A composite water reducer for suppressing reaction bubbles of fly ash in concrete, its preparation method and application

Abstract

The present invention relates to the technical field of concrete additives, and specifically discloses a composite water reducer for inhibiting reaction bubbles of fly ash in concrete. By weight, 1000 parts of the composite water reducer are composed of the following raw materials: 100-350 parts of polycarboxylic acid water reducing mother liquor, 50-250 parts of polycarboxylic acid slump retaining mother liquor, 0-55 parts of retarder, 0-0.2 parts of air-entraining agent, 0-0.3 parts of defoaming agent, 10-40 parts of inhibitor, 0-10 parts of water retention and thickening agent, and the balance is water; the inhibitor is one or more of ferrous sulfate, copper sulfate, magnesium sulfate, and zinc sulfate. The composite water reducer for inhibiting reaction bubbles of fly ash in concrete according to the present invention can inhibit the generation of bubbles in concrete due to the reaction under the alkaline condition of denitrification fly ash, improve the apparent quality and strength of concrete precast beams and fair-faced concrete, and is beneficial to expanding the application of denitrification fly ash in concrete.

Description

Technical Field

[0001] The invention relates to the technical field of concrete additives, and in particular to a composite water reducing agent for inhibiting concrete fly ash reaction bubbles, and a preparation method and application thereof. Background Art

[0002] Polycarboxylic acid-based high-efficiency water reducers are the latest generation of dispersants in the concrete industry. Compared with the previous lignin, wood calcium sulfonate and naphthalene-based water reducers, polycarboxylic acid-based water reducers have lower dosage and higher water reduction rate, which can usually reach 30-40%, or even higher. Polycarboxylic acid-based water reducers have a strong polar main chain and hydrophilic side chains of a certain length and number. The molecular structure is comb-shaped, and the outward-extending comb structure supported by numerous side chains provides sufficient spatial arrangement effect for the further dispersion of cement particles. Compared with the double-layer electrical repulsion of naphthalene-based high-efficiency water reducers, the steric hindrance effect makes the dispersion last much longer, and the slump retention performance of concrete using polycarboxylic acid water reducers is better. At the same time, it has good compatibility with cement, admixtures, and active additives, providing a good technical guarantee for the promotion of the use of large-volume fly ash, slag, steel slag, manganese slag and other industrial solid wastes. In addition, the breakthrough in the process technology of polycarboxylic acid water reducers - no formaldehyde is used in the synthesis, which has less environmental pollution and is conducive to the sustainable development of construction.

[0003] At the same time, due to my country's vast territory, complex ground materials and diversified concrete raw materials, some problems are inevitable in the application of polycarboxylic acid water-reducing agents. In engineering applications, different cements, mineral powders and fly ash will inevitably cause some adaptability problems when using polycarboxylic acid water-reducing agents, such as increased water demand, large fluctuations in admixture dosage, irregular strength growth, abnormal concrete setting time, large slump loss, etc. In particular, when fly ash is used as an admixture in precast concrete beams and plain concrete structures, it brings serious appearance problems, which are specifically manifested in: color difference on the concrete surface, large areas of scattered black spots, large areas of pores, etc. For precast concrete beams and plain concrete structures, the demolding surface is not decorated in any way and is used as the final delivery surface. If the above-mentioned appearance problems exist, it is difficult to meet the delivery standards. At the same time, too many pores in the concrete will also bring quality risks such as reduced strength. Color difference, spots, etc. can be well solved by fully mixing the concrete and strictly screening the raw materials. However, the problem of many pores on the concrete surface is still difficult to deal with by adding defoamer components to the polycarboxylic acid water reducer through compounding. At present, this problem has become a major technical difficulty in the application of concrete admixtures.

[0004] There are various reasons for the existence of apparent pores in concrete. Polycarboxylate water reducer itself is a surfactant with a designable structure and is extremely hydrophilic. During its synthesis process, some surface-active components that reduce surface tension are often retained. Therefore, it inherently has a certain air-entraining function. These components that reduce surface tension are different from traditional air-entraining agents. In the production process of air-entraining agents, some necessary conditions for generating stable, fine, and closed bubbles are considered, and surface-active components are added to the air-entraining agents. As a result, the bubbles introduced into the concrete can bring excellent workability and constructability to the concrete on the premise of meeting the specified requirements of the air content, and will not have an adverse impact on properties such as strength. In a concrete structure, excessive air content will bring the risk of strength reduction and also affect the appearance quality of the concrete. Water reducer application manufacturers usually add defoaming agent components according to needs to reduce the internal air content of the concrete to meet the requirements. Bubbles caused by raw materials or gradation problems in the concrete itself can usually be well eliminated by compounding defoaming agents. However, if bubbles are generated during the reaction of the concrete materials themselves after the concrete is mixed with water, and the bubbles are just in the stage when the concrete loses plasticity, and there is not enough concrete slurry to fill the bubble defects, resulting in porosity inside and on the surface of the hardened concrete, this problem is often difficult to handle; improper use of fly ash is the main reason for the generation of reaction bubbles in concrete. Fly ash is a by-product of coal-fired power plants. Its micro-aggregate effect, morphological effect, activity effect, etc. can improve the workability, long-term durability, and late mechanical properties of concrete. With increasing attention to environmental protection, large domestic coal-fired power plants have completed desulfurization and denitrification technical transformations in order to meet emission standards, and most of the fly ash produced by power plants is denitrified fly ash. At present, the most commonly used flue gas denitrification technologies in the world are selective catalytic reduction technology (SCR) and selective non-catalytic reduction technology (SNCR). Both denitrification technologies use liquid ammonia, ammonia water, or urea as reducing agents. In actual applications, ammonia escape cannot be completely avoided, and the escaped ammonia reacts with sulfur oxides in the flue gas to generate a large amount of ammonium salts, thus causing the enrichment of such substances in fly ash. When using this kind of fly ash in ready-mixed concrete, ammonium salts will continuously react in an alkaline environment to release ammonia gas, generating bubble holes inside and on the surface of the concrete, which has an adverse impact on the appearance and compressive strength of the concrete. The existing forms of residual ammonia in denitrified fly ash are mainly physically adsorbed ammonia gas, ammonium bicarbonate, ammonium sulfate, and ammonium bisulfate. After being incorporated into the concrete, the denitrified fly ash dissolves in water to become free ammonium ions, and there is the following equilibrium for ammonium ions under the alkaline condition provided by cement hydration:

