CN114316157B - Environment-friendly water reducer - Google Patents
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Abstract
The invention discloses a green environment-friendly water reducer, which improves the dispersion performance of the water reducer by introducing different ionic groups into polycarboxylate to change charges, and is not limited to realizing the dispersion of concrete particles by steric hindrance. The invention introduces the phosphorus-containing group into the side chain, and the phosphorus-containing group can provide larger steric hindrance compared with a carbon straight-chain structure, so that the density of the side chain on the main chain of the polycarboxylate can be reduced to enhance the water-reducing capability; and after the phosphate group is added, the phosphate group and calcium ions have stronger complexing ability, so that the chemical adsorption ability of the invention is further improved. Under the dual effects of physical and chemical adsorption, the invention has better water reducing effect, can reduce the use of raw materials in the concrete production, and is energy-saving and economical.
Description
Technical Field
The invention relates to the technical field of concrete additives, in particular to a green environment-friendly water reducer.
Background
The water reducer is a concrete processing aid, is mostly an anionic surfactant, and can be adsorbed on the surface of concrete particles to increase the dispersibility of concrete, thereby reducing the unit water consumption. The water reducer resists compression, improves the hydration process and the working performance of concrete, can reduce the dosage of unit cement and delay setting time, and is widely applied to concrete preparation. According to the composition classification, the common water reducer comprises lignin sulfonate water reducer, naphthalene high-efficiency water reducer, melamine high-efficiency water reducer, sulfamate high-efficiency water reducer, fatty acid high-efficiency water reducer and polycarboxylate high-efficiency water reducer, wherein the water reducing efficiency of the polycarboxylate high-efficiency water reducer is up to more than 25%, and the water reducer has excellent tax reducing effect.
Patent CN 107986673A discloses a high-efficiency environment-friendly water reducer and a preparation method thereof, wherein butyl sulfonic acid cellulose ether is used for forming an adsorption layer on the surface of cement, so that the defects of poor durability, poor impermeability and limited water reducing effect of the existing water reducer are effectively overcome. Patent CN 109133697A discloses a compound polycarboxylate water reducer and a preparation method of the polycarboxylate water reducer in the compound polycarboxylate water reducer, and workability of concrete is improved by compounding various polycarboxylate water reducers and synergistic effect. The problems of single water reducing mechanism and low water reducing rate exist in the above patents, the application range is narrow, and the water reducing requirements of different types of cement in actual use are difficult to meet.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, the technical problems to be solved by the present invention are: (1) The polycarboxylate high-efficiency water reducer with excellent water reducing performance can reduce the addition amount of water in concrete, and save the consumption of raw materials on the premise of meeting the use requirement; (2) The adsorption capacity of polycarboxylate high-efficiency water reducer molecules to concrete particles is improved, and the dispersibility, the easiness and the neutrality of the water reducer to the concrete particles are improved.
The polycarboxylate superplasticizer is widely applied to concrete materials, and can increase the dispersibility of concrete particles. The traditional lignin-based and naphthalene-based water reducer can form a charged layer on the surface of particles, and achieve a dispersing effect through the repulsive interaction of the charged layer, so that the use amount of water is reduced. In contrast to the two classes of water reducers described above, polycarboxylate superplasticizers are typically polymers consisting of a main chain and side chains; the side chains of polycarboxylate superplasticizers are long, can extend into the liquid phase, and provide steric hindrance to prevent agglomeration of the particles. The side chains usually contain both hydrophobic and hydrophilic groups, and the hydrophilic groups extend to the liquid phase to form an adsorption layer, while the hydrophobic groups can adsorb on the surface of the cement particles, thereby promoting diffusion.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the environment-friendly water reducer consists of a modified polycarboxylate high-efficiency water reducer and a defoaming agent; the modified polycarboxylate superplasticizer is any one of high-dispersion carboxylate polymer and cross-linked carboxylate polymer.
