Method for preparing low-carbon concrete based on biochar

Abstract

The invention provides a preparation method of waste straw charcoal concrete, and belongs to the technical field of building materials. The concrete is prepared from Portland cement, waste straw biochar, low-calcium fly ash, coarse and fine aggregate, an additive and water, and all the components are mixed according to a specific proportion. The preparation process of the waste straw biochar comprises the steps of cleaning, drying, crushing and pyrolyzing. When the concrete is prepared, part of the raw materials are subjected to dry mixing, then the other raw materials are added and stirred in a CO2 environment, and carbonization curing and standard curing are performed after mold forming and preliminary curing demolding. Tests show that the method does not affect the compressive strength of the concrete, but significantly improves the carbon sequestration rate of the concrete, realizes resource utilization and efficient carbon sequestration of the waste straws, has the advantages of low carbon, environmental protection and mechanical properties, and has a good application prospect.

Description

Technical Field

[0001] The present invention provides a sustainable, low-carbon and environmentally friendly method for preparing low-carbon concrete based on waste straw biochar, which relates to the field of building materials technology. It can significantly improve the carbon sequestration efficiency of biochar concrete, and the physical and mechanical properties of the concrete remain stable. Background Art

[0002] In recent years, global CO2 emissions have continued to rise, posing severe challenges to the climate system and the ecological environment. As a key sector of carbon emissions, the building materials industry faces immense pressure and urgently needs to achieve a low-carbon transition through technological innovation. This is particularly true in concrete production and application. The development of low-carbon concrete has become a key direction for implementing national strategic goals and promoting the development of green building materials.

[0003] Currently, conventional concrete carbon sequestration technologies rely primarily on natural carbonation or the addition of industrial byproducts (such as mineral admixtures) to reduce carbon emissions during production. However, the natural carbonation process is limited by the diffusion dynamics within concrete pores, and the interaction between CO2 and concrete is typically limited to a depth of a few millimeters from the surface. This limits the volume of concrete involved in the carbonation reaction and reduces carbon capture efficiency. Therefore, developing new technologies and materials with more efficient carbon sequestration capabilities has become a top priority for the green development of the concrete industry.

[0004] With the continuous advancement of technology, emerging carbon capture and storage methods are moving towards active capture and efficient storage. For example, directly injecting CO2 during the concrete mixing stage, or performing CO2 curing after concrete is formed, these methods have made significant progress in improving carbon capture efficiency. In addition, biochar, as a stable carbon-rich solid material, has been widely recognized as an important carbon sequestration method because it has negative carbon emission characteristics due to its formation through the pyrolysis of biomass under anaerobic conditions. In terms of net greenhouse gas emission reduction, the stable carbon stored in biochar accounts for more than 50%, showing significant emission reduction benefits. The production of biochar can not only effectively reduce carbon emissions, but also provide a new solution for the development of low-carbon concrete by improving the physical and mechanical properties and carbon sequestration capacity of carbonized and cured concrete.

[0005] Therefore, the present invention provides a sustainable, low-carbon and environmentally friendly method for preparing low-carbon concrete based on waste straw biochar. This method can significantly improve the carbon sequestration efficiency of biochar concrete, and the physical and mechanical properties of the concrete remain stable. This technology not only realizes the resource utilization of waste straw, but also lays a solid foundation for the widespread application of waste straw biochar concrete in construction projects.

[0006] The technical solution of the present invention provides a sustainable, low-carbon and environmentally friendly method for preparing low-carbon concrete based on waste straw biochar. The technical solution of the present invention is as follows:

[0007] 1. The raw materials of waste straw biochar concrete include cement, waste straw biochar, fly ash, coarse aggregate, fine aggregate, admixtures and water. The main components of waste straw biochar concrete per cubic meter are:

[0008] (1) Cement: 300kg-350kg;

[0009] (2) Waste straw biochar: 15kg-25kg;

[0010] (3) Fly ash: 15kg-25kg;

[0011] (4) Fine aggregate: 620kg-680kg;

[0012] (5) Coarse aggregate: 1100kg-1250kg;

[0013] (6) Admixtures: 3kg-5kg of polycarboxylate water reducer and 0.25kg-0.5kg of hydroxypropyl methylcellulose;

[0014] (7) Water: 160kg-170kg.

[0015] 2. Furthermore, the cement is Portland cement with a strength grade of 42.5, 52.5 or 62.5.

