Concrete polycarboxylate superplasticizer and preparation method thereof

Abstract

The invention discloses a concrete polycarboxylate superplasticizer and a preparation method thereof. A precursor of the polycarboxylate superplasticizer comprises vinyl polyoxyethylene ether, or vinyl polyoxyethylene ether and an ester of vinyl polyoxyethylene ether and fluorocarboxylic acid; the mass ratio of the vinyl polyoxyethylene ether to the ester of the vinyl polyoxyethylene ether and the fluorocarboxylic acid is (3-5): 1; the number ratio of carboxyl to side chains in the polycarboxylate superplasticizer is 2.5-3.5. The concrete polycarboxylate superplasticizer provided by the invention has a proper ratio of carboxyl to side chains, and can reliably reduce the flow viscosity of concrete and improve the performance of the concrete.

Description

Technical Field

[0001] The present invention generally relates to the technical field of concrete for engineering construction, and particularly relates to a concrete polycarboxylate water reducer and a preparation method thereof. Background Art

[0002] Due to its high water-reducing performance and the designability of its structure, polycarboxylate cement water reducer has become the main variety of concrete water reducers. With the development of the times, high-strength, high-pumpability and high-durability concrete has become an inevitable trend in the development of contemporary concrete technology. At present, high-strength and ultra-high-strength concrete achieve their high strength by increasing the amount of cementitious materials and reducing the water-binder ratio. Such concrete mix ratios will result in high viscosity and poor fluidity of the concrete, and the pumping performance of the concrete is poor, seriously affecting the construction efficiency and greatly limiting the popularization and application of high-strength and ultra-high-strength concrete.

[0003] In related technologies, to improve the fluidity and pumping performance of high-strength concrete, methods such as increasing the dosage of water reducer, adding air-entraining agent, and optimizing the particle gradation are mainly adopted. However, when the dosage of general polycarboxylate-based water reducers is too large, adverse phenomena such as segregation and bleeding of concrete will occur; the viscosity-reducing effect of adding air-entraining agent is limited, and too many air bubbles will have an adverse effect on the strength. Therefore, how to reduce the flow viscosity of high-strength concrete is of great significance. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide a concrete polycarboxylate water reducer and a preparation method thereof, which have a suitable ratio of carboxyl groups to side chains and can reliably reduce the flow viscosity of concrete.

[0005] In a first aspect, the present invention provides a concrete polycarboxylate water reducer, wherein the precursor of the polycarboxylate water reducer includes vinyl polyoxyethylene ether, or a mixture of vinyl polyoxyethylene ether and an esterified product of vinyl polyoxyethylene ether and fluorocarboxylic acid; the mass ratio of vinyl polyoxyethylene ether to the esterified product of vinyl polyoxyethylene ether and fluorocarboxylic acid is (3 - 5):1;

[0006] The ratio of the number of carboxyl groups to the number of side chains in the polycarboxylate water reducer is 2.5 - 3.5.

[0007] As an optional solution, the weight-average molecular weight of vinyl polyoxyethylene ether is 3000 - 6000.

[0008] As an optional solution, the weight-average molecular weight of the esterified product of vinyl polyoxyethylene ether and fluorocarboxylic acid is 3100 - 6300.

[0009] As an optional solution, the fluorocarboxylic acid includes trifluoroacetic acid and / or heptafluorobutyric acid.

[0010] As an alternative, the polycarboxylate water reducer is obtained by polymerizing the precursor under the action of acrylic acid, a chain initiator, an oxidizing agent, and a reducing agent, wherein the molecular ratio of acrylic acid to the precursor is 2.8 - 3.5;

[0011] As an alternative, the chain initiator includes at least one of mercaptopropionic acid and sodium hypophosphite; the oxidizing agent includes hydrogen peroxide, and the reducing agent includes ascorbic acid.

[0012] In a second aspect, the present invention provides a method for preparing the concrete polycarboxylate water reducer of the first aspect, which specifically includes the following steps:

[0013] Provide a precursor of the polycarboxylate water reducer;

[0014] Perform a polymerization reaction on the precursor to obtain the polycarboxylate water reducer.

