the construction progress. Therefore, in some projects that require rapid strength growth, its use may need to be weighed.

[0013] Therefore, through reasonable design and modification means, it is of great significance to develop a new attapulgite modified polycarboxylic acid superplasticizer. SUMMARY

[0014] The technical problem to be solved by the present application is to provide an attapulgite modified polycarboxylic acid superplasticizer, which is composed of polycarboxylic acid and modified attapulgite; the modified attapulgite is directly grafted into the molecular structure of polycarboxylic acid through active groups.

[0015] In order to solve the above technical problems, the present application discloses a preparation method of an attapulgite modified polycarboxylic acid superplasticizer, the specific steps are as follows:

[0016] S1. Mix the silane coupling agent with the attapulgite treated with acid and alkali, and then react, after the reaction is completed, ultrasonic dispersion to obtain modified attapulgite;

[0017] S2. Mix the polycarboxylic acid monomer and initiator uniformly for pre-reaction, add the modified attapulgite after the pre-reaction is completed, and then react, wash and dry to obtain the powder-like attapulgite modified polycarboxylic acid superplasticizer.

[0018] Preferably, the powder-like attapulgite modified polycarboxylic acid superplasticizer prepared in S2 is added with sodium hydroxide solution to adjust the pH to 4-6, and then diluted to obtain the liquid form of attapulgite modified polycarboxylic acid superplasticizer.

[0019] In S1, the mass ratio of the silane coupling agent to the acid and alkali treated palygorskite is 1: (30-50); the silane coupling agent exists in the form of an alcohol solution, wherein the mass ratio of the silane coupling agent to the alcohol is 1:200; and the silane coupling agent is KH-570.

[0020] Preferably, the acid and alkali treatment process of the palygorskite is first treated with 1M HCl for 30 min, and then treated with 1M NaOH for 40 min.

[0021] More preferably, the particle size of the palygorskite is 20-200 mesh.

[0022] In S1, the reaction conditions of the silane coupling agent and the acid and alkali treated palygorskite are a temperature of 40-60℃ and a reaction time of 4-6h.

[0023] In S1, the ultrasonic dispersion conditions are a dispersion time of 15-30 min and an ultrasonic wave intensity of 2-5W / cm 2 .

[0024] In S2, the polycarboxylic acid monomer comprises, by mass percentage, 30-50% of acrylic acid (AA), 30-40% of methacrylic acid (MAA), 10-40% of hydroxyethyl acrylate (HEA) and / or hydroxypropyl acrylate (HPA); and the amount of the initiator used is 0.4-1.0% of the polycarboxylic acid monomer by mass percentage.

[0025] Preferably, the initiator is potassium persulfate (KPS).

[0026] In S2, the pre-reaction conditions are a temperature of 60-80℃ and a reaction time of 2-3h.

[0027] In S2, the amount of the modified palygorskite used is 5-10% of the polycarboxylic acid monomer by mass percentage.

[0028] In S2, the reaction time after the addition of the modified palygorskite is 1-2h.

[0029] Specifically, in some embodiments of the present application, the above-mentioned palygorskite modified polycarboxylic acid water reducing agent is added to concrete as one of the concrete admixtures, and the water reducing rate, the slump and the compressive strength of the concrete are tested to verify the possibility of the application of the above-mentioned palygorskite modified polycarboxylic acid water reducing agent in concrete admixtures.

[0030] Beneficial effects: The difference between attapulgite graft modification and direct mixing is that, through graft modification, chemical bonding between attapulgite and polycarboxylic acid molecules can be achieved, thereby significantly enhancing the interfacial bonding force and overall performance. This modification mainly introduces active groups on the surface of attapulgite or links polymers to the surface of attapulgite through covalent bonds, achieving the following effects:

[0031] (1) Chemical bonding enhancement

[0032] During graft modification, the active sites on the surface of attapulgite (such as hydroxyl groups, siloxane bonds, etc.) and the functional groups of polycarboxylic acid (such as carboxyl groups, hydroxyl groups, epoxy groups, etc.) form stable covalent bonds through chemical reaction. This chemical bonding allows the modified attapulgite to be more firmly combined with polycarboxylic acid molecules, avoiding mutual separation in the cement system and improving the overall performance of the water reducing agent;