[0016] 3. Furthermore, the waste straw biochar is waste corn straw or waste wheat straw.

[0017] 4. Furthermore, the preparation method of the waste straw biochar is as follows: first, the collected waste corn straw or wheat straw is washed with water, placed in a drying oven at 60°C and dried until constant weight is reached; then, it is crushed with a crusher and sieved into particles less than 0.6 mm; finally, the raw material is placed in a vacuum furnace, pyrolyzed at 400°C-600°C for 1.5h-2h at a heating rate of 10°C / min, and a cooling rate of 10°C / min-20°C / min, and then cooled to room temperature to obtain biochar.

[0018] 5. Furthermore, the fly ash is Class I or Class II low-calcium fly ash, with a CaO content (by mass percentage) of <3%.

[0019] 6. Furthermore, the fine aggregate is river sand with a fineness modulus of 2.3-2.9.

[0020] 7. Furthermore, the coarse aggregate is crushed stone with a particle size range of 5mm-31.5mm.

[0021] 8. Furthermore, the admixture is a polycarboxylate water-reducing agent with a water-reducing rate of >25%, and hydroxypropyl methylcellulose with a viscosity of 100,000 mPa·s-120,000 mPa·s.

[0022] 9. The method for preparing waste straw biochar concrete comprises the following steps: first, weigh the required cement, waste straw biochar, and fly ash, pour them into a blender, and stir for 60 seconds to thoroughly mix. Then, add the remaining raw materials and stir in a blender sealed with acrylic sheet in a CO2 atmosphere for 240 seconds. The CO2 gas has a purity of 90%-99.9%, a flow rate of 5L / min-10L / min, and a CO2 pressure of 0.5atm-2atm. Finally, pour the mixture into a 100mm×100mm×100mm mold, vibrate for 30s-60s, cover the test block with polyethylene film, and place it in a curing box at a temperature of (20±2)°C and a relative humidity of >95%. Curing for 24 hours is followed by demolding.

[0023] 10. The curing method of waste straw biochar concrete comprises the following steps: carbonization curing is adopted, with a CO2 gas purity of 90%-99.9%, a flow rate of 5L / min-10L / min, and a CO2 gas pressure of 0.5atm-2atm. After carbonization curing for 12 hours, the test blocks are placed in a curing box at a temperature of (20±2)°C and a relative humidity of >95% and cured to an age of 7 days and 28 days, respectively.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) For waste straw biochar concrete, the present invention proposes a new preparation method that does not affect the physical and mechanical properties of concrete.

[0026] (2) For waste straw biochar, the present invention proposes an efficient carbon sequestration method, which successfully realizes the resource utilization of solid waste materials, effectively reduces carbon emissions, and significantly improves the carbon sequestration rate of concrete. DETAILED DESCRIPTION

[0027] In order to further demonstrate the efficacy of the present invention, the present invention is further described in detail below with reference to specific application cases.

[0028] Example 1:

[0029] This embodiment provides a method for preparing waste corn straw biochar concrete.

[0030] The raw materials of waste corn straw biochar concrete include Portland cement, waste corn straw biochar, Class II low-calcium fly ash, river sand, crushed stone, polycarboxylate water reducer, hydroxypropyl methylcellulose and water. The main components of waste corn straw biochar concrete per cubic meter are:

[0031] (1) Portland cement: 300 kg;

[0032] (2) Waste corn straw biochar: 15 kg;

[0033] (3) Grade II low calcium fly ash: 15 kg;

[0034] (4) River sand: 620 kg;

[0035] (5) Crushed stone: 1240 kg;

[0036] (6) Polycarboxylate water reducer: 3 kg;

[0037] (7) Hydroxypropyl methylcellulose: 0.25 kg;

[0038] (8) Water: 160 kg.

[0039] The strength grade of silicate cement is 42.5, the CaO content (by mass percentage) of Grade II low-calcium fly ash is 2.9%, the fineness modulus of river sand is 2.3, the particle size range of crushed stone is 5mm-20mm, the water reduction rate of polycarboxylate superplasticizer is 29%, and the viscosity of hydroxypropyl methylcellulose is 100,000mPa·s.