[0015] As an alternative, performing a polymerization reaction on the precursor to obtain the polycarboxylate water reducer specifically includes:

[0016] Put the oxidizing agent into the precursor to obtain a base material;

[0017] Add acrylic acid to water and mix to obtain a first mixture;

[0018] Add the reducing agent and the chain transfer agent to water and mix to obtain a second mixture;

[0019] After adding the first mixture and the second mixture to the base material, continue the polymerization reaction to obtain the polycarboxylate water reducer;

[0020] Among them, the mass of the chain transfer agent is 0.5% - 1.5% of the mass of the precursor, the mass of the reducing agent is 0.1% - 0.3% of the precursor, and the mass of the oxidizing agent is 0.3% - 0.5% of the mass of the precursor.

[0021] As an alternative, during the process of adding the first mixture and the second mixture to the base material and then continuing the polymerization reaction to obtain the polycarboxylate water reducer, the reaction temperature of the whole process is 20°C - 35°C, and the time for continuing the polymerization reaction is 30 min - 50 min.

[0022] As an alternative, adding the first mixture and the second mixture to the base material includes:

[0023] Drop the first mixture and the second mixture into the base material simultaneously; among them, the dropping time of the second mixture is 15 min - 20 min longer than that of the first mixture, and the dropping time of the first mixture is 50 min - 120 min.

[0024] As an alternative, after adding the first mixture and the second mixture to the base material and continuing the polymerization reaction, the method further includes:

[0025] Add caustic solution to react and add water to prepare a 40%-50% mixture to obtain a concrete alkali water reducer.

[0026] The concrete polycarboxylate water reducer provided by the present invention selects vinyl polyoxyethylene ether, or an esterified product of vinyl polyoxyethylene ether and vinyl polyoxyethylene ether and fluorocarboxylic acid as the precursor of the polycarboxylate water reducer, and the mass ratio of vinyl polyoxyethylene ether to the esterified product of vinyl polyoxyethylene ether and fluorocarboxylic acid is (3-5):1. In the macromonomer structure of the esterified product of polyoxyethylene ether and fluorocarboxylic acid, the hydrophobic end groups will approach the main chain, fold, and change the density of the polycarboxylate side chain, so that the carboxyl group and the side chain can have a suitable ratio, and the side chain length and rigidity of the polycarboxylate are suitable, thereby effectively reducing the flow viscosity of the concrete, improving the concrete performance, and ensuring the construction efficiency. Description of the Drawings

[0027] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objects, and advantages of the present application will become more apparent:

[0028] Figure 1 It is an adsorption model of polycarboxylate on cement particles. Detailed Embodiments

[0029] The present application will be further described in detail below in conjunction with the embodiments. It can be understood that the specific embodiments described herein are only used to explain the related invention, rather than limiting the invention. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the embodiments.

[0030] For polycarboxylate used as a water reducer variety, in order to make polycarboxylate adsorb quickly and have a high water reduction rate during use, the ratio of carboxyl groups to side chains in the structure of the vast majority of polycarboxylate varieties is in the range of 4 to 5.5. The weight average molecular weight of the terminal alkenyl polyoxyethylene ether used for polymerization is generally selected to be 3000. In the actual use process, it is found that when the polycarboxylate obtained by using a terminal alkenyl polyoxyethylene ether with a weight average molecular weight greater than 3000 and having a relatively large number of carboxyl groups, the adsorption is relatively slow, the workability is poor, and the bleeding phenomenon is serious.

[0031] To solve the viscosity problem of high-strength concrete, some researchers believe that polycarboxylic acids with relatively short side chains and relatively short main chains are beneficial to improving the fluidity of concrete. The theory behind this view is that polycarboxylic acids with short side chains can reduce the thickness of the adsorbed water layer of polycarboxylic acids on the surface of cement particles, increasing the amount of freely flowing water, thus increasing the fluidity of concrete. Second, introducing some hydrophobic monomers into the polycarboxylic acid structure and reducing the HLB value of the polycarboxylic acid can effectively reduce the viscosity of concrete. However, in practical applications, the effect of polycarboxylic acids prepared using the above viewpoints is extremely limited.

[0032] Based on the above problems, embodiments of the present application provide a concrete polycarboxylate water reducer. The precursor of the polycarboxylate water reducer includes vinyl polyoxyethylene ether, or a mixture of vinyl polyoxyethylene ether and an ester of vinyl polyoxyethylene ether and fluorocarboxylic acid; the mass ratio of vinyl polyoxyethylene ether to the ester of vinyl polyoxyethylene ether and fluorocarboxylic acid is (3 - 5):1.

