Method for carbon sequestration and reinforcement of recycled aggregate by using composite alkali solution and recycled aggregate

Abstract

The application relates to a method for carbon fixation and reinforcement of recycled aggregate by using a composite alkali solution and recycled aggregate, which comprises the following steps: soaking waste concrete recycled aggregate by using a composite alkali solution, the solute of the composite alkali solution comprising a first solute and a second solute for reaction to generate sodium hydroxide, wherein the first solute is a soluble alkali with hydroxyl, and the second solute is a soluble sodium salt; and then introducing carbon dioxide into the composite alkali solution to perform carbonization reaction, so as to obtain recycled aggregate. The application uses the composite alkali solution which is more operable and safer to stimulate the recycled aggregate to generate hydration products in the unhydrated clinker and mineral admixtures in the attached mortar, and uses carbon dioxide to make the hydration products and the residual alkali solution perform carbonization reaction to generate calcium carbonate to block pores and cracks, so that the performance of the recycled aggregate can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of industrial solid waste recycling, in particular to a method for carbon sequestration and reinforcement of recycled aggregate by using a composite alkali solution and recycled aggregate. BACKGROUND

[0002] With the continuous demolition of old buildings, a large amount of waste concrete is generated. The accumulation of these waste concretes not only occupies a large amount of land resources, but also pollutes the air and soil due to the fly ash generated by weathering and the alkaline leachate generated by rain. Reusing waste concrete by reshaping into recycled aggregate can reduce the exploitation of natural sand and gravel, solve the problem of environmental pollution, and achieve the reuse of resources. However, compared with natural aggregate, the main component of recycled aggregate is natural aggregate wrapped by attached mortar. The high porosity and micro-crack characteristics of recycled aggregate result in high water absorption, high crushing value, and high apparent density, which leads to low performance of concrete prepared by using recycled aggregate.

[0003] Currently, scholars at home and abroad mostly use methods such as crushing and shaping, thermal decomposition, solution immersion, and mortar wrapping to strengthen recycled aggregate, so as to achieve the purpose of stripping or reducing the porosity and water absorption of attached mortar of recycled aggregate.

[0004] The stripping effect of the crushing and shaping method is often poor. The attached mortar close to the internal natural aggregate is difficult to strip, and even secondary cracks may be generated during the crushing process.

[0005] The thermal decomposition method needs to calcine the recycled aggregate at high temperature, which greatly increases the energy consumption and carbon emissions.

[0006] The immersion method uses acid solution or strong alkali solution to treat recycled aggregate, but the effect is often limited. In high concentration, it may even reduce the strength of concrete and change the pH value of recycled aggregate, thereby affecting the performance of mortar or concrete.

[0007] The mortar wrapping method can effectively reduce the water absorption of recycled aggregate, such as using polymers, organic silicon waterproof agents, cement, etc. However, these materials have low strengthening effect on recycled aggregate, are easy to fall off, and most of them have the characteristics of high cost.

[0008] In some related technologies, sodium hydroxide solution is used to improve the quality of waste concrete recycled aggregate. However, sodium hydroxide solution has high alkalinity, which may cause alkali-aggregate reaction with silicon dioxide contained in the aggregate, resulting in concrete expansion and cracking. Therefore, it is only limited to the case where the original aggregate in the original waste concrete recycled aggregate is non-alkali active egg and gravel. Sodium hydroxide is a strong base, and the prepared solution is not easy to control and has corrosion danger, which has weak operability. In addition, the hydration products generated by alkali activation have negative characteristics such as volume instability, large shrinkage, and easy shrinkage of late mechanical properties.

[0009] In some related technologies, sodium carbonate solution is used to improve the quality of recycled aggregate of waste concrete. The sodium carbonate solution reacts with calcium hydroxide in the cement stone of waste concrete to form calcium carbonate, which blocks the pores and cracks of the cement stone. However, the calcium hydroxide in the cement stone of many construction wastes has been used for decades, and there is little calcium hydroxide to react with sodium carbonate. At the same time, sodium carbonate is a weak base, and its activation of unhydrated cement clinker and mineral admixtures in cement is weak.

