CN108558261B - Additive for inhibiting assembled concrete bleeding and preparation method thereof - Google Patents
Additive for inhibiting assembled concrete bleeding and preparation method thereof Download PDFInfo
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- CN108558261B CN108558261B CN201810448636.0A CN201810448636A CN108558261B CN 108558261 B CN108558261 B CN 108558261B CN 201810448636 A CN201810448636 A CN 201810448636A CN 108558261 B CN108558261 B CN 108558261B
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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
- 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 an additive for inhibiting water bleeding of fabricated concrete and a preparation method thereof. The concrete admixture is prepared from the following raw materials: 150-250 parts of polycarboxylic acid component, 5-20 parts of water secretion regulator and 730-845 parts of water. The invention also provides a preparation method of the concrete admixture, which comprises the following process steps: 1) adding the water secretion regulator into water, and stirring for a proper time until the water secretion regulator is dissolved to obtain a transparent solution; 2) adding a polycarboxylic acid component into the solution, and stirring for a proper time to obtain the concrete admixture. The concrete admixture prepared by the method can prevent the lagging bleeding of fresh concrete and ensure the appearance quality of the assembled concrete member; meanwhile, the admixture has high adaptability to cement, strong water-reducing dispersing capacity and wide application prospect.
Description
Technical Field
The invention belongs to the technical field of concrete admixtures, and particularly relates to an admixture for inhibiting fabricated concrete bleeding and a preparation method thereof.
Background
The development of the prefabricated buildings has become the national policy of the construction industry in China, and the state department issues a notice (the state issue [ 2016 ] 71) of guidance suggestions about the vigorous development of the prefabricated buildings. The opinion requires active development of fabricated concrete structures. The building department more specifically requires: by 2020, the proportion of national assembly type buildings in new buildings reaches more than 15%, more than 50 assembly type building demonstration cities, more than 200 assembly type building industry bases, more than 500 assembly type building demonstration projects and more than 30 assembly type building science and technology innovation bases are cultivated. At a policy level, the fabricated building has been raised to an unprecedented height.
However, the market share of the existing fabricated building is low, less than 1%, because the fabricated building is still subject to many technical difficulties in material production, structural design, construction acceptance and the like.
The prefabricated building uses building materials as designed building modules, wherein the prefabricated concrete structure is a main building module. The prefabricated concrete structure is a concrete structure formed by assembling/connecting prefabricated concrete members serving as main stressed members. The quality of the precast concrete member directly affects the quality of the fabricated concrete structure, and one important quality requires that the surface of the precast concrete member is flat and smooth, uniform in color and sharp in edges, which requires that the concrete mixture has good construction performance. The concrete mixture is the most critical control index because bleeding easily causes segregation and delamination of concrete, and the appearance quality of the concrete member is seriously influenced and the development of the precast concrete member is hindered due to many surface air holes, many water marks and large color difference.
Bleeding is the poor water retention of the constituent materials when the heavier solid components of the concrete components settle, causing some water to flow out of the concrete slurry. The concrete bleeding phenomenon can be divided into two types: normal bleeding and delayed bleeding. Ordinary bleeding generally occurs within a short time (5min) after the concrete mixture is mixed; the delayed bleeding means that the initial state of the fresh concrete is good, and the fresh concrete has good fluidity, cohesiveness and plasticity preservation, but within 1-2 hours (or a long time) after pouring construction, the concrete has obvious bleeding phenomenon, and the delayed bleeding often occurs during construction of the fresh concrete under the low-temperature condition in winter.
As an important guarantee for the quality of concrete, the concrete admixture can obviously improve the bleeding phenomenon of the concrete. Production of additives and a great deal of research is carried out by researchers to solve the bleeding problem of concrete. For example, patent CN107383274A discloses a concrete water retention agent prepared mainly from acrylamide, methacrylic acid and hydrophobic monomer (isobutyl methacrylate or dimethylaminoethyl methacrylate) by radical polymerization, and it is found from the publication that the water retention agent mainly solves the general bleeding phenomenon of concrete.
