A low-carbon, crack-resistant, self-healing mass concrete and its preparation method

Abstract

This invention discloses a low-carbon, crack-resistant, self-healing mass concrete and its preparation method. The mass concrete comprises the following components by weight: 340-440 parts of active binder, 60-100 parts of other binders, 680-750 parts of fine aggregate, 1030-1100 parts of coarse aggregate, 155-165 parts of water, and 7-11 parts of high-performance admixture. The active binder is a mixture of cement, fly ash, and mineral powder; the other binders are a mixture of granite sawdust and treated recycled micro-powder; the fine aggregate is a mixture of sand and internal curing fine aggregate; the coarse aggregate is a mixture of crushed stone and mineralized self-healing phase change coarse aggregate; and the high-performance admixture is a composite admixture, a mixture of high-performance polycarboxylate superplasticizer powder, a hydration heat inhibitor, and a shrinkage reducer. The low-carbon, crack-resistant, self-healing mass concrete provided by this invention has advantages such as excellent strength, low shrinkage, excellent crack resistance and impermeability, and self-healing function of cracks, which can effectively improve the service performance of mass concrete; at the same time, the preparation method is simple and suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a low-carbon, crack-resistant, self-healing large-volume concrete and its preparation method. Background Technology

[0002] Concrete is the most widely used man-made building material in the world today, extensively applied in bridges, high-rise buildings, railways, shipping, and other engineering projects. However, concrete is characterized by its compressive strength but not tensile strength. Its self-shrinkage, thermal shrinkage, and external stresses can all cause cracks to develop, which negatively impact the lifespan and functionality of the concrete. In particular, large-volume concrete structures, due to their large size and thickness, are highly susceptible to cracking due to the accumulation of heat during hydration, leading to significant temperature differences between the inside and outside of the concrete structure and concentrated temperature stress. This can result in the overall destruction of the concrete structure, affecting its use and, in severe cases, even compromising its durability and safety.

[0003] Common methods for repairing concrete cracks include manual grouting, but these methods only address visible, obvious cracks and cannot repair deep, fine cracks. Currently, there are many research findings on microbial self-healing technology for concrete. CN103043937 discloses a self-healing system for underground concrete structures using composite capsules containing aerobic microorganisms. However, the preparation process of this microcapsule-based microbial-repaired concrete is complex, difficult to mold, and the equipment is expensive, resulting in high production costs and limiting its application. Therefore, researching a self-healing large-volume concrete with a simple preparation process and suitable for widespread application is of great significance. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a low-carbon, crack-resistant, self-healing mass concrete and its preparation method to address the shortcomings of the prior art. The concrete has the advantages of excellent strength, low shrinkage, excellent crack resistance and impermeability, and self-healing function of cracks, which can effectively improve the service performance of mass concrete. At the same time, the preparation method is simple and suitable for widespread application.

[0005] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows:

[0006] A low-carbon, crack-resistant, self-healing mass concrete, comprising the following components by weight:

[0007] 340-440 parts of active adhesive material;

[0008] Other adhesive materials: 60-100 parts;

[0009] Fine aggregate 680-750 parts;

[0010] 1030-1100 parts of coarse aggregate;

[0011] 155-165 parts water;

[0012] 7-11 parts of high-performance admixture;

[0013] The active adhesive is a mixture of cement, fly ash, and mineral powder; the other adhesive is a mixture of granite sawdust and treated recycled micro powder; the fine aggregate is a mixture of sand and internally cured fine aggregate; the coarse aggregate is a mixture of crushed stone and mineralized self-healing phase change coarse aggregate; the high-performance admixture is a composite admixture, a mixture of high-performance polycarboxylate superplasticizer powder, hydration heat inhibitor, and shrinkage reducer.

[0014] In the above scheme, the active adhesive contains 260-340 parts by weight of cement, and 80-100 parts by weight of fly ash and mineral powder; the cement is PO 42.5 cement, the fly ash is grade I or II fly ash, and the mineral powder is grade S95 or S105 mineral powder.

