CN109987870B - High-efficiency concrete water reducing agent and preparation method thereof - Google Patents
High-efficiency concrete water reducing agent and preparation method thereof Download PDFInfo
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- CN109987870B CN109987870B CN201910313463.6A CN201910313463A CN109987870B CN 109987870 B CN109987870 B CN 109987870B CN 201910313463 A CN201910313463 A CN 201910313463A CN 109987870 B CN109987870 B CN 109987870B
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/0028—Aspects relating to the mixing step of the mortar preparation
- C04B40/0039—Premixtures of ingredients
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/04—Acids; Metal salts or ammonium salts thereof
- C08F220/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F228/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a bond to sulfur or by a heterocyclic ring containing sulfur
- C08F228/02—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a bond to sulfur or by a heterocyclic ring containing sulfur by a bond to sulfur
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
- C08F283/06—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G on to polyethers, polyoxymethylenes or polyacetals
- C08F283/065—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G on to polyethers, polyoxymethylenes or polyacetals on to unsaturated polyethers, polyoxymethylenes or polyacetals
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/30—Water reducers, plasticisers, air-entrainers, flow improvers
- C04B2103/302—Water reducers
Abstract
The invention discloses a high-efficiency concrete water reducing agent which is prepared from the following raw materials in parts by weight: 80-90 parts of polycarboxylic acid water reducing agent, 0.16-0.18 part of defoaming agent, 1-1.2 parts of viscosity regulator and 0.8-0.9 part of modified lignin; the invention also discloses a preparation method of the high-efficiency concrete water reducing agent. The invention takes a self-made polycarboxylate superplasticizer as a main substance, and the hydrophilic group carboxyl (-COO-), amino (-NH-) contained in the self-made polycarboxylate superplasticizer2) The synergistic effect of the hydrophobic group ester group (-COOR) and the polyether side chain is beneficial to the wetting and adsorption of the hydrophobic group ester group (-COOR) and the polyether side chain on the surfaces of concrete and concrete particles and the relative lubrication among aggregate particles; by quantitatively mixing the defoaming agent and the modified lignin, a proper amount of air can be introduced into the concrete, the workability of the concrete is improved, the viscosity of the concrete is reduced, and the concrete has certain slump retaining performance; the concrete water reducing agent which has high efficiency and strong slump retaining performance and can improve the workability of concrete is prepared.
Description
Technical Field
The invention belongs to the technical field of concrete processing, and particularly relates to a high-efficiency concrete water reducing agent and a preparation method thereof.
Background
The concrete water reducing agent is an additive for reducing the water required by the hardening of concrete and further improving the strength of the concrete, and the traditional concrete water reducing agent takes naphthalene and melamine products as the main stream. In recent years, with the vigorous development of construction industry at home and abroad, the demand of the water reducer for concrete is increased year by year, and the concrete develops towards high strength, light weight and construction fluidization, so that the water reducer is also required to have stronger dispersion and water reduction effects and better slump retaining performance. Because the traditional naphthalene and melamine water reducing agents have the problems of low water reducing rate, high slump loss of fresh concrete and the like, the construction requirements of increasingly complex and large-scale actual engineering are difficult to meet, the adaptability of the composite product and cement is unstable, the setting, hardening and durability of concrete are affected even, and the problems are more obvious along with the larger using amount of the water reducing agent in the building market, so that a novel high-efficiency water reducing agent is urgently needed.
At present, in developed countries abroad, such as the United states, Japan, Italy and the like, the water reducer is widely applied to maleic anhydride series and acrylic acid series high-performance concrete water reducers in concrete projects requiring high durability, such as water conservancy, roads and the like, although the technology is mature, the water reducer is restricted in the application and popularization of practical projects due to the problems of complex preparation process, high requirement on reaction equipment and the like. The research on novel carboxylic acid polymer water reducing agents is carried out after the concept about high-performance concrete is proposed in the field, and the novel carboxylic acid polymer water reducing agents are mainly used as concrete slump loss control agents from the research on reactive high-molecular maleic anhydride-olefin sulfonate copolymers.
Disclosure of Invention
The invention aims to provide a high-efficiency concrete water reducing agent and a preparation method thereof, wherein a self-made polycarboxylate water reducing agent is used as a main body substance, and the synergistic effect of hydrophilic group carboxyl (-COO-), amino (-NH2), hydrophobic group ester (-COOR) and polyether side chain contained in the self-made polycarboxylate water reducing agent is favorable for wetting and adsorbing the surfaces of concrete and concrete particles and relatively lubricating the aggregate particles; by doping the defoaming agent, the air content of the concrete mixture is reduced, the compactness of the concrete is increased, large bubbles which are unfavorable for strength are eliminated, and the compressive strength of the concrete can be improved; through the quantitative doping of the modified lignin, the modified lignin has a certain air entraining effect, can entrain air in a proper amount in concrete, improves the workability of the concrete, reduces the viscosity of the concrete and has a certain slump retaining performance on the concrete; the concrete water reducing agent which has high efficiency and strong slump retaining performance and can improve the workability of concrete is prepared.
