CN114276045A - Multi-effect concrete water reducing agent - Google Patents
Multi-effect concrete water reducing agent Download PDFInfo
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- CN114276045A CN114276045A CN202111634544.XA CN202111634544A CN114276045A CN 114276045 A CN114276045 A CN 114276045A CN 202111634544 A CN202111634544 A CN 202111634544A CN 114276045 A CN114276045 A CN 114276045A
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Abstract
The invention provides a multi-effect concrete water reducing agent, which is prepared by the following steps: uniformly mixing and stirring mother liquor of a polycarboxylate superplasticizer, a retarder, calcium saccharate, a defoaming agent, a water-retaining agent, sodium hexametaphosphate and water to obtain mixed liquor; and adding the air entraining agent into the mixed solution, and uniformly stirring to obtain the multi-effect concrete water reducing agent. The invention adopts the compounding of two kinds of polycarboxylate superplasticizer mother liquor, thus overcoming the functional limitation of a single-component water reducing agent; moreover, the sodium hexametaphosphate is added into the multi-effect concrete water reducing agent, so that the expansion performance of concrete can be effectively improved, and meanwhile, the water reducing agent also has strong water retention, working performance and adaptability.
Description
Technical Field
The invention relates to the technical field of concrete admixtures, in particular to a multi-effect concrete water reducing agent.
Background
The concrete has the characteristics of convenient raw material source, convenient construction, low energy consumption, low cost, capability of consuming a large amount of industrial waste residues and the like, so that under the actual condition that the modern science and technology is changed day by day, the concrete still serves as a building material with the largest consumption, particularly the formula amount of the Chinese concrete accounts for about half of the whole world, and the concrete admixture is one of important components of the modern concrete. The concrete admixture can improve the working performance, the technological performance and the production strengthening process of fresh concrete, can also improve and enhance the quality and the weather resistance of buildings and members, and plays an important role in promoting the development and progress of concrete technology.
In the concrete admixture, the water reducing agent is undoubtedly the heaviest, and the using amount of the water reducing agent accounts for more than 4/5 of the using amount of all the concrete admixture according to statistics. The water reducing agents commonly used at present mainly comprise lignosulfonate, naphthalene water reducing agents and polycarboxylic acid water reducing agents, and among various water reducing agents, the polycarboxylic acid water reducing agents are emphasized due to the characteristics of strong controllability of molecular structures, low mixing amount, high water reducing rate, capability of improving the durability of concrete, shortening the setting time, improving the slump loss of common concrete too fast, environmental protection and the like, so that the polycarboxylic acid water reducing agents are the highest-performance water reducing agents with highest technical content, optimal performance in all aspects and maximum application potential in the additive industry at present.
The adaptability between concrete admixture and cement is a problem which is difficult to overcome all the time, and the polycarboxylic acid water reducing agent is no exception. The adaptability of the water reducing agent and the cement can be influenced by the components, the specific surface area, the alkali content, the type and the mixing amount of the gypsum and the like of the cement. The research shows that: c in cement3The higher the A content, the larger the specific surface area, and the higher the alkali content, which results in poor concrete fluidity. The research shows that: the gypsum mixing amount and the crystallization form have great influence on the adsorption behavior of the carboxylic acid water reducing agent on the surface of cement particles, thereby influencing the dispersion of the cement particles. Along with the increase of the mixing amount of the gypsum, the soluble concentration in the solution is increased, and the soluble concentration and the polycarboxylate water reducing agent form a competitive adsorption situation, so that the adsorption rate of the polycarboxylic acid is reduced sharply, and the adsorption and dispersion effects of the polycarboxylate water reducing agent are seriously influenced. In addition to this, SO4 contained in the cement2-The ions also have a relatively large influence on their use. Large amount of SO4 2-Ions can directly influence the adsorption capacity of the polycarboxylate superplasticizer molecules on cement particles, so that the water reducing effect of the polycarboxylate superplasticizer is greatly weakened, and the problem of bleeding is caused. Research and engineering practice shows that after the water reducing agent is mixed into cement, the water reducing agent usually has poor adaptability to the cement and is suitable for the cementSensitive mud content of sandstone aggregate, unstable workability of fresh concrete and the like.
Chinese patent CN 108101407A discloses a polycarboxylic acid series composite water reducing agent and a preparation method thereof, wherein the polycarboxylic acid series composite water reducing agent comprises the following components in parts by weight: 50-60 parts of polycarboxylic acid water reducing agent, 30-40 parts of aliphatic water reducing agent, 15-20 parts of propanesulfonic acid, 10-15 parts of air entraining agent, 10-15 parts of triethanolamine and 3-5 parts of chlorohydrocarbon.
