High-strength self-repairing composite concrete based on modified charcoal and preparation method of high-strength self-repairing composite concrete

Abstract

The invention relates to the technical field of concrete, in particular to high-strength self-repairing composite concrete based on modified charcoal and a preparation method of the high-strength self-repairing composite concrete. The preparation method comprises the following steps: mixing and grinding ground biochar and polydopamine to obtain modified biochar; weighing 70-80 parts of ardealite, 40-55 parts of cement, 40-50 parts of slag, 90-120 parts of modified charcoal, 10-20 parts of nano silicon dioxide and 1-10 parts of a crystallization additive CA, and mixing to obtain a dry mixture; mixing the dry mixture with 4-7 parts of an alkali activator and 35-60 parts of water to obtain ardealite slurry; and curing the phosphogypsum slurry to obtain the composite concrete. PDA is used for modifying the biochar, so that the biochar has higher adsorption capacity, pores in the concrete can be more effectively filled, and the porosity is reduced, so that the strength and durability of the concrete are improved, the interface bonding force between the biochar and a concrete matrix is enhanced, and the mechanical property of the concrete is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and in particular to a high-strength self-healing composite concrete based on modified biochar and a preparation method thereof. Background Art

[0002] Reducing the carbon emissions of building materials and enhancing the carbon capture capacity of building materials are current hot issues. In response, carbon capture, utilization, and storage technologies are increasingly applied to the cement and concrete industries.

[0003] Biochar is a stable, carbon-rich solid pyrolyzed from biomass under oxygen-limited conditions. Its raw materials include a wide range of wastes such as crop residues, plants, manure, and sludge, making its production process carbon-negative. Thus, it is itself a green material with a high specific surface area and high porosity. Due to its good carbon sequestration potential, biochar has become a new and sustainable alternative in cementitious materials.

[0004] However, current research shows that when the addition amount of biochar is within 5%, the compressive strength, flexural strength, and splitting tensile strength of biochar concrete are not weaker than those of ordinary concrete. When the replacement rate exceeds 8%, the mechanical properties of biochar concrete will decrease significantly, and the workability is also poor. The amount of biochar used in the prepared concrete is too low to offset the CO 2 .

[0005] In addition, concrete will develop cracks due to various factors during use. If these cracks are not repaired in time, they may gradually expand, leading to a decline in the overall performance of the structure. Cracks will consume more manpower and material resources for repair. Although cementitious materials have an inherent ability to self-heal cracks due to continuous hydration, their crack repair efficiency is still limited. Existing research shows that a large amount of CO 2 emissions are generated during the production and use of traditional concrete, while self-healing concrete helps reduce carbon emissions and achieve emission reduction goals by extending the service life and reducing the demand for new material production. Therefore, it is necessary to develop a composite concrete that simultaneously has high strength, high carbon sequestration ability, and can self-heal, so as to meet the current requirements of buildings and the environment. Summary of the Invention

[0006] The purpose of the present invention is to propose a high-strength self-healing composite concrete based on modified biochar and a preparation method thereof in view of the above-mentioned deficiencies of the prior art.

[0007] The first object of the present invention is to provide a preparation method of a high-strength self-healing composite concrete based on modified biochar, comprising the following steps:

[0008] Mix the ground biochar with polydopamine by grinding to obtain modified biochar;

[0009] Weigh 70 - 80 parts of phosphogypsum, 40 - 55 parts of cement, 40 - 50 parts of slag, 90 - 120 parts of modified biochar, 10 - 20 parts of nano-silica, and 1 - 10 parts of crystal admixture CA, and mix them evenly to obtain a dry mix;

[0010] Mix the dry mix with 4 - 7 parts of alkali activator and 35 - 60 parts of water by stirring to obtain a phosphogypsum slurry;

[0011] Put the phosphogypsum slurry into a mold, vibrate, and cure to obtain composite concrete.

[0012] Furthermore, the alkali activator includes 2 - 3.5 parts of 40% concentration NaOH solution and 2 - 3 parts of 10% concentration water glass solution.

[0013] Furthermore, the mass ratio of the ground biochar to polydopamine is 2:1.

[0014] Furthermore, the biochar is ground for 0.5 - 1.5 h and then mixed with polydopamine and ground for 0.5 - 1.5 h.

