CN109160766B - Core-shell structure expanding agent for concrete and preparation method thereof - Google Patents
Core-shell structure expanding agent for concrete and preparation method thereof Download PDFInfo
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- CN109160766B CN109160766B CN201811178726.9A CN201811178726A CN109160766B CN 109160766 B CN109160766 B CN 109160766B CN 201811178726 A CN201811178726 A CN 201811178726A CN 109160766 B CN109160766 B CN 109160766B
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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
- C04B40/0046—Premixtures of ingredients characterised by their processing, e.g. sequence of mixing the ingredients when preparing the premixtures
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Abstract
The invention relates to a core-shell structure expanding agent for concrete, which comprises 55-76% of calcium oxide, 7-12% of high polymer, 1-5% of azodiisobutyronitrile, 3-6% of 3-aminopropylmethyldiethoxysilane, 2-4% of sodium hexametaphosphate, 2-4% of sodium silicate and 9-14% of ferric chloride. In the preparation method of the expanding agent, calcium oxide is added with an anhydrous dichloromethane solution of high molecular polymer and an ethanol solution of 3-aminopropyl methyl diethoxy silane in sequence; then adding azodiisobutyronitrile to complete surface grafting modification; and finally, adding a sodium hexametaphosphate solution, a sodium silicate solution and an iron chloride solution, and baking by a muffle furnace to obtain a finished product of the core-shell structure expanding agent. The particle size of the expanding agent is uniform, the iron oxide shell can prevent the calcium oxide expanding agent from being hydrated too fast in the early stage, and the iron oxide reacts with alkali liquor in concrete to generate ferric hydroxide, so that a secondary expansion source is provided, and the problem of effective compensation shrinkage is solved; the compactness of the concrete is increased, and the compressive strength and the impermeability of the concrete are improved.
Description
Technical Field
The invention relates to the technical field of concrete admixtures, in particular to a core-shell structure expanding agent for concrete and a preparation method thereof.
Background
Calcium oxide (CaO) is an important inorganic expanding agent material, and is mainly used for concrete to react with water to generate calcium hydroxide with low solubility under the condition of low water demand, and simultaneously generate large expansion energy to compensate early concrete shrinkage, thereby reducing the probability of crack generation. The calcium oxide reacts very violently with water, very high reaction heat can be instantaneously released when the calcium oxide is contacted with the water, the heat release amount is large, so that the temperature rise inside the concrete is relatively high, but the heat dissipation inside the concrete is slow, and the surface cooling speed is high, so that the temperature stress is generated, and the temperature crack is generated.
In order to solve the problem that the reaction degree of calcium oxide (CaO) and water is quite violent and reduce the generation of ineffective expansion energy, the surface of calcium oxide is mostly coated in the prior art, so that the phenomenon of violent heat release caused by direct contact of the calcium oxide and water is avoided, and the reaction time with the water is prolonged. For example, patent No. 201510060677.9 discloses a modified calcium oxide expanding agent for cement concrete, which is coated with long-chain fatty acid on the surface of the expanding agent, but simply solves the problem of rapid reaction of calcium oxide, but the expanding agent lacks a secondary expansion source, and is not ideal for sufficiently improving the crack resistance of concrete. For example, patent No. 201510061056.2 discloses a modified calcium oxide cement concrete expanding agent and a preparation method thereof, wherein the expanding agent is coated on the surface of calcium oxide by degradable high molecular polymers such as polyester, polycarbonate or polyester carbonate, and similarly lacks a secondary expansion source.
Disclosure of Invention
The invention provides a core-shell structure expanding agent for concrete, which is realized by the following technology in order to ensure that a secondary expansion source is provided after the calcium oxide surface is coated.
A core-shell structure expanding agent for concrete comprises the following components in percentage by mass: 55-76% of calcium oxide, 7-12% of high polymer, 1-5% of azodiisobutyronitrile, 3-6% of 3-aminopropylmethyldiethoxysilane, 2-4% of sodium hexametaphosphate, 2-4% of sodium silicate and 9-14% of ferric chloride; wherein the high molecular polymer is biodegradable.
In the core-shell structure expanding agent for concrete, the sodium hexametaphosphate solution and the sodium silicate solution are used as a compounded dispersing agent, so that the dissolution of ferric chloride can be promoted, and the generated ferric hydroxide can be uniformly adsorbed on the surface of calcium oxide subjected to surface grafting treatment. After roasting in a muffle furnace, the ferric hydroxide on the surface reacts to generate ferric oxide, so that the iron oxide is more stably attached. The expanding agent with the core-shell structure is oxidized, so that on one hand, the problem that the CaO expanding agent is too fast hydrated in the early stage is effectively relieved, and the phenomenon that the hydrated expansion cannot effectively compensate shrinkage in the concrete plasticity stage is avoided; on the other hand, when the concrete expanding agent is used, the ferric oxide reacts with alkaline liquid in the concrete again to generate ferric hydroxide to cause volume expansion, so that a secondary expansion source is provided for the concrete, the compactness of the concrete can be increased, and the compressive strength and the impermeability of the concrete can be improved.