[0010] In some related technologies, carbonation treatment is used to strengthen the performance of recycled aggregate. For example, calcium hydroxide solution is sprayed on recycled aggregate of long-age waste concrete to provide carbonizable substances, and carbonation curing is performed until the surface is completely carbonized to block the pores and cracks of the recycled aggregate. However, calcium hydroxide is a weak base, and its solution only provides carbonizable substances, and its activation of unhydrated clinker and mineral admixtures in the attached mortar of recycled aggregate is weak. SUMMARY

[0011] The embodiments of the present application provide a method for carbon sequestration and strengthening of recycled aggregate using a composite alkali solution, which uses a more operable and safer composite alkali solution to activate the unhydrated clinker and mineral admixtures in the attached mortar of recycled aggregate to generate hydration products, and uses carbon dioxide to make the hydration products and residual alkali solution carbonated to form calcium carbonate to block the pores and cracks, which can effectively improve the performance of recycled aggregate.

[0012] In a first aspect, a method for carbon sequestration and strengthening of recycled aggregate using a composite alkali solution is provided, which includes the following steps:

[0013] The waste concrete recycled aggregate is soaked in a composite alkali solution, and the solutes of the composite alkali solution include a first solute for reacting to generate sodium hydroxide and a second solute, wherein the first solute is a soluble base with hydroxyl ions, and the second solute is a soluble sodium salt.

[0014] Carbon dioxide is introduced into the composite alkali solution to perform carbonation reaction to obtain recycled aggregate.

[0015] In some embodiments, the first solute is calcium hydroxide.

[0016] In some embodiments, the second solute is one or more of sodium carbonate and sodium sulfate.

[0017] In some embodiments, the mass concentration of the composite alkali solution is 10% to 14%.

[0018] In some embodiments, the mass ratio of the first solute to the second solute is 10 to 30: 1 to 5.

[0019] In some embodiments, the waste concrete recycled aggregate is soaked in the composite alkali solution for 26-30 days.

[0020] In some embodiments, the carbon dioxide has a gas velocity of 0.2-0.4 L / min / 100 g of recycled aggregate.

[0021] In some embodiments, the carbon dioxide has a purity of no less than 99.9%.

[0022] In some embodiments, the carbonation reaction is stopped when the pH value of the composite alkali solution is 7.3-7.6.

[0023] In a second aspect, the application provides a recycled aggregate prepared by the method for carbon sequestration and performance enhancement of recycled aggregate using a composite alkali solution.

[0024] The technical scheme provided by the application has the following beneficial effects:

[0025] The application uses a composite alkali solution which is more operable and safer to excite the unhydrated clinker and mineral admixtures in the recycled aggregate to generate hydration products, and uses carbon dioxide to make the hydration products and residual alkali solution undergo carbonation reaction to generate calcium carbonate to plug pores and cracks, which can effectively improve the performance of the recycled aggregate.

[0026] The hydration products generated by alkali excitation have negative effects such as unstable volume change, large shrinkage, and inverted mechanical properties in later ages. The hydration products generated by the composite alkali solution of calcium hydroxide and sodium carbonate have smaller shrinkage than the hydration products generated by sodium hydroxide alone, but still show shrinkage, and the later performance is also unstable. However, since most of the calcium hydroxide is consumed in the alkali excitation hydration products, carbonation occurs easily, generating stable product calcium carbonate, and the generation of calcium carbonate is an expansion process that can effectively plug pores.

[0027] The hydration products generated by the composite alkali solution of calcium hydroxide and sodium sulfate excite unhydrated cement clinker and mineral admixtures to generate expansive product ettringite, which can effectively plug pores. However, ettringite is an unstable product that will be converted to monosulfate hydration product AFm when the sulfate ions in the system are insufficient, and will decompose when the temperature is higher than 70℃, which is not conducive to the stability of the performance of the recycled aggregate. Ettringite also carbonates easily, which can generate stable carbonation products, which is conducive to the stability of the performance of the recycled aggregate.

[0028] Compared with in air, carbonation of carbon dioxide in water can accelerate carbonation reaction, and make the alkali-activated hydration product in the pores and cracks of the recycled aggregate obtain a higher carbonation degree; at the same time, the calcium ions contained in the alkali solution in the pores and cracks of the recycled aggregate can also react with carbonate to form calcium carbonate to block the pores; and based on the "nucleation effect", the calcium carbonate generated in the alkali solution is also more likely to concentrate production with the calcium carbonate on the surface of the recycled aggregate as a crystal nucleus to form a dense calcium carbonate protective layer on the surface of the recycled aggregate, further making the surface of the recycled aggregate obtain a higher density.