[0033] (2) Improved dispersibility and stability

[0034] The dispersibility of graft-modified attapulgite in cement paste is significantly improved. Compared with direct mixing of physical bonding, graft modification enhances the interfacial bonding force, reduces the agglomeration effect of polymers, and allows the modified attapulgite to be more uniformly and stably distributed in the system, maintaining a longer active action time;

[0035] (3) Surface performance control

[0036] Graft modification can precisely control the hydrophilicity and lipophilicity of the surface of attapulgite. By introducing different graft chains, the hydrophilicity or hydrophobicity can be directionally enhanced, thereby optimizing the dispersion, adsorption, and rheological properties of polycarboxylic acid water reducing agent. This control ability cannot be achieved by direct mixing;

[0037] (4) Intermolecular synergistic effect

[0038] After graft modification, there is not only electrostatic repulsion and steric hindrance between attapulgite and polycarboxylic acid molecules, but also a synergistic effect of chemical bonds. This synergistic effect can more effectively enhance the adsorption capacity of the water reducing agent in the cement paste, reduce the water consumption in concrete, and improve the strength and durability of concrete.

[0039] Compared with direct mixing, graft modification technology makes the interaction between attapulgite and polycarboxylic acid molecules more stable and effective, significantly improving the workability of the water reducing agent and increasing the water reduction rate in actual use. After graft modification, attapulgite and polycarboxylic acid molecules are more closely combined, significantly improving the dispersibility of the water reducing agent, reducing the water consumption of concrete, and improving the fluidity of the cement paste;

[0040] Enhancing the strength of concrete: By modifying the attapulgite, the microstructure of the cement paste is improved, which increases the compressive strength and flexural strength of the concrete, and enhances its durability.

[0041] Prolonging the action time: Graft modification makes the combination of attapulgite and water reducing agent more stable, prolongs the effective time of water reducing agent in concrete, and improves the operability of construction.

[0042] Improving the adsorption efficiency: The adsorption capacity of the modified attapulgite surface to cement particles is enhanced, reducing the loss of polycarboxylate superplasticizer in the paste, and improving the use efficiency of the superplasticizer.

[0043] Optimizing the interface performance: Graft modification significantly improves the interface performance between attapulgite and polycarboxylic acid, promoting the uniform distribution of cement particles and reducing the slump loss. DETAILED DESCRIPTION

[0044] The experimental methods described in the following examples are conventional methods unless otherwise specified. The reagents and materials described in the following examples are commercially available unless otherwise specified. The performance test methods for the superplasticizer products described in the following examples are conventional methods used in the field for evaluating the performance of superplasticizers.

[0045] Example 1:

[0046] (1) Modification of attapulgite

[0047] Select attapulgite with a moderate particle size (20-200 mesh) 100g, and perform surface acid and base treatment. The acid is 1M HCl, and the treatment time is 30min. The base is 1M NaOH, and the treatment time is 40min. After treatment, the acid and base treated attapulgite is obtained.

[0048] Use 2g of silane coupling agent KH-570 to further modify the acid and base treated attapulgite. Mix the coupling agent with the solvent at a mass ratio of 1:200 to prepare a coupling agent solution. The solvent is methanol or ethanol. Mix the coupling agent solution with the acid and base treated attapulgite uniformly, and react at a reaction temperature of 40℃ for 4h to introduce active groups such as hydroxyl or carboxyl groups on the surface of the attapulgite, enhancing its binding force with polycarboxylic acid molecules. Use ultrasonic waves to disperse the product after the reaction for 15min, with an ultrasonic intensity of 2W / cm 2 , and obtain the silane coupling agent modified attapulgite with a particle size of 200-400nm.