[0015] Furthermore, the biochar is ground for 1 h and then mixed with polydopamine and ground for 1 h.

[0016] Furthermore, first mix 4 - 7 parts of alkali activator and 35 - 60 parts of water by stirring to obtain an alkali activator liquid, and then mix it with the dry mix by stirring to obtain a phosphogypsum slurry.

[0017] Furthermore, 73 - 76 parts of phosphogypsum, 45 - 50 parts of cement, 43 - 47 parts of slag, 100 - 110 parts of modified biochar, 12 - 17 parts of nano-silica, 3 - 7 parts of crystal admixture CA, 5 - 6 parts of alkali activator, and 40 - 50 parts of water

[0018] The second object of the present invention is to provide a high-strength self-healing composite concrete based on modified biochar prepared by the above preparation method.

[0019] The present invention utilizes the high adhesion performance of PDA to adhere it to the surface of biochar, and spontaneously forms a PDA film through cross-linking, reducing the agglomeration of biochar and its water absorption, thereby improving the workability of the mortar mixture, making it evenly distributed in the entire matrix, and improving the utilization rate of biochar. In addition, in an alkaline environment, PDA forms a composite material with calcium silicate hydrate (C-S-H, the primary hydration product of cement), thereby improving the mechanical properties of the carbon-fixing composite concrete. On the other hand, when cracks are generated in the material due to various factors during use, the crystal admixture CA can directly react with moisture and CO in the air 2The reaction forms calcite, improves the self-healing ability of the gel and mortar under non-invasive exposure conditions, and promotes the healing efficiency.

[0020] Generally speaking, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0021] 1. The modified substance PDA adopted in the present invention is a polymer material with rich functional groups. After modifying biochar, it has stronger adsorption ability, can more effectively fill the pores in concrete, reduce the porosity, and thus improve the strength and durability of concrete. In addition, the introduction of PDA may also enhance the interfacial bonding force between biochar and the concrete matrix, further improving the mechanical properties of concrete, and the compressive strength reaches more than 49.6 MPa.

[0022] 2. The use of nano-silica in the present invention can further reduce the voids of the functionalized biochar particles, resulting in a denser matrix, making the microstructure of the concrete more dense, thereby reducing the porosity and significantly improving the compressive strength of the concrete. On the other hand, nano-silica is composed of a large number of particles with good sphericity. Its incorporation reduces the friction between the phosphogypsum pastes, plays a role in lubricating the phosphogypsum pastes, effectively improves the fluidity of the phosphogypsum pastes, and can extend the setting time of the phosphogypsum pastes.

[0023] 3. The present invention adds a crystalline admixture CA, which can react with CO in the air and moisture when cracks occur in the cementitious material to stimulate the formation of calcite to repair the crack surface, and improve the self-healing ability of the gel and mortar under non-invasive exposure conditions. 2 and water to stimulate the formation of calcite to repair the crack surface, and improve the self-healing ability of the gel and mortar under non-invasive exposure conditions.

[0024] 4. The present invention can absorb a large amount of CO 2 , reduce the environmental impact brought by the greenhouse effect, meet the needs of industries such as construction while consuming a large amount of solid waste such as phosphogypsum, has the characteristics of high strength and high self-repair, can realize the functionalization, greening and low-carbonization of products in the directions of ocean engineering, construction engineering, etc., has a wide range of applications, and the carbon fixation effect can reach more than 88.3%.

[0025] 5. The production process of the present invention is simple, the raw material sources are wide and easy to adjust, and it is convenient to realize functionalization. Specific Embodiments

[0026] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0027] Example 1

[0028] The present embodiment provides a method for preparing high-strength self-repairing composite concrete based on modified biochar, which is composed of the following raw materials in parts by weight: 70 parts of phosphogypsum, 40 parts of cement, 45 parts of slag, 33 parts of PDA, 66 parts of biochar, 20 parts of nano-silicon dioxide, 10 parts of CA, 3.5 parts of 40% concentration NaOH solution, 2.2 parts of 10% concentration water glass solution, and 40 parts of water.

[0029] The method for preparing a high-strength self-repairing composite concrete based on modified biochar described above in this embodiment comprises the following steps:

[0030] S1: The biochar was ground using a ball mill for 1 hour, and then PDA was added in proportion, with the mass fraction of PDA in the mixture being approximately 33.33%, and the modified biochar was ground again for 1 hour.

