CN114276045B - Multi-effect concrete water reducing agent - Google Patents
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Abstract
The invention provides a multi-effect concrete water reducer, which is prepared by the following steps: the polycarboxylate water reducer mother liquor, retarder, sugar calcium, defoamer, water-retaining agent, sodium hexametaphosphate and water are mixed and stirred uniformly to obtain mixed liquor; and adding the air entraining agent into the mixed solution, and uniformly stirring to obtain the multi-effect concrete water reducer. The invention adopts the combination of two polycarboxylate water reducer mother solutions, and overcomes the functional limitation of a single-component water reducer; furthermore, the sodium hexametaphosphate is added into the multi-effect concrete water reducer, so that the expansion performance of concrete can be effectively improved, and meanwhile, the water reducer has strong water retention, working performance and adaptability.
Description
Technical Field
The invention relates to the technical field of concrete additives, in particular to a multi-effect concrete water reducing agent.
Background
The concrete has the characteristics of convenient raw material sources, convenient construction, low energy consumption, low cost, large consumption of industrial waste residues and the like, so that the concrete is still the building material with the largest dosage under the actual condition of the current technology day-to-day variation, and especially the square quantity of Chinese concrete is about half of the world, and the concrete additive is one of the important components of the modern concrete. The concrete admixture can not only improve the working performance of fresh concrete, improve the process performance and strengthen the production process, but also improve and enhance the quality and weather resistance of buildings and components, and plays a vital role in promoting the development and progress of concrete technology.
In the concrete admixture, the water reducing agent is of great importance, and the water reducing agent accounts for more than 4/5 of the total concrete admixture. Among a plurality of water reducing agent varieties, the polycarboxylic acid water reducing agent has the characteristics of strong molecular structure controllability, low mixing amount, high water reducing rate, high concrete durability, shortened setting time, excessively fast slump loss of common concrete, environmental protection and the like, and is a high-performance water reducing agent with the forefront of the current additive industry, highest technical content, optimal performance in all aspects, maximum application potential.
The adaptability between the concrete admixture and cement has been a problem which is difficult to overcome, and the polycarboxylate water reducer is no exception. Cement composition, specific surface area, alkali content, gypsum type and amount of gypsumThe adaptability of the water reducer and cement can be affected equally. Studies have shown that: c in cement 3 The higher the A content, the larger the specific surface area, and the higher the alkali content, resulting in deterioration of the fluidity of the concrete. Studies have shown that: the gypsum mixing amount and the crystal form have a great influence on the adsorption behavior of the carboxylic acid water reducer on the surface of cement particles, so that the dispersion of the cement particles is influenced. With the increase of the mixing amount of gypsum, the soluble concentration in the solution is increased, so that a competitive adsorption situation is formed with the polycarboxylate water reducer, the adsorption rate of the polycarboxylate is rapidly reduced, and the adsorption and dispersion effects of the polycarboxylate water reducer are seriously affected. In addition to this, SO4 contained in cement 2- The effect of ions on their use is also relatively large. High amounts of SO 4 2- Ions can directly influence the adsorption quantity of the polycarboxylate water reducer molecules on cement particles, so that the water reducing effect of the water reducer is greatly weakened, and the bleeding problem occurs. Research and engineering practice show that after the water reducer is doped into cement, the problems of poor adaptability of the water reducer and cement, sensitivity to the mud content of sand aggregate, unstable workability of fresh concrete and the like can be generally encountered.
Chinese patent CN 108101407A discloses a polycarboxylic acid type composite water reducing agent and a preparation method thereof, the polycarboxylic acid type composite water reducing agent comprises the following components in parts by weight: 50-60 parts of polycarboxylic acid water reducer, 30-40 parts of aliphatic water reducer, 15-20 parts of propane sulfonic acid, 10-15 parts of air entraining agent, 10-15 parts of triethanolamine and 3-5 parts of chlorinated hydrocarbon.
The invention discloses a high-efficiency composite water reducing agent for concrete and application thereof, wherein the high-efficiency composite water reducing agent is prepared from 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 calcium lignan, 5-20 parts of cellulose water-retaining material and 30-70 parts of water as raw materials.
