Hydrated calcium aluminate carbonate early strength agent for concrete, preparation method and application thereof

Abstract

The invention discloses a hydrated calcium aluminate carbonate early strength agent for concrete and a preparation method and application thereof, belonging to the technical field of building material concrete admixtures. An alkaline mixed solution containing a cementitious material X and a carbonate solution are mixed, and high-speed stirring hydration, filtering, drying and grinding are performed in sequence to prepare the hydrated calcium aluminate carbonate early strength agent. The preparation method disclosed in the invention is simple and easy to implement, the raw materials are few in variety and cheap and easy to obtain, the prepared early strength agent has excellent early strength effect, and does not affect the later compressive strength of concrete.

Description

Technical Field

[0001] The invention belongs to the technical field of building material concrete admixtures, and in particular relates to a hydrated calcium carbonate aluminate early strength agent for concrete, and a preparation method and application thereof. Background Art

[0002] Early strength agent is a concrete admixture that can be used to accelerate cement hydration and hardening, and effectively improve the early strength of concrete. This admixture is usually used in winter construction, emergency repairs, or projects that need to quickly reach strength. It plays an indispensable and important role in certain construction projects and the production of cement concrete products. It can bring economic and engineering benefits to construction projects, improve the efficiency of cement concrete product production, and increase economic benefits.

[0003] Early strength agents can achieve high early strength with low dosage, are simple and convenient to use, and are conducive to improving production efficiency. However, while traditional early strength agents improve the early strength of concrete, most of them will cause later strength shrinkage and reduce concrete working performance.

[0004] There are many types of early strength agents, and different early strength agents will have different effects on concrete. For example, chloride salts are currently the best early strength agent, but the introduction of chloride ions will accelerate the corrosion of steel bars and reduce the durability of concrete, so they are now banned in reinforced concrete; sulfate early strength agents are prone to cause concrete frost, alkali-aggregate reaction and sulfate erosion, and may also lead to coarsening of the pore structure of concrete in the later stage; while organic early strength agents, such as calcium formate, triethanolamine, early strength polycarboxylate water reducer, etc., are rarely added and difficult to control. Over-addition will cause slow setting of concrete, and are not suitable for steam-cured concrete. In addition, the most researched is the organic-inorganic composite early strength agent. This composite early strength agent has a significant early strength effect and can complement the two types of early strength agents. However, this early strength agent has a complex mechanism of action and unstable composition, and it is difficult to control the dosage in actual application.

[0005] Hydrated calcium aluminate (3CaO·Al2O3·CaCO3·11H2O, HCAC) exists stably in the form of monocarbonate calcium aluminate crystals. Adding hydrated calcium aluminate to cement concrete can significantly improve the early strength of concrete. Hydrated calcium aluminate has better insolubility and stability, can exist stably in concrete, and is not easy to decompose or transform, which helps to maintain the early strength of concrete. There are few studies on hydrated calcium aluminate as a concrete early strength agent. Studies have shown that adding fine calcium carbonate powder to cement concrete can promote the formation of hydrated calcium aluminate in concrete and improve the compressive strength of concrete at all ages. Chinese patent CN117303835A proposes a calcium aluminate carbonitious material and its preparation method and application. It mainly uses calcium carbonate solid waste and aluminum-containing active minerals to prepare hydrated calcium aluminate carbonitious material, and adds alkali activator and setting components. It belongs to a calcium carbonate solid waste treatment method. The hydrated calcium aluminate carbonitious material prepared by it has a high content of inactive calcium carbonate. It can be inferred that if it is used as an early strength agent, the effect will be greatly reduced. Secondly, the calcium carbonate solid waste needs to go through processes such as crushing, drying, and grinding to meet the required calcium carbonate fineness, and the energy consumption is relatively high.

