Ecological concrete and preparation method thereof

Abstract

The invention relates to the technical field of low-alkalinity concrete, and discloses ecological concrete and a preparation method thereof, and the preparation method comprises the following steps: acid treatment of alkaline coarse aggregate, molding of macroporous concrete, carbonization curing, implantation of a high-strength hollow plastic pipe in concrete pores, coating on the surface of the concrete, and the like. According to the invention, concrete water is used as a soak solution for acid treatment of alkaline coarse aggregate, a sodium carbonate solution is used for maintenance, and plant fiber, high-volume superfine mineral powder and water granulated slag sand are used as fine aggregate. The overall alkalinity of the concrete is reduced while the mechanical properties of the concrete are not reduced by reducing the alkalinity of the aggregate, reducing the alkalinity of the cementing material, reducing the alkalinity of the curing environment and blocking the transmission of alkalinity inside and outside the concrete through the rubber powder, the epoxy resin, the coating and the like.

Description

Technical Field

[0001] This invention relates to the field of low-alkalinity concrete technology, and in particular to an eco-friendly concrete and its preparation method. Background Technology

[0002] Ecological concrete is an environmentally friendly type of concrete that balances structural performance with ecological functions. Its characteristics include porosity, permeability, and the ability to support plant root growth or purify (adsorb pollutants). However, traditional concrete, due to its high alkalinity (pH value typically above 12.5), inhibits seed germination and root growth, and affects microbial activity, thus limiting its application in areas requiring symbiosis with plants, such as ecological slope protection and green walls. To address this issue, researchers have recently conducted research on ecological concrete from multiple aspects, including material selection, mix design, and chemical modification.

[0003] Currently, the alkali reduction technology for eco-friendly concrete mainly employs the following techniques: (1) Use low-alkali or modified cementitious materials (such as low-alkali sulfoaluminate cement, low-alkali cement mixed with blast furnace slag).

[0004] (2) Use acidic or buffering substances to neutralize alkalinity (such as adding aluminum sulfate to modified ecological concrete test blocks, or using substances such as aluminum dihydrogen phosphate).

[0005] (3) Utilize industrial solid waste (such as lithium slag, fly ash, mineral powder, etc.) to partially replace cement in order to reduce the calcium hydroxide produced by cement hydration. For example, the existing patent CN119118555A has attempted to use lithium slag powder as an admixture or to prepare alkali aggregate inhibitors to reduce the alkalinity of concrete and improve its compressive strength and impermeability.

[0006] There is also a patent CN202311010012.8 that improves the density and wear resistance of concrete and effectively reduces shrinkage by incorporating components such as magnesium fluorosilicate and aluminum dihydrogen phosphate.

[0007] However, existing technologies still face many challenges. First, relying solely on large amounts of mineral admixtures can reduce the early strength of concrete, prolong setting time, and result in slow alkalinity reduction. Second, introduced chemical additives may cause rapid setting, false setting, or affect later strength development, and their compatibility and long-term stability with the cement system need to be considered. Furthermore, there is a contradiction between reducing alkalinity and maintaining the required mechanical properties, durability, and pore structure suitable for plant root growth in concrete.

[0008] Therefore, developing an eco-friendly concrete that can synergistically achieve low alkalinity, suitable pore structure, good mechanical properties and long-term durability, while ensuring that its preparation process is simple and cost-controllable, has become an urgent problem to be solved in this field.

[0009] Patent CN202411287131.2 discloses a modified porous ecological concrete. By using coarse aggregate and sulfoaluminate cement as the main components, and adding modified diatomaceous earth, modified porous ceramsite, modified fiber components, etc., a modified porous ecological concrete with high strength and low alkalinity is obtained. It has been applied to slope protection projects with good results.