[0049] (2) Preparation of polycarboxylic acid superplasticizer

[0050] In a reaction kettle, polycarboxylic acid precursor was synthesized according to conventional process, and the monomer ratio and reaction conditions were controlled during the synthesis process. The monomers were added to the reaction kettle according to the following composition: 30 g of acrylic acid (AA), 40 g of methacrylic acid (MAA), and the rest was 30 g of hydroxyethyl acrylate (HEA) or hydroxypropyl acrylate (HPA), initiator: potassium persulfate (KPS), 0.4 g; reaction temperature 60°C, pre-reaction time 2h; after pre-reaction, 5g of silane coupling agent modified palygorskite was added, and reacted for 1h; the obtained modified polycarboxylic acid water reducing agent was washed and dried to obtain a powder palygorskite modified polycarboxylic acid water reducing agent; the surface energy of the powder palygorskite modified polycarboxylic acid water reducing agent was detected by contact angle method or surface tension method, and the surface energy was 80mN / m. Subsequently, the above powder was added to a sodium hydroxide solution to adjust the pH to 4 and dilute to obtain a liquid palygorskite modified polycarboxylic acid water reducing agent.

[0051] The prepared water reducing agent product has excellent performance, and the water reducing rate can reach 16%. When the dosage is 0.5% of the cement dosage, compared with the use of ordinary water reducing agent (naphthalene series water reducing agent) under the same water-cement ratio, the slump can be increased by more than 10 cm, and the compressive strength can be increased by more than 15%.

[0052] Example 2:

[0053] (1) Palygorskite modification treatment

[0054] Select palygorskite with moderate particle size (20-200 mesh) 100g, and perform surface acid-base treatment, wherein 1M HCl is used for 30min. After 38min of treatment with 1M NaOH, acid-base treated palygorskite is obtained;

[0055] 2.2g of silane coupling agent KH-570 is used to further modify the acid-base treated palygorskite. The coupling agent is mixed with a solvent in a mass ratio of 1:200 to prepare a coupling agent solution, and the solvent is methanol or ethanol; the coupling agent solution and the acid-base treated palygorskite are mixed uniformly, and the reaction is carried out at a reaction temperature of 45°C for 6h, so as to introduce active groups such as hydroxyl and carboxyl groups on the surface of the palygorskite, and enhance the binding force with the polycarboxylic acid molecules; the product after the reaction is dispersed by ultrasonic wave for 20min, and the ultrasonic wave intensity is 3W / cm 2 . After dispersion, the silane coupling agent modified palygorskite with a particle size of 200-400nm is obtained.

[0056] (2) Preparation of polycarboxylic acid water reducing agent

[0057] In the reaction kettle, the polycarboxylic acid precursor was synthesized according to the conventional process, and the monomer ratio and reaction conditions were controlled during the synthesis process. The monomers were added to the reaction kettle according to the following composition: acrylic acid (AA) 35 g, methacrylic acid (MAA) 38 g, the rest is hydroxyethyl acrylate (HEA) or hydroxypropyl acrylate (HPA) 27 g, initiator: potassium persulfate (KPS), 0.5 g; reaction temperature 65°C, pre-reaction time 2.5 h; after pre-reaction, 6 g of silane coupling agent modified palygorskite was added, and the reaction was continued for 1.5 h; the obtained modified polycarboxylic acid water reducing agent was washed and dried to obtain a powder palygorskite modified polycarboxylic acid water reducing agent; the surface energy of the powder palygorskite modified polycarboxylic acid water reducing agent was detected by contact angle method or surface tension method, and the surface energy was 90 mN / m. Subsequently, the above powder was added to a sodium hydroxide solution to adjust the pH to 6.5 and dilute to obtain a liquid palygorskite modified polycarboxylic acid water reducing agent.

[0058] The performance of the water reducing agent prepared in this example was tested using the same water reducing agent product performance test method, and the test results showed that the water reducing rate of the water reducing agent prepared in this example could reach 16%. The dosage was 0.5% of the cement dosage, and under the same water-cement ratio, compared with the use of ordinary water reducing agent (naphthalene series water reducing agent), the slump could be increased by more than 10 cm, and the compressive strength could be increased by more than 15%.