[0006] Therefore, there is an urgent need to provide a hydrated calcium aluminate carbonate early strength agent with simple process, excellent early strength effect and no effect on the later compressive strength of concrete. Summary of the invention

[0007] In view of the above technical problems, the present invention proposes a hydrated calcium aluminate carbonate early strength agent for concrete and its preparation method and application. The hydrated calcium aluminate carbonate early strength agent uses a small number of raw materials that are cheap and easy to obtain, has a simple preparation process, requires less equipment, and can be industrialized and mass-produced; and the prepared early strength agent has excellent early strength effect and does not affect the later compressive strength of concrete.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] One of the technical solutions of the present invention:

[0010] A method for preparing a hydrated calcium aluminate carbonate early strength agent for concrete comprises the following steps:

[0011] The alkaline mixed solution containing the gelling material X and the carbonate solution are mixed, and the mixture is stirred at high speed for hydration, filtered, dried and ground in sequence to prepare the hydrated calcium aluminate carbonate early strength agent;

[0012] Wherein, the cementitious material X is aluminate cement; and the volume ratio of the alkaline mixed solution containing the cementitious material X to the carbonate solution is 1:(0.2-1).

[0013] Beneficial effects: The hydrated calcium aluminate prepared within this volume ratio range has a high content and few impurities. If the amount of carbonate added is small, it is not enough to generate enough hydrated calcium aluminate. If the amount of carbonate added is large, more calcium carbonate impurities will be generated, which will reduce the early strength effect of the early strength agent.

[0014] Preferably, the cementitious material X is aluminate cement that complies with GB / T201-2015.

[0015] Furthermore, the gelling material X includes one or more of CA50, CA60, CA70 and CA80.

[0016] Preferably, the mass concentration of the alkaline mixed solution containing the gelling material X is 10%-50%;

[0017] The pH of the alkaline mixed solution containing the gelling material X is 13±1.

[0018] Beneficial effect: The early strength agent prepared under the pH value conditions specified in the present invention has good strength; if the pH is lower than this, by-products such as aluminum hydroxide gel will appear, affecting the strength of cement.

[0019] Preferably, the alkaline mixed solution containing the gelling material X is prepared by: dissolving the gelling material X in water, adding a pH regulator and mixing uniformly;

[0020] The pH adjuster is a soluble alkaline substance.

[0021] Furthermore, the soluble alkaline substance includes alkali metal hydroxide (preferably sodium hydroxide, potassium hydroxide) or sodium aluminate.

[0022] Preferably, the mass concentration of the carbonate solution is 10%-50%.

[0023] Beneficial effect: Under the mass concentration of the carbonate solution defined in the present invention, the normal reaction can be ensured and the yield of hydrated calcium aluminate can be improved. The problem of low yield of hydrated calcium aluminate due to too low concentration, resulting in increased cost, and the problem of large amount of ion precipitation and slow reaction process due to too high concentration can be avoided.

[0024] Furthermore, the carbonate in the carbonate solution includes potassium carbonate, sodium carbonate or ammonium carbonate.

[0025] Preferably, the rotation speed during the high-speed stirring hydration process is 100-2000 r / min; the time of high-speed stirring hydration is 5-10 h.

[0026] Beneficial effect: Within this speed range, the reactants can be stirred and mixed evenly and react fully without causing excessive production energy consumption and a sharp increase in costs.

[0027] Preferably, the drying temperature in the drying process is 40° C.-100° C.; and the drying is performed until constant weight.

[0028] Preferably, the grinding process is: grinding the dried product to an average particle size of 200-2500 meshes.

[0029] Beneficial effect: The particle size range matches the particle size range of concrete cementitious materials. Grinding too coarsely will affect the hydration reaction process. Grinding too finely may partially improve the early strength effect, but the energy consumption is too high.

[0030] The second technical solution of the present invention:

[0031] A hydrated calcium aluminate carbonate early strength agent for concrete is prepared by the above preparation method.

