Ion-tolerant water reducing agent as well as preparation method and application thereof

Abstract

The invention provides an ion-tolerant water reducing agent as well as a preparation method and application thereof. The molecular structure of the ion-tolerant water reducing agent comprises a structural unit of starch polysaccharide or a starch polysaccharide derivative. The invention aims to solve the technical problem of how to prepare the ion-tolerant water reducing agent which has low ion sensitivity, so that the stability and solubility of a molecular structure of the water reducing agent in a complex ion environment are improved, the dispersing performance of the water reducing agent in the complex ion environment is improved, and the service life of the water reducing agent in the complex ion environment is prolonged. Gel material particles can be well dispersed in a complex ion environment, and large-scale application of low-carbon concrete is further promoted.

Description

Technical Field

[0001] The invention relates to the technical field of concrete chemical admixtures, and in particular to an ion-tolerant water reducing agent and a preparation method and application thereof. Background Art

[0002] With the proposal of the "dual carbon" goal, all industries are seeking and accelerating green and low-carbon transformation. For the concrete industry, which plays a huge role in infrastructure construction, green and low-carbon is also the only way for future development.

[0003] As a common cement concrete admixture, water reducer can significantly reduce the water consumption of concrete while maintaining the workability of cement concrete. Common water reducers include sulfonated lignin water reducer, naphthalene water reducer and polycarboxylic acid high-performance water reducer. Lignin water reducer and naphthalene water reducer polymers present linear structures, and mainly achieve the dispersion of cement particles through the electrostatic repulsion generated by the main chain anions, but their water reduction rate is limited. Polycarboxylic acid water reducer, as a "third generation" water reducer, has a comb-shaped structure. In addition to the electrostatic repulsion of the main chain, its side chain can also provide steric hindrance, thereby significantly improving its water reduction rate. However, polycarboxylic acid water reducer is very "sensitive" to the chemical environment of the cement paste solution and the generated hydration products.

[0004] The pore solution of traditional concrete is mainly composed of calcium ions, hydroxide ions, potassium ions, etc.; compared with traditional concrete, the ionic chemical environment of cement paste solution of alkali-activated concrete, carbon capture concrete and other low-carbon concrete is more complex, and its pore solution is mainly composed of carbonate ions, bicarbonate ions and hydroxide ions; the change of ion types and hydration products greatly affects the solubility of water reducers and their interaction with cementitious materials, weakens the electrostatic repulsion and steric hindrance effect of water reducers, etc., and significantly reduces the dispersion effect of various water reducers in the existing technology, which makes it difficult for low-carbon concrete to meet construction requirements, greatly limiting the large-scale application of low-carbon concrete. Summary of the invention

[0005] The main purpose of the present invention is to provide an ion-tolerant water reducer and a preparation method and application thereof. The technical problem to be solved is how to prepare an ion-tolerant water reducer with low ion sensitivity, thereby improving the stability and solubility of the molecular structure of the water reducer in a complex ionic environment, improving the dispersion performance of the water reducer in a complex ionic environment, achieving good dispersion of cementitious material particles in a complex ionic environment, and further promoting the large-scale application of low-carbon concrete.

[0006] The purpose of the present invention and the technical problem to be solved are achieved by adopting the following technical solutions: According to the ion-tolerant water reducer proposed in the present invention, its molecular structure includes the structural unit of starch polysaccharide or starch polysaccharide derivative.

[0007] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

[0008] Preferably, in the aforementioned ion-tolerant water reducer, the mass proportion of the structural units of the starch polysaccharide or starch polysaccharide derivative in the ion-tolerant water reducer is ≥ 65%.

[0009] Preferably, in the aforementioned ion-tolerant water reducer, the starch polysaccharide derivative is β-cyclodextrin.

[0010] Preferably, the aforementioned ion-tolerant water reducer, wherein the ion-tolerant water reducer has a linear structural unit and / or a multi-arm structural unit; the linear structural unit is a linear structure with β-cyclodextrin or starch polysaccharide as a side chain; the multi-arm structural unit is a multi-arm structure with β-cyclodextrin or starch polysaccharide as the center.

[0011] Preferably, the aforementioned ion-tolerant water reducer has a molecular weight of 5000 to 100000 g / mol.