Preferably, the defoaming agent is any one or a mixture of more than one of polyether defoaming agent, high-carbon alcohol defoaming agent and fatty acid defoaming agent.
Preferably, the addition amount of the defoaming agent is 0.01-0.2 wt% of the modified polycarboxylate superplasticizer.
The inventor finds that the common polycarboxylate superplasticizer has the characteristic of easy adjustment of molecular structure to meet different use demands, but also has certain limitations. The polycarboxylate superplasticizer provides steric hindrance through longer side chains to strengthen the initial dispersibility of the concrete, can accelerate the hydration of the concrete and change the crystallization state of hydration products, and simultaneously has the defect of weaker initial water reducing capacity. The inventors have thus made improvements in that the introduction of different ionic groups in the polycarboxylate to change the charge improves the dispersion properties of the water reducer, and are not limited to the dispersion of concrete particles by steric hindrance alone. The inventors have introduced phosphorus-containing groups in the side chains that can provide greater steric hindrance than the straight-chain carbon structure, and thus can reduce the density of the side chains on the main chain of the polycarboxylate to enhance the water-reducing ability. The inventor unexpectedly discovers that the water reducing capacity of the polycarboxylate high-efficiency water reducer is improved after the phosphorus-containing group is introduced, and the adsorption and combination performance of water reducer molecules and concrete particles are stronger; the reason for this phenomenon may be that the conventional polycarboxylate superplasticizer is attached to the surface of the concrete particles by physical adsorption accompanied by complexation of a small amount of carboxyl groups and calcium ions in the concrete, the complexation capability of the carboxyl groups and the calcium ions is limited, the phosphate groups are included in the phosphorus-containing groups, and after the phosphate groups are added, the phosphate groups and the calcium ions have stronger complexation capability, so that the chemisorption capability is further increased, and under the dual effects of physical and chemical adsorption, the polycarboxylate superplasticizer prepared by the inventor has better dispersibility than before, and macroscopically shows better water reducing effect.
Preferably, the preparation method of the high-dispersion carboxylate polymer comprises the following steps of:
dissolving 9-12 parts of polyethylene glycol monoallyl ether in 60-90 parts of water to obtain an aqueous solution of polyethylene glycol monoallyl ether for later use; dissolving 4-6 parts of sodium methacrylate sulfonate and 50-60 parts of acrylic acid in 40-80 parts of water to obtain a mixed solution I for later use; dissolving 3.5-5 parts of ammonium persulfate in 20-30 parts of water to obtain an initiation solution for standby;
x2, adding 40-48 parts of composite side chain modifier into the aqueous solution of polyethylene glycol monoallyl ether obtained in the step X1, and mixing for 15-30 min; adding the mixed solution I after the mixing is completed, and continuously stirring for 15-30 min; then the temperature is raised to 60-80 ℃ and the initiating solution is added for reaction for 2-4 hours; cooling to normal temperature after the reaction is finished, and regulating the pH of the liquid to 6-8 by using a sodium hydroxide aqueous solution with the concentration of 30-40 wt%; filtering to obtain filtrate, namely the high-dispersion carboxylate polymer.
Preferably, each operation of step X2 is performed in an oxygen-free environment.
Preferably, in the step X2, the compound side chain modifier is methacrylic acid phosphate, vinyl phosphonic acid and vinyl acetate according to the mass ratio of (12-16): (1.25-2): 1.
Preferably, the mixing rate of the mixing in step X2 is 300 to 600rpm.
Preferably, the stirring rate of the reaction in step X2 is 180 to 360rpm.