Compared with the common bleeding, the adverse effect caused by the delayed bleeding is larger, because the delayed bleeding phenomenon is difficult to find in time within 1h or longer after construction, and the delayed bleeding can cause floating slurry to appear on the surface layer of the concrete, and simultaneously, sand flow and water marks are formed on the side surface of the member, thereby seriously weakening the appearance quality of the surface of the concrete member.
Patent CN103992057B discloses a method for solving the problem of delayed bleeding of concrete, which is to compound a water-retaining material (one of polyvinyl alcohol, carboxymethyl cellulose, and methyl cellulose) and sodium sulfate into a polycarboxylic acid water reducing agent to inhibit the delayed bleeding of concrete, and it is found from the publication that the method focuses mainly on solving the delayed bleeding phenomenon after 1h of concrete mixture, and the bleeding condition after a long time of concrete mixture is not studied, and the bleeding phenomenon of fresh concrete before initial setting (generally 8-9h after mixing) will affect the appearance quality of concrete after demolition.
In order to solve the bleeding problem of concrete, particularly the phenomenon of delayed bleeding and ensure the appearance quality of a precast concrete member, the development of an additive for inhibiting the bleeding of the assembled concrete is very important.
Disclosure of Invention
The invention aims to provide an additive for inhibiting the bleeding of fabricated concrete, so as to prevent the occurrence of the delayed bleeding phenomenon of the concrete and ensure the appearance quality of fabricated concrete members.
Another object of the present invention is to provide a method for preparing the above additive for suppressing the bleeding of fabricated concrete.
Based on the research thought, the technical scheme of the invention is as follows:
an additive for inhibiting the bleeding of fabricated concrete is prepared from the following raw materials in parts by weight:
150-250 parts of polycarboxylic acid component, 5-20 parts of water secretion regulator and 730-845 parts of water;
the polycarboxylic acid component is prepared by free radical copolymerization of monomers such as allyl polyoxyethylene ether, acrylic acid, N- (3-dimethylaminopropyl) methacrylamide and the like; wherein the mass fraction ratio of the allyl polyoxyethylene ether, the acrylic acid, the N- (3-dimethylaminopropyl) methacrylamide, the initiator, the chain transfer agent and the water is 100: (3-10): (1-3): (0.1-0.5): (0.5-0.25): (120-180). The reaction temperature is 40-65 deg.C, preferably 45-60 deg.C.
Further, the mass concentration of the polycarboxylic acid component is preferably 35% to 50%, more preferably 35% to 45%; the mass fraction of the polycarboxylic acid component is preferably 150 to 250, and more preferably 150 to 200.
The water secretion regulator is one or more of zinc acetate dihydrate, zinc nitrate hexahydrate and zinc sulfate heptahydrate in any proportion.
Further, the water secretion regulator is preferably zinc acetate dihydrate, zinc nitrate hexahydrate and zinc sulfate heptahydrate, and is more preferably zinc nitrate hexahydrate and zinc sulfate heptahydrate; the water secretion regulator is preferably 5-20 parts by weight, and more preferably 5-10 parts by weight; the mass fraction of the water is preferably 730-845, and more preferably 800-845.
In addition, the preparation method of the fabricated concrete bleeding inhibiting additive comprises the following steps:
1) adding a proper amount of water secretion regulator into water, and stirring for a proper time until the water secretion regulator is dissolved to obtain a transparent solution; the stirring time is preferably 0.5-3 h; more preferably 0.5 to 1 hour.
2) Adding a proper amount of polycarboxylic acid component into the solution, and stirring for a proper time to obtain the concrete admixture; the stirring time is preferably 0.5 to 3 hours, and more preferably 0.5 to 1 hour.