The purpose of the invention can be realized by the following technical scheme:
the high-efficiency concrete water reducing agent is prepared from the following raw materials in parts by weight: 80-90 parts of polycarboxylic acid water reducing agent, 0.16-0.18 part of defoaming agent, 1-1.2 parts of viscosity regulator and 0.8-0.9 part of modified lignin;
the defoaming agent is a nonionic polyether defoaming agent;
the high-efficiency concrete water reducing agent is prepared by the following steps:
step S1, preparation of polycarboxylate superplasticizer
1) Adding diglycolamine, deionized water, concentrated sulfuric acid and sodium sulfate into a four-neck flask provided with a thermometer, a stirrer, a reflux condenser pipe and a heating device in sequence;
2) when the temperature reaches 90 ℃, adding maleic anhydride in batches in a small amount for 3 hours to react to obtain an active intermediate; wherein the mass ratio of maleic anhydride to diglycolamine is 1.1:1, the monomer concentration is 10%, the use amounts of concentrated sulfuric acid and sodium sulfate are respectively 1.2% and 1% of the mass of the monomer, and the concentrated sulfuric acid is 98% of sulfuric acid in mass fraction;
3) adding deionized water and isopentenyl polyoxyethylene ether into a glass reaction container provided with a water bath, a thermometer, a stirrer and a reflux condenser pipe, heating and stirring until solid raw materials are completely dissolved, adjusting the temperature to 60 ℃, sequentially and respectively dripping initiator ammonium persulfate, acrylic acid, sodium methallyl sulfonate and an active intermediate for copolymerization within 3h at the constant temperature of 60 ℃, and continuously preserving the heat for 50-60min after dripping;
wherein the addition amount of the deionized water is 11-12 times of the mass of the isopentenyl polyoxyethylene ether, the mass ratio of the isopentenyl polyoxyethylene ether, the acrylic acid, the sodium methallyl sulfonate and the active intermediate is 1.0:2.0:0.5:3.2, and the use amount of the ammonium persulfate is 1.1 percent of the mass of the monomer;
4) after the reaction is finished, adjusting the pH value to 6.9-7.2 by using a sodium hydroxide solution with the mass fraction of 30% to obtain a polycarboxylic acid water reducing agent;
and S2, mixing the defoamer, the viscosity regulator and the modified lignin into the polycarboxylic acid water reducer, and stirring and mixing uniformly to obtain the high-efficiency concrete water reducer.
Further, the viscosity modifier is prepared by the following method:
(1) dissolving sodium p-styrenesulfonate and diacetone acrylamide in a certain amount of deionized water to obtain a mixed solution, and adding a 28% NaOH solution to adjust the pH value of the mixed solution to 7.5-8;
(2) adding a certain amount of initiator into the mixed solution, putting into a constant-temperature water bath at 60 ℃, introducing nitrogen into the mixed solution for 30-35min, and reacting for 4h under the condition of slow stirring at 60 r/min;
(3) after the reaction is finished, adding deionized water to obtain the viscosity regulator;
wherein the concentration of the reaction monomer is 10%, and the mass ratio of the sodium styrene sulfonate to the diacetone acrylamide is 7: 3, the initiator is sodium persulfate, and the using amount of the initiator is 0.5 percent of the total mass of the monomers.
Further, the modified lignin is prepared by the following method:
(1) putting the rice straw lignin into a vacuum drying oven at 60 ℃ for drying for 16 hours for later use;
(2) weighing dried lignin, gradually dissolving the lignin into a sodium hydroxide solution with the mass fraction of 28% under strong stirring, slowly adding a methylglyoxal solution with the mass fraction of 20% at room temperature, wherein the dosage ratio of the methylglyoxal solution to the dried lignin is 5mL:3g, adjusting the pH value of the system to 11.8-12, reacting for 4h at 60 ℃, and cooling the product to the room temperature;
(3) precipitating lignin in the product by using 1 mol. L-1 hydrochloric acid solution, washing the product by using distilled water until the filtrate is neutral, and drying the product in a vacuum drying oven at the temperature of 60 ℃ for 22-24 hours to obtain the modified lignin.
