A polycarboxylic water reducing agent special for desert sand concrete, a preparation method thereof and desert sand concrete

Abstract

This invention relates to the field of concrete admixtures, and particularly to a polycarboxylate superplasticizer specifically for desert sand concrete, its preparation method, and desert sand concrete itself. The polycarboxylate superplasticizer is polymerized by free radical polymerization of modified polyether macromonomers with unsaturated carboxylic acids and / or anhydrides. This polycarboxylate superplasticizer is adapted to the specific characteristics of desert sand concrete. When applied in the preparation of desert sand concrete, it can reduce the viscosity of the concrete slurry, increase the water reduction rate, and improve the strength of the resulting desert sand concrete. It exhibits good anti-mud effect and high water reduction rate even with a relatively low superplasticizer dosage. This invention can reduce the manufacturing cost of desert sand concrete, solving the problems of high superplasticizer dosage, high concrete manufacturing cost, and poor concrete strength caused by the poor performance of traditional polycarboxylate superplasticizers in the preparation of desert sand concrete. It also reduces application obstacles when introducing desert sand as a substitute for industrial sand in concrete preparation, alleviating the shortage of industrial sand in the industry.

Description

Technical Field

[0001] This invention relates to the field of concrete admixture technology, and in particular to a polycarboxylate superplasticizer for desert sand concrete, its preparation method, and desert sand concrete. Background Technology

[0002] Currently, there is a shortage of engineering sand in Northwest my country, while the region is rich in desert sand resources, with large and abundant reserves in the northwest. Therefore, in the construction industry, using desert sand to replace all or part of the natural engineering sand in concrete preparation can alleviate the shortage of industrial sand in my country, thereby reducing transportation costs of raw materials such as engineering sand and lowering project costs.

[0003] However, there are still some challenges and obstacles to using desert sand in concrete preparation:

[0004] In the application of desert sand concrete, polycarboxylate superplasticizers are usually compounded with other engineering additives and added to the desert sand concrete. However, due to the characteristics of desert sand, such as small particle size, low particle size distribution, high mud content (high clay content), severe weathering, poor adsorption, and high water demand, the existing traditional polycarboxylate superplasticizers are not effective in desert sand concrete. The required dosage of polycarboxylate superplasticizer is high, and the water-reducing effect is poor. This results in high manufacturing costs and low concrete strength, which limits the application of desert sand.

[0005] In summary, traditional polycarboxylate superplasticizers are not suitable for desert sand concrete. Their addition to desert sand concrete is ineffective, resulting in high project costs and poor performance. Furthermore, traditional polycarboxylate superplasticizers have a single functional monomer, which cannot meet the needs of desert sand in this special case. Summary of the Invention

[0006] To address the problems of existing polycarboxylate superplasticizers mentioned in the background section, this invention provides a polycarboxylate superplasticizer specifically for desert sand concrete, the technical solution of which is as follows:

[0007] This special polycarboxylate superplasticizer for desert sand concrete is polymerized by free radical polymerization of modified polyether macromonomers with unsaturated carboxylic acids and / or anhydrides.

[0008] The structural formula of the modified polyether macromonomer is shown below:

[0009]

[0010] In this context, R1, R2, and R3 are each independently -H, -OH, a halogen group, or a C1-C5 alkyl or C1-C5 alkoxy group; R4 is -H, -OH, a halogen group, or a C1-C5 alkyl or C1-C5 alkoxy group or -NO2; R5 is -H or a C1-C5 alkyl group, and n is an integer from 50 to 2000.

[0011] The polycarboxylate superplasticizer is polymerized via free radical polymerization with modified polyether macromonomers and unsaturated carboxylic acids and / or anhydrides, so that the molecular chain of the polycarboxylate superplasticizer is linked with the p-hydroxybenzoate modification unit shown in the following structural formula:

[0012] ,

[0013] R1, R2, and R3 are each independently -H, -OH, a halogen group, or a C1-C5 alkyl or C1-C5 alkoxy group; R4 is -H, -OH, a halogen group, or a C1-C5 alkyl or C1-C5 alkoxy group or -NO2.

[0014] In some embodiments, the modified polyether macromonomer and unsaturated carboxylic acid and / or acid anhydride are subjected to free radical polymerization under the action of an oxidant, a reducing agent, and a chain transfer agent to obtain the polycarboxylic acid water-reducing agent; wherein the free radical polymerization reaction temperature is 30-80°C; and the weight ratio of the modified polyether macromonomer, unsaturated carboxylic acid, acid anhydride, and oxidant is (50-220):(0.2-40):(0.1-20):(1-10).

[0015] In some embodiments, the unsaturated carboxylic acid is at least one selected from acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate; the acid anhydride is at least one selected from maleic anhydride, maleic anhydride, isophthalic anhydride, and phthalic anhydride; and the oxidizing agent is at least one selected from hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, cumene hydroperoxide, benzoyl peroxide, dihexyl percarbonate, and tert-butyl hydroperoxide.

[0016] In some embodiments, the free radical polymerization process is as follows:

[0017] The modified polyether macromonomer, the first part of unsaturated carboxylic acid and / or the first part of acid anhydride, and the oxidizing agent are dissolved in water to obtain the base solution;

[0018] Dissolve the second part of the unsaturated carboxylic acid and / or the second part of the acid anhydride in water to obtain solution A;

[0019] The reducing agent and chain transfer agent are dissolved in water to obtain solution B;

[0020] The substrate is heated to 30-80°C, and then the reaction temperature is maintained at 30-80°C. Solution A and solution B are added dropwise to the substrate to carry out the polymerization reaction. After the addition is complete, the reaction continues for a certain period of time.