Preferably, the biodegradable high molecular polymer comprises at least one of polyorthoester and polylactide-glycolide.
More preferably, the core-shell structure expanding agent for concrete comprises, by mass: 66% of calcium oxide, 8.5% of high polymer, 3% of azobisisobutyronitrile, 4.5% of 3-aminopropylmethyldiethoxysilane, 3.5% of sodium hexametaphosphate, 3.5% of sodium silicate and 11% of ferric chloride.
The invention also provides a preparation method of the core-shell structure expanding agent for concrete, which comprises the following steps:
s1, weighing calcium oxide, drying and grinding the calcium oxide into fine powder to ensure that the specific surface area is 200-600 m2Kg, sample A; weighing high molecular polymer, azodiisobutyronitrile, 3-aminopropyl methyl diethoxysilane, sodium hexametaphosphate, sodium silicate and ferric chloride for later use; preparing all high molecular polymers into 10g/L anhydrous dichloromethane solution, namely solution B; preparing all 3-aminopropyl methyl diethoxy silane into an ethanol solution with the concentration of 6g/L, namely a solution C; preparing 5% aqueous solution, namely solution D, E, from all sodium hexametaphosphate and sodium silicate respectively; preparing all ferric chloride into an aqueous solution with the mass fraction of 12%, namely a solution F;
s2, adding all the samples A into the solution B in equal amount and in batches, stirring uniformly, and removing a dichloromethane solvent at 60 ℃ in vacuum to obtain a calcium oxide expanding agent which is coated and modified on the surface of a high molecular polymer, namely P-CaO;
s3, adding all P-CaO into the solution C, and stirring for 1-3 h; then adding azodiisobutyronitrile, stirring for 2-4 h again, standing for 3-6 h, and drying the precipitate in a 60 ℃ oven to obtain a modified calcium oxide expanding agent subjected to surface grafting treatment, namely ADMS-P-CaO;
s4, preparing slurry with the concentration of 300g/L from all ADMS-P-CaO by absolute ethyl alcohol, and then adding the solution D, E and stirring uniformly; then adding the solution F, heating to boil, and reacting for 2-3 h; and finally, washing, neutralizing, drying and roasting in a muffle furnace to obtain the ADMS-P-CaO expanding agent finished product with the surface coated by the iron oxide.
In the preparation method of the core-shell structure expanding agent for concrete, the principle is as follows: the surface of calcium oxide is coated with biodegradable high molecular polymer to minimize the agglomeration of calcium oxide, make the particle size more uniform, and better disperse in organic solvent, then surface graft modification is carried out with 3-aminopropyl methyl diethoxy silane to improve the adhesion property of calcium oxide surface, and finally the surface is reacted with ferric chloride to realize the uniform coating of a layer of ferric oxide on the surface.
Preferably, in step S1, the specific surface area of the sample is 450m2/kg。
More preferably, in step S4, the heating method of the muffle furnace is: firstly, heating to 560-700 ℃ within 1-3 h, and preserving heat for 1-2.5 h; and finally, gradually cooling to room temperature within 2-4 h under the protection of nitrogen.
More preferably, in step S4, the muffle furnace is heated in the following manner: firstly, heating to 680 ℃ within 2h, and preserving heat for 2 h; finally, the temperature is gradually reduced to the room temperature within 3.5 hours under the protection of nitrogen. .
The invention also provides a preparation method of the core-shell structure expanding agent for concrete.
Compared with the prior art, the invention has the advantages that:
1. degradable high molecular materials are utilized to carry out film forming treatment on the surface of calcium oxide, so that the agglomeration effect of the calcium oxide is reduced, the particle size is more uniform, and the calcium oxide can be better dispersed in an organic solvent;
2. the ADMS-P-CaO is prepared by coating iron oxide as a shell, so that on one hand, the problem that the calcium oxide expanding agent is too fast to hydrate in the early stage is solved, and the problem that the hydrated expansion cannot effectively compensate shrinkage in the concrete plasticity stage is solved;
3. the ferric oxide reacts with alkali liquor in the concrete to generate ferric hydroxide, volume expansion is caused, and a secondary expansion source is provided;
4. the alkali liquor in the ferric oxide reacts to generate ferric hydroxide, so that the compactness of the concrete can be increased, and the compressive strength and the impermeability of the concrete can be improved.