[0032] The third technical solution of the present invention:

[0033] For example, the above-mentioned concrete hydrated calcium aluminate early strength agent is used to improve the early strength of concrete.

[0034] Preferably, the solid content of the hydrated calcium aluminate carbon early strength agent is 1-5wt.% of the cementitious material Y;

[0035] The cementitious material Y is the raw material in the concrete.

[0036] Compared with the prior art, the present invention has the following advantages and technical effects:

[0037] 1. The calcium aluminate hydrate early strength agent prepared by the present invention has a small number of raw materials, a simple preparation process, and requires less production equipment, and is easy to carry out industrial production;

[0038] 2. The preparation method of the hydrated calcium aluminate carbonate early strength agent disclosed in the present invention is to prepare an early strength agent with excellent early strength effect by adjusting the raw material ratio and the grinding fineness, and the early strength agent has good adaptability to cementitious materials;

[0039] 3. The hydrated calcium aluminate early strength agent prepared by the present invention is simple to use and can be directly used in the concrete mixing process.

[0040] Direct addition has good dispersing effect in concrete system;

[0041] 4. The hydrated calcium aluminate carbonate early strength agent prepared by the present invention has a small dosage, a significant early strength effect, and can slightly improve the later strength of concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0043] Figure 1 The XRD pattern of the hydrated calcium aluminate carbonate early strength agent powder prepared in Example 1-5;

[0044] Figure 2 This is the particle size distribution diagram of the hydrated calcium aluminate early strength agent powder prepared in Examples 1-5. DETAILED DESCRIPTION

[0045] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0046] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0047] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation 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 associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0048] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0049] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0050] The invention discloses a hydrated calcium aluminate carbonate early strength agent for concrete, a preparation method and an application thereof. The raw materials of the early strength agent include carbonate, a pH regulator and a gelling material. The early strength agent is prepared by adding water and high-speed mechanical stirring, followed by filtering, drying and grinding.

[0051] The carbonate is a soluble carbonate, including potassium carbonate, sodium carbonate, ammonium carbonate and other soluble carbonates. The purity of the soluble carbonate should be above industrial grade.

[0052] The pH adjuster is a soluble alkaline substance, including alkali metal hydroxides (sodium hydroxide, potassium hydroxide), sodium aluminate and other soluble alkaline substances. The purity of the alkaline material should reach industrial grade or above.

[0053] The cementitious material is aluminate cement of types such as CA50, CA60, CA70 and CA80 that conforms to GB / T201-2015 "Aluminate Cement".

[0054] A method for preparing a hydrated calcium aluminate carbonate early strength agent for concrete is as follows:

[0055] Step 1: dissolving the gelling material in tap water at a mass percentage concentration of 10%-50%, and adjusting the pH value of the mixed solution to 13±1 with a pH regulator to obtain a mixed solution A;

[0056] Step 2: Dissolve carbonate in tap water at a mass percentage concentration of 10%-50% to obtain solution B;

[0057] Step 3: Mix the mixed solution A and solution B in a volume ratio of 1:0.2-1, and stir them in a high-speed stirrer for 5-10 hours at a stirring speed of 100r / min-2000r / min;

[0058] Step 4: Filter the mixed solution after stirring and hydrating in step 3 to obtain hydrated calcium carbonoaluminate cake, and dry the cake in an oven at a drying temperature of 40°C-100°C;

[0059] Step 5: Grind the dried hydrated calcium aluminate with a ball mill to an average particle size of 200-2500 meshes to obtain hydrated calcium aluminate early strength agent powder for concrete.

[0060] The amount of the hydrated calcium aluminate carbonate early strength agent in concrete is 1%-5% of the mass of the cementitious material.

[0061] The "room temperature" in the present invention refers to 20-30°C unless otherwise specified.

[0062] The "parts" described in the present invention, unless otherwise specified, refer to parts by mass.

[0063] The raw materials used in the present invention are all purchased from the market.