The preparation method of the high-efficiency concrete water reducing agent comprises the following steps:
step S1, preparation of the polycarboxylate superplasticizer:
1) adding diglycolamine, deionized water, concentrated sulfuric acid and sodium sulfate into a four-neck flask provided with a thermometer, a stirrer, a reflux condenser pipe and a heating device in sequence;
2) when the temperature reaches 90 ℃, adding maleic anhydride in batches in a small amount for 3 hours to react to obtain an active intermediate; wherein the mass ratio of maleic anhydride to diglycolamine is 1.1:1, the monomer concentration is 10%, the use amounts of concentrated sulfuric acid and sodium sulfate are respectively 1.2% and 1% of the mass of the monomer, and the concentrated sulfuric acid is 98% of sulfuric acid in mass fraction;
3) adding deionized water and isopentenyl polyoxyethylene ether into a glass reaction container provided with a water bath, a thermometer, a stirrer and a reflux condenser pipe, heating and stirring until solid raw materials are completely dissolved, adjusting the temperature to 60 ℃, sequentially and respectively dripping initiator ammonium persulfate, acrylic acid, sodium methallyl sulfonate and an active intermediate for copolymerization within 3h at the constant temperature of 60 ℃, and continuously preserving the heat for 50-60min after dripping;
wherein the addition amount of the deionized water is 11-12 times of the mass of the isopentenyl polyoxyethylene ether, the mass ratio of the isopentenyl polyoxyethylene ether, the acrylic acid, the sodium methallyl sulfonate and the active intermediate is 1.0:2.0:0.5:3.2, and the use amount of the ammonium persulfate is 1.1 percent of the mass of the monomer;
4) after the reaction is finished, adjusting the pH value to 6.9-7.2 by using a sodium hydroxide solution with the mass fraction of 30% to obtain a polycarboxylic acid water reducing agent;
and S2, mixing the defoamer, the viscosity regulator and the modified lignin into the polycarboxylic acid water reducer, and stirring and mixing uniformly to obtain the high-efficiency concrete water reducer.
The invention has the beneficial effects that:
the concrete water reducing agent adopts a polycarboxylate water reducing agent as a main body, and the structural main chain of the prepared polycarboxylate water reducing agent contains hydrophilic group carboxyl (-COO-), amino (-NH2), hydrophobic group ester (-COOR) and polyether side chain; the carboxyl (-COO-) can generate good adsorption and anchoring effects on cement and soil, and effectively slow down the hydration of cement and the formation of calcium hydroxide crystals; the polyether side chain extends into the liquid phase, and reacts with water molecules to form a hydration film, and simultaneously exerts the steric hindrance effect to disperse cement particles; the ester group (-COOR) is hydrolyzed under the high alkaline environment of cement hydration and then converted into carboxyl group (-COO-) with strong hydrophilicity, so as to adsorb and disperse cement and soil particles; the short ether side chain and-NH 2 form hydrogen bonds with water molecules and polyether side chains respectively to play a role in strengthening steric hindrance; in addition, carboxyl (-COO-) can generate electrostatic adsorption with positively charged aluminate (C3A, C4 AF) in the cement mineral; the alkaline environment of cement hydration enables-NH 2 groups of the water reducing agent to be positively charged (-NH3+), and can react with negatively charged silicate (C3S and C2S) of cement minerals, and the synergistic effect of the groups on the polycarboxylate water reducing agent is beneficial to the wetting and adsorption of the polycarboxylate water reducing agent on the surfaces of concrete and concrete particles and the relative lubrication of aggregate particles;
according to the invention, the quantitative defoaming agent is doped in the concrete water reducing agent, the working performance of the concrete mixture has a certain relation with the gas content, and a proper amount of bubbles is beneficial to improving the workability of the concrete mixture, but the gas content is too high, so that the fluidity of the concrete is reduced, and after the defoaming agent is doped, a part of small bubbles beneficial to the working performance are still remained while large bubbles unfavorable to the working performance in the mixture are eliminated, so that the fluidity of the mixture is increased, and the loss of the fluidity for 3h is reduced; in the aspect of mechanical property, due to the addition of the defoaming agent, the gas content of the concrete mixture is reduced, the compactness of the concrete is increased, large bubbles which are unfavorable for strength are eliminated, and the compressive strength of the concrete can be improved;