[0059] Example 3:

[0060] (1) Palygorskite modification treatment

[0061] Select palygorskite with moderate particle size (20-200 mesh) 100 g, and perform surface acid-base treatment, wherein the acid is 1M HCl, and the treatment time is 40 min, and the base is 1M NaOH, and the treatment time is 20 min to obtain acid-base treated palygorskite;

[0062] Use 2.4 g of silane coupling agent KH-570 to further modify the acid-base treated palygorskite, mix the coupling agent with the solvent according to the mass ratio of 1:200 to prepare a coupling agent solution, and the solvent is methanol or ethanol; mix the coupling agent solution with the acid-base treated palygorskite uniformly, and react at a reaction temperature of 50°C for 5h, so as to introduce active groups such as hydroxyl and carboxyl groups to the surface of the palygorskite, and enhance the binding force with the polycarboxylic acid molecules; use ultrasonic waves to disperse the product after the reaction is completed for 30 min, and the ultrasonic wave intensity is 4W / cm 2 , and the particle size of the silane coupling agent modified palygorskite is 200-400 nm.

[0063] (2) Preparation of polycarboxylic acid water reducing agent

[0064] In a reaction kettle, polycarboxylic acid precursor was synthesized according to conventional process, and the monomer ratio and reaction conditions were controlled during the synthesis process. The monomers were added to the reaction kettle according to the following composition: 40 g of acrylic acid (AA), 36 g of methacrylic acid (MAA), and the rest was 24 g of hydroxyethyl acrylate (HEA) or hydroxypropyl acrylate (HPA); initiator: potassium persulfate (KPS), 0.7 g; reaction temperature 70°C, pre-reaction time 3h; after pre-reaction, 7 g of modified attapulgite was added, and reacted for 1h; the obtained modified polycarboxylic acid water reducing agent was washed and dried to obtain a powder attapulgite modified polycarboxylic acid water reducing agent; the surface energy of the powder attapulgite modified polycarboxylic acid water reducing agent was detected by contact angle method or surface tension method, and the surface energy was 80 mN / m. Subsequently, the above powder was added to a sodium hydroxide solution to adjust the pH to 7 and dilute to obtain a liquid attapulgite modified polycarboxylic acid water reducing agent.

[0065] The performance of the water reducing agent prepared in this example was tested by using the same water reducing agent product performance test method, and the test results showed that the water reducing rate of the water reducing agent prepared in this example could reach 10%. When the dosage was 0.7% of the cement dosage, the slump could be increased by more than 7 cm and the compressive strength could be increased by more than 13% compared with the use of ordinary water reducing agent (naphthalene series water reducing agent) under the same water-cement ratio.

[0066] Example 4:

[0067] (1) Modification of attapulgite

[0068] 100 g of attapulgite with moderate particle size (20-200 mesh) was selected for surface acid-base treatment, wherein 1M HCl was used for 45 min of treatment, and 1M NaOH was used for 25 min of treatment to obtain acid-base treated attapulgite;

[0069] 2.6 g of silane coupling agent KH-570 was used to further modify the acid-base treated attapulgite, and the coupling agent was mixed with a solvent in a mass ratio of 1:200 to prepare a coupling agent solution, and the solvent was methanol or ethanol; the coupling agent solution and the acid-base treated attapulgite were mixed uniformly, and reacted at a reaction temperature of 60°C for 5h, so as to introduce active groups such as hydroxyl and carboxyl groups to the surface of the attapulgite, and enhance the bonding force with the polycarboxylic acid molecules; the product after the reaction was dispersed by ultrasonic wave for 15 min, and the ultrasonic wave intensity was 5W / cm 2 , and the silane coupling agent modified attapulgite with a particle size of 200-400 nm was obtained after dispersion.

[0070] (2) Preparation of polycarboxylic acid water reducing agent

[0071] In a reaction kettle, polycarboxylic acid precursor was synthesized according to conventional process, and the monomer ratio and reaction conditions were controlled during the synthesis process. The monomers were added to the reaction kettle according to the following composition: 45 g of acrylic acid (AA), 34 g of methacrylic acid (MAA), and the rest was 21 g of hydroxyethyl acrylate (HEA) or hydroxypropyl acrylate (HPA); initiator: potassium persulfate (KPS), 0.8 g; reaction temperature 75°C, pre-reaction time 2.5 h; after pre-reaction, 8 g of silane coupling agent modified palygorskite was added, and reacted for another 1.5 h; the obtained modified polycarboxylic acid water reducer was washed and dried to obtain a powder palygorskite modified polycarboxylic acid water reducer; the surface energy of the powder palygorskite modified polycarboxylic acid water reducer was detected by contact angle method or surface tension method, and the surface energy was 100 mN / m. Subsequently, the above powder was added to a sodium hydroxide solution to adjust the pH to 4 and dilute to obtain a liquid palygorskite modified polycarboxylic acid water reducer.