In long-term production practice, the inventors have observed that the addition of highly dispersed carboxylate polymer to concrete, while giving it good dispersibility and workability, the degree of the dispersibility and workability is greatly affected by the length, morphology, etc. of the side chains, which results in large differences in hydration process of concrete under some unusual use environments such as severe weather, leading to unexpected overall water-reducing effect. In order to improve the stability of the high-dispersion carboxylate polymer, the inventor makes further improvement on the original basis, the carboxylate polymer is crosslinked through a long straight chain, the molecular configuration of the crosslinked carboxylate polymer is more stable, and meanwhile, the inventor also discovers that the steric hindrance of the crosslinked carboxylate polymer is further increased, so that the dispersion of concrete particles can be better promoted, and the fluidity of concrete can be improved. The use of the cross-linked carboxylate polymer as a water reducing agent component and addition to the concrete, after setting, exhibits a higher compressive strength, probably due to the fact that the structure of the concrete is optimized with lower porosity than before, after addition of the cross-linked carboxylate polymer.
Preferably, the preparation method of the crosslinked carboxylate polymer comprises the following raw materials in parts by weight:
9-12 parts of polyethylene glycol monoallyl ether is dissolved in 60-90 parts of water to obtain an aqueous solution of polyethylene glycol monoallyl ether for standby; dissolving 4-6 parts of sodium methacrylate sulfonate and 50-60 parts of acrylic acid in 40-80 parts of water to obtain a mixed solution I for later use; dissolving 3.5-5 parts of ammonium persulfate in 20-30 parts of water to obtain an initiation solution for standby; dissolving 0.8-1.5 parts of mercaptoethanol in 5-8 parts of water to obtain aqueous solution of mercaptoethanol for later use;
adding 40-48 parts of compound side chain modifier and 4-7.5 parts of 1, 6-hexanediol divinyl ether into an aqueous solution of polyethylene glycol monoallyl ether at the temperature of 40-50 ℃ and mixing for 30-60 min; after the mixing is finished, continuously adding the mixed solution I obtained in the step Y1, and continuously stirring for 15-30 min to obtain a mixed solution II for later use;
y3, raising the temperature of the mixed solution II to 60-80 ℃, adding the initiating solution obtained in the step Y1 and the aqueous solution of mercaptoethanol, and reacting for 3-6 h; cooling to normal temperature after the reaction is finished, and regulating the pH of the liquid to 6-8 by using a sodium hydroxide aqueous solution with the concentration of 30-40 wt%; filtering to obtain filtrate, namely the cross-linked carboxylate polymer.
Preferably, in the step Y2, the compound side chain modifier is methacrylic acid phosphate, vinyl phosphonic acid and vinyl acetate according to the mass ratio of (12-16): (1.25-2): 1.
Preferably, the mixing rate of the mixing in step Y2 is 300 to 600rpm.
Preferably, the stirring rate of the reaction in step Y2 is 180 to 360rpm.
Preferably, each of the operations in step Y2 and step Y3 is performed in an oxygen-free environment.
On the basis of conforming to the common knowledge in the field, the above preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the invention.
The raw materials in the formula of the invention are introduced and have the following functions:
defoaming agent: can reduce the surface tension of water, solution, suspension, etc., prevent foam formation, or reduce or eliminate original foam. The method is used for eliminating foam in the modified polycarboxylate superplasticizer.
Polyethylene glycol monoallyl ether: organic matter, the raw material in the invention.
Sodium methallyl sulfonate: white crystalline powder is easily soluble in water, slightly soluble in ethanol and dimethyl sulfoxide, and insoluble in other organic solvents. The invention is used as a raw material.
Acrylic acid: the organic compound is colorless liquid, has pungent smell, corrosiveness and stronger acidity. Has the property of being soluble in water, ethanol and diethyl ether, and also soluble in benzene, acetone, chloroform, etc. The chemical property is active, and is easy to polymerize in air. The invention is used as a monomer raw material for polymerization.
Ammonium persulfate: white crystalline powder, which is used as an initiator for polymerization in the present invention.