according to the invention, modified lignin is doped into the concrete water reducing agent, the lignin is modified by methylglyoxal, methylglyoxal contains carbonyl and aldehyde groups, the aldehyde groups can be subjected to hydroxylation reaction with the lignin under an alkaline condition, so that the hydroxyl content in the lignin is increased, the total hydroxyl content of the lignin after modification is obviously improved compared with that before modification, the reaction activity is enhanced, and the thermal stability is obviously improved; when the modified lignin is added into concrete, the modified lignin has a very strong inhibiting effect on cement hydration due to residual saccharides and rich groups such as hydroxyl, ether bond, sulfonic acid group and the like contained in the modified lignin, and can play a role in retarding coagulation; meanwhile, the modified lignin can effectively shield the initial hydration of minerals, and is adsorbed on the surfaces of particles to form water films, so that the hydration products are prevented from adsorbing high-efficiency water reducing agent molecules, the molecular concentration of the high-efficiency water reducing agent in a liquid phase is effectively increased, and the sensitivity of the polycarboxylic acid water reducing agent in the application of concrete is improved, so that the retentivity of the fluidity is improved, namely the concrete has better slump retaining performance; moreover, the modified lignin has a certain air entraining effect, can entrain air in a proper amount in concrete, improves the workability of the concrete, reduces the viscosity of the concrete, and has a certain slump retaining performance on the concrete;
the self-made polycarboxylate superplasticizer is used as a main body substance, and the synergistic effect of hydrophilic group carboxyl (-COO-), amino (-NH2), hydrophobic group ester (-COOR) and polyether side chain contained in the self-made polycarboxylate superplasticizer is favorable for wetting and adsorbing the surfaces of concrete and concrete particles and relatively lubricating aggregate particles; by doping the defoaming agent, the air content of the concrete mixture is reduced, the compactness of the concrete is increased, large bubbles which are unfavorable for strength are eliminated, and the compressive strength of the concrete can be improved; through the quantitative doping of the modified lignin, the modified lignin has a certain air entraining effect, can entrain air in a proper amount in concrete, improves the workability of the concrete, reduces the viscosity of the concrete and has a certain slump retaining performance on the concrete; the concrete water reducing agent which is high in efficiency, strong in slump retaining performance and capable of improving the workability of concrete is prepared, can be widely applied to the field of buildings, and has remarkable social and economic benefits.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The high-efficiency concrete water reducing agent is prepared from the following raw materials in parts by weight: 80-90 parts of polycarboxylic acid water reducing agent, 0.16-0.18 part of defoaming agent, 1-1.2 parts of viscosity regulator and 0.8-0.9 part of modified lignin;
the defoaming agent is a nonionic polyether defoaming agent;
the workability of the concrete mixture has a certain relation with the air content, and the moderate amount of air bubbles is beneficial to improving the workability of the concrete mixture, but the air content is too high, so that the fluidity of the concrete is reduced, and after the defoaming agent is doped, part of small air bubbles beneficial to the workability are still remained while large air bubbles unfavorable to the workability in the mixture are eliminated, so that the fluidity of the mixture is increased, and the loss of the fluidity for 3h is reduced; in the aspect of mechanical property, due to the addition of the defoaming agent, the gas content of the concrete mixture is reduced, the compactness of the concrete is increased, large bubbles which are unfavorable for strength are eliminated, and the compressive strength of the concrete can be improved;
the viscosity regulator is prepared by the following method:
(1) dissolving sodium p-styrenesulfonate and diacetone acrylamide in a certain amount of deionized water to obtain a mixed solution, and adding a 28% NaOH solution to adjust the pH value of the mixed solution to 7.5-8;
(2) adding a certain amount of initiator into the mixed solution, putting into a constant-temperature water bath at 60 ℃, introducing nitrogen into the mixed solution for 30-35min, and reacting for 4h under the condition of slow stirring at 60 r/min;
(3) after the reaction is finished, adding deionized water to obtain the viscosity regulator;
wherein the concentration of the reaction monomer is 10%, and the mass ratio of the sodium p-styrene sulfonate to the diacetone acrylamide is 7: 3, the initiator is sodium persulfate, and the using amount of the initiator is 0.5 percent of the total mass of the monomers;
the prepared viscosity modifier is a copolymer of sodium p-styrenesulfonate and diacetone acrylamide, has a rich branched structure and excellent adsorption performance, achieves the viscosity reduction effect by air entraining compared with the common viscosity modifier, increases the adsorption thickness of the viscosity modifier on the surface of cement particles through a multi-branched structure of molecules, reduces the yield stress, and can reduce the viscosity of a mixture without increasing the gas content;
the modified lignin is prepared by the following method:
(1) putting the rice straw lignin into a vacuum drying oven at 60 ℃ for drying for 16 hours for later use;
(2) weighing dried lignin, gradually dissolving the lignin into a sodium hydroxide solution with the mass fraction of 28% under strong stirring, slowly adding a methylglyoxal solution with the mass fraction of 20% at room temperature, wherein the dosage ratio of the methylglyoxal solution to the dried lignin is 5mL:3g, adjusting the pH value of the system to 11.8-12, reacting for 4h at 60 ℃, and cooling the product to the room temperature;
(3) precipitating lignin in the product by using 1 mol. L-1 hydrochloric acid solution, washing the product by using distilled water until the filtrate is neutral, and drying the product in a vacuum drying oven at the temperature of 60 ℃ for 22-24 hours to obtain modified lignin;