[0072] The performance of the water reducer prepared in this example was tested by using the same water reducer product performance test method, and the test results showed that the water reducing rate of the water reducer prepared in this example could reach 20%. When the dosage was 0.6% of the cement dosage, the slump could be increased by more than 6 cm and the compressive strength could be increased by more than 10% compared with the use of ordinary water reducer (naphthalene series water reducer) under the same water-cement ratio.

[0073] Example 5:

[0074] (1) Palygorskite modification treatment

[0075] 100 g of palygorskite with moderate particle size (20-200 mesh) was selected for surface acid-base treatment. 1M HCl was used for acid treatment for 50 min, and 1M NaOH was used for base treatment for 34 min to obtain acid-base treated palygorskite.

[0076] 2.8 g of silane coupling agent KH-570 was used to further modify the acid-base treated palygorskite. The coupling agent was mixed with solvent at a mass ratio of 1:200 to prepare a coupling agent solution, and the solvent was methanol or ethanol. The coupling agent solution was mixed with the acid-base treated palygorskite uniformly, and reacted at a reaction temperature of 55°C for 6 h to introduce active groups such as hydroxyl and carboxyl groups on the surface of the palygorskite, thereby enhancing the binding force with the polycarboxylic acid molecules. The product after reaction was dispersed by ultrasonic wave for 30 min, and the ultrasonic wave intensity was 4 W / cm 2 After dispersion, the silane coupling agent modified palygorskite with a particle size of 200-400 nm was obtained.

[0077] (2) Preparation of polycarboxylic acid water reducer

[0078] In a reaction kettle, polycarboxylic acid precursor was synthesized according to conventional process, and the monomer ratio and reaction conditions were controlled during the synthesis process. The monomers were added to the reaction kettle according to the following composition: 50 g of acrylic acid (AA), 32 g of methacrylic acid (MAA), and the rest was 18 g of hydroxyethyl acrylate (HEA) or hydroxypropyl acrylate (HPA); initiator: potassium persulfate (KPS), 1 g; reaction temperature 80°C, pre-reaction time 3h; after pre-reaction, 9 g of silane coupling agent modified palygorskite was added, and reacted for 1.2h; the obtained modified polycarboxylic acid water reducing agent was washed and dried to obtain a powder palygorskite modified polycarboxylic acid water reducing agent; the surface energy of the powder palygorskite modified polycarboxylic acid water reducing agent was detected by contact angle method or surface tension method, and the surface energy was 75 mN / m. Subsequently, the above powder was added to a sodium hydroxide solution to adjust the pH to 7 and dilute to obtain a liquid palygorskite modified polycarboxylic acid water reducing agent.

[0079] The performance of the water reducing agent prepared in this example was tested by using the same water reducing agent product performance test method, and the test results showed that the water reducing rate of the water reducing agent prepared in this example could reach 12%. When the dosage was 1% of the cement dosage, compared with the use of ordinary water reducing agent (naphthalene series water reducing agent) under the same water-cement ratio, the slump could be increased by more than 5 cm, and the compressive strength could be increased by more than 14%.

[0080] Example 6:

[0081] (1) Palygorskite modification treatment

[0082] Select palygorskite with moderate particle size (20-200 mesh) 100 g, and perform surface acid-base treatment, wherein the acid is 1M HCl, and the treatment time is 30 min, and the base is 1M NaOH, and the treatment time is 36 min to obtain acid-base treated palygorskite;

[0083] Use 3 g of silane coupling agent KH-570 to further modify the acid-base treated palygorskite, mix the coupling agent with the solvent according to the mass ratio of 1:200 to prepare a coupling agent solution, and the solvent is methanol or ethanol; mix the coupling agent solution with the acid-base treated palygorskite uniformly, and react at a reaction temperature of 40°C for 4h, so as to introduce active groups such as hydroxyl and carboxyl groups to the surface of the palygorskite, and enhance the binding force with the polycarboxylic acid molecules; use ultrasonic waves to disperse the product after the reaction for 20 min, and the ultrasonic wave intensity is 3W / cm 2 , and the particle size of the silane coupling agent modified palygorskite is 200-400 nm.