[0010] Patent CN202110021451.3 discloses a low-alkalinity concrete for vegetation based on recycled construction waste, comprising the following components by mass percentage: 20%–30% coarse construction waste particles, 10%–30% fine construction waste particles, 20%–30% paper sludge ceramsite, 10%–30% cement, 0.1%–0.5% admixtures, 0.05%–0.15% potassium dihydrogen phosphate, 0.5%–1.0% ethylene glycol tert-butyl ether, and 0.04%–0.1% polypropylene carbonate polyol. By optimizing the concrete's components, its alkalinity can be effectively reduced, with a pH below 10. Utilizing the porous structure of the paper sludge ceramsite improves its permeability and aeration, thus facilitating the penetration of water and nutrients required for plant growth. Adding potassium dihydrogen phosphate as a buffer has two advantages. First, potassium dihydrogen phosphate, when dissolved in water, forms a weakly acidic solution that can neutralize the alkali produced during cement hydration, thereby reducing the alkalinity of the concrete and making it more suitable for plant growth. Second, potassium dihydrogen phosphate can provide the concrete with phosphorus and potassium elements suitable for plant growth. Furthermore, potassium dihydrogen phosphate reacts with calcium hydroxide, a product of cement hydration, to produce calcium phosphate, calcium hydrogen phosphate, tripotassium phosphate, dipotassium hydrogen phosphate, etc., depending on the specific ratio, thus providing phosphorus, potassium, and calcium elements for plant growth.

[0011] Patent CN202311719222.4 discloses a lithium slag cementitious material that replaces part of the cement with lithium slag, improving the overall mechanical properties of concrete. The addition of lithium slag surrounds the cement particles, hindering their reaction with water and slowing down the hydration reaction, thereby reducing heat release and preventing early cracking caused by excessive internal heat in the concrete. Furthermore, the active components in the lithium slag continuously consume the hydration product calcium hydroxide, providing long-term alkali reduction protection.

[0012] Patent CN202310566299.6 discloses a modified eco-concrete based on chitosan-biochar polymer. The key component, chitosan-biochar polymer, is obtained by mixing, stirring, drying, grinding, and sieving natural plant-derived biochar and chitosan in an acetic acid solution. The modified eco-concrete exhibits high compressive strength, well-developed pore structure, excellent water and fertilizer retention, significant vegetation coverage, and outstanding water purification performance. After forming a film, the chitosan can physically prevent the release of internal alkaline ions, and the large surface area of ​​the biochar also facilitates the release of metal ions and OH groups. - It has a strong adsorption and fixation effect. Summary of the Invention

[0013] Purpose of the invention: To address the problems existing in the prior art, this invention provides an eco-friendly concrete and its preparation method, which solves the problems of high alkalinity in traditional concrete and its unfavorable effect on plant growth.

[0014] Technical solution: On the one hand, the present invention provides a method for preparing eco-friendly concrete, comprising the following steps: S1. Coarse aggregate pretreatment: Alkaline coarse aggregate with a particle size of less than 10 mm is soaked in an acidic solution with a concentration of 0.1~2.0% by mass for 5~48 hours, and then air-dried until there is no visible water on the surface; the alkaline coarse aggregate is aggregate with CaO as the main component; S2. Forming large-pore concrete: Concrete is poured into a porous mold to form large-pore concrete; wherein, the pores of the large-pore concrete are interconnected pores, the coarse aggregate used in the large-pore concrete is the pretreated coarse aggregate in S1, and the large-pore concrete also contains plant fibers with a length of 10mm~20mm. S3. Carbonation curing: After demolding the macroporous concrete obtained in S2, immerse it in a sodium carbonate solution or a composite solution of sodium carbonate and sodium silicate with a pH of 9-12 for 1-3 days. S4. Inserting high-strength hollow plastic tubes into concrete holes: After carbonization curing, the large-hole concrete obtained in S3 is dried, and epoxy resin is applied to the inner surface of the large holes of the large-hole concrete. Then, a hollow plastic tube of the same size as the large hole is vertically inserted into the large hole. S5. Apply a coating to the concrete surface obtained in S4 to obtain eco-friendly concrete.

[0015] Further, in S1, the acidic solution is one or more of hydrochloric acid, sulfuric acid, or nitric acid solution.

[0016] Furthermore, in S1, the alkaline aggregate is one of limestone, dolomite, or marble.