the methylglyoxal modified lignin contains carbonyl and aldehyde groups, the aldehyde groups can be subjected to hydroxylation reaction with lignin under an alkaline condition, so that the hydroxyl content in the lignin is increased, the total hydroxyl content of the modified lignin is obviously improved compared with that before modification, the reaction activity is enhanced, and the thermal stability is obviously improved; when the modified lignin is added into concrete, the modified lignin has a very strong inhibiting effect on cement hydration due to residual saccharides and rich groups such as hydroxyl, ether bond, sulfonic acid group and the like contained in the modified lignin, and can play a role in retarding coagulation; meanwhile, the modified lignin can effectively shield the initial hydration of minerals, and is adsorbed on the surfaces of particles to form water films, so that the hydration products are prevented from adsorbing high-efficiency water reducing agent molecules, the molecular concentration of the high-efficiency water reducing agent in a liquid phase is effectively increased, and the sensitivity of the polycarboxylic acid water reducing agent in the application of concrete is improved, so that the retentivity of the fluidity is improved, namely the concrete has better slump retaining performance; moreover, the modified lignin has a certain air entraining effect, can entrain air in a proper amount in concrete, improves the workability of the concrete, reduces the viscosity of the concrete, and has a certain slump retaining performance on the concrete;
the preparation method of the high-efficiency concrete water reducing agent comprises the following steps:
step S1, preparation of the polycarboxylate superplasticizer:
adding diglycolamine, deionized water, concentrated sulfuric acid and sodium sulfate into a four-neck flask provided with a thermometer, a stirrer, a reflux condenser pipe and a heating device in sequence;
when the temperature reaches 90 ℃, adding maleic anhydride in batches in a small amount for 3 hours to react to obtain an active intermediate; wherein n (maleic anhydride) =1.1:1, the monomer concentration is 10%, the use amounts of concentrated sulfuric acid and sodium sulfate are respectively 1.2% and 1% of the monomer mass, and the concentrated sulfuric acid is 98% sulfuric acid in mass fraction; (the reactive intermediate introduces ester group and amino group in the process of aqueous solution free radical polymerization)
Adding deionized water and isopentenyl polyoxyethylene ether into a glass reaction container provided with a water bath, a thermometer, a stirrer and a reflux condenser pipe, heating and stirring until solid raw materials are completely dissolved, adjusting the temperature to 60 ℃, sequentially and respectively dripping initiator ammonium persulfate, acrylic acid, sodium methallyl sulfonate and an active intermediate for copolymerization within 3h at the constant temperature of 60 ℃, and continuously preserving the heat for 50-60min after dripping; wherein the addition amount of the deionized water is 11-12 times of the mass of the isopentenyl polyoxyethylene ether, n (isopentenyl polyoxyethylene ether), n (acrylic acid), n (sodium methallyl sulfonate), n (active intermediate) =1.0:2.0:0.5:3.2, and the use amount of ammonium persulfate is 1.1% of the mass of the monomer;
after the reaction is finished, adjusting the pH value to 6.9-7.2 by using a sodium hydroxide solution with the mass fraction of 30% to obtain a polycarboxylic acid water reducing agent;
the main chain of the structure of the prepared polycarboxylate superplasticizer contains hydrophilic group carboxyl (-COO-), amino (-NH2), hydrophobic group ester (-COOR) and polyether side chain; the carboxyl (-COO-) can generate good adsorption and anchoring effects on cement and soil, and effectively slow down the hydration of cement and the formation of calcium hydroxide crystals; the polyether side chain extends into the liquid phase, and reacts with water molecules to form a hydration film, and simultaneously exerts the steric hindrance effect to disperse cement particles; the ester group (-COOR) is hydrolyzed under the high alkaline environment of cement hydration and then converted into carboxyl group (-COO-) with strong hydrophilicity, so as to adsorb and disperse cement and soil particles; the short ether side chain and-NH 2 form hydrogen bonds with water molecules and polyether side chains respectively to play a role in strengthening steric hindrance; in addition, carboxyl (-COO-) can generate electrostatic adsorption with positively charged aluminate (C3A, C4 AF) in the cement mineral; the alkaline environment of cement hydration enables-NH 2 groups of the water reducing agent to be positively charged (-NH3+), and can react with negatively charged silicate (C3S and C2S) of cement minerals, and the synergistic effect of the groups on the polycarboxylate water reducing agent is beneficial to the wetting and adsorption of the polycarboxylate water reducing agent on the surfaces of concrete and concrete particles and the relative lubrication of aggregate particles;
and S2, mixing the defoamer, the viscosity regulator and the modified lignin into the polycarboxylic acid water reducer, and stirring and mixing uniformly to obtain the high-efficiency concrete water reducer.
When the high-efficiency concrete water reducing agent is used, the folding and solid content of the water reducing agent is 0.2%.