[0012] The purpose of the present invention and the technical problem to be solved are achieved by adopting the following technical solutions. According to the preparation method of an ion-tolerant water reducer proposed in the present invention, it comprises the following steps:

[0013] S61: uniformly mixing the first reactant with water to obtain a first reactant aqueous solution; the first reactant comprises at least one of a starch polysaccharide containing an olefin functional group and a β-cyclodextrin containing an olefin functional group; the starch polysaccharide containing an olefin functional group has a molecular weight of 1000 to 3000 g / mol;

[0014] S62 adds an initiator to the aqueous solution of the first reactant, and stirs uniformly to obtain an initiator solution;

[0015] S63, adding an unsaturated acid solution and a chain transfer agent solution to the initiator solution respectively, and keeping the temperature at the reaction temperature to obtain a reaction solution; based on the sum of the mass of the first reactant, the initiator, the unsaturated acid and the chain transfer agent being 100%, the total mass percentage of the starch polysaccharide containing an olefin functional group and / or the β-cyclodextrin containing an olefin functional group is ≥ 65%;

[0016] S64 The reaction solution is cooled to room temperature, and its pH value is adjusted to be neutral to obtain an ion-tolerant water-reducing agent solution.

[0017] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

[0018] Preferably, in the aforementioned preparation method, the starch polysaccharide containing olefin functional groups is selected from at least one of monoolefin functional starch polysaccharides, diolefin functional starch polysaccharides, pentaolefin functional starch polysaccharides, heptaolefin functional starch polysaccharides and N-olefin functional starch polysaccharides; wherein N is a natural number ≥10; and the β-cyclodextrin containing olefin functional groups is selected from at least one of monoolefin functional β-cyclodextrin, diolefin functional β-cyclodextrin, triolefin functional β-cyclodextrin, tetraolefin functional β-cyclodextrin and heptaolefin functional β-cyclodextrin.

[0019] Preferably, in the aforementioned preparation method, the first reactant also includes a polyether monomer; the polyether monomer is selected from at least one of propyl polyethylene glycol ether, 2-methylprop-2-enyl polyethylene glycol ether, 3-methylbut-3-allyl polyethylene glycol ether, vinyl polyethylene glycol ether and vinyloxybutyl polyethylene glycol ether; the unsaturated acid is selected from at least one of unsaturated carboxylic acid, unsaturated sulfonic acid and unsaturated phosphoric acid; the unsaturated carboxylic acid is selected from at least one of acrylic acid, methyl acrylate, ethyl propionate, methacrylic acid and hydroxyethyl acrylate; the unsaturated sulfonic acid is selected from at least one of sodium acrylic acid sulfonate, sodium vinyl sulfonate and sodium methacrylic acid; the unsaturated phosphate is selected from at least one of 2-methyl-2-acrylic acid-2-hydroxyethyl ester phosphate, alkyl acrylate phosphate, ethylene glycol methacrylate phosphate and methacryloyloxyethyl phosphate.

[0020] Preferably, in the aforementioned preparation method, the initiator is selected from at least one of azobisisobutyronitrile, potassium persulfate and hydrogen peroxide; and the chain transfer agent is selected from at least one of aromatic disulfide esters, aliphatic disulfide esters, trithiocarbonates and sulfonate esters.

[0021] The purpose of the present invention and the technical problem to be solved are achieved by adopting the following technical solutions: According to the present invention, an application of the above-mentioned ion-tolerant water reducer in the field of concrete admixtures is proposed.

[0022] By means of the above technical solution, the ion-tolerant water reducer and its preparation method and application proposed in the present invention have at least the following advantages:

[0023] The ion-tolerant water reducer and its preparation method and application proposed in the present invention introduce the structural units of starch polysaccharide or starch polysaccharide derivatives into the molecular structure of the water reducer, and use the structural units of starch polysaccharide or starch polysaccharide derivatives as the side chains and / or main chains of the water reducer, so that the rigidity of the water reducer polymer molecules can be improved, and the curling and winding of the molecular chains of the water reducer molecules in a strong ionic chemical environment can be prevented, thereby improving its dispersion effect; and the structural units of starch polysaccharide or starch polysaccharide derivatives are used as the side chains and / or main chains of the water reducer to provide steric hindrance effect and electrostatic adsorption effect for the water reducer molecules; on the one hand, the low ion sensitivity of the polysaccharide polymer is utilized to reduce the sensitivity of the water reducer to a strong ionic environment, thereby improving the water reducer. On the one hand, the solubility of water reducer molecules in complex ionic environments is improved; on the other hand, the molecular rigid structure of starch polysaccharides and their derivatives is used to prevent the phase separation phenomenon caused by agglomeration of water reducer molecules in a strong ionic environment, effectively regulating the agglomeration behavior of water reducer molecules, thereby improving the ion sensitivity of water reducer molecules; the water reducer of the present invention mostly exists in the form of a single molecule structure in a strong ionic environment, which is more conducive to adsorption on the surface of cementitious material particles, and therefore has better ion tolerance; from the above, it can be seen that the water reducer of the present invention can improve the stability and solubility of the molecular structure in a complex ionic environment, improve the dispersion performance of the water reducer in a complex ionic environment, and further promote the large-scale application of low-carbon concrete. After on-site field testing, the water reducer significantly improved the working performance of concrete in complex ionic environments such as carbon capture concrete and oligomer concrete.