[0005]

[0006] As ammonia gas escapes, the ammonia concentration in the solution decreases, promoting the ionization equilibrium to shift to the right, enabling continuous generation and release of ammonia gas. At the same time, with the continuous progress of hydration, the increase in the content of the hydration by-product calcium hydroxide leads to an increase in alkalinity in the free aqueous solution, further promoting the rightward shift of the ionization equilibrium. During concrete pouring and vibration, high-frequency vibration also accelerates the escape of ammonia gas. Considering the above factors, the escaped ammonia gas stays on the surface of the concrete formwork during the stage when the concrete loses its plasticity, resulting in the formation of defective holes after hardening. At the same time, due to the presence of gas, the internal compactness of the concrete decreases, thereby posing a risk of reduced concrete strength.

[0007] Regarding the above-mentioned concrete air hole problems, the prior art discloses improving the concrete air hole problems by adding a defoaming agent component to the polycarboxylate superplasticizer through compounding means or modifying the polycarboxylate superplasticizer. For example, the Chinese patent application with publication number CN110372255A discloses a composite high-performance polycarboxylate superplasticizer, which includes the following raw materials in parts by weight: 15 - 20 parts of a water-reducing polycarboxylate superplasticizer mother liquor, 10 - 15 parts of a viscosity-reducing polycarboxylate superplasticizer mother liquor, 20 - 30 parts of a sustained-release polycarboxylate superplasticizer mother liquor, 10 - 15 parts of a hydration heat inhibitor, 2 - 5 parts of a retarder, 0 - 0.1 part of a consistency regulator, 0 - 0.06 part of an air-entraining agent, and 0 - 0.05 part of a defoaming agent. This patent application obtains a composite high-performance polycarboxylate superplasticizer by adding a defoaming agent through conventional compounding means, which can handle the inherent bubbles caused by poor grading of conventional concrete manufactured sand, surface activity, stirring, etc., but cannot solve the quality problems caused by the bubbles generated by the reaction of coal ash materials in concrete. The Chinese patent application with publication number CN113461872A discloses a bubble-control monomer, a polycarboxylate superplasticizer, and its preparation method. By grafting the bubble-control monomer to modify the polycarboxylate molecular structure, it can effectively control the size and distribution of bubbles in the concrete structure and reduce the number of surface bubbles. However, this patented technology cannot fundamentally solve the adverse effects of fly ash on the appearance and compressive strength of concrete, and in this patent, complex chemical means are required to synthesize and prepare the bubble-control monomer from unsaturated acids and amphoteric monomers, which requires high temperature and catalytic conditions, and the conditions are relatively cumbersome and harsh. Summary of the Invention

[0008] Aiming at the above deficiencies, the present invention provides a composite superplasticizer for inhibiting the reaction bubbles of fly ash in concrete and its preparation method, which can inhibit the generation of bubbles caused by the reaction of denitrification fly ash under alkaline conditions, and improve the appearance quality and strength of precast concrete beams and fair-faced concrete. The specific technical solutions are as follows:

[0009] A composite water reducer for suppressing reaction bubbles of fly ash in concrete, characterized in that, by weight, 1000 parts of the composite water reducer are composed of the following raw materials: 100-350 parts of polycarboxylate water reducing mother liquor, 50-250 parts of polycarboxylate slump retaining mother liquor, 0-55 parts of retarder, 0-0.2 parts of air-entraining agent, 0-0.3 parts of defoaming agent, 10-40 parts of inhibitor, 0-10 parts of water retention and thickening agent, and the rest is water; the inhibitor is one or more of ferrous sulfate, copper sulfate, magnesium sulfate, and zinc sulfate.