Disclosure of Invention
In view of the defects of the prior art, the invention provides a multi-effect concrete water reducer, which has good working performance and good adaptability to cement, 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 above object, the present invention adopts the following technical scheme:
the multi-effect concrete water reducer comprises the following components in parts by weight: 20-50 parts of polycarboxylate water reducer mother liquor, 1-2 parts of retarder, 2-8 parts of sugar calcium, 0.2-0.5 part of defoamer, 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 water reducer mother liquor, 1-2 parts of retarder, 2-8 parts of sugar calcium, 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;
and S2, adding 0.5-1.0 part of air entraining agent into the mixed solution obtained in the step S1, and uniformly stirring to obtain the multi-effect concrete water reducer.
The inventor finds that the expansion performance of the concrete can be effectively improved and cracks can be effectively avoided by adding sodium hexametaphosphate into the multi-effect concrete water reducer.
The polycarboxylate water reducer mother liquor is one or a mixture of two or more of water-reducing polycarboxylate water reducer mother liquor, slump-retaining polycarboxylate water reducer mother liquor and viscosity-reducing polycarboxylate water reducer mother liquor.
The preferable polycarboxylic acid mother liquor is a mixture of a water-reducing polycarboxylic acid mother liquor and a slump retaining polycarboxylic acid mother liquor; the mass percentage of the two is 50-90% of water-reducing type polycarboxylate superplasticizer mother liquor and 10-50% of slump-retaining type polycarboxylate superplasticizer mother liquor.
By adopting the combination of two polycarboxylate water reducer mother solutions, the limitation of the performance of a single type of polycarboxylate water reducer can be overcome, the purposes of controlling the initial working state of fresh concrete and the time-dependent loss of concrete slump are achieved, the consumption of mixing water can be effectively reduced, the defects of easy segregation, bleeding and poor workability of concrete are overcome, and the working performance of the concrete is improved.
The preferred retarder is 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 deferring 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) Drying carrageenan powder in a drying oven at 30-40deg.C for 20-24 hr, pulverizing, and sieving with 80-120 mesh sieve to obtain pulverized carrageenan powder;
2) Weighing 10-15g of the crushed carrageenan powder prepared in the step 1), and uniformly dispersing the carrageenan powder in 100-150mL of ethanol aqueous solution with the mass concentration of 70-95 wt%; adding 4-6mL of 10-20wt% sodium hydroxide aqueous solution to the dispersion; heating the reaction solution to 30-40 ℃; after reacting for 1-2h, adding 4-6g sodium chloroacetate, and continuing to react for 3-4h at 30-40 ℃; cooling to 20-25deg.C, adjusting pH to 6.0-7.0 with 0.5-1mol/L acetic acid aqueous solution, vacuum filtering, collecting filter cake, and washing the filter cake with 70-95wt% ethanol aqueous solution for 2-3 times; and (3) placing the filter cake in a constant temperature drying oven at 30-40 ℃ for drying for 20-24 hours 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, wherein the mass ratio of the sodium dodecyl benzene sulfonate to the sodium dodecyl sulfate is 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 fine bubbles uniformly distributed in the mixing process of concrete can be generated, the aim of controlling the air content of the concrete can be achieved, the strength of the concrete structure and the durability of freeze-thawing cycle can be controlled, and the workability of fresh concrete can be improved.
The defoaming agent is an organic silicon defoaming agent, is mainly used for eliminating the quantity of harmful bubbles introduced by the polycarboxylate water reducer mother liquor and by mechanical stirring, can improve the foaming problem in the stirring process of cement mortar, and has a beneficial effect on the strength and 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 uniformly distribute in a mortar system, so that the cementing material is stable, and meanwhile, the pumping difficulty caused by water loss of cement mortar can be reduced.