[0064] The technical solution of the present invention is further illustrated by the following embodiments.

[0065] Example 1

[0066] A method for preparing a hydrated calcium aluminate carbonate early strength agent for concrete comprises the following steps:

[0067] Step 1: Dissolve the cementitious material CA50 aluminate cement in tap water at a mass percentage concentration of 10%, and adjust the pH value of the mixed solution to 13±1 with a pH regulator, sodium hydroxide, to obtain a mixed solution A;

[0068] Step 2: Dissolve sodium carbonate in tap water at a mass percent concentration of 10% to obtain solution B;

[0069] Step 3: Mix the mixed solution A and solution B at a volume ratio of 1:0.2, and stir them in a high-speed stirrer for 5 hours at a stirring speed of 100 r / min;

[0070] Step 4: Filter the mixed solution after stirring and hydrating in step 3 to obtain hydrated calcium carbonoaluminate cake, and dry the cake in an oven at a drying temperature of 40°C;

[0071] Step 5: Grind the dried hydrated calcium aluminate with a ball mill to an average particle size of 2500 meshes to obtain hydrated calcium aluminate early strength agent powder for concrete.

[0072] Example 2

[0073] A method for preparing a hydrated calcium aluminate carbonate early strength agent for concrete comprises the following steps:

[0074] Step 1: Dissolve the cementitious material CA60 aluminate cement in tap water at a mass percentage concentration of 20%, and adjust the pH value of the mixed solution to 13±1 with a pH regulator sodium metaaluminate to obtain a mixed solution A;

[0075] Step 2: Dissolve sodium carbonate in tap water at a mass percent concentration of 20% to obtain solution B;

[0076] Step 3: Mix the mixed solution A and solution B at a volume ratio of 1:0.4, and stir them in a high-speed mixer for hydration for 6 hours at a stirring speed of 500 r / min;

[0077] Step 4: Filter the mixed solution after stirring and hydrating in step 3 to obtain hydrated calcium carbonoaluminate cake, and dry the cake in an oven at a drying temperature of 55°C;

[0078] Step 5: Grind the dried hydrated calcium aluminate with a ball mill to an average particle size of 1500 mesh to obtain hydrated calcium aluminate early strength agent powder for concrete.

[0079] Example 3

[0080] A method for preparing a hydrated calcium aluminate carbonate early strength agent for concrete comprises the following steps:

[0081] Step 1: Take the cementitious material CA70 and dissolve it in tap water with a mass percentage concentration of 30%, and adjust the pH value of the mixed solution to 13±1 with a pH regulator potassium hydroxide to obtain a mixed solution A;

[0082] Step 2: Dissolve potassium carbonate in tap water at a mass percent concentration of 30% to obtain solution B;

[0083] Step 3: Mix the mixed solution A and solution B at a volume ratio of 1:0.6, and stir them in a high-speed mixer for hydration for 7 hours at a stirring speed of 1000 r / min;

[0084] Step 4: Filter the mixed solution after stirring and hydrating in step 3 to obtain hydrated calcium carbonoaluminate cake, and dry the cake in an oven at a drying temperature of 70°C;

[0085] Step 5: Grind the dried hydrated calcium aluminate with a ball mill to an average particle size of 1000 mesh to obtain hydrated calcium aluminate early strength agent powder for concrete.

[0086] Example 4

[0087] A method for preparing a hydrated calcium aluminate carbonate early strength agent for concrete comprises the following steps:

[0088] Step 1: Take the cementitious material CA70 and dissolve it in tap water with a mass percentage concentration of 40%, and adjust the pH value of the mixed solution to 13±1 with a pH regulator potassium hydroxide to obtain a mixed solution A;

[0089] Step 2: Dissolve potassium carbonate in tap water at a mass percent concentration of 40% to obtain solution B;

[0090] Step 3: Mix the mixed solution A and solution B at a volume ratio of 1:0.8, and stir them in a high-speed mixer for hydration for 8 hours at a stirring speed of 1500 r / min;

[0091] Step 4: Filter the mixed solution after stirring and hydrating in step 3 to obtain hydrated calcium aluminate carbonate cake, and dry the cake in an oven at a drying temperature of 85°C;

[0092] Step 5: Grind the dried hydrated calcium aluminate with a ball mill to an average particle size of 500 meshes to obtain hydrated calcium aluminate early strength agent powder for concrete.