Chinese patent CN 107117853A discloses a concrete high-efficiency composite water reducing agent and application thereof, the invention is a composite water reducing agent prepared by using 10-40 parts of polycarboxylic acid mother liquor, 4-15 parts of air entraining agent, 15-30 parts of hydrophilic colloid, 0.1-1 part of retarder, 0.8-2 parts of mirabilite, 1-5 parts of wood calcium, 5-20 parts of cellulose water-retaining material and 30-70 parts of water as raw materials, the composite water reducing agent has the performances of slow release, slump retention, early strength, high strength, water retention and the like, the unit water consumption of concrete is greatly reduced, the composite water reducing agent is applied to the preparation of concrete, the compactness of the concrete can be improved, the cement consumption is greatly reduced, the shrinkage is reduced, the stability of the concrete is improved, the characteristics of low dosage and remarkable effect are realized when the composite water reducing agent is used in the concrete, the environment is friendly, and has good economic and social benefits, the invention does not solve the adaptability problem of the composite water reducing agent and the cement.
Disclosure of Invention
In view of the defects of the prior art, the invention provides the multiple-effect concrete water reducing agent which has good working performance and good adaptability with cement, and meanwhile, the multiple-effect concrete water reducing agent can effectively improve the expansion performance of concrete, reduce the generation of cracks in the concrete and improve the durability of the concrete.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
a multi-effect concrete water reducing agent comprises the following components in parts by weight: 20-50 parts of polycarboxylic acid water reducing agent mother liquor, 1-2 parts of retarder, 2-8 parts of sugar calcium, 0.2-0.5 part of defoaming agent, 10-20 parts of water-retaining agent, 3-6 parts of sodium hexametaphosphate, 0.5-1.0 part of air entraining agent and 50-70 parts of water.
The preparation method of the multi-effect concrete water reducer comprises the following steps:
s1, uniformly mixing and stirring 20-50 parts of polycarboxylate superplasticizer mother liquor, 1-2 parts of retarder, 2-8 parts of calcium saccharate, 0.2-0.5 part of defoamer, 10-20 parts of water-retaining agent, 3-6 parts of sodium hexametaphosphate and 50-70 parts of water to obtain a mixed solution;
s2, adding 0.5-1.0 part of air entraining agent into the mixed liquid obtained in the step S1, and uniformly stirring to obtain the multi-effect concrete water reducing agent.
The inventor finds that the expansion performance of concrete can be effectively improved and cracks can be effectively avoided by adding sodium hexametaphosphate into the multi-effect concrete water reducing agent.
The polycarboxylate superplasticizer mother liquor is one or a mixture of two or more of water-reducing polycarboxylate superplasticizer mother liquor, slump-retaining polycarboxylate superplasticizer mother liquor and viscosity-reducing polycarboxylate superplasticizer mother liquor.
The preferable polycarboxylic acid mother liquor is the mixture of the water-reducing polycarboxylic acid mother liquor and the slump-retaining polycarboxylic acid mother liquor; the mass percentages of the two are 50-90% of the mother solution of the water-reducing polycarboxylic acid water reducing agent and 10-50% of the mother solution of the slump-retaining polycarboxylic acid water reducing agent.
The composite of the two kinds of polycarboxylate superplasticizer mother liquor can overcome the limitation of the performance of a single kind of polycarboxylate superplasticizer, achieve the purpose of controlling the initial working state of fresh concrete and the concrete slump loss over time, effectively reduce the dosage of mixed water, improve the defects of easy segregation, bleeding and poor workability of concrete, and improve the working performance of concrete.
The preferred retarder is a modified carrageenan. The retarder can be adsorbed on the surface of cement particles to form a film, and the requirement of adjusting the hardening time of concrete is met by delaying the crystallization hardening of hydration products, so that the workability of the concrete can be improved, the quality of the concrete is improved, and meanwhile, the water reducing effect is achieved;
further, the preparation method of the modified carrageenan comprises the following steps:
1) putting the carrageenin powder in a drying oven at 30-40 ℃ for drying for 20-24h, crushing and sieving with a 80-120 mesh sieve to obtain crushed carrageenin powder for later use;
2) weighing 10-15g of the crushed carrageenan powder prepared in the step 1), and uniformly dispersing the powder in 100-150mL of ethanol aqueous solution with the mass concentration of 70-95 wt% to obtain a dispersion liquid; adding 4-6mL of 10-20 wt% sodium hydroxide aqueous solution into the dispersion; heating the reaction solution to 30-40 ℃; after reacting for 1-2h, adding 4-6g of sodium chloroacetate, and continuing to react for 3-4h at 30-40 ℃; cooling to 20-25 deg.C, adjusting pH to 6.0-7.0 with 0.5-1mol/L acetic acid water solution, vacuum filtering, collecting filter cake, and washing the filter cake with 70-95 wt% ethanol water solution for 2-3 times; and (3) placing the filter cake at 30-40 ℃ and placing the filter cake in a constant-temperature drying oven for drying for 20-24h to obtain the modified carrageenan.