[0010] The technical principle of the composite water reducer for suppressing reaction bubbles of fly ash in concrete of the present invention is as follows: using the reaction between the inhibitor and ammonia molecules hydrolyzed from ammonium ions in the concrete slurry to produce alkaline precipitates, effectively reducing the hydroxide ion concentration in the concrete slurry, making the ionization equilibrium shift and slowing down the formation of bubble holes caused by the release of ammonia due to concentration aggregation; at the same time, the inhibitor can react with the main component ammonium sulfate in desulfurized fly ash to form relatively stable and low-solubility Mohr's salt (ammonium ferrous sulfate), also effectively reducing the ammonium ions in the concrete slurry, promoting the ionization equilibrium to shift to the left, and avoiding the release of ammonia due to the concentration aggregation of ammonia molecules; avoiding surface holes caused by the inability of air holes to heal during the stage when the concrete loses plasticity and improving the concrete strength; in addition, the inhibitor also has the functions of solidifying harmful substances in the concrete such as heavy metal chromium, reducing the risk of virus harm brought by human absorption, and enhancing the concrete strength. The main reaction formulas are as follows:

[0011] CuSO4 + 2NH3·H2O = Cu(OH)2↓ + (NH4)2SO4

[0012] FeSO4 + 2NH3·H2O = Fe(OH)2↓ + (NH4)2SO4

[0013] MgSO4 + 2NH3·H2O = Mg(OH)2↓ + (NH4)2SO4

[0014] (NH4)2SO4 + FeSO4 + 6H2O = (NH4)2SO4·FeSO4·6H2O (Mohr's salt).

[0015] In the present invention, the inhibitor is a water-soluble component. At the same time, the main component mother liquor of the polycarboxylate water reducer itself is a macromolecule synthesized by organic synthesis. After the polymerization reaction, each active monomer has been grafted and polymerized, and will not react with the inhibitor to cause the inactivation of the inhibitor. Moreover, the polycarboxylate water reducer is acidic, which can effectively avoid the hydrolysis of the inhibitor to form precipitate flocs, creating good conditions for the stability of the inhibitor; other components are also water-soluble components, and the components will not affect each other to cause problems such as reduced solubility and precipitation, nor will there be any adverse reactions that cause the functions of each component to fail.

[0016] The composite water reducer for inhibiting the reaction bubbles of fly ash in concrete combines components such as an inhibitor, a polycarboxylate water reducing mother liquor, a polycarboxylate slump retaining mother liquor, etc. Among them, the polycarboxylate water reducing mother liquor provides sufficient electrostatic repulsion and dispersibility for the concrete due to its special comb-shaped molecular structure and active groups such as carboxyl groups, sulfonic acid groups, and hydroxyl groups; the polycarboxylate slump retaining mother liquor gradually releases active groups with anchoring and dispersing effects under the condition of increasing alkalinity during the cement hydration process, continuously maintaining the dispersibility of the concrete to meet the construction requirements; the corresponding retarder delays the hydration of the cement, effectively avoiding the cracking of the concrete caused by the concentration of hydration heat due to too short setting time; the water retaining and thickening agent, air-entraining agent, and defoaming agent play an auxiliary role in improving the workability and quality of the concrete; the cooperation of each component in the concrete can effectively improve the quality of the concrete.

[0017] Preferably, in the above-mentioned composite water reducer for inhibiting the reaction bubbles of fly ash in concrete, the solid content of the polycarboxylate water reducing mother liquor is 40% - 50%.

[0018] Preferably, in the above-mentioned composite water reducer for inhibiting the reaction bubbles of fly ash in concrete, the solid content of the polycarboxylate slump retaining mother liquor is 40% - 50%.

[0019] Preferably, in the above-mentioned composite water reducer for inhibiting the reaction bubbles of fly ash in concrete, the retarder is one or more of white sugar, sodium gluconate, boric acid, tartaric acid, sodium tripolyphosphate, sodium polyphosphate, sodium hexametaphosphate, phosphoric acid, trisodium phosphate, sodium phosphate tetrabasic, disodium hydrogen phosphate, sodium pyrophosphate, alkyl phosphate ester, disodium ethylenediaminetetraacetate.

[0020] Preferably, in the above-mentioned composite water reducer for inhibiting the reaction bubbles of fly ash in concrete, the water retaining and thickening agent is one or more of maltodextrin, polyacrylamide, welan gum, xanthan gum, and cellulose ether.

[0021] Preferably, in the above-mentioned composite water reducer for inhibiting the reaction bubbles of fly ash in concrete, the air-entraining agent is one or more of rosin resin type, alkyl benzene sulfonate type, fatty alcohol sulfonate type, carboxylic acid type, alkyl sulfate type, and saponin type; the defoaming agent is one or more of organosilane type, polyether type, organic alcohol type, mineral type, and polysiloxane type.

[0022] Preferably, in the above-mentioned composite water reducer for inhibiting the reaction bubbles of fly ash in concrete, the inhibitor is ferrous sulfate.

[0023] Preferably, in the above-mentioned composite water reducer for inhibiting the reaction bubbles of fly ash in concrete, by weight, it is composed of the following raw materials: 225 parts of polycarboxylate water reducing mother liquor, 150 parts of polycarboxylate slump retaining mother liquor, 35 parts of retarder, 0.1 part of air-entraining agent, 0.1 part of defoaming agent, 30 parts of inhibitor, 0.4 part of water retaining and thickening agent, and 559.4 parts of water; the inhibitor is ferrous sulfate.

