Carbonation resistant concrete and method of making same

Abstract

The application discloses an anti-carbonization concrete and a preparation method thereof, and relates to the field of concrete, which is prepared from the following components by weight: modified coarse aggregate 100-200 parts; fine aggregate 50-90 parts; Portland cement 60-80 parts; water 15-24 parts; water reducing agent 2-4 parts; and coated expansive agent 6-9 parts; and the preparation method of the coated expansive agent is as follows: polyethylene imine, ethanol and expansive agent are mixed and ball milled to obtain the coated expansive agent. The application has the effect of improving the compressive strength and carbonization resistance of the concrete.

Description

Technical Field

[0001] This application relates to the field of concrete, and in particular to a carbonation-resistant concrete and a method for preparing the same. Background Technology

[0002] Carbonation of concrete is a type of chemical corrosion that occurs in concrete. The main cause is that carbon dioxide gas in the air penetrates into the concrete and reacts chemically with alkaline substances in the concrete, leading to a reduction in alkaline substances. When carbonation exceeds the concrete's protective layer, the concrete will lose its protective function for the reinforcing steel under the influence of water and air.

[0003] Currently, because concrete cracking is caused by the concentration of internal stress due to its own shrinkage, which accelerates the carbonation rate of concrete, an expansive agent is often added to the concrete. The micro-expansion of the expansive agent balances the expansion stress generated inside the concrete, reduces the cracking phenomenon, and thus improves the carbonation resistance of the concrete.

[0004] However, because concrete has low strength in the early stages of hardening, the expansion agent will enlarge the pore structure of the concrete while expanding, resulting in low concrete density. After the concrete solidifies, carbon dioxide can easily penetrate into the interior of the concrete through the enlarged pore structure, resulting in limited improvement in the concrete's resistance to carbonation. Summary of the Invention

[0005] To address the problem of poor carbonation resistance caused by low density in concrete after the addition of an expansion agent, this application provides carbonation-resistant concrete and its preparation method.

[0006] On the one hand, the carbonation-resistant concrete provided in this application adopts the following technical solution:

[0007] A carbonation-resistant concrete is prepared from components comprising the following parts by weight:

[0008] 100-200 parts of modified coarse aggregate;

[0009] 50-90 parts fine aggregate;

[0010] 60-80 parts of silicate cement;

[0011] 15-24 parts water;

[0012] 2-4 parts water-reducing agent;

[0013] 6-9 parts of coating expander;

[0014] The preparation method of the coating swelling agent is as follows:

[0015] Polyethyleneimine, ethanol, and an expanding agent are mixed and ball-milled to obtain a coating expanding agent.

[0016] By adopting the above technical solution, using silicate cement, modified coarse aggregate, and fine aggregate as the main components of concrete, and using water-reducing agents to reduce the amount of mixing water, the silicate cement hydrates during concrete setting, bonding and initially shaping the modified coarse and fine aggregates. At this time, the polyethyleneimine in the coating expansion agent forms a protective film on the surface of the expansion agent particles, delaying the expansion of the expansion agent and reducing the cracking rate. Simultaneously, the heat generated by the hydration of silicate cement raises the internal temperature of the concrete, and the polyethyleneimine gradually dissolves within the concrete. As the concrete sets, the rigid skeleton formed by the modified coarse aggregate, fine aggregate, and silicate cement gradually hardens. At this time, the expansion agent begins to expand under the constraint of the rigid skeleton, thereby filling the gaps in the rigid skeleton, improving the density of the concrete, and minimizing the entry of carbon dioxide from the air into the concrete through the pore structure. Under the combined effect, the concrete's resistance to carbonation and compressive strength are improved.

[0017] Preferably, the weight ratio of the expanding agent to the polyethyleneimine is (7.5-15):1.

[0018] Preferably, in the coating expander, the number average molecular weight of the polyethyleneimine is 3500-10000.

[0019] Preferably, the mixing includes: first premixing polyethyleneimine and ethanol to obtain a premix, and then mixing the premix with an expanding agent, wherein the expanding agent includes calcium sulfoaluminate.