The air entraining agent is a composite air entraining agent and consists of sodium dodecyl benzene sulfonate and sodium dodecyl sulfate in a mass ratio of 1:2-3, the composite air entraining agent is an anionic surfactant, and the molecular structure of the composite air entraining agent contains hydrophilic groups and hydrophobic groups, so that the surface tension of water can be obviously reduced, a large amount of uniformly distributed fine bubbles are generated in the concrete mixing process, the purpose of controlling the air content of the concrete is achieved, the strength of the concrete and the durability of freeze-thaw resistance circulation are controlled, and the workability of fresh concrete is improved.
The defoaming agent is an organic silicon defoaming agent, is mainly used for eliminating the number of harmful bubbles introduced by the mother liquor of the polycarboxylate superplasticizer and by mechanical stirring, can improve the foaming problem in the stirring process of cement mortar, and has favorable effects on the strength and the durability of concrete.
Preferably, the water-retaining agent is modified sodium cellulose; the surface activity of the water-retaining agent ensures that the cementing material is easy to be uniformly distributed in a mortar system, so that the cementing material is stable, and the pumping difficulty caused by the water loss of cement mortar can be reduced.
Further, the preparation method of the modified sodium carboxymethylcellulose comprises the following steps:
weighing 10-20g of sodium carboxymethylcellulose, dissolving in 500mL of 300-90 wt% water, heating the solution to 75-90 ℃, introducing nitrogen for 5-10min, dropwise adding 3-5g of 30-50 wt% potassium persulfate aqueous solution, continuously introducing nitrogen for 30-40min, dropwise adding 3-5g of 30-50 wt% potassium persulfate aqueous solution, after the potassium persulfate aqueous solution is dropwise added, carrying out heat preservation reaction for 10-30min, adding 5-10g of sodium p-styrenesulfonate, reacting for 0.5-1h, dropwise adding 3-5g of 30-50 wt% potassium persulfate aqueous solution, after the potassium persulfate aqueous solution is dropwise added, reacting for 10-20min, dropwise adding 8-10g of methyl methacrylate, after dropwise adding, carrying out constant-temperature stirring reaction for 3-5h to obtain white latex, adding 100mL of 70-90 wt% ethanol aqueous solution into the white latex, standing, precipitating, filtering, collecting precipitate, washing the precipitate with water, drying in a vacuum drying oven at 60-80 deg.C for 20-24 hr to obtain crude product, washing the crude product with chloroform for 2-3 times, and drying in a vacuum drying oven at 60-80 deg.C for 20-24 hr to obtain modified sodium carboxymethylcellulose.
The technical idea of the invention is as follows: by compounding the water reducing agent mother liquor and the slump-retaining water reducing agent mother liquor, the functional limitation of a single-component water reducing agent is overcome, the water consumption is effectively reduced, and the defects of easy segregation and poor workability of concrete are overcome; the hydrophilic modified carrageenan is added, so that the consistency of the aqueous solution can be increased under the condition of very low aqueous solution concentration, the expansion degree of concrete is not influenced while the consistency of the concrete is increased, and the pressure of concrete pumping is reduced; the composite air entraining agent is selected, has good adaptability with the polycarboxylic acid mother liquor, good inducing effect and strong stability of introduced bubbles, is suitable for being matched with the defoaming agent for use, and can improve the pore structure of concrete; the defoaming agent and the air entraining agent are selected for use together, so that the foaming problem in the concrete mortar stirring process can be solved; modified sodium carboxymethylcellulose is introduced as a water-retaining agent, the surface activity of the modified sodium carboxymethylcellulose ensures that a cementing material is easy to uniformly distribute in a mortar system, so that the cementing material is stable, and meanwhile, the pumping difficulty caused by the water loss of cement mortar can be reduced, a part of polar groups in the modified sodium carboxymethylcellulose can be anchored on the surfaces of cement particles and can perform certain chemical reaction with the cement particles to form a high polymer with certain mechanical strength, some nonpolar high polymer chains extend into the cement-based material to form a net structure, conditions are provided for interweaving a hydration product, and the breaking strength and the toughness of a cement-based material sample can be improved to a certain extent.
Compared with the prior art, the invention has the beneficial effects that:
1. the composite of two kinds of polycarboxylate superplasticizer mother liquor is adopted, so that the functional limitation of a single-component water reducing agent is overcome, and the performance superposition of two different water reducing agents is realized;
2. the modified sodium carboxymethylcellulose can effectively improve the intersolubility of the defoaming agent, the air entraining agent and the polycarboxylate superplasticizer mother liquor, and can ensure that the multi-effect concrete superplasticizer is stably stored for a long time without layering;
3. the multi-effect concrete water reducing agent prepared by the invention has stronger water retention, good working performance and good adaptability with cement;
4. the multi-effect concrete water reducing agent prepared by the invention can endow concrete with good expansibility, reduce the generation of cracks in the concrete and prolong the durability of the concrete.
