阅读说明：本技术 一种大体积混凝土用聚羧酸减水剂及其制备方法 (Polycarboxylic acid water reducing agent for mass concrete and preparation method thereof ) 是由 林艳梅 朱少宏 官梦芹 林晓琛 方云辉 柯余良 姚文杰 安小强 于 2021-08-13 设计创作，主要内容包括：本发明涉及混凝土外加剂技术领域,特别涉及一种大体积混凝土用聚羧酸减水剂及其制备方法。该大体积混凝土用聚羧酸减水剂,其由聚醚大单体、丙烯酸、水化热调控功能材料共聚制得；其中,所述水化热调控功能材料包含纳米材料和不饱和酯类单体；所述不饱和酯类单体由马来酸酐与降解处理后的降解淀粉经酯化反应制得；所述纳米材料由烷氧基硅烷水溶液于乙醇钙溶液中经熟化制得。该聚羧酸减水剂能够有效降低混凝土水化热,同时对混凝土凝结时间和早期强度影响较小,可控制大体积混凝土缺陷裂缝的产生,提高其结构的服役寿命,减少其结构的维护成本；通过掺加该聚羧酸减水剂的方式来抑制热裂缝,具有简单高效、经济性强等优点。(The invention relates to the technical field of concrete admixtures, in particular to a polycarboxylic acid water reducing agent for mass concrete and a preparation method thereof. The polycarboxylic acid water reducing agent for the mass concrete is prepared by copolymerizing a polyether macromonomer, acrylic acid and a hydration heat regulation functional material; wherein the hydration heat regulation and control functional material comprises a nano material and an unsaturated ester monomer; the unsaturated ester monomer is prepared by esterification reaction of maleic anhydride and degraded starch after degradation treatment; the nanometer material is prepared by curing an alkoxy silane water solution in a calcium ethoxide solution. The polycarboxylate superplasticizer can effectively reduce the hydration heat of concrete, has small influence on the setting time and the early strength of the concrete, can control the generation of mass concrete defect cracks, prolongs the service life of the structure, and reduces the maintenance cost of the structure; the hot crack is inhibited by adding the polycarboxylate superplasticizer, and the method has the advantages of simplicity, high efficiency, strong economy and the like.)

1. The utility model provides a polycarboxylate water reducing agent for bulky concrete which characterized in that: prepared by copolymerizing polyether macromonomer, acrylic acid and hydration heat regulating functional materials;

wherein the hydration heat regulation and control functional material comprises a nano material and an unsaturated ester monomer;

the unsaturated ester monomer is prepared by esterification reaction of maleic anhydride and degraded starch after degradation treatment;

the nanometer material is prepared by curing an alkoxy silane water solution in a calcium ethoxide solution.

2. A polycarboxylic acid water reducing agent for mass concrete according to claim 1,

the calcium ethoxide solution is prepared by reacting metal calcium with an ethanol solution, and the reaction temperature is 75-85 ℃;

the curing is carried out at a temperature of 70 ℃ to 90 ℃.

3. The polycarboxylic acid water reducing agent for mass concrete according to claim 2, wherein the alkoxy silane is one or more of tetraethoxy silane, vinyl triacetoxy silane and gamma-aminopropyl triethoxy silane;

the molar ratio of the metallic calcium to the ethanol solution to the alkoxy silane is 1 (1.1-1.2) to 1.2-1.4.

4. The polycarboxylic acid water reducer for mass concrete according to claim 1, wherein the degraded starch is prepared by performing enzymolysis treatment on starch by amylase;

the enzymolysis treatment conditions are that the pH value is 5.5-6.5 and the enzymolysis temperature is 45-55 ℃.

5. The polycarboxylic acid water reducer for mass concrete according to claim 1, wherein the unsaturated ester monomer is prepared by mixing, grinding and esterifying maleic anhydride and degraded starch in sequence.

6. A polycarboxylic acid water reducing agent for mass concrete according to claim 4,

the mass ratio of the starch to the maleic anhydride is (90-110) to (15-25);

the esterification reaction temperature is 125-140 ℃.

7. The polycarboxylic acid water reducer for the large-volume concrete according to claim 1, wherein the mass ratio of the nano material to the unsaturated ester monomer is 1 (1-5).

