Preparation method of sulfate and carbonized compound modified regenerated micro-powder, product and application of sulfate and carbonized compound modified regenerated micro-powder

Abstract

The invention provides a preparation method of sulfate and carbonized composite modified regenerated micro powder as well as a product and application thereof, and belongs to the technical field of building material solid waste recycling and reusing. The modified regenerated micro-powder is prepared by the following steps: crushing, screening and grinding waste concrete to obtain unmodified regenerated micro-powder, and soaking the unmodified regenerated micro-powder in a sulfate solution to obtain suspended matters; industrial carbon dioxide gas is introduced into the suspended matter, the carbonization reaction of the sulfate modified regenerated micro powder is promoted, and finally suction filtration and drying are performed to obtain the sulfate modified regenerated micro powder. On one hand, the carbon sequestration efficiency of the regenerated micro-powder is enhanced, and on the other hand, the activity of the regenerated micro-powder is improved, so that cement concrete prepared from the modified regenerated micro-powder instead of cement has excellent mechanical properties. The carbon dioxide curing efficiency of the regenerated micro-powder can be improved, the activity of the regenerated micro-powder is improved, the composite modified regenerated micro-powder can be used for producing cement concrete products, and the preparation method is simple and has wide industrial application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling and reusing solid waste of building materials, and in particular relates to a preparation method of sulfate and carbonization composite modified regenerated micropowder and its product and application. Background Art

[0002] In recent years, the demolition, collapse and reconstruction of a large number of buildings have generated a large amount of waste concrete, which not only causes a waste of resources, but also causes serious pollution to the environment. Recycled micropowder recycled from waste concrete can be used as an auxiliary cementitious material to replace cement, which can not only solve the problem of construction waste disposal, but also effectively reduce the amount of cement. The recycled micropowder obtained by crushing waste concrete has a complex composition, which makes the recycled micropowder low in activity and high in water absorption, resulting in a decrease in the working performance and mechanical properties of concrete. The direct replacement of recycled micropowder in cement concrete has the limitations of low activity and low utilization rate.

[0003] In order to broaden the application scope of recycled micropowder, it is particularly important to modify the recycled micropowder to improve its performance. There are four main methods for modifying recycled micropowder: physical activation, chemical activation, thermal activation, and carbonization modification. Accelerated carbonization of recycled micropowder is one of the effective ways to improve the sustainable development of concrete in the construction industry. Existing studies have shown that carbonization treatment can compact the pore structure of recycled micropowder. The carbonized recycled micropowder has significant volcanic ash activity and can be reused as a supplementary cementitious material. A single carbonization modification treatment method can improve the activity of recycled micropowder, but the existing carbonization efficiency of carbonized regenerated micropowder is not high, and its application technology in cement concrete is still in its infancy. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a preparation method of sulfate and carbonization composite modified regenerated micropowder and its product and application, and utilizes chemical modification and carbonization to synergistically treat waste concrete to improve the quality of regenerated micropowder, so that it can not only improve the activity of regenerated micropowder, but also achieve the effect of improving carbon fixation, which is beneficial to the recycling of waste concrete and reduces the amount of cement used.

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

[0006] One of the technical solutions of the present invention:

[0007] A method for preparing sulfate and carbonization composite modified regenerated micropowder comprises the following steps: crushing, screening and grinding waste concrete to obtain unactivated regenerated micropowder, and the unactivated regenerated micropowder is soaked and dispersed in a sulfate solution to obtain a suspended substance; industrial carbon dioxide gas is introduced into the suspended substance and stirred to induce wet carbonization of the unactivated regenerated micropowder, and after the wet carbonization reaction is completed, the composite modified regenerated micropowder is obtained by suction filtration and drying.

[0008] Furthermore, the waste concrete is crushed and sieved to select particles with a size less than 0.15 mm.

[0009] Furthermore, the concentration of the regenerated micropowder in the suspension is 80-200 g / L, the concentration of the sulfate solution is 0.1-0.5 mol / L, and the soaking time is 0.5-2 h.