Detailed Description
The sources of some of the raw materials used in the examples of the present invention are as follows, and the raw materials used in the examples can be obtained from conventional commercial sources or can be prepared by conventional methods, unless otherwise specified:
the water-reducing polycarboxylic acid mother liquor is purchased from Shandong tiger chemical technology Co., Ltd, is a light yellow liquid in appearance, has a pH value of 6-8, a solid content of 20 +/-1% and a water reducing rate of 20-40%.
The slump-retaining polycarboxylic acid mother liquor is purchased from Wuhan Huaxuan high and new technology Limited company, the model is KH-6, and the water reduction rate is more than or equal to 30 percent.
Carrageenan purchased from denying cheng biotechnology ltd, denying, and having a powdered appearance and a food-grade type.
Sodium dodecyl benzene sulfonate, purchased from Nanjing Milan chemical Co., Ltd., is white or pale yellow powder in appearance, has an HLB value of 10.6 and a decomposition temperature of 450 ℃.
Sodium lauryl sulfate, purchased from Kyowa Seisakusho chemical Co., Ltd, model number SLS, melting point 204-.
The organic silicon defoaming agent is purchased from Changzhou Shunhua chemical industry Co., Ltd, the model is XPJ-S210, the appearance is milky fluid, the pH is 6-8, and the solid content is 10% -40%.
Sodium chloroacetate, purchased from Shandong Liang New Material science and technology Co., Ltd, was solid in appearance and was LA-8X in type.
Sodium carboxymethylcellulose, purchased from Xinseiyang cellulose works, Wen' an county, 99% in content, having a pH of 5.0-7.5.
Potassium persulfate purchased from chemical Limited of Jinan Haobang, and having an appearance of white crystalline powder, heavy metal (in pb) of not more than 0.0005%, iron of not more than 0.001%, free acid (in H)2SO4Calculated by the total weight of the active oxygen is less than or equal to 0.10 percent, and the active oxygen is more than or equal to 5.86 percent.
Sodium p-styrenesulfonate, purchased from Jining Sanshi Biotech, Inc., was a white crystalline solid in appearance and rated as technical grade.
Comparative example
A preparation method of a multi-effect concrete water reducing agent comprises the following steps:
s1, weighing the raw materials according to the formula, mixing 50g of polycarboxylate superplasticizer mother liquor, 2g of carrageenan, 5g of calcium saccharate, 0.5g of organic silicon defoamer, 20g of sodium carboxymethylcellulose and 60g of water, and uniformly stirring at the temperature of 30 ℃ to obtain a mixed solution; the polycarboxylate superplasticizer mother liquor is a mixture of a water-reducing polycarboxylate superplasticizer mother liquor and a slump-retaining polycarboxylate superplasticizer mother liquor in a mass ratio of 3: 1.
S2, adding 1g of air entraining agent into the mixed liquid obtained in the step S1, and uniformly stirring at the temperature of 30 ℃ to obtain the multi-effect concrete water reducing agent; the air entraining agent is a mixture of sodium dodecyl benzene sulfonate and sodium dodecyl sulfate in a mass ratio of 1: 2.
Example 1
A preparation method of a multi-effect concrete water reducing agent comprises the following steps:
s1, weighing the raw materials according to the formula, mixing 50g of polycarboxylate superplasticizer mother liquor, 2g of modified carrageenan, 5g of calcium saccharate, 0.5g of organic silicon defoamer, 20g of sodium carboxymethylcellulose and 60g of water, and uniformly stirring at the temperature of 30 ℃ to obtain a mixed solution; the polycarboxylate superplasticizer mother liquor is a mixture of a water-reducing polycarboxylate superplasticizer mother liquor and a slump-retaining polycarboxylate superplasticizer mother liquor in a mass ratio of 3: 1.
S2, adding 1g of air entraining agent into the mixed liquid obtained in the step S1, and uniformly stirring at the temperature of 30 ℃ to obtain the multi-effect concrete water reducing agent; the air entraining agent is a mixture of sodium dodecyl benzene sulfonate and sodium dodecyl sulfate in a mass ratio of 1: 2.
The preparation method of the modified carrageenan comprises the following steps:
1) putting the carrageenan powder in a drying oven at 40 ℃ for drying for 24h, crushing and sieving with a 100-mesh sieve to obtain crushed carrageenan powder for later use;
2) weighing 10g of the crushed carrageenan powder prepared in the step 1), and uniformly dispersing the powder in 100mL of 70 wt% ethanol aqueous solution to obtain a dispersion liquid; 5mL of a 20% (w/w) aqueous solution of sodium hydroxide was added to the dispersion; heating the reaction solution to 40 ℃; after reacting for 2h, adding 6g of sodium chloroacetate, and continuing to react for 3h at 40 ℃; cooling to 20 ℃, adjusting the pH value of the solution to 7.0 by using 0.5mol/L acetic acid aqueous solution, performing suction filtration, collecting a filter cake, and washing the filter cake for 3 times by using 70 wt% ethanol aqueous solution; and (3) placing the filter cake at 40 ℃ and placing the filter cake in a constant-temperature drying oven for drying for 24h to obtain the modified carrageenan.