[0021] The dropwise addition times for solutions A and B are 1.0–4.5 h, respectively. After both solutions A and B are added, the reaction continues for 0.5–5 h. The sum of the amounts of the two unsaturated carboxylic acids is the total amount of unsaturated carboxylic acids, and the sum of the amounts of the two acid anhydrides is the total amount of unsaturated carboxylic acids.

[0022] In some embodiments, the reducing agent is at least one selected from ascorbic acid, azobisisopropylimidazoline hydrochloride, sodium metabisulfite, sodium formaldehyde sulfoxylate, ferrous sulfate, sodium hypophosphite, sodium phosphite, and ferrous ammonium sulfate; the chain transfer agent is a thiol chain transfer agent; preferably selected from at least one selected from mercaptoacetic acid, mercaptopropionic acid, mercaptoethanol, and mercaptopropanol; the weight ratio of the modified polyether macromonomer, reducing agent, chain transfer agent, and water is (50-220):(2-10):(1-10):(100-250); the amount of oxidant is 3.0%-10.0% of the total mass of the modified polyether macromonomer.

[0023] In some embodiments, the modified polyether macromonomer is prepared by a first condensation reaction of a polyether macromonomer and a p-ester benzoic acid compound under the action of a catalyst.

[0024] The structural formula of the p-ester benzoic acid compound is as follows:

[0025] ,

[0026] R1, R2, and R3 are each independently -H or -OH or a halogen group or a C1-C5 alkyl or C1-C5 alkoxy group; R4 is -H or -OH or a halogen group or a C1-C5 alkyl or C1-C5 alkoxy group or -NO2.

[0027] The structural formula of the polyether macromonomer is as follows:

[0028]

[0029] Wherein, R5 is an -H or C1-C5 alkyl group, and n is an integer from 50 to 2000.

[0030] In some embodiments, the p-esterified benzoic acid compound is prepared by a second condensation reaction of p-hydroxybenzoic acid and a p-benzoic acid compound under the action of a catalyst;

[0031] The structural formula of p-hydroxybenzoic acid is as follows:

[0032] ;

[0033] The structural formula of the benzoic acid compounds is as follows:

[0034]

[0035] R1, R2, and R3 are each independently -H, -OH, a halogen group, or a C1-C5 alkyl or C1-C5 alkoxy group; R4 is -H, -OH, a halogen group, or a C1-C5 alkyl or C1-C5 alkoxy group or -NO2.

[0036] In some embodiments, the molar ratio of the polyether macromonomer to the p-benzoic acid compound is 1:(1-10), the reaction temperature of the first condensation reaction is 40-180°C, and the reaction time is 5-210 min; the molar ratio of the p-hydroxybenzoic acid to the p-benzoic acid compound is (1-10):(1-10), the reaction temperature of the second condensation reaction is 40-180°C, and the reaction time is 10-210 min; the catalyst is concentrated sulfuric acid.

[0037] This invention also provides a method for preparing the polycarboxylate superplasticizer for desert sand concrete as described above, characterized by comprising the following steps:

[0038] The modified polyether macromonomer, the first part of unsaturated carboxylic acid and / or the first part of acid anhydride, and the oxidizing agent are dissolved in water to obtain the base solution;

[0039] Dissolve the second part of the unsaturated carboxylic acid and / or the second part of the acid anhydride in water to obtain solution A;

[0040] The reducing agent and chain transfer agent are dissolved in water to obtain solution B;

[0041] Heat the base liquid to 30-80°C, and then maintain the reaction temperature at 30-80°C. Add solution A and solution B dropwise into the substrate to carry out the polymerization reaction. After the addition is complete, continue the reaction for a certain period of time.

[0042] The dropwise addition times for solutions A and B are 1.0–4.5 h, respectively. After both solutions A and B are added, the reaction continues for 0.5–5 h. The sum of the amounts of the two unsaturated carboxylic acids is the total amount of unsaturated carboxylic acids, and the sum of the amounts of the two acid anhydrides is the total amount of unsaturated carboxylic acids.

[0043] The present invention also provides a desert sand concrete, the raw material components of which include desert sand, cement, and polycarboxylate superplasticizer as described above.

[0044] Based on the above, compared with the prior art, the polycarboxylate superplasticizer for desert sand concrete provided by the present invention has the following beneficial effects:

[0045] The polycarboxylate superplasticizer for desert sand concrete provided by this invention can adapt to the corresponding characteristics of desert sand concrete. When applied to the preparation of desert sand concrete, it can reduce the viscosity of desert sand concrete slurry, increase the water reduction rate, and improve the strength of the obtained desert sand concrete. It can achieve good anti-mud effect and high water reduction rate even with a low dosage of superplasticizer.

[0046] Therefore, this invention can effectively reduce the manufacturing cost of desert sand concrete, solve the defects of traditional polycarboxylate superplasticizers in the preparation of desert sand concrete, such as high superplasticizer dosage, high concrete manufacturing cost, and poor concrete strength, which are caused by poor performance. It also reduces the application obstacles when desert sand is introduced to replace industrial sand in concrete preparation, alleviates the shortage of industrial sand in the industry, thereby reducing the transportation cost of industrial sand raw materials and lowering the cost of concrete engineering.