Further, the preparation method of the polycarboxylic acid water-reducing component comprises the following steps:
1) dissolving allyl polyoxyethylene ether in water to prepare a solution A, wherein the mass concentration of the solution A is preferably 45-75%, and more preferably 55-70%; the molecular weight of the allyl polyoxyethylene ether is preferably 3000-5000, and more preferably 3500-4500;
2) dissolving acrylic acid and N- (3-dimethylaminopropyl) methacrylamide in water to prepare a solution B, wherein the mass concentration of the solution B is preferably 55-75%, and more preferably 60-70%;
3) dissolving a chain transfer agent and a reducing component in an initiator in water to prepare a solution C, wherein the mass concentration of the solution C is preferably 1.0-4.0%, and more preferably 1.5-2.5%; the chain transfer agent is preferably thioglycolic acid and mercaptopropionic acid; the initiator is a redox initiation system, preferably an L-ascorbic acid/hydrogen peroxide and sodium bisulfite/ammonium persulfate system, and the reducing components thereof are preferably L-ascorbic acid and hydrogen sulfite.
4) Heating the solution A to a set reaction temperature, adding an oxidizing component in an initiation system into the solution A, wherein the oxidizing component is preferably hydrogen peroxide and ammonium persulfate, then dropwise adding the solutions B and C into the solution A within different time, continuing to react for a period of time after all dropwise adding is finished, then cooling the reaction solution to room temperature, adjusting the pH value with alkali liquor, diluting with water to obtain a proper mass concentration, wherein the mass concentration is preferably 35-50%, more preferably 35-45%, and then obtaining the polycarboxylic acid component used by the invention.
Further, in the step 2), the dripping time of the solution B is preferably 2-4 h, and more preferably 3-4 h;
further, in the step 3), the dripping time of the solution C is preferably 2.5-5.5 hours, and more preferably 3-4.5 hours; after the dropwise addition, the continuous reaction time is preferably 0.5-2.0 h, and more preferably 0.5-1.5 h.
Further, in the step 4), the alkali liquor is preferably a sodium hydroxide solution, and the mass concentration of the alkali liquor is preferably 10-45%, and more preferably 25-35%; the pH value is preferably 4 to 7, more preferably 5.5 to 6.5.
Compared with the prior art, the invention has the following beneficial effects:
1) the concrete admixture prepared by the method can inhibit the bleeding of the fresh concrete, particularly the delayed bleeding at a lower environmental temperature, and can stop the delayed bleeding before the initial setting of the fresh concrete, thereby ensuring the appearance quality of the assembled concrete member.
2) The adaptability of the concrete admixture and cement is less influenced by the quality of the cement, and the delayed bleeding of concrete mixed by different cements can be prevented.
3) The concrete admixture prepared by the method has high cement dispersing capacity, can avoid delayed bleeding of fresh concrete, is low in mixing amount during use, high in adaptability and wide in application value.
Detailed Description
The additive for inhibiting the bleeding of the fabricated concrete is used for preventing the occurrence of the delayed bleeding phenomenon of the concrete and ensuring the appearance quality of the fabricated concrete member.
A large number of experimental studies show that the hydration rate of cement is influenced by the ambient temperature, and when the ambient temperature is lower, the hydration rate of cement is reduced, and the setting time is prolonged. Generally, polycarboxylic acid molecules added to fresh concrete are gradually consumed as they are wrapped by cement hydration products. However, when the ambient temperature is low, the hydration of the cement in the fresh concrete is slow, the amount of hydration products is low, and the retention time of the polycarboxylic acid molecules in the mixture is prolonged. As the polycarboxylic acid molecules continuously exert the dispersing capacity of the polycarboxylic acid molecules on cement, free water in the mixture is gradually separated out to form hysteresis bleeding.
Applicants have discovered that polycarboxylic acid molecules can be used to accelerate the rate of hydration of cement at lower temperatures by the synergistic effect of higher molecular weight polyether and amine groups. The polyether monomer and the amino monomer are further optimized, the generation rate of cement hydration products can be adjusted, the polycarboxylic acid molecules are ensured to be gradually wrapped by the hydration products to lose the water reducing and dispersing capacity, further, the precipitation of free water is inhibited, and the phenomenon of delayed bleeding is prevented.