Example 1
The high-efficiency concrete water reducing agent is prepared from the following raw materials in parts by weight: 80 parts of polycarboxylic acid water reducing agent, 0.16 part of defoaming agent, 1 part of viscosity regulator and 0.8 part of modified lignin;
the preparation method of the high-efficiency concrete water reducing agent comprises the following steps:
step S1, preparation of the polycarboxylate superplasticizer:
1) adding diglycolamine, deionized water, concentrated sulfuric acid and sodium sulfate into a four-neck flask provided with a thermometer, a stirrer, a reflux condenser pipe and a heating device in sequence;
2) when the temperature reaches 90 ℃, adding maleic anhydride in batches in a small amount for 3 hours to react to obtain an active intermediate; wherein n (maleic anhydride) =1.1:1, the monomer concentration is 10%, the use amounts of concentrated sulfuric acid and sodium sulfate are respectively 1.2% and 1% of the monomer mass, and the concentrated sulfuric acid is 98% sulfuric acid in mass fraction;
3) adding deionized water and isopentenyl polyoxyethylene ether into a glass reaction container provided with a water bath, a thermometer, a stirrer and a reflux condenser pipe, heating and stirring until solid raw materials are completely dissolved, adjusting the temperature to 60 ℃, sequentially and respectively dripping initiator ammonium persulfate, acrylic acid, sodium methallyl sulfonate and an active intermediate within 3h at the constant temperature of 60 ℃ for copolymerization, and continuously preserving heat for 50min after dripping; wherein the addition amount of the deionized water is 11 times of the mass of the isopentenyl polyoxyethylene ether, n (isopentenyl polyoxyethylene ether), n (acrylic acid), n (sodium methallyl sulfonate), n (active intermediate) =1.0:2.0:0.5:3.2, and the use amount of ammonium persulfate is 1.1 percent of the mass of the monomer;
4) after the reaction is finished, adjusting the pH value to 6.9-7.2 by using a sodium hydroxide solution with the mass fraction of 30% to obtain a polycarboxylic acid water reducing agent;
and S2, mixing the defoamer, the viscosity regulator and the modified lignin into the polycarboxylic acid water reducer, and stirring and mixing uniformly to obtain the high-efficiency concrete water reducer.
Example 2
The high-efficiency concrete water reducing agent is prepared from the following raw materials in parts by weight: 85 parts of polycarboxylic acid water reducing agent, 0.17 part of defoaming agent, 1.1 parts of viscosity regulator and 0.85 part of modified lignin;
the preparation method of the high-efficiency concrete water reducing agent comprises the following steps:
step S1, preparation of the polycarboxylate superplasticizer:
1) adding diglycolamine, deionized water, concentrated sulfuric acid and sodium sulfate into a four-neck flask provided with a thermometer, a stirrer, a reflux condenser pipe and a heating device in sequence;
2) when the temperature reaches 90 ℃, adding maleic anhydride in batches in a small amount for 3 hours to react to obtain an active intermediate; wherein n (maleic anhydride) =1.1:1, the monomer concentration is 10%, the use amounts of concentrated sulfuric acid and sodium sulfate are respectively 1.2% and 1% of the monomer mass, and the concentrated sulfuric acid is 98% sulfuric acid in mass fraction;
3) adding deionized water and isopentenyl polyoxyethylene ether into a glass reaction container provided with a water bath, a thermometer, a stirrer and a reflux condenser pipe, heating and stirring until solid raw materials are completely dissolved, adjusting the temperature to 60 ℃, sequentially and respectively dripping initiator ammonium persulfate, acrylic acid, sodium methallyl sulfonate and an active intermediate within 3h at the constant temperature of 60 ℃ for copolymerization, and continuously preserving heat for 55min after dripping is finished; wherein the addition amount of the deionized water is 11.5 times of the mass of the isopentenyl polyoxyethylene ether, n (isopentenyl polyoxyethylene ether), n (acrylic acid), n (sodium methallyl sulfonate), n (active intermediate) =1.0:2.0:0.5:3.2, and the use amount of ammonium persulfate is 1.1 percent of the mass of the monomer;
4) after the reaction is finished, adjusting the pH value to 6.9-7.2 by using a sodium hydroxide solution with the mass fraction of 30% to obtain a polycarboxylic acid water reducing agent;
and S2, mixing the defoamer, the viscosity regulator and the modified lignin into the polycarboxylic acid water reducer, and stirring and mixing uniformly to obtain the high-efficiency concrete water reducer.