Further, the preparation method of the modified sodium carboxymethyl cellulose comprises the following steps:
10-20g of sodium carboxymethyl cellulose is weighed and dissolved in 300-500mL of water, the solution is heated to 75-90 ℃, after nitrogen is introduced for 5-10min, 3-5g of 30-50wt% of potassium persulfate aqueous solution is dripped, after nitrogen is continuously introduced for 30-40min, 3-5g of 30-50wt% of potassium persulfate aqueous solution is dripped, after the dripping of the potassium persulfate aqueous solution is finished, the reaction is carried out for 10-30min while keeping the temperature, 5-10g of sodium p-styrenesulfonate is added, after the reaction is carried out for 0.5-1h, 3-5g of 30-50wt% of potassium persulfate aqueous solution is dripped, after the dripping of the potassium persulfate aqueous solution is finished, 8-10g of methyl methacrylate is dripped, after the dripping is finished, stirring is carried out at constant temperature for 3-5h, white latex is obtained, 100-200mL of 70-90wt% of ethanol aqueous solution is added into the white latex, the white latex is subjected to standing, precipitation is filtered, the precipitation is collected, the precipitation is washed by water, and then the obtained after the precipitation is dried in a vacuum drying oven for 20-24h, the crude cellulose is dried for 20-80 h, and the crude cellulose is obtained after the crude cellulose is dried for 20-20 h, and the crude cellulose is dried by the vacuum drying oven for 2-80 h.
The technical conception of the invention: the method has the advantages that through the combination of the water-reducing type water reducer mother liquor and the slump retaining type water reducer mother liquor, the limitation of the functions of a single-component water reducer 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 concentration of the aqueous solution, the aqueous solution does not influence the expansion degree of concrete while increasing the consistency of the concrete, and the pressure during concrete pumping is reduced; the composite air entraining agent is selected, has good adaptability and good inducing effect with the polycarboxylic acid mother liquor, has stronger stability for introducing bubbles, is suitable for being matched with a defoaming agent for use, and can improve the pore structure of concrete; the foam killer is used together with the air entraining agent, so that the foaming problem in the stirring process of the concrete mortar can be improved; the modified sodium carboxymethyl cellulose is introduced as a water-retaining agent, the surface activity of the modified sodium carboxymethyl cellulose ensures that a cementing material is easy to uniformly distribute in a mortar system, so that the cementing material is stable, meanwhile, the pumping difficulty caused by water loss of cement mortar can be reduced, a part of polar groups in the modified sodium carboxymethyl cellulose can be anchored on the surfaces of cement particles and react with the cement particles to form a polymer with certain mechanical strength, some nonpolar polymer chains extend into a cement-based material to form a network structure, and the fracture strength and toughness of a cement-based material sample can be improved to a certain extent by providing conditions for interweaving of a hydration product.
Compared with the prior art, the invention has the beneficial effects that:
1. the two polycarboxylate water reducer mother solutions are compounded, so that the functional limitation of a single-component water reducer is overcome, and the performance superposition of two different water reducers is realized;
2. the use of the modified sodium carboxymethyl cellulose can effectively improve the intersolubility of the defoamer, the air entraining agent and the mother solution of the polycarboxylate superplasticizer, so that the multi-effect concrete superplasticizer can be stably stored for a long time and does not have layering phenomenon;
3. the multi-effect concrete water reducer prepared by the invention has stronger water retention property, good working performance and good adaptability to cement;
4. the multi-effect concrete water reducer 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 in the examples of the present invention are as follows, and the raw materials used in the examples are all available from conventional commercial sources or can be prepared by conventional methods unless specifically indicated otherwise:
the water-reducing polycarboxylic acid mother liquor is purchased from Shandong Dong tiger chemical engineering Co., ltd, and has a light yellow liquid appearance, a pH value of 6-8, a solid content of 20+ -1% and a water reducing rate of 20-40%.
The slump retaining type polycarboxylic acid mother liquor is purchased from Wuhan Hua Xuan high technology Co., ltd, and is of the model KH-6, and the water reducing rate is more than or equal to 30 percent.
Carrageenan, purchased from atangate biosciences, inc. In biotechnology, has a powdery appearance and a food grade.
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 dodecyl sulfate, which is purchased from Changzhou commercial company chemical industry Co., ltd, model SLS, melting point 204-207, and white or light yellow powder appearance.