8. The polycarboxylic acid water reducing agent for mass concrete according to claim 1, wherein the polyether macromonomer is one or more of a combination of isobutylene alcohol polyoxyethylene ether, hydroxybutyl vinyl polyethylene glycol ether and ethoxy vinyl polyethylene glycol ether;

the mass ratio of the polyether macromonomer, the acrylic acid and the hydration heat function regulating material is (10-15) to (15-25) 100.

9. A preparation method of a polycarboxylic acid water reducer for mass concrete according to any one of claims 1 to 8, characterized by comprising the following preparation steps:

s100, preparing a nano material:

s110, reacting metal calcium with an ethanol solution at the temperature of 75-85 ℃ to obtain a calcium ethoxide solution;

s120, dripping an alkoxy silane water solution into the calcium ethoxide solution, and reacting and curing for a certain time at the temperature of 70-90 ℃ after finishing dripping;

s130, placing the product obtained in the step S120 at normal temperature for a certain time, and performing dialysis treatment to obtain a nano material;

s200, preparing unsaturated ester monomers and hydration heat regulation functional materials;

s210, degrading starch to obtain degraded starch;

s220, mixing and grinding the degraded starch and maleic anhydride, and carrying out esterification reaction at the temperature of 125-140 ℃ to obtain unsaturated ester monomers;

s230, mixing the unsaturated ester monomer and the nano material to prepare a hydration heat regulation functional material;

s300, carrying out copolymerization reaction on the polyether macromonomer, the acrylic acid and the hydration heat regulation and control functional material to obtain the polycarboxylic acid water reducer for the mass concrete.

10. The preparation method of the polycarboxylic acid water reducer for mass concrete according to claim 9, wherein in S210, starch is dissolved to prepare starch slurry, the pH value of the slurry is adjusted, and then amylase is added to carry out enzymolysis treatment on the starch slurry to obtain degraded starch;

before S220, adding an acidic reagent into the product obtained in S210 to adjust the pH value to 2-3, and after enzyme deactivation treatment for at least 30min, adding an alkaline reagent to adjust the pH value to be neutral.

Technical Field

The invention relates to the technical field of concrete admixtures, in particular to a polycarboxylic acid water reducing agent for mass concrete and a preparation method thereof.

Background

With the continuous and rapid development of the building industry in China, the demand and the application amount of mass concrete are gradually increased year by year. However, a large amount of hydration heat is generated after the concrete is poured, heat is not dissipated in time due to the low thermal conductivity of the concrete material, and the internal temperature is constantly increased due to the generated hydration heat. When the temperature reaches a peak and then decreases, the concrete will develop thermal shrinkage and shrinkage stresses. When the shrinkage stress is greater than the tensile stress, cracks are formed, thereby destroying the usability, load-bearing capacity, safety, durability, and the like of the member. Therefore, mass concrete engineering poses higher challenges and requirements on its core technology, concrete thermal crack control.

The traditional measures for inhibiting the hot cracks comprise block pouring, cooling water pipe pre-burying, surface laying of a heat insulation layer and the like, but the measures have the problems of high energy consumption, high cost, high construction difficulty and the like, and the application of the measures is limited.

In recent years, researchers propose that hot cracks are inhibited by adding hydration heat regulating materials, the hydration heat regulating materials can reduce the No. 2 heat release peak value and accumulated heat release of cement hydration, or can absorb partial hydration heat to reduce temperature gradient, so that the risk of concrete shrinkage cracking is reduced, and the method has the advantages of simplicity, high efficiency, high economy and the like, and is gradually a research hotspot at home and abroad.

At present, hydration heat regulating materials are various, urea and saccharides (derivatives) have excellent hydration heat regulating effects, and in recent years, amylodextrin and phase change materials are emerging continuously, so that the influence on the safety of concrete can be reduced, and the development potential is huge. In addition, medium and low heat cement, fly ash, phosphorous slag, and steel slag have been studied in a great deal as materials used earlier, and other types of materials are also receiving increasing attention.

The hydration heat regulating material is a new method for controlling the hydration temperature rise of concrete, has the advantages of simplicity, effectiveness, strong economy and the like, and gradually becomes a research hotspot at home and abroad. However, the hydration heat regulation material has the problems of reducing the early strength of concrete, delaying the setting time of concrete and the like, and limits the application of the hydration heat regulation material in engineering cast-in-place structural concrete. Therefore, the development of a water reducing agent which has a good dispersing function, can obviously reduce the hydration heat release rate of cement and has small influence on the setting time and the early strength of concrete is urgently needed in the market.