[0047] Other features and beneficial effects of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects of the invention and other beneficial effects may be realized and obtained by means of the structures particularly pointed out in the description and claims. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] In the description of this invention, it should be noted that all terms used in this invention (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and should not be construed as limiting the invention; it should be further understood that the terms used in this invention should be understood to have the same meaning as those in the context of this specification and in the relevant field, and should not be understood in an idealized or overly formal sense, except as expressly defined in this invention.

[0050] The present invention provides a preferred example of the preparation process of p-ester-benzoic acid compounds, modified polyether macromonomers, and polycarboxylate superplasticizers for desert sand concrete as follows:

[0051] 1. The preparation process of p-esterified benzoic acid compounds is as follows:

[0052] p-hydroxybenzoic acid and p-benzoic acid compounds are dissolved in water, a catalyst is added to catalyze the reaction, and the mixture is stirred to carry out a second condensation reaction, thus obtaining the product.

[0053] Wherein, the molar ratio of p-hydroxybenzoic acid to p-benzoic acid compounds is (1-10):(1-10), the reaction temperature of the second condensation reaction is 40-180℃, and the reaction time is 10-210 min;

[0054] The catalyst is concentrated sulfuric acid;

[0055] The structural formula of p-hydroxybenzoic acid is as follows:

[0056] ;

[0057] The structural formula of the benzoic acid compounds is as follows:

[0058]

[0059] R1, R2, and R3 are each independently -H, -OH, a halogen group, or a C1-C5 alkyl or C1-C5 alkoxy group; R4 is -H, -OH, a halogen group, or a C1-C5 alkyl or C1-C5 alkoxy group or -NO2.

[0060] The structural formula of the obtained p-ester benzoic acid compounds is as follows:

[0061] ,

[0062] R1, R2, and R3 are each independently -H, -OH, a halogen group, or a C1-C5 alkyl or C1-C5 alkoxy group; R4 is -H, -OH, a halogen group, or a C1-C5 alkyl or C1-C5 alkoxy group or -NO2.

[0063] 2. The preparation process of the modified polyether macromonomer is as follows:

[0064] The polyether macromonomer and a p-ester benzoic acid compound are dissolved in water, a catalyst is added, and the mixture is stirred to carry out the first condensation reaction, thus obtaining the product.

[0065] The molar ratio of the polyether macromonomer to the p-ester benzoic acid compound is 1:(1-10), the reaction temperature of the first condensation reaction is 40-180℃, and the reaction time is 5-210 min.

[0066] The structural formula of the polyether macromonomer is as follows:

[0067]

[0068] Wherein, R5 is an -H or C1-C5 alkyl group, and n is an integer from 50 to 2000.

[0069] The structural formula of the obtained modified polyether macromonomer is shown below:

[0070]

[0071] In this context, R1, R2, and R3 are each independently -H, -OH, a halogen group, or a C1-C5 alkyl or C1-C5 alkoxy group; R4 is -H, -OH, a halogen group, or a C1-C5 alkyl or C1-C5 alkoxy group or -NO2; R5 is -H or a C1-C5 alkyl group, and n is an integer from 50 to 2000.

[0072] 3. Preparation process of polycarboxylate superplasticizer for desert sand concrete

[0073] The modified polyether macromonomer, the first part of unsaturated carboxylic acid and / or the first part of acid anhydride, and the oxidizing agent are dissolved in water to obtain the base solution;

[0074] Dissolve the second part of the unsaturated carboxylic acid and / or the second part of the acid anhydride in water to obtain solution A;

[0075] The reducing agent and chain transfer agent are dissolved in water to obtain solution B;

[0076] The substrate solution is heated to 30–80°C, and then the reaction temperature is maintained at 30–80°C. Solution A and solution B are added dropwise to the substrate to carry out the polymerization reaction. After the addition is complete, the reaction continues for a certain period of time. The dropwise addition time of solution A and solution B is 1.0–4.5 h, respectively. After both solutions A and B are added, the reaction continues for 0.5–5 h. The sum of the amounts of the two unsaturated carboxylic acids is the total amount of unsaturated carboxylic acids, and the sum of the amounts of the two acid anhydrides is the total amount of unsaturated carboxylic acids.

[0077] It should be noted that each unsaturated carboxylic acid can be a single unsaturated carboxylic acid or a mixture of multiple unsaturated carboxylic acids; each acid anhydride can be a single acid anhydride or a mixture of multiple acid anhydrides.

[0078] Regarding the raw material ratio:

[0079] The total weight ratio of the modified polyether macromonomer, unsaturated carboxylic acid, acid anhydride, oxidant, reducing agent, chain transfer agent, and water is (50-220):(0.2-40):(0.1-20):(1-10):(2-10):(1-10):(100-250).

[0080] Preferably, the amount of oxidant used is 3.0% to 10.0% of the total mass of the modified polyether macromonomer;

[0081] Preferably, the amount of the reducing agent is 5.0% to 12.0% of the total mass of the modified polyether macromonomer;

[0082] Preferably, the amount of chain transfer agent used is 10.0% to 12.0% of the total mass of the modified polyether macromonomer, unsaturated carboxylic acid, and acid anhydride.

[0083] Regarding the selection of raw materials:

[0084] The unsaturated carboxylic acid is at least one selected from acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate.