[0093] Example 5

[0094] A method for preparing a hydrated calcium aluminate carbonate early strength agent for concrete comprises the following steps:

[0095] Step 1: Take the cementitious material CA80 and dissolve it in tap water with a mass percentage concentration of 50%, and adjust the pH value of the mixed solution to 13±1 with a pH regulator sodium hydroxide to obtain a mixed solution A;

[0096] Step 2: dissolve ammonium carbonate in tap water at a mass percent concentration of 50% to obtain solution B;

[0097] Step 3: Mix the mixed solution A and solution B in a volume ratio of 1:1, and stir them in a high-speed mixer for hydration for 10 hours at a stirring speed of 2000 r / min;

[0098] Step 4: Filter the mixed solution after stirring and hydrating in step 3 to obtain hydrated calcium carbonoaluminate cake, and dry the cake in an oven at a drying temperature of 100° C.;

[0099] Step 5: Grind the dried hydrated calcium aluminate with a ball mill to an average particle size of 200 meshes to obtain hydrated calcium aluminate early strength agent powder for concrete.

[0100] Blank group (no early strength agent was added to the concrete)

[0101] Comparative Example 1 (not within the volume ratio range defined in the present invention)

[0102] A method for preparing a hydrated calcium aluminate carbonate early strength agent for concrete comprises the following steps:

[0103] Step 1: Dissolve the cementitious material CA60 aluminate cement in tap water at a mass percentage concentration of 20%, and adjust the pH value of the mixed solution to 13±1 with a pH regulator sodium metaaluminate to obtain a mixed solution A;

[0104] Step 2: Dissolve sodium carbonate in tap water at a mass percent concentration of 20% to obtain solution B;

[0105] Step 3: Mix the mixed solution A and solution B at a volume ratio of 1:0.05, and stir them in a high-speed mixer for hydration for 6 hours at a stirring speed of 500 r / min;

[0106] Step 4: Filter the mixed solution after stirring and hydrating in step 3 to obtain hydrated calcium carbonoaluminate cake, and dry the cake in an oven at a drying temperature of 55°C;

[0107] Step 5: Grind the dried hydrated calcium aluminate with a ball mill to an average particle size of 1500 mesh to obtain hydrated calcium aluminate early strength agent powder for concrete.

[0108] Comparative Example 2 (not within the grinding particle size range defined in the present invention)

[0109] A method for preparing a hydrated calcium aluminate carbonate early strength agent for concrete comprises the following steps:

[0110] Step 1: Dissolve the cementitious material CA60 aluminate cement in tap water at a mass percentage concentration of 20%, and adjust the pH value of the mixed solution to 13±1 with a pH regulator sodium metaaluminate to obtain a mixed solution A;

[0111] Step 2: Dissolve sodium carbonate in tap water at a mass percent concentration of 20% to obtain solution B;

[0112] Step 3: Mix the mixed solution A and solution B at a volume ratio of 1:0.4, and stir them in a high-speed mixer for hydration for 6 hours at a stirring speed of 500 r / min;

[0113] Step 4: Filter the mixed solution after stirring and hydrating in step 3 to obtain hydrated calcium carbonoaluminate cake, and dry the cake in an oven at a drying temperature of 55°C;

[0114] Step 5: Grind the dried hydrated calcium aluminate with a ball mill to an average particle size of 50 meshes to obtain hydrated calcium aluminate early strength agent powder for concrete.