[0015] In the above scheme, the mass ratio of granite sawdust to treated recycled micro powder in the other adhesive materials is 1:(1-2); the granite sawdust is granite cutting tailings with a SiO2 content of 70%-80%, a loss on ignition of 1.0-1.8%, a 28-day activity index of 75%-80%, and a particle size range of less than 75 μm.

[0016] In the above scheme, the preparation method of the other adhesive material specifically includes the following: mixing granite sawdust and treated recycled micro powder and ball milling for 30-40 minutes to obtain the other adhesive material; during the ball milling process, an external grinding aid is added, the external grinding aid is lignin sulfonate, and its mass is 0.06%-0.12% of the total mass of granite sawdust and treated recycled micro powder.

[0017] The preparation method of the treated recycled micro powder in the above scheme specifically includes the following: during the process of preparing recycled aggregate from waste concrete, fine particles with a particle size of less than 75 μm are screened to obtain initial recycled micro powder; the initial recycled micro powder is added to water to form a slurry, wherein the slurry concentration is 200-300 g / L; the temperature of the slurry is controlled at 60-80℃; carbon dioxide gas is introduced into the slurry for stirring and carbonization for 1-2 hours; after filtration and drying, the treated recycled micro powder is obtained; wherein the carbon dioxide gas is industrial waste gas with a CO2 content of 80%-95%.

[0018] In the above scheme, the mass ratio of sand to internal curing fine aggregate in the fine aggregate is (60-50):(40-50); the sand is one of ordinary manufactured sand or river sand.

[0019] The preparation method of the internally cured fine aggregate in the above scheme specifically includes the following: granite sawdust, treated recycled micro powder, composite expansion agent, alkali activator, and NaOH are mixed into pellets and granulated, then placed in a 300-500MHz microwave environment for 30-40 minutes, ceramsite with a particle size of 0-5mm is screened, and then cured at 95%-100%RH and 35±5℃ for 7 days, and then naturally cured for 21 days to obtain the internally cured fine aggregate.

[0020] In the above scheme, the composition of the internal curing fine aggregate, based on 100 parts by weight, includes: 10-20 parts granite sawdust, 20-30 parts of treated recycled micro powder, 20-30 parts of composite expansion agent, 5-8 parts of alkali activator, 1-3 parts of NaOH, and the balance being water.

[0021] In the above scheme, the composite expanding agent is MgO, CaO and Ca4Al6SO4. 16 A mixture of MgO, CaO and Ca4Al6SO4 16 The mass ratio is (20-40): (30-50): (10-20).

[0022] In the above scheme, the alkaline activator is a water glass solution with a modulus of 2.8 to 3.0.

[0023] In the above scheme, the NaOH used is commercially available industrial flake NaOH with a purity of 99.9%.

[0024] In the above scheme, the mass ratio of crushed stone and mineralized self-healing phase change coarse aggregate in the coarse aggregate is (60-75):(25-40); the mass ratio of high-performance polycarboxylate superplasticizer powder, hydration heat inhibitor, and shrinkage reducer in the high-performance admixture is 1:(0.8-1.0):(0.1-0.2).

[0025] In the above scheme, the high-performance polycarboxylate superplasticizer powder is a commercially available superplasticizer powder with a solid content of 98% ± 1%, a pH value of 7 to 9, a water bleeding rate of ≤ 85%, and a water reduction rate of 32% to 35%.

[0026] In the above scheme, the heat of hydration inhibitor is a commercially available HHC-S type heat of hydration inhibitor with a setting time difference ≤300min, a bleeding rate ≤100%, a concrete compressive strength ratio ≥100% over 28 days, and a concrete adiabatic temperature rise reduction rate (1 day) ≥15%.

[0027] In the above scheme, the shrinkage reducing agent is commercially available SRA815, which has a concrete compressive strength ratio of ≥95% at 28 days and a shrinkage reduction rate of ≥30% at 28 days.