[0033] The ratio of carboxyl groups to the number of side chains in the polycarboxylate water reducer is 2.5 - 3.5.

[0034] It can be understood that to reduce the flow viscosity of concrete, it is mainly to reduce the interaction force between cement particles. The force between cement particles mainly comes from the cement hydration process, where some particles carry positive charges and some carry negative charges, and the force between the charges is the main factor affecting the flow viscosity of concrete. For polycarboxylate water reducers, the side chains in the structure should have an appropriate density, rigidity, and length. Such a structure is conducive to increasing the distance between cement particles with different charges, thereby reducing the force between the charges, which is beneficial to reducing viscosity and increasing fluidity. Another requirement for the polycarboxylic acid structure is that the main chain of the polycarboxylic acid should not be too long, as an overly long main chain will form a large flocculent structure, which is not conducive to the fluidity of concrete.

[0035] As Figure 1 shown in the adsorption model of the embodiments of the present application on cement particles, it can be seen from the figure that polycarboxylic acids can increase the distance between cement particles, thereby facilitating the reduction of the charge force and the viscosity.

[0036] The concrete polycarboxylate water reducer of the embodiments of the present application can effectively reduce the flow viscosity of concrete by, on the one hand, increasing the ratio of side chains to carboxyl groups, combined with a reasonable acid-ether ratio and the weight-average molecular weight of the polycarboxylic acid, making the side chain length of the polycarboxylic acid moderate and the rigidity moderate; on the other hand, folding the long side chains.

[0037] Among them, a fluorocarboxylic acid ester is introduced at the other end of the vinyl polyoxyethylene ether, making the end group have strong hydrophobicity. In solution, the hydrophobic end group will move closer to the main chain, thus folding.

[0038] Exemplarily, the terminal alkenyl polyethylene glycol ether-fluorinated carboxylic acid ester monomer has the following structure and reaction:

[0039]

[0040] The vinyl polyethylene glycol ether reacts with the fluorinated carboxylic acid through an esterification reaction to obtain a vinyl polyethylene glycol ether fluorinated carboxylic acid ester macromonomer, simply referred to as a terminal alkenyl fluorinated macromonomer.

[0041] Among them, the mass ratio of the vinyl polyoxyethylene ether to the esterification product of the vinyl polyoxyethylene ether and the fluorinated carboxylic acid can be but is not limited to 3:1, 4:1, or 5:1, etc. In this embodiment, the mass ratio of the vinyl polyoxyethylene ether to the esterification product of the vinyl polyoxyethylene ether and the fluorinated carboxylic acid is selected to have a lower ratio of carboxyl groups to side chains, which is conducive to regulating the ratio of carboxyl groups to side chains, enabling the polycarboxylic acid to have a high side chain density and a long side chain length, thus facilitating the reduction of the viscosity of the concrete.

[0042] Among them, the ratio of the number of carboxyl groups to side chains in the polycarboxylate superplasticizer can be but is not limited to 2.5, 3, or 3.5, which is conducive to the polycarboxylate superplasticizer having a suitable side chain density and rigidity, thus facilitating the reduction of the flow viscosity of the concrete.

[0043] The concrete polycarboxylate superplasticizer in the embodiment of the present application solves the problem of the relatively high viscosity of the existing concrete. The concrete polycarboxylate superplasticizer in the embodiment of the present application selects vinyl polyoxyethylene ether, or a combination of vinyl polyoxyethylene ether and the esterification product of vinyl polyoxyethylene ether and fluorinated carboxylic acid as the precursor of the polycarboxylate superplasticizer, and the mass ratio of vinyl polyoxyethylene ether to the esterification product of vinyl polyoxyethylene ether and fluorinated carboxylic acid is (3 - 5):1. In the macromonomer structure of the esterification product of polyoxyethylene ether and fluorinated carboxylic acid, the hydrophobic end groups will approach the main chain and fold, changing the side chain density of the polycarboxylic acid, thereby enabling a suitable ratio of carboxyl groups to side chains, and making the side chain length and rigidity of the polycarboxylic acid suitable. Moreover, when the macromolecules of the polycarboxylic acid adsorb on the surface of cement particles, the distance between two differently charged particles will be increased as much as possible, thereby reducing the action of the Coulomb force, and further effectively reducing the flow viscosity of the concrete, improving the concrete performance, and ensuring the construction efficiency.

[0044] As a feasible method, the weight average molecular weight of the vinyl polyoxyethylene ether is 3000 - 6000.