[0020] By adopting the above technical solution and controlling the ratio of polyethyleneimine to the expanding agent and the number-average molecular weight of polyethyleneimine, a water-soluble layer of polyethyleneimine is formed on the surface of calcium sulfoaluminate, which delays the expansion of calcium sulfoaluminate and reduces the cracking rate. During concrete solidification, the polyethyleneimine on the surface of calcium sulfoaluminate gradually dissolves, and as the heat generated during concrete solidification increases, the internal temperature of the large-volume concrete rises, gradually accelerating the dissolution rate of polyethyleneimine. During rigid skeleton forming, calcium sulfoaluminate expands under the constraint of the rigid skeleton, improving the density of the concrete. Furthermore, the premixing of polyethyleneimine with ethanol improves the uniformity of polyethyleneimine coverage on the surface of calcium sulfoaluminate. Under the combined effect, the carbonation resistance and compressive strength of the concrete are improved.

[0021] Optionally, the modified coarse aggregate is prepared as follows:

[0022] A1. Mix the adhesive and silane coupling agent to obtain the adhesive;

[0023] A2. Soak the coarse aggregate in the binder and then take it out to obtain modified coarse aggregate.

[0024] Preferably, the adhesive is selected from one or both of polyvinyl alcohol aqueous solution and water glass.

[0025] Preferably, the adhesive is an aqueous solution of polyvinyl alcohol.

[0026] Preferably, the polyvinyl alcohol in the aqueous solution has a mass fraction of 6%-10%.

[0027] Preferably, the volume weight ratio of the adhesive to the silane coupling agent is (2.5-3)L:1kg.

[0028] Preferably, the weight ratio of the coating expansion agent to the modified coarse aggregate is (0.035-0.07):1.

[0029] Preferably, the weight ratio of the coating expansion agent to the modified coarse aggregate is (0.04-0.06):1.

[0030] By adopting the above technical solution, the early strength of the rigid skeleton formed by coarse aggregate, fine aggregate, and silicate cement is improved through the use of adhesives. Furthermore, by controlling the addition ratio of adhesive to silane coupling agent and the weight ratio of coating expansion agent to modified coarse aggregate, the rigid skeleton is further improved by cross-linking polyvinyl alcohol and dissolved polyethyleneimine under the action of silane coupling agent during expansion of the expansion agent. This further enhances the filling and bonding effect of the expansion agent on the gaps in the rigid skeleton. In addition, the polyethyleneimine cross-linked with the rigid skeleton can also adsorb carbon dioxide entering the concrete, inhibiting the penetration of carbon dioxide into the concrete. Under the combined effect, the carbonation resistance and compressive strength of the concrete are further improved.

[0031] On the other hand, this application also provides a method for preparing carbonation-resistant concrete, which adopts the following technical solution:

[0032] A method for preparing carbonation-resistant concrete includes the following steps:

[0033] S1. Mix the coating expansion agent, silicate cement, modified coarse aggregate and fine sand to obtain the structural material;

[0034] S2. Mix the structural material, water-reducing agent and water evenly to obtain carbonation-resistant concrete.

[0035] Preferably, step S1 includes the following steps:

[0036] S11. Mix the coating expansion agent and modified coarse aggregate to obtain a premix;

[0037] S12. Mix silicate cement, fine sand and premixed material evenly to obtain structural material.

[0038] By adopting the above technical solution, the premixing of the coating expansion agent and the modified coarse aggregate improves the dispersion effect of the two in concrete. At the same time, it facilitates the contact between the polyethyleneimine in the coating expansion agent and the modified coarse aggregate when dissolved. Under the combined action of silicate cement, fine sand, water and water-reducing agent, the carbonation resistance and compressive strength of concrete are improved.

[0039] In summary, this application includes at least one of the following beneficial technical effects:

[0040] 1. Using silicate cement, modified coarse aggregate, and fine aggregate as the main components of concrete, and using water-reducing agents to reduce the amount of mixing water, the silicate cement hydrates during concrete setting, bonding and initially shaping the modified coarse and fine aggregates. At this time, the polyethyleneimine in the coating expansion agent forms a protective film on the surface of the expansion agent particles, delaying the expansion of the expansion agent and reducing the cracking rate. The polyethyleneimine gradually dissolves in the concrete. As the concrete sets, the rigid skeleton formed by the modified coarse aggregate, fine aggregate, and silicate cement gradually hardens. At this time, the expansion agent begins to expand under the constraint of the rigid skeleton, thereby filling the gaps in the rigid skeleton and improving the density of the concrete. Under the combined effect, the concrete's resistance to carbonation and compressive strength are improved.