[0085] The acid anhydride is at least one of maleic anhydride, maleic anhydride, isophthalic anhydride, and phthalic anhydride;

[0086] The oxidant is at least one of hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, cumene hydroperoxide, benzoyl peroxide, dihexyl percarbonate, and tert-butyl hydroperoxide.

[0087] Preferably, the reducing agent is at least one selected from ascorbic acid, azobisisopropylimidazoline hydrochloride, sodium metabisulfite, sodium formaldehyde sulfoxylate, ferrous sulfate, sodium hypophosphite, sodium phosphite, and ferrous ammonium sulfate; the chain transfer agent is a thiol chain transfer agent, more preferably selected from at least one selected from mercaptoacetic acid, mercaptopropionic acid, mercaptoethanol, and mercaptopropanol.

[0088] To verify the effectiveness of the present invention, the present invention also provides the following embodiments and comparative examples:

[0089] Example 1:

[0090] S1. Dissolve p-benzoic acid compounds and p-hydroxybenzoic acid in water at 80°C, add concentrated sulfuric acid for catalysis, stir the reaction at 80°C for 120 min, cool to precipitate crystals after the reaction, add cold water to crystallize, filter to obtain solid product, dry to obtain p-esterified benzoic acid compounds, namely 2-(4-chlorobenzyl)-benzoic acid.

[0091] The molar ratio of p-hydroxybenzoic acid, benzoic acid compounds, water, and concentrated sulfuric acid catalyst is 3:1:10:0.1.

[0092] The structural formula of the benzoic acid compounds is as follows:

[0093] ,

[0094] The structural formulas of p-esterified benzoic acid compounds are as follows:

[0095]

[0096] Among them, R1, R2, and R3 are each independently -H; R4 is -H.

[0097] S2. The obtained 2-(4-chlorobenzyl)-benzoic acid and polyether macromonomer (methylallyl polyethylene glycol) were dissolved in water, concentrated sulfuric acid catalyst was added, and the mixture was stirred to carry out a condensation reaction. After the reaction was completed, the mixture was cooled to precipitate crystals. After adding cold water to crystallize, the mixture was filtered and dried to obtain modified polyoxyethylene ether. The reaction temperature was 110℃ and the reaction time was 80 min.

[0098] The molar ratio of polyether macromonomer, p-benzoic acid compound, water, and concentrated sulfuric acid catalyst is 1:3:20:0.1.

[0099] The structural formula of the polyether macromonomer (methylallyl polyethylene glycol) is as follows:

[0100]

[0101] Where R5 is -H and n is 500.

[0102] The structural formula of the obtained modified polyether macromonomer is shown below:

[0103]

[0104] Among them, R1, R2, and R3 are each independently -H, R4 is -H, R5 is -H, and n is 500.

[0105] S3. Dilute the acrylic acid with deionized water to obtain solution A; in step S3, the mass ratio of acrylic acid to water is 10:15;

[0106] S4. Dilute ferrous sulfate and mercaptoacetic acid with deionized water to obtain solution B; in step S4, the mass ratio of ferrous sulfate, mercaptoacetic acid and water is 5:4:100;

[0107] S5. Add modified polyoxyethylene ether, acrylic acid, maleic anhydride, methacrylic acid, hydrogen peroxide, ammonium persulfate and the remaining deionized water to the reaction vessel, stir evenly to obtain the base liquid, and heat to the reaction temperature of 30°C.

[0108] In step S5, the mass ratio of modified polyoxyethylene ether, acrylic acid, maleic anhydride, methacrylic acid, hydrogen peroxide, ammonium persulfate, and the remaining deionized water is 200:0.3:10:2:3:1:150.

[0109] S6. Maintain the reaction temperature at 30°C, and slowly add solution A and solution B dropwise to the bottom liquid of the reaction vessel while stirring. Complete the addition of solution A and solution B within 2 hours. After the addition of solution A and solution B is completed, continue to keep the temperature and react for another 2 hours to obtain the mother liquor of polycarboxylate superplasticizer for desert sand.

[0110] In step S6,

[0111] The mass ratio of substrate, solution A, and solution B is 360:28:33.

[0112] Example 2:

[0113] S1. Dissolve p-benzoic acid compounds and p-hydroxybenzoic acid in water at 50°C, add concentrated sulfuric acid for catalysis, stir the reaction at 95°C for 120 min, cool to precipitate crystals after the reaction, add cold water to crystallize, filter, and dry to obtain p-esterified benzoic acid compounds, namely 3-bromo-2-(4-chlorobenzyl)-benzoic acid.

[0114] The molar ratio of p-hydroxybenzoic acid, p-benzoic acid compounds, water, and concentrated sulfuric acid catalyst is 4:1:20:0.2.

[0115] The structural formula of the benzoic acid compounds is as follows:

[0116] ,

[0117] The structural formulas of p-esterified benzoic acid compounds are as follows:

[0118]

[0119] Among them, R1, R2, and R3 are -H, -Br, and -H, respectively; R4 is -H.

[0120] S2. The obtained p-ester benzoic acid compound and polyether macromonomer (methyl allyl polyethylene glycol) are dissolved in water, concentrated sulfuric acid catalyst is added, and the mixture is stirred to carry out a condensation reaction. After the reaction is completed, the mixture is cooled to precipitate crystals. After adding cold water to crystallize, the mixture is filtered and dried to obtain modified polyoxyethylene ether. The reaction temperature is 90℃ and the reaction time is 120min.