The applicant researches and discovers that the poor adaptability of polycarboxylic acid molecules and cement can easily cause the phenomenon of delayed bleeding of fresh concrete. The quality of various cements is greatly different, such as the mineral phase proportion of clinker in the cement, the variety and quality difference of admixture in the cement, and the like, which increases the difficulty for the adaptability of polycarboxylic acid molecules with specific structures and the cement. In order to avoid lagging bleeding and weaken the influence of polycarboxylic acid molecules on the adaptability of cement, the invention develops the water bleeding regulator which has stronger complexing capacity on water and can adsorb free water released by the dispersing action of the polycarboxylic acid molecules.
Based on the research thought, the technical scheme of the invention is as follows:
an additive for inhibiting the bleeding of fabricated concrete has the technical scheme that the additive is prepared from the following raw materials in parts by weight: 150-250 parts of polycarboxylic acid component, 5-20 parts of water secretion regulator and 730-845 parts of water; the polycarboxylic acid component is prepared from monomers such as allyl polyoxyethylene ether, acrylic acid, N- (3-dimethylaminopropyl) methacrylamide and the like through free radical copolymerization, wherein the mass fraction ratio of the allyl polyoxyethylene ether, the acrylic acid, the N- (3-dimethylaminopropyl) methacrylamide, an initiator, a chain transfer agent and water is 100: (3-10): (1-3): (0.1-0.5): (0.5-0.25): (120-180); the water secretion regulator is one or the combination of zinc acetate dihydrate, zinc nitrate hexahydrate and zinc sulfate heptahydrate in any proportion.
For the sake of clarity, the present invention will be further described in detail by the following specific preferred embodiments in conjunction with the effect test examples, but the present invention is not limited to the following embodiments.
Example 1
The preparation method of the polycarboxylic acid water-reducing component comprises the following steps:
1) 160g of allyl polyoxyethylene ether with the molecular weight of 3500 is dissolved in 100g of water to prepare a solution A;
2) dissolving 13g of acrylic acid and 3.3g of N- (3-dimethylaminopropyl) methacrylamide in 8g of water to prepare a solution B;
3) dissolving 0.6g of mercaptopropionic acid and 0.3g of L-ascorbic acid in 45g of water to prepare a solution C;
4) heating the solution A to 50 ℃, adding 0.45g of hydrogen peroxide into the solution A, and then simultaneously dripping the solution B and the solution C into the solution A, wherein the dripping time of the solution B is 3.0h, and the dripping time of the solution C is 3.5 h;
after all the components are added dropwise, the reaction is continued for 1 hour, then the temperature of the reaction solution is cooled to room temperature, 20g of sodium hydroxide solution (30 wt%) is used for adjusting the pH value of the reaction solution to 6.0, and 109g of water is added to obtain the polycarboxylic acid component with the mass concentration of 40%.
The additive for inhibiting the bleeding of the fabricated concrete, which contains the polycarboxylic acid water-reducing component, is prepared from the following raw materials in parts by weight: 200 parts of polycarboxylic acid component, 5 parts of water secretion regulator zinc nitrate hexahydrate and 795 parts of water;
adding 5.0g of zinc nitrate hexahydrate into 795g of water, and stirring for 0.5h to obtain a transparent solution; and adding 200g of the prepared polycarboxylic acid component into the solution, and stirring for 0.5h to obtain the concrete admixture.
Example 2
The preparation method of the polycarboxylic acid water-reducing component comprises the following steps:
1) 182g of allyl polyoxyethylene ether with the molecular weight of 4000 is dissolved in 120g of water to prepare solution A;
2) dissolving 13g of acrylic acid and 3.3g of N- (3-dimethylaminopropyl) methacrylamide in 8g of water to prepare a solution B;
3) dissolving 0.6g of mercaptopropionic acid and 0.3g of L-ascorbic acid in 45g of water to prepare a solution C;
4) heating the solution A to 50 ℃, adding 0.45g of hydrogen peroxide into the solution A, and then simultaneously dripping the solution B and the solution C into the solution A, wherein the dripping time of the solution B is 3.0h, and the dripping time of the solution C is 3.5 h;
after all the dropwise addition is finished, the reaction is continued for 1 hour, then the temperature of the reaction solution is reduced to room temperature, the pH value of the reaction solution is adjusted to 6.0 by using 20g of sodium hydroxide solution (30 wt%), and then 122g of water is added to obtain the polycarboxylic acid component with the mass concentration of 40%.