[0041] 2. Premixing polyethyleneimine with ethanol improves the uniformity of polyethyleneimine coverage on the calcium sulfoaluminate surface;

[0042] 3. The adhesive improves the early strength of the rigid skeleton formed by coarse aggregate, fine aggregate, and silicate cement. Furthermore, by controlling the addition ratio of adhesive to silane coupling agent and the weight ratio of coating expansion agent to modified coarse aggregate, the rigid skeleton and dissolved polyethyleneimine cross-link under the action of silane coupling agent during expansion of the expansion agent, further improving the filling and bonding effect of the expansion agent on the gaps in the rigid skeleton. In addition, the polyethyleneimine cross-linked with the rigid skeleton can also adsorb carbon dioxide entering the concrete, inhibiting the penetration of carbon dioxide into the concrete. Under the combined effect, the carbonation resistance and compressive strength of the concrete are further improved. Attached Figure Description

[0043] Figure 1 This is a flowchart of the preparation method of carbonation-resistant concrete in this application;

[0044] Figure 2 yes Figure 1 The flowchart for step S1. Detailed Implementation

[0045] The present application will be further described in detail below with reference to the embodiments. The following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the following embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the methods used are conventional methods known in the art, and the consumables and reagents used are commercially available. Unless otherwise stated, the technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be applied to the present invention.

[0046] All raw materials used in the examples are commercially available. The coarse aggregate is limestone aggregate, the fine aggregate is fine sand, the expansion agent is calcium sulfoaluminate, and the water-reducing agent is polycarboxylate water-reducing agent.

[0047] Examples 1-7

[0048] Examples 1-7 provide a carbonation-resistant concrete and its preparation method, the composition and proportions of which are shown in Table 1.

[0049] The preparation methods of the modified coarse aggregate in Examples 1-7 are as follows:

[0050] A1. Solution preparation: Add 3 kg of silane coupling agent to 8 L of 8% polyvinyl alcohol aqueous solution, and stir and mix evenly at 60°C to obtain the adhesive.

[0051] A2. Modification: After cleaning the surface of the coarse aggregate, soak it in the adhesive for 6 hours and then take it out to obtain modified coarse aggregate.

[0052] The preparation methods of the coating swelling agent in Examples 1-7 are as follows:

[0053] B1. Mixing: Mix 2 parts by weight of polyethyleneimine, 1 part by weight of ethanol and 20 parts by weight of calcium sulfoaluminate to obtain a mixture.

[0054] B2. Ball milling: Add the mixture to a ball mill and mill it evenly to obtain the coating expansion agent.

[0055] The preparation methods of carbonation-resistant concrete in Examples 1-7 are as follows:

[0056] S1. Ingredients: Add the coating expansion agent, silicate cement, modified coarse aggregate and fine sand to the concrete mixer and mix to obtain the structural material;

[0057] S2. Mixing: Weigh out the water-reducing agent and water, mix the water-reducing agent and water evenly, add them to the concrete mixer, and continue mixing to obtain carbonation-resistant concrete.

[0058] In Examples 1-7, the degree of polymerization of polyvinyl alcohol used to prepare modified coarse aggregate was 1700 and the degree of alcoholysis was 88%; the number average molecular weight of polyethyleneimine used to prepare coating expansion agent was 3500.

[0059] Table 1: Composition and mix proportions of carbonation-resistant concrete

[0060]

[0061]

[0062] Example 8

[0063] Example 8 provides a carbonation-resistant concrete and its preparation method. The difference between Example 8 and Example 2 is that water glass is used instead of the polyvinyl alcohol aqueous solution when preparing the modified coarse aggregate.

[0064] Example 9

[0065] Example 9 provides an anti-carbonation concrete and its preparation method. The difference between Example 9 and Example 2 lies in the preparation method of the coating expansion agent. The preparation method of the coating expansion agent in Example 9 is as follows:

[0066] B1. Mixing: Mix 4 parts by weight of polyethyleneimine, 1.5 parts by weight of ethanol and 30 parts by weight of calcium sulfoaluminate to obtain a mixture.

[0067] B2. Ball milling: Add the mixture to a ball mill and mill it evenly to obtain the coating expansion agent.

[0068] Example 10

[0069] Example 10 provides a carbonation-resistant concrete and its preparation method. The difference between Example 10 and Example 2 lies in the preparation method of the coating expansion agent. The preparation method of the coating expansion agent in Example 10 is as follows:

[0070] B1. Mixing: Mix 1 part by weight of polyethyleneimine, 0.6 parts by weight of ethanol and 15 parts by weight of calcium sulfoaluminate to obtain a mixture.