The invention has the beneficial effects that:
compared with the prior art, the invention introduces the phosphorus-containing groups with different chain lengths into the side chains of the polycarboxylate molecules, and realizes better steric hindrance effect by utilizing the phosphorus-containing groups so as to increase the dispersibility among the concrete particles.
Compared with the prior art, the phosphate group on the side chain of the modified polycarboxylate molecule has stronger complexing ability with calcium ions in concrete compared with the original carboxyl, thereby improving the adsorption ability of the modified polycarboxylate molecule on the surface of the concrete particles; because of the improvement of the adsorption capacity, the molecules of the modified polycarboxylate adsorbed on the particle surfaces are increased, so that the surfaces have higher electrostatic repulsive force and steric hindrance, and the dispersion of the concrete is facilitated.
Compared with the prior art, the cross-linked carboxylate polymer is cross-linked through a long straight chain, the molecular configuration of the cross-linked carboxylate polymer is more stable, and after the cross-linked carboxylate polymer prepared by the method is added, the concrete structure is optimized, and the compressive strength of the concrete is improved.
Detailed Description
The invention is further illustrated by means of the following examples, which are not intended to limit the scope of the invention. The experimental methods, in which specific conditions are not noted in the following examples, were selected according to conventional methods and conditions, or according to the commercial specifications.
The comparative example and the examples of the present invention have the following parameters of part of raw materials:
polyethylene glycol monoallyl ether, beijing Hua Weirui chemical industry limited, CAS number: 27274-31-3;
propylene glycol block polyether, south Africa chemical Co., ltd., CAS number: 9003-11-6;
methacrylic acid phosphate, cantonese Weng Jiang chemical company, CAS number: 52628-03-2;
1, 6-hexanediol divinyl ether, shanghai Jin Jinle Utility Co., ltd., CAS number: 19763-13-4.
Example 1
An environment-friendly water reducer consists of a high-dispersion carboxylate polymer and propylene glycol block polyether.
The propylene glycol block polyether was added in an amount of 0.1wt% of the highly dispersed carboxylate polymer.
The preparation method of the high-dispersion carboxylate polymer comprises the following steps:
x1, 9kg of polyethylene glycol monoallyl ether is dissolved in 75kg of water to obtain an aqueous solution of polyethylene glycol monoallyl ether for later use; dissolving 5.5kg of sodium methacrylate sulfonate and 50kg of acrylic acid in 80kg of water to obtain a mixed solution I for later use; 3.5kg of ammonium persulfate is dissolved in 25kg of water to obtain an initiation solution for standby;
under the protection of nitrogen, adding 43.5kg of composite side chain modifier into the aqueous solution of polyethylene glycol monoallyl ether obtained in the step X1, and mixing for 15min at the stirring speed of 450 rpm; adding the mixed solution I after the mixing is completed, and continuously stirring for 30min; subsequently, the temperature was raised to 70℃and an initiating solution was added, the stirring rate was reduced to 240rpm and reacted for 3 hours; cooling to normal temperature after the reaction is finished, and regulating the pH of the liquid to 7 by using a 30wt% sodium hydroxide aqueous solution; filtering to obtain filtrate, namely the high-dispersion carboxylate polymer.
The composite side chain modifier in the step X2 is phosphoric acid methacrylate and vinyl phosphonic acid with the mass ratio of 12: 1.5.
Example 2
An environment-friendly water reducer consists of a high-dispersion carboxylate polymer and propylene glycol block polyether.
The propylene glycol block polyether was added in an amount of 0.1wt% of the highly dispersed carboxylate polymer.