The application number is 201910904317.0, Chinese patent application with the publication date of 2019, 12 and 24 discloses a preparation method of a polycarboxylate superplasticizer with hydration heat regulation and control effects, wherein carboxymethyl starch with the substitution degree of 0.3-0.5 and better water solubility is introduced, and is subjected to series of treatments such as pyrolysis, acidolysis, enzymolysis and the like, and then is subjected to esterification reaction with unsaturated hydroxy ester monomers to obtain modified CMS monomers for synthesizing the polycarboxylate superplasticizer; the water reducing agent can ensure that the hydration reaction of cement is gradually and stably carried out, effectively reduce the hydration heat release rate of the cement, reduce the temperature peak of concrete, delay the appearance of the temperature peak value and reduce the risk of concrete cracking. The polycarboxylate water reducer prepared by the invention can delay the temperature peak of concrete for more than 20 hours, reduce the temperature peak of concrete for more than 6 ℃, improve the 28d compressive strength of concrete by not less than 10%, has good cement adaptability, can improve the workability of concrete, has simple preparation process and is beneficial to large-scale industrial production, but the early strength of concrete can be reduced by delaying the temperature peak of concrete and reducing the temperature peak of concrete, and the setting time of concrete is prolonged.

Disclosure of Invention

To solve the problems mentioned in the background art: the traditional measures for inhibiting the hot cracks, such as block pouring, cooling water pipe pre-embedding, surface laying of an insulating layer and the like, have the problems of high energy consumption, high cost, high construction difficulty and the like; the existing hydration heat regulation material can control the hydration temperature rise of concrete, but has the problems of reducing the early strength of the concrete, delaying the setting time of the concrete and the like. The invention provides a polycarboxylate superplasticizer which can be applied to mass concrete engineering in a large scale, can effectively reduce hydration heat, has small influence on the setting time and early strength of concrete, can control the generation of mass concrete defect cracks, prolongs the service life of the structure, and reduces the maintenance cost of the structure.

The invention provides a polycarboxylic acid water reducing agent for mass concrete, which is prepared by copolymerizing a polyether macromonomer, acrylic acid and a hydration heat regulation functional material; wherein the hydration heat regulation and control functional material comprises a nano material and an unsaturated ester monomer; the unsaturated ester monomer is prepared by esterification reaction of maleic anhydride and degraded starch after degradation treatment; the nano material is prepared by curing an alkoxy silane water solution in a calcium ethoxide solution;

the polycarboxylic acid water reducer for the mass concrete, provided by the invention, contains a large amount of hydroxyl and carboxyl in unsaturated acid ester generated by introducing maleic anhydride and starch subjected to enzymolysis modification treatment in a molecular structure, so that the quantity of the hydroxyl and carboxyl in the molecular structure of the water reducer is increased, the polycarboxylic acid water reducer has higher molecular weight, more functional group quantity and larger molecular coil, and is easy to complex Ca²⁺The concentration of free ions is reduced, and the hydration process of cement is hindered; in addition, the polycarboxylate superplasticizer slowly releases sugar chains under alkaline conditions to continuously slow down the hydration of cement, thereby effectively reducing the hydration heat of concrete;

meanwhile, the water reducer provided by the invention contains a nano material, the nano material is prepared by dripping an alkoxy silane water solution into an ethanol calcium solution and performing reaction curing, the prepared nano material is a mucilaginous substance, and a C-S-H structure in bond connection is formed in the mucilaginous substance, so that the development of the early strength of a cement-based material, particularly 6-12H after hydration can be promoted, but the maximum heat release rate in an accelerated period is not greatly influenced, the influence on the total hydration heat is small, the concrete strength is effectively improved on the premise of not obviously increasing the early hydration heat, and the problems of the early strength reduction of the concrete and the prolonging of the setting time after the hydration heat is reduced can be solved. The prepared polycarboxylate superplasticizer can effectively control the temperature rise of large-volume engineering concrete, prevent cracking, has no influence on the early strength and the setting time of the concrete, and prolongs the service life of the concrete.

Further, the calcium ethoxide solution is prepared by reacting metal calcium with an ethanol solution, and the reaction temperature is 75-85 ℃; the curing is carried out at a temperature of 70 ℃ to 90 ℃.