[0121] The molar ratio of polyether macromonomer, p-benzoic acid compound, water, and concentrated sulfuric acid catalyst is 1:2:30:0.1.

[0122] The structural formula of the polyether macromonomer (methylallyl polyethylene glycol) is as follows:

[0123] ,

[0124] Where R5 is -CH3 and n is 1000;

[0125] The structural formula of the obtained modified polyether macromonomer is shown below:

[0126]

[0127] Among them, R1, R2, and R3 are -H, -Br, and -H, respectively; R4 is -H.

[0128] S3. Dilute the acrylic acid with deionized water to obtain solution A; in step S3, the mass ratio of acrylic acid to water is 9:16;

[0129] S4. Dilute ascorbic acid and mercaptopropionic acid with deionized water to obtain solution B; in step S4, the mass ratio of ascorbic acid, mercaptopropionic acid and water is 8:3:90;

[0130] S5. Add modified polyoxyethylene ether, maleic anhydride, methacrylic acid, tert-butyl hydroperoxide, benzoyl peroxide and the remaining deionized water to the reaction vessel, stir evenly to obtain the bottom liquid, and heat to the reaction temperature of 40°C.

[0131] In step S5, the mass ratio of modified polyoxyethylene ether, maleic anhydride, methacrylic acid, tert-butyl hydroperoxide, benzoyl peroxide and the remaining deionized water is 220:0.5:9:4:6:5:160.

[0132] S6. Maintain the reaction temperature at 70℃, and slowly add solution A and solution B dropwise to the bottom liquid of the reaction vessel while stirring. Complete the addition of solution A and solution B within 2 hours. After the addition of solution A and solution B is completed, continue to keep the temperature and react for 4 hours to obtain the mother liquor of polycarboxylate superplasticizer for desert sand.

[0133] In step S6, the mass ratio of substrate, solution A, and solution B is 350:30:33.

[0134] Example 3:

[0135] S1. Dissolve p-benzoic acid compounds and p-hydroxybenzoic acid in water at 40°C, add concentrated sulfuric acid for catalysis, stir the reaction at 40°C for 90 min, add cold water to crystallize, filter, and dry to obtain p-esterified benzoic acid compounds, namely 2-(4-chlorobenzyl)-6-nitrobenzoic acid.

[0136] The molar ratio of p-hydroxybenzoic acid, p-benzoic acid compounds, water, and concentrated sulfuric acid catalyst is 2:1:20:0.1.

[0137] The structural formula of the benzoic acid compounds is as follows:

[0138] ,

[0139] The structural formulas of p-esterified benzoic acid compounds are as follows:

[0140] ,

[0141] Among them, R1, R2, and R3 are all -H; R4 is -NO2.

[0142] S2. The obtained p-ester benzoic acid compound and polyether macromonomer (methyl allyl polyethylene glycol) are dissolved in water, concentrated sulfuric acid catalyst is added, and the mixture is stirred to carry out a condensation reaction. After the reaction is completed, the mixture is cooled to precipitate crystals. After adding cold water to crystallize, the mixture is filtered and dried to obtain modified polyoxyethylene ether. The reaction temperature is 150℃ and the reaction time is 150min.

[0143] The molar ratio of polyether macromonomer, p-ester benzoic acid compound, water, and concentrated sulfuric acid catalyst is 1:3:30:0.1.

[0144] The structural formula of the polyether macromonomer (methylallyl polyethylene glycol) is as follows:

[0145] ,

[0146] Where R5 is -C3H7 and n is 2000;

[0147] The structural formula of the obtained modified polyether macromonomer is shown below:

[0148]

[0149] Among them, R1, R2, and R3 are all -H; R4 is -NO2.

[0150] S3. Dilute the acrylic acid with deionized water to obtain solution A; in step S3, the mass ratio of acrylic acid to water is 12:17;

[0151] S4. Dilute sodium hypophosphite, mercaptoacetic acid, and mercaptopropionic acid with deionized water to obtain solution B; in step S4, the mass ratio of sodium hypophosphite, mercaptoacetic acid, mercaptopropionic acid, and water is 20:4:3:200;

[0152] S5. Add modified polyoxyethylene ether, maleic anhydride, isophthalic anhydride, phthalic anhydride, methacrylic acid, benzoyl peroxide, dihexyl peroxide and the remaining deionized water to the reaction vessel, stir evenly to obtain the bottom liquid, and heat to the reaction temperature of 55℃.

[0153] In step S5, the mass ratio of modified polyoxyethylene ether, maleic anhydride, isophthalic anhydride, phthalic anhydride, methacrylic acid, benzoyl peroxide, dihexyl percarbonate, and the remaining deionized water is 180:0.5:7:9:4:6:5:150.

[0154] S6. Maintain the reaction temperature at 55℃, and slowly add solution A and solution B dropwise to the bottom liquid of the reaction vessel while stirring. Complete the addition of solution A and solution B within 2 hours. After the addition of solution A and solution B is completed, continue to keep the temperature and react for 5 hours to obtain the mother liquor of polycarboxylate superplasticizer for desert sand.

[0155] In step S6, the mass ratio of substrate, solution A, and solution B is 350:30:37.