[0024] Furthermore, the ion-tolerant green water reducer proposed in the present invention is suitable for complex ionic chemical environments, has a simple preparation method, and has a strong designability of molecular structure, which broadens the types and categories of molecular structures of polycarboxylic acid water reducers.

[0025] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail as follows. DETAILED DESCRIPTION

[0026] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of an ion-tolerant water reducer and its preparation method and application according to the present invention, its specific implementation method, structure, characteristics and effects in combination with the preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0027] The present invention provides an ion-tolerant water reducer, the molecular structure of which includes a starch polysaccharide or starch polysaccharide derivative structural unit. The water reducer is prepared and synthesized by using a raw material containing a starch polysaccharide or starch polysaccharide derivative structural unit and an unsaturated acid monomer through free radical polymerization technology.

[0028] Since polysaccharide polymers have low ion sensitivity, the present invention introduces structural units of starch polysaccharides or starch polysaccharide derivatives into the structure of the water reducer, so that the sensitivity of the water reducer to strong ion environments can be reduced, thereby improving the solubility of the water reducer in complex ion environments; at the same time, when the structural units of starch polysaccharides or starch polysaccharide derivatives exist as side chains / main chains of the water reducer, they can give the water reducer molecular rigidity, so that it can prevent the curling and entanglement of the molecular chains of the water reducer molecules in a strong ion chemical environment, thereby improving its dispersion effect; that is, it can prevent the phase separation phenomenon caused by agglomeration of the water reducer molecules in a strong ion environment, effectively regulate the agglomeration behavior of the water reducer molecules, and further improve the ion sensitivity of the water reducer molecules.

[0029] The present invention also provides a method for preparing an ion-tolerant water reducer, which comprises the following steps:

[0030] First, the main reaction raw materials are prepared into an aqueous solution, specifically, the first reactant is evenly mixed with water to obtain the first reactant aqueous solution.

[0031] In the above technical scheme, the first reactant is the key raw material for preparing the water reducer of the present invention. The first reactant includes at least one of a starch polysaccharide containing an olefin functional group and a β-cyclodextrin containing an olefin functional group, and then polymerizes it into a water reducer of the target structure through free radical polymerization. In order to ensure the solubility of the above raw materials in water and facilitate its introduction into the water reducer molecule at a higher ratio, the present invention preferably has a molecular weight of 1000 to 3000 g / mol for the starch polysaccharide containing an olefin functional group.

[0032] Through a large number of experimental studies, it was found that when the starch polysaccharide containing olefin functional groups is selected from at least one of monoolefin functional starch polysaccharide, diolefin functional starch polysaccharide, pentaolefin functional starch polysaccharide, heptaolefin functional starch polysaccharide and N-olefin functional starch polysaccharide; wherein N is a natural number ≥10; or, when the β-cyclodextrin containing olefin functional groups is selected from at least one of monoolefin functional β-cyclodextrin, diolefin functional β-cyclodextrin, triolefin functional β-cyclodextrin, tetraolefin functional β-cyclodextrin and heptaolefin functional β-cyclodextrin, the ion sensitivity of the prepared water reducer is particularly low.

[0033] The polymerization reaction of the present invention has relatively broad requirements on the reaction temperature. Generally, the reaction temperature can be set to 10°C to 70°C according to the solubility and activity of the first reactant; when water and the first reactant are added to the reactor, the temperature is controlled according to the preset process conditions.

[0034] In the prior art, the preparation of water reducers mainly uses polyether monomers as reactants, and the main reason is that polyether monomers are widely available and reasonably priced; therefore, in the technical solution of the present invention, on the premise that the ion sensitivity of the water reducer can meet the usage scenario, the first reactant may also include a portion of polyether monomers, thereby controlling the cost of the water reducer. In some specific embodiments of the present invention, at least one of allyl polyethylene glycol ether (APEG), 2-methylprop-2-enyl polyethylene glycol ether (HPEG), 3-methylbut-3-allyl polyethylene glycol ether (IPEG), vinyl polyethylene glycol ether (VPEG) and vinyloxybutyl polyethylene glycol ether (VBPEG).