Further, the alkoxy silane is one or more of tetraethoxy silane, vinyl triacetoxy silane and gamma-aminopropyl triethoxy silane; the molar ratio of the metallic calcium to the ethanol solution to the alkoxy silane is 1 (1.1-1.2) to 1.2-1.4.

Further, the degraded starch is prepared by performing enzymolysis treatment on starch by using amylase; the enzymolysis treatment conditions are that the pH value is 5.5-6.5 and the enzymolysis temperature is 45-55 ℃.

Further, the unsaturated ester monomer is prepared by mixing, grinding and esterifying maleic anhydride and degraded starch in sequence.

Further, the mass ratio of the starch to the maleic anhydride is (90-110) to (15-25); the esterification reaction temperature is 125-140 ℃.

Furthermore, the mass ratio of the nano material to the unsaturated ester monomer is 1 (1-5).

Further, the polyether macromonomer is one or a combination of more of isobutylene alcohol polyoxyethylene ether, hydroxybutyl vinyl polyglycol ether and ethoxy vinyl polyglycol ether; the mass ratio of the polyether macromonomer, the acrylic acid and the hydration heat function regulating material is (10-15) to (15-25) 100.

The invention also provides a preparation method of the polycarboxylic acid water reducer for the mass concrete, which comprises the following preparation steps:

s100, preparing a nano material:

s110, reacting metal calcium with an ethanol solution at the temperature of 75-85 ℃ to obtain a calcium ethoxide solution;

s120, dripping an alkoxy silane water solution into the calcium ethoxide solution, and reacting and curing for a certain time at the temperature of 70-90 ℃ after finishing dripping;

s130, placing the product obtained in the step S120 at normal temperature for a certain time, and performing dialysis treatment to obtain a nano material;

s200, preparing unsaturated ester monomers and hydration heat regulation functional materials;

s210, degrading starch to obtain degraded starch;

s220, mixing and grinding the degraded starch and maleic anhydride, and carrying out esterification reaction at the temperature of 125-140 ℃ to obtain unsaturated ester monomers;

s230, mixing the unsaturated ester monomer and the nano material to prepare a hydration heat regulation functional material;

s300, carrying out copolymerization reaction on the polyether macromonomer, the acrylic acid and the hydration heat regulation and control functional material to obtain the polycarboxylic acid water reducer for the mass concrete.

Further, in S210, dissolving starch in water to prepare starch slurry, adjusting the pH value of the slurry, and then adding amylase to carry out enzymolysis treatment on the starch slurry to obtain degraded starch;

and before S220, adding an acidic reagent into the product obtained in S210 to adjust the pH value to 2-3, and after enzyme deactivation treatment for at least 30min, adding an alkaline reagent to adjust the pH value to be neutral.

Compared with the prior art, the polycarboxylic acid water reducer for the mass concrete provided by the invention has the following technical effects:

the concrete hydration heat can be effectively reduced, the influence on the concrete setting time and the early strength is small, the generation of mass concrete defect cracks can be controlled, the service life of the structure is prolonged, and the maintenance cost of the structure is reduced; the hot crack is inhibited by adding the polycarboxylate superplasticizer, and the method has the advantages of simplicity, high efficiency, strong economy and the like.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the following description will clearly and completely describe the embodiments of the present invention, and obviously, the described embodiments are a part of the embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a polycarboxylic acid water reducing agent for mass concrete, which is prepared by copolymerizing a polyether macromonomer, acrylic acid and a hydration heat regulation functional material; the hydration heat regulation and control functional material comprises a nano material and an unsaturated ester monomer; the unsaturated ester monomer is prepared by esterification reaction of maleic anhydride and degraded starch after degradation treatment; the nano material is prepared by curing an alkoxy silane water solution in a calcium ethoxide solution;

the method comprises the following steps of (1) degrading starch to obtain the degraded starch, wherein chemical bonds of a starch molecular chain after degradation are partially broken to shorten the starch molecular chain, and the degradation treatment is an existing starch degradation treatment method, including but not limited to pyrolysis, enzymolysis, acidolysis and other degradation treatment methods;

the invention also provides a preparation method of the polycarboxylic acid water reducing agent for the mass concrete, which comprises the following steps: the preparation method comprises the following preparation steps:

s100, preparing a nano material:

s110, reacting metal calcium with an ethanol solution at the temperature of 75-85 ℃ to obtain a calcium ethoxide solution;