The organic silicon defoamer is purchased from Changzhou cisco chemical industry Co., ltd, model XPJ-S210, the appearance is a milky white fluid, the pH is 6-8, and the solid content is 10% -40%.
Sodium chloroacetate purchased from Shandong Liang New Material technology Co., ltd.) has a solid appearance and model LA-8X.
Sodium carboxymethyl cellulose is purchased from Xinsaiyang cellulose factory, wen' an county, the content is 99%, and the pH value is 5.0-7.5.
Potassium persulfate purchased from Jinan Haobao chemical Co., ltd.) has the appearance of white crystal powder, heavy metal (calculated as pb) of less than or equal to 0.0005%, and iron of less than or equal to 0.001% of free acid (calculated as H) 2 SO 4 Calculated by the weight, 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 biotechnology Co., ltd.) is white crystalline solid in appearance and is of industrial grade.
Comparative example
A preparation method of a multi-effect concrete water reducer comprises the following steps:
s1, weighing raw materials according to a formula, mixing 50g of polycarboxylate superplasticizer mother liquor, 2g of carrageenan, 5g sugar calcium, 0.5g of organosilicon defoamer, 20g of sodium carboxymethylcellulose and 60g of water uniformly at a temperature of 30 ℃ to obtain a mixed solution; the polycarboxylate water reducer mother liquor is the mixture of water-reducing polycarboxylate water reducer mother liquor and slump-retaining polycarboxylate water reducer mother liquor with the mass ratio of 3:1.
S2, adding 1g of air entraining agent into the mixed solution obtained in the step S1, and uniformly stirring at the temperature of 30 ℃ to obtain a multi-effect concrete water reducer; 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 reducer comprises the following steps:
s1, weighing raw materials according to a formula, mixing 50g of polycarboxylate superplasticizer mother liquor, 2g of modified carrageenan, 5g of sugar calcium, 0.5g of organosilicon defoamer, 20g of sodium carboxymethylcellulose and 60g of water uniformly at a temperature of 30 ℃ to obtain a mixed solution; the polycarboxylate water reducer mother liquor is the mixture of water-reducing polycarboxylate water reducer mother liquor and slump-retaining polycarboxylate water reducer mother liquor with the mass ratio of 3:1.
S2, adding 1g of air entraining agent into the mixed solution obtained in the step S1, and uniformly stirring at the temperature of 30 ℃ to obtain a multi-effect concrete water reducer; 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) Drying carrageenan powder in a drying oven at 40 ℃ for 24 hours, 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 carrageenan powder in 100mL of ethanol aqueous solution with the mass concentration of 70 wt%; adding 5mL of 20% (w/w) sodium hydroxide aqueous solution to the dispersion; heating the reaction solution to 40 ℃; after 2h of reaction, 6g of sodium chloroacetate is added, and the reaction is continued for 3h at 40 ℃; cooling to 20 ℃, regulating the pH value of the solution to 7.0 by using 0.5mol/L acetic acid aqueous solution, carrying out suction filtration, collecting a filter cake, and washing the filter cake for 3 times by using 70wt% ethanol aqueous solution; and (5) placing the filter cake in a constant temperature drying oven at 40 ℃ for drying for 24 hours to obtain the modified carrageenan.