[0028] In the above scheme, the preparation method of the mineralized self-healing phase change coarse aggregate specifically includes the following:

[0029] S1, fine particles with a particle size of 4.75 to 20 mm are taken during the process of preparing recycled aggregate from waste concrete to obtain core material;

[0030] S2, take the other adhesive materials, microbial additives, alkali activator, and NaOH, mix them, and stir evenly to obtain shell material; place the core material obtained in step S1 in a granulator, add the shell material while spraying water, granulate, and then place it in a temperature of 40-60℃ and 90%-99%RH for 7-14 days to obtain self-healing coarse aggregate; wherein the mass ratio of the core material to the shell material is 1:(2-3); the mass ratio of the other adhesive materials, microbial additives, alkali activator, and NaOH in the shell material is (60-70):(3-5):(20-25):(3-5);

[0031] S3, Place the self-healing coarse aggregate obtained in step S2 in a CO2 curing chamber for 8-10 hours. The curing conditions are 80%-85% RH, temperature 20-30℃, and CO2 pressure 0.1-0.2 MPa. After taking it out, place it in the air for 28 days to obtain mineralized self-healing coarse aggregate.

[0032] S4, the mineralized self-healing coarse aggregate obtained in step S3 is placed in a microbial additive and adsorbed under a negative pressure of 30-40 kPa for 10-20 min. Then it is placed in molten phase change paraffin and adsorbed under a negative pressure of 80-100 kPa in a constant temperature water bath at 80-90℃ for 40-60 min. After cooling to room temperature, it is taken out and air-dried to obtain the mineralized self-healing phase change coarse aggregate. The mass ratio of the mineralized self-healing coarse aggregate, microbial additive and phase change paraffin is (85-90):(5-8):(2-10).

[0033] In the above scheme, the phase change paraffin is commercially available paraffin with a phase change temperature of 60-70℃.

[0034] The microbial additive preparation method described above specifically includes the following:

[0035] Take 10-15 μL of *Bacillus pseudostrongylus* and place it in 1-1.5 portions of culture medium. Incubate at 30-35°C for 24-28 hours to obtain a bacterial suspension containing *Bacillus*. Centrifuge at 4000-6000 rpm for 10-20 minutes at 5-10°C to remove the supernatant and water, obtaining a concentrated bacterial suspension. The bacterial concentration in the concentrated bacterial suspension is 10-1. 8 ~10 9The microbial additive is prepared by adding 300-400 mL of calcium lactate and 100-150 mL of yeast extract to 100-150 mL of concentrated bacterial solution, then adding distilled water to a final volume of 1 L and mixing thoroughly. The concentration of calcium lactate is 4.5-5.0 g / L, and the concentration of yeast extract is 8.0-10.0 g / L. The culture medium consists of: 4.5-5.0 g soybean protein, 5.0-6.0 g yeast extract, 8-10 g glucose, 0.8-1.0 g K₂HPO₄, 0.15-0.2 g MgSO₄·7H₂O, 4.8-5.0 g NaCl, 9.8-10.2 g Na₂CO₃, and 1.0-1.1 L distilled water.

[0036] The preparation method of the above-mentioned low-carbon, crack-resistant, self-healing mass concrete includes the following steps:

[0037] (1) Weigh each raw material according to the above components. Each component and its mass fraction include: 300-450 parts of active adhesive, 60-100 parts of other adhesive, 680-750 parts of fine aggregate, 1030-1100 parts of coarse aggregate, 155-165 parts of water, and 7-11 parts of high-performance additive.

[0038] (2) Mix the active adhesive, other adhesives and high-performance admixtures evenly in sequence; then add coarse aggregate, fine aggregate and water in sequence and stir continuously for 2-3 minutes. After molding and curing, the low-carbon crack-resistant self-healing large-volume concrete is obtained; the fine aggregate in the fine aggregate and the mineralized self-healing phase change coarse aggregate in the coarse aggregate are pre-absorbed with water for 30-40 minutes before stirring.

[0039] Compared with existing technologies, the beneficial effects of this invention are:

[0040] (1) The low-carbon crack-resistant self-healing mass concrete provided by the present invention has the advantages of excellent strength, low shrinkage, excellent crack resistance and impermeability, and self-healing function of cracks, which can effectively improve the service performance of mass concrete.

[0041] (2) This invention provides a method for preparing low-carbon, crack-resistant, self-healing large-volume concrete. The preparation method is simple and suitable for widespread application.