s120, dripping an alkoxy silane water solution into the calcium ethoxide solution, and reacting and curing for 1-3 h at the temperature of 70-90 ℃ after finishing dripping;

s130, placing the product obtained in the step S120 at normal temperature for 12-24 hours, and performing dialysis treatment to obtain a nano material;

s200, preparing unsaturated ester monomers and hydration heat regulation functional materials;

s210, degrading starch to obtain degraded starch;

s220, mixing and grinding the degraded starch and maleic anhydride, and carrying out esterification reaction at the temperature of 125-140 ℃ to obtain unsaturated ester monomers;

s230, mixing the unsaturated ester monomer and the nano material to prepare a hydration heat regulation functional material;

s300, carrying out copolymerization reaction on the polyether macromonomer, the acrylic acid and the hydration heat regulation and control functional material to obtain the polycarboxylic acid water reducer for the mass concrete.

Preferably, in an embodiment, in S210, starch is dissolved in water to prepare starch slurry, the pH value of the slurry is adjusted, and then amylase is added to perform enzymolysis on the starch slurry to obtain degraded starch;

preferably, in one embodiment, before performing S220, an acidic reagent is added to the product obtained in S210 to adjust the pH to 2-3, and after at least 30min of enzyme deactivation, an alkaline reagent is added to adjust the pH to be neutral.

Preferably, in an embodiment, in S230, the hydration heat regulating functional material is prepared by ball-milling and pulverizing the unsaturated ester monomer in advance, and mixing with the nanomaterial.

Wherein, for the preparation of the nano material: preferably, in one embodiment, the alkoxysilane is one or more of tetraethoxysilane, vinyltriacetoxysilane, gamma-aminopropyltriethoxysilane; preferably, the alkoxysilane is tetraethoxysilane.

Preferably, in one embodiment, the molar ratio of the metallic calcium to the ethanol solution to the alkoxy silane is 1 (1.1-1.2) to 1.2-1.4.

Preferably, in one embodiment, during the dialysis treatment, sodium hydroxide solution is used as dialysate, and the pore diameter of the dialysis membrane is 300-600 nm; the nanometer material is prepared by reacting and curing an alkoxy silane water solution in a calcium ethoxide solution, and then the nanometer material with the nanometer size is obtained by sequentially standing at normal temperature, dialyzing and purifying.

Wherein, for the preparation of unsaturated ester monomers:

preferably, in one embodiment, the starch is one or more of corn starch and tapioca flour; preferably, the starch is corn starch.

Preferably, in one embodiment, the amylase may be selected from one or more combinations of moderate temperature alpha-amylase, beta-amylase; preferably, the amylase is a mesophilic alpha-amylase. The intermediate temperature alpha-amylase and beta-amylase are the existing amylases.

Preferably, in one embodiment, the mass ratio of the starch to the maleic anhydride is (90-110): 15-25);

wherein, for the preparation of unsaturated ester monomers: preferably, in an embodiment, the mass ratio of the nanomaterial and the unsaturated ester monomer contained in the hydration heat regulation functional material is 1 (1-5).

Wherein, for the preparation of the polycarboxylic acid water reducing agent for the large-volume concrete:

preferably, in one embodiment, the polyether macromonomer is one or more of the group consisting of a polyoxyethylene methacrylate, hydroxybutyl vinyl polyglycol ether and ethoxyvinyl polyglycol ether; preferably, the polyether macromonomer is isobutylene alcohol polyoxyethylene ether;

preferably, in one embodiment, the mass ratio of the polyether macromonomer, the acrylic acid and the hydration heat function regulating material is 100 (10-15): 15-25.

Preferably, in one embodiment, an initiator and a molecular regulator are also added in the copolymerization reaction; the initiator can be a water-soluble redox initiation system, such as hydrogen peroxide-sodium formaldehyde sulfoxylate (sodium formaldehyde sulfoxylate) and the like; the molecular weight regulator may be selected from at least one of thioglycolic acid, mercaptopropionic acid, mercaptoethanol, isopropanol, sodium hypophosphite, trisodium phosphate, sodium formate, sodium acetate, and dodecanethiol.

The invention also provides the following examples and comparative examples:

example 1

(1) Adding metal calcium and ethanol into a four-neck flask, starting a stirring paddle to stir, reacting for 4 hours at a reflux temperature, dripping tetraethoxysilane aqueous solution, wherein the mass concentration of the tetraethoxysilane aqueous solution is 90%, the dripping time is 4 hours, reacting and curing for 1 hour after dripping is finished, standing for 24 hours at normal temperature, dialyzing for 3 days in calcium hydroxide solution, and replacing the calcium hydroxide solution every 6 hours to obtain the nano material.