[0035] The second step is to add an initiator to the aqueous solution of the first reactant, stir evenly, and obtain an initiator solution. The polymerization reaction of the present invention is a free radical polymerization. In this step, the initiator is selected from at least one of azobisisobutyronitrile, potassium persulfate and hydrogen peroxide, and its dosage can be flexibly designed according to the feed amount and reaction activity of the reaction raw materials; in some specific embodiments of the present invention, the dosage of the initiator is 0.5% to 5% of the monomer mass; the feeding speed of the initiator can be designed according to the conventional art, and the present invention does not specifically limit this.

[0036] The third step is to add a solution containing an unsaturated acid and a solution containing a chain transfer agent and a reducing agent to the initiator solution; after the above raw materials are added, the reaction system is reacted at the process design temperature for 1 to 2 hours to terminate the reaction and obtain a reaction solution. The reducing agent in this step is optional but not necessary, such as no reducing agent is added in Example 2 and Example 3.

[0037] In the above technical scheme, the unsaturated acid is a monomer used for polymerization reaction with the first reactant. In some specific embodiments of the present invention, according to the design of the molecular structure of the water reducer, the unsaturated acid can be at least one selected from unsaturated carboxylic acid, unsaturated sulfonic acid and unsaturated phosphoric acid; the unsaturated carboxylic acid is selected from at least one of acrylic acid, methyl acrylate, ethyl propionate, methacrylic acid and hydroxyethyl acrylate; the unsaturated sulfonic acid is selected from at least one of sodium acrylic acid sulfonate, sodium vinyl sulfonate and sodium methacrylic acid; the unsaturated phosphate is selected from at least one of 2-methyl-2-acrylic acid-2-hydroxyethyl ester phosphate, alkyl acrylate phosphate, ethylene glycol methacrylate phosphate and methacryloyloxyethyl phosphate. In order to facilitate the addition of monomers, these unsaturated acids can be prepared in advance into a solution state, and the mass is converted during measurement, and the mass of the effective substance in the solution is calculated. The feeding rate of the unsaturated acid can be adjusted according to the activity of the raw material, and is generally controlled to be added within 0 to 8 hours.

[0038] In the above technical scheme, the reducing agent can generally be sodium ascorbate, which is not specifically limited in the present invention. The reducing agent can reduce the initiator to generate free radicals. Taking ammonium persulfate as an example, sodium ascorbate reacts with it to break the peroxide bond in the ammonium persulfate and generate sulfate radicals, thereby initiating a polymerization reaction, which can effectively control the starting point of the polymerization reaction and allow the polymerization reaction to start smoothly. The amount of reducing agent added can be designed based on experience, which is not specifically limited in the present invention.

[0039] In the above technical scheme, the chain transfer agent is mainly used to control the molecular weight of the polymer and inhibit the branching reaction, so that the obtained water reducer polymer structure is controlled, the molecular weight is controlled, and the molecular weight distribution is narrow; the present invention preferably selects a chain transfer agent with a high chain transfer coefficient, for example, at least one of aromatic disulfide esters, aliphatic disulfide esters, trithiocarbonates and sulfonates can be selected; the amount of chain transfer agent added can be designed according to the target structure of the water reducer molecule, generally according to the difference in monomer activity, the amount can be 0.05% to 5% of the monomer mass, and the present invention does not make specific limitations on this.

[0040] In order to facilitate the addition of reducing agents and chain transfer agents, these raw materials can be prepared in advance as solutions, and their mass can be converted during measurement, and the mass of the effective substances in the solution can be used for calculation. The addition speed of reducing agents and chain transfer agents can be adjusted according to the raw materials, and is generally controlled to be completed within 0 to 3 hours.

[0041] In order to ensure that the water reducer has a low ion sensitivity that can meet the requirements, the specific functional structural units in the water reducer of the present invention must ensure a sufficient proportion. In some specific embodiments of the present invention, the sum of the mass of the first reactant, the initiator, the unsaturated acid, the chain transfer agent and the reducing agent (optionally added or not) is 100%, and the total mass percentage of the starch polysaccharide containing olefin functional groups and / or the β-cyclodextrin containing olefin functional groups is ≥65%. The water reducer under this ratio condition can meet the application in a complex ionic environment, such as Example 1, Example 3 to Example 8; further, the total mass percentage of the starch polysaccharide containing olefin functional groups and / or the β-cyclodextrin containing olefin functional groups is ≥75%, such as Example 2; the water reducer under this ratio condition has lower ion sensitivity and better application effect.

[0042] Finally, the reaction solution is cooled to room temperature, and then the pH value of the reaction solution is adjusted to neutral using an aqueous solution of sodium hydroxide to obtain an ion-tolerant water-reducing agent solution. The concentration of the aqueous solution of sodium hydroxide in this step is not specifically limited and can be selected according to the specific situation. For example, a sodium hydroxide aqueous solution with a mass concentration of 15% to 30% is selected to adjust the pH value of the reaction solution to about 7.0.