[0029] By using the composite alkali solution to activate the unhydrated cement clinker and mineral admixtures in the waste concrete recycled aggregate, the alkali-activated hydration product is generated, after once blocking the pores and cracks, wet carbonation curing is carried out, the unstable alkali-activated hydration product is converted into stable calcium carbonate for secondary blocking, at the same time, the carbonate in the alkali solution can also generate a dense calcium carbonate protective film on the surface of the recycled aggregate due to the crystal nucleus effect, further increasing the density of the recycled aggregate.

[0030] It can be seen that, in the application, the composite alkali solution is used to activate the unhydrated cement clinker and mineral admixtures in the recycled aggregate, the reaction is more moderate than using sodium hydroxide alone, and more intense than using calcium hydroxide, sodium carbonate and sodium sulfate alone, which can reduce the operability and danger while ensuring the activation effect.

[0031] In the application, the generated unstable alkali-activated hydration product is converted into stable calcium carbonate for secondary blocking by using wet carbonation, which avoids the volume shrinkage, mechanical property deterioration and decomposition of the alkali-activated hydration product, and can improve the stability of the recycled aggregate performance; in addition, the residual uncarbonated alkali-activated hydration product can still provide strength for the recycled aggregate.

[0032] In the application, the recycled aggregate is neutralized by using wet carbonation, which avoids the influence of the residual alkaline substances on the performance of the concrete.

[0033] In the application, wet carbonation is used in a water environment, which can make the carbonation product more easily grow from the pores, cracks and interstices of the recycled aggregate, which is beneficial to the improvement of the density of the recycled aggregate. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced as follows, and obviously, the drawings in the following description are only some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0035] Figure 1A flowchart of a method for carbon fixation and reinforcement of recycled aggregate by using a composite alkali solution is provided in the embodiments of the present application. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0037] Reference Signs List Figure 1 As shown in the drawings, the embodiments of the present application provide a method for carbon fixation and reinforcement of recycled aggregate by using a composite alkali solution, which comprises the following steps:

[0038] 101: soaking waste concrete recycled aggregate in a composite alkali solution, a solute of the composite alkali solution comprising a first solute and a second solute for reaction to generate sodium hydroxide, wherein the first solute is a soluble alkali with hydroxyl ions, and the second solute is a soluble sodium salt;

[0039] 102: introducing carbon dioxide into the composite alkali solution to perform carbonization reaction, to obtain recycled aggregate.

[0040] The mechanism of the method provided in the present application is as follows:

[0041] The first solute and the second solute are compounded according to a certain mass ratio in the present application, so that the first solute and the second solute gradually react and generate sodium hydroxide in a water environment, and the reaction formula is as follows:

[0042] Na + +OH-→NaOH

[0043] After the gradually generated sodium hydroxide reacts with unhydrated cement clinker and mineral admixtures, the remaining calcium hydroxide can continue to participate in the reaction to ensure the late strength development. The negative effects caused by using sodium hydroxide solution alone, such as strong corrosion, unstable volume change of hydration products, large shrinkage, and late mechanical property reversal, can be avoided; and the defects of using calcium hydroxide, sodium carbonate or sodium sulfate solution alone, such as insufficient activation of unhydrated cement clinker and mineral admixtures, can also be avoided.

[0044] The hydration product generated by alkali activation has negative effects such as unstable volume change, large shrinkage, and reversed mechanical properties in later stage. Although the hydration product generated by calcium hydroxide and sodium carbonate composite alkali solution activation has smaller shrinkage than the hydration product generated by sodium hydroxide alone, it still shows shrinkage, and the later stage performance also has unstable characteristics. However, in the alkali-activated hydration product, most of the calcium hydroxide is consumed, and carbonation is prone to occur, generating stable product calcium carbonate. The generation of calcium carbonate is an expansion process, which can effectively block the pores.

[0045] In the hydration product generated by calcium hydroxide and sodium sulfate composite alkali solution activation of unhydrated cement clinker and mineral admixtures, the expansive product ettringite is generated, which can effectively block the pores. However, ettringite is an unstable product, which will be converted into monosulfate hydration product AFm when the sulfate ions in the system are insufficient, and will decompose when the temperature is higher than 70℃, which is not conducive to the stability of the performance of the recycled aggregate. Ettringite is also prone to carbonation, which can generate stable carbonation products, which is conducive to the stability of the performance of the recycled aggregate.