[0017] Further, in S2, the concrete is composed of the following components in parts by weight: 100-150 parts cement clinker, 100-200 parts ultrafine mineral powder, 5-10 parts gypsum, 80-100 parts nickel-iron slag powder, 1200-1400 parts coarse aggregate, 600-700 parts fine aggregate, 3-5 parts plant fiber, 3-5 parts adhesive powder, 4-6 parts water-reducing agent, and 135-150 parts water.

[0018] Furthermore, the water is the soaking solution after soaking the alkaline coarse aggregate in S1. When using the solution, the pH value of the soaking solution is adjusted to 8-9 by one or two of sodium silicate and sodium carbonate.

[0019] Furthermore, the specific surface area of ​​the ultrafine mineral powder is 400~700m². 2 / kg.

[0020] Furthermore, the fine aggregate is water-slag sand.

[0021] Furthermore, in S1, the alkaline aggregate is one of limestone, dolomite, or marble.

[0022] Furthermore, in S4, the specific drying conditions are: drying temperature: 50~60°C; drying time: 1~3 hours.

[0023] On the other hand, the present invention provides an eco-friendly concrete prepared by the method described in any of the above claims.

[0024] Beneficial Effects: This invention utilizes concrete water as an acid-treated soaking solution for alkaline coarse aggregates, employs sodium carbonate solution for curing, and uses plant fibers, high-volume ultrafine mineral powder, and slag sand as fine aggregates. Through aggregate-based alkali reduction, cementitious material-based alkali reduction, curing environment-based alkali reduction, and the use of adhesive powder, epoxy resin, and coatings to seal alkali transport inside and outside the concrete, the overall alkalinity of the concrete is reduced without compromising its mechanical properties. Compared with existing technologies, the specific beneficial effects are as follows: 1. Soaking alkaline aggregates in an acidic solution has two main effects. First, the acid will corrode the smooth surface of the aggregates, making them tougher and improving the bonding strength between cement paste and recycled aggregates. Second, after acid treatment, the aggregate surface becomes weakly acidic, and small amounts of calcium chloride, calcium nitrate, and calcium sulfate products generated by the reaction between the acid and the aggregates will be present on the aggregate surface. This provides conditions for the nucleation and rapid reaction of hydration products.

[0025] 2. The soaking solution of acid-treated aggregates is used as an aqueous solution. The aqueous solution is weakly acidic. At the same time, the calcium chloride, calcium nitrate and calcium sulfate products produced by the reaction of acid with aggregates can accelerate the hydration reaction of cement. In addition, after adjusting the pH value of the soaking solution with sodium silicate, sodium carbonate and other substances, these silicates and carbonates will react with free calcium ions in the soaking solution to form nano-sized calcium silicate and calcium carbonate products. These nano-sized products will act as nucleation sites to accelerate cement hydration.

[0026] 3. Adding plant fibers to concrete can improve its crack resistance, but plant fibers have poor alkali resistance. The eco-concrete provided by this invention is weakly alkaline, thus the plant fibers have higher durability. Furthermore, the large pores in the concrete and the hollow pores of the plant fibers can provide CO3 for carbonation curing. 2- The transport pathway of (carbonate) further consumes calcium hydroxide in the concrete; in addition, the sodium carbonate solution in the curing liquid can also react with ultrafine mineral powder and other substances to form new hydration products, which fill the pores inside the concrete.

[0027] 4. Drying at 50-60 degrees Celsius accelerates the hydration reaction of the cementitious materials and reduces the amount of water remaining in the pores of the concrete after the cement reaction, preventing the leakage of alkaline solutions. Epoxy resin can be used to seal the small pores on the walls of large-pore concrete, thus inhibiting the leakage of residual calcium hydroxide. Simultaneously, high-strength hollow plastic tubes of the same size as the pores are pre-installed in the large pores. These tubes are bonded to the concrete with epoxy resin. When the concrete is subjected to vertical compressive stress, the hollow plastic tubes prevent lateral deformation in the horizontal direction, acting as a hooping effect, improving the mechanical properties of the concrete, and also preventing the alkaline erosion of plants by calcium hydroxide in the concrete.