Wherein the molar ratio of the metal calcium to the ethanol to the tetraethoxysilane is 1: 1.1: 1.2, the addition amount of the tetraethoxysilane is 20 mol; the dialysis membrane is a dialysis membrane with the aperture of 300 nm;

(2) mixing 100g of corn starch with water to form slurry with the mass concentration of 30%, then adjusting the pH value of the system to 6 by using 30% sulfuric acid, adding 10g of medium-temperature alpha-amylase, and carrying out heat preservation and hydrolysis for 4h at 50 ℃; regulating the pH value of the system to 2-3 by using 30% sulfuric acid, inactivating enzyme for 30min, and regulating the pH value to be neutral by using a saturated sodium hydroxide solution; adding 20g of maleic anhydride, placing the mixture in a mortar, mixing and grinding the mixture evenly, transferring the mixture into a round-bottom flask, placing the round-bottom flask into an oil bath, heating the mixture to 135 ℃, stirring the mixture by a stirring paddle simultaneously, reacting for 3 hours, and stopping heating. Taking out the reactants after cooling, and grinding the reactants by using a ball mill to prepare unsaturated ester monomers; and (3) adding 60g of the nano material prepared in the step (1) and 100g of unsaturated ester monomer, and mixing to obtain the hydration heat regulation functional material.

(3) Adding 100g of isobutylene alcohol polyoxyethylene ether, 20g of the hydration heat regulation functional material, 1g of hydrogen peroxide and water into a reaction kettle, controlling the temperature to be 40 ℃, then respectively dropwise adding a sodium formaldehyde sulfoxylate aqueous solution, a thioglycolic acid aqueous solution and an acrylic acid aqueous solution within 3h, and preserving heat for 1h after dropwise adding is finished to obtain a reaction product with the concentration of 50%; adjusting the pH of the reaction product to 6.0-7.0 by using sodium hydroxide to obtain a polycarboxylic acid water reducing agent;

wherein 0.5g of sodium formaldehyde sulfoxylate aqueous solution is dissolved in 150g of water, 0.5g of thioglycolic acid aqueous solution is dissolved in 150g of water, and 10g of acrylic acid aqueous solution is dissolved in 180g of water. The molecular weight of the isobutylene alcohol polyoxyethylene ether is 3000.

Example 2

(1) Adding metal calcium and ethanol into a four-neck flask, starting a stirring paddle to stir, reacting for 3 hours at a reflux temperature, dripping tetraethoxysilane aqueous solution, wherein the mass concentration of the tetraethoxysilane aqueous solution is 90%, the dripping time is 3 hours, reacting and curing for 2 hours after dripping is finished, standing for 18 hours at normal temperature, dialyzing for 3 days in calcium hydroxide solution, and replacing the calcium hydroxide solution every 6 hours to obtain the nano material.

Wherein the molar ratio of the metal calcium to the ethanol to the tetraethoxysilane is 1: 1.1: 1.3, the addition amount of the tetraethoxysilane is 30 mol; the dialysis membrane is a dialysis membrane with the aperture of 500 nm;

(2) mixing 100g of corn starch with water to form slurry with the mass concentration of 30%, then adjusting the pH value of the system to 6 by using 30% sulfuric acid, adding 10g of medium-temperature alpha-amylase, and carrying out heat preservation and hydrolysis for 4h at 50 ℃; regulating the pH value of the system to 2-3 by using 30% sulfuric acid, inactivating enzyme for 30min, and regulating the pH value to be neutral by using a saturated sodium hydroxide solution; adding 25g of maleic anhydride, placing the mixture in a mortar, mixing and grinding the mixture evenly, transferring the mixture into a round-bottom flask, placing the round-bottom flask into an oil bath, heating the mixture to 130 ℃, stirring the mixture by a stirring paddle simultaneously, reacting for 3 hours, and stopping heating. Taking out the reactants after cooling, and grinding the reactants by using a ball mill to prepare unsaturated ester monomers; and (3) adding 60g of the nano material prepared in the step (1) and 60g of unsaturated ester monomers to mix to obtain the hydration heat regulation functional material.

