Concrete anti-alkali agent and preparation method thereof

Abstract

The invention discloses a concrete anti-alkali agent and a preparation method thereof, and belongs to the technical field of concrete. The concrete anti-alkali agent is prepared by selecting the natural plant waste, the macromolecular organic acid salt, the polyacrylate, the polyethylene glycol, the surfactant and the composite mineral admixture as components of the anti-alkali agent, and the concrete anti-alkali agent can effectively resist alkali aggregate reaction and improve the alkali resistance and durability of concrete.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete, and particularly relates to a concrete alkali-resistant agent and a preparation method thereof. Background Art

[0002] At present, the concrete alkali-resistant agents on the market are mainly divided into two categories: one is the silicate-type alkali-resistant agent, and the other is the inorganic salt-type alkali-resistant agent. The main component of the silicate-type alkali-resistant agent is silicate cement clinker, such as ordinary Portland cement, slag Portland cement, etc. The advantages of this type of alkali-resistant agent are its wide source, low price, and its ability to effectively resist alkali-aggregate reaction and improve the durability of concrete. However, since its main component is silicate cement clinker, its alkali activity is relatively low, and the reaction with alkali in concrete is relatively slow, so its alkali-resistant ability is relatively weak. The inorganic salt-type alkali-resistant agents mainly include compounds such as calcium carbonate and phosphate. The advantages of this type of alkali-resistant agent are its strong alkali-resistant ability and its ability to effectively inhibit the alkali-aggregate reaction in concrete. However, the disadvantages of this type of alkali-resistant agent are its high cost, and it is easy to decompose under high-temperature environment, posing a certain pollution risk to the environment.

[0003] Generally speaking, the existing concrete alkali-resistant agents on the market generally have problems such as poor alkali-resistant performance, high cost, and non-environmental protection. In order to improve these problems, it is necessary to develop a concrete alkali-resistant agent with good alkali-resistant performance and low cost. Summary of the Invention

[0004] In view of the above technical problems, the present invention provides a concrete alkali-resistant agent and a preparation method thereof, which can effectively resist alkali-aggregate reaction and improve the alkali-resistant performance and durability of concrete.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One object of the present invention is to provide a concrete alkali-resistant agent, comprising the following raw materials in parts by mass: 60 - 80 parts of natural plant waste, 60 - 80 parts of high molecular organic acid salt, 10 - 20 parts of polyacrylate, 3 - 8 parts of polyethylene glycol, 7 - 12 parts of surfactant, and 15 - 30 parts of composite mineral admixture.

[0007] The present invention selects natural plant waste, high molecular organic acid salt, polyacrylate, polyethylene glycol, surfactant, and composite mineral admixture as the components of the alkali-resistant agent. Starting from both chemical and physical aspects, by regulating the dosage ratio of each raw material and utilizing the synergistic effect of the mass of each raw material, the alkali-resistant performance of concrete is improved, and the phenomenon of efflorescence is reduced.

[0008] Optionally, the natural plant waste is one or more of corn straw, rice straw, and reed straw. By selecting appropriate natural plant waste, the resources of these plant wastes can be fully utilized, and at the same time, the production cost can be reduced.

[0009] Optionally, the polymer organic acid salt is a mixture of sodium polyvinyl maleate and sodium polyacrylate sulfonate, and the mass ratio is 2:1. The selection of this polymer organic acid salt not only has good alkali resistance, but also has good durability and environmental friendliness.

[0010] Optionally, the mass ratio of the natural plant waste to the polymer organic acid salt is 1:1.

[0011] Optionally, the polyacrylate is sodium polyacrylate.

[0012] Optionally, the surfactant is sodium sulfonate modified by polyurethane. The selection of this surfactant not only ensures the excellent performance of the concrete alkali resistance agent, but also makes it have good processability.

[0013] Optionally, the composite mineral admixture is a mixture of diatomite, zeolite, and sepiolite, and the mass ratio is 3:2:3. The use of this composite mineral admixture not only improves the alkali resistance of the concrete, but also improves the workability of the concrete.