The preparation method of the high-dispersion carboxylate polymer comprises the following steps:
x1, 9kg of polyethylene glycol monoallyl ether is dissolved in 75kg of water to obtain an aqueous solution of polyethylene glycol monoallyl ether for later use; dissolving 5.5kg of sodium methacrylate sulfonate and 50kg of acrylic acid in 80kg of water to obtain a mixed solution I for later use; 3.5kg of ammonium persulfate is dissolved in 25kg of water to obtain an initiation solution for standby;
under the protection of nitrogen, adding 43.5kg of composite side chain modifier into the aqueous solution of polyethylene glycol monoallyl ether obtained in the step X1, and mixing for 15min at the stirring speed of 450 rpm; adding the mixed solution I after the mixing is completed, and continuously stirring for 30min; subsequently, the temperature was raised to 70℃and an initiating solution was added, the stirring rate was reduced to 240rpm and reacted for 3 hours; cooling to normal temperature after the reaction is finished, and regulating the pH of the liquid to 7 by using a 30wt% sodium hydroxide aqueous solution; filtering to obtain filtrate, namely the high-dispersion carboxylate polymer.
The composite side chain modifier in the step X2 is phosphoric acid methacrylate and vinyl acetate with the mass ratio of 12:1.
Example 3
An environment-friendly water reducer consists of a high-dispersion carboxylate polymer and propylene glycol block polyether.
The propylene glycol block polyether was added in an amount of 0.1wt% of the highly dispersed carboxylate polymer.
The preparation method of the high-dispersion carboxylate polymer comprises the following steps:
x1, 9kg of polyethylene glycol monoallyl ether is dissolved in 75kg of water to obtain an aqueous solution of polyethylene glycol monoallyl ether for later use; dissolving 5.5kg of sodium methacrylate sulfonate and 50kg of acrylic acid in 80kg of water to obtain a mixed solution I for later use; 3.5kg of ammonium persulfate is dissolved in 25kg of water to obtain an initiation solution for standby;
under the protection of nitrogen, adding 43.5kg of composite side chain modifier into the aqueous solution of polyethylene glycol monoallyl ether obtained in the step X1, and mixing for 15min at the stirring speed of 450 rpm; adding the mixed solution I after the mixing is completed, and continuously stirring for 30min; subsequently, the temperature was raised to 70℃and an initiating solution was added, the stirring rate was reduced to 240rpm and reacted for 3 hours; cooling to normal temperature after the reaction is finished, and regulating the pH of the liquid to 7 by using a 30wt% sodium hydroxide aqueous solution; filtering to obtain filtrate, namely the high-dispersion carboxylate polymer.
The composite side chain modifier in the step X2 is vinyl phosphonic acid and vinyl acetate in a mass ratio of 1.5: 1.
Example 4
An environment-friendly water reducer consists of a high-dispersion carboxylate polymer and propylene glycol block polyether.
The propylene glycol block polyether was added in an amount of 0.1wt% of the highly dispersed carboxylate polymer.
The preparation method of the high-dispersion carboxylate polymer comprises the following steps:
x1, 9kg of polyethylene glycol monoallyl ether is dissolved in 75kg of water to obtain an aqueous solution of polyethylene glycol monoallyl ether for later use; dissolving 5.5kg of sodium methacrylate sulfonate and 50kg of acrylic acid in 80kg of water to obtain a mixed solution I for later use; 3.5kg of ammonium persulfate is dissolved in 25kg of water to obtain an initiation solution for standby;
under the protection of nitrogen, adding 43.5kg of composite side chain modifier into the aqueous solution of polyethylene glycol monoallyl ether obtained in the step X1, and mixing for 15min at the stirring speed of 450 rpm; adding the mixed solution I after the mixing is completed, and continuously stirring for 30min; subsequently, the temperature was raised to 70℃and an initiating solution was added, the stirring rate was reduced to 240rpm and reacted for 3 hours; cooling to normal temperature after the reaction is finished, and regulating the pH of the liquid to 7 by using a 30wt% sodium hydroxide aqueous solution; filtering to obtain filtrate, namely the high-dispersion carboxylate polymer.
The compound side chain modifier in the step X2 is phosphoric acid methacrylate, vinyl phosphonic acid and vinyl acetate in a mass ratio of 12:1.5: 1.