[0071] B2. Ball milling: Add the mixture to a ball mill and mill it evenly to obtain the coating expansion agent.

[0072] Example 11

[0073] Example 11 provides a carbonation-resistant concrete and its preparation method. The difference between Example 11 and Example 2 is that the number average molecular weight of polyethyleneimine in Example 11 is 5000.

[0074] Example 12

[0075] Example 12 provides a carbonation-resistant concrete and its preparation method. The difference between Example 12 and Example 2 is that the number average molecular weight of polyethyleneimine in Example 12 is 10,000.

[0076] Example 13

[0077] Example 13 provides an anti-carbonation concrete and its preparation method. The difference between Example 13 and Example 11 is that in Example 13, during the preparation of the coating expansion agent, step S1 includes the following steps:

[0078] B11. Premix: Add 2 parts by weight of polyethyleneimine and 1 part by weight of ethanol to a mixing tank and stir until homogeneous to obtain a premix. B12. Compound Mix: Add 20 parts by weight of calcium sulfoaluminate to the premix in the mixing tank and stir until homogeneous to obtain a compound.

[0079] Example 14

[0080] Example 14 provides a carbonation-resistant concrete and its preparation method. The difference between Example 14 and Example 13 lies in the preparation method of the modified coarse aggregate. The preparation method of the modified coarse aggregate in Example 14 is as follows:

[0081] A1. Solution preparation: Add 2 kg of silane coupling agent to 6 L of 8% polyvinyl alcohol aqueous solution and stir and mix evenly at 60°C to obtain the adhesive.

[0082] A2. Modification: After cleaning the surface of the coarse aggregate, soak it in the adhesive for 6 hours and then take it out to obtain modified coarse aggregate.

[0083] Example 15

[0084] Example 15 provides a carbonation-resistant concrete and its preparation method. The difference between Example 15 and Example 13 lies in the preparation method of the modified coarse aggregate. The preparation method of the modified coarse aggregate in Example 15 is as follows:

[0085] A1. Solution preparation: Add 4 kg of silane coupling agent to 10 L of 8% polyvinyl alcohol aqueous solution and stir and mix evenly at 60°C to obtain the adhesive.

[0086] A2. Modification: After cleaning the surface of the coarse aggregate, soak it in the adhesive for 6 hours and then take it out to obtain modified coarse aggregate.

[0087] Example 16

[0088] Example 16 provides a carbonation-resistant concrete and its preparation method. The difference between Example 16 and Example 13 is that step S1 includes the following steps:

[0089] S11. Premixed: The coating expansion agent and modified coarse aggregate are added to the concrete mixer and mixed to obtain premixed material;

[0090] S12. Remixing: Add silicate cement and fine sand to the premixed material in the concrete mixer and mix evenly to obtain structural material.

[0091] Comparative Example 1

[0092] Comparative Example 1 provides a carbonation-resistant concrete and its preparation method. The difference between Comparative Example 1 and Example 2 is that coarse aggregate is used to replace modified coarse aggregate in Comparative Example 1.

[0093] Comparative Example 2

[0094] Comparative Example 2 provides a carbonation-resistant concrete and its preparation method. The difference between Comparative Example 2 and Example 2 is that calcium sulfoaluminate is used to replace the coating expansion agent in Comparative Example 2.

[0095] Comparative Example 3

[0096] Comparative Example 3 provides a carbonation-resistant concrete and its preparation method. The difference between Comparative Example 3 and Example 2 is that in Comparative Example 3, coarse aggregate is used to replace modified coarse aggregate, and calcium sulfoaluminate is used to replace the coating expansion agent.

[0097] Testing and Inspection

[0098] The following tests were performed on the carbonation-resistant concrete prepared according to Examples 1-16 and Comparative Examples 1-3:

[0099] (1) The 56-day compressive strength (MPa) of carbonation resistant concrete was tested according to GB / T 50081-2002.

[0100] (2) The carbonation depth (mm) of carbonation resistant concrete at 28 days was tested according to GB / T 50082-2009.

[0101] The test data are shown in Table 2.

[0102] Table 2: Compressive strength and carbonation depth of carbonation-resistant concrete.