[0043] Depending on the difference in the raw materials used, the water reducer can be a molecular structure with a linear structural unit, a molecular structure with a multi-arm structural unit, or a polymer molecular structure containing both a linear structural unit and a multi-arm structural unit; the linear structural unit is a linear structure with β-cyclodextrin or starch polysaccharide as a side chain; the multi-arm structural unit is a multi-arm structure with β-cyclodextrin or starch polysaccharide as the center.

[0044] The polymerization reaction is described below in the form of a reaction equation.

[0045] The following formula 1) shows an equation for a free radical polymerization reaction using unsaturated carboxylic acid, polyether monomer and monoolefin functional group β-cyclodextrin as raw materials, and the generated product is a molecular structure with linear structural units. The subscripts n, x, and m in the equation are all natural numbers greater than 1, indicating the number of various corresponding repeating structural units.

[0046]

[0047] The following formula 2) shows an equation for a free radical polymerization reaction using unsaturated carboxylic acid, polyether monomer and tetraolefin functional group β-cyclodextrin as raw materials, and the generated product is a molecular structure with multi-arm structural units. The subscripts n, x, and m in the equation are all natural numbers greater than 1, indicating the number of various corresponding repeating structural units.

[0048] It should be noted that the subscripts n, m, and x in Formula 1) and Formula 2) are not specific values, but general natural numbers. For example, the specific numbers represented by n as the subscript in the four multi-arms may be different. Similarly, the specific numbers represented by m as the subscript in the four multi-arms may be different. The specific numbers represented by x as the subscript in the four multi-arms may be different. The specific numbers represented by the subscript n in the polyether monomer and the subscript n in the product molecule may be different.

[0049]

[0050] It can be understood that the above equations 1) and 2) are only used to illustrate the linear structure or multi-arm structure of the water reducer to help understand the technical solution of the present invention, but are not intended to limit the molecular structure of the water reducer of the present invention.

[0051] The technical solution of the present invention can flexibly design the molecular structure of the water reducer, and a linear structure or a multi-arm structure can be designed by selecting raw materials; the molecular weight of the water reducer can be controlled by designing the raw material ratio and the type and quantity of the chain transfer agent; the present invention preferably regulates the molecular weight of the ion-tolerant water reducer to 5000-100000 g / mol.

[0052] The present invention also proposes an application of the aforementioned ion-tolerant water reducer in the field of concrete admixtures.

[0053] The present invention will be further described below in conjunction with specific embodiments, but this should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by technicians in this field based on the above-mentioned contents of the present invention still fall within the scope of protection of the present invention.

[0054] Example 1

[0055] Take 10g of allyl polyethylene glycol ether (APEG), 40g of monoolefin β-cyclodextrin and 40g of water and mix them evenly at 65°C. Then, 0.5g of hydrogen peroxide is added dropwise to the aqueous solution containing allyl polyethylene glycol ether and monoolefin β-cyclodextrin. After stirring evenly, solution A containing 4g of acrylic acid and solution B containing 0.201 sodium ascorbate and 0.75g of sulfonate are added dropwise to the solution containing allyl polyethylene glycol ether and monoolefin β-cyclodextrin. The dropping time is 2h and 2.5h respectively. After the dropping is completed, keep warm at 65°C for 1.5h. The reaction is completed. After the reaction solution is cooled to room temperature, 30% NaOH solution is added dropwise to the reaction system to adjust the pH value to 7 to obtain a water reducer solution.

[0056] After testing, the weight average molecular weight of the water reducer is 20000g / mol.

[0057] Example 2

[0058] Take 20g of monoolefin β-cyclodextrin and 20g of water and mix them evenly at 65°C. Then, add 0.5g of azobisisobutyronitrile to the aqueous solution of β-cyclodextrin. After stirring evenly, add solution A containing 5g of acrylic acid and solution B containing 0.75g of aromatic disulfide to the solution containing monoolefin β-cyclodextrin respectively. The adding time is 2h and 2.5h respectively. After the adding is completed, keep warm at 65°C for 1.5h. The reaction is completed. After the reaction solution is cooled to room temperature, add 30% concentration of NaOH solution to the reaction system to adjust the pH value to 7 to obtain a water reducer solution.

[0059] After testing, the weight average molecular weight of the water reducer is 30100 g / mol.