Example 2
A preparation method of a multi-effect concrete water reducer comprises the following steps:
s1, weighing raw materials according to a formula, mixing 50g of polycarboxylate superplasticizer mother liquor, 2g of carrageenan, 5g sugar calcium, 0.5g of organosilicon defoamer, 20g of modified sodium carboxymethylcellulose and 60g of water uniformly at a temperature of 30 ℃ and stirring to obtain a mixed solution; the polycarboxylate water reducer mother liquor is prepared by mixing water-reducing polycarboxylate water reducer mother liquor and slump-retaining polycarboxylate water reducer mother liquor in a mass ratio of 3:1;
s2, adding 1g of air entraining agent into the mixed solution obtained in the step S1, and uniformly stirring at the temperature of 30 ℃ to obtain a multi-effect concrete water reducer; 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 carboxymethyl cellulose comprises the following steps:
15g of sodium carboxymethyl cellulose is weighed and dissolved in 300mL of water, the solution is heated to 80 ℃, nitrogen is introduced for 10min, 5g of 50wt% potassium persulfate aqueous solution is dripped, nitrogen is continuously introduced for 30min, 5g of 50wt% potassium persulfate aqueous solution is dripped, after the dripping of the potassium persulfate aqueous solution is finished, the reaction is carried out for 30min, 10g of sodium p-styrenesulfonate is added, 5g of 50wt% potassium persulfate aqueous solution is dripped after the reaction for 0.5h, after the dripping of the potassium persulfate solution is finished, 10g of methyl methacrylate is dripped after the reaction for 20min, stirring is carried out at constant temperature for 3h, white latex is obtained, 100mL of 75wt% ethanol aqueous solution is added into the white latex, standing is carried out, precipitation is carried out, filtering, precipitation is collected, the precipitate is washed by water, the obtained precipitate is dried in a vacuum drying oven at 80 ℃ for 24h, the obtained crude product is washed with chloroform for 3 times, and the crude product is dried in a vacuum drying oven at 80 ℃ for 24h, and the modified sodium carboxymethyl cellulose is obtained.
Example 3
A preparation method of a multi-effect concrete water reducer comprises the following steps:
s1, weighing raw materials according to a formula, mixing 50g of polycarboxylate superplasticizer mother liquor, 2g of modified carrageenan, 5g of sugar calcium, 0.5g of organosilicon defoamer, 20g of modified sodium carboxymethylcellulose and 60g of water uniformly at a temperature of 30 ℃ and stirring to obtain a mixed solution; the polycarboxylate water reducer mother liquor is the mixture of water-reducing polycarboxylate water reducer mother liquor and slump-retaining polycarboxylate water reducer mother liquor with the mass ratio of 3:1.
S2, adding 1g of air entraining agent into the mixed solution obtained in the step S1, and uniformly stirring at the temperature of 30 ℃ to obtain a multi-effect concrete water reducer; 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) Drying carrageenan powder in a drying oven at 40 ℃ for 24 hours, 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 carrageenan powder in 100mL of ethanol aqueous solution with the mass concentration of 70 wt%; adding 5mL of a 20wt% sodium hydroxide aqueous solution to the dispersion; heating the reaction solution to 40 ℃; after 2h of reaction, 6g of sodium chloroacetate is added, and the reaction is continued for 3h at 40 ℃; cooling to 20 ℃, regulating the pH value of the solution to 7.0 by using 0.5mol/L acetic acid aqueous solution, carrying out suction filtration, collecting a filter cake, and washing the filter cake for 3 times by using 70wt% ethanol aqueous solution; and (5) placing the filter cake in a constant temperature drying oven at 40 ℃ for drying for 24 hours to obtain the modified carrageenan.
The preparation method of the modified sodium carboxymethyl cellulose comprises the following steps:
15g of sodium carboxymethyl cellulose is weighed and dissolved in 300mL of water, the solution is heated to 80 ℃, nitrogen is introduced for 10min, 5g of 50wt% potassium persulfate aqueous solution is dripped, nitrogen is continuously introduced for 30min, 5g of 50wt% potassium persulfate aqueous solution is dripped, after the dripping of the potassium persulfate aqueous solution is finished, the reaction is carried out for 30min, 10g of sodium p-styrenesulfonate is added, 5g of 50wt% potassium persulfate aqueous solution is dripped after the reaction for 0.5h, after the dripping of the potassium persulfate solution is finished, 10g of methyl methacrylate is dripped after the reaction for 20min, stirring is carried out at constant temperature for 3h, white latex is obtained, 100mL of 75wt% ethanol aqueous solution is added into the white latex, standing is carried out, precipitation is carried out, filtering, precipitation is collected, the precipitate is washed by water, the obtained precipitate is dried in a vacuum drying oven at 80 ℃ for 24h, the obtained crude product is washed with chloroform for 3 times, and the crude product is dried in a vacuum drying oven at 80 ℃ for 24h, and the modified sodium carboxymethyl cellulose is obtained.