[0045] In this embodiment, the weight average molecular weight of the vinyl polyoxyethylene ether is conducive to ensuring that the polycarboxylate superplasticizer has suitable adsorption properties and workability.

[0046] As a feasible method, the weight average molecular weight of the esterification product of vinyl polyoxyethylene ether and fluorinated carboxylic acid is 3100 - 6300.

[0047] In this embodiment, the weight-average molecular weight of the esterified product of vinyl polyoxyethylene ether and fluorinated carboxylic acid can adjust the side chain length of the polycarboxylate superplasticizer, which is beneficial to improving the appropriate adsorption of the polycarboxylate superplasticizer, thereby making the workability of the concrete better.

[0048] In a preferred embodiment, the fluorinated carboxylic acid includes trifluoroacetic acid and / or heptafluorobutyric acid.

[0049] In some embodiments, the polycarboxylate superplasticizer is obtained by polymerizing a precursor under the action of acrylic acid, a chain initiator, an oxidizing agent, and a reducing agent. Among them, the molecular ratio of acrylic acid to the precursor is 2.8 - 3.5;

[0050] Among them, acrylic acid can be used to regulate the number of carboxyl groups in the polycarboxylate superplasticizer; the chain initiator is beneficial to the polymerization of the precursor and can also increase the side chain density; the oxidizing agent and the reducing agent form a redox system, which further promotes the polymerization of the precursor under the action of the chain initiator, making the ratio of side chains to carboxyl groups in the polycarboxylic acid appropriate.

[0051] Specifically, the molecular ratio of acrylic acid to the precursor can be but is not limited to 2.8, 3, 3.2, 3.3, or 3.5, etc.

[0052] The molecular ratio of acrylic acid to the precursor in this embodiment is beneficial to ensuring an appropriate ratio of carboxyl groups to side chains in the polycarboxylic acid, thereby facilitating the expansion of the distance between cement ions with different charges, reducing the force of the charges, and further being beneficial to reducing the viscosity and increasing the fluidity.

[0053] In some embodiments, the chain initiator includes at least one of mercaptopropionic acid and sodium hypophosphite; the oxidizing agent includes hydrogen peroxide, and the reducing agent includes ascorbic acid.

[0054] The chain initiator, oxidizing agent, and reducing agent in this embodiment act synergistically to enable the reliable polymerization of the precursor, thereby ensuring an appropriate ratio of carboxyl groups to side chains in the polycarboxylate superplasticizer, an appropriate side chain length, and a not-too-long main chain, which is beneficial to reducing the viscosity of the concrete, increasing the fluidity, and avoiding flocculation.

[0055] In summary, in the embodiments of the present application, by selecting vinyl polyoxyethylene ether, or vinyl polyoxyethylene ether and the esterified product of vinyl polyoxyethylene ether and fluorinated carboxylic acid as the precursor of the polycarboxylate superplasticizer, and the mass ratio of vinyl polyoxyethylene ether to the esterified product of vinyl polyoxyethylene ether and fluorinated carboxylic acid is (3 - 5):1. In the macromonomer structure of the esterified product of polyoxyethylene ether and fluorinated carboxylic acid, the hydrophobic end groups will approach the main chain, fold, and change the side chain density of the polycarboxylic acid, so that an appropriate ratio of carboxyl groups to side chains can be obtained, and the side chain length and rigidity of the polycarboxylic acid are suitable. Furthermore, it can effectively reduce the flow viscosity of the concrete, improve the concrete performance, and ensure the construction efficiency;

[0056] Moreover, under the action of acrylic acid, initiator, reducing agent and oxidizing agent, reliable polymerization of the precursor can be ensured, so that the polycarboxylic acid has a suitable carboxyl group and side chain ratio, and can reliably reduce the viscosity of concrete and increase fluidity.

[0057] In a second aspect, the present invention provides a method for preparing a polycarboxylic acid water reducer for concrete according to the first aspect, specifically including the following steps:

[0058] Step S1: Provide a precursor of the polycarboxylic acid water reducer;

[0059] Step S2: Subject the precursor to a polymerization reaction to obtain a polycarboxylic acid water reducer.