[0042] (3) This invention can ensure the strength index of large-volume concrete by using active adhesives in combination with other adhesives. At the same time, the addition of fly ash and mineral powder can effectively reduce the heat of hydration in the early stage of large-volume concrete. In addition, the heat of hydration inhibitor added to the high-performance admixture can further effectively reduce the heat of hydration in the early stage of large-volume concrete, and the addition of other adhesives can also reduce the heat of hydration. The other activated adhesives also have a synergistic effect on the strength of large-volume concrete in the later stage. Among them, the lignosulfonate added during the treatment of other adhesives can not only improve the mechanical activation efficiency during the grinding process, but also the surfactant properties of its linear polymer can play a water-reducing role in the preparation of internal curing fine aggregates and subsequent application in large-volume concrete, which synergistically enhances the water-reducing effect with the high-performance polycarboxylate superplasticizer.

[0043] (4) In this invention, the expansive internal curing fine aggregate is combined with the shrinkage reducer in the high-performance admixture. First, the internal curing fine aggregate is pre-saturated with water, which can provide water source for the later hydration of the cementitious material of large volume concrete and reduce drying shrinkage. At the same time, the shrinkage reducer and the internal curing fine aggregate have a dual shrinkage reduction effect, which can effectively improve the shrinkage resistance of large volume concrete and reduce the generation of shrinkage cracks.

[0044] (5) In this invention, the mineralized self-healing phase change coarse aggregate introduces phase change paraffin as an outer solidification shell. At room temperature, it is solid, which can protect the stability of the microbial community. After the mineral carbonization treatment, its mechanical properties are effectively improved. In addition, when the temperature rises to 60-70℃ during the pouring and curing of large-volume concrete, the phase change paraffin can melt from solid to liquid, which can effectively consume the internal heat of the large-volume concrete and reduce the internal temperature rise rate. At the same time, after melting the phase change paraffin, the microbial community is gradually released. During the service of the large-volume concrete, the microbial community contained therein can produce CaCO3 precipitate after a certain period of time, thereby reducing the generation of internal cracks, improving internal density, and achieving self-healing effect. Meanwhile, the microbial additives in the internal curing fine aggregate treatment process not only improve the crushing performance of fine aggregate during the granulation preparation of fine aggregate, but also provide microbial community incorporation in the subsequent large-volume concrete, promoting the improvement of internal density.

[0045] (6) The preparation process of other adhesives and aggregates in this invention consumes a large amount of solid waste, such as granite sawdust, recycled micro powder, recycled stone, etc. Among them, the mineralization process of mineralized self-healing phase change coarse aggregate can effectively absorb CO2. That is, the preparation method provided by this invention can absorb both solid waste and CO2, thus achieving the effect of carbon reduction and emission reduction. Detailed Implementation

[0046] The technical solution of the present invention will be described in detail below with reference to specific embodiments. However, the described embodiments are only some embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0047] In the embodiments and comparative examples of the present invention, some commercially available raw material information is shown in Table 1.

[0048] Table 1 Raw Material Information

[0049]

[0050] The present invention discloses a method for preparing low-carbon, crack-resistant, self-healing mass concrete, comprising the following steps:

[0051] (1) Weigh each raw material according to the components. Each component and its mass fraction include: 340-440 parts of active adhesive, 60-100 parts of other adhesive, 680-750 parts of fine aggregate, 1030-1100 parts of coarse aggregate, 155-165 parts of water, and 7-11 parts of high-performance admixture.

[0052] (2) Mix the active adhesive, other adhesives and high-performance admixtures evenly in sequence; then add coarse aggregate, fine aggregate and water in sequence and stir continuously for 3 minutes. After molding and curing, low-carbon crack-resistant self-healing large-volume concrete is obtained; the fine aggregate in the internal curing fine aggregate and the coarse aggregate in the mineralized self-healing phase change coarse aggregate are pre-absorbed with water for 30 minutes before stirring.

[0053] The active adhesive is a mixture of cement, fly ash, and mineral powder; other adhesives are a mixture of granite sawdust and treated recycled micro powder in a mass ratio of 1:1; fine aggregate is a mixture of sand and internally cured fine aggregate; coarse aggregate is a mixture of crushed stone and mineralized self-healing phase change coarse aggregate; the high-performance admixture is a composite admixture, a mixture of high-performance polycarboxylate superplasticizer powder, hydration heat inhibitor, and shrinkage reducer.