[0040] ① The preparation method of waste corn straw biochar includes the following steps:

[0041] First, the collected waste corn stalks were washed with water and dried in a drying oven at 60°C until they reached constant weight. Then, they were crushed with a crusher and sieved into particles less than 0.6 mm in size. Finally, the raw materials were placed in a vacuum furnace and pyrolyzed at 500°C for 1.5 h at a heating rate of 10°C / min and a cooling rate of 15°C / min. Biochar was obtained after cooling to room temperature.

[0042] ② The preparation method of waste corn straw biochar concrete includes the following steps:

[0043] First, the required amount of Portland cement, waste corn straw biochar, and Grade II low-calcium fly ash were weighed and poured into a blender for 60 seconds to thoroughly mix. The remaining raw materials were then added and stirred for 240 seconds in a blender sealed with acrylic sheet in a CO2 atmosphere with a purity of 90%, a flow rate of 5 L / min, and a pressure of 1 atm. Finally, the mixture was poured into a 100 mm × 100 mm × 100 mm mold and vibrated for 60 seconds. The test block was then covered with polyethylene film and placed in a curing chamber at (20 ± 2)°C and a relative humidity > 95%. Cured for 24 hours before demolding.

[0044] ③The curing method of waste corn straw biochar concrete includes the following steps:

[0045] Carbonization curing was adopted, with a CO2 gas purity of 99.9%, a flow rate of 5 L / min, and a CO2 gas pressure of 1 atm. After carbonization curing for 12 hours, the specimens were placed in a curing box with a temperature of (20±2)°C and a relative humidity of >95% and cured to the ages of 7 days and 28 days, respectively.

[0046] Example 2:

[0047] This embodiment provides a method for preparing waste corn straw biochar concrete.

[0048] The raw materials of waste corn straw biochar concrete include Portland cement, waste corn straw biochar, Class I low-calcium fly ash, river sand, crushed stone, polycarboxylate water reducer, hydroxypropyl methylcellulose and water. The main components of waste corn straw biochar concrete per cubic meter are:

[0049] (1) Portland cement: 350 kg;

[0050] (2) Waste corn straw biochar: 25 kg;

[0051] (3) Class I low calcium fly ash: 25 kg;

[0052] (4) River sand: 680kg;

[0053] (5) Crushed stone: 1100 kg;

[0054] (6) Polycarboxylate water reducer: 5kg;

[0055] (7) Hydroxypropyl methylcellulose: 0.5 kg;

[0056] (8) Water: 170 kg.

[0057] The strength grade of Portland cement is 42.5, the CaO content (by mass percentage) of Grade I low-calcium fly ash is 2.7%, the fineness modulus of river sand is 2.9, the particle size range of crushed stone is 5mm-31.5mm, the water reduction rate of polycarboxylate superplasticizer is 29%, and the viscosity of hydroxypropyl methylcellulose is 100,000mPa·s.

[0058] ① The preparation method of waste corn straw biochar includes the following steps:

[0059] First, the collected waste corn stalks were washed with water and dried in a drying oven at 60°C until they reached constant weight. Then, they were crushed with a crusher and sieved into particles less than 0.6 mm in size. Finally, the raw materials were placed in a vacuum furnace and pyrolyzed at 500°C for 1.5 h at a heating rate of 10°C / min and a cooling rate of 15°C / min. Biochar was obtained after cooling to room temperature.

[0060] ② The preparation method of waste corn straw biochar concrete includes the following steps:

[0061] First, the required amount of Portland cement, waste corn straw biochar, and Grade I low-calcium fly ash were weighed and poured into a blender for 60 seconds to thoroughly mix. The remaining raw materials were then added and stirred in an acrylic-sealed blender under CO2 gas for 240 seconds. The CO2 gas was 99.9% pure, at a flow rate of 5 L / min and a pressure of 1 atm. Finally, the mixture was poured into a 100 mm × 100 mm × 100 mm mold and vibrated for 60 seconds. The test piece was then covered with polyethylene film and placed in a curing chamber at (20 ± 2)°C and a relative humidity > 95%. Cured for 24 hours before demolding.

[0062] ③The curing method of waste corn straw biochar concrete includes the following steps:

[0063] Carbonization curing was adopted, with a CO2 gas purity of 99.9%, a flow rate of 5 L / min, and a CO2 gas pressure of 1 atm. After carbonization curing for 12 hours, the specimens were placed in a curing box with a temperature of (20±2)°C and a relative humidity of >95% and cured to the ages of 7d and 28d.