[0156] Comparative Example 1: (The polyether macromonomer is not modified)

[0157] The only difference between this comparative example and Example 1 is that, in the preparation of the polycarboxylate superplasticizer, i.e., in step S5, the modified polyoxyethylene ether is replaced by an equal mass of methyl allyl polyethylene glycol monomethyl ether. The other preparation processes and conditions are the same as in Example 1, and it is used for a comparative study of the performance of the polycarboxylate superplasticizer in the embodiments of the present invention.

[0158] The molecular weight of methyl allyl polyethylene glycol monomethyl ether is 2000.

[0159] Comparative Example 2: (The polyether macromonomer was not modified)

[0160] The only difference between this comparative example and Example 2 is that, in the preparation of the polycarboxylate superplasticizer, i.e., in step S5, the modified polyoxyethylene ether is replaced with isopentenyl alcohol polyoxyethylene ether by mass. The other preparation processes and conditions are the same as in Example 2, and it is used for a performance comparison study of the polycarboxylate superplasticizer with the examples of the present invention.

[0161] The molecular weight of isopentenyl alcohol polyoxyethylene ether is 5000.

[0162] Comparative Example 3: (The polyether macromonomer was not modified)

[0163] The only difference between this comparative example and Example 3 is that, in the preparation of the polycarboxylate superplasticizer, i.e., in step S5, the modified polyoxyethylene ether is replaced by ethylene glycol monovinyl polyethylene glycol ether in equal mass. The other preparation processes and conditions are the same as in Example 3. This example is used for a comparative study of the performance of the polycarboxylate superplasticizer in the embodiments of the present invention.

[0164] The molecular weight of ethylene glycol monovinyl polyethylene glycol ether is 3000.

[0165] Comparative Example 4: (The molecular weight of the selected polyether macromonomer is outside the scope of this application)

[0166] The only difference between this comparative example and Example 1 is that, in the preparation of the modified polyether macromonomer, i.e., in step S2, the polyether macromonomer (methylallyl polyethylene glycol) used in Example 1 is replaced by an equal mass of 3000 with a molecular weight of 500 (i.e., n=30). The other preparation processes and conditions are the same as in Example 1. This example is used for a comparative study of the performance of the polycarboxylate superplasticizer in the examples of this invention.

[0167] Comparative Example 5: (The amount of oxidant used is not within the scope of this application)

[0168] The only difference between this comparative example and Example 1 is that the amount of oxidant used in the preparation of the polycarboxylate superplasticizer is 12% of the total mass of the modified polyether macromonomer. The other preparation processes and conditions are the same as in Example 1. This example is used for a comparative study of the performance of the polycarboxylate superplasticizer in the embodiments of the present invention.

[0169] Comparative Example 6: (The amount of oxidant used is not within the scope of this application)

[0170] The only difference between this comparative example and Example 1 is that the reaction temperature of the base liquid in steps S5 and S6 is 25°C when preparing the polycarboxylate superplasticizer. The other preparation processes and conditions are the same as in Example 1. This example is used for a comparative study of the performance of the polycarboxylate superplasticizer in the embodiments of the present invention.

[0171] Performance testing of the products in the examples and comparative examples:

[0172] Performance tests were conducted on the polycarboxylate superplasticizer mother liquors prepared in the examples and comparative examples:

[0173] According to GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures", the polycarboxylate superplasticizers prepared in the above examples and comparative examples were tested for mortar fluidity.

[0174] According to GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the polycarboxylate superplasticizer prepared in the above examples and comparative examples was added to the concrete, and the initial slump, 3-hour slump, and 28-day compressive strength of the concrete were measured; wherein, the water-cement ratio was fixed at 0.48.

[0175] The concrete mix proportions are as follows: water: 175 kg, cement (Southern Cement P.052.5R): 360 kg, desert sand (mud content 5%): 790 kg, and stone: 1060 kg.

[0176] The specific test results are shown in Table 1 below:

[0177] Table 1

[0178]

[0179] Analysis of performance test results of the products in the examples and comparative examples:

[0180] (1) As can be seen from the above results, the polycarboxylate superplasticizer obtained in the embodiments of this application can reduce the viscosity of concrete slurry, increase the water reduction rate, and improve the strength of desert sand concrete when applied to desert sand concrete.

[0181] (2) The polyether macromonomers used in Comparative Examples 1-3 were not modified, that is, the polycarboxylate superplasticizers synthesized in Comparative Examples 1-3 were ordinary polycarboxylate superplasticizers. It can be seen from the data in the table that the initial mortar fluidity of the polycarboxylate superplasticizers obtained in Comparative Examples 1-3 was significantly lower than that in the Example, and the slump of Comparative Examples 1-3 was also smaller than that in the Example. It can be seen that compared with the ordinary polycarboxylate superplasticizers prepared in Comparative Examples 1-3, the polycarboxylate superplasticizers provided in the Examples of the Invention have a higher water reduction rate.

[0182] Compared with the polycarboxylate superplasticizer obtained in the comparative example, the superplasticizer in this embodiment can achieve a higher water reduction rate at a lower dosage. Its water reduction rate is better, and the resulting desert sand concrete has higher compressive strength. It can effectively reduce the manufacturing cost of desert sand concrete and solve the defect that the traditional polycarboxylate superplasticizer requires a high dosage to prepare desert sand concrete, which leads to high cost.