Example 4
A preparation method of a multi-effect concrete water reducer comprises the following steps:
s1, weighing raw materials according to a formula, mixing 50g of polycarboxylate superplasticizer mother liquor, 2g of modified carrageenan, 5g of sugar calcium, 0.5g of organic silicon defoamer, 20g of modified sodium carboxymethylcellulose, 5g of sodium hexametaphosphate and 60g of water, and uniformly stirring at a temperature of 30 ℃ to obtain a mixed solution; the polycarboxylate water reducer mother liquor is prepared by mixing water-reducing polycarboxylate water reducer mother liquor and slump-retaining polycarboxylate water reducer mother liquor in a mass ratio of 3:1;
s2, adding 1g of air entraining agent into the mixed solution obtained in the step S1, and uniformly stirring at the temperature of 30 ℃ to obtain a multi-effect concrete water reducer; 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 example 3, and is not repeated here.
The preparation method of the modified sodium carboxymethyl cellulose is the same as that of example 3, and is not repeated here.
Test case
Testing the fluidity of cement paste: according to GB/T8077-2012 "concrete admixture homogeneity test method", test objects are comparative examples, multi-effect concrete water reducing agents prepared in examples 1-3, a certain amount of water reducing agent and water are added into a certain amount of cement (Sanxia P042.5), the test is carried out after stirring, the error is generally not more than 5mm, and the specific operation steps are as follows:
(1) The glass plate with the dimensions of 400mm x 5mm was placed in a horizontal position and the glass plate, truncated conical round mold, stirrer and stirrer pan were rubbed with a wet cloth so that the surface thereof was wet without water stains. Placing a truncated cone mold in the center of a glass plate and covering the truncated cone mold with wet cloth for later use; (2) 300g of cement is weighed, poured into a stirring pot, and then 105g of water is added with the multi-effect concrete water reducer with the folding and fixing mixing amount (accounting for 0.3% of the mass of the cement) and mixed with the cement for stirring; (3) Stirring the mixed cement paste in a cement paste stirrer for 120s, standing for 15s, and then rapidly stirring for 120s; (4) Pouring the stirred cement into a truncated cone circular mould placed on a glass plate, balancing the truncated cone circular mould, lifting the truncated cone circular mould in the vertical direction to enable the cement to freely flow on the glass plate, and flowing for 30 seconds until the cement paste is not expanded; (5) The maximum length in the vertical direction is measured by a steel ruler, and the average value is taken as the testing result of the fluidity of the cement paste. The specific test results are shown in Table 1.
Table 1: fluidity of cement paste
| Fluidity (mm) of cement paste | |
| Comparative example | 230 |
| Example 1 | 250 |
| Example 2 | 260 |
| Example 3 | 280 |
The concrete is prepared by referring to a standard JGJ 55-2011 common concrete mix proportion design project, the mix proportion is 360kg of cement (Sanxia P042.5), 637kg of stone powder sand, 273kg of machine-made sand, 637kg of stone 1 (5-20 mm), 273kg of stone 2 (15-31.5 mm), 7.2kg of multi-effect concrete water reducer and 170kg of water, and the bleeding rate and the freeze-thawing resistance of the prepared concrete are tested.
Determination of concrete bleeding rate: according to GB/T8076-2008 "concrete admixture rule" test, a covered cylinder (with an inner diameter of 185cm, a height of 200 mm) having a volume of 5L is wetted with wet cloth, a concrete mixture is put into the cylinder, vibrated on a vibrating table for 20s, and then lightly trowelled with a spatula, and covered to prevent moisture evaporation. The surface of the sample should be 20mm lower than the edge of the nozzle. Calculating time from plastering, bleeding with a liquid suction pipe at intervals of 10min for the first 60min, and absorbing water at intervals of 20min until no bleeding occurs three times continuously. Before each water absorption, 5min before each water absorption, one side of the cylinder bottom should be raised by about 20mm, so that the cylinder is inclined to facilitate water absorption. After water absorption, the cartridge was gently placed flat and capped. The water sucked out each time is poured into a measuring cylinder with a plug, and finally the total bleeding amount is calculated to be accurate to 1g, and the bleeding rate is calculated according to the following formula:
G w ＝G l -G 0
wherein: b—bleeding rate,%;
V W -total mass of bleeding in grams (g);
w- -the water consumption of the concrete mixture in grams (g);
g- -the total mass of the concrete mixture in grams (G);
G W sample mass in grams (g);
g1-the mass of the cylinder and the sample in grams (G);
G 0 barrel mass in grams (g).