[0031] S2: According to the weight ratio of raw materials, weigh phosphogypsum, cement, slag, modified biochar, nano-silica, and CA, stir in a stirrer, and mix evenly to obtain a dry mix;

[0032] S3: Stir water, 40% NaOH solution and 10% water glass solution in a volumetric bucket to obtain an alkali activator liquid after sufficient mixing;

[0033] S4: mixing the dry mix obtained in step S2 with the liquid obtained in step S3 according to the weight ratio of the raw materials, and stirring evenly to obtain a corresponding phosphogypsum slurry;

[0034] S5: Put the material obtained in step S4 into a mold, vibrate it on a vibration table for one minute, smooth the surface, leave it for 1 day, then take it out and put it in a curing room.

[0035] The compressive strength of the block was measured after curing for 3d, 7d, and 28d. The compressive strength of each embodiment at 3d, 7d, and 28d was tested according to GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete";

[0036] After 14 days of curing, the samples of the embodiment were placed in a fully automatic concrete carbonization test box for carbonization for 7 days, and the weight of the samples was measured every day. After the carbonization was completed, the mass change of the samples was calculated to study their effect on CO 2 The adsorption rate.

[0037] A diamond saw blade was used to perform precise cutting on the surface of each embodiment after 28 days of curing. The cutting depth and speed were adjusted to control the width and length of the cracks in each embodiment to remain consistent. After cutting and curing for 20 days and 40 days, an optical microscope was used to observe the curing effect of the cracks, and relevant data were recorded to calculate the self-repair rate of each embodiment.

[0038] The high-strength self-healing composite concrete prepared in Example 1 of the present invention was subjected to compressive strength test, CO 2 adsorption rate test, and self-healing rate test:

[0039] The results of the compressive strength test are shown in Table 1. It can be obtained that the compressive strength of the high-strength self-healing composite concrete after 3 days of curing is 34.2 MPa, the compressive strength after 7 days of curing is 40.2 MPa, and the compressive strength after 28 days of curing is 49.6 MPa.

[0040] CO 2 The results of the adsorption rate test are shown in Table 2. It can be obtained that the adsorption rate of CO 2 reaches 88.3% after 7 days of carbonization of the high-strength self-healing composite concrete

[0041] The results of the self-healing rate test are shown in Table 3. It can be obtained that the self-healing rate of the high-strength self-healing composite concrete reaches 85% after 20 days of cutting and curing, and the self-healing rate reaches 100% after 40 days of cutting and curing.

[0042] Example 2

[0043] A preparation method of high-strength self-healing composite concrete based on modified biochar in this example is composed of the following raw materials in parts by weight: 75 parts of phosphogypsum, 50 parts of cement, 50 parts of slag, 31 parts of PDA, 62 parts of biochar, 13 parts of nano-silica, 1 part of CA, 2.75 parts of 40% concentration NaOH solution, 3 parts of 10% concentration water glass solution, and 35 parts of water.

[0044] A preparation method of high-strength self-healing composite concrete based on modified biochar as described above in this example includes the following steps:

[0045] S1: Grind the biochar with a ball mill for 1 hour, then add PDA in proportion. The mass fraction of PDA in the mixture is about 33.33%, and grind for another 1 hour to prepare the modified biochar.

[0046] S2: Weigh phosphogypsum, cement, slag, modified biochar, nano-silica, and CA according to the weight ratio of the raw materials and stir them in a stirrer to obtain a dry mixture;

[0047] S3: Stir water, 40% concentration NaOH solution, and 10% concentration water glass solution evenly in a volumetric bucket to obtain an alkali activator liquid after sufficient mixing;

[0048] S4: Mix the dry mixture prepared in step S2 with the liquid prepared in S3 according to the weight ratio of the raw materials and stir evenly to obtain the corresponding phosphogypsum slurry;

[0049] S5: Load the material obtained in step S4 into a mold. After vibrating on a vibrating table for one minute, level the surface, let it stand for 1 day, then take it out and place it in a curing room.