[0183] (3) Compared with Example 1, Comparative Example 4 uses a modified polyether macromonomer with a larger molecular weight. It can be seen from the data in the table that the initial mortar fluidity of the polycarboxylate superplasticizer obtained in Comparative Example 4 is significantly lower than that in Example 1, and the slump of Comparative Example 4 is also smaller than that in Example 1. The adsorption amount on the surface of desert sand in Comparative Example 4 is significantly greater than that in Example 1. It can be seen that compared with the modified polycarboxylate superplasticizer prepared in Comparative Example 4, the polycarboxylate superplasticizer provided in the present invention has a higher superplasticity.

[0184] Compared with the polycarboxylate superplasticizer obtained in the comparative example, the superplasticizer in this embodiment can adsorb less on the surface of desert sand at a lower dosage, while meeting the higher water reduction rate required in mortar and concrete applications. Furthermore, the desert sand concrete produced has higher compressive strength, which can effectively reduce the manufacturing cost of desert sand concrete and solve the problem of high cost caused by the high dosage of traditional polycarboxylate superplasticizers when used to prepare desert sand concrete.

[0185] In summary, the polycarboxylate superplasticizer for desert sand concrete and its preparation method provided by this invention include at least the following design concepts and beneficial effects:

[0186] 1. Design concept and beneficial effects

[0187] The polycarboxylate superplasticizer for desert sand concrete of this invention introduces a biphenyl ring unsaturated functional monomer into its molecular chain, adapting it to the corresponding characteristics of desert sand concrete. When applied to desert sand concrete, the corresponding p-hydroxybenzoic acid structure in the molecular chain gives it a better anti-mud effect, effectively reducing the viscosity of concrete slurry, increasing the water reduction rate, and improving the strength of the obtained desert sand concrete. It can achieve good anti-mud effect and high water reduction rate with a low superplasticizer dosage. At the same time, this application uses a low molecular weight polyether macromonomer, which can better reduce the waste caused by the larger specific surface area of ​​desert sand compared with traditional manufactured sand, resulting in more polycarboxylate superplasticizer adsorbed on the sand surface. This makes it difficult for polycarboxylate superplasticizer to be adsorbed on the surface of desert sand, but it can be better adsorbed on the surface of cement particles through electrostatic adsorption and complexation reaction with Ca2+ on the cement surface. The resulting steric hindrance is relatively large, thereby improving the dispersion ability, which is beneficial for the application of polycarboxylate superplasticizer in desert sand concrete.

[0188] Therefore, this invention can effectively reduce the manufacturing cost of desert sand concrete, solve the defects of traditional polycarboxylate superplasticizers in the preparation of desert sand concrete, such as high superplasticizer dosage, high concrete manufacturing cost, and poor concrete strength, which are caused by poor performance. It also reduces the application obstacles when desert sand is introduced to replace industrial sand in concrete preparation, alleviates the shortage of industrial sand in the industry, thereby reducing the transportation cost of industrial sand raw materials and lowering the cost of concrete engineering.

[0189] The polycarboxylate superplasticizer for desert sand concrete provided by this invention has a simple production method, low production cost, and good social benefits.

[0190] 2. The present invention has the following novelty:

[0191] Desert sand is characterized by small particles and low gradation. Traditional desert sand concrete requires a large amount of polycarboxylate superplasticizer, resulting in poor water reduction effect, high cost, and low concrete strength during use. This invention patent, however, introduces different functional monomers to optimize and obtain a new type of polycarboxylate superplasticizer, thereby improving the water reduction effect and reducing the amount of superplasticizer required during the use of desert sand concrete, effectively saving costs.

[0192] Compared with traditional polycarboxylate superplasticizers, the polycarboxylate superplasticizer provided by this invention introduces high molecular weight functional monomers and adds anti-mud and reinforcing functional monomers, realizing the multi-functionality of polycarboxylate superplasticizers. It can be applied to desert sand concrete with low gradation, severe weathering and poor adsorption, so as to improve the strength of desert sand concrete, reduce the dosage of superplasticizer and reduce manufacturing costs.

[0193] The present invention provides a simple method for preparing desert sand concrete. It has a high water reduction rate when preparing mortar and concrete, the prepared mortar has low viscosity, and the mixture is uniform. This is beneficial for Northwest my country to select desert sand to replace all or part of the natural engineering sand in actual engineering projects, alleviate my country's demand for industrial sand, reduce transportation costs, and lower project costs. It has good market application prospects.

[0194] It should be noted that:

[0195] The specific parameters or some commonly used reagents or raw materials in the above embodiments are specific or preferred embodiments under the concept of the present invention, and are not intended to limit it; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.

[0196] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A polycarboxylate superplasticizer for desert sand concrete, characterized by: The modified polyether macromonomer is polymerized with unsaturated carboxylic acid and / or anhydride by free radical polymerization reaction; The structural formula of the modified polyether macromonomer is as follows: Wherein, R1, R2, R3 are each independently -H or -OH or halogen group or C1-C5 alkyl or C1-C5 alkoxy; R4 is -H or -OH or halogen group or C1-C5 alkyl or C1-C5 alkoxy or -NO2; R5 is -H or C1-C5 alkyl, and n is an integer of 50-2000.

2. The polycarboxylate superplasticizer for desert sand concrete according to claim 1, characterized in that: The modified polyether macromonomer is polymerized with unsaturated carboxylic acid and / or anhydride by free radical polymerization reaction under the action of an oxidizing agent, a reducing agent and a chain transfer agent to obtain the polycarboxylate superplasticizer; The free radical polymerization reaction temperature is 30-80℃; The weight ratio of the modified polyether macromonomer, the unsaturated carboxylic acid, the anhydride, the oxidizing agent and the chain transfer agent is (50-220):(0.2-40):(0.1-20):(1-10).