(3) Adding 100g of isobutylene alcohol polyoxyethylene ether, 15g of the hydration heat regulation functional material, 1g of hydrogen peroxide and water into a reaction kettle, controlling the temperature to be 40 ℃, then respectively dropwise adding a sodium formaldehyde sulfoxylate aqueous solution, a thioglycolic acid aqueous solution and an acrylic acid aqueous solution within 3h, and preserving heat for 1h after dropwise adding is finished to obtain a reaction product with the concentration of 50%; adjusting the pH of the reaction product to 6.0-7.0 by using sodium hydroxide to obtain a polycarboxylic acid water reducing agent;

wherein 0.5g of sodium formaldehyde sulfoxylate aqueous solution is dissolved in 150g of water, 0.5g of thioglycolic acid aqueous solution is dissolved in 150g of water, and 15g of acrylic acid aqueous solution is dissolved in 180g of water. The molecular weight of the isobutylene alcohol polyoxyethylene ether is 2400.

Comparative example 1

(1) Adding metal calcium and ethanol into a four-neck flask, starting a stirring paddle to stir, reacting for 4 hours at a reflux temperature, dripping tetraethoxysilane aqueous solution, wherein the mass concentration of the tetraethoxysilane aqueous solution is 90%, the dripping time is 4 hours, reacting and curing for 1 hour after dripping is finished, standing for 24 hours at normal temperature, dialyzing for 3 days in calcium hydroxide solution, and replacing the calcium hydroxide solution every 6 hours to obtain the nano material;

wherein the molar ratio of the metal calcium to the ethanol to the tetraethoxysilane is 1: 1.1: 1.2, the addition amount of the tetraethoxysilane is 20 mol; the dialysis membrane is a dialysis membrane with the aperture of 300 nm;

(2) adding 100g of isobutylene polyoxyethylene ether, 20g of the nano material, 1g of hydrogen peroxide and water into a reaction kettle, controlling the temperature to be 40 ℃, then respectively dropwise adding a sodium formaldehyde sulfoxylate aqueous solution, a thioglycolic acid aqueous solution and an acrylic acid aqueous solution within 3h, and preserving heat for 1h after dropwise adding is finished to obtain a reaction product with the concentration of 50%; and adjusting the pH of the reaction product to 6.0-7.0 by using sodium hydroxide to obtain the polycarboxylic acid water reducer.

Wherein 0.5g of sodium formaldehyde sulfoxylate aqueous solution is dissolved in 150g of water, 0.5g of thioglycolic acid aqueous solution is dissolved in 150g of water, and 10g of acrylic acid aqueous solution is dissolved in 180g of water. The molecular weight of the isobutylene alcohol polyoxyethylene ether is 3000.

Comparative example 2

(1) Mixing 100g of corn starch with water to form slurry with the mass concentration of 30%, then adjusting the pH value of the system to 6 by using 30% sulfuric acid, adding 10g of medium-temperature alpha-amylase, and carrying out heat preservation and hydrolysis for 4h at 50 ℃; regulating the pH value of the system to 2-3 by using 30% sulfuric acid, inactivating enzyme for 30min, and regulating the pH value to be neutral by using a saturated sodium hydroxide solution; adding 20g of maleic anhydride, placing the mixture in a mortar, mixing and grinding the mixture evenly, transferring the mixture into a round-bottom flask, placing the round-bottom flask into an oil bath, heating the mixture to 135 ℃, stirring the mixture by a stirring paddle simultaneously, reacting for 3 hours, and stopping heating. And taking out the reactant after cooling, and grinding the reactant by using a ball mill to obtain the hydration heat regulation functional material.

(2) Adding 100g of isobutylene alcohol polyoxyethylene ether, 20g of the hydration heat regulation functional material, 1g of hydrogen peroxide and water into a reaction kettle, controlling the temperature to be 40 ℃, then respectively dropwise adding a sodium formaldehyde sulfoxylate aqueous solution, a thioglycolic acid aqueous solution and an acrylic acid aqueous solution within 3h, and preserving heat for 1h after dropwise adding is finished to obtain a reaction product with the concentration of 50%; adjusting the pH of the reaction product to 6.0-7.0 by using sodium hydroxide to obtain a polycarboxylic acid water reducing agent;

wherein 0.5g of sodium formaldehyde sulfoxylate aqueous solution is dissolved in 150g of water, 0.5g of thioglycolic acid aqueous solution is dissolved in 150g of water, and 10g of acrylic acid aqueous solution is dissolved in 180g of water. The molecular weight of the isobutylene alcohol polyoxyethylene ether is 3000.