[0050] Measure the compressive strength of the blocks after curing for 3 days, 7 days, and 28 days, and detect the compressive strength of each example at 3 days, 7 days, and 28 days according to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" GB / T50081-2002;

[0051] Put some samples of the examples after curing for 14 days into a full-automatic concrete carbonation test box for carbonation for 7 days, and keep measuring the weight of the samples every day. After carbonation is completed, calculate the mass change of the samples and study its adsorption rate of CO 2 of.

[0052] Use a diamond saw blade to precisely cut the surface of each example after curing for 28 days. Adjust the cutting depth and speed to control the width and length of the cracks in each example to be consistent. After cutting and curing for 20 days and 40 days, use an optical microscope to observe the curing effect of the cracks, record relevant data, and calculate the self-healing rate of each example.

[0053] Carry out compressive strength test, CO 2 adsorption rate test, and self-healing rate test on the high-strength self-healing composite concrete prepared in Example 2 of the present invention:

[0054] The test results of the compressive strength are shown in Table 1. It can be obtained that the compressive strength of the high-strength self-healing composite concrete after curing for 3 days is 36.3 MPa, the compressive strength after curing for 7 days is 42.5 MPa, and the compressive strength after curing for 28 days is 51.4 MPa.

[0055] CO 2 The test results of the adsorption rate are shown in Table 2. It can be obtained that the adsorption rate of CO 2 of the high-strength self-healing composite concrete reaches 89.8% after carbonation for 7 days

[0056] The test results of the self-healing rate are shown in Table 3. It can be obtained that the self-healing rate of the high-strength self-healing composite concrete reaches 82.2% after cutting and curing for 20 days, and the self-healing rate reaches 100% after cutting and curing for 40 days.

[0057] Example 3

[0058] A preparation method of a high-strength self-healing composite concrete based on modified biochar in this example is composed of the following raw materials in parts by weight: 80 parts of phosphogypsum, 40 parts of cement, 46 parts of slag, 30 parts of PDA, 60 parts of biochar, 15 parts of nano-silica, 6 parts of CA, 2 parts of 40% concentration NaOH solution, 2.5 parts of 10% concentration water glass solution, and 45 parts of water.

[0059] A preparation method of high-strength self-healing composite concrete based on modified biochar according to the above-described embodiments includes the following steps:

[0060] S1: Grind the biochar using a ball mill for 1 hour, then add PDA in proportion. The mass fraction of PDA in the mixture is about 33.33%, and grind again for 1 hour to prepare the modified biochar.

[0061] S2: Weigh phosphogypsum, cement, slag, modified biochar, nano-silica, and CA according to the weight ratio of raw materials, and stir them in a stirrer to obtain a dry mixture by uniform mixing.

[0062] S3: Stir water, 40% concentration NaOH solution, and 10% concentration water glass solution evenly in a measuring bucket, and obtain an alkali activator liquid after sufficient mixing.

[0063] S4: Mix the dry mixture prepared in step S2 with the liquid prepared in S3 according to the weight ratio of raw materials and stir evenly to obtain the corresponding phosphogypsum slurry.

[0064] S5: Load the material prepared in step S4 into a mold, vibrate it on a vibrating table for one minute, then level the surface, place it for 1 day, and then take it out and put it into a curing room.

[0065] Measure the compressive strength of the blocks after curing for 3 days, 7 days, and 28 days, and detect the compressive strength of each embodiment at 3 days, 7 days, and 28 days according to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" GB / T50081-2002.

[0066] Put some samples of the embodiments after curing for 14 days into a full-automatic concrete carbonation test box for carbonation for 7 days, and keep measuring the weight of the samples every day. After carbonation is completed, calculate the mass change of the samples and study its adsorption rate of CO 2 2.

[0067] Use a diamond saw blade to precisely cut the surface of each embodiment after curing for 28 days, adjust the cutting depth and speed to control the width and length of the cracks in each embodiment to be consistent. Observe the crack curing effect with an optical microscope after cutting and curing for 20 days and 40 days, and record relevant data to calculate the self-healing rate of each embodiment.

[0068] Conduct compressive strength test, CO 2 2 adsorption rate test, and self-healing rate test on the high-strength self-healing composite concrete prepared in Example 3 of the present invention:

[0069] The test results of the compressive strength are shown in Table 1. It can be obtained that the compressive strength of the high-strength self-healing composite concrete after curing for 3 days is 35.2 MPa, the compressive strength after curing for 7 days is 41.4 MPa, and the compressive strength after curing for 28 days is 50.3 MPa.