[0103] Data source 56-day compressive strength (MPa) 28-day carbonization depth (mm) Example 1 53.3 9.3 Example 2 53.9 8.9 Example 3 53.5 9.2 Example 4 51.2 10.5 Example 5 51.4 10.2 Example 6 51.9 9.8 Example 7 52.1 9.6 Example 8 50.8 11.5 Example 9 52.6 9.7 Example 10 52.8 9.6 Example 11 55.6 7.3 Example 12 54.3 8.2 Example 13 57.2 5.8 Example 14 56.3 6.3 Example 15 55.9 6.8 Example 16 58.3 4.6 Comparative Example 1 44.8 15.4 Comparative Example 2 43.1 18.3 Comparative Example 3 40.2 20.6

[0104] The following detailed description of this application is based on the experimental data provided in Table 1-2.

[0105] Examples 1-3 investigated the effects of fine aggregate, silicate cement, water, and water-reducing agent on the compressive strength and carbonation resistance of the prepared carbonation-resistant concrete. The 56-day compressive strength of the carbonation-resistant concrete prepared in Example 2 was greater than that of the concrete prepared in Examples 1 and 3. The 28-day carbonation depth of the carbonation-resistant concrete prepared in Example 2 was also less than that of the concrete prepared in Examples 1 and 3, indicating that the carbonation-resistant concrete prepared in Example 2 had higher compressive strength and stronger carbonation resistance. Considering all factors, Example 2 is the preferred embodiment.

[0106] Using Example 2 as a control, Examples 4 and 5 investigated the effect of modified coarse aggregate on the compressive strength and carbonation resistance of the prepared carbonation-resistant concrete. The 56-day compressive strength of the carbonation-resistant concrete prepared in Example 2 was greater than that of the concrete prepared in Examples 4 and 5, while the 28-day carbonation depth of the carbonation-resistant concrete prepared in Example 2 was less than that of the concrete prepared in Examples 4 and 5. This indicates that the carbonation-resistant concrete prepared in Example 2 has higher compressive strength and stronger carbonation resistance. Considering all factors, Example 2 is the preferred embodiment.

[0107] Compared with Example 2, Examples 6 and 7 investigated the effect of the coating expansion agent on the compressive strength and carbonation resistance of the prepared carbonation-resistant concrete. The 56-day compressive strength of the carbonation-resistant concrete prepared in Example 2 was greater than that of the concrete prepared in Examples 6 and 7, while the 28-day carbonation depth of the carbonation-resistant concrete prepared in Example 2 was less than that of the concrete prepared in Examples 6 and 7. This indicates that the carbonation-resistant concrete prepared in Example 2 has higher compressive strength and stronger carbonation resistance. Considering all factors, Example 2 is the preferred embodiment.

[0108] Compared with Example 2, Example 8 investigated the effect of the type of binder used in preparing the improved coarse aggregate on the compressive strength and carbonation resistance of the resulting carbonation-resistant concrete. The 56-day compressive strength of the carbonation-resistant concrete prepared in Example 2 was greater than that of the carbonation-resistant concrete prepared in Example 8, and the 28-day carbonation depth of the carbonation-resistant concrete prepared in Example 2 was less than that of the carbonation-resistant concrete prepared in Example 8. This indicates that the carbonation-resistant concrete prepared in Example 2 has higher compressive strength and stronger carbonation resistance. Considering all factors, Example 2 is the preferred embodiment.

[0109] Using Example 2 as a control, Examples 9 and 10 investigated the effect of the proportions of raw materials used to prepare the coating expansion agent on the compressive strength and carbonation resistance of the resulting carbonation-resistant concrete. The 56-day compressive strength of the carbonation-resistant concrete prepared in Example 2 was greater than that of the concrete prepared in Examples 9 and 10, while the 28-day carbonation depth of the carbonation-resistant concrete prepared in Example 2 was less than that of the concrete prepared in Examples 9 and 10. This indicates that the carbonation-resistant concrete prepared in Example 2 has higher compressive strength and stronger carbonation resistance. Considering all factors, Example 2 is the preferred embodiment.

[0110] Compared with Example 2, Examples 11 and 12 investigated the effect of the number-average molecular weight of polyethyleneimine used to prepare the coating expansion agent on the compressive strength and carbonation resistance of the prepared carbonation-resistant concrete. The 56-day compressive strength of the sample prepared in Example 11 was greater than that of the samples prepared in Examples 2 and 12, and the 28-day carbonation depth of the sample prepared in Example 11 was less than that of the samples prepared in Examples 2 and 12. This indicates that the carbonation-resistant concrete prepared in Example 11 has higher compressive strength and stronger carbonation resistance. Considering all factors, Example 11 is the preferred embodiment.