[0014] Diatomaceous earth has a porous structure and a large specific surface area, which endows it with strong adsorption properties. In the alkali-resistant agent, diatomaceous earth can adsorb alkaline substances in concrete, reduce the precipitation of alkaline substances such as calcium hydroxide, and thus lower the alkalinity of concrete. In addition, the porous structure of diatomaceous earth helps to improve the impermeability of concrete, reduce the penetration of water and erosion media, and thereby enhance the durability of concrete. Zeolite also has excellent adsorption properties and can absorb small molecule substances decomposed by the product at high temperatures (such as gaseous or liquid water molecules) and the heat generated on the surface of the friction pair during braking friction. In the concrete alkali-resistant agent, zeolite can adsorb and fix alkaline substances, reducing the erosion of alkaline substances on concrete. The structure of zeolite can also adjust the pore structure of concrete to a certain extent, improving the density and durability of concrete. Sepiolite has a layered structure and contains a large amount of crystal water. In the alkali-resistant agent, the layered structure of sepiolite can adsorb and fix alkaline substances, reducing the migration and erosion of alkaline substances. The high-temperature resistance of sepiolite also helps to improve the stability of concrete in high-temperature environments. The present invention mixes diatomaceous earth, zeolite, and sepiolite in a fixed ratio, which is optimized based on their respective adsorption properties and physical and chemical characteristics. The porous structure and layered structure of diatomaceous earth and sepiolite provide a strong adsorption capacity, while zeolite enhances the adsorption and ion exchange capacity through its unique pore structure. This ratio helps to balance the adsorption properties and physical and chemical characteristics of each component to achieve the best alkali-resistant effect. That is to say, diatomaceous earth, zeolite, and sepiolite mainly play a role in the concrete alkali-resistant agent by adsorbing and fixing alkaline substances, adjusting the pore structure of concrete, and improving the density and durability of concrete. The physical and chemical characteristics and interaction relationships of these minerals together improve the alkali-resistant performance of concrete.

[0015] The second object of the present invention is to provide a preparation method of a concrete alkali-resistant agent, comprising the following steps:

[0016] Crush natural plant waste to obtain biomass powder, and mix the biomass powder with a high molecular organic acid salt to obtain a mixture;

[0017] Mix the mixture with polyacrylate, polyethylene glycol, a surfactant, and a composite mineral admixture in sequence to obtain a concrete alkali-resistant agent.

[0018] In the present invention, natural plant waste is first mixed with a high-molecular organic acid salt, which can ensure sufficient reaction between the two to form a stable base. Then, polyacrylate, polyethylene glycol, a surfactant, and a composite mineral admixture are gradually added. Each step of physical blending is to ensure the uniform distribution of each component in the final product, thereby improving the overall performance of the alkali-resistant agent. The defined dosage ratio and mixing sequence are also related to chemical stability and reaction kinetics. For example, the addition of polyacrylate will affect the pH value of the mixture, and further affect the reaction activity of the high-molecular organic acid salt. By controlling the dosage ratio and mixing sequence, the reaction conditions can be optimized to ensure that the chemical reaction in the alkali-resistant agent proceeds under the best conditions.

[0019] Optionally, the mass ratio of the natural plant waste to the high-molecular organic acid salt is 1:1. This ratio is selected because the high-molecular organic acid salt can interact with components such as cellulose and silicate in the plant waste to form a stable complex, improving the alkali resistance effect.

[0020] A third object of the present invention is to provide a concrete, the raw materials of which include the above-mentioned concrete alkali-resistant agent, and the addition amount of the concrete alkali-resistant agent is 0.1-3 wt% of the mass of cement in the concrete.

[0021] In the concrete alkali-resistant agent provided by the present invention, natural plant waste contains a large amount of cellulose and silicate, which can be used as active fillers to enhance the mechanical properties of concrete. Moreover, it has certain adsorption properties, which helps to absorb and fix alkaline substances in concrete and reduce the efflorescence phenomenon. The polymer organic acid salt can react with calcium hydroxide generated by cement hydration to form a stable complex, reducing the precipitation of calcium hydroxide, thereby reducing the alkalinity of concrete and improving the durability and impermeability of concrete. Polyacrylate has good water retention and dispersibility, which can improve the workability of concrete, reduce the evaporation of water, and thus reduce surface cracking and efflorescence caused by water evaporation. At the same time, it can also react with cement hydration products to improve the compactness of concrete. Polyethylene glycol has good wettability and adhesiveness, which can be used as a plasticizer for concrete to improve the fluidity and processability of concrete, and can also reduce the surface tension of water, promote the uniform distribution of water in concrete, and reduce the alkalinity non-uniformity caused by uneven water distribution. Surfactants such as polyurethane-modified aliphatic sodium sulfonate can reduce the surface tension of the liquid, improve the dispersibility of each component in concrete, enhance the compatibility between the alkali-resistant agent and the concrete matrix, and improve the alkali-resistant effect. Composite mineral admixtures such as diatomite, zeolite, and sepiolite have a porous structure and a large specific surface area, which can adsorb and fix alkaline substances in concrete to reduce the efflorescence phenomenon. At the same time, they can also be used as active fillers to undergo a secondary reaction with cement hydration products to improve the strength and durability of concrete. The present invention uses natural plant waste, polymer organic acid salt, polyacrylate, polyethylene glycol, surfactant, and composite mineral admixture as raw materials, and through the interaction of multiple mechanisms such as physical adsorption, chemical complexation, and secondary hydration reaction, jointly improves the alkali-resistant performance of concrete, reduces the efflorescence phenomenon, and improves the durability and mechanical properties of concrete.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] The concrete alkali-resistant agent of the present invention not only has good alkali-resistant performance and durability, but also has the characteristics of being green and economical. Its raw materials are widely sourced, the process is simple, and it is easy to produce on a large scale. At the same time, its unique formulation design ensures both good alkali-resistant performance and good workability of concrete during use. Specific Embodiments