[0046] Compared with in air, the carbonation reaction is accelerated when carbon dioxide is dissolved in water, and the alkali-activated hydration product in the pores and cracks of the recycled aggregate can obtain a higher carbonation degree. At the same time, the calcium ions in the alkali solution contained in the pores and cracks of the recycled aggregate will also react with carbonate to generate calcium carbonate to block the pores. Moreover, based on the "nucleation effect", the calcium carbonate generated in the alkali solution is also more likely to concentrate production with the calcium carbonate on the surface of the recycled aggregate as the crystal nucleus, to form a dense calcium carbonate protective layer on the surface of the recycled aggregate, further increasing the density of the surface of the recycled aggregate.

[0047] By using composite alkali solution to activate the unhydrated cement clinker and mineral admixtures in the waste concrete recycled aggregate, alkali-activated hydration products are generated. After the pores and cracks are blocked once, wet carbonation curing is carried out to convert the unstable alkali-activated hydration products into stable calcium carbonate for secondary blocking. At the same time, the carbonate in the alkali solution will also generate a dense calcium carbonate protective film on the surface of the recycled aggregate due to the crystal nucleus effect, further increasing the density of the recycled aggregate.

[0048] It can be seen that the application uses composite alkali solution to activate the unhydrated cement clinker and mineral admixtures in the recycled aggregate. The reaction is more moderate than using sodium hydroxide alone, and more intense than using calcium hydroxide, sodium carbonate, and sodium sulfate alone. It can reduce the operability and danger while ensuring the activation effect.

[0049] The application uses wet carbonation to convert the generated unstable alkali-activated hydration products into stable calcium carbonate for secondary blocking, avoiding the volume shrinkage, mechanical property degradation, and decomposition of the alkali-activated hydration products, and can improve the stability of the performance of the recycled aggregate. In addition, the residual uncarbonated alkali-activated hydration products can still provide strength for the recycled aggregate.

[0050] The application utilizes wet carbonization to make the recycled aggregate neutral, avoiding the influence of the alkaline substances remaining on the recycled aggregate on the performance of the concrete.

[0051] The application utilizes wet carbonization in a water environment, which can make the carbonization products grow more easily from the pores, cracks and gaps of the alkaline hydration products of the recycled aggregate, and is beneficial to the improvement of the density of the recycled aggregate.

[0052] The application is beneficial to the dissolution of carbon dioxide in an alkaline solution environment, and can solidify higher concentration and higher volume of carbon dioxide in a unit time.

[0053] The first solute is calcium hydroxide.

[0054] The second solute is one or more of sodium carbonate and sodium sulfate.

[0055] The mass concentration of the composite alkali solution is 10% to 14%. When the concentration is higher than 14%, although the water absorption rate of the recycled aggregate can be significantly reduced, the apparent density is also reduced; when the concentration is lower than 10%, the water absorption rate of the recycled aggregate is large, and the apparent density is also low. Neither is conducive to the improvement of the performance of the recycled aggregate.

[0056] The mass ratio of the first solute to the second solute is 10 to 30: 1 to 5.

[0057] The soaking time of the waste concrete recycled aggregate in the composite alkali solution is 26 to 30 days.

[0058] The gas velocity of the carbon dioxide is 0.2 to 0.4 L / min / 100 g of recycled aggregate.

[0059] The purity of the carbon dioxide is not less than 99.9%.

[0060] When the carbonation reaction is to the pH value of the composite alkali solution is 7.3 to 7.6, stop the introduction of carbon dioxide to prevent excessive introduction of carbon dioxide to make the solution acidic, leading to the decomposition of the hydration product and the dissolution of calcium carbonate.

[0061] The carbonation component of the recycled aggregate is the hydration product generated by the unhydrated cement and mineral admixture excited by the composite alkali solution and the alkaline substances remaining in the solution.

[0062] The application also provides a recycled aggregate prepared by the method for solidifying carbon dioxide and strengthening recycled aggregate by using a composite alkali solution.

[0063] The application will be further described in connection with the following examples and comparative examples. It should be understood that the examples are only used to illustrate the application and not used to limit the scope of the application. Furthermore, it should be understood that after reading the content of the application, those skilled in the art can make various modifications or changes to the application, and these equivalent forms also fall within the scope defined by the appended claims of the application.