[0010] Furthermore, the wet carbonization treatment is to introduce industrial carbon dioxide into the regenerated micropowder soaked in sulfate solution and stir it, and the time of the wet carbonization treatment is 2-4 hours.

[0011] Furthermore, the wet carbonization treatment is carried out in an industrial CO2 atmosphere with a concentration of 20-99%.

[0012] The second technical solution of the present invention:

[0013] A sulfate and carbonization composite modified regenerated micro powder is prepared according to the preparation method.

[0014] The third technical solution of the present invention:

[0015] The application of the sulfate and carbonization composite modified regenerated micro powder in the preparation of concrete.

[0016] The sulfate and carbonization composite modified regenerated micropowder contains a certain amount of unhydrated cement particles and calcium hydroxide, and these components have the ability to continue to hydrate to form a gel product.

[0017] Furthermore, the sulfate and carbonized composite modified regenerated micropowder is used as a mineral admixture in a cement concrete system to replace part of the cement.

[0018] Furthermore, the replacement rate of the sulfate and carbonization composite modified recycled micro powder for cement is 10-30%.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects:

[0020] (1) The present invention uses a composite modification method to treat the regenerated micropowder. The regenerated micropowder is first soaked in a sulfate solution. The sulfate, as an activator, can react with the hydroxide in the regenerated micropowder to generate new hydration products, such as calcium sulfate and calcium vanadium. These products help to improve the activity of the regenerated micropowder. Then, through wet carbonization, the hydration products of Ca(OH)2 and CSH react with CO2 to obtain calcium carbonate and amorphous silica-alumina gel, which further improves the activity of the regenerated micropowder. The carbonization product fills the pores of the regenerated micropowder, reduces its water absorption rate, strengthens the physical properties of the regenerated micropowder, and significantly improves its microstructure. At the same time, it can also react with cement hydration products to exert a volcanic ash effect and significantly improve the early mechanical properties of cement. It can be used to prepare cement concrete, reduce the amount of cement used, and is beneficial to energy conservation and environmental protection and improves the compressive strength of cement concrete.

[0021] (2) The active regenerated micropowder prepared by the present invention has improved utilization value and is suitable for preparing concrete as an auxiliary cementitious material, thereby solving the waste of discarded concrete and environmental protection problems and reducing costs. In addition, the preparation method is simple and is suitable for industrial production. DETAILED DESCRIPTION

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0027] The embodiment of the present invention proposes a method for preparing sulfate and carbonization composite modified regenerated micropowder, wherein waste concrete is crushed, screened and ground to obtain unactivated regenerated micropowder, and the unactivated regenerated micropowder is soaked in a sulfate solution and wet carbonized to obtain the sulfate and carbonization composite modified regenerated micropowder.

[0028] In a preferred embodiment of the present invention, the waste concrete is crushed and sieved to select particles with a size less than 0.15 mm.

[0029] In a preferred embodiment of the present invention, the concentration of the regenerated micro powder in the suspension is 80-200 g / L, the concentration of the sulfate solution is 0.1-0.5 mol / L, preferably 0.2 mol / L, the soaking time is 0.5-2 h, preferably 1 h. The sulfate includes at least one of a CaSO4 solution and a Na2SO4 solution.

[0030] In a preferred embodiment of the present invention, the wet carbonization treatment is to introduce industrial carbon dioxide gas into the mixture after soaking in sulfate solution for stirring and carbonization. The time of the wet carbonization treatment is 2-4 hours, preferably 4 hours.

[0031] In a preferred embodiment of the present invention, the CO2 concentration of the wet carbonization treatment is 20-99%, preferably the CO2 concentration is 40-99%.

[0032] The embodiment of the present invention also provides a sulfate and carbonization composite modified regenerated micropowder, which is prepared according to the preparation method.

[0033] The embodiment of the present invention also proposes the use of the sulfate and carbonization composite modified regenerated micro powder in the preparation of concrete.