Example 2
A preparation method of a multi-effect concrete water reducing agent comprises the following steps:
s1, weighing the raw materials according to the formula, mixing 50g of polycarboxylate superplasticizer mother liquor, 2g of carrageenan, 5g of calcium saccharate, 0.5g of organic silicon defoamer, 20g of modified sodium carboxymethylcellulose and 60g of water, and uniformly stirring at the temperature of 30 ℃ to obtain a mixed solution; the polycarboxylate superplasticizer mother liquor is a mixture of a water-reducing polycarboxylate superplasticizer mother liquor and a slump-retaining polycarboxylate superplasticizer mother liquor in a mass ratio of 3: 1;
s2, adding 1g of air entraining agent into the mixed liquid obtained in the step S1, and uniformly stirring at the temperature of 30 ℃ to obtain the multi-effect concrete water reducing agent; the air entraining agent is a mixture of sodium dodecyl benzene sulfonate and sodium dodecyl sulfate in a mass ratio of 1: 2.
The preparation method of the modified sodium carboxymethylcellulose comprises the following steps:
weighing 15g of sodium carboxymethylcellulose, dissolving in 300mL of water, heating the solution to 80 ℃, introducing nitrogen for 10min, 5g of 50 wt% potassium persulfate aqueous solution is dripped, nitrogen is continuously introduced for 30min, 5g of 50 wt% potassium persulfate aqueous solution is dripped, after the dripping of the potassium persulfate aqueous solution is finished, keeping the temperature for reaction for 30min, adding 10g of sodium p-styrenesulfonate, reacting for 0.5h, dropwise adding 5g of 50 wt% potassium persulfate aqueous solution, after the potassium persulfate aqueous solution is completely dropwise added, after the reaction is carried out for 20min, 10g of methyl methacrylate is dripped, after the dripping is finished, the reaction is carried out for 3h under constant temperature stirring to obtain white latex, 100mL of 75 wt% ethanol water solution is added into the white latex, the white latex is kept stand, precipitates are separated out, the precipitates are filtered, collected, washed by water and then dried in a vacuum drying oven at 80 ℃ for 24h to obtain a crude product, the crude product is washed by chloroform for 3 times and then dried in the vacuum drying oven at 80 ℃ for 24h to obtain the modified sodium carboxymethylcellulose.
Example 3
A preparation method of a multi-effect concrete water reducing agent comprises the following steps:
s1, weighing the raw materials according to the formula, mixing 50g of polycarboxylate superplasticizer mother liquor, 2g of modified carrageenan, 5g of calcium saccharate, 0.5g of organic silicon defoamer, 20g of modified sodium carboxymethylcellulose and 60g of water, and uniformly stirring at the temperature of 30 ℃ to obtain a mixed solution; the polycarboxylate superplasticizer mother liquor is a mixture of a water-reducing polycarboxylate superplasticizer mother liquor and a slump-retaining polycarboxylate superplasticizer mother liquor in a mass ratio of 3: 1.
S2, adding 1g of air entraining agent into the mixed liquid obtained in the step S1, and uniformly stirring at the temperature of 30 ℃ to obtain the multi-effect concrete water reducing agent; the air entraining agent is a mixture of sodium dodecyl benzene sulfonate and sodium dodecyl sulfate in a mass ratio of 1: 2.
The preparation method of the modified carrageenan comprises the following steps:
1) putting the carrageenan powder in a drying oven at 40 ℃ for drying for 24h, crushing and sieving with a 100-mesh sieve to obtain crushed carrageenan powder for later use;
2) weighing 10g of the crushed carrageenan powder prepared in the step 1), and uniformly dispersing the powder in 100mL of 70 wt% ethanol aqueous solution to obtain a dispersion liquid; 5mL of a 20 wt% aqueous solution of sodium hydroxide was added to the dispersion; heating the reaction solution to 40 ℃; after reacting for 2h, adding 6g of sodium chloroacetate, and continuing to react for 3h at 40 ℃; cooling to 20 ℃, adjusting the pH value of the solution to 7.0 by using 0.5mol/L acetic acid aqueous solution, performing suction filtration, collecting a filter cake, and washing the filter cake for 3 times by using 70 wt% ethanol aqueous solution; and (3) placing the filter cake at 40 ℃ and placing the filter cake in a constant-temperature drying oven for drying for 24h to obtain the modified carrageenan.