[0064] Example 1

[0065] The example includes the following steps:

[0066] (1) Composite alkali solution treatment: the recycled aggregate is soaked in a composite alkali solution of calcium hydroxide / sodium carbonate, the concentration of the composite alkali solution is 10%, the mass ratio of calcium hydroxide to sodium carbonate is 10:1, and the soaking time is 28 days.

[0067] (2) Wet carbonation treatment: carbonation reaction is carried out by introducing carbon dioxide with a concentration of 99.9% and a gas velocity of 0.2 L / min / 100 g of recycled aggregate into the composite alkali solution, and when the pH value of the solution is 7.3-7.6, the introduction of carbon dioxide is stopped, to obtain the recycled aggregate with carbon sequestration and reinforcement by the composite alkali activation solution.

[0068] Example 2

[0069] The example includes the following steps:

[0070] (1) Composite alkali solution treatment: the recycled aggregate is soaked in a composite alkali solution of calcium hydroxide / sodium carbonate, the concentration of the composite alkali solution is 10%, the mass ratio of calcium hydroxide to sodium carbonate is 10:3, and the soaking time is 28 days.

[0071] (2) Wet carbonation treatment: carbonation reaction is carried out by introducing carbon dioxide with a concentration of 99.9% and a gas velocity of 0.2 L / min / 100 g of recycled aggregate into the composite alkali solution, and when the pH value of the solution is 7.3-7.6, the introduction of carbon dioxide is stopped, to obtain the recycled aggregate with carbon sequestration and reinforcement by the composite alkali activation solution.

[0072] Example 3

[0073] The example includes the following steps:

[0074] (1) Composite alkali solution treatment: the recycled aggregate is soaked in a composite alkali solution of calcium hydroxide / sodium carbonate, the concentration of the composite alkali solution is 10%, the mass ratio of calcium hydroxide to sodium carbonate is 20:1, and the soaking time is 28 days.

[0075] (2) Wet carbonation treatment: carbonation reaction was carried out by bubbling carbon dioxide with a concentration of 99.9% and a gas velocity of 0.2 L / min / 100 g of recycled aggregate into the composite alkali solution, and the bubbling was stopped when the pH value of the solution was 7.3-7.6, to obtain the recycled aggregate carbonated and strengthened by the composite alkali solution.

[0076] Example 4

[0077] This example includes the following steps:

[0078] (1) Composite alkali solution treatment: the recycled aggregate was immersed in a calcium hydroxide / sodium carbonate composite alkali solution with a concentration of 10%, and the mass ratio of calcium hydroxide to sodium carbonate was 20:3, and the immersion time was 28 days.

[0079] (2) Wet carbonation treatment: carbonation reaction was carried out by bubbling carbon dioxide with a concentration of 99.9% and a gas velocity of 0.2 L / min / 100 g of recycled aggregate into the composite alkali solution, and the bubbling was stopped when the pH value of the solution was 7.3-7.6, to obtain the recycled aggregate carbonated and strengthened by the composite alkali solution.

[0080] Example 5

[0081] This example includes the following steps:

[0082] (1) Composite alkali solution treatment: the recycled aggregate was immersed in a calcium hydroxide / sodium carbonate composite alkali solution with a concentration of 10%, and the mass ratio of calcium hydroxide to sodium carbonate was 30:1, and the immersion time was 28 days.

[0083] (2) Wet carbonation treatment: carbonation reaction was carried out by bubbling carbon dioxide with a concentration of 99.9% and a gas velocity of 0.2 L / min / 100 g of recycled aggregate into the composite alkali solution, and the bubbling was stopped when the pH value of the solution was 7.3-7.6, to obtain the recycled aggregate carbonated and strengthened by the composite alkali solution.

[0084] Example 6

[0085] This example includes the following steps:

[0086] (1) Composite alkali solution treatment: the recycled aggregate was immersed in a calcium hydroxide / sodium carbonate composite alkali solution with a concentration of 10%, and the mass ratio of calcium hydroxide to sodium carbonate was 30:3, and the immersion time was 28 days.

[0087] (2) Wet carbonation treatment: carbonation reaction was carried out by bubbling carbon dioxide with a concentration of 99.9% and a gas velocity of 0.2 L / min / 100 g of recycled aggregate into the composite alkali solution, and the bubbling was stopped when the pH value of the solution was 7.3-7.6, to obtain the recycled aggregate carbonated and strengthened by the composite alkali solution.