[0054] Granite sawdust is the tailings from granite cuttings. It has a SiO2 content of 75%, a loss on ignition of 1.5%, a 28-day activity index of 80%, and a particle size range of 10–75 μm.

[0055] The preparation method of other adhesive materials is as follows: mix granite sawdust, treated recycled micro powder and added grinding aid and ball mill for 40 minutes to obtain other adhesive materials; wherein the added grinding aid is lignin sulfonate, and its mass is 0.06% of the total mass of granite sawdust and treated recycled micro powder.

[0056] The specific preparation method of the treated recycled micro powder includes the following: during the process of preparing recycled aggregate from waste concrete, fine particles with a particle size of less than 75 μm are screened to obtain initial recycled micro powder. The initial recycled micro powder is added to water to form a slurry with a slurry concentration of 300 g / L. The temperature of the slurry is controlled at 60℃, and carbon dioxide gas is introduced into the slurry for stirring and carbonization for 2 hours. After filtration and drying, the treated recycled micro powder is obtained. The carbon dioxide gas is industrial waste gas with a CO2 content of 95%.

[0057] The preparation method of the internal curing fine aggregate includes the following steps: Granite sawdust, treated recycled micro-powder, composite expansion agent, alkali activator, and NaOH are mixed and granulated into balls. The mixture is then treated in a 500MHz microwave environment for 30 minutes. Ceramsite with a particle size of 0-5mm is screened, and the mixture is cured at 95%-100% RH and 35±5℃ for 7 days, followed by natural curing for 21 days to obtain the internal curing fine aggregate. The composition of the internal curing fine aggregate, per 100 parts by weight, includes: 20 parts granite sawdust, 30 parts treated recycled micro-powder, 30 parts composite expansion agent, 8 parts alkali activator, 2 parts NaOH, and the remainder is water. The composite expansion agent consists of MgO, CaO, and Ca4Al6SO4. 16 A mixture of MgO, CaO and Ca4Al6SO4 16 The mass ratio is 40:40:20; the alkali activator is a water glass solution with a modulus of 2.8, and the NaOH is commercially available industrial flake NaOH with a purity of 99.9%.

[0058] The specific methods for preparing mineralized self-healing phase change coarse aggregates include the following:

[0059] S1, fine particles with a particle size of 4.75 to 20 mm are taken during the process of preparing recycled aggregate from waste concrete to obtain core material;

[0060] S2, other adhesive materials, microbial additives, alkali activators, and NaOH are mixed and stirred evenly to obtain the shell material; the core material obtained in step S1 is placed in a granulator and the shell material is added while water is sprayed, and the mixture is granulated and then cured at 60℃ and 90%~99%RH for 14 days to obtain self-healing coarse aggregate; the mass ratio of core material to shell material is 1:3; the mass ratio of other adhesive materials, microbial additives, alkali activators, and NaOH in the shell material is 70:5:20:5.

[0061] S3, Place the self-healing coarse aggregate obtained in step S2 in a CO2 curing chamber for 10 hours. The curing conditions are 85% RH, temperature of 25-30℃, and CO2 pressure of 0.1-0.2 MPa. After taking it out, place it in the air for 28 days to obtain mineralized self-healing coarse aggregate.

[0062] S4. The mineralized self-healing coarse aggregate obtained in step S3 is placed in the microbial additive and adsorbed under a negative pressure of 40 kPa for 20 min. Then it is placed in molten phase change paraffin and adsorbed under a negative pressure of 100 kPa in a constant temperature water bath at 85 ± 5℃ for 60 min. After cooling to room temperature, it is taken out and air-dried to obtain the mineralized self-healing phase change coarse aggregate. The mass ratio of the mineralized self-healing coarse aggregate, the microbial additive and the phase change paraffin is 90:5:5.