The preparation method of the modified sodium carboxymethylcellulose comprises the following steps:
weighing 15g of sodium carboxymethylcellulose, dissolving in 300mL of water, heating the solution to 80 ℃, introducing nitrogen for 10min, 5g of 50 wt% potassium persulfate aqueous solution is dripped, nitrogen is continuously introduced for 30min, 5g of 50 wt% potassium persulfate aqueous solution is dripped, after the dripping of the potassium persulfate aqueous solution is finished, keeping the temperature for reaction for 30min, adding 10g of sodium p-styrenesulfonate, reacting for 0.5h, dropwise adding 5g of 50 wt% potassium persulfate aqueous solution, after the potassium persulfate aqueous solution is completely dropwise added, after the reaction is carried out for 20min, 10g of methyl methacrylate is dripped, after the dripping is finished, the reaction is carried out for 3h under constant temperature stirring to obtain white latex, 100mL of 75 wt% ethanol water solution is added into the white latex, the white latex is kept stand, precipitates are separated out, the precipitates are filtered, collected, washed by water and then dried in a vacuum drying oven at 80 ℃ for 24h to obtain a crude product, the crude product is washed by chloroform for 3 times and then dried in the vacuum drying oven at 80 ℃ for 24h to obtain the modified sodium carboxymethylcellulose.
Example 4
A preparation method of a multi-effect concrete water reducing agent comprises the following steps:
s1, weighing the raw materials according to a formula, mixing 50g of polycarboxylic acid water reducer mother liquor, 2g of modified carrageenan, 5g of calcium saccharate, 0.5g of organic silicon defoamer, 20g of modified sodium carboxymethylcellulose, 5g of sodium hexametaphosphate and 60g of water, and uniformly stirring at the temperature of 30 ℃ to obtain a mixed solution; the polycarboxylate superplasticizer mother liquor is a mixture of a water-reducing polycarboxylate superplasticizer mother liquor and a slump-retaining polycarboxylate superplasticizer mother liquor in a mass ratio of 3: 1;
s2, adding 1g of air entraining agent into the mixed liquid obtained in the step S1, and uniformly stirring at the temperature of 30 ℃ to obtain the multi-effect concrete water reducing agent; the air entraining agent is a mixture of sodium dodecyl benzene sulfonate and sodium dodecyl sulfate in a mass ratio of 1: 2.
The preparation method of the modified carrageenan is the same as that of the example 3, and the details are not repeated.
The preparation method of the modified sodium carboxymethylcellulose is the same as that of example 3, and is not repeated herein.
Test example
Testing the fluidity of the cement paste: according to GB/T8077-2012, namely a concrete admixture homogeneity test method, a test object is a multi-effect concrete water reducing agent prepared in a comparative example and examples 1-3, a certain amount of water reducing agent and water are added into a certain amount of cement (Sanxia P042.5), and the test is carried out after stirring, wherein the error is generally not more than 5mm, and the concrete operation steps are as follows:
(1) the glass plate with the size of 400mm multiplied by 5mm is placed in a horizontal position, and the glass plate, the truncated cone round die, the stirrer and the stirring pot are wiped by wet cloth, so that the surface of the glass plate is wet and has no water stain. Placing a truncated cone mould in the center of a glass plate, and covering the truncated cone mould with wet cloth for later use; (2) weighing 300g of cement, pouring the cement into a stirring pot, weighing a multi-effect concrete water reducing agent with the solid content (accounting for the mass of the cement) of 0.3 percent into 105g of water, and mixing and stirring the water reducing agent and the cement; (3) putting the mixed cement paste into a cement paste mixer, stirring for 120s, standing for 15s, and then quickly stirring for 120 s; (4) pouring the stirred cement into a truncated cone circular mold placed on a glass plate, balancing the truncated cone circular mold, lifting the truncated cone circular mold in the vertical direction, so that the cement freely flows on the glass plate, and the cement flows for 30 seconds until cement paste is not expanded; (5) and measuring the maximum length in the vertical direction by using a steel ruler, and taking the average value as the test result of the fluidity of the cement paste. The specific test results are shown in table 1.
Table 1: fluidity of cement paste
| Fluidity of cement paste (mm) | |
| Comparative example | 230 |
| Example 1 | 250 |
| Example 2 | 260 |
| Example 3 | 280 |
Concrete is prepared according to standard JGJ 55-2011 'common concrete mix proportion design engineering', the mix proportion is 360kg (Sanxia P042.5), 637kg of stone powder sand, 273kg of machine-made sand, 637kg of stone 1(5-20mm), 273kg of stone 2(15-31.5mm), 7.2kg of multi-effect concrete water reducer and 170kg of water, and the prepared concrete is subjected to bleeding rate and freeze-thaw resistance tests.