[0024] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0025] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0027] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0028] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0029] The present invention provides a concrete alkali-resistant agent, which comprises the following raw materials in parts by mass: 60 - 80 parts of natural plant waste, 60 - 80 parts of high molecular organic acid salts, 10 - 20 parts of polyacrylate, 3 - 8 parts of polyethylene glycol, 7 - 12 parts of surfactant, and 15 - 30 parts of composite mineral admixture.

[0030] Optionally in some embodiments, the concrete alkali-resistant agent contains 60 parts, 70 parts, 80 parts of natural plant waste, or any range or sub-range between the aforementioned ratios.

[0031] Optionally in some embodiments, the concrete alkali-resistant agent contains 60 parts, 70 parts, 80 parts of high molecular organic acid salts, or any range or sub-range between the aforementioned ratios.

[0032] Optionally in some embodiments, the concrete alkali-resistant agent contains 10 parts, 15 parts, 20 parts of polyacrylate, or any range or sub-range between the aforementioned ratios.

[0033] Optionally, in some embodiments, the concrete alkali-resistant agent contains 3 parts, 5 parts, 8 parts of polyethylene glycol or any range or sub-range between the aforementioned ratios.

[0034] Optionally, in some embodiments, the concrete alkali-resistant agent contains 7 parts, 9 parts, 12 parts of surfactant or any range or sub-range between the aforementioned ratios.

[0035] Optionally, in some embodiments, the concrete alkali-resistant agent contains 15 parts, 22 parts, 30 parts of composite mineral admixture or any range or sub-range between the aforementioned ratios.

[0036] In some embodiments, the natural plant waste can be one or more of corn straw, rice straw and reed straw. Exemplarily, in the following embodiments of the present invention, the natural plant waste is corn straw, and the effect verification is carried out as an example. The corn straw can be used only after being crushed to a particle size between 180 and 250 microns. This particle size can not only increase the surface area but also maintain the gaps between the particles, which is beneficial to subsequent mixing and reaction. If the particle size is too small, it will lead to uneven mixing; if the particle size is too large, it will affect the full contact with the high molecular organic acid salt and reduce the alkali-resistant effect. Exemplarily, in the following embodiments of the present invention, the corn straw is crushed to 250 microns.

[0037] In the following embodiments of the present invention, the high molecular organic acid salt is a mixture of sodium polyvinyl alcohol maleate and sodium polypropylene sulfonate, and the mass ratio is 2:1.

[0038] In the following embodiments of the present invention, the polyacrylate is sodium polyacrylate. As an example, SAP 90 is specifically selected in the following embodiments.

[0039] In the following embodiments of the present invention, the surfactant is sodium polyurethane-modified aliphatic sulfonate. As an example, ND-100 is specifically selected in the following embodiments.

[0040] In the following embodiments of the present invention, the composite mineral admixture is a mixture of diatomite, zeolite and sepiolite, and the mass ratio is 3:2:3.

[0041] The preparation method of the concrete alkali-resistant agent includes the following steps:

[0042] (1) Dry and crush the natural plant waste to obtain biomass powder, and mix the biomass powder with the high molecular organic acid salt to obtain mixture 1;

[0043] (2) Mix the polyacrylate with the mixture 1 to obtain mixture 2;

[0044] (3) Physically blend the said mixture 2 with polyethylene glycol to obtain mixture 3;

[0045] (4) Physically blend the said mixture 3 with a surfactant to obtain mixture 4;

[0046] (5) Mix the said mixture 4 with a composite mineral admixture to obtain a concrete alkali-resistant agent.