[0070] CO 2 The adsorption rate test results of CO are shown in Table 2. It can be concluded that the adsorption rate of CO in the high-strength self-healing composite concrete reaches 91.2% after 7 days of carbonization. 2

[0071] The self-healing rate test results are shown in Table 3. It can be concluded that the self-healing rate of the high-strength self-healing composite concrete reaches 88.3% after 20 days of cutting and curing, and reaches 100% after 40 days of cutting and curing.

[0072] Without conflict, the above embodiments and the features in the embodiments in this article can be combined with each other.

[0073] Those skilled in the art can easily understand that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0074] Example 4

[0075] A preparation method of high-strength self-healing composite concrete based on modified biochar in this embodiment is composed of the following raw materials in parts by weight: 74 parts of phosphogypsum, 44 parts of cement, 45 parts of slag, 35 parts of PDA, 70 parts of biochar, 20 parts of nano-silica, 7 parts of CA, 2 parts of 40% concentration NaOH solution, 2 parts of 10% concentration water glass solution, and 60 parts of water.

[0076] A preparation method of high-strength self-healing composite concrete based on modified biochar as described above in this embodiment includes the following steps:

[0077] S1: Grind the biochar with a ball mill for 1 hour, then add PDA in a ratio of 2:1 and grind again for 1 hour to prepare the modified biochar;

[0078] S2: Weigh phosphogypsum, cement, slag, modified biochar, nano-silica, and CA according to the weight ratio of the raw materials and stir them in a stirrer to obtain a dry mixture;

[0079] S3: Stir water, 40% concentration NaOH solution, and 10% concentration water glass solution evenly in a capacity bucket to obtain an alkali activator liquid after sufficient mixing;

[0080] S4: Mix the dry mixture prepared in step S2 with the liquid prepared in S3 according to the weight ratio of the raw materials and stir evenly to obtain the corresponding phosphogypsum slurry;

[0081] S5: Load the material prepared in step S4 into a mold, vibrate it on a vibrating table for one minute, then level the surface, place it for 1 day, and then take it out and put it into a curing room.​

[0082] Measure the compressive strength of the specimens after curing for 3d, 7d, and 28d, and detect the compressive strength of each example at 3d, 7d, and 28d according to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T 50081-2002).

[0083] Put some specimens of the examples after curing for 14d into a full-automatic concrete carbonation test box for carbonation for 7 days, and keep measuring the weight of the specimens every day. After carbonation is completed, calculate the mass change of the specimens and study its adsorption rate of CO 2 .

[0084] Use a diamond saw blade to precisely cut the surfaces of each example after curing for 28d, adjust the cutting depth and speed to keep the width and length of the cracks in each example consistent. Observe the curing effect of the cracks by optical microscope after cutting and curing for 20d and 40d, and record relevant data to calculate the self-healing rate of each example.

[0085] Conduct compressive strength test, CO 2 adsorption rate test, and self-healing rate test on the high-strength self-healing composite concrete prepared in Example 4 of the present invention:

[0086] The test results of the compressive strength are shown in Table 1. It can be obtained that the compressive strength of the high-strength self-healing composite concrete after curing for 3 days is 41.8 MPa, the compressive strength after curing for 7 days is 46.3 MPa, and the compressive strength after curing for 28 days is 55.1 MPa.

[0087] CO 2 The test results of the adsorption rate are shown in Table 2. It can be obtained that the adsorption rate of CO 2 of the high-strength self-healing composite concrete reaches 93.4% after carbonation for 7d.

[0088] The test results of the self-healing rate are shown in Table 3. It can be obtained that the self-healing rate of the high-strength self-healing composite concrete reaches 87.5% after cutting and curing for 20d, and the self-healing rate reaches 100% after cutting and curing for 40d.

[0089] Example 5

[0090] A preparation method of a high-strength self-healing composite concrete based on modified biochar in this example is composed of the following raw materials in parts by weight: 76 parts of phosphogypsum, 47.5 parts of cement, 43 parts of slag, 30 parts of PDA, 60 parts of biochar, 18 parts of nano-silica, 10 parts of CA, 2.75 parts of 40% concentration NaOH solution, 2.7 parts of 10% concentration water glass solution, and 60 parts of water.