Detailed Description
The technical solutions of the present invention will be described clearly and completely below, 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 core-shell structure expansive agent for concrete prepared in the following examples 1 to 9 and comparative examples 1 to 6 is prepared by the following method:
s1, weighing calcium oxide, drying, and grinding to make its specific surface area alpha m2Kg, sample A; weighing polylactide-glycolide, azodiisobutyronitrile, 3-aminopropylmethyldiethoxysilane, sodium hexametaphosphate, sodium silicate and ferric chloride for later use; preparing anhydrous dichloromethane solution with the concentration of 10g/L, namely solution B, from all polylactide-glycolide; preparing all 3-aminopropyl methyl diethoxy silane into an ethanol solution with the concentration of 6g/L, namely a solution C; preparing 5% aqueous solution, namely solution D, E, from all sodium hexametaphosphate and sodium silicate respectively; preparing all ferric chloride into an aqueous solution with the mass fraction of 12%, namely a solution F;
s2, adding all the samples A into the solution B in equal amount and in batches, stirring uniformly, and removing a dichloromethane solvent in vacuum at 60 ℃ to obtain a calcium oxide expanding agent which is modified by wrapping the surfaces of polylactide-glycolide, namely P-CaO;
s3, adding all P-CaO into the solution C, and stirring for 1-3 h; then adding azodiisobutyronitrile, stirring for 2-4 h again, standing for 3-6 h, and drying the precipitate in a 60 ℃ oven to obtain a modified calcium oxide expanding agent subjected to surface grafting treatment, namely ADMS-P-CaO;
s4, preparing slurry with the concentration of 300g/L from all ADMS-P-CaO by absolute ethyl alcohol, and then adding the solution D, E and stirring uniformly; then adding the solution F, heating to boil, and reacting for 2-3 h; finally, washing, neutralizing, drying, putting into a muffle furnace, heating to T ℃ within 1-3 h, and preserving heat for 2 h; and finally, gradually reducing the temperature to room temperature within 3.5 hours under the protection of nitrogen to obtain the ADMS-P-CaO expanding agent finished product with the surface coated by the ferric oxide. .
Examples 1 to 7 and comparative examples 1 to 6
In examples 1 to 7 and comparative examples 1 to 6, calcium oxide, polylactide-glycolide, azobisisobutyronitrile, 3-aminopropylmethyldiethoxysilane, sodium hexametaphosphate, sodium silicate, and iron chloride were weighed in the mass percentages in table 1. core-Shell Structure expanding agent of examples and comparative examples in preparation, specific surface area α m of sample A of step S12In terms of/kg, T.degree.C. in step S4 is shown in Table 1 below.
TABLE 1 core-shell structure expander formulations and preparation conditions for examples 1-7 and comparative examples 1-6
Application example
In the examples, ADMS-P-CaO prepared in step S3, i.e., ADMS-P-CaO expander coated with monosodium glutamate and iron oxide, was used as a control group. The performances of examples 1 to 7, comparative examples 1 to 6 and a control group, and the compression resistance, the fracture resistance and the expansion rate limiting performance of the concrete prepared by adopting the expanding agents are detected, and specific results are shown in tables 2 and 3 below.
TABLE 2 Performance tables of the core-shell expanders of examples 1 to 7 and comparative examples 1 to 6
TABLE 3 tables for testing the compression and bending resistances and the limited expansion rates of the concretes prepared in examples 1 to 7 and comparative examples 1 to 6
As can be seen from the above tables 2 and 3, the core-shell structure expansive agents prepared in examples 1 to 7 have the best performance, and the core-shell structure expansive agents prepared in examples 1 to 7 also have better mechanical properties than those of the control group and comparative examples 1 to 6. The core-shell structure expanding agent prepared in the example 1 has the best performance, and the concrete prepared correspondingly has the best mechanical property. Compared with the calcium oxide expanding agent only coated with degradable high molecular polymer on the surface, the expanding agent with the core-shell structure prepared by coating the calcium oxide particle surface with the high molecular polymer, the expanding agent has better performance, and the prepared concrete has better limited expansion rate, breaking strength and compressive strength.
Claims (7)
1. A core-shell structure expanding agent for concrete is characterized by comprising the following components in percentage by mass: 55-76% of calcium oxide, 7-12% of high polymer, 1-5% of azodiisobutyronitrile, 3-6% of 3-aminopropylmethyldiethoxysilane, 2-4% of sodium hexametaphosphate, 2-4% of sodium silicate and 9-14% of ferric chloride; wherein the high molecular polymer is biodegradable.