Example 5
An environment-friendly water reducer consists of a cross-linked carboxylate polymer and propylene glycol block polyether.
The propylene glycol block polyether was added in an amount of 0.1wt% of the crosslinked carboxylate polymer.
The preparation method of the crosslinked carboxylate polymer comprises the following steps:
y1, 9kg of polyethylene glycol monoallyl ether is dissolved in 75kg of water to obtain an aqueous solution of polyethylene glycol monoallyl ether for later use; dissolving 5.5kg of sodium methacrylate sulfonate and 50kg of acrylic acid in 80kg of water to obtain a mixed solution I for later use; 3.5kg of ammonium persulfate is dissolved in 25kg of water to obtain an initiation solution for standby; dissolving 1.2kg of mercaptoethanol in 6kg of water to obtain aqueous solution of mercaptoethanol for later use;
under the protection of Y2 nitrogen, adding 43.5kg of composite side chain modifier and 4.6kg of 1, 6-hexanediol divinyl ether into an aqueous solution of polyethylene glycol monoallyl ether at 45 ℃ and mixing for 45 minutes at a stirring speed of 450 rpm; after the mixing is finished, continuously adding the mixed solution I obtained in the step Y1, and continuously stirring for 30min to obtain a mixed solution II for later use;
under the protection of Y3 nitrogen, the temperature of the mixed solution II is raised to 70 ℃, the initiation solution obtained in the step Y1 and the aqueous solution of mercaptoethanol are added, and the reaction is carried out for 4 hours at the stirring speed of 240 rpm; cooling to normal temperature after the reaction is finished, and regulating the pH of the liquid to 7 by using a 30wt% sodium hydroxide aqueous solution; filtering to obtain filtrate, namely the cross-linked carboxylate polymer.
The composite side chain modifier in the step Y2 is phosphoric acid methacrylate, vinyl phosphonic acid and vinyl acetate in a mass ratio of 12:1.5: 1.
Comparative example 1
An environment-friendly water reducer consists of carboxylate polymer and propylene glycol block polyether.
The propylene glycol block polyether was added in an amount of 0.1wt% of the carboxylate polymer.
The preparation method of the high-dispersion carboxylate polymer comprises the following steps:
x1, 9kg of polyethylene glycol monoallyl ether is dissolved in 75kg of water to obtain an aqueous solution of polyethylene glycol monoallyl ether for later use; dissolving 5.5kg of sodium methacrylate sulfonate and 50kg of acrylic acid in 80kg of water to obtain a mixed solution I for later use; 3.5kg of ammonium persulfate is dissolved in 25kg of water to obtain an initiation solution for standby;
under the protection of nitrogen, adding the aqueous solution of polyethylene glycol monoallyl ether obtained in the step X1 into the mixed solution I, and mixing for 15min at the stirring speed of 450 rpm; subsequently, the temperature was raised to 70℃and an initiating solution was added, the stirring rate was reduced to 240rpm and reacted for 3 hours; cooling to normal temperature after the reaction is finished, and regulating the pH of the liquid to 7 by using a 30wt% sodium hydroxide aqueous solution; filtering to obtain filtrate, namely the carboxylate polymer.
Test example 1
The water reducing performance test of the green environment-friendly water reducing agent is carried out with reference to the specific requirements in GB 8076-2008 concrete admixture. The cement for testing adopts C in clinker 3 The content of A is 5 percent, and the dihydrate gypsum is used as 32.5-grade ordinary Portland cement of the setting accelerator; the sand used for testing uses the sand in the zone II; selecting gravels with the particle size of 10mm for testing; the cement dosage is 305kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The amounts of cement, sand and stone are the same as those of the reference concrete; the addition amount of the green environment-friendly water reducer is 0.5 weight percent of cement. The concrete test block is manufactured and maintained according to the specific requirements of the standard. The test of the water reduction rate was performed with reference to the specific requirements of the 6.5.2 water reduction rate measurement. Each group tested 3 samples and the results averaged. The water reducing performance test results of the green environment-friendly water reducer are shown in table 1.
