Cementing material based on solid waste and preparation method thereof

Abstract

The invention relates to the technical field of concrete cementing material preparation, in particular to a cementing material based on solid waste and a preparation method thereof.The cementing material is prepared from, by mass, 27-35 parts of red mud, 34-46 parts of slag, 5-30 parts of carbide slag, 10-25 parts of ardealite and 10-18 parts of modified biochar; the modified biochar is obtained through cellulose pyrolysis, and the biochar obtained through pyrolysis is treated through epichlorohydrin, DMF and diethylenetriamine. When being used for curing, the prepared cementing material is high in fluidity, easy to mix, high in compressive strength and breaking strength in 3, 7 and 28 days, lower in heavy metal leaching rate than the national standard and small in environmental harm.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of concrete cementitious materials, and specifically to a waste-based cementitious material and a preparation method thereof. Background Art

[0002] A large amount of energy is consumed and a large amount of carbon dioxide is emitted during the production process of traditional cement, which causes a serious burden on the environment. In recent years, geopolymers, as a kind of low-carbon and environmentally friendly building material, have received extensive attention due to their low energy consumption, low carbon dioxide emissions and low cost.

[0003] Red mud, phosphogypsum and carbide slag are a large amount of solid waste generated during industrial production. At present, their utilization rate is low, and long-term stacking causes serious pollution to the environment. How to effectively use these solid wastes to prepare high-performance cementitious materials without adding commercial alkali activators has become a research hotspot in the field of building materials.

[0004] Therefore, in view of the problems raised in the present invention, those skilled in the art propose to prepare a cementitious material with red mud, slag and carbide slag as the basic materials. At the same time, in view of the defects existing in the solid waste materials themselves, such as poor fluidity and low overall strength of the material after gelling, the problem is further solved by adding modified biochar. Summary of the Invention

[0005] The purpose of the present invention is to provide a waste-based cementitious material and a preparation method thereof to solve the problems raised in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A waste-based cementitious material comprises the following components by mass: 27-35 parts of red mud, 34-46 parts of slag, 5-30 parts of carbide slag, 10-25 parts of phosphogypsum, and 10-18 parts of modified biochar;

[0008] The preparation method of the modified biochar comprises the following steps:

[0009] S101: Dispersing cellulose into a sodium hydroxide solution with a concentration of 0.5-2 mol / L, soaking for 0.2-1 h, centrifuging and separating, washing the product with sufficient deionized water, and then freeze-drying at -30 to -70 °C for 12-24 h;

[0010] S102: Dispersing the cellulose treated in step S101 into a mixed solution of ammonium dihydrogen phosphate and sodium bicarbonate, soaking for 1-2 h, centrifuging and filtering, and vacuum drying at 20-30 °C;

[0011] S103. Pyrolyze the cellulose processed in step S102 under a nitrogen atmosphere. After pyrolysis is completed, grind it through a 500 - 800 mesh sieve to obtain biochar;

[0012] S104. Immerse the biochar obtained in step S103 in hydrochloric acid with a concentration of 5 - 8 mol / L for 6 - 10 h. After washing with sufficient deionized water, vacuum dry it at 30 - 50 °C;

[0013] S105. Put the biochar processed in step S104 into a mixed solution of epichlorohydrin and DMF, heat it up to 70 - 90 °C and react for 0.5 - 1 h, then dropwise add diethylenetriamine and continue to react for 1 - 2 h. Filter the product, wash it with sufficient deionized water, and vacuum dry it at 30 - 50 °C to obtain modified biochar.

[0014] Further, the mass ratio between the cellulose and the sodium hydroxide solution in step S101 is 1:(15 - 25).

[0015] Further, the concentration of ammonium dihydrogen phosphate in step S102 is 0.1 - 2 mol / L, the concentration of sodium bicarbonate is 0.5 - 1 mol / L, and the mass ratio between the cellulose processed in step S101 and the mixed solution of ammonium dihydrogen phosphate and sodium bicarbonate is 1:(30 - 50).

[0016] Further, the pyrolysis temperature in step S103 is 800 - 1000 °C, and the pyrolysis time is 3 - 6 h.

[0017] Further, the mass ratio between the biochar and hydrochloric acid in step S104 is 1:(12 - 20).

[0018] Further, the mass ratio between epichlorohydrin, DMF, diethylenetriamine and the biochar processed in step S104 is (3 - 5):(2 - 7):(1 - 2):1.