Comparative example 3

(1) Alkoxysilane additive: preparing tetraethoxysilane into a solution with the mass concentration of 95%, wherein the solvent adopts water;

(2) mixing 100g of corn starch with water to form slurry with the mass concentration of 30%, then adjusting the pH value of the system to 6 by using 30% sulfuric acid, adding 10g of medium-temperature alpha-amylase, and carrying out heat preservation and hydrolysis for 4h at 50 ℃; regulating the pH value of the system to 2-3 by using 30% sulfuric acid, inactivating enzyme for 30min, and regulating the pH value to be neutral by using a saturated sodium hydroxide solution; adding 20g of maleic anhydride, placing the mixture in a mortar, mixing and grinding the mixture evenly, transferring the mixture into a round-bottom flask, placing the round-bottom flask into an oil bath, heating the mixture to 135 ℃, stirring the mixture by a stirring paddle simultaneously, reacting for 3 hours, and stopping heating. Taking out the reactants after cooling, and grinding the reactants by using a ball mill to prepare unsaturated ester monomers; and (3) adding 60g of tetraethoxysilane solution prepared in the step (1) and 100g of unsaturated ester monomers to mix to obtain the hydration heat regulation functional material.

(3) Adding 100g of isobutylene alcohol polyoxyethylene ether, 20g of the hydration heat regulation functional material, 1g of hydrogen peroxide and water into a reaction kettle, controlling the temperature to be 40 ℃, then respectively dropwise adding a sodium formaldehyde sulfoxylate aqueous solution, a thioglycolic acid aqueous solution and an acrylic acid aqueous solution within 3h, and preserving heat for 1h after dropwise adding is finished to obtain a reaction product with the concentration of 50%; adjusting the pH of the reaction product to 6.0-7.0 by using sodium hydroxide to obtain a polycarboxylic acid water reducing agent;

wherein, the sodium formaldehyde sulfoxylate aqueous solution is 0.5g of sodium formaldehyde sulfoxylate dissolved in 150g of water, the thioglycolic acid aqueous solution is 0.5g of thioglycolic acid dissolved in 150g of water, and the acrylic acid aqueous solution is 10g of acrylic acid solution dissolved in 180g of water; the molecular weight of the isobutylene alcohol polyoxyethylene ether is 3000.

The polycarboxylic acid water reducing agent prepared in the embodiment and the comparative example is tested according to the related indexes of JCT 2608-:

the Fujian ordinary portland cement is adopted, and the concrete mixing proportion is as follows: cement 360kg/m³790kg/m of sand³1060kg/m of stones³162kg/m of water³The polycarboxylic acid water reducing agents prepared in the examples and the comparative examples were subjected to a performance test according to a folding mixing amount of 0.2%, and the test results are shown in table 1;

wherein, comparative example 4 is a reference sample, and the concrete mixing ratio thereof is the same as that of example 1, except that no polycarboxylic acid water reducing agent is added to the base sample.

TABLE 1

The results in Table 1 show that the polycarboxylate superplasticizer prepared by the embodiment of the invention can effectively reduce the hydration heat of concrete, the hydration heat reduction rate in 24 hours is as high as 55%, and the influence on the setting time and the early strength of the concrete is small, and the initial setting time and the 1d compressive strength are basically unchanged compared with the reference sample; therefore, the method can effectively control the generation of the large-volume concrete defect crack, improve the service life of the structure and reduce the maintenance cost of the structure.

Compared with the embodiment, the 24-hour hydration heat reduction rate of the comparative example 1 is-0.3%, and the effect of effectively reducing the hydration heat of the concrete cannot be achieved; in the comparative example 2, although the reduction rate of 24h hydration heat is up to 50 percent through testing, the initial setting time is up to 420min, the 1d compressive strength is only 12.4MPa and is obviously smaller than the 1d compressive strength values of the basic sample and the embodiment of the invention, the problems of reducing the early strength of concrete, delaying the setting time of concrete and the like still exist in the comparative example 1, and the application of the concrete in the cast-in-place structure concrete of the engineering is limited; in comparative example 3, the alkoxysilane solution used as an additive did not have significant effects on improving the early strength of concrete and shortening the setting time of concrete.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.