[0024] A preparation method of the composite water reducer for suppressing the reaction bubbles of fly ash in concrete as described above, comprising the following steps:

[0025] (1) First, water and retarder are put into a stirring kettle, stirred to dissolve the retarder in the water, and then an inhibitor is added and stirred to dissolve.

[0026] (2) The polycarboxylate water reducer mother liquor and the polycarboxylate slump retention mother liquor are put into the stirring kettle and stirred evenly.

[0027] (3) The water retention thickener is put into the stirring kettle, and the stirring is started to ensure that all the added components are fully mixed evenly.

[0028] (4) The defoaming agent is added. After the defoaming agent is completely stirred evenly and all the large air bubbles on the surface of the water reducer are completely eliminated, the air-entraining agent is added and stirred evenly.

[0029] Application of the composite water reducer for suppressing the reaction bubbles of fly ash in concrete as described above in the preparation of concrete containing fly ash.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. In the composite water reducer for suppressing the reaction bubbles of fly ash in concrete of the present invention, adding an inhibitor can effectively inhibit the bubble reaction of denitrification fly ash, avoid the surface holes caused by the inability of pores to heal during the plastic loss stage of concrete, and fundamentally solve the problems such as the surface quality problems and strength decline of precast concrete beams and fair-faced concrete caused by the reaction bubbles brought by using denitrification fly ash. The solution method is simple and efficient; the inhibitor can stably exist with other components, and the components will not affect each other to cause problems such as reduced solubility and precipitation, nor will there be any adverse reactions that cause the failure of the functions of each component; when the components are used in combination in concrete, the quality of concrete can be effectively improved.

[0032] 2. The composite water reducer for suppressing the reaction bubbles of fly ash in concrete of the present invention can effectively reduce the compounding amount of the defoaming agent used in the water reducer, can alleviate the problems such as surface oil floating and stratification precipitation caused by the water reducer compounded with a large amount of organosilicon or silicone ether composite defoaming agent, and at the same time avoids the problems such as bleeding, workability and wrapping property of concrete caused by the large amount of defoaming agent used in concrete; at the same time, the inhibitor is easily soluble and has stable properties, and compounding with the polycarboxylate water reducer does not affect the use effect and there is no problem of stratification.

[0033] 3. The preparation method of the composite water reducer for suppressing the reaction bubbles of fly ash in concrete of the present invention is obtained by physically mixing each component, and there is no need to perform modification treatment on the polycarboxylate water reducer mother liquor required for compounding in advance. The method is simple and easy to operate.

[0034] 4. The present invention solves the technical problem of using denitrified fly ash in concrete, provides technical guarantee for the use of complex local materials in concrete, can reduce the ammonia gas released by denitrified fly ash in concrete, and reduces the safety risk brought to construction workers by the ammonia gas released from concrete. Detailed Embodiments

[0035] The following is a detailed description of the specific embodiments of the present invention, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0036] Example 1

[0037] A composite water reducer for suppressing the reaction bubbles of fly ash in concrete is composed of the following raw materials by weight: 225 parts of polycarboxylate water reducing mother liquor (solid content 50%), 150 parts of polycarboxylate slump retaining mother liquor (solid content 50%), 25 parts of sodium gluconate, 10 parts of white sugar, 0.1 part of fatty alcohol sulfonate air-entraining agent, 0.1 part of polyether block polyether defoaming agent, 10 parts of ferrous sulfate inhibitor, 0.4 part of 400-viscosity hydroxypropyl methyl cellulose ether (HPMC) water retention and thickening agent, and 579.4 parts of water. Among them, the polycarboxylate water reducing mother liquor is produced by Guangxi Yunying New Materials Technology Co., Ltd., with the model H108-501; the polycarboxylate slump retaining mother liquor is produced by Guangxi Yunying New Materials Technology Co., Ltd., with the model H107E-501, and the fatty alcohol sulfonate air-entraining agent is produced by Evonik (China) Investment Co., Ltd., with the model SITREN AIRVOID 616; the polyether block polyether defoaming agent is produced by Toho Chemical (Shanghai) Co., Ltd., with the model AIRSIZER DF-210.

[0038] The preparation method of the composite water reducer for suppressing the reaction bubbles of fly ash in concrete in this example includes the following steps:

[0039] Put 579.4 parts of water in the formula into the stirring kettle, add 25 parts of sodium gluconate + 10 parts of white sugar as the retarder, and stir and dissolve them in water. After the stirring and dissolving are completed, add 10 parts of ferrous sulfate as the inhibitor, and start stirring to ensure complete dissolution; put 225 parts of polycarboxylate water reducing mother liquor and 150 parts of polycarboxylate slump retaining mother liquor into the stirring kettle and stir evenly; put 0.4 part of 400-viscosity cellulose ether as the water retention and thickening agent into the stirring kettle, start stirring to ensure that all the added components are fully mixed evenly, then add 0.1 part of defoaming agent. After the defoaming agent is completely stirred evenly and all the large bubbles on the surface of the water reducer are completely eliminated, add 0.1 part of air-entraining agent and stir evenly.