TABLE 1
| Test set | Water reduction Rate (%) |
| Example 1 | 34.7 |
| Example 2 | 31.9 |
| Example 3 | 29.5 |
| Example 4 | 37.1 |
| Example 5 | 43.8 |
| Comparative example 1 | 25.4 |
The water reducing rate reflects the strength of the water reducing capability of the water reducing agent. As can be seen from the comparison of the above examples and comparative examples, the polycarboxylate water reducer has high water-reducing efficiency. Example 5 has an optimal water reduction capacity as high as 43.8% compared to the other examples. The addition of a small amount of the water reducer prepared in the embodiment 5 can greatly reduce the addition amount of water, and is beneficial to saving the consumption of raw materials. The reason for this may be that the side chain incorporates a phosphorus-containing group which can provide a larger steric hindrance than the carbon linear structure, and the steric hindrance of the carboxylate polymer after crosslinking is further increased, and the dispersion of the concrete particles can be better promoted to enhance the water-reducing ability.
Test example 2
The slump test of the green environment-friendly water reducer is carried out with reference to the specific requirements of slump and slump 1h time-varying quantity measurement in GB 8076-2008 concrete admixture. The parameters and the addition amount of the cement, sand, stone and water reducer for test are the same as those in test example 1. The slump cylinder is a cone cylinder welded by thin steel plates, the upper surface and the lower surface of the slump cylinder are parallel and perpendicular to the axis of the cone, two handles are welded at the two sides outside the cylinder, foot pedals are welded at the two sides near the lower end, the inner surface of the cone cylinder is smooth and has no bulge or recess, and the inner dimension of the slump cylinder is as follows: the diameter of the bottom is 200mm, the diameter of the top is 100mm, the height is 300mm, and the thickness of the cylinder wall is 2mm. The diameter of the tamping rod is 16mm, the length is 600mm, and the end part is rounded. The rest of the operations were carried out according to standard specific procedures, the concrete mix slump being expressed in cm, five samples being tested per group, the results being averaged and the exact value being 0.5cm. Slump test results of the green and environment-friendly water reducer are shown in table 2.
TABLE 2
The water reducer belongs to one of the surfactants, and under the condition that the cement ratio of the concrete is unchanged, the addition amount and slump of the water reducer are positively correlated. Slump objectively reflects the fluidity and dispersibility of concrete. As can be seen from the comparison of the above examples and comparative examples, the water reducing agent prepared in example 5 has an optimal dispersing effect on concrete, probably because the general polycarboxylate superplasticizer attaches to the surface of concrete particles by physical adsorption accompanied by small amount of complexation of carboxyl groups and calcium ions in the concrete, the complexation ability of carboxyl groups and calcium ions is limited, phosphate groups are included in phosphorus-containing groups, and after phosphate groups are added, the phosphate groups and calcium ions have a stronger complexation ability, further increase the chemical adsorption ability, and example 5 has better dispersibility than other examples or comparative examples under the dual effects of physical and chemical adsorption.
Test example 3
The invention relates to a method for testing the influence of an environment-friendly water reducer on the concrete pressure resistance, which is carried out according to the specific requirements of GB/T50081-2019 'test method Standard for physical and mechanical properties of concrete'. The concrete materials and parameters, amounts of addition were the same as those in test example 1. The test specimen was a cubic standard specimen with a side length of 150 mm. The preparation and maintenance of the sample refer to the specific requirements of the standard, and the standard maintenance age is 28d. Compressive strength was measured by a hydraulic universal mechanical tester (WAW-300B model, available from Jinan times test instruments Co., ltd.) and the results were averaged for 3 samples per group. The compressive strength results of concrete samples added with the green and environment-friendly water reducer are shown in Table 3.