In the test, one sample was taken from each batch of concrete mix and the bleeding rate was taken as the arithmetic average of the three samples to the nearest 0.1%. If one of the maximum or minimum values of the three samples differs from the intermediate value by more than 15%, the maximum value is discarded together with the minimum value, the intermediate value is taken as the bleeding rate for the set of tests, and if the differences between the maximum value and the minimum value and the intermediate value are both more than 15%, the test should be repeated. Bleeding rate test data are shown in table 2:
table 2: concrete bleeding rate
| Bleeding Rate (%) | |
| Comparative example | 6.53％ |
| Example 1 | 3.25％ |
| Example 2 | 3.08％ |
| Example 3 | 1.50％ |
Durability test: the antifreeze test is carried out by referring to standard GB/T50082-2009 Standard of method for testing the long-term Performance and durability of ordinary concrete. The specific test method is as follows: the prepared concrete is made into test blocks with the dimensions of 100mm multiplied by 100mm, the test blocks are maintained in a standard curing box for 28 days, then the test blocks are immersed in water with the temperature of 18-20 ℃ to require that the top surfaces of the test blocks are immersed in water for more than 20mm, and freeze thawing test is carried out after the test blocks are immersed for 4 days. After the soaking is finished, taking out the test block, wiping the water on the surface of the test block by using wet cloth, weighing the mass of the test block, numbering the test block, and then placing the test block into a freezer to start a freeze thawing test. The freezing temperature of the freeze resistance test was maintained at-20- -18 ℃. And immediately taking out the test block after freezing for 4 hours, immersing the test block in water at 18-20 ℃ to melt for 4 hours, and after the thawing, namely after the freeze-thawing cycle is finished, keeping the test block to be compared in a standard curing box until the freeze-thawing cycle is finished for 50 times, and carrying out compression test with the freeze-proof test block. In the test process, the freeze thawing test piece is subjected to appearance inspection once every 25 cycles, when the severely 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 thawing cycle test can be stopped.
The test may be stopped when the freeze-thaw cycle occurs in one of three conditions:
1) The prescribed number of cycles has been reached.
2) The loss rate of compressive strength reaches 25 percent.
3) The mass loss rate reaches 5 percent.
4) The intensity loss rate of the freeze-thawing cycle test is calculated according to the following formula.
Δf c ＝(f c0 -f cn )/f c0 ×100％
Δfc—the loss rate of concrete strength after freeze-thawing cycles, calculated (%) as the average value of 3 test pieces;
f c0 -mean compressive strength (MPa) of the comparative test pieces;
f cn -average compressive strength (MPa) of 3 test pieces after N freeze-thaw cycles.
Δω n ＝(G 0 -G 1 )/G 0 ×100％
Δω n -mass loss rate after N freeze-thawing cycles, calculating (%) as an average of 3 test pieces;
g0—mass of test piece before freeze-thaw cycle test (G);
gn- -mass of test piece after N freeze-thaw cycles (g).
The data of the freeze-thaw resistance test of the concrete are shown in table 3:
table 3: anti-freeze thawing performance of concrete
F200 is a grade of concrete freeze resistance and represents that the mass loss of the concrete is not more than 5%, the dynamic elastic modulus is not more than 40% or the strength is not more than 25% after 200 freeze-thawing cycles. The multi-effect concrete water reducer prepared by the invention can be applied to concrete, so that the freeze-thawing resistance of the concrete can be obviously improved, the durability of the concrete can be improved, and the environment-friendly development requirement can be met.
Test example 4
The test is carried out by referring to a limited expansion rate test method specified in annex A in GB 23439-2017 'concrete expansion agent'; the test results are shown in Table 4.