[0040] Example 2

[0041] A composite water reducer for inhibiting reaction bubbles of fly ash in concrete, by weight, is composed of the following raw materials: 225 parts of polycarboxylate water reducing mother liquor (solid content 50%), 150 parts of polycarboxylate slump retaining mother liquor (solid content 50%), 25 parts of sodium gluconate, 10 parts of white sugar, 0.1 part of fatty alcohol sulfonate air-entraining agent, 0.1 part of polyether block polyether defoaming agent, 20 parts of ferrous sulfate inhibitor, 0.4 part of 400-viscosity hydroxypropyl methyl cellulose ether water retention and thickening agent (HPMC), and 569.4 parts of water. Among them, the polycarboxylate water reducing mother liquor is produced by Guangxi Yunying New Material Technology Co., Ltd., with the model H108-501; the polycarboxylate slump retaining mother liquor is produced by Guangxi Yunying New Material Technology Co., Ltd., with the model H107E-501, the fatty alcohol sulfonate air-entraining agent is produced by Evonik (China) Investment Co., Ltd., with the model SITREN AIRVOID 616; the polyether block polyether defoaming agent is produced by Toho Chemical (Shanghai) Co., Ltd., with the model AIRSIZER DF-210.

[0042] The preparation method of the composite water reducer for inhibiting reaction bubbles of fly ash in concrete in this example is the same as that in Example 1, the difference being: the dosage of the inhibitor ferrous sulfate is different.

[0043] Example 3

[0044] A composite water reducer for inhibiting reaction bubbles of fly ash in concrete, by weight, is composed of the following raw materials: 225 parts of polycarboxylate water reducing mother liquor (solid content 50%), 150 parts of polycarboxylate slump retaining mother liquor (solid content 50%), 25 parts of sodium gluconate, 10 parts of white sugar, 0.1 part of fatty alcohol sulfonate air-entraining agent, 0.1 part of polyether block polyether defoaming agent, 30 parts of ferrous sulfate inhibitor, 0.4 part of 400-viscosity hydroxypropyl methyl cellulose ether (HPMC) water retention and thickening agent, and 559.4 parts of water. Among them, the polycarboxylate water reducing mother liquor is produced by Guangxi Yunying New Material Technology Co., Ltd., with the model H108-501; the polycarboxylate slump retaining mother liquor is produced by Guangxi Yunying New Material Technology Co., Ltd., with the model H107E-501, the fatty alcohol sulfonate air-entraining agent is produced by Evonik (China) Investment Co., Ltd., with the model SITREN AIRVOID 616; the polyether block polyether defoaming agent is produced by Toho Chemical (Shanghai) Co., Ltd., with the model AIRSIZER DF-210.

[0045] The preparation method of the composite water reducer for inhibiting reaction bubbles of fly ash in concrete in this example is the same as that in Example 1, the difference being: the dosage of the inhibitor ferrous sulfate is different.

[0046] Example 4

[0047] A composite water reducer for suppressing reaction bubbles of fly ash in concrete, by weight, is composed of the following raw materials: 225 parts of polycarboxylate water-reducing mother liquor (solid content 50%), 150 parts of polycarboxylate slump-retention mother liquor (solid content 50%), 25 parts of sodium gluconate, 10 parts of white sugar, 0.1 part of fatty alcohol sulfonate air-entraining agent, 0.1 part of polyether block polyether defoaming agent, 40 parts of ferrous sulfate inhibitor, 0.4 part of 400-viscosity hydroxypropyl methyl cellulose ether (HPMC) water-retaining and thickening agent, and 549.4 parts of water. Among them, the polycarboxylate water-reducing mother liquor is produced by Guangxi Yunying New Material Technology Co., Ltd., with the model H108-501; the polycarboxylate slump-retention mother liquor is produced by Guangxi Yunying New Material Technology Co., Ltd., with the model H107E-501; the fatty alcohol sulfonate air-entraining agent is produced by Evonik (China) Investment Co., Ltd., with the model SITREN AIRVOID 616; the polyether block polyether defoaming agent is produced by Toho Chemical (Shanghai) Co., Ltd., with the model AIRSIZER DF-210.

[0048] The preparation method of the composite water reducer for suppressing reaction bubbles of fly ash in concrete in this example is the same as that in Example 1, except that the dosage of the inhibitor ferrous sulfate is different.

[0049] Example 5

[0050] A composite water reducer for suppressing reaction bubbles of fly ash in concrete, by weight, is composed of the following raw materials: 250 parts of polycarboxylate water-reducing mother liquor (solid content 45%), 167 parts of polycarboxylate slump-retention mother liquor (solid content 45%), 20 parts of white sugar, 0.1 part of alkyl sulfate sodium dodecyl sulfate air-entraining agent, 0.1 part of organosilane polysiloxane defoaming agent, 30 parts of magnesium sulfate inhibitor, 10 parts of maltodextrin, and 522.8 parts of water. Among them, the polycarboxylate water-reducing mother liquor is produced by Hunan Zhongyan Building Materials Technology Co., Ltd., with the model WR-900; the polycarboxylate slump-retention mother liquor is produced by Hunan Zhongyan Building Materials Technology Co., Ltd., with the model OM-802; the alkyl sulfate sodium dodecyl sulfate air-entraining agent is produced by Shanghai Maxam Daily Chemical Co., Ltd., with the model K12; the organosilane polysiloxane defoaming agent is produced by Toho Chemical (Shanghai) Co., Ltd., with the model AIRSIZER FZ-150.