TABLE 3 Table 3
| Test set | 28d compressive Strength (MPa) |
| Example 1 | 51.7 |
| Example 2 | 48.2 |
| Example 3 | 44.9 |
| Example 4 | 54.4 |
| Example 5 | 61.2 |
| Comparative example 1 | 41.6 |
The compressive strength reflects the strength limit of concrete when externally applied pressure. As can be seen from the comparison of the above examples and comparative examples, the crosslinked carboxylate polymer prepared by the present invention can improve the 28d compressive strength of concrete after being added as a water reducing agent to the concrete. The reason for this may be that the structure of the concrete is optimized after the addition of the cross-linked carboxylate polymer, and has a lower porosity than before, so that the concrete exhibits a higher compressive strength after solidification.
The foregoing describes in detail preferred embodiments of the present invention. It should be understood that numerous modifications and variations can be made in accordance with the concepts of the invention by one of ordinary skill in the art without undue burden. Therefore, all technical solutions which can be obtained by logic analysis, reasoning or limited experiments based on the prior art by the person skilled in the art according to the inventive concept shall be within the scope of protection defined by the claims.
Claims (6)
1. The utility model provides a green environmental protection water-reducing agent which characterized in that: the green environment-friendly water reducer consists of a modified polycarboxylate high-efficiency water reducer and a defoaming agent; the modified polycarboxylate superplasticizer is a cross-linked carboxylate polymer;
the preparation method of the crosslinked carboxylate polymer comprises the following raw materials in parts by weight:
9-12 parts of polyethylene glycol monoallyl ether is dissolved in 60-90 parts of water to obtain an aqueous solution of polyethylene glycol monoallyl ether for standby; dissolving 4-6 parts of sodium methacrylate sulfonate and 50-60 parts of acrylic acid in 40-80 parts of water to obtain a mixed solution I for later use; dissolving 3.5-5 parts of ammonium persulfate in 20-30 parts of water to obtain an initiation solution for standby; dissolving 0.8-1.5 parts of mercaptoethanol in 5-8 parts of water to obtain aqueous solution of mercaptoethanol for later use;
adding 40-48 parts of compound side chain modifier and 4-7.5 parts of 1, 6-hexanediol divinyl ether into an aqueous solution of polyethylene glycol monoallyl ether at the temperature of 40-50 ℃ and mixing for 30-60 min; after the mixing is finished, continuously adding the mixed solution I obtained in the step Y1, and continuously stirring for 15-30 min to obtain a mixed solution II for later use;
y3, raising the temperature of the mixed solution II to 60-80 ℃, adding the initiating solution obtained in the step Y1 and the aqueous solution of mercaptoethanol, and reacting for 3-6 h; cooling to normal temperature after the reaction is finished, and regulating the pH of the liquid to 6-8 by using a sodium hydroxide aqueous solution with the concentration of 30-40 wt%; filtering to obtain filtrate, namely the cross-linked carboxylate polymer;
the composite side chain modifier in the step Y2 is phosphoric acid methacrylate, vinyl phosphonic acid and vinyl acetate in a mass ratio of (12-16): (1.25-2): 1.
2. The green environmental protection water reducing agent according to claim 1, wherein: the defoaming agent is at least one of polyether defoaming agent, high-carbon alcohol defoaming agent and fatty acid defoaming agent.
3. The green environmental protection water reducing agent according to claim 1, wherein: the addition amount of the defoaming agent is 0.01-0.2 wt% of the modified polycarboxylate superplasticizer.
4. The green environmental protection water reducing agent according to claim 1, wherein: each operation of step Y2 is performed in an oxygen-free environment.
5. The green environmental protection water reducing agent according to claim 1, wherein: the mixing rate of the mixing in step Y2 is 300 to 600rpm.
6. The green environmental protection water reducing agent according to claim 1, wherein: the stirring rate of the reaction in the step Y3 is 180-360 rpm.
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