Example 3
The high-efficiency concrete water reducing agent is prepared from the following raw materials in parts by weight: 90 parts of polycarboxylic acid water reducing agent, 0.18 part of defoaming agent, 1.2 parts of viscosity regulator and 0.9 part of modified lignin;
the preparation method of the high-efficiency concrete water reducing agent comprises the following steps:
step S1, preparation of the polycarboxylate superplasticizer:
1) adding diglycolamine, deionized water, concentrated sulfuric acid and sodium sulfate into a four-neck flask provided with a thermometer, a stirrer, a reflux condenser pipe and a heating device in sequence;
2) when the temperature reaches 90 ℃, adding maleic anhydride in batches in a small amount for 3 hours to react to obtain an active intermediate; wherein n (maleic anhydride) =1.1:1, the monomer concentration is 10%, the use amounts of concentrated sulfuric acid and sodium sulfate are respectively 1.2% and 1% of the monomer mass, and the concentrated sulfuric acid is 98% sulfuric acid in mass fraction;
3) adding deionized water and isopentenyl polyoxyethylene ether into a glass reaction container provided with a water bath, a thermometer, a stirrer and a reflux condenser pipe, heating and stirring until solid raw materials are completely dissolved, adjusting the temperature to 60 ℃, sequentially and respectively dripping initiator ammonium persulfate, acrylic acid, sodium methallyl sulfonate and an active intermediate within 3h at the constant temperature of 60 ℃ for copolymerization, and continuously preserving the heat for 60min after dripping is finished; wherein the addition amount of the deionized water is 12 times of the mass of the isopentenyl polyoxyethylene ether, n (isopentenyl polyoxyethylene ether), n (acrylic acid), n (sodium methallyl sulfonate), n (active intermediate) =1.0:2.0:0.5:3.2, and the use amount of ammonium persulfate is 1.1 percent of the mass of the monomer;
4) after the reaction is finished, adjusting the pH value to 6.9-7.2 by using a sodium hydroxide solution with the mass fraction of 30% to obtain a polycarboxylic acid water reducing agent;
and S2, mixing the defoamer, the viscosity regulator and the modified lignin into the polycarboxylic acid water reducer, and stirring and mixing uniformly to obtain the high-efficiency concrete water reducer.
Comparative example
A commercial polycarboxylic acid water reducing agent was used as a comparative example.
And (3) performing performance measurement according to the concrete water reducer fracture-solid content of 0.2% in the examples 1-3 and the comparative example:
the working performance and the mechanical property of the concrete mixture are respectively carried out according to GB/T50080-2002 Standard for testing the performance of the common concrete mixture and GB/T50081-2002 Standard for testing the mechanical property of the common concrete, and the test results are shown in the following table:
it can be known that the water reducing agent prepared in the embodiment 1-3 is added into concrete, the initial fluidity of the water reducing agent is more than 593mm, and the fluidity loss after 3 hours is 15mm, which shows that the concrete water reducing agent prepared by the invention can increase the workability and fluidity of the concrete; the air content is less than 1.6 percent, the compressive strength after 7 days reaches 37.3-37.4MPa, the compressive strength after 28 days reaches 49.5-49.8MPa, and the collapse time is 3.8-3.9s, which shows that the water reducer prepared by the invention has strong collapse protection performance and compressive strength, and the obtained concrete has good mechanical properties.
The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims (2)
1. The high-efficiency concrete water reducing agent is characterized by being prepared from the following raw materials in parts by weight: 80-90 parts of polycarboxylic acid water reducing agent, 0.16-0.18 part of defoaming agent, 1-1.2 parts of viscosity regulator and 0.8-0.9 part of modified lignin;
the defoaming agent is a nonionic polyether defoaming agent;
the high-efficiency concrete water reducing agent is prepared by the following steps:
step S1, preparation of the polycarboxylate superplasticizer:
1) adding diglycolamine, deionized water, concentrated sulfuric acid and sodium sulfate into a four-neck flask provided with a thermometer, a stirrer, a reflux condenser pipe and a heating device in sequence;
2) when the temperature reaches 90 ℃, adding maleic anhydride in batches in a small amount for 3 hours to react to obtain an active intermediate; wherein the mass ratio of maleic anhydride to diglycolamine is 1.1:1, the monomer concentration is 10%, the use amounts of concentrated sulfuric acid and sodium sulfate are respectively 1.2% and 1% of the mass of the monomer, and the concentrated sulfuric acid is 98% of sulfuric acid in mass fraction;
3) adding deionized water and isopentenyl polyoxyethylene ether into a glass reaction container provided with a water bath, a thermometer, a stirrer and a reflux condenser pipe, heating and stirring until solid raw materials are completely dissolved, adjusting the temperature to 60 ℃, sequentially and respectively dripping initiator ammonium persulfate, acrylic acid, sodium methallyl sulfonate and an active intermediate for copolymerization within 3h at the constant temperature of 60 ℃, and continuously preserving the heat for 50-60min after dripping;
wherein the addition amount of the deionized water is 11-12 times of the mass of the isopentenyl polyoxyethylene ether, the mass ratio of the isopentenyl polyoxyethylene ether, the acrylic acid, the sodium methallyl sulfonate and the active intermediate is 1.0:2.0:0.5:3.2, and the use amount of the ammonium persulfate is 1.1 percent of the mass of the monomer;