[0111] Compared with Example 11, Example 13 investigated the effect of the steps in preparing the coating expansion agent on the compressive strength and carbonation resistance of the obtained carbonation-resistant concrete. The 56-day compressive strength of the sample prepared in Example 13 was greater than that of the sample prepared in Example 11, and the 28-day carbonation depth of the sample prepared in Example 13 was less than that of the sample prepared in Example 11. This indicates that the carbonation-resistant concrete prepared in Example 13 has higher compressive strength and stronger carbonation resistance. Considering all factors, Example 13 is the preferred embodiment.

[0112] Using Example 13 as a control, Examples 14 and 15 investigated the effect of the raw material ratio for preparing the modified coarse aggregate on the compressive strength and carbonation resistance of the resulting carbonation-resistant concrete. The 56-day compressive strength of the sample prepared in Example 13 was greater than that of the samples prepared in Examples 14 and 15, and the 28-day carbonation depth of the sample prepared in Example 13 was less than that of the sample prepared in Example 15. This indicates that the carbonation-resistant concrete prepared in Example 13 has higher compressive strength and stronger carbonation resistance. Considering all factors, Example 13 is the preferred embodiment.

[0113] Compared with Example 13, Example 16 investigated the effect of the preparation steps of the carbonation-resistant concrete on the compressive strength and carbonation resistance of the obtained carbonation-resistant concrete. The 56-day compressive strength of the sample prepared in Example 16 was greater than that of the sample prepared in Example 13, and the 28-day carbonation depth of the sample prepared in Example 16 was less than that of the sample prepared in Example 13. This indicates that the carbonation-resistant concrete prepared in Example 16 has higher compressive strength and stronger carbonation resistance. Considering all factors, Example 16 is the preferred embodiment.

[0114] Using Example 2 as a control, Comparative Examples 1-3 investigated the effects of modified coarse aggregate and coating expansion agent on the compressive strength and carbonation resistance of the prepared carbonation-resistant concrete. The 56-day compressive strength of the sample prepared in Example 2 was significantly greater than that of the samples prepared in Comparative Examples 1-3, and the 28-day carbonation depth of the sample prepared in Example 2 was significantly smaller than that of the samples prepared in Comparative Examples 1-3. This indicates that the modified coarse aggregate and the coating expansion agent have a synergistic effect, greatly improving the compressive strength and carbonation resistance of mass concrete.

[0115] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A carbonation-resistant concrete, characterized in that: It is prepared from the following components in parts by weight: 100-200 parts of modified coarse aggregate; 50-90 parts fine sand; 60-80 parts of silicate cement; 15-24 parts water; 2-4 parts water-reducing agent; 6-9 parts of coating expander; The preparation method of the coating swelling agent is as follows: Polyethyleneimine, ethanol, and an expanding agent are mixed and ball-milled to obtain a coating expanding agent; The mixing process includes: first premixing polyethyleneimine and ethanol to obtain a premix, and then mixing the premix with an expanding agent. The expanding agent includes calcium sulfoaluminate; The modified coarse aggregate is prepared as follows: A1. Mix the adhesive and silane coupling agent to obtain the adhesive; A2. After soaking the coarse aggregate in the binder, remove it to obtain modified coarse aggregate; The adhesive is an aqueous solution of polyvinyl alcohol.

2. The carbonation-resistant concrete according to claim 1, characterized in that: The weight ratio of the expanding agent to the polyethyleneimine is (7.5-15):

1.

3. The carbonation-resistant concrete according to claim 1, characterized in that: The number-average molecular weight of the polyethyleneimine is 3500-10000.

4. The carbonation-resistant concrete according to claim 1, characterized in that: The volume weight ratio of the adhesive to the silane coupling agent is 2.5-3L:1kg.

5. The carbonation-resistant concrete according to claim 1, characterized in that: The weight ratio of the coating expansion agent to the modified coarse aggregate is (0.035-0.07):

1.

6. A method for preparing carbonation-resistant concrete according to any one of claims 1-5, characterized in that: Includes the following steps: S1. Mix the coating expansion agent, silicate cement, modified coarse aggregate and fine sand to obtain the structural material; S2. Mix the structural material, water-reducing agent and water evenly to obtain carbonation-resistant concrete.

7. The method for preparing carbonation-resistant concrete according to claim 6, characterized in that: Step S1 includes the following steps: S11. Mix the coating expansion agent and modified coarse aggregate to obtain a premix; S12. Mix silicate cement, fine sand and premixed material evenly to obtain structural material.

Images