[0051] The preparation method of the composite water reducer for suppressing reaction bubbles of fly ash in concrete in this example is the same as that in Example 1, except that there are differences in the variety of formula raw materials, the solid content of the mother liquor, and the manufacturer.

[0052] Example 6

[0053] A composite water reducer for suppressing the reaction bubbles of fly ash in concrete, by weight, consists of the following raw materials: 225 parts of polycarboxylate water reducing mother liquor (solid content 50%), 150 parts of polycarboxylate slump retaining mother liquor (solid content 50%), 20 parts of boric acid, 10 parts of sodium tripolyphosphate, 0.1 part of saponin triterpenoid saponin air-entraining agent, 0.1 part of polysiloxane defoaming agent, 30 parts of copper sulfate inhibitor, 0.2 part of 20,000 viscosity methyl cellulose ether (MC) water retention and thickening agent, and 564.6 parts of water. Among them, the polycarboxylate water reducing mother liquor is produced by Guangdong Langtaosha New Materials Co., Ltd., with the model PC-50JS; the polycarboxylate slump retaining mother liquor is produced by Guangdong Langtaosha New Materials Co., Ltd., with the model PC-50BT; the saponin triterpenoid saponin air-entraining agent is produced by Jiangxi Xinzhongye Tea Industry Technology Co., Ltd., with the model ZY-99; the polysiloxane defoaming agent is produced by Dongguan Shengyuan Synthetic Materials Technology Co., Ltd., with the model S825.

[0054] The preparation method of the composite water reducer for suppressing the reaction bubbles of fly ash in concrete in this example is the same as that in Example 1, except for the differences in the variety of formula raw materials, the solid content of the mother liquor, and the manufacturer.

[0055] Example 7

[0056] A composite water reducer for suppressing the reaction bubbles of fly ash in concrete, by weight, consists of the following raw materials: 281 parts of polycarboxylate water reducing mother liquor (solid content 40%), 188 parts of polycarboxylate slump retaining mother liquor (solid content 40%), 20 parts of tartaric acid, 10 parts of sodium gluconate, 0.1 part of carboxylic acid air-entraining agent, 0.1 part of organosilane polysiloxane defoaming agent, 30 parts of zinc sulfate inhibitor, 0.4 part of anionic 6 million molecular weight polyacrylamide water retention and thickening agent, and 470.4 parts of water. Among them, the polycarboxylate water reducing mother liquor is produced by Yunnan Aochu Technology Co., Ltd., with the model OCJS-22; the polycarboxylate slump retaining mother liquor is produced by Yunnan Aochu Technology Co., Ltd., with the model OCBT-11; the carboxylic acid air-entraining agent is produced by Toho Chemical (Shanghai) Co., Ltd., with the model ALSCOAPAE-720; the organosilane polysiloxane defoaming agent is produced by Nanning Tengda Auxiliary Co., Ltd., with the model TD-322.

[0057] The preparation method of the composite water reducer for suppressing the reaction bubbles of fly ash in concrete in this example is the same as that in Example 1, except for the differences in the variety of formula raw materials, the solid content of the mother liquor, and the manufacturer.

[0058] Comparative Example 1

[0059] A composite water reducer is composed of the following raw materials by weight: 225 parts of polycarboxylate water-reducing mother liquor (solid content 50%), 150 parts of polycarboxylate slump-retention mother liquor (solid content 50%), 25 parts of sodium gluconate, 10 parts of white sugar, 0.1 part of fatty alcohol sulfonate air-entraining agent, 0.1 part of polyether block polyether defoaming agent, 0.4 part of 400-viscosity hydroxypropyl methyl cellulose ether (HPMC) water-retaining thickening agent, and 589.4 parts of water. Among them, the polycarboxylate water-reducing mother liquor is produced by Guangxi Yunying New Material Technology Co., Ltd. with the model H108-501; the polycarboxylate slump-retention mother liquor is produced by Guangxi Yunying New Material Technology Co., Ltd. with the model H107E-501, and the fatty alcohol sulfonate air-entraining agent is produced by Evonik (China) Investment Co., Ltd. with the model SITREN AIRVOID 616; the polyether block polyether defoaming agent is produced by Toho Chemical (Shanghai) Co., Ltd. with the model AIRSIZER DF-210.

[0060] The preparation method of the composite water reducer in this comparative example is the same as that in Example 1, except that no inhibitor is used.

[0061] Comparative Example 2

[0062] A composite water reducer is composed of the following raw materials by weight: 250 parts of polycarboxylate water-reducing mother liquor (solid content 45%), 167 parts of polycarboxylate slump-retention mother liquor (solid content 45%), 20 parts of white sugar, 0.1 part of alkyl sulfate sodium dodecyl sulfate air-entraining agent, 0.1 part of organosilane polysiloxane defoaming agent, 10 parts of maltodextrin, and 552.8 parts of water. Among them, the polycarboxylate water-reducing mother liquor is produced by Hunan Zhongyan Building Materials Technology Co., Ltd. with the model WR-900; the polycarboxylate slump-retention mother liquor is produced by Hunan Zhongyan Building Materials Technology Co., Ltd. with the model OM-802; the alkyl sulfate sodium dodecyl sulfate air-entraining agent is produced by Shanghai Maxam Daily Chemical Co., Ltd. with the model K12; the organosilane polysiloxane defoaming agent is produced by Toho Chemical (Shanghai) Co., Ltd. with the model AIRSIZER FZ-150.