[0060] It can be understood that the precursor of the polycarboxylic acid water reducer can be vinyl polyoxyethylene ether, or an esterification product of vinyl polyoxyethylene ether and vinyl polyoxyethylene ether with a fluorocarboxylic acid; among them, vinyl polyoxyethylene ether can be a directly purchased finished product, and of course it can also be synthesized by chemical synthesis; similarly, the esterification product of vinyl polyoxyethylene ether and fluorocarboxylic acid can be obtained by esterification of vinyl polyoxyethylene ether and fluorocarboxylic acid;

[0061] It can also be understood that the polymerization method of the above precursor can be aqueous solution radical polymerization. For example, two macromonomers of vinyl polyoxyethylene ether and an esterification product of vinyl polyoxyethylene ether and fluorocarboxylic acid and deionized water are put into a reaction kettle according to a set mass ratio as the precursor base material, and the above precursor is polymerized under the action of an initiator, an oxidizing agent and a reducing agent to obtain a polycarboxylic acid water reducer.

[0062] In a preferred embodiment, step S2: Subject the precursor to a polymerization reaction to obtain a polycarboxylic acid water reducer, specifically including:

[0063] Put the oxidizing agent into the precursor to obtain a base material;

[0064] Add acrylic acid to water and mix to obtain a first mixture;

[0065] Add the reducing agent and the chain transfer agent to water and mix to obtain a second mixture;

[0066] After adding the first mixture and the second mixture to the base material, continue the polymerization reaction to obtain a polycarboxylic acid water reducer;

[0067] Among them, the mass of the chain transfer agent is 0.5%-1.5% of the mass of the precursor, the mass of the reducing agent is 0.1%-0.3% of the precursor, and the mass of the oxidizing agent is 0.3%-0.5% of the mass of the precursor.

[0068] It should be noted that the first mixture and the second mixture can be added to the base material in any way, such as but not limited to direct addition, dropping or spraying, etc.; the first mixture and the second mixture can be added simultaneously, or alternately, or the first mixture can be added first and then the second mixture, etc. The embodiments of the present application do not make specific limitations on the above, as long as the reliable polymerization of the above precursors can be ensured.

[0069] Specifically, the mass of the chain transfer agent can be but not limited to 0.5%, 0.7%, 1.0%, 1.2% or 1.5% of the mass of the precursor. When the mass of the chain transfer agent is less than 0.5% of the mass of the precursor, it cannot promote the polymerization of the precursor and cannot form a reliable side chain; when the mass of the chain transfer agent is higher than 1.5% of the mass of the precursor, the side chain of the reliable polycarboxylic acid is too long to form a main chain, which will cause problems such as delamination and sedimentation of the concrete; the mass of the reducing agent can be but not limited to 0.1%, 0.15%, 0.2%, 0.25% or 0.3% of the mass of the precursor. When the mass of the reducing agent is less than 0.1% of the mass of the precursor, the amount of the reducing agent is too small to ensure the reliable occurrence of the polymerization reaction; when the mass of the reducing agent is higher than 0.3% of the mass of the precursor, the amount of the reducing agent is too large, causing the entire system to be unbalanced and unable to reliably form a redox system; the mass of the oxidizing agent can be but not limited to 0.3%, 0.35%, 0.4%, 0.45% or 0.5% of the mass of the precursor, etc. When the mass of the oxidizing agent is less than 0.3%, the mass of the oxidizing agent is too low to ensure the reliable oxidation of the precursor. When the mass of the oxidizing agent is higher than 0.5%, the mass of the oxidizing agent is too large, causing the entire system to be unbalanced and unable to reliably form a redox system.

[0070] In this embodiment, the addition order of each raw material is beneficial to ensuring the reliable polymerization of the precursor, so that the obtained polycarboxylic acid has appropriate carboxyl and side chain densities, which is beneficial to reducing the flow viscosity of the concrete.

[0071] In some embodiments, after adding the first mixture and the second mixture to the base material and continuing the polymerization reaction to obtain a polycarboxylic acid water reducer, the reaction temperature of the whole process is 20°C - 35°C, and the time for continuing the polymerization reaction is 30 min - 50 min.

[0072] Specifically, the reaction temperature of the whole process can be but not limited to 20°C, 25°C, 30°C or 35°C. When the reaction temperature is lower than 20°C, the reaction temperature is too low, resulting in too slow a polymerization reaction rate; when the reaction temperature is higher than 35°C, the reaction temperature is too high, which may damage the organic structure and at the same time cause a fast polymerization rate, making it impossible to control the polymerization degree.