[0091] The preparation method of a high-strength self-healing composite concrete based on modified biochar described above in this example includes the following steps:

[0092] S1: Use a ball mill to grind the biochar for 1 hour, then add PDA in proportion. The mass fraction of PDA in the mixture is about 33.33%, and grind again for 1 hour to prepare the modified biochar;

[0093] S2: Weigh phosphogypsum, cement, slag, modified biochar, nano-silica, and CA according to the weight ratio of raw materials, and stir them in a stirrer to obtain a dry mixture by uniform mixing;

[0094] S3: Stir water, 40% concentration NaOH solution, and 10% concentration water glass solution evenly in a measuring bucket, and obtain an alkali activator liquid after sufficient mixing;

[0095] S4: Mix the dry mixture prepared in step S2 according to the weight ratio of raw materials and the liquid prepared in S3, and stir evenly to obtain the corresponding phosphogypsum paste;

[0096] S5: Load the material prepared in step S4 into a mold, vibrate it on a vibrating table for one minute, then level the surface, place it for 1 day, and then take it out and put it into a curing room.

[0097] The curing condition is the standard curing of concrete, the temperature range is 20±2, and the humidity is above 95%. The same curing conditions are used for other embodiments.

[0098] Measure the compressive strength of the blocks after curing for 3d, 7d, and 28d, and detect the compressive strength of each embodiment at 3d, 7d, and 28d according to the "Standard Test Method for Mechanical Properties of Ordinary Concrete" GB / T50081-2002;

[0099] Put some samples of the embodiments after curing for 14d into a full-automatic concrete carbonation test box for carbonation for 7 days, and keep measuring the weight of the samples every day. After carbonation is completed, calculate the mass change of the samples and study its adsorption rate of CO 2 2.

[0100] Use a diamond saw blade to precisely cut the surface of each embodiment after curing for 28d, adjust the cutting depth and speed to control the width and length of the cracks in each embodiment to be consistent, observe the curing effect of the cracks by optical microscope after cutting and curing for 20d and 40d, and record relevant data to calculate the self-healing rate of each embodiment.

[0101] Carry out compressive strength test, CO 2 2 adsorption rate test, and self-healing rate test on the high-strength self-healing composite concrete prepared in Example 5 of the present invention:

[0102] The test results of the compressive strength are shown in Table 1. It can be obtained that the compressive strength of the high-strength self-healing composite concrete is 40.7 MPa after 3 days of curing, 45.2 MPa after 7 days of curing, and 53.4 MPa after 28 days of curing.

[0103] CO 2 The test results of the adsorption rate of 2 CO are shown in Table 2. It can be obtained that the adsorption rate of CO of the high-strength self-healing composite concrete reaches 89.2% after 7 days of carbonization.

[0104] The test results of the self-healing rate are shown in Table 3. It can be obtained that the self-healing rate of the high-strength self-healing composite concrete reaches 85.1% after 20 days of cutting and curing, and 100% after 40 days of cutting and curing.

[0105] Example 6

[0106] A preparation method of high-strength self-healing composite concrete based on modified biochar in this example consists of the following raw materials by weight: 70 parts of phosphogypsum, 55 parts of cement, 45 parts of slag, 40 parts of PDA, 80 parts of biochar, 10 parts of nano-silica, 4 parts of CA, 2.2 parts of 40% concentration NaOH solution, 2.5 parts of 10% concentration water glass solution, and 47.5 parts of water.

[0107] The preparation method of high-strength self-healing composite concrete based on modified biochar described above in this example includes the following steps:

[0108] S1: Grind the biochar with a ball mill for 1 hour, then add PDA in proportion. The mass fraction of PDA in the mixture is about 33.33%, and grind for another 1 hour to prepare the modified biochar;

[0109] S2: Weigh phosphogypsum, cement, slag, modified biochar, nano-silica, and CA according to the weight ratio of the raw materials and stir them in a stirrer to obtain a dry mixture;

[0110] S3: Stir water, 40% concentration NaOH solution, and 10% concentration water glass solution evenly in a volumetric bucket to obtain an alkali activator liquid after full mixing;

[0111] S4: Mix the dry mixture prepared in step S2 with the liquid prepared in S3 according to the weight ratio of the raw materials and stir evenly to obtain the corresponding phosphogypsum slurry;

[0112] S5: Put the material prepared in step S4 into a mold, vibrate it on a vibrating table for one minute, then level the surface, place it for 1 day, and then take it out and put it into the curing room.