[0115] Figure 1 The XRD pattern of the hydrated calcium aluminate carbonate early strength agent powder prepared in Example 1-5; Figure 1 In the XRD diagram of the hydrated calcium aluminate early strength agent powder of each embodiment, obvious hydrated calcium aluminate phase can be seen, but due to the different proportions of the raw materials, a small amount of impurities such as calcium carbonate and calcium hydroxide are produced.

[0116] Figure 2 The particle size distribution diagram of the hydrated calcium aluminate early strength agent powder prepared in Examples 1-5; Figure 2 It can be seen that the average particle size of the hydrated calcium aluminate early strength agent powder prepared in each embodiment is: the average particle size of Example 1 is 5 μm, the average particle size of Example 2 is 9 μm, the average particle size of Example 3 is 14 μm, the average particle size of Example 4 is 33 μm, and the average particle size of Example 5 is 74 μm.

[0117] The early strength agent prepared in Examples 1-5 and Comparative Examples 1-2 was added to C40 concrete in an amount of 2% of the mass of the cementitious materials (cement and fly ash in Table 1) in the concrete. The mix ratio of C40 concrete is shown in Table 1. Wherein, G represents coarse aggregate, and the subscript represents the particle size range of coarse aggregate. The mechanical properties test was carried out in accordance with the Standard for Test Methods for Physical and Mechanical Properties of Concrete GB / T 50081-2019.

[0118] Table 1 C40 concrete mix proportion (kg / m 3 )

[0119]

[0120] Table 2 Compressive strength test data of concrete of different ages

[0121]

[0122] As shown in Table 2, compared with the blank group without early strength agent, Examples 1-5 have obvious early strength effect at 8h and 1d, and the compressive strength at 7d and 28d is also slightly improved compared with the blank group without early strength agent. The compressive strength of Comparative Examples 1-2 at each age is greater than that of the blank group, but significantly lower than that of the embodiment groups, and the early strength effect is weak.

[0123] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing a hydrated calcium aluminate carbonate early strength agent for concrete, characterized in that: The following steps are involved: The alkaline mixed solution containing the gelling material X and the carbonate solution are mixed, and then the mixture is stirred at high speed for hydration, filtered, dried and ground in sequence to prepare the hydrated calcium aluminate carbonate early strength agent; Wherein, the cementitious material X is aluminate cement; the volume ratio of the alkaline mixed solution containing the cementitious material X to the carbonate solution is 1: (0.2-1); the mass concentration of the carbonate solution is 10%-50%; The gelling material X includes one or more of CA50, CA60, CA70 and CA80; The mass percentage concentration of the alkaline mixed solution containing the gelling material X is 10%-50%; The pH of the alkaline mixed solution containing the gelling material X is 13±1; The grinding process is as follows: the dried product is ground to an average particle size of 200-2500 meshes.

2. The method for preparing a hydrated calcium aluminate carbonate early strength agent for concrete according to claim 1, characterized in that: The preparation process of the alkaline mixed solution containing the gelling material X is as follows: dissolving the gelling material X in water, adding a pH adjusting agent and mixing uniformly; The pH adjuster is a soluble alkaline substance.

3. The method for preparing a hydrated calcium aluminate carbonate early strength agent for concrete according to claim 1, characterized in that: The rotation speed during the high-speed stirring hydration process is 100-2000 r / min; the time of the high-speed stirring hydration is 5-10 hours.

4. A hydrated calcium aluminate carbonate early strength agent for concrete, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 3.

5. Use of the hydrated calcium aluminate carbonate early strength agent for concrete as claimed in claim 4 in improving the early strength of concrete.

6. The use of a hydrated calcium aluminate carbonate early strength agent for concrete according to claim 5 in improving the early strength of concrete, characterized in that: The solid content of the hydrated calcium aluminate carbon early strength agent is 1-5wt.% of the cementitious material Y; The cementitious material Y is the raw material in the concrete.

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