[0063] The specific methods for preparing the above-mentioned microbial additives include the following:

[0064] 10 μL of *Bacillus pseudostrongylus* was placed in one culture medium and incubated at 35°C for 24 hours to obtain a bacterial suspension. The suspension was then centrifuged at 6000 rpm for 10 minutes at 5°C to remove the supernatant and water, yielding a concentrated bacterial suspension with a bacterial cell concentration of 10⁻⁶. 8 ~10 9 The microbial additive is prepared by adding 300 mL of calcium lactate and 100 mL of yeast extract to 100 mL of concentrated bacterial solution and mixing them evenly. The concentration of calcium lactate is 5.0 g / L and the concentration of yeast extract is 10 g / L. The culture medium consists of: 5.0 g soybean protein, 5.0 g yeast extract, 10 g glucose, 1.0 g K2HPO4, 0.2 g MgSO4·7H2O, 5.0 g NaCl, 10.2 g Na2CO3, and 1 L distilled water.

[0065] High-performance admixtures are mainly composite admixtures, which are prepared by uniformly mixing high-performance polycarboxylate superplasticizer powder, hydration heat inhibitor, and shrinkage reduction agent in a ratio of 1:1:0.2.

[0066] The raw material composition of the low-carbon crack-resistant self-healing mass concrete prepared in Examples 1-6 and the ordinary mass concrete prepared in Comparative Examples 1-4 of this invention is shown in Table 2.

[0067] Table 2 Raw material ratios for Examples 1-6 and Comparative Examples 1-4 (kg / m³) 3 )

[0068]

[0069] The low-carbon, crack-resistant, self-healing mass concrete samples prepared in Examples 1-6 and the ordinary mass concrete samples prepared in Comparative Examples 1-4 were subjected to relevant performance tests. The test results are shown in Table 3 below. The test methods used were as follows: 28-day autogenous shrinkage rate was detected according to the non-contact method in Part 8 of the "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete" (GBT 50082-2009); the total crack area per unit area was detected according to Part 9 of the "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete" (GBT50082-2009); and the electrical flux was tested using the rapid electrical flux determination method in the electrical flux test section of the "Technical Specification for Construction of Highway Bridges and Culverts" (JTG / T F502011). Core sampling, wax sealing, and vacuum saturation of the samples were performed at 28 days of age.

[0070] Table 3. Performance data of the large-volume concrete prepared in the examples and comparative examples.

[0071]

[0072] Table 3 shows that the compressive strength of concrete in Examples 1-6 is basically stable and not much different from that in the comparative example, indicating that the added binders have good activity and can provide good later strength. At the same time, the data on the highest internal temperature of concrete shows that the synergistic effect of other binders, mineralized self-healing phase change coarse aggregate, and hydration heat inhibitor can effectively reduce the internal temperature rise of concrete. Analysis of the autogenous shrinkage rate, electrical flux, and crack resistance (total crack area per unit area) data shows that the autogenous shrinkage of concrete in the examples is significantly reduced compared with the comparative example, indicating that the internal curing effect of the internal curing fine aggregate and the synergistic effect of its micro-expansion characteristics and shrinkage reduction agent have played a good role. From the electrical flux data, the internal density of the low-carbon crack-resistant mass concrete prepared in the examples is significantly better than that of ordinary mass concrete, and the crack resistance is also improved simultaneously.

[0073] Examples 2 and 4, and comparative examples 2 and 4, were selected for comparison of self-healing capabilities. The test results are shown in Table 4 below. The testing method used was the self-healing width testing method: after the molded test blocks were cured for 28 days, cracks were created using a universal testing machine. Gaskets with dimensions of 10mm × 10mm × 0.3mm were pasted at the four corners of one specimen cross-section. The two cross-sections were then combined in their original positions and fixed in the middle of the fixture, followed by curing for self-healing.

[0074] Table 4 Self-healing capability test data

[0075]

[0076] As can be seen from the data in Table 4, the low-carbon crack-resistant self-healing mass concrete prepared by introducing mineralized self-healing phase change coarse aggregate and internally cured fine aggregate can better repair cracks through self-healing. However, the data from the comparative example shows that its crack recovery effect is not obvious. That is, the mineralized self-healing phase change coarse aggregate and internally cured fine aggregate introduced in this invention have a better repair effect on cracks in mass concrete.