Test materials and amounts:
| material | Material quality |
| 42.5 grade Portland cement | 607.5±2.0g |
| Water reducing Agents of example 3 or example 4 | 10.0+0.1g |
| Standard sand | 1350.0±5.0g |
| Mixing water | 190.0+1.0g |
Table 4 expansion performance test of concrete
| Limited expansion 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 from the multi-effect concrete water reducer prepared from example 4 added with sodium hexametaphosphate is better than that of the multi-effect concrete water reducer prepared from example 3 without sodium hexametaphosphate. The reasons 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 macroscopic expansion of the concrete.
Claims (4)
1. The multi-effect concrete water reducer is characterized by comprising the following components in parts by weight: 20-50 parts of polycarboxylate water reducer mother liquor, 1-2 parts of retarder, 2-8 parts of sugar calcium, 0.2-0.5 part of defoamer, 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 retarder is modified carrageenan; the preparation method of the modified carrageenan comprises the following steps:
1) Drying carrageenan powder in a drying oven at 30-40deg.C for 20-24 hr, pulverizing, and sieving with 80-120 mesh sieve to obtain pulverized carrageenan powder;
2) Weighing 10-15g of the crushed carrageenan powder prepared in the step 1), and uniformly dispersing the carrageenan powder in 100-150mL of ethanol aqueous solution with the mass concentration of 70-95 wt%; adding 4-6mL of 10-20wt% sodium hydroxide aqueous solution to the dispersion; heating the reaction solution to 30-40 ℃; after reacting for 1-2h, adding 4-6g sodium chloroacetate, and continuing to react for 3-4h at 30-40 ℃; cooling to 20-25deg.C, adjusting pH to 6.0-7.0 with 0.5-1mol/L acetic acid aqueous solution, vacuum filtering, collecting filter cake, and washing the filter cake with 70-95wt% ethanol aqueous solution for 2-3 times; placing the filter cake in a constant temperature drying oven at 30-40 ℃ for drying for 20-24 hours to obtain modified carrageenan;
the water-retaining agent is modified sodium carboxymethyl cellulose;
the preparation method of the modified sodium carboxymethyl cellulose comprises the following steps:
10-20g of sodium carboxymethyl cellulose is weighed and dissolved in 300-500mL of water, the solution is heated to 75-90 ℃, after nitrogen is introduced for 5-10min, 3-5g of 30-50wt% of potassium persulfate aqueous solution is dripped, after nitrogen is continuously introduced for 30-40min, 3-5g of 30-50wt% of potassium persulfate aqueous solution is dripped, after the dripping of the potassium persulfate aqueous solution is finished, the reaction is carried out for 10-30min while keeping the temperature, 5-10g of sodium p-styrenesulfonate is added, after the reaction is carried out for 0.5-1h, 3-5g of 30-50wt% of potassium persulfate aqueous solution is dripped, after the dripping of the potassium persulfate aqueous solution is finished, 8-10g of methyl methacrylate is dripped, after the dripping is finished, stirring is carried out at constant temperature for 3-5h, white latex is obtained, 100-200mL of 70-90wt% of ethanol aqueous solution is added into the white latex, the white latex is subjected to standing, precipitation is filtered, the precipitation is collected, the precipitation is washed by water, and then the obtained after the precipitation is dried in a vacuum drying oven for 20-24h, the crude cellulose is dried for 20-80 h, and the crude cellulose is obtained after the crude cellulose is dried for 20-20 h, and the crude cellulose is dried by the vacuum drying oven for 2-80 h.
2. A multi-effect concrete water reducing agent as defined in claim 1, wherein: the polycarboxylate water reducer mother liquor is one or a mixture of two or more of water-reducing polycarboxylate water reducer mother liquor, slump-retaining polycarboxylate water reducer mother liquor and viscosity-reducing polycarboxylate water reducer mother liquor.
3. A multi-effect concrete water reducing agent as defined in claim 1, wherein: the air entraining agent consists of sodium dodecyl benzene sulfonate and sodium dodecyl sulfate in the mass ratio of 1 to 2-3.
4. A multi-effect concrete water reducing agent as defined in claim 1, wherein: the defoaming agent is an organosilicon defoaming agent.
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