[0028] 5. By using low amounts of cement clinker and high amounts of ultrafine mineral powder and nickel-iron slag powder, the calcium hydroxide in the cement is consumed more quickly. At the same time, water slag sand is used as fine aggregate to further consume the alkali in the system in the later stage. The alkali transmission channels are blocked internally with adhesive powder and externally with coatings to reduce the leakage of alkali in cement concrete. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the embodiments. Implementation method 1:

[0030] This embodiment provides a method for preparing eco-friendly concrete, the specific steps of which are as follows: S1. Coarse aggregate pretreatment: Immerse alkaline coarse aggregate with a particle size of 5.0-10.0 mm in a 1.5% hydrochloric acid solution for 24 hours, and then air dry until the surface is free of water; the above alkaline coarse aggregate is limestone aggregate; S2. Molded large-pore concrete: Concrete is poured into a porous mold to form large-pore concrete; wherein, the concrete is composed of the following components by weight: 120 parts cement clinker, 100 parts ultrafine mineral powder, 7 parts gypsum, 90 parts nickel-iron slag powder, 1250 parts coarse aggregate (coarse aggregate after pretreatment in S1), 650 parts fine aggregate, 4 parts plant fiber, 4 parts adhesive powder, 4 parts water-reducing agent, and 140 parts water. The pores in the aforementioned large-pore concrete are interconnected; the length of the aforementioned plant fiber is 10 mm; the water used is the soaking solution after soaking the alkaline coarse aggregate in S1, and the pH value of the soaking solution is adjusted to 8 with a 5% sodium silicate solution before use; the specific surface area of ​​the aforementioned ultrafine mineral powder is 400 m². 2 / kg; The above fine aggregate is water-slag sand; S3. Carbonation curing: After demolding, the macroporous concrete obtained in S2 is immersed in a sodium carbonate solution with a pH of 9 for 1 day for carbonation curing to obtain porous concrete specimens. S4. Hollow plastic tubes are inserted into the concrete holes: The porous concrete specimens obtained in S3 are dried at 50°C for 1 hour. Then, epoxy resin is applied to the inner surface of the large holes of the porous concrete specimens, and high-strength hollow plastic tubes (PE material) of the same size as the large holes are vertically inserted into the large holes. S5. Apply a cement-based penetrating crystalline coating to the surface of the concrete obtained in S4 to obtain eco-friendly concrete. Implementation Method 2:

[0031] This embodiment provides a method for preparing eco-friendly concrete, the specific steps of which are as follows: S1. Coarse aggregate pretreatment: Immerse alkaline coarse aggregate with a particle size of 5.0-10.0 mm in a 0.1% sulfuric acid solution for 12 hours, and then air dry until the surface is free of water; the above alkaline coarse aggregate is dolomite aggregate; S2. Molded macroporous concrete: Concrete is poured into a porous mold to form macroporous concrete; wherein the concrete is composed of the following components in parts by weight: 130 parts cement clinker, 180 parts ultrafine mineral powder, 6 parts gypsum, 85 parts nickel-iron slag powder, 1350 parts coarse aggregate (coarse aggregate after pretreatment in S1), 680 parts fine aggregate, 3.5 parts plant fiber, 3.5 parts adhesive powder, 5 parts water-reducing agent, and 145 parts water; The pores in the aforementioned large-pore concrete are interconnected; the length of the aforementioned plant fiber is 20 mm; the water used is the soaking solution after soaking the alkaline coarse aggregate in S1, and the pH value of the soaking solution is adjusted to 9 with a 6% sodium carbonate solution before use; the specific surface area of ​​the aforementioned ultrafine mineral powder is 600 m². 2 / kg; The above fine aggregate is water-slag sand; S3. Carbonation curing: After demolding, the macroporous concrete obtained in S2 is immersed in a sodium carbonate solution with a pH of 10 for 2 days for carbonation curing to obtain porous concrete specimens. S4. Hollow plastic tubes are inserted into the concrete holes: The porous concrete specimens obtained in S3 are dried at 55°C for 2 hours. Then, epoxy resin is applied to the inner surface of the large holes of the porous concrete specimens, and high-strength hollow plastic tubes (PE material) of the same size as the large holes are vertically inserted into the large holes. S5. Apply a cement-based penetrating crystalline coating to the surface of the concrete obtained in S4 to obtain eco-friendly concrete. Implementation Method 3:

[0032] This embodiment provides a method for preparing eco-friendly concrete, the specific steps of which are as follows: S1. Coarse aggregate pretreatment: Alkaline coarse aggregate with a particle size of 5.0-10.0 mm is soaked in a 2.0% nitric acid solution for 48 hours and then air-dried until the surface is free of water; the above-mentioned alkaline coarse aggregate is marble aggregate; S2. Molded macroporous concrete: Concrete is poured into a porous mold to form macroporous concrete; wherein, the concrete is composed of the following components in parts by weight: 140 parts cement clinker, 160 parts ultrafine mineral powder, 8 parts gypsum, 95 parts nickel-iron slag powder, 1300 parts coarse aggregate (coarse aggregate after pretreatment in S1), 620 parts fine aggregate, 4.5 parts plant fiber, 4 parts adhesive powder, 6 parts water-reducing agent, and 138 parts water; The pores in the aforementioned large-pore concrete are interconnected; the length of the aforementioned plant fiber is 15 mm; the water used is the soaking solution after soaking the alkaline coarse aggregate in S1, and the pH value of the soaking solution is adjusted to 9 with a 3% sodium silicate and 5% sodium carbonate compound solution before use; the specific surface area of ​​the aforementioned ultrafine mineral powder is 700 m² / g. 2 / kg; The above fine aggregate is water-slag sand; S3. Carbonation curing: After demolding, the macroporous concrete obtained in S2 is immersed in a composite solution with a pH of 12, which is prepared by mixing sodium carbonate and sodium silicate in a mass ratio of 1:1, for 3 days to carry out carbonation curing and obtain porous concrete specimens. S4. Hollow plastic tubes are inserted into the concrete holes: The porous concrete specimens obtained in S3 are dried at 60°C for 1 hour. Then, epoxy resin is applied to the inner surface of the large holes of the porous concrete specimens, and high-strength hollow plastic tubes (PE material) of the same size as the large holes are vertically inserted into the large holes. S5. Apply a cement-based penetrating crystalline coating to the surface of the concrete obtained in S4 to obtain eco-friendly concrete. Implementation Method 4:

[0033] This embodiment provides a method for preparing eco-friendly concrete, the specific steps of which are as follows: S1. Coarse aggregate pretreatment: Alkaline coarse aggregate with a particle size of 5-10mm is soaked in a 1.0% mass fraction mixed solution of hydrochloric acid and sulfuric acid (mixing ratio of 1:1) for 36 hours, and then air-dried until the surface is free of water; the above alkaline coarse aggregate is recycled aggregate from limestone; S2. Molded macroporous concrete: Concrete is poured into a porous mold to form macroporous concrete; wherein, the concrete is composed of the following components in parts by weight: 100 parts cement clinker, 190 parts ultrafine mineral powder, 5 parts gypsum, 80 parts nickel-iron slag powder, 1400 parts coarse aggregate (coarse aggregate after pretreatment in S1), 700 parts fine aggregate, 3 parts plant fiber, 5 parts adhesive powder, 5 parts water-reducing agent, and 150 parts water. The pores in the aforementioned large-pore concrete are interconnected; the length of the aforementioned plant fiber is 10 mm; the water used is the soaking solution after soaking the alkaline coarse aggregate in S1, and the pH value of the soaking solution is adjusted to 9 with a 5% sodium silicate solution before use; the specific surface area of ​​the aforementioned ultrafine mineral powder is 600 m² / g. 2 / kg; The above fine aggregate is water-slag sand; S3. Carbonation curing: After demolding, the macroporous concrete obtained in S2 is immersed in a sodium carbonate solution with a pH of 12 for 2 days for carbonation curing to obtain porous concrete specimens. S4. Hollow plastic tubes are inserted into the concrete holes: The porous concrete specimens obtained in S3 are dried at 55°C for 3 hours. Then, epoxy resin is applied to the inner surface of the large holes of the porous concrete specimens, and high-strength hollow plastic tubes (PE material) of the same size as the large holes are vertically inserted into the large holes. S5. Apply a cement-based penetrating crystalline coating to the surface of the concrete obtained in S4 to obtain eco-friendly concrete. Implementation Method 5:

[0034] This embodiment provides a method for preparing eco-friendly concrete, the specific steps of which are as follows: S1. Coarse aggregate pretreatment: Alkaline coarse aggregate with a particle size of 5.0-10.0 mm is soaked in a mixed solution of hydrochloric acid and nitric acid with a mass fraction of 0.8% (mixing ratio of 2:1) for 5 hours, and then air-dried until the surface is free of water; the above alkaline coarse aggregate is a compound aggregate of limestone and dolomite in a mass ratio of 1:1. S2. Molded large-pore concrete: Concrete is poured into a porous mold to form large-pore concrete; wherein, the concrete is composed of the following components in parts by weight: 150 parts cement clinker, 200 parts ultrafine mineral powder, 10 parts gypsum, 100 parts nickel-iron slag powder, 1200 parts coarse aggregate (coarse aggregate after pretreatment in S1), 600 parts fine aggregate, 5 parts plant fiber, 3 parts adhesive powder, 5 parts water-reducing agent, and 135 parts water. The pores in the aforementioned large-pore concrete are interconnected; the length of the aforementioned plant fiber is 20 mm; the water used is the soaking solution after soaking the alkaline coarse aggregate in S1, and the pH value of the soaking solution is adjusted to 9 with a sodium silicate and sodium carbonate compound solution (mass ratio 2:1) before use; the specific surface area of ​​the aforementioned ultrafine mineral powder is 600 m². 2 / kg; The above fine aggregate is water-slag sand; S3. Carbonation curing: After demolding, the macroporous concrete obtained in S2 is immersed in a sodium silicate and sodium carbonate compound solution (mass ratio 2:1) with a pH value of 11 for 2 days to carry out carbonation curing, and a porous concrete specimen is obtained. S4. Hollow plastic tubes are inserted into the concrete holes: The porous concrete specimens obtained in S3 are dried at 55°C for 1 hour. Then, epoxy resin is applied to the inner surface of the large holes of the porous concrete specimens, and high-strength hollow plastic tubes (PE material) of the same size as the large holes are vertically inserted into the large holes. S5. Apply a cement-based penetrating crystalline coating to the surface of the concrete obtained in S4 to obtain eco-friendly concrete. Comparative Example 1 (Blank Control Group):

[0035] Ordinary ecological concrete, by weight, comprises the following components: 400 parts PO 42.5 cement, 1300 parts 5-10mm continuously graded crushed stone, 650 parts medium sand, 145 parts water, and 5 parts polycarboxylate superplasticizer. Its preparation process is as follows: cement, crushed stone, and sand are dry-mixed evenly, then water and superplasticizer are added and stirred to form a mixture. The concrete mixture is then poured into a porous mold and compacted using a vibrating table. The specimens are demolded and then cured under standard conditions (temperature 20±2°C, humidity ≥95%) for 28 days. Performance testing

[0036] Table 1 shows the performance evaluation indicators and testing methods of this invention. pH value test method: After the concrete has been cured for 28 days, it is crushed, and the internal sample is ground and passed through a 0.15mm sieve. Weigh 10g of powder and mix it with 50ml of deionized water (water-to-solid ratio 5:1). Stir magnetically for 5 minutes and let it stand for 24 hours. Take the supernatant and measure it with a precision pH meter.

[0037] Compressive strength: The compressive strength of a 100mm×100mm×100mm cube specimen at 28 days of age was tested according to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T 50081).