[0034] In a preferred embodiment of the present invention, the sulfate and carbonized composite modified regenerated micropowder is used as a mineral admixture in a cement concrete system to replace part of the cement.

[0035] In a preferred embodiment of the present invention, the replacement rate of the sulfate and carbonization composite modified recycled micro powder for cement is 10-30%, preferably 10-20%.

[0036] All raw materials used in the examples of the present invention are commercially available.

[0037] The technical solution of the present invention is further illustrated by the following embodiments.

[0038] Example 1

[0039] A method for preparing sulfate and carbonization composite modified regenerated micropowder comprises the following steps:

[0040] (1) crushing and sieving the waste concrete, and then passing it through a 0.15 mm sieve to obtain unactivated recycled micro powder;

[0041] (2) taking the unactivated regenerated micropowder in step (1) and immersing and dispersing it in a 0.1 mol / L CaSO4 solution for 1 h to obtain a solid-liquid mixture A (a suspension in which the concentration of the regenerated micropowder in the suspension is 80 g / L);

[0042] (3) The solid-liquid mixture A obtained in step (2) is introduced into industrial CO2 gas with a concentration of 20% and stirred for 2 hours to obtain a solid mixture B, which is then filtered and dried to obtain sulfate and carbonized composite modified regenerated micropowder for subsequent use as a substitute for cement mineral admixtures.

[0043] Example 2

[0044] Compared with Example 1, the only difference is that the concentration of regenerated micro powder in the suspension is 200 g / L.

[0045] Example 3

[0046] Compared with Example 1, the only difference is that the concentration of the CaSO4 solution is 0.5 mol / L.

[0047] Example 4

[0048] Compared with Example 1, the only difference is that the unactivated regenerated micropowder is immersed and dispersed in a 0.1 mol / L CaSO4 solution for 0.5 h.

[0049] Example 5

[0050] Compared with Example 1, the only difference is that the unactivated regenerated micropowder is immersed and dispersed in a 0.1 mol / L CaSO4 solution for 2 h.

[0051] Example 6

[0052] Compared with Example 1, the only difference is that industrial CO2 gas with a concentration of 40% is introduced into the solid-liquid mixture A obtained in step (2).

[0053] Example 7

[0054] Compared with Example 1, the only difference is that industrial CO2 gas with a concentration of 99% is introduced into the solid-liquid mixture A obtained in step (2).

[0055] Example 8

[0056] Compared with Example 1, the only difference is that the unactivated regenerated micropowder in step (1) is soaked and dispersed in a 0.2 mol / L Na2SO4 solution;

[0057] The solid-liquid mixture A obtained in step (2) is introduced with industrial CO2 gas having a concentration of 99%;

[0058] The remaining steps are the same as in Example 1.

[0059] Comparative Example 1

[0060] Unactivated regenerated micropowder (prepared according to step (1) of Example 1).

[0061] Comparative Example 2

[0062] The preparation method of CaSO4 modified regenerated micro powder comprises the following steps:

[0063] (1) crushing and sieving the waste concrete, and then passing it through a 0.15 mm sieve to obtain unactivated recycled micro powder;

[0064] (2) taking the unactivated regenerated micropowder in step (1) and immersing and dispersing it in a 0.1 mol / L CaSO4 solution for 1 h to obtain a solid-liquid mixture A (a suspension in which the concentration of the regenerated micropowder in the suspension is 80 g / L);

[0065] (3) The solid-liquid mixture A obtained in step (2) is filtered and dried to obtain CaSO4 modified regenerated micropowder, which is used as a subsequent substitute for cement mineral admixture.

[0066] Comparative Example 3

[0067] The preparation method of Na2SO4 modified regenerated micro powder comprises the following steps:

[0068] (1) crushing and sieving the waste concrete, and then passing it through a 0.15 mm sieve to obtain unactivated recycled micro powder;

[0069] (2) taking the unactivated regenerated micropowder in step (1) and immersing and dispersing it in a 0.1 mol / L Na2SO4 solution for 1 h to obtain a solid-liquid mixture A (a suspension in which the concentration of the regenerated micropowder in the suspension is 80 g / L);

[0070] (3) The solid-liquid mixture A obtained in step (2) is filtered and dried to obtain Na2SO4 modified regenerated micropowder, which is used as a subsequent substitute for cement mineral admixture.