[0063] The preparation method of the composite water reducer in this comparative example is the same as that in Example 5, except that no inhibitor is used.

[0064] Comparative Example 3

[0065] A composite water reducer is composed of the following raw materials by weight: 225 parts of polycarboxylate water-reducing mother liquor (solid content 50%), 150 parts of polycarboxylate slump-retention mother liquor (solid content 50%), 20 parts of boric acid, 10 parts of sodium tripolyphosphate, 0.1 part of saponin triterpenoid saponin air-entraining agent, 0.1 part of polysiloxane defoaming agent, 0.2 part of 20,000-viscosity methyl cellulose ether water-retaining thickener, and 594.6 parts of water. Among them, the polycarboxylate water-reducing mother liquor is produced by Guangdong Langtaosha New Materials Co., Ltd., with the model PC-50JS; the polycarboxylate slump-retention mother liquor is produced by Guangdong Langtaosha New Materials Co., Ltd., with the model PC-50BT; the saponin triterpenoid saponin air-entraining agent is produced by Jiangxi Xinzhongye Tea Technology Co., Ltd., with the model ZY-99; the polysiloxane defoaming agent is produced by Dongguan Shengyuan Synthetic Materials Technology Co., Ltd., with the model S825.

[0066] The preparation method of the composite water reducer in this comparative example is the same as that in Example 6, except that the inhibitor is not used.

[0067] Comparative Example 4

[0068] A composite water reducer is composed of the following raw materials by weight: 281 parts of polycarboxylate water-reducing mother liquor (solid content 40%), 188 parts of polycarboxylate slump-retention mother liquor (solid content 40%), 20 parts of tartaric acid, 10 parts of sodium gluconate, 0.1 part of carboxylic acid air-entraining agent, 0.1 part of organosilane polysiloxane defoaming agent, 0.4 part of anionic 6-million-molecular-weight polyacrylamide water-retaining thickener, and 500.4 parts of water. Among them, the polycarboxylate water-reducing mother liquor is produced by Yunnan Aochu Technology Co., Ltd., with the model OCJS-22; the polycarboxylate slump-retention mother liquor is produced by Yunnan Aochu Technology Co., Ltd., with the model OCBT-11; the carboxylic acid air-entraining agent is produced by Toho Chemical (Shanghai) Co., Ltd., with the model ALSCOAPAE-720; the organosilane polysiloxane defoaming agent is produced by Nanning Tengda Auxiliary Co., Ltd., with the model TD-322.

[0069] The preparation method of the composite water reducer in this comparative example is the same as that in Example 7, except that the inhibitor is not used.

[0070] Test Example

[0071] The following concrete application performance, air content and mechanical property tests are carried out on the composite water reducers prepared in Examples 1 to 7 and Comparative Examples 1 to 4:

[0072] ① Materials for performance testing: Cement, Yufeng P.O42.5 ordinary Portland cement; Manufactured sand, produced in Liuzhou, Guangxi, fineness modulus 2.5, methylene blue MB value 0.8; Fly ash A, secondary ash produced in Baise, Guangxi, with relatively high ammonia content, obvious pungent smell, activity index 78%, ammonium ion content 752 mg / kg; Fly ash B, secondary fly ash produced in Pingguo, Guangxi, without obvious pungent smell, activity index 77%, ammonium ion content 12 mg / kg; Mineral powder, S95 grade produced in Beihai, Guangxi, activity index 96%; Aggregates, crushed stones with particle size of 5 - 30 mm; Water, tap water; The admixtures are those in Examples 1 - 7 and Comparative Examples 1 - 4 above.

[0073] ② The tests for measuring the application performance and air content of concrete were carried out with reference to GB / T50080 - 2016 "Standard Test Method for Performance of Ordinary Concrete Mixtures". The only variable in the experimental mix proportion of concrete was fly ash. Two sets of mix proportions were set as shown in Table 1. The concrete was mixed according to the proportions in Table 1, and the slump and spread of the fresh concrete mixture were recorded at the initial stage, 1 h, and 2 h respectively, with the unit of mm; The air content (%) of the fresh concrete mixture was measured at the initial stage, 1 h, and 2 h respectively.

[0074] Table 1 Experimental mix proportion of concrete

[0075]

[0076] The comparison of the working performance, mechanical properties, and air content of concrete can be seen in Table 2 and Table 3 respectively. In Table 2 and Table 3, the dosage of the composite water - reducing agent is 2.0%, while keeping the water consumption consistent and the water - cement ratio unchanged.