[0077] In summary, the low-carbon, crack-resistant, self-healing mass concrete provided by this invention has advantages such as excellent strength, low shrinkage, excellent crack resistance and impermeability, and self-healing function, which can effectively improve the service performance of mass concrete; at the same time, the preparation method is simple and suitable for widespread application.

[0078] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A low-carbon, crack-resistant, self-healing large-volume concrete, characterized in that, By mass, it includes the following components: 340-440 parts of active adhesive material; Other adhesive materials: 60-100 parts; Fine aggregate 680-750 parts; 1030~1100 parts of coarse aggregate; 155-165 parts water; 7-11 parts of high-performance admixture; The active adhesive material is a mixture of cement, fly ash and mineral powder; The other adhesive material is a mixture of granite sawdust and treated recycled micro powder; the fine aggregate is a mixture of sand and internal curing fine aggregate; the coarse aggregate is a mixture of crushed stone and mineralized self-healing phase change coarse aggregate. The high-performance admixture is a composite admixture, which is a mixture of high-performance polycarboxylate superplasticizer powder, hydration heat inhibitor and shrinkage reducer; The preparation method of the internally cured fine aggregate specifically includes the following: granite sawdust, treated recycled micro powder, composite expansion agent, alkali activator, and NaOH are mixed into pellets and granulated, then placed in a 300~500MHz microwave environment for 30~40min, ceramsite with a particle size of 0~5mm is screened, and then cured at 95%~100%RH and 35±5℃ for 7d, and then naturally cured for 21d to obtain the internally cured fine aggregate; The composition of the internal curing fine aggregate, based on 100 parts by weight, includes: 10-20 parts granite sawdust, 20-30 parts treated recycled micro powder, 20-30 parts composite expansion agent, 5-8 parts alkali activator, 1-3 parts NaOH, and the balance being water. The composite expanding agent is composed of MgO, CaO, and Ca4Al6SO4. 16 A mixture of MgO, CaO and Ca4Al6SO4 16 The mass ratio is (20~40):(30~50):(10~20); The alkali activator is a water glass solution with a modulus of 2.8 to 3.0; the preparation method of the mineralized self-healing phase change coarse aggregate specifically includes the following: S1, fine particles with a particle size of 4.75~20mm are taken during the process of preparing recycled aggregate from waste concrete to obtain core material; S2, take the other adhesive materials, microbial additives, alkali activator and NaOH, mix them and stir evenly to obtain shell material; place the core material obtained in step S1 in a granulator and add the shell material while spraying water, form granules, and then place it in a temperature of 40~60℃ and 90%~99%RH for 7-14 days to obtain self-healing coarse aggregate. S3, Place the self-healing coarse aggregate obtained in step S2 in a CO2 curing chamber for 8~10 hours, with curing conditions of 80%~85%RH, temperature of 20~30℃, and CO2 pressure of 0.1~0.2Mpa; After taking it out, place it in the air for 28 days to obtain mineralized self-healing coarse aggregate; S4. The mineralized self-healing coarse aggregate obtained in step S3 is placed in a microbial additive and adsorbed under a negative pressure of 30~40Kpa for 10~20min. Then it is placed in molten phase change paraffin and adsorbed under a negative pressure of 80~100Kpa in a constant temperature water bath at 80~90℃ for 40~60min. After cooling to room temperature, it is taken out and air-dried to obtain the mineralized self-healing phase change coarse aggregate.

2. The low-carbon, crack-resistant, self-healing mass concrete according to claim 1, characterized in that, The active adhesive contains 260-340 parts by weight of cement, and 80-100 parts by weight of fly ash and mineral powder; the cement is PO 42.5 cement, the fly ash is grade I or II fly ash, and the mineral powder is grade S95 or S105 mineral powder.

3. The low-carbon, crack-resistant, self-healing mass concrete according to claim 1, characterized in that, The specific preparation method of the treated recycled micro powder includes the following: during the process of preparing recycled aggregate from waste concrete, fine particles with a particle size of less than 75 μm are screened to obtain initial recycled micro powder. The initial recycled micro powder is added to water to form a slurry, wherein the slurry concentration is 200~300 g / L; the temperature of the slurry is controlled at 60~80℃, and carbon dioxide gas is introduced into the slurry for stirring and carbonization for 1~2 hours. After filtration and drying, the treated recycled micro powder is obtained; wherein the carbon dioxide gas is industrial waste gas with a CO2 content of 80%~95%.