[0088] Comparative Example 1

[0089] The present comparative example comprises the following steps:

[0090] The recycled aggregate is soaked with a sodium hydroxide solution with a mass concentration of 10%, and the soaking time is 28 days.

[0091] Comparative Example 2

[0092] The present comparative example comprises the following steps:

[0093] The recycled aggregate is soaked with a sodium carbonate solution with a mass concentration of 6%, and the soaking time is 28 days.

[0094] The samples of Examples 1-6 and Comparative Examples 1-2 are tested for water absorption and apparent density, and the test results are shown in Table 1 below.

[0095] Table 1 Water absorption, apparent density

[0096] Name Absorption / % Apparent density / (kg / m 3 )]]> Example 1 5.24 2350 Example 2 4.80 2355 Example 3 4.70 2376 Example 4 4.15 2390 Example 5 4.23 2400 Example 6 3.90 2430 Comparative Example 1 5.65 2335 Comparative Example 2 6.18 2215

[0097] In combination with Examples 1-6 and Comparative Example 1, it can be seen that, compared with sodium hydroxide, the hydration products generated by using a composite alkali solution to generate sodium hydroxide have a smaller shrinkage rate than the hydration products generated by sodium hydroxide alone, but still exhibit shrinkage, and have unstable properties in the later stage. However, since most of the calcium hydroxide in the alkali-activated hydration products is consumed, carbonation easily occurs, generating stable calcium carbonate, and the generation of calcium carbonate is an expansion process that can effectively block pores, so the water absorption is much lower than that of Comparative Example 1, and the apparent density is much higher than that of Comparative Example 1.

[0098] In combination with Examples 1-6 and Comparative Example 2, it can be seen that, compared with sodium carbonate, the use of a composite alkali solution to generate sodium hydroxide has a stronger excitation effect on unhydrated cement clinker and mineral admixtures in cement, which in turn excites the generation of hydration products from unhydrated clinker and mineral admixtures in the attached mortar of the recycled aggregate, and utilizes carbon dioxide to cause carbonation reaction between the hydration products and residual alkali solution to generate calcium carbonate to block pores and cracks, which can effectively improve the performance of the recycled aggregate, so the water absorption is much lower than that of Comparative Example 2, and the apparent density is much higher than that of Comparative Example 2.

[0099] In the description of the present application, it should be noted that the terms "upper", "lower", and the like are used for indicating the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. Unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be interpreted broadly, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0100] It should be noted that in the present application, relational terms such as "first" and "second", and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus including a series of elements includes not only those elements, but also other elements not explicitly listed, or other elements inherent in such a process, method, article or apparatus. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of other identical elements in the process, method, article or apparatus including the element.

[0101] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. A method for carbonation of recycled aggregates using a composite alkali solution, characterized by, It comprises the following steps: The waste concrete recycled aggregate is soaked by a composite alkali solution, solutes of the composite alkali solution include a first solute and a second solute for reacting to generate sodium hydroxide; Carbonation reaction is carried out by introducing carbon dioxide into the composite alkali solution to obtain the recycled aggregate The first solute is calcium hydroxide; The second solute is one or more of sodium carbonate and sodium sulfate; The mass ratio of the first solute to the second solute is 10-30:1-5.

2. The method for carbonation of reinforced recycled aggregates with composite alkali solution according to claim 1, characterized in that: The mass concentration of the composite alkali solution is 10%-14%.

3. The method for carbonation of reinforced recycled aggregates with composite alkali solution according to claim 1, characterized in that: The soaking time of the waste concrete recycled aggregate in the composite alkali solution is 26-30 days.

4. The method for carbonation of reinforced recycled aggregates with composite alkali solution according to claim 1, characterized in that: The gas speed of the carbon dioxide is 0.2-0.4 L / min / 100 g of the recycled aggregate.

5. The method for carbonation of reinforced recycled aggregates with composite alkali solution according to claim 1, characterized in that: The purity of the carbon dioxide is not less than 99.9%.

6. The method for carbonation of reinforced recycled aggregates with composite alkali solution according to claim 1, characterized in that: When the carbonation reaction is to the pH value of the composite alkali solution of 7.3-7.6, the introduction of the carbon dioxide is stopped.

7. A recycled aggregate, characterized by: It is prepared by the method for carbon fixation and reinforcement of recycled aggregate by using a composite alkali solution according to any one of claims 1 to 6.

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