[0073] After adding the first mixture and the second mixture, the time for continuing the reaction can be, but is not limited to, 30 min, 35 min, 40 min, 45 min, or 50 min, etc. When the time for continuing the polymerization reaction is less than 30 min, the polymerization effect of the precursor is poor. When the time for continuing the polymerization reaction is greater than 50 min, the overall reaction time is too long, reducing the production and processing efficiency.

[0074] In a preferred embodiment, adding the first mixture and the second mixture to the base material includes:

[0075] Adding the first mixture and the second mixture to the base material dropwise simultaneously; wherein, the dropping time of the second mixture is 15 min - 20 min longer than that of the first mixture, and the dropping time of the first mixture is 50 min - 120 min.

[0076] In this embodiment, the first mixture and the second mixture are added dropwise simultaneously, and the dropping time of the second mixture is longer. This is beneficial for further neutralizing the oxidant, avoiding the product obtained by polymerization from being oxidized, and thus obtaining a polycarboxylic acid with a suitable ratio of carboxyl groups and side chains.

[0077] In some embodiments, after adding the first mixture and the second mixture to the base material and continuing the polymerization reaction, the method further includes:

[0078] Adding an alkali solution to react and adding water to prepare a 40% - 50% mixed solution to obtain a concrete alkali water reducer.

[0079] Among them, the alkali solution can be, but is not limited to, solutions such as sodium hydroxide and potassium hydroxide. The main function of the alkali solution is to neutralize the acid solution in the entire reaction system and adjust the pH value of the entire system.

[0080] In this embodiment, after neutralizing by adding an alkali solution and then adding water to make a solution with a solid content of 40% - 50%, it is beneficial to obtain a polycarboxylic acid water reducer that can reduce the flow viscosity of concrete.

[0081] In summary, the preparation method of the embodiment of the present application is simple to operate, has strong controllability, and can obtain a polycarboxylic acid water reducer with a suitable ratio of the number of carboxyl groups and side chains, thereby being able to reliably reduce the flow viscosity of concrete and improve the construction efficiency.

[0082] The present invention will be described below through specific embodiments. It should be noted that the following specific embodiments are only for illustrative purposes and do not limit the scope of the present invention in any way. Additionally, unless otherwise specified, the methods without specifically recorded conditions or steps are conventional methods, and the reagents and materials used can be obtained from commercial channels.

[0083] Example 1

[0084] 360 g (0.12 mol) of vinyl polyoxyethylene ether macromonomer with a weight-average molecular weight of 3000 was put into a reaction kettle, 300 g of water was added, and then 2.0 g of oxidant hydrogen peroxide was put in, and they were stirred and mixed evenly as the bottom material;

[0085] 26 g (0.3611 mol) of acrylic acid was weighed and put into bottle A, and then 50 g of deionized water was added and mixed evenly as material A;

[0086] 0.50 g of reducing agent VC, 50 g of water, 2.2 g of mercaptopropionic acid and 3 g of sodium hypophosphite were respectively weighed and put into bottle B as material B;

[0087] The temperature of the bottom material in the reaction kettle was controlled at 30 °C, and material A and material B were added dropwise simultaneously. The dropping time of material A was controlled at 60 minutes; the dropping time of material B was controlled at 75 minutes. The temperature during the dropping process was kept not higher than 35 °C. After the dropping was completed, stirring reaction was maintained for 40 minutes, and then 15 g of 30% NaOH solution was added for neutralization, and water was added to make the solid content of the solution 40%, obtaining polycarboxylate superplasticizer PCE-Z1. Among them, the ratio of carboxyl group to side chain in the polycarboxylic acid was 3.0.

[0088] Example 2

[0089] 300 g (0.1 mol) of vinyl polyoxyethylene ether macromonomer with a weight-average molecular weight of 3000 and 60 g (0.00968 mol) of esterified product of vinyl polyoxyethylene ether with fluorocarboxylic acid with a weight-average molecular weight of 6200 were put into a reaction kettle, 300 g of water was added, and then 2.0 g of oxidant hydrogen peroxide was put in, and they were stirred and mixed evenly as the bottom material;

[0090] 24 g (0.3333 mol) of acrylic acid was weighed and put into bottle A, and then 50 g of deionized water was added as material A;

[0091] 0.50 g of reducing agent VC, 50 g of water, 2.1 g of mercaptopropionic acid and 2.5 g of sodium hypophosphite were respectively weighed and put into bottle B as material B;

[0092] The temperature of the bottom material in the reaction kettle was controlled at 30 °C, and material A and material B were added dropwise simultaneously. The dropping time of material A was 60 minutes; the dropping time of material B was 75 minutes. The temperature during the dropping process was kept not higher than 35 °C. After the dropping was completed, stirring reaction was maintained for 40 minutes, and then 15 g of 30% NaOH solution was added for neutralization, and water was added to make the solid content of the solution 40%, obtaining polycarboxylate superplasticizer PCE-Z2. Among them, the ratio of carboxyl group to side chain in the polycarboxylic acid was 3.04.