[0084] (2) Preparation of polycarboxylic acid water reducing agent

[0085] In a reaction kettle, polycarboxylic acid precursor is synthesized according to conventional process, and monomer ratio and reaction condition are controlled during the synthesis process. The monomers are added into the reaction kettle according to the following composition: 45 g of acrylic acid (AA), 34 g of methacrylic acid (MAA), and the rest is 21 g of hydroxyethyl acrylate (HEA) or hydroxypropyl acrylate (HPA), 0.9 g of initiator: potassium persulfate (KPS); the reaction temperature is 75 DEG C, and the pre-reaction time is 2.5 h; after the pre-reaction, 10 g of modified attapulgite is added, and the reaction is carried out for another 1 h; the obtained modified polycarboxylic acid water reducing agent is washed and dried to obtain a powder attapulgite modified polycarboxylic acid water reducing agent; the surface energy of the powder attapulgite modified polycarboxylic acid water reducing agent is detected by using the contact angle method or the surface tension method, and the detection result shows that the surface energy is 95 mN / m; then, the above powder is added into a sodium hydroxide solution to adjust the pH value to 6, and is diluted to obtain a liquid attapulgite modified polycarboxylic acid water reducing agent.

[0086] The water reducing agent prepared in the embodiment is tested by using the same water reducing agent product performance test method, and the test result shows that the water reducing rate of the water reducing agent prepared in the embodiment can reach 18%. When the mixing amount is 0.9% of the cement amount, and under the same water-cement ratio, compared with the use of a common water reducing agent (naphthalene series water reducing agent), the slump can be increased by more than 8 cm, and the compressive strength can be increased by more than 13%.

[0087] The application provides an attapulgite modified polycarboxylic acid water reducing agent and a preparation method thereof. There are many methods and approaches to realize the technical scheme, and the above description is only the preferred embodiment of the application. It should be pointed out that, for ordinary skilled persons in the technical field, some improvements and decorations can be made without departing from the principle of the application, and these improvements and decorations should also be regarded as the protection scope of the application. The components not mentioned in the embodiment can be realized by using the existing technology.

Claims

1. A method for preparing an attapulgite-modified polycarboxylate superplasticizer, characterized in that, The specific steps are as follows: S1. Mix the silane coupling agent with the acid-base treated attapulgite and react them. After the reaction is completed, disperse the mixture by ultrasonication to obtain the modified attapulgite. S2. Mix the polycarboxylate monomer and initiator evenly for pre-reaction. After the pre-reaction is completed, add modified attapulgite and react again. After washing and drying, obtain attapulgite-modified polycarboxylate superplasticizer. The mass ratio of the silane coupling agent to the acid-alkali treated attapulgite is 1:(30-50); the silane coupling agent exists in the form of an alcohol solution, wherein the mass ratio of the silane coupling agent to the alcohol is 1:200; the silane coupling agent is KH-570. The reaction conditions between the silane coupling agent and the acid-alkali treated attapulgite are: temperature 40-60℃, reaction time 4-6h. In S2, the polycarboxylic acid monomer comprises, by mass percentage, 30-50% acrylic acid, 30-40% methacrylic acid, 10-40% hydroxyethyl acrylate and / or hydroxypropyl acrylate; the amount of the initiator used by mass percentage is 0.4-1.0% of the polycarboxylic acid monomer; the pre-reaction conditions are a temperature of 60-80°C and a reaction time of 2-3 hours; the amount of the modified attapulgite used by mass percentage is 5-10% of the polycarboxylic acid monomer.

2. The preparation method according to claim 1, characterized in that, In S1, the ultrasonic dispersion conditions are dispersion for 15–30 minutes and ultrasonic intensity of 2–5 W / cm. 2 .

3. The preparation method according to claim 1, characterized in that, In S2, the reaction time after adding modified attapulgite is 1-2 hours.

4. A concrete admixture, characterized in that, The concrete admixture comprises an attapulgite-modified polycarboxylate superplasticizer prepared by any one of the preparation methods in claims 1 to 3.