The additive for inhibiting the bleeding of the fabricated concrete, which contains the polycarboxylic acid water-reducing component, is prepared from the following raw materials in parts by weight: 200 parts of polycarboxylic acid component, 10 parts of zinc sulfate heptahydrate as a water secretion regulator and 790 parts of water;
adding 10g of zinc sulfate heptahydrate into 790g of water, and stirring for 0.5h to obtain a transparent solution; and adding 200g of the prepared polycarboxylic acid component into the solution, and stirring for 0.5h to obtain the concrete admixture.
Example 3
The preparation method of the polycarboxylic acid water-reducing component comprises the following steps:
1) 182g of allyl polyoxyethylene ether with the molecular weight of 4000 is dissolved in 120g of water to prepare solution A;
2) dissolving 13g of acrylic acid and 5.0g of N- (3-dimethylaminopropyl) methacrylamide in 10g of water to prepare a solution B;
3) dissolving 0.6g of mercaptopropionic acid and 0.3g of L-ascorbic acid in 45g of water to prepare a solution C;
4) heating the solution A to 50 ℃, adding 0.45g of hydrogen peroxide into the solution A, and then simultaneously dripping the solution B and the solution C into the solution A, wherein the dripping time of the solution B is 3.0h, and the dripping time of the solution C is 3.5 h;
after all the dropwise addition is finished, the reaction is continued for 1 hour, then the temperature of the reaction solution is reduced to room temperature, the pH value of the reaction solution is adjusted to 6.0 by using 20g of sodium hydroxide solution (30 wt%), and then 122g of water is added to obtain the polycarboxylic acid component with the mass concentration of 40%.
The additive for inhibiting the bleeding of the fabricated concrete, which contains the polycarboxylic acid water-reducing component, is prepared from the following raw materials in parts by weight: 200 parts of polycarboxylic acid component, 10 parts of zinc sulfate heptahydrate as a water secretion regulator and 790 parts of water;
adding 10g of zinc sulfate heptahydrate into 790g of water, and stirring for 0.5h to obtain a transparent solution; and adding 200g of the prepared polycarboxylic acid component into the solution, and stirring for 0.5h to obtain the concrete admixture.
Example 4
The preparation method of the polycarboxylic acid water-reducing component comprises the following steps:
1) 182g of allyl polyoxyethylene ether with the molecular weight of 4000 is dissolved in 120g of water to prepare solution A;
2) dissolving 13g of acrylic acid and 3.3g of N- (3-dimethylaminopropyl) methacrylamide in 8g of water to prepare a solution B;
3) dissolving 0.6g of mercaptopropionic acid and 0.3g of L-ascorbic acid in 45g of water to prepare a solution C;
4) heating the solution A to 50 ℃, adding 0.45g of hydrogen peroxide into the solution A, and then simultaneously dripping the solution B and the solution C into the solution A, wherein the dripping time of the solution B is 3.0h, and the dripping time of the solution C is 3.5 h;
after all the dropwise addition is finished, the reaction is continued for 1 hour, then the temperature of the reaction solution is reduced to room temperature, the pH value of the reaction solution is adjusted to 6.0 by using 20g of sodium hydroxide solution (30 wt%), and then 122g of water is added to obtain the polycarboxylic acid component with the mass concentration of 40%.
The additive for inhibiting the bleeding of the fabricated concrete, which contains the polycarboxylic acid water-reducing component, is prepared from the following raw materials in parts by weight: 200 parts of polycarboxylic acid component, 15 parts of zinc sulfate heptahydrate as a water secretion regulator and 785 parts of water;
adding zinc sulfate heptahydrate (15g) into 785g of water, and stirring for 0.5h to obtain a transparent solution; and adding 200g of the prepared polycarboxylic acid component into the solution, and stirring for 0.5h to obtain the concrete admixture.