[0064] Example 3:

[0065] This embodiment provides a method for preparing waste corn straw biochar concrete.

[0066] The raw materials of waste corn straw biochar concrete include Portland cement, waste corn straw biochar, Class II low-calcium fly ash, river sand, crushed stone, polycarboxylate water reducer, hydroxypropyl methylcellulose and water. The main components of waste corn straw biochar concrete per cubic meter are:

[0067] (1) Portland cement: 330 kg;

[0068] (2) Waste corn straw biochar: 20 kg;

[0069] (3) Grade II low calcium fly ash: 20 kg;

[0070] (4) River sand: 650kg;

[0071] (5) Crushed stone: 1165 kg;

[0072] (6) Polycarboxylate water reducer: 4.5 kg;

[0073] (6) Hydroxypropyl methylcellulose: 0.3 kg;

[0074] (7) Water: 165 kg.

[0075] The strength grade of silicate cement is 42.5, the CaO content (by mass percentage) of Grade II low-calcium fly ash is 2.9%, the fineness modulus of river sand is 2.5, the particle size range of crushed stone is 5mm-25mm, the water reduction rate of polycarboxylate water reducer is 29%, and the viscosity of hydroxypropyl methylcellulose is 100,000 mPa·s.

[0076] ① The preparation method of waste corn straw biochar includes the following steps:

[0077] First, the collected waste corn stalks were washed with water and dried in a drying oven at 60°C until they reached constant weight. Then, they were crushed with a crusher and sieved into particles less than 0.6 mm in size. Finally, the raw materials were placed in a vacuum furnace and pyrolyzed at 600°C for 2 h at a heating rate of 10°C / min and a cooling rate of 15°C / min. Biochar was obtained after cooling to room temperature.

[0078] ② The preparation method of waste corn straw biochar concrete includes the following steps:

[0079] First, the required amount of Portland cement, waste corn straw biochar, and Grade II low-calcium fly ash were weighed and poured into a blender for 60 seconds to thoroughly mix. The remaining raw materials were then added and stirred for 240 seconds in a blender sealed with acrylic sheet in a CO2 atmosphere with a purity of 95%, a flow rate of 10 L / min, and a pressure of 1 atm. Finally, the mixture was poured into a 100 mm × 100 mm × 100 mm mold and vibrated for 60 seconds. The test block was then covered with polyethylene film and placed in a curing chamber at (20 ± 2)°C and a relative humidity > 95%. Cured for 24 hours before demolding.

[0080] ③The curing method of waste corn straw biochar concrete includes the following steps:

[0081] Carbonization curing was adopted, with a CO2 gas purity of 95%, a flow rate of 10 L / min, and a CO2 gas pressure of 1 atm. After carbonization curing for 12 hours, the specimens were placed in a curing box with a temperature of (20±2)°C and a relative humidity of >95% and cured to the ages of 7d and 28d.

[0082] Example 4:

[0083] This embodiment provides a method for preparing waste wheat straw biochar concrete.

[0084] The raw materials of waste wheat straw biochar concrete include Portland cement, waste wheat straw biochar, Class I low-calcium fly ash, river sand, crushed stone, polycarboxylate water reducer, hydroxypropyl methylcellulose and water. The main components of waste wheat straw biochar concrete per cubic meter are:

[0085] (1) Portland cement: 320 kg;

[0086] (2) Waste wheat straw biochar: 25 kg;

[0087] (3) Class I low calcium fly ash: 25 kg;

[0088] (4) River sand: 640 kg;

[0089] (5) Crushed stone: 1175 kg;

[0090] (6) Polycarboxylate water reducer: 4 kg;

[0091] (7) Hydroxypropyl methylcellulose: 0.35 kg;

[0092] (8) Water: 165 kg.

[0093] The strength grade of Portland cement is 42.5, the CaO content (by mass percentage) of Grade I low-calcium fly ash is 2.7%, the fineness modulus of river sand is 2.4, the particle size range of crushed stone is 5mm-30mm, the water reduction rate of polycarboxylate superplasticizer is 29%, and the viscosity of hydroxypropyl methylcellulose is 100,000mPa·s.

[0094] ① The preparation method of waste wheat straw biochar comprises the following steps:

[0095] First, the collected waste wheat straw was washed with water and dried in a drying oven at 60°C until it reached constant weight; then, it was crushed with a crusher and sieved into particles less than 0.6 mm; finally, the raw material was placed in a vacuum furnace and pyrolyzed at 500°C for 1.5 h at a heating rate of 10°C / min, with a cooling rate of 15°C / min, and biochar was obtained after cooling to room temperature.