[0047] In the following embodiments of the present invention, the mass ratio of the natural plant waste to the polymer organic acid salt is 1:1.

[0048] The said concrete alkali-resistant agent can be used to prepare concrete, and the addition amount of the said concrete alkali-resistant agent is 0.1-3 wt% of the mass of cement in the concrete, such as 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%. Exemplarily, in the following embodiments of the present invention, the addition amount of the said concrete alkali-resistant agent in the concrete is 0.5 wt% of the mass of cement in the concrete.

[0049] The "parts" mentioned in the present invention refer to parts by mass unless otherwise specified.

[0050] All raw materials used in the present invention are obtained by purchasing in the market.

[0051] The polyethylene glycol used in the embodiments of the present invention is PEG200.

[0052] The technical solution of the present invention is further described below through embodiments.

[0053] Example 1

[0054] A concrete alkali-resistant agent, comprising the following raw materials in parts by mass: 60 parts of natural plant waste (corn straw), 60 parts of polymer organic acid salt (a mixture of polyvinyl alcohol maleate and sodium polyacrylate sulfonate, with a mass ratio of 2:1); 10 parts of polyacrylate (sodium polyacrylate, SAP 90), 3 parts of polyethylene glycol, 7 parts of surfactant (polyurethane-modified aliphatic sulfonate, ND-100), and 15 parts of composite mineral admixture (a mixture of diatomite, zeolite, and sepiolite, with a mass ratio of 3:2:3).

[0055] The preparation method comprises the following steps:

[0056] (1) Dry and crush the natural plant waste to obtain biomass powder with a particle size of 250 microns, add the obtained biomass powder and the polymer organic acid salt to deionized water so that the mass fraction of the polymer organic acid salt is 10 wt%, then stir at 50 °C and 500 rpm for 2 hours, and adjust the pH = 8 to obtain mixture 1;

[0057] (2) Add polyacrylate to Mixture 1 and stir for 1 hour at 65 °C to obtain Mixture 2;

[0058] (3) Continuously add polyethylene glycol with a mass concentration of 10 wt% (the solvent is deionized water) to Mixture 2 and stir for 1.5 hours at 50 °C and 10000 rpm to obtain Mixture 3;

[0059] (4) Add a surfactant with a mass concentration of 15 wt% (the solvent is methanol) to Mixture 3 and stir for 2 hours at 50 °C and 5000 rpm to obtain Mixture 4;

[0060] (5) Add a composite mineral admixture to Mixture 4 and stir evenly to obtain an alkali-resistant agent for concrete.

[0061] Example 2

[0062] An alkali-resistant agent for concrete, comprising the following raw materials in parts by mass: 70 parts of natural plant waste (corn straw), 70 parts of a high molecular organic acid salt (a mixture of sodium polyvinyl alcohol maleate and sodium polyacrylate sulfonate, with a mass ratio of 2:1); 15 parts of polyacrylate (sodium polyacrylate, SAP 90), 5 parts of polyethylene glycol, 9 parts of a surfactant (sodium polyurethane-modified aliphatic sulfonate, ND-100), and 22 parts of a composite mineral admixture (a mixture of diatomaceous earth, zeolite, and sepiolite, with a mass ratio of 3:2:3).

[0063] The preparation method is the same as that of Example 1.

[0064] Example 3

[0065] An alkali-resistant agent for concrete, comprising the following raw materials in parts by mass: 80 parts of natural plant waste (corn straw), 80 parts of a high molecular organic acid salt (a mixture of sodium polyvinyl alcohol maleate and sodium polyacrylate sulfonate, with a mass ratio of 2:1); 20 parts of polyacrylate (sodium polyacrylate, SAP 90), 8 parts of polyethylene glycol, 12 parts of a surfactant (sodium polyurethane-modified aliphatic sulfonate, ND-100), and 30 parts of a composite mineral admixture (a mixture of diatomaceous earth, zeolite, and sepiolite, with a mass ratio of 3:2:3).

[0066] The preparation method is the same as that of Example 1.

[0067] Comparative Example 1

[0068] Same as Example 2, except that the dosage of the high molecular organic acid salt is 50 parts.

[0069] Comparative Example 2

[0070] Same as Example 2, except that sodium polyvinyl alcohol maleate is used alone as the high molecular organic acid salt, that is, 70 parts of sodium polyvinyl alcohol maleate.