Example 5
The preparation method of the polycarboxylic acid water-reducing component comprises the following steps:
1) 182g of allyl polyoxyethylene ether with the molecular weight of 4000 is dissolved in 120g of water to prepare solution A;
2) dissolving 13g of acrylic acid and 3.3g of N- (3-dimethylaminopropyl) methacrylamide in 8g of water to prepare a solution B;
3) dissolving 0.6g of mercaptopropionic acid and 0.3g of L-ascorbic acid in 45g of water to prepare a solution C;
4) heating the solution A to 50 ℃, adding 0.45g of hydrogen peroxide into the solution A, and then simultaneously dripping the solution B and the solution C into the solution A, wherein the dripping time of the solution B is 3.0h, and the dripping time of the solution C is 3.5 h;
after all the dropwise addition is finished, the reaction is continued for 1 hour, then the temperature of the reaction solution is reduced to room temperature, the pH value of the reaction solution is adjusted to 6.0 by using 20g of sodium hydroxide solution (30 wt%), and then 122g of water is added to obtain the polycarboxylic acid component with the mass concentration of 40%.
The additive for inhibiting the bleeding of the fabricated concrete, which contains the polycarboxylic acid water-reducing component, is prepared from the following raw materials in parts by weight: 200 parts of polycarboxylic acid component, 20 parts of water secretion regulator zinc nitrate hexahydrate and 780 parts of water;
adding 20g of zinc nitrate hexahydrate into 780g of water, and stirring for 0.5h to obtain a transparent solution; and adding 200g of the prepared polycarboxylic acid component into the solution, and stirring for 0.5h to obtain the concrete admixture.
Comparative example 1
Dissolving allyl polyoxyethylene ether (109g) with the molecular weight of 2400 in 72g of water to prepare a solution (A);
dissolving acrylic acid (13g) in 10g of water to prepare a solution (B); mercaptopropionic acid (0.6g) and L-ascorbic acid (0.3g) were dissolved in 45g of water to prepare a solution (C);
heating the solution (A) to 50 ℃, adding hydrogen peroxide (0.45g) into the solution (A), and then simultaneously dripping the solutions (B) and (C) into the solution (A), wherein the dripping time of the solution (B) is 3.0h, and the dripping time of the solution (C) is 3.5 h;
after all the dropwise addition is finished, the reaction is continued for 1 hour, then the temperature of the reaction solution is reduced to room temperature, the pH value of the reaction solution is adjusted to 6.0 by using 20g of sodium hydroxide solution (30 wt%), and then 53g of water is added to obtain the polycarboxylic acid component with the mass concentration of 40%.
The prepared polycarboxylic acid component (200g) was added to 800g of water, and stirred for 0.5h to obtain a transparent solution as a comparative example.
Comparative example 2
Dissolving allyl polyoxyethylene ether (109g) with the molecular weight of 2400 in 72g of water to prepare a solution (A);
dissolving acrylic acid (13g) in 10g of water to prepare a solution (B); mercaptopropionic acid (0.6g) and L-ascorbic acid (0.3g) were dissolved in 45g of water to prepare a solution (C); heating the solution (A) to 50 ℃, adding hydrogen peroxide (0.45g) into the solution (A), and then simultaneously dripping the solutions (B) and (C) into the solution (A), wherein the dripping time of the solution (B) is 3.0h, and the dripping time of the solution (C) is 3.5 h;
after all the dropwise addition is finished, the reaction is continued for 1 hour, then the temperature of the reaction solution is reduced to room temperature, the pH value of the reaction solution is adjusted to 6.0 by using 20g of sodium hydroxide solution (30 wt%), and then 53g of water is added to obtain the polycarboxylic acid component with the mass concentration of 40%.
Adding zinc sulfate heptahydrate (15g) into 785g of water, and stirring for 0.5h to obtain a transparent solution; then adding the prepared polycarboxylic acid component (200g) into the solution, and stirring for 0.5h to obtain the concrete admixture.
The contents of the effect test examples are as follows.