[0096] ② The preparation method of waste wheat straw biochar concrete includes the following steps:

[0097] First, the required amount of Portland cement, waste wheat straw biochar, and Class I low-calcium fly ash were weighed and poured into a blender. Stir for 60 seconds to thoroughly mix. The remaining raw materials were then added and stirred in an acrylic-sealed blender under CO2 for 240 seconds. The CO2 gas was 90% pure, at a flow rate of 5 L / min, and at a pressure of 1 atm. Finally, the mixture was poured into a 100 mm × 100 mm × 100 mm mold and vibrated for 60 seconds. The specimen was then covered with polyethylene film and placed in a curing chamber at (20 ± 2)°C and a relative humidity > 95%. Cured for 24 hours before demolding.

[0098] ③The curing method of waste wheat straw biochar concrete includes the following steps:

[0099] Carbonization curing was adopted, with a CO2 gas purity of 90%, a flow rate of 5 L / min, and a CO2 gas pressure of 1 atm. After carbonization curing for 12 hours, the specimens were placed in a curing box with a temperature of (20±2)°C and a relative humidity of >95% and cured to the ages of 7d and 28d.

[0100] Example 5: Blank control group, no waste straw biochar

[0101] This embodiment provides a method for preparing concrete.

[0102] The raw materials of concrete include Portland cement, Class I low-calcium fly ash, river sand, crushed stone, polycarboxylate water reducer, hydroxypropyl methylcellulose and water. The main components of each cubic meter of concrete are:

[0103] (1) Portland cement: 300 kg;

[0104] (2) Class I low-calcium fly ash: 25 kg;

[0105] (3) River sand: 670 kg;

[0106] (4) Crushed stone: 1195 kg;

[0107] (5) Polycarboxylate water reducer: 5 kg;

[0108] (6) Hydroxypropyl methylcellulose: 0.25 kg;

[0109] (7) Water: 160 kg.

[0110] The strength grade of Portland cement is 42.5, the CaO content (by mass percentage) of Grade I low-calcium fly ash is 2.7%, the fineness modulus of river sand is 2.4, the particle size range of crushed stone is 5mm-30mm, the water reduction rate of polycarboxylate superplasticizer is 29%, and the viscosity of hydroxypropyl methylcellulose is 100,000mPa·s.

[0111] First, the required amount of Portland cement and Grade I low-calcium fly ash was weighed and poured into a blender. Mixing was then completed for 60 seconds to thoroughly mix. The remaining raw materials were then added and stirred for 240 seconds in a blender sealed with acrylic sheet in the presence of 99.9% pure CO2 at a flow rate of 5 L / min and a pressure of 1 atm. Finally, the mixture was poured into a 100 mm × 100 mm × 100 mm mold and vibrated for 60 seconds. The specimens were then covered with polyethylene film and placed in a curing chamber at (20 ± 2)°C and a relative humidity of >95%. Cured for 24 hours before demolding. Carbonation curing was employed with 99.9% pure CO2 at a flow rate of 5 L / min and a pressure of 1 atm. After carbonization curing for 12 hours, the specimens were placed in a curing chamber at (20 ± 2)°C and a relative humidity of >95% for 7 and 28 days, respectively.

[0112] Test results

[0113] The compressive strength of each experimental group was measured according to GB / T 50081-2019, "Standard for Test Methods of Physical and Mechanical Properties of Concrete." Carbon retention was determined by oven-drying the tested concrete at 105°C to constant weight. The sample was then ground using a vibrating mill and its weight loss rate was measured using a TG-DSC thermal analyzer at temperatures between 600°C and 900°C. The carbon retention in the concrete was then calculated. The test parameters used were a dry air atmosphere, a temperature range of 30°C to 900°C, and a heating rate of 10°C / min. The results for the compressive strength and carbon retention of each concrete group are shown in Table 1.