[0113] Measure the compressive strength of the specimens after curing for 3d, 7d, and 28d, and detect the compressive strength of each example at 3d, 7d, and 28d according to the Standard for Test Methods of Mechanical Properties on Ordinary Concrete (GB / T 50081-2002).

[0114] Put some samples of the examples after curing for 14d into a full-automatic concrete carbonation test chamber for carbonation for 7 days, and keep measuring the weight of the samples every day. After carbonation is completed, calculate the mass change of the samples and study their adsorption rate of CO 2 .

[0115] Use a diamond saw blade to precisely cut the surfaces of each example after curing for 28d, adjust the cutting depth and speed to make the width and length of the cracks in each example consistent, observe the curing effect of the cracks by optical microscope after cutting and curing for 20d and 40d, and record relevant data to calculate the self-healing rate of each example.

[0116] Carry out compressive strength test, CO 2 adsorption rate test, and self-healing rate test on the high-strength self-healing composite concrete prepared in Example 6 of the present invention:

[0117] The test results of the compressive strength are shown in Table 1. It can be obtained that the compressive strength of the high-strength self-healing composite concrete after curing for 3 days is 37.4 MPa, the compressive strength after curing for 7 days is 42.8 MPa, and the compressive strength after curing for 28 days is 51.9 MPa.

[0118] CO 2 The test results of the adsorption rate are shown in Table 2. It can be obtained that the adsorption rate of CO 2 of the high-strength self-healing composite concrete reaches 90.5% after carbonation for 7d

[0119] The test results of the self-healing rate are shown in Table 3. It can be obtained that the self-healing rate of the high-strength self-healing composite concrete reaches 84.6% after cutting and curing for 20d, and the self-healing rate reaches 100% after cutting and curing for 40d.

[0120] Comparative Example 1

[0121] This comparative example is composed of the following raw materials by weight: 74 parts of phosphogypsum, 44 parts of cement, 45 parts of slag, 70 parts of biochar, 20 parts of nano-silica, 7 parts of CA, 2 parts of 40% concentration NaOH solution, 2 parts of 10% concentration water glass solution, and 60 parts of water.

[0122] The preparation method of a kind of high-strength self-healing composite concrete based on modified biochar described above in this comparative example includes the following steps:

[0123] S1: Grind the biochar with a ball mill for 1 hour;

[0124] S2: Weigh phosphogypsum, cement, slag, biochar, and nano-silica according to the raw material weight ratio, and stir them in a blender to obtain a dry mixture by uniform mixing.

[0125] S3: Stir water, 40% concentration NaOH solution, and 10% concentration water glass solution evenly in a volumetric bucket, and obtain an alkali-activated agent liquid after sufficient mixing.

[0126] S4: Mix the dry mixture prepared in step S2 according to the raw material weight ratio with the liquid prepared in S3, and stir evenly to obtain the corresponding phosphogypsum paste.

[0127] S5: Load the material prepared in step S4 into a mold, vibrate it on a vibrating table for one minute, then level the surface, place it for 1 day, and then take it out and put it into a curing room.

[0128] Measure the compressive strength of the blocks after curing for 3 days, 7 days, and 28 days, and detect the compressive strength of each example at 3 days, 7 days, and 28 days according to the "Standard Test Method for Mechanical Properties of Ordinary Concrete" GB / T50081 - 2002.

[0129] Put some samples of the examples after curing for 14 days into a fully automatic concrete carbonation test box for carbonation for 7 days, and keep measuring the weight of the samples every day. After carbonation is completed, calculate the mass change of the samples and study its adsorption rate of CO 2 2.

[0130] Use a diamond saw blade to precisely cut the surface of the comparative example after curing for 28 days, adjust the cutting depth and speed to control the width and length of the cracks in each example to be consistent. After cutting and curing for 20 days and 40 days, observe the curing effect of the cracks with an optical microscope, record the relevant data, and calculate the self - repair rate of each example.