[0060] Example 3

[0061] Take 5g of allyl polyethylene glycol ether (APEG), 25g of tetraolefin β-cyclodextrin and 35g of water and mix them evenly at 75°C. Then, 0.5g of potassium persulfate is added dropwise to the aqueous solution containing allyl polyethylene glycol ether and tetraolefin β-cyclodextrin. After stirring evenly, solution A containing 5g of sodium vinyl sulfonate and solution B containing 0.55g of aliphatic disulfide are added dropwise to the solution containing allyl polyethylene glycol ether and tetraolefin β-cyclodextrin. The addition time is 1h and 2.5h, respectively. After the addition is completed, keep warm at 75°C for 1.5h. The reaction is completed. After the reaction solution is cooled to room temperature, a 30% concentration of NaOH solution is added dropwise to the reaction system to adjust the pH value to 7 to obtain a water reducer solution.

[0062] After testing, the weight average molecular weight of the water reducer is 39000g / mol.

[0063] Example 4

[0064] Take 4g of vinyl polyethylene glycol ether (VPEG), 20g of monoolefin β-cyclodextrin and 100g of water and mix them evenly at 25°C. Then, 0.5g of hydrogen peroxide is added dropwise to the aqueous solution containing allyl polyethylene glycol ether and monoolefin β-cyclodextrin. After stirring evenly, solution A containing 2.5g of acrylic acid and solution B dissolved with 0.201 sodium ascorbate and 0.35g of trithiocarbonate are added dropwise to the solution containing allyl polyethylene glycol and monoolefin β-cyclodextrin. The dropping time is 2h and 2.5h respectively. After the dropping is completed, keep warm at 25°C for 1.5h. The reaction is completed. After the reaction solution is cooled to room temperature, 30% NaOH solution is added dropwise to the reaction system to adjust the pH value to 7 to obtain a water reducer solution.

[0065] After testing, the weight average molecular weight of the water reducer is 27500 g / mol.

[0066] Example 5

[0067] Take 46g of 3-methylbutyl-3-allyl polyethylene glycol ether (IPEG) and 108g of monoolefin starch polysaccharide and 100g of water and mix them evenly at 60°C. Then, 1.80g of hydrogen peroxide is added dropwise to the solution containing 3-methylbutyl-3-allyl polyethylene glycol ether and monoolefin starch polysaccharide. After stirring evenly, solution A containing 4.8g of acrylic acid and solution B dissolved with 0.241g of sodium ascorbate and 0.30g of sulfonate are added dropwise to the solution containing 3-methylbutyl-3-allyl polyethylene glycol ether and monoolefin starch polysaccharide, respectively. The dropping time is 1h and 3.5h, respectively. After the dropping is completed, the mixture is kept warm at 60°C for 2h. The reaction is completed. After the reaction solution is cooled to room temperature, a 30% concentration of NaOH solution is added dropwise to the reaction solution to adjust the pH value to 7 to obtain a water reducer solution.

[0068] After testing, the weight average molecular weight of the water reducer is 48000g / mol.

[0069] Example 6

[0070] Take 18g of ethylene oxide butyl polyethylene glycol ether (VBPEG), 68g of diene starch polysaccharide and 100g of water and mix them evenly at 60°C. Then, 1.80g of hydrogen peroxide is added dropwise to the aqueous solution containing VBPEG and diene starch polysaccharide. After stirring evenly, solution A containing 8g of acrylic acid and solution B containing 0.225g of sodium ascorbate and 2.20g of trithiocarbonate are added dropwise to the solution containing VBPEG and diene starch polysaccharide, respectively. The dropping time is 2h and 2.5h, respectively. After the dropping is completed, keep warm at 50°C for 1.5h. The reaction is completed. After the reaction solution is cooled to room temperature, 30% NaOH solution is added dropwise to the reaction solution to adjust the pH value to 7 to obtain a water reducer solution.

[0071] After testing, the weight average molecular weight of the water reducer is 51000g / mol.

[0072] Example 7

[0073] Take 20g of vinyl polyethylene glycol ether (VPEG), 80g of polyolefin starch polysaccharide and 100g of water and mix them evenly at 55°C. Then, add 1.48g of hydrogen peroxide to the aqueous solution of VPEG and polyolefin starch polysaccharide. After stirring evenly, solution A containing 12g of acrylic acid and solution B containing 0.225g of sodium ascorbate and 1.90g of aliphatic disulfide are added dropwise to the VPEG and polyolefin starch polysaccharide solutions, respectively. The dropping time is 2h and 2.5h, respectively. After the dropping is completed, keep warm at 55°C for 1h. The reaction is completed. After the reaction solution is cooled to room temperature, a 30% concentration NaOH solution is added dropwise to the reaction solution to adjust the pH value to 7 to obtain a water reducer solution.

[0074] After testing, the weight average molecular weight of the water reducer is 88000g / mol.