[0093] Example 3

[0094] 270 g (0.045 mol) of vinyl polyoxyethylene ether macromonomer with a weight-average molecular weight of 6000 and 90 g (0.0145 mol) of the esterified product of vinyl polyoxyethylene ether with a weight-average molecular weight of 6200 and a fluorocarboxylic acid were put into a reaction kettle, 300 g of water was added, and 2.0 g of oxidant hydrogen peroxide was added as the bottom material;

[0095] 14.4 g (0.2 mol) of acrylic acid was weighed and put into bottle A, and then 50 g of deionized water was added as material A;

[0096] 0.50 g of reducing agent VC, 50 g of water, 1.8 g of mercaptopropionic acid, and 3 g of sodium hypophosphite were respectively weighed and put into bottle B as material B;

[0097] The temperature of the bottom material in the reaction kettle was controlled not to exceed 30 °C. Then, material A and material B were simultaneously added dropwise. The dropping time of material A was 60 minutes; the dropping time of material B was 75 minutes. The temperature during the dropping process was kept not to exceed 35 °C. After the dropping was completed, stirring reaction was maintained for 40 minutes, and then 15 g of 30% NaOH solution was added for neutralization, and water was added to make the solid content of the solution 40% to obtain polycarboxylate superplasticizer PCE-Z3; among them, the ratio of carboxyl groups to side chains in the polycarboxylic acid was 3.36.

[0098] Example 4

[0099] 270 g (0.06 mol) of vinyl polyoxyethylene ether macromonomer with a weight-average molecular weight of 4500 and 90 g (0.029 mol) of the esterified product of vinyl polyoxyethylene ether with a weight-average molecular weight of 3100 and a fluorocarboxylic acid were put into a reaction kettle, 300 g of water was added, and 2.0 g of oxidant hydrogen peroxide was added as the bottom material;

[0100] 18 g (0.25 mol) of acrylic acid was weighed and put into bottle A, and then 50 g of deionized water was added as material A;

[0101] 0.50 g of reducing agent VC, 50 g of water, 2.5 g of mercaptopropionic acid, and 2.5 g of sodium hypophosphite were respectively weighed and put into bottle B as material B;

[0102] The temperature of the bottom material in the reaction kettle was controlled not to exceed 30 °C. Then, material A and material B were simultaneously added dropwise. The dropping time of material A was 60 minutes; the dropping time of material B was 75 minutes. The temperature during the dropping process was kept not to exceed 35 °C. After the dropping was completed, stirring reaction was maintained for 40 minutes, and then 15 g of 30% NaOH solution was added for neutralization, and water was added to make the solid content of the solution 40% to obtain polycarboxylate superplasticizer PCE-Z4; among them, the ratio of carboxyl groups to side chains in the polycarboxylic acid was 2.8.

[0103] Comparative sample 1 was a commercially available viscosity-reducing polycarboxylate superplasticizer;

[0104] The comparative sample 2 is a common polycarboxylate water reducer.

[0105] The following concrete experiments were carried out on the polycarboxylate water reducers of the above embodiments:

[0106] The mix proportion of the concrete is shown in Table 1;

[0107] Table 1 Concrete Mix Proportion

[0108]

[0109] Among them, in Table 1, the admixture is the water reducer of Examples 1-4 and Comparative Samples 1-2. Among them, the dosage of the admixture in the concrete is 1%, and when used, the admixture is diluted with water to a solid content of 20%.