[0077] It can be clearly seen from the air content data in Table 3 that the overall air content of Concrete Mix Ratio 1 (Fly ash A, ammonium ion content 752 mg / kg) is higher than that of Concrete Mix Ratio 2 (Fly ash B, ammonium ion content 12 mg / kg); from the test results of the concrete in Table 2, it can be known that under the same conditions, in terms of mechanical properties, the 3d / 7d early strength and 28d strength of Concrete Mix Ratio 2 (Fly ash B, ammonium ion content 12 mg / kg) are both higher than those of Concrete Mix Ratio 1 (Fly ash A, ammonium ion content 752 mg / kg) as a whole, indicating that the excessive presence of ammonium ions under alkaline conditions will generate gas, increase the internal voids of the concrete, resulting in an increase in air content and at the same time bringing the risk of strength reduction; from the concrete tests in Table 2, comparing Examples 1-7 and Comparative Examples 1-4, the slump / spread data are basically the same, indicating that this technical solution does not affect the normal efficacy of the polycarboxylate water reducer and will not affect the normal application state of the concrete. Comparing Examples 1-4, it can be seen that within a certain range of the inhibitor dosage, the 3d / 7d early strength increases regularly with the gradual increase of the inhibitor dosage. The inhibitor addition measure proposed in this technical solution can improve the early strength and late strength of the concrete, which should be due to the use of ion doping to accelerate the cement hardening process, improve the cement hydration environment and conditions, and make the performance of the cement more stable and excellent; from the concrete air content in Table 3, comparing Examples 1-7 and Comparative Examples 1-4, the overall air content of the examples is significantly lower than that of the comparative examples, and at the same time the surface pore condition is significantly improved, indicating that the inhibitor in this technical solution effectively restricts the gas release due to the excessive ammonium ions in the fly ash under alkaline conditions; as the cement hydration proceeds, the inside of the concrete should tend to be dense and the air content will decrease. Comparing Comparative Examples 1-4, the air content remains basically the same from the initial stage to 1 h and even slightly increases, indicating that the gas generated by the reaction in Comparative Examples 1-4 contributes to the part of the air content lost due to hydration, while the air content of Examples 1-7 gradually decreases from the initial stage to 1 h and 2 h, indicating that adding the inhibitor can improve the problem of reaction bubbles in denitrified fly ash and increase the strength.

[0078] Table 2 Concrete Workability and Mechanical Properties

[0079]

[0080]

[0081] Table 3 Concrete Air Content

[0082]

[0083]

[0084] In summary, the composite water reducer for suppressing the reaction bubbles of fly ash in concrete can effectively solve the problems of the appearance quality and strength risk hidden dangers caused by the bubbles generated by the reaction of denitrification fly ash under alkaline conditions in precast concrete beams and fair-faced concrete pores, and improve the quality of concrete.

[0085] The foregoing description of the specific exemplary embodiments of the present invention is for purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and obviously, many changes and variations are possible in light of the above teaching. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical applications, so that those skilled in the art can implement and utilize the various different exemplary embodiments of the present invention, as well as various different selections and changes. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims

1. A composite water reducing agent for inhibiting concrete fly ash reaction bubbles, characterized in that: The invention is composed of the following raw materials by weight: 225 parts of polycarboxylic acid water-reducing mother liquor, 150 parts of polycarboxylic acid slump-retaining mother liquor, 35 parts of retarder, 0.1 parts of air entraining agent, 0.1 parts of defoamer, 30 parts of inhibitor, 0.4 parts of water-retaining thickener, and 559.4 parts of water; the inhibitor is ferrous sulfate; the air entraining agent is fatty alcohol sulfonate; and the defoamer is polyether.

2. The composite water reducing agent for inhibiting concrete fly ash reaction bubbles according to claim 1, characterized in that: The solid content of the polycarboxylic acid water-reducing mother liquor is 40% to 50%.

3. The composite water reducing agent for inhibiting concrete fly ash reaction bubbles according to claim 1, characterized in that: The solid content of the polycarboxylic acid collapse-retaining mother solution is 40% to 50%.

4. The composite water reducing agent for inhibiting concrete fly ash reaction bubbles according to claim 1, characterized in that: The retarder is one or more of white sugar, sodium gluconate, boric acid, tartaric acid, sodium tripolyphosphate, sodium polyphosphate, sodium hexametaphosphate, phosphoric acid, trisodium phosphate, tetrasodium phosphate, disodium hydrogen phosphate, sodium pyrophosphate, alkyl phosphate, and disodium ethylenediaminetetraacetate.

5. The composite water reducing agent for inhibiting concrete fly ash reaction bubbles according to claim 1, characterized in that: The water-retaining thickener is one or more of maltodextrin, polyacrylamide, weinland gum, xanthan gum and cellulose ether.

6. A method for preparing a composite water reducing agent for inhibiting reaction bubbles of concrete fly ash as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Put water and retarder into a stirring kettle in sequence, stir to dissolve the retarder in water, then add the inhibitor and stir to dissolve; (2) putting the polycarboxylic acid water-reducing mother liquor and the polycarboxylic acid collapse-preserving mother liquor into a stirring kettle and stirring them evenly; (3) Add the water-retaining thickener into the stirring kettle and start stirring to ensure that all the components are fully mixed; (4) Add the defoaming agent and stir it evenly. After the large bubbles on the surface of the water reducer are completely eliminated, add the air entraining agent and stir it evenly.

7. Use of the composite water reducing agent for inhibiting reaction bubbles of concrete fly ash as claimed in any one of claims 1 to 5 in the preparation of concrete containing fly ash.

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