[0071] Comparative Example 4

[0072] The preparation method of 20% concentration carbon dioxide modified regenerated micro powder comprises the following steps:

[0073] (1) crushing and sieving the waste concrete, and then passing it through a 0.15 mm sieve to obtain unactivated recycled micro powder;

[0074] (2) The unactivated regenerated micropowder obtained in step (1) is introduced into industrial CO2 gas with a concentration of 20% and stirred for 2 hours to obtain a solid mixture, which is then filtered and dried to obtain 20% concentration carbon dioxide modified regenerated micropowder for subsequent use as a substitute for cement mineral admixtures.

[0075] Comparative Example 5

[0076] The preparation method of 99% concentration carbon dioxide modified regenerated micro powder comprises the following steps:

[0077] (1) crushing and sieving the waste concrete, and then passing it through a 0.15 mm sieve to obtain unactivated recycled micro powder;

[0078] (2) The unactivated regenerated micropowder obtained in step (1) is introduced into industrial CO2 gas with a concentration of 20% and stirred for 2 hours to obtain a solid mixture, which is then filtered and dried to obtain 99% carbon dioxide-modified regenerated micropowder for subsequent use as a substitute for cement mineral admixtures.

[0079] Performance Testing

[0080] The recycled fine powder prepared in Examples 1-8 and Comparative Examples 1-5 was used to replace cement at a replacement rate of 30%, and 315 g of P·O42.5 cement, 135 g of recycled fine powder, 1350 g of ISO standard sand, and 225 g of water were mixed to prepare concrete. A control group was set up in which no recycled fine powder was added, and 450 g of P·O42.5 cement, 1350 g of ISO standard sand, and 225 g of water were mixed to prepare cement mortar.

[0081] The activity index of recycled micropowder is an important indicator to measure its activity as a mineral admixture in cement-based materials. It reflects the contribution of recycled micropowder to the strength of concrete after replacing cement. The expansion of recycled micropowder mortar replacing 30% of cement clinker is used to characterize its water requirement. With reference to the standards JG / T 573-2020 "Recycled Micropowder for Concrete and Mortar" and GB / T 2419-2005 "Test Method for Fluidity of Cement Mortar", the above concrete samples were tested for 7d compressive strength, 28d compressive strength, specific surface area, mortar expansion and recycled micropowder activity index. The test results of sample performance are shown in Tables 1 and 2.

[0082] Table 1 Test results of bonding performance of recycled micropowder

[0083]

[0084]

[0085] Table 2 Recycled micro powder activity index and concrete strength test

[0086] Group 7d compressive strength / MPa 28d compressive strength / MPa Regeneration micro powder activity / % Control group 38.4 50.9 / Example 1 33.1 43.4 71 Example 2 36.6 47.3 78 Example 3 34.3 45.8 74 Example 4 36.7 48.1 82 Example 5 34.2 44.9 73 Example 6 38.1 48.3 80 Example 7 36.2 45.8 76 Example 8 38.3 48.8 85 Comparative Example 1 22.4 28.9 57 Comparative Example 2 25.8 31.7 63 Comparative Example 3 26.2 32.7 64 Comparative Example 4 25.1 31.2 63 Comparative Example 5 26.8 33.3 65