[0114] Table 1 Compressive strength (MPa) and carbon sequestration rate (%) of waste straw biochar concrete

[0115] Group number Carbon-fixing materials 7d 28d Carbon sequestration rate Example 1 corn stalks 27.3 38.2 25.4 Example 2 corn stalks 28.7 40.4 29.5 Example 3 corn stalks 27.1 39.8 26.3 Example 4 wheat straw 27.9 41.0 29.6 Blank control group none 29.4 40.6 11.2

[0116] As shown in Table 1, under similar mix ratios, the compressive strength of concrete containing waste straw biochar was similar to that of the control group without biochar at 7 and 28 days. However, the addition of waste straw biochar significantly increased the carbon sequestration rate in concrete. The carbon sequestration rates in Examples 1-4 all exceeded 25%, more than double that of the control group.

[0117] In summary, the present invention provides a method for preparing waste straw biochar concrete. This method does not affect the compressive strength of concrete, but significantly improves the carbon fixation rate of concrete, realizes the resource utilization of waste straw and efficient carbon sequestration, and has the advantages of low carbon environmental protection and mechanical properties, and has good application prospects.

Claims

1. A waste straw biochar concrete, characterized by: The raw materials include cement, waste straw biochar, fly ash, coarse aggregate, fine aggregate, admixtures and water; the components of each cubic meter of waste straw biochar concrete are: (1) Cement: 300kg-350kg; (2) Waste straw biochar: 15kg-25kg; (3) Fly ash: 15kg-25kg; (4) Fine aggregate: 620kg-680kg; (5) Coarse aggregate: 1100kg-1250kg; (6) Admixtures: 3kg-5kg of acrylic acid-based high-efficiency water reducer and 0.25kg-0.5kg of hydroxypropyl methylcellulose; (7) Water: 160kg-170kg.

2. The waste straw biochar concrete according to claim 1, characterized in that: The cement is silicate cement with a strength grade of 42.5, 52.5 or 62.

5.

3. The waste straw biochar concrete according to claim 1, characterized in that: The waste straw biochar is waste corn straw or waste wheat straw.

4. The waste straw biochar concrete according to claim 1, characterized in that: The waste straw biochar preparation method comprises the following steps: first, washing the collected waste corn straw or wheat straw with water, placing the collected waste corn straw or wheat straw in a drying oven at 60°C and drying the waste straw at 60°C until a constant weight is reached; then, crushing the waste straw with a crusher and sieving the waste straw into particles with a size of less than 0.6 mm; finally, placing the raw material in a vacuum furnace, pyrolyzing the waste straw at 400°C-600°C for 1.5h-2h at a heating rate of 10°C / min, cooling the waste straw at a cooling rate of 10°C / min-20°C / min, and cooling the waste straw to room temperature to obtain biochar.

5. The waste straw biochar concrete according to claim 1, characterized in that: The fly ash is Class I or Class II low-calcium fly ash, and the CaO content is less than 3% by mass.

6. The waste straw biochar concrete according to claim 1, characterized in that: The fine aggregate is river sand with a fineness modulus of 2.3-2.

9.

7. The waste straw biochar concrete according to claim 1, characterized in that: The coarse aggregate is crushed stone with a particle size range of 5mm-31.5mm.

8. The waste straw biochar concrete according to claim 1, characterized in that: The admixtures are polycarboxylic acid water-reducing agent with a water-reducing rate of more than 25% and hydroxypropyl methylcellulose with a viscosity of 100,000 mPa·s-120,000 mPa·s.

9. The method for preparing waste straw biochar concrete according to claim 1, characterized in that: The preparation steps are as follows: First, the required amount of cement, waste straw biochar, and fly ash were weighed and poured into a blender for 60 seconds to thoroughly mix. The remaining raw materials were then added and stirred in a blender sealed with acrylic sheet for 240 seconds in a CO2 atmosphere. The CO2 gas purity was 90%-99.9%, the flow rate was 5L / min-10L / min, and the CO2 pressure was 0.5atm-2atm. Finally, the mixture was poured into a 100mm×100mm×100mm mold and vibrated for 30-60 seconds. The test block was then covered with polyethylene film and placed in a curing chamber at (20±2)°C and a relative humidity of >95%. Cured for 24 hours before demolding.

10. The method for curing the waste straw biochar concrete according to claim 1, characterized in that: The maintenance steps are as follows: Carbonization curing was adopted, with CO2 gas purity of 90%-99.9%, flow rate of 5L / min-10L / min, CO2 gas pressure of 0.5atm-2atm. After carbonization curing for 12h, the specimens were placed in a curing box with a temperature of (20±2)℃ and relative humidity>95% and cured to the age of 7d and 28d respectively.