4) after the reaction is finished, adjusting the pH value to 6.9-7.2 by using a sodium hydroxide solution with the mass fraction of 30% to obtain a polycarboxylic acid water reducing agent;
s2, mixing a defoaming agent, a viscosity regulator and modified lignin into the polycarboxylic acid water reducing agent, and uniformly stirring and mixing to obtain the high-efficiency concrete water reducing agent;
the modified lignin is prepared by the following method:
(1) putting the rice straw lignin into a vacuum drying oven at 60 ℃ for drying for 16 hours for later use;
(2) weighing dried lignin, gradually dissolving the lignin into a sodium hydroxide solution with the mass fraction of 28% under strong stirring, slowly adding a methylglyoxal solution with the mass fraction of 20% at room temperature, wherein the dosage ratio of the methylglyoxal solution to the dried lignin is 5mL:3g, adjusting the pH value of the system to 11.8-12, reacting for 4h at 60 ℃, and cooling the product to the room temperature;
(3) precipitating lignin in the product by using 1 mol. L-1 hydrochloric acid solution, washing the product by using distilled water until the filtrate is neutral, and drying the product in a vacuum drying oven at the temperature of 60 ℃ for 22-24 hours to obtain modified lignin;
the viscosity regulator is prepared by the following method:
(1) dissolving sodium p-styrenesulfonate and diacetone acrylamide in a certain amount of deionized water to obtain a mixed solution, and adding a 28% NaOH solution to adjust the pH value of the mixed solution to 7.5-8;
(2) adding a certain amount of initiator into the mixed solution, putting into a constant-temperature water bath at 60 ℃, introducing nitrogen into the mixed solution for 30-35min, and reacting for 4h under the condition of slow stirring at 60 r/min;
(3) after the reaction is finished, adding deionized water to obtain the viscosity regulator;
wherein the concentration of the reaction monomer is 10%, and the mass ratio of the sodium p-styrene sulfonate to the diacetone acrylamide is 7: 3, the initiator is sodium persulfate, and the using amount of the initiator is 0.5 percent of the total mass of the monomers.
2. The preparation method of the high-efficiency concrete water reducer according to claim 1, characterized by comprising the following steps:
1) adding diglycolamine, deionized water, concentrated sulfuric acid and sodium sulfate into a four-neck flask provided with a thermometer, a stirrer, a reflux condenser pipe and a heating device in sequence;
2) when the temperature reaches 90 ℃, adding maleic anhydride in batches in a small amount for 3 hours to react to obtain an active intermediate; wherein the mass ratio of maleic anhydride to diglycolamine is 1.1:1, the monomer concentration is 10%, the use amounts of concentrated sulfuric acid and sodium sulfate are respectively 1.2% and 1% of the mass of the monomer, and the concentrated sulfuric acid is 98% of sulfuric acid in mass fraction;
3) adding deionized water and isopentenyl polyoxyethylene ether into a glass reaction container provided with a water bath, a thermometer, a stirrer and a reflux condenser pipe, heating and stirring until solid raw materials are completely dissolved, adjusting the temperature to 60 ℃, sequentially and respectively dripping initiator ammonium persulfate, acrylic acid, sodium methallyl sulfonate and an active intermediate for copolymerization within 3h at the constant temperature of 60 ℃, and continuously preserving the heat for 50-60min after dripping;
wherein the addition amount of the deionized water is 11-12 times of the mass of the isopentenyl polyoxyethylene ether, the mass ratio of the isopentenyl polyoxyethylene ether, the acrylic acid, the sodium methallyl sulfonate and the active intermediate is 1.0:2.0:0.5:3.2, and the use amount of the ammonium persulfate is 1.1 percent of the mass of the monomer;
4) after the reaction is finished, adjusting the pH value to 6.9-7.2 by using a sodium hydroxide solution with the mass fraction of 30% to obtain a polycarboxylic acid water reducing agent;
and (3) adding a defoaming agent, a viscosity regulator and modified lignin into the polycarboxylic acid water reducing agent, and uniformly stirring and mixing to obtain the high-efficiency concrete water reducing agent.
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| CN111875281A (en) * | 2020-08-11 | 2020-11-03 | 衡阳市九州建材有限公司 | Powdery water reducing agent and preparation method thereof |
| CN112897933B (en) * | 2021-04-21 | 2021-11-30 | 深圳市天祥新材料有限公司 | Machine-made sand regulator for concrete |
| CN113683227A (en) * | 2021-09-14 | 2021-11-23 | 湖南天为环保科技有限公司 | Activating agent for strengthening high-concentration landfill leachate membrane concentrated solution solidified body and application thereof |
| CN114316157B (en) * | 2022-02-08 | 2023-10-31 | 淮北旭日新材料股份有限公司 | Environment-friendly water reducer |
| CN114477834A (en) * | 2022-03-04 | 2022-05-13 | 贵州万为金科特种建材有限公司 | Polycarboxylate high-efficiency water reducing agent |
| CN114890766A (en) * | 2022-06-10 | 2022-08-12 | 安徽瑞联节能科技股份有限公司 | Composite calcium silicate board and preparation method thereof |
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| CN115536304B (en) * | 2022-09-26 | 2023-06-16 | 浙江智峰科技有限公司 | Preparation process of compound concrete water reducer and concrete water reducer |
| CN115593048B (en) * | 2022-10-08 | 2023-11-21 | 北京化工大学 | Fireproof layer material, preparation method thereof and heat-insulating fireproof glass |
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