[0038] Plant compatibility: After 28 days of curing, concrete test blocks were placed in seedling trays, and 100 Bermuda grass seeds were evenly sown in the large holes of the concrete. After 28 days of cultivation in an artificial climate chamber (temperature 25°C, humidity 70%), the number of germinated seeds was counted and the germination rate was calculated.

[0039]

[0040] As shown in Table 1, the present invention has the following advantages: 1. Excellent alkalinity reduction and ecological compatibility: As shown in Table 1, the five embodiments of the present invention successfully stabilized the pH value of the concrete pore liquid in the weakly alkaline range of 10.2-10.7, which is far lower than the 12.8 of Comparative Example 1. More importantly, the present invention achieved a plant germination rate of 95%-98%. 2. Excellent mechanical properties: While achieving low alkalinity and high germination rate, the 28-day compressive strength of the embodiments of the present invention remained at a high level of 40.8-45.3 MPa, higher than that of the comparative example, meeting the strength requirements of ecological slope protection, vegetated block engineering, and other projects.

[0041] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing eco-friendly concrete, characterized in that, Includes the following steps: S1. Coarse aggregate pretreatment: Alkaline coarse aggregate with a particle size of less than or equal to 10 mm is soaked in an acidic solution with a concentration of 0.1~2.0% by mass for 5~48 hours, and then air-dried until there is no visible water on the surface; the alkaline coarse aggregate is aggregate with CaO as the main component; S2. Forming large-pore concrete: Concrete is poured into a porous mold to form large-pore concrete; wherein, the pores of the large-pore concrete are interconnected pores, the coarse aggregate used in the large-pore concrete is the pretreated coarse aggregate in S1, and the large-pore concrete also contains plant fibers with a length of 10mm~20mm. S3. Carbonation curing: After demolding the macroporous concrete obtained in S2, immerse it in a sodium carbonate solution or a composite solution of sodium carbonate and sodium silicate with a pH of 9-12 for 1-3 days. S4. Inserting high-strength hollow plastic tubes into concrete holes: After carbonization curing, the large-hole concrete obtained in S3 is dried, and epoxy resin is applied to the inner surface of the large holes of the large-hole concrete. Then, a hollow plastic tube of the same size as the large hole is vertically inserted into the large hole. S5. Apply a coating to the concrete surface obtained in S4 to obtain eco-friendly concrete.

2. The method for preparing eco-friendly concrete according to claim 1, characterized in that: In S1, the acidic solution is one or more of hydrochloric acid, sulfuric acid, or nitric acid solution.

3. The method for preparing eco-friendly concrete according to claim 1, characterized in that: In S1, the alkaline aggregate is one or more of limestone, dolomite, and marble.

4. The method for preparing eco-friendly concrete according to claim 1, characterized in that: In S2, the concrete is composed of the following components in parts by weight: 100-150 parts cement clinker, 100-200 parts ultrafine mineral powder, 5-10 parts gypsum, 80-100 parts nickel-iron slag powder, 1200-1400 parts coarse aggregate, 600-700 parts fine aggregate, 3-5 parts plant fiber, 3-5 parts adhesive powder, 4-6 parts water-reducing agent, and 135-150 parts water.

5. The method for preparing eco-friendly concrete according to claim 4, characterized in that: The water is the soaking solution after soaking alkaline coarse aggregate in S1. When using it, the pH value of the soaking solution is adjusted to 8-9 by one or two of sodium silicate and sodium carbonate.

6. The method for preparing eco-friendly concrete according to claim 4, characterized in that: The specific surface area of ​​the ultrafine mineral powder is 400~700m². 2 / kg.

7. The method for preparing eco-friendly concrete according to claim 4, characterized in that: The fine aggregate is water-slag sand.

8. The method for preparing eco-friendly concrete according to claim 1, characterized in that: In S1, the alkaline aggregate is one of limestone, dolomite, or marble.

9. The method for preparing eco-friendly concrete according to claim 1, characterized in that: In S4, the specific drying conditions are: drying temperature: 50~60°C; drying time: 1~3 hours.

10. An eco-friendly concrete prepared by the method according to any one of claims 1-9.

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