[0075] Example 8

[0076] Take 18g of 3-methylbutyl-3-allyl polyethylene glycol ether (IPEG), 55g of heptaolefin β-cyclodextrin monomer and 100g of water and mix them evenly at 60°C. Then, 1.88g of hydrogen peroxide is added dropwise to the aqueous solution containing IPEG and heptaolefin β-cyclodextrin monomer. After stirring evenly, solution A containing 2.8g of acrylic acid and solution B dissolved with 0.241g of sodium ascorbate and 0.30g of sulfonate are added dropwise to the aqueous solution containing IPEG and heptaolefin β-cyclodextrin monomer, respectively. The dropping time is 2h and 2.5h, respectively. After the dropping is completed, keep warm at 60°C for 2h. The reaction is completed. The reaction solution is cooled to room temperature, and a 30% concentration of NaOH solution is added dropwise to the reaction solution to adjust the pH value to 7 to obtain a water reducer solution.

[0077] After testing, the weight average molecular weight of the water reducer is 78000g / mol.

[0078] The ion-tolerant green water-reducing agent prepared in the above embodiment was tested for its dispersibility on cement according to the method in the standard GB / T8077-2002 "Test method for homogeneity of concrete admixtures", with a water-reducing agent aqueous solution having a solid content of 35% added at 0.18% (in terms of solid content) of the cement mass, and a water-cement ratio of 0.29. The results are shown in Table 1 below.

[0079] Table 1

[0080] Example Flow performance mm Example Flow performance mm 1 285 5 288 2 255 6 292 3 282 7 281 4 287 8 298

[0081] It can be seen from the test data in Table 1 that the fluidity of the cement paste obtained by the water reducer prepared by the present invention under the test conditions is greater than 250 mm, which is much higher than the qualified standard of cement paste fluidity, indicating that the water reducer solution prepared by the technical solution of the present invention has good dispersibility for cement.

[0082] The ion-tolerant green water-reducing agents prepared in the above Examples 1 to 8 and the water-reducing agents commonly used on the market were added into concrete containing 2% of the mass of the cementitious material by sodium bicarbonate, sodium carbonate and alkali activator according to the proportions shown in Table 2 below, and the workability of the concrete was tested. The results are shown in Table 2.

[0083] Table 2

[0084] Water reducing agent type Slump mm Dosage% Water-cement ratio Control group 1 (naphthalene-based water reducer) 65 0.8 0.58 Control group 2 (aliphatic water reducer) 60 1.0 0.58 Control group 3 (polycarboxylic acid water reducer) No slump 0.4 0.42 Example 1 185 0.45 0.42 Example 2 225 0.45 0.42 Example 3 190 0.45 0.42 Example 4 205 0.45 0.42 Example 5 200 0.45 0.42 Example 6 200 0.45 0.42 Example 7 190 0.45 0.42 Example 8 185 0.45 0.42

[0085] It can be seen from the test data in Table 2 that the water-reducing agent prepared by the present invention can be well dispersed at a lower water-cement ratio. As shown in Examples 1 to 8, the slump of the concrete mixed therewith is relatively high, all ≥180 mm, indicating that when the water-reducing agent of the present invention is applied to a strong ionic chemical environment in an application scenario including sodium bicarbonate, sodium carbonate and an alkali activator, the water-reducing agent of the present invention has good adaptability.

[0086] Furthermore, when the first reactant in the preparation of the water reducer does not contain any polyether monomer, that is, the structural units of starch polysaccharides or starch polysaccharide derivatives included in the molecular structure account for a high proportion, for example, ≥75%, the prepared water reducer has better dispersibility; specifically as follows: Although the fluidity of Example 2 is slightly lower than that of other embodiments in the cement slurry test, when it is applied to a strong ionic chemical environment in an application scenario containing sodium bicarbonate, sodium carbonate and an alkali activator, its slump result is significantly higher than that of other embodiments, indicating that the water reducer of Example 2 has better adaptability in dealing with a strong ionic chemical environment in an application scenario containing sodium bicarbonate, sodium carbonate and an alkali activator, less fluidity loss, and further low ion sensitivity.

[0087] When the water reducer of control group 1 and control group 2 is used, it needs to be mixed at a higher water-cement ratio, and the dispersibility after mixing is poor, which is manifested as a low slump, all ≤65mm; when the water reducer of control group 3 is used, although it can be mixed at the same water-cement ratio as the water reducer of the present invention, the dispersibility of the mixture after mixing is very poor, which is manifested as no slump.