[0131] Conduct compressive strength test, CO 2 2 adsorption rate test, and self - repair rate test on the biochar composite concrete prepared in the comparative example of the present invention:

[0132] The test results of compressive strength are shown in Table 1. It can be concluded that the compressive strength of this high - strength self - repairing composite concrete after curing for 3 days is 2.5 MPa, the compressive strength after curing for 7 days is 5.7 MPa, and the compressive strength after curing for 28 days is 8.8 MPa.

[0133] CO 2 2 adsorption rate test results are shown in Table 2. It can be concluded that the adsorption rate of CO 2 2 of this high - strength self - repairing composite concrete reaches 89.6% after carbonation for 7 days.

[0134] The self - healing rate test results are shown in Table 3. It can be concluded that the self - healing rate of the high - strength self - healing composite concrete reaches 86.6% after cutting and curing for 20 days, and reaches 100% after cutting and curing for 40 days.

[0135] Table 1 Test results of normal - temperature performance indicators of high - strength self - healing composite concrete products prepared in Comparative Example 1 and Examples 1 - 6

[0136]

[0137] Table 2 Test results table of CO 2 adsorption rate of high - strength self - healing composite concrete products prepared in Comparative Example 1 and Examples 1 - 6

[0138]

[0139]

[0140] Table 3 Test results table of self - healing rate of high - strength self - healing composite concrete products prepared in Examples 1 - 6

[0141]

[0142] It can be observed from Tables 1, 2, and 3 that the corresponding performance of Example 4 is the best. Compared with Example 4, PDA is not doped in the cementitious material in Comparative Example 1. The corresponding performance test results of Comparative Example 1 are shown in Tables 1, 2, and 3. From the test data results of the compressive strength performance in Table 1, it can be shown that the composite concrete prepared by adding biochar modified with PDA can not only adsorb a large amount of carbon dioxide, but also improve the compressive strength of the material, effectively solving the problem that the carbon adsorption capacity and strength are not consistent.

[0143] Where not covered above, it shall apply to the prior art.

[0144] Although some specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration purposes and not for limiting the scope of the present invention. Those skilled in the technical field to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar ways to substitute, but will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made in accordance with the technical essence of the present invention to the above - mentioned embodiments shall be included in the protection scope of the present invention.

Claims

1. A method for preparing high-strength self-repairing composite concrete based on modified biochar, characterized in that: The steps include: The ground biochar is mixed with polydopamine and ground to obtain modified biochar; Weigh 70-80 parts of phosphogypsum, 40-55 parts of cement, 40-50 parts of slag, 90-120 parts of modified biochar, 10-20 parts of nano-silicon dioxide, and 1-10 parts of crystallization admixture CA, and mix them evenly to obtain a dry mix; The dry mix is ​​mixed with 4-7 parts of an alkali activator and 35-60 parts of water to obtain a phosphogypsum slurry; The phosphogypsum slurry is loaded into a mold, vibrated, and cured to obtain composite concrete.

2. The preparation method according to claim 1, characterized in that The alkaline activator includes 2 to 3.5 parts of 40% concentration NaOH solution and 2 to 3 parts of 10% concentration water glass solution.

3. The preparation method according to claim 1, characterized in that: The mass ratio of ground biochar to polydopamine was 2:

1.

4. The preparation method according to claim 1, characterized in that: The biochar was ground for 0.5-1.5 h and then mixed with polydopamine and ground for 0.5-1.5 h.

5. The preparation method according to claim 4, characterized in that: The biochar was ground for 1 h and then mixed with polydopamine and ground for 1 h.

6. The preparation method according to claim 1, characterized in that: First, 4-7 parts of alkali activator and 35-60 parts of water are stirred and mixed to obtain alkali activator liquid, and then stirred and mixed with the dry mixed material to obtain phosphogypsum slurry.

7. The preparation method according to claim 1, characterized in that: 73-76 parts of phosphogypsum, 45-50 parts of cement, 43-47 parts of slag, 100-110 parts of modified biochar, 12-17 parts of nano-silicon dioxide, 3-7 parts of crystallizing admixture CA, 5-6 parts of alkali activator, and 40-50 parts of water.

8. A high-strength self-repairing composite concrete based on modified biochar prepared by the preparation method according to any one of claims 1 to 7.

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