And (3) measuring the bleeding rate of the concrete: according to the test of GB/T8076-2008 'concrete admixture specification', a 5L cylinder with a cover (the inner diameter is 185cm, the height is 200mm) is wetted by wet cloth, the concrete mixture is put into the cylinder, vibrated on a vibration table for 20s, then slightly smoothed by a spatula, and covered to prevent water evaporation. The surface of the sample should be 20mm lower than the edge of the opening. Calculating time from smearing, precipitating bleeding once every 10min in the first 60min by using a pipette, and absorbing water once every 20min later until no bleeding exists for three times continuously. 5min before each water absorption, the bottom side of the cylinder should be raised by about 20mm, and the cylinder should be inclined to facilitate water absorption. After water absorption, the cylinder was gently laid flat and covered. Injecting the water sucked out each time into a measuring cylinder with a plug, finally calculating the total bleeding amount to be accurate to 1g, and calculating the bleeding rate according to the following formula:
Gw＝Gl-G0
in the formula: b- -bleeding rate,%;
VW-total mass of bleeding in grams (g);
w- -the water consumption of the concrete mixture, in grams (g);
g- -total mass of concrete mixture in grams (G);
GW-sample mass in grams (g);
g1- -Cartridge and sample Mass in grams (G);
G0-cylinder mass in grams (g).
During the test, one sample is taken from each batch of concrete mixture, and the bleeding rate is the arithmetic average value of the three samples, and the accuracy is 0.1%. If the difference between the maximum value or the minimum value of the three samples and the intermediate value is larger than 15% of the intermediate value, the maximum value and the minimum value are both omitted, the intermediate value is taken as the bleeding rate of the group of tests, and if the differences between the maximum value and the minimum value and the intermediate value are both larger than 15% of the intermediate value, the test is repeated. The bleeding rate test data is shown in table 2:
table 2: bleeding rate of concrete
| Bleeding Rate (%) | |
| Comparative example | 6.53％ |
| Example 1 | 3.25％ |
| Example 2 | 3.08％ |
| Example 3 | 1.50％ |
And (3) durability test: the antifreezing test is carried out according to the standard GB/T50082-2009 Standard test method for the long-term performance and durability of the common concrete. The specific test method is as follows: preparing the prepared concrete into a test block with the size of 100mm multiplied by 100mm, curing the test block in a standard curing box for 28 days, then immersing the test block into water with the temperature of 18-20 ℃ until the top surface of the test block is submerged under the water for more than 20mm, and performing freeze-thaw test after immersing the test block for 4 days. And after soaking, taking out the test block, wiping off the moisture on the surface of the test block by using a wet cloth, weighing the test block to obtain the quality of the test block, numbering the test block, and putting the test block into a freezing box to start a freeze-thaw test. The freezing temperature of the anti-freezing test is kept between-20 ℃ and-18 ℃. And (3) freezing the test block for 4 hours, immediately taking out the test block, immersing the test block into water at 18-20 ℃ for melting for 4 hours, after the freezing and thawing cycle is finished, performing the next freezing and thawing cycle, keeping the test block to be compared in a standard curing box until the freezing and thawing cycle is finished for 50 times, and simultaneously performing a compression test on the test block and the anti-freezing test block. In the test process, the freeze-thaw test piece is subjected to appearance inspection once every 25 times of circulation, when a seriously damaged test piece is found, the test piece is immediately weighed, and if the average weight loss rate of the test piece is more than 5%, the freeze-thaw cycle test can be stopped.
The test may be stopped when one of the following three conditions occurs during the freeze-thaw cycle:
1) the specified number of cycles has been reached.
2) The loss rate of the compressive strength reaches 25 percent.
3) The mass loss rate reaches 5 percent.
4) The strength loss rate after the freeze-thaw cycle test should be calculated according to the following formula.
Δfc＝(fc0-fcn)/fc0×100％
Delta fc-concrete strength loss rate after freeze-thaw cycle, calculated (%) as the average of 3 test pieces;
fc0-average compressive strength (MPa) of the comparative test pieces;
fcnaverage compressive strength (MPa) of 3 test pieces after N freeze-thaw cycles.
Δωn＝(G0-G1)/G0×100％
Δωn-mass loss rate after N freeze-thaw cycles, calculated as the average of 3 test pieces (%);
g0- -test piece mass (G) before freeze-thaw cycling test;
gn- -test piece mass (g) after N freeze-thaw cycles.
The freeze-thaw resistance test data of the concrete is shown in table 3:
table 3: freezing and thawing resistance of concrete
F200 is a rating for concrete frost resistance, and represents no more than 5% mass loss, no more than 40% decrease in dynamic elastic modulus, or no more than 25% decrease in strength after 200 freeze-thaw cycles of the concrete. The multi-effect concrete water reducing agent prepared by the invention can obviously improve the freeze-thaw resistance of concrete and the durability of the concrete when being applied to the concrete, and meets the requirement of environmental development.
Test example 4
The test is carried out by referring to the limited expansion rate test method specified in appendix A in GB 23439-2017 concrete expanding agent; the test results are shown in Table 4.