[0110] The comparison results of the polycarboxylate water reducers of Examples 1-4 of the present application and the concrete of the comparative samples are shown in Tables 2, 3, 4 and 5:

[0111] Table 2 Test Results of Concrete with Strength Grade C80

[0112]

[0113]

[0114] Table 3 Test Results of Concrete with Strength Grade C100

[0115]

[0116]

[0117] Table 4 is the test result of the compressive strength of concrete with strength grade C80

[0118]

[0119]

[0120] Table 5 is the test result of the compressive strength of concrete with strength grade C100

[0121]

[0122] According to the results in Tables 2-5, it can be seen that compared with the comparative samples, the polycarboxylate water reducers of Examples 1-4 of the present application can make the concrete have good workability, soft material, easy to turn over, and better compressive strength. Further, it shows that the polycarboxylate water reducers of the examples of the present application can reliably reduce the flow viscosity of the concrete, thereby ensuring good workability of the concrete, soft material, easy to turn over, and thus improving the compressive strength of the concrete.

[0123] The above description is only a preferred embodiment of the present application and an explanation of the technical principles applied. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the technical solutions formed by mutually replacing the above features with the technical features (but not limited to) disclosed in the present application that have similar functions.

Claims

1. Concrete polycarboxylate water reducer, characterized in that: The precursor of the polycarboxylate water-reducing agent includes vinyl polyoxyethylene ether, or vinyl polyoxyethylene ether and an ester of vinyl polyoxyethylene ether and fluorocarboxylic acid; the mass ratio of the vinyl polyoxyethylene ether to the ester of the vinyl polyoxyethylene ether and fluorocarboxylic acid is (3-5):1; The ratio of the number of carboxyl groups to the number of side chains in the polycarboxylate water-reducing agent is 2.5-3.

5.

2. The concrete polycarboxylate water-reducing agent according to claim 1, characterized in that: The weight average molecular weight of the vinyl polyoxyethylene ether is 3000-6000.

3. The concrete polycarboxylate water reducer according to claim 1, characterized in that: The weight average molecular weight of the ester of vinyl polyoxyethylene ether and fluorocarboxylic acid is 3100-6300.

4. The concrete polycarboxylate water-reducing agent according to claim 1, characterized in that: The fluorinated carboxylic acid includes trifluoroacetic acid and / or heptafluorobutyric acid.

5. The concrete polycarboxylate water-reducing agent according to claim 1, characterized in that: The polycarboxylate water reducer is obtained by polymerizing the precursor under the action of acrylic acid, a chain initiator, an oxidant and a reducing agent, wherein the molecular ratio of the acrylic acid to the precursor is 2.8-3.5; Preferably, the chain initiator comprises at least one of mercaptopropionic acid and sodium hypophosphite; the oxidizing agent comprises hydrogen peroxide, and the reducing agent comprises ascorbic acid.

6. A method for preparing the concrete polycarboxylate water-reducing agent according to any one of claims 1 to 5, characterized in that: The specific steps include: Providing a precursor of the polycarboxylate water-reducing agent; The precursor is subjected to polymerization reaction to obtain the polycarboxylate water-reducing agent.

7. The method according to claim 6, characterized in that The precursor is subjected to a polymerization reaction to obtain the polycarboxylate water-reducing agent, specifically comprising: Adding the oxidant into the precursor to obtain a base material; Adding the acrylic acid into water and mixing to obtain a first mixed material; Adding the reducing agent and the chain transfer agent into water and mixing them to obtain a second mixed material; After adding the first mixed material and the second mixed material to the base material, continuing the polymerization reaction to obtain the polycarboxylate water reducer; The mass of the chain transfer agent is 0.5%-1.5% of the mass of the precursor, the mass of the reducing agent is 0.1%-0.3% of the mass of the precursor, and the mass of the oxidant is 0.3%-0.5% of the mass of the precursor.

8. The method according to claim 7, characterized in that After adding the first mixed material and the second mixed material to the base material, the polymerization reaction is continued to obtain the polycarboxylate water reducer. The reaction temperature of the whole process is 20° C.-35° C., and the polymerization reaction time is 30 min-50 min.

9. The method according to claim 7, characterized in that: Adding the first mixed material and the second mixed material to the base material comprises: The first mixed material and the second mixed material are simultaneously added dropwise to the base material; wherein the adding time of the second mixed material is 15-20 minutes longer than the adding time of the first mixed material, and the adding time of the first mixed material is 50-120 minutes.

10. The method according to claim 7, characterized in that After adding the first mixed material and the second mixed material to the base material and continuing the polymerization reaction, the method further comprises: Alkali solution is added for reaction and water is added to prepare a 40%-50% mixed solution to obtain the concrete alkali water agent.

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