Examples of Effect test
According to the determination method of the bleeding rate ratio in the concrete admixture (GB 8076-2008), the total bleeding mass of fresh concrete prepared by using the concrete admixtures in the examples and the comparative examples at different times before the initial setting of the concrete was measured.
According to the requirement of a prefabricated ready-mixed concrete structure, the concrete comprises the following components in parts by weight:
360 parts of cement, 80 parts of fly ash, 720 parts of sand, 1060 parts of stones, 140 parts of water and 9.0 parts of concrete admixture. The cement is made of ordinary portland cement (PO 425R), and the manufacturers are conch (fresh) cement, Huarun (seal) cement, Tai mud, Guangdong hong Feng cement and Guangzhou Zhujiang cement; the fly ash is II-grade fly ash produced by Guangzhou Wanglong power plants.
Table 1 example 1 total bleeding mass of formulated concrete
Table 2 example 2 total bleeding mass of formulated concrete
Table 3 example 3 total bleeding mass of formulated concrete
Table 4 example 4 total bleeding mass of formulated concrete
Table 5 example 5 total bleeding mass of formulated concrete
Table 6 total bleeding mass of comparative example 1 formulated concrete
TABLE 7 Total bleeding mass of comparative example 2 formulated concrete
Note: the volume of the concrete in the test was about 5.0L, and the initial setting time was about 9.0 h.
As can be seen from the bleeding amount data of the fresh concrete prepared in the above tables 1 to 5 after different periods of time, the bleeding amounts of the concrete prepared with the concrete admixtures prepared in examples 1 to 5 at different periods of time were greatly reduced as compared with those of comparative examples 1 to 2.
Taking the Huarun cement as an example, when the cement is compared with the original cement in the comparative example 1, the total bleeding mass of the fresh concrete is 21.6g, and the bleeding phenomenon still occurs 3 hours after the concrete is mixed; the bleeding amount of the concrete prepared by the concrete admixture prepared by the method is greatly reduced, for example, in example 4, the total bleeding mass of the fresh concrete is only 1.5g, no bleeding occurs after the concrete is mixed for 2 hours, and the fresh concrete keeps good workability.
These data indicate that the concrete admixture prepared by the method of the present invention can inhibit the bleeding of concrete, especially the delayed bleeding phenomenon after 2 hours of mixing.
When different cements are adopted, the bleeding phenomenon of the fresh concrete is greatly different, compared with other cements, the bleeding phenomenon of the Hongfeng cement is the most serious, for example, when the cement is compared with the other cements, the total bleeding mass of the fresh concrete reaches 99.2g, and the bleeding phenomenon still occurs after 4h of mixing; in example 5, the bleeding amount was reduced to 8.6g, no bleeding occurred after 2 hours of mixing, and the fresh concrete maintained good plasticity. This shows that when the quality of cement fluctuates, the concrete admixture prepared by the method of the invention can still inhibit the bleeding of concrete, especially the delayed bleeding phenomenon after 2h of mixing.
When the Hongfeng cement is adopted, compared with the comparative example 1, the comparative example 2 has the advantages that the total bleeding mass of the fresh concrete reaches 60.2g, the bleeding amount is obviously reduced, and the bleeding amount in different time periods is also obviously reduced. The water bleeding regulator can improve the adaptability of concrete admixture and cement and enhance the capability of fresh concrete in inhibiting water bleeding.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, so that any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.
Claims (10)
1. The additive for inhibiting the bleeding of the fabricated concrete is characterized by being prepared from the following raw materials in parts by weight:
150-250 parts of polycarboxylic acid component, 5-20 parts of water secretion regulator and 730-845 parts of water; the polycarboxylic acid component is prepared by the free radical copolymerization of allyl polyoxyethylene ether, acrylic acid and N- (3-dimethylaminopropyl) methacrylamide monomer; wherein, the ratio of allyl polyoxyethylene ether, acrylic acid, N- (3-dimethylamino propyl) methacrylamide, initiator, chain transfer agent and water is 100: (3-10): (1-3): (0.1-0.5): (0.5-0.25): (120-180) by mass; the reaction temperature is 40-65 ℃;
the water secretion regulator is one or more of zinc acetate dihydrate, zinc nitrate hexahydrate and zinc sulfate heptahydrate in any proportion;
the preparation method comprises the following process steps:
1) adding the water secretion regulator into water, and stirring for a proper time until the water secretion regulator is dissolved to obtain a transparent solution;
2) adding a polycarboxylic acid component into the solution, and stirring for a proper time to obtain the concrete admixture.