2. The core-shell structural expansive agent for concrete according to claim 1, wherein said biodegradable high molecular polymer comprises at least one of polyorthoester and polylactide-glycolide.
3. The core-shell structural expanding agent for concrete according to claim 2, comprising by mass: 66% of calcium oxide, 8.5% of high polymer, 3% of azobisisobutyronitrile, 4.5% of 3-aminopropylmethyldiethoxysilane, 3.5% of sodium hexametaphosphate, 3.5% of sodium silicate and 11% of ferric chloride.
4. A method for preparing a core-shell structure expansive agent for concrete as claimed in any one of claims 1 to 3, comprising the steps of:
s1, weighing calcium oxide, drying and grinding the calcium oxide into fine powder to ensure that the specific surface area is 200-600 m2Kg, sample A; weighing high molecular polymer, azodiisobutyronitrile, 3-aminopropyl methyl diethoxysilane, sodium hexametaphosphate, sodium silicate and ferric chloride for later use; preparing all high molecular polymers into 10g/L anhydrous dichloromethane solution, namely solution B; preparing all 3-aminopropyl methyl diethoxy silane into an ethanol solution with the concentration of 6g/L, namely a solution C; preparing 5% aqueous solution, namely solution D, E, from all sodium hexametaphosphate and sodium silicate respectively; preparing all ferric chloride into an aqueous solution with the mass fraction of 12%, namely a solution F;
s2, adding all the samples A into the solution B in equal amount and in batches, stirring uniformly, and removing a dichloromethane solvent at 60 ℃ in vacuum to obtain a calcium oxide expanding agent which is coated and modified on the surface of a high molecular polymer, namely P-CaO;
s3, adding all P-CaO into the solution C, and stirring for 1-3 h; then adding azodiisobutyronitrile, stirring for 2-4 h again, standing for 3-6 h, and drying the precipitate in a 60 ℃ oven to obtain a modified calcium oxide expanding agent subjected to surface grafting treatment, namely ADMS-P-CaO;
s4, preparing slurry with the concentration of 300g/L from all ADMS-P-CaO by absolute ethyl alcohol, and then adding the solution D, E and stirring uniformly; then adding the solution F, heating to boil, and reacting for 2-3 h; and finally, washing, neutralizing, drying and roasting in a muffle furnace to obtain the ADMS-P-CaO expanding agent finished product with the surface coated by the iron oxide.
5. The method for preparing a core-shell structure expansive agent for concrete according to claim 4, wherein the specific surface area of the sample is 450m in step S12/kg。
6. The method for preparing a core-shell structure expansive agent for concrete according to claim 4 or 5, wherein in the step S4, the temperature of the muffle furnace is raised in a manner that: firstly, heating to 560-700 ℃ within 1-3 h, and preserving heat for 1-2.5 h; and finally, gradually cooling to room temperature within 2-4 h under the protection of nitrogen.
7. The method for preparing a core-shell structure expansive agent for concrete according to claim 6, wherein in step S4, the muffle furnace is heated in a manner that: firstly, heating to 680 ℃ within 2h, and preserving heat for 2 h; finally, the temperature is gradually reduced to the room temperature within 3.5 hours under the protection of nitrogen.
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| CN103964722A (en) * | 2014-05-04 | 2014-08-06 | 苏州市市政工程设计院有限责任公司 | Chemical admixture capable of improving effectiveness of concrete expanding agent under restrictive condition |
| CN106348643A (en) * | 2016-08-19 | 2017-01-25 | 桂林华越环保科技有限公司 | Modified concrete expansive agent |
| CN108249811A (en) * | 2018-02-02 | 2018-07-06 | 日照弗尔曼新材料科技有限公司 | A kind of concrete anticracking swelling agent and preparation method thereof |
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- 2018-10-10 CN CN201811178726.9A patent/CN109160766B/en active Active
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| JPH04285080A (en) * | 1991-03-14 | 1992-10-09 | Tsutsunaka Plast Ind Co Ltd | Composition for inorganic expanded body |
| CN103964722A (en) * | 2014-05-04 | 2014-08-06 | 苏州市市政工程设计院有限责任公司 | Chemical admixture capable of improving effectiveness of concrete expanding agent under restrictive condition |
| CN106348643A (en) * | 2016-08-19 | 2017-01-25 | 桂林华越环保科技有限公司 | Modified concrete expansive agent |
| CN108249811A (en) * | 2018-02-02 | 2018-07-06 | 日照弗尔曼新材料科技有限公司 | A kind of concrete anticracking swelling agent and preparation method thereof |
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