3. The polycarboxylate superplasticizer for desert sand concrete according to claim 2, characterized in that: The unsaturated carboxylic acid is at least one of acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate and ethyl methacrylate; The anhydride is at least one of maleic anhydride, fumaric anhydride, isophthalic anhydride and phthalic anhydride; The oxidizing agent is at least one of hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, cumene hydroperoxide, dibenzoyl peroxide, dihexyl peroxydicarbonate and tert-butyl hydroperoxide.

4. The polycarboxylate superplasticizer for desert sand concrete according to claim 2, characterized in that, The free radical polymerization reaction process is as follows: The modified polyether macromonomer, the first part of unsaturated carboxylic acid and / or the first part of anhydride and the oxidizing agent are dissolved in water to obtain a bottom solution; The second part of unsaturated carboxylic acid and / or the second part of anhydride is dissolved in water to obtain solution A; The reducing agent and the chain transfer agent are dissolved in water to obtain solution B; The bottom solution is heated to 30-80℃, and then the reaction temperature is kept at 30-80℃, solution A and solution B are added dropwise into the bottom solution for polymerization reaction, and after the addition is completed, the reaction is continued for a certain period of time; The dropping time of solution A and solution B is 1.0-4.5h respectively, and after the addition of solution A and solution B is completed, the reaction is continued for 0.5-5h; the total amount of the two parts of unsaturated carboxylic acid is the total amount of unsaturated carboxylic acid, and the total amount of the two parts of anhydride is the total amount of unsaturated carboxylic acid.

5. The polycarboxylate superplasticizer for desert sand concrete according to claim 2, characterized in that: The reducing agent is at least one of ascorbic acid, azobisimidozolin hydrochloride, sodium pyrosulfite, sodium sulfite, ferrous sulfate, sodium hypophosphite, sodium phosphite and ferrous ammonium sulfate; The chain transfer agent is a thiol chain transfer agent; The weight ratio of the total amount of the modified polyether macromonomer, the reducing agent, the chain transfer agent and water is (50-220):(2-10):(1-10):(100-250); and the amount of the oxidizing agent is 3.0%-10.0% of the total mass of the modified polyether macromonomer.

6. The polycarboxylate superplasticizer for desert sand concrete according to claim 1, characterized in that: The modified polyether macromonomer is prepared by a first condensation reaction of a polyether macromonomer and a p-ester benzoic acid compound in the presence of a catalyst; The p-ester benzoic acid compound has the following structural formula: ， R1, R2, and R3 are each independently -H, -OH, a halogen group, a C1-C5 alkyl group, or a C1-C5 alkoxy group; and R4 is -H, -OH, a halogen group, a C1-C5 alkyl group, a C1-C5 alkoxy group, or -NO2. The polyether macromonomer has the following structural formula: R5 is -H or a C1-C5 alkyl group; and n is an integer from 50 to 2000.

7. The polycarboxylate superplasticizer for desert sand concrete according to claim 6, characterized in that: The p-ester benzoic acid compound is prepared by a second condensation reaction of p-hydroxybenzoic acid and a p-benzoic acid compound in the presence of a catalyst; The p-hydroxybenzoic acid has the following structural formula: ； The p-benzoic acid compound has the following structural formula: R1, R2, and R3 are each independently -H, -OH, a halogen group, a C1-C5 alkyl group, or a C1-C5 alkoxy group; and R4 is -H, -OH, a halogen group, a C1-C5 alkyl group, a C1-C5 alkoxy group, or -NO2.

8. The polycarboxylic acid water reducer for desert sand concrete according to claim 7, characterized in that: The molar ratio of the polyether macromonomer to the p-ester benzoic acid compound is 1:(1-10), the reaction temperature of the first condensation reaction is 40-180°C, and the reaction time is 5-210 min; The molar ratio of the p-hydroxybenzoic acid to the p-benzoic acid compound is (1-10):(1-10), the reaction temperature of the second condensation reaction is 40-180°C, and the reaction time is 10-210 min; The catalyst is concentrated sulfuric acid.

9. A method for preparing the polycarboxylate superplasticizer for desert sand concrete according to any one of claims 1-8, characterized in that, The method comprises the following steps: The modified polyether macromonomer, the first part of unsaturated carboxylic acid and / or the first part of acid anhydride, and an oxidizing agent are dissolved in water to obtain a bottom solution; The second part of unsaturated carboxylic acid and / or the second part of acid anhydride are dissolved in water to obtain solution A; A reducing agent and a chain transfer agent are dissolved in water to obtain solution B; The bottom solution is heated to 30-80°C, and then the reaction temperature is kept at 30-80°C, solution A and solution B are added dropwise into the bottom solution for polymerization, and after the dropwise addition is completed, the reaction is continued for a certain period of time; The dropwise addition time of solution A and solution B is 1.0-4.5 h respectively, and after the dropwise addition of solution A and solution B is completed, the reaction is continued for 0.5-5 h; the total amount of the two parts of unsaturated carboxylic acid is equal to the total amount of unsaturated carboxylic acid, and the total amount of the two parts of acid anhydride is equal to the total amount of unsaturated carboxylic acid.

10. A desert sand concrete, characterized by: The raw material components include desert sand, cement, and the polycarboxylic acid water reducer according to any one of claims 1-8.

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