[0087] The test results show that the specific surface area of ​​the regenerated micropowder prepared in the embodiment of the present invention is 360-387m 2 / kg, the expansion of the prepared mortar sample is 168-186mm, the 7d compressive strength is 33.1-38.3MPa, the 28d compressive strength is 43.4-48.8MPa, and the activity of the regenerated micropowder is 71-85%. This is because sulfate is an important component of cement, and sulfate ions exist in the regenerated micropowder. At this time, part of the calcium in the regenerated micropowder is precipitated in the form of calcium sulfate, and carbonization causes the hydration product of the regenerated micropowder to form calcium carbonate precipitation. The size of the carbonized product is relatively regular, which effectively fills the pores in the micropowder, improves its fineness, and thus increases its specific surface area. The higher the expansion of the concrete mortar, the less water it requires. It can be seen that with the increase of sulfate solution concentration, the compressive strength of concrete mortar samples prepared by sulfate and carbonization composite modified regenerated micropowder at 7d and 28d showed a trend of first increasing and then decreasing. At the same time, the activity index of regenerated micropowder also decreased with the decrease of strength, indicating that with the addition of sulfate solution, the calcium ions of regenerated micropowder dissolved in the solution rich in carbon dioxide and sulfate will generate calcium sulfate and calcium carbonate to fill the pores and improve the microstructure. However, continuing to increase the concentration of sulfate solution will reduce the amount of hydration product Ca(OH)2, resulting in a decrease in strength.

[0088] According to Comparative Examples 1-5, it can be seen that the mortar prepared by using sulfate and carbonization composite modified regenerated micropowder in the embodiment has a higher compressive strength than the mortar prepared by unmodified and single modified regenerated micropowder. This is because the calcium sulfate and calcium carbonate generated by sulfate and carbonization composite modification fill the pores to further reduce the porosity and improve the compactness. The untreated regenerated micropowder in Comparative Example 1 has higher porosity and water absorption, thereby reducing its density and strength. Comparative Examples 2-3 use carbonization treatment. As the carbonization time increases, the carbonization reaction of the hydration product and carbon dioxide is more sufficient, so that more Ca(OH)2 is converted into CaCO3. Comparative Examples 4-5 are treated with different sulfate solutions. Sulfate ions promote the reaction of cement clinker minerals with water and accelerate the hydration process, thereby improving the activity of the regenerated micropowder. It is explained that the regenerated micropowder modified by sulfate and carbonization composite can solve the problem of low activity and strength of the regenerated micropowder.

[0089] 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 sulfate and carbonization composite modified regenerated micropowder, characterized in that: The following steps are involved: The waste concrete is crushed, sieved and ground to obtain unactivated regenerated micropowder, and the unactivated regenerated micropowder is dispersed by soaking in a sulfate solution to obtain a suspension; carbon dioxide gas is introduced into the suspension and stirred to induce sufficient wet carbonization of the unactivated regenerated micropowder, and after the wet carbonization reaction is completed, the composite modified regenerated micropowder is obtained by filtration and drying.

2. The method for preparing sulfate and carbonization composite modified regenerated micropowder according to claim 1, characterized in that: The particle size of the unactivated regenerated micro powder is less than 0.15 mm.

3. The method for preparing sulfate and carbonization composite modified regenerated micropowder according to claim 1, characterized in that: The concentration of the regenerated micro powder in the suspension is 80-200 g / L, the concentration of the sulfate solution is 0.1-0.5 mol / L, and the soaking time is 0.5-2 h.

4. The method for preparing sulfate and carbonization composite modified regenerated micropowder according to claim 1, characterized in that: The wet carbonization reaction time is 2-4 hours.

5. The method for preparing sulfate and carbonization composite modified regenerated micropowder according to claim 4, characterized in that: The wet carbonization reaction is carried out in a CO2 atmosphere with a concentration of 20-99%.

6. The method for preparing sulfate and carbonization composite modified regenerated micropowder according to claim 1, characterized in that: The waste concrete grinding process requires the addition of abrasives, and the abrasive is triisopropanolamine.

7. A sulfate and carbonization composite modified regenerated micro powder, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 6.

8. Use of the sulfate and carbonization composite modified regenerated micropowder as claimed in claim 7 in preparing concrete.

9. The use according to claim 8, characterized in that The sulfate and carbonized composite modified regenerated micro powder is used as a mineral admixture in a cement concrete system to replace part of the cement.

10. The use according to claim 9, characterized in that The replacement rate of the sulfate and carbonization composite modified recycled micro powder for cement is 10-30%.

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