Test materials and amounts:
| material | Quality of material |
| 42.5 grade ordinary portland cement | 607.5±2.0g |
| Water reducing agent of example 3 or example 4 | 10.0+0.1g |
| Standard sand | 1350.0±5.0g |
| Mixing water | 190.0+1.0g |
TABLE 4 testing of the expansion Properties of the concretes
| Limiting expansion rate after 24 days of oxidation | |
| Example 3 | 0.8×10-4 |
| Example 4 | 2.1×10-4 |
As can be seen from Table 4, the expansion performance of the concrete prepared by adding the multi-effect concrete water reducing agent prepared by adding sodium hexametaphosphate in example 4 is better than that of the multi-effect concrete water reducing agent prepared by adding no sodium hexametaphosphate in example 3. The reason for this may be: the addition of a proper amount of sodium hexametaphosphate can optimize the pore structure of the concrete and provide favorable conditions for the macroscopic expansion of the concrete.
Claims (6)
1. The multi-effect concrete water reducing agent is characterized by comprising the following components in parts by weight: 20-50 parts of polycarboxylic acid water reducing agent mother liquor, 1-2 parts of retarder, 2-8 parts of sugar calcium, 0.2-0.5 part of defoaming agent, 10-20 parts of water-retaining agent, 3-6 parts of sodium hexametaphosphate, 0.5-1.0 part of air entraining agent and 50-70 parts of water.
2. The multi-effect concrete water reducer of claim 1, characterized in that: the polycarboxylate superplasticizer mother liquor is one or a mixture of two or more of water-reducing polycarboxylate superplasticizer mother liquor, slump-retaining polycarboxylate superplasticizer mother liquor and viscosity-reducing polycarboxylate superplasticizer mother liquor.
3. The multi-effect concrete water reducer of claim 1, characterized in that: the retarder is modified carrageenan; the preparation method of the modified carrageenan comprises the following steps:
1) putting the carrageenin powder in a drying oven at 30-40 ℃ for drying for 20-24h, crushing and sieving with a 80-120 mesh sieve to obtain crushed carrageenin powder for later use;
2) weighing 10-15g of the crushed carrageenan powder prepared in the step 1), and uniformly dispersing the powder in 100-150mL of ethanol aqueous solution with the mass concentration of 70-95 wt% to obtain a dispersion liquid; adding 4-6mL of 10-20 wt% sodium hydroxide aqueous solution into the dispersion; heating the reaction solution to 30-40 ℃; after reacting for 1-2h, adding 4-6g of sodium chloroacetate, and continuing to react for 3-4h at 30-40 ℃; cooling to 20-25 deg.C, adjusting pH to 6.0-7.0 with 0.5-1mol/L acetic acid water solution, vacuum filtering, collecting filter cake, and washing the filter cake with 70-95 wt% ethanol water solution for 2-3 times; and (3) placing the filter cake at 30-40 ℃ and placing the filter cake in a constant-temperature drying oven for drying for 20-24h to obtain the modified carrageenan.
4. The multi-effect concrete water reducer of claim 1, characterized in that: the air entraining agent consists of sodium dodecyl benzene sulfonate and sodium dodecyl sulfate in a mass ratio of 1: 2-3.
5. The multi-effect concrete water reducer of claim 1, characterized in that: the defoaming agent is an organic silicon defoaming agent.
6. The multi-effect concrete water reducer of claim 1, characterized in that: the water-retaining agent is modified sodium carboxymethylcellulose;
the preparation method of the modified sodium carboxymethylcellulose comprises the following steps:
weighing 10-20g of sodium carboxymethylcellulose, dissolving in 500mL of 300-90 wt% water, heating the solution to 75-90 ℃, introducing nitrogen for 5-10min, dropwise adding 3-5g of 30-50 wt% potassium persulfate aqueous solution, continuously introducing nitrogen for 30-40min, dropwise adding 3-5g of 30-50 wt% potassium persulfate aqueous solution, after the potassium persulfate aqueous solution is dropwise added, carrying out heat preservation reaction for 10-30min, adding 5-10g of sodium p-styrenesulfonate, reacting for 0.5-1h, dropwise adding 3-5g of 30-50 wt% potassium persulfate aqueous solution, after the potassium persulfate aqueous solution is dropwise added, reacting for 10-20min, dropwise adding 8-10g of methyl methacrylate, after dropwise adding, carrying out constant-temperature stirring reaction for 3-5h to obtain white latex, adding 100mL of 70-90 wt% ethanol aqueous solution into the white latex, standing, precipitating, filtering, collecting precipitate, washing the precipitate with water, drying in a vacuum drying oven at 60-80 deg.C for 20-24 hr to obtain crude product, washing the crude product with chloroform for 2-3 times, and drying in a vacuum drying oven at 60-80 deg.C for 20-24 hr to obtain modified sodium carboxymethylcellulose.
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