[0071] Comparative Example 3

[0072] Same as Example 2, except that SAP 90 was replaced with SAP 130 in equal mass.

[0073] Comparative Example 4

[0074] Same as Example 2, except that the surfactant was replaced with ND-150 in equal mass.

[0075] Comparative Example 5

[0076] Same as Example 2, except that the composite mineral admixture (a mixture of diatomite, zeolite and sepiolite with a mass ratio of 3:2:3) was replaced with a composite mineral admixture (a mixture of diatomite and sepiolite with a mass ratio of 1:1) in equal mass.

[0077] Performance test:

[0078] The performance of the alkali-resistant agents prepared in Examples 1-3 and Comparative Examples 1-5 was tested. The specific method was as follows: The concrete alkali-resistant agent was added to conventional alkali-activated slag cement in an amount of 0.5 wt% of the cement mass. The obtained mixture was cured for 24 hours under standard conditions of a constant temperature (20±2°C) and a constant humidity (90±2%), and then stored in a ventilated place for 24 hours. The alkali-activated slag cement was cyclically cured in the above environment for 28 days, and its alkali efflorescence area and compressive strength at 28 days were detected (the performance was tested according to the standard of GB 175-2007 "Common Portland Cement"). Three groups were repeated and the average value was taken. At the same time, the alkali-activated slag cement without adding the alkali-resistant agent was used as the blank group, and the results are shown in Table 1.

[0079] Table 1 Performance test results of different concrete alkali-resistant agents

[0080] Addition amount of concrete alkali-resistant agent / % Relative whitening area / % 28d compressive strength / MPa Blank group 0 94.21 32.4 Example 1 0.5 2.32 62.7 Example 2 0.5 2.10 64.9 Example 3 0.5 2.65 63.2 Comparative example 1 0.5 26.71 41.3 Comparative example 2 0.5 11.46 54.6 Comparative example 3 0.5 13.57 52.9 Comparative example 4 0.5 16.55 49.7 Comparative example 5 0.5 21.47 44.6

[0081] As can be seen from Table 1, the concrete alkali-resistant agents prepared in Examples 1-3 of the present invention can effectively inhibit the alkali efflorescence problem of alkali-activated slag cement. Compared with the blank group without adding the concrete alkali-resistant agent, Examples 1-3 not only have good alkali resistance and durability, but also the use of natural plant waste as raw materials greatly reduces the production cost. The present invention alleviates the problems of poor alkali resistance, high cost and non-environmental protection in the prior art.

[0082] The above is only the preferred specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in this application should be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

1. A concrete anti-alkali agent, characterized in that: The invention comprises the following raw materials in parts by weight: 60-80 parts of natural plant waste, 60-80 parts of high molecular weight organic acid salt, 10-20 parts of polyacrylic acid salt, 3-8 parts of polyethylene glycol, 7-12 parts of surfactant and 15-30 parts of composite mineral admixture.

2. The concrete anti-alkali agent according to claim 1, characterized in that: The natural plant waste is one or more of corn stalks, rice straw and reed stalks.

3. The concrete anti-alkali agent according to claim 1, characterized in that: The polymer organic acid salt is a mixture of sodium polyvinyl alcohol maleate and sodium polypropylene sulfonate, with a mass ratio of 2:

1.

4. The concrete anti-alkali agent according to claim 1, characterized in that: The polyacrylate is sodium polyacrylate.

5. The concrete anti-alkali agent according to claim 1, characterized in that: The surfactant is polyurethane modified sodium aliphatic sulfonate.

6. The concrete anti-alkali agent according to claim 1, characterized in that: The composite mineral admixture is a mixture of diatomite, zeolite and sepiolite, with a mass ratio of 3:2:

3.

7. A method for preparing a concrete anti-alkali agent according to any one of claims 1 to 6, characterized in that: The following steps are involved: Drying and crushing natural plant waste to obtain biomass powder, and mixing the biomass powder with a high molecular weight organic acid salt to obtain a mixture; The mixture is sequentially mixed with polyacrylate, polyethylene glycol, a surfactant and a composite mineral admixture to obtain a concrete anti-alkali agent.

8. The method for preparing a concrete anti-alkali agent according to claim 7, characterized in that: The mass ratio of the natural plant waste to the high molecular organic acid salt is 1:

1.

9. A concrete, characterized in that: The raw materials include the concrete alkali-resistant agent according to any one of claims 1 to 6, and the added amount of the concrete alkali-resistant agent is 0.1-3wt% of the mass of cement in the concrete.