[0088] As can be seen from the above, the water reducer prepared by the present invention has good dispersion performance in a strong ionic chemical environment. Compared with traditional naphthalene-based water reducers, aliphatic water reducers and polycarboxylic acid water reducers, it has stronger dispersion ability in an alkali-activated system and a complex solution ion environment, which significantly improves the workability of concrete.

[0089] The technical features in the claims and / or the specification of the present invention may be combined, and the combination is not limited to the combination obtained by reference in the claims. The technical solution obtained by combining the technical features in the claims and / or the specification is also within the protection scope of the present invention.

[0090] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. An ion-tolerant water reducer, characterized in that: Its molecular structure includes structural units of starch polysaccharide or starch polysaccharide derivatives.

2. The ion-tolerant water reducer according to claim 1, characterized in that: The mass proportion of the structural units of the starch polysaccharide or starch polysaccharide derivative in the ion-tolerant water reducer is ≥65%.

3. The ion-tolerant water reducer according to claim 1, characterized in that: The starch polysaccharide derivative is β-cyclodextrin.

4. The ion-tolerant water reducer according to claim 3, characterized in that: The ion-tolerant water reducer has a linear structural unit and / or a multi-arm structural unit; the linear structural unit is a linear structure with β-cyclodextrin or starch polysaccharide as a side chain; the multi-arm structural unit is a multi-arm structure with β-cyclodextrin or starch polysaccharide as the center.

5. The ion-tolerant water reducing agent according to any one of claims 1 to 4, characterized in that: The molecular weight of the ion-tolerant water reducer is 5000 to 100000 g / mol.

6. A method for preparing an ion-tolerant water reducer, characterized in that: It includes the following steps: S61: uniformly mixing the first reactant with water to obtain a first reactant aqueous solution; the first reactant comprises at least one of a starch polysaccharide containing an olefin functional group and a β-cyclodextrin containing an olefin functional group; the starch polysaccharide containing an olefin functional group has a molecular weight of 1000 to 3000 g / mol; S62 adds an initiator to the aqueous solution of the first reactant, and stirs uniformly to obtain an initiator solution; S63, adding an unsaturated acid solution and a chain transfer agent solution to the initiator solution respectively, and keeping the temperature at the reaction temperature to obtain a reaction solution; based on the sum of the mass of the first reactant, the initiator, the unsaturated acid and the chain transfer agent being 100%, the total mass percentage of the starch polysaccharide containing an olefin functional group and / or the β-cyclodextrin containing an olefin functional group is ≥ 65%; S64 The reaction solution is cooled to room temperature, and its pH value is adjusted to be neutral to obtain an ion-tolerant water-reducing agent solution.

7. The preparation method according to claim 6, characterized in that: The starch polysaccharide containing olefin functional groups is selected from at least one of monoolefin functional starch polysaccharides, diolefin functional starch polysaccharides, pentaolefin functional starch polysaccharides, heptaolefin functional starch polysaccharides and N-olefin functional starch polysaccharides; wherein N is a natural number ≥10; the β-cyclodextrin containing olefin functional groups is selected from at least one of monoolefin functional β-cyclodextrin, diolefin functional β-cyclodextrin, triolefin functional β-cyclodextrin, tetraolefin functional β-cyclodextrin and heptaolefin functional β-cyclodextrin.

8. The preparation method according to claim 6, characterized in that: The first reactant also includes a polyether monomer; the polyether monomer is selected from at least one of propyl polyethylene glycol ether, 2-methylprop-2-enyl polyethylene glycol ether, 3-methylbut-3-allyl polyethylene glycol ether, vinyl polyethylene glycol ether and vinyloxybutyl polyethylene glycol ether; the unsaturated acid is selected from at least one of unsaturated carboxylic acid, unsaturated sulfonic acid and unsaturated phosphoric acid; the unsaturated carboxylic acid is selected from at least one of acrylic acid, methyl acrylate, ethyl propionate, methacrylic acid and hydroxyethyl acrylate; the unsaturated sulfonic acid is selected from at least one of sodium acrylic acid sulfonate, sodium vinyl sulfonate and sodium methacrylic acid; the unsaturated phosphate is selected from at least one of 2-methyl-2-acrylic acid-2-hydroxyethyl ester phosphate, alkyl acrylate phosphate, ethylene glycol methacrylate phosphate and methacryloyloxyethyl phosphate.

9. The preparation method according to claim 6, characterized in that: The initiator is selected from at least one of azobisisobutyronitrile, potassium persulfate and hydrogen peroxide; the chain transfer agent is selected from at least one of aromatic disulfide esters, aliphatic disulfide esters, trithiocarbonates and sulfonate esters.

10. Use of the ion-tolerant water-reducing agent according to any one of claims 1 to 5 in the field of concrete admixtures.

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