2. The bleeding-inhibiting admixture for fabricated concrete according to claim 1, wherein: the reaction temperature is 45-60 ℃.
3. The bleeding-inhibiting admixture for fabricated concrete according to claim 1, wherein: the preparation method of the polycarboxylic acid water-reducing component comprises the following steps:
1) dissolving allyl polyoxyethylene ether in water to prepare a solution A, wherein the mass concentration of the solution A is 45-75%;
2) dissolving acrylic acid and N- (3-dimethylaminopropyl) methacrylamide in water to prepare a solution B, wherein the mass concentration of the solution B is 55-75%;
3) dissolving reducing components in a chain transfer agent and an initiator in water to prepare a solution C with the mass concentration of 1.0-4.0%;
4) heating the solution A to a set reaction temperature, adding an oxidizing component in an initiation system into the solution A, wherein the oxidizing component comprises hydrogen peroxide and ammonium persulfate, then dropwise adding the solutions B and C into the solution A within different time, continuing to react for a period of time after all dropwise adding is finished, then cooling the temperature of the reaction solution to room temperature, adjusting the pH value with alkali liquor, diluting with water to obtain a proper mass concentration, and thus obtaining the polycarboxylic acid component.
4. The bleeding-inhibiting admixture for fabricated concrete according to claim 3, wherein:
in the step 1), the mass concentration of the solution A is 55-70%;
in the step 2), the mass concentration of the solution B is 60-70%;
in the step 3), the mass concentration of the solution C is 1.5-2.5%.
5. The bleeding-inhibiting admixture for fabricated concrete according to claim 3, wherein:
in the step 1), the molecular weight of the allyl polyoxyethylene ether is 3000-5000;
in the step 3), the chain transfer agent is thioglycolic acid or mercaptopropionic acid; the initiator is a redox initiation system, and is an L-ascorbic acid/hydrogen peroxide and sodium bisulfite/ammonium persulfate system, and the reducing components of the initiator are respectively L-ascorbic acid and sodium bisulfite;
in the step 4), the dripping time of the solution B is 2-4 h; the dropping time of the solution C is 2.5-5.5 h; after the dropwise addition is finished, continuing the reaction for 0.5-2.0 h; the alkali liquor is sodium hydroxide solution, and the mass concentration of the alkali liquor is 10-45%; the pH value is 4-7.
6. The bleeding-inhibiting admixture for fabricated concrete according to claim 5, wherein:
in the step 1), the molecular weight of the allyl polyoxyethylene ether is 3500-4500;
in the step 4), the dripping time of the solution B is 3-4 h; the dropping time of the solution C is 3-4.5 h; after the dropwise addition is finished, continuing the reaction for 0.5-1.5 h; the alkali liquor is sodium hydroxide solution, and the mass concentration of the alkali liquor is 25-35%; the pH value is 5.5-6.5.
7. The bleeding-inhibiting admixture for fabricated concrete according to claim 1, wherein: the mass concentration of the polycarboxylic acid component is 35-50%.
8. The bleeding-inhibiting admixture for fabricated concrete according to claim 7, wherein: the mass concentration of the polycarboxylic acid component is 35-45%.
9. The bleeding-inhibiting admixture for fabricated concrete according to claim 1, wherein:
in the step 1), the stirring time is 0.5-3 h;
in the step 2), the stirring time is 0.5-3 h.
10. The bleeding-inhibiting admixture for fabricated concrete according to claim 1, wherein: in the step 1), the stirring time is 0.5-1 h; in the step 2), the stirring time is 0.5-1 h.
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