4. The low-carbon, crack-resistant, self-healing mass concrete according to claim 1, characterized in that, The preparation method of the other adhesive material specifically includes the following: mixing granite sawdust and treated recycled micro powder and ball milling for 30-40 minutes to obtain the other adhesive material; during the ball milling process, an external grinding aid is added, which is lignin sulfonate, and its mass is 0.06%-0.12% of the total mass of granite sawdust and treated recycled micro powder; The mass ratio of granite sawdust to treated recycled micro powder in the other adhesive materials is 1:(1~2); the granite sawdust is granite cutting tailings with a SiO2 content of 70%~80%, a loss on ignition of 1.0~1.8%, a 28-day activity index of 75%~80%, and a particle size range of less than 75um.

5. The low-carbon, crack-resistant, self-healing mass concrete according to claim 1, characterized in that, The mass ratio of sand to internal curing fine aggregate in the fine aggregate is (60~50):(40~50); the sand is either ordinary manufactured sand or river sand.

6. The low-carbon, crack-resistant, self-healing mass concrete according to claim 1, characterized in that, In the preparation method of the mineralized self-healing phase change coarse aggregate: The mass ratio of the core material to the shell material is 1:(2~3); the mass ratio of other adhesives, microbial additives, alkali activators, and NaOH in the shell material is (60~70):(3~5):(20~25):(3~5); The mass ratio of mineralized self-healing coarse aggregate, microbial additive and phase change paraffin is (85~90): (5~8): (2~10).

7. The low-carbon, crack-resistant, self-healing mass concrete according to claim 1, characterized in that, The method for preparing the microbial additive specifically includes the following: Take 10-15 μL of *Bacillus pseudostrongylus* and place it in 1-1.5 portions of culture medium. Incubate at 30-35°C for 24-28 hours to obtain a bacterial suspension containing *Bacillus*. Centrifuge at 4000-6000 rpm for 10-20 minutes at 5-10°C to remove the supernatant and water, obtaining a concentrated bacterial suspension. The bacterial concentration in the concentrated bacterial suspension is 10-1. 8 ~10 9 The microbial additive is prepared by adding 300-400 mL of calcium lactate and 100-150 mL of yeast extract to 100-150 mL of concentrated bacterial solution, then adding distilled water to a final volume of 1 L and mixing thoroughly. The concentration of calcium lactate is 4.5-5.0 g / L, and the concentration of yeast extract is 8.0-10.0 g / L. The culture medium consists of: 4.5-5.0 g soybean peptone, 5.0-6.0 g yeast extract, 8-10 g glucose, 0.8-1.0 g K2HPO4, 0.15-0.2 g MgSO4•7H2O, 4.8-5.0 g NaCl, 9.8-10.2 g Na2CO3, and 1.0-1.1 L distilled water.

8. The low-carbon, crack-resistant, self-healing mass concrete according to claim 1, characterized in that, The mass ratio of crushed stone and mineralized self-healing phase change coarse aggregate in the coarse aggregate is (60~75):(25~40); the mass ratio of high-performance polycarboxylate superplasticizer powder, hydration heat inhibitor, and shrinkage reducer in the high-performance admixture is 1:(0.8~1.0):(0.1~0.2).

9. The method for preparing low-carbon, crack-resistant, self-healing mass concrete according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Weigh each raw material according to the above components. Each component and its mass fraction include: 300-450 parts of active adhesive, 60-100 parts of other adhesive, 680-750 parts of fine aggregate, 1030-1100 parts of coarse aggregate, 155-165 parts of water, and 7-11 parts of high-performance additive. (2) Mix the active adhesive, other adhesives and high-performance admixtures evenly in sequence; then add coarse aggregate, fine aggregate and water in sequence and stir continuously for 2-3 minutes. After molding and curing, the low-carbon crack-resistant self-healing large-volume concrete is obtained; the fine aggregate in the fine aggregate and the mineralized self-healing phase change coarse aggregate in the coarse aggregate are pre-absorbed with water for 30-40 minutes before stirring.

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