[0019] A preparation method of a gelling material based on solid waste, comprising the following steps:

[0020] S1. Calcinate red mud and slag at 800 - 1000 °C for 2 - 4 h in proportion, and dry carbide slag and phosphogypsum at 100 - 150 °C;

[0021] S2. Put the red mud and slag processed in step S1 into a mixed solution of 3 - mercaptopropyltrimethoxysilane and isopropanol, stir and process for 2 - 10 h. Filter the product, wash it with sufficient absolute ethanol, and vacuum dry it at 20 - 40 °C;

[0022] S3. Immerse the red mud and slag treated in step S2 into hydrogen peroxide solution with a mass fraction of 30%, react at 40 - 70 °C for 0.5 - 2 h, and vacuum dry the filtered product at 20 - 40 °C;

[0023] S4. Put the slag and red mud treated in step S3, the carbide slag, phosphogypsum and modified biochar treated in step S1 into a blender and stir for 20 min to obtain a cementitious material.

[0024] Further, the mass ratio of the sum of the mass of the red mud and slag to 3 - mercaptopropyltrimethoxysilane and isopropanol in step S2 is 1:(1 - 3):(8 - 10).

[0025] Further, the mass ratio of the sum of the mass of the red mud and slag to hydrogen peroxide in step S3 is 1:(5 - 8).

[0026] Compared with the prior art, the effects of the present invention are as follows:

[0027] 1. The main materials in the present invention include red mud, carbide slag and slag, which can meet the preparation of the cementitious material for concrete, and effectively solve the problem that solid waste is inconvenient to utilize;

[0028] 2. Modified biochar is also added in the present invention. The addition of modified biochar effectively improves the fluidity of the mixture and the mixing effect. As a cementitious material, its compressive and flexural strengths at 3, 7, and 28 d are relatively high;

[0029] 3. When the cementitious material prepared in the present invention is cured, the heavy metal leaching rate of its cured product is far lower than the national standard, and it has little harm to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the process flow chart for preparing the cementitious material of the present invention;

[0031] Figure 2 is the process flow chart for preparing the modified biochar of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] Please refer to Figures 1 to 2 , the present invention provides:

[0034] Example 1

[0035] A preparation method of a solid waste-based cementitious material, comprising the following steps:

[0036] S1. Calcine 480 g of red mud and 615 g of slag at 950 °C for 2.5 h, and dry 240 g of carbide slag and 300 g of phosphogypsum at 110 °C;

[0037] S2. Put the red mud and slag treated in step S1 into a mixed solution of 3-mercaptopropyltrimethoxysilane and isopropanol and stir for 4 h. The dosages of 3-mercaptopropyltrimethoxysilane and isopropanol are 2.25 kg and 9.9 kg respectively. Wash the filtered product with sufficient anhydrous ethanol and vacuum dry at 30 °C;

[0038] S3. Immerse the red mud and slag treated in step S2 into 6.6 kg of hydrogen peroxide with a mass fraction of 30%, react at 45 °C for 1.8 h, and vacuum dry the filtered product at 30 °C;

[0039] S4. Put the slag and red mud treated in step S3, the carbide slag and phosphogypsum treated in step S1, and 165 g of modified biochar into a blender and stir for 20 min to obtain the cementitious material;

[0040] The preparation method of the above-mentioned modified biochar comprises the following steps:

[0041] S101. Disperse 1.08 kg of cellulose into 21.8 kg of sodium hydroxide solution with a concentration of 1 mol / L, soak for 0.8 h, centrifuge and separate. After washing the product with sufficient deionized water, freeze-dry at -45 °C for 15 h;

[0042] S102. Disperse 990 g of cellulose treated in step S101 into a mixed solution of 37.5 kg of ammonium dihydrogen phosphate and sodium bicarbonate, soak for 1.5 h, wherein the concentration of ammonium dihydrogen phosphate is 0.6 mol / L and the concentration of sodium bicarbonate is 0.8 mol / L. Centrifuge and filter and vacuum dry at 25 °C;

[0043] S103. Pyrolyze the cellulose treated in step S102 under a nitrogen atmosphere, the pyrolysis temperature is 900 °C, the pyrolysis time is 5 h, and after pyrolysis is completed, grind and pass through a 600-mesh sieve to obtain biochar;

[0044] S104. Immerse 225 g of the biochar obtained in step S103 into 4.05 kg of hydrochloric acid with a concentration of 6 mol / L and treat for 8 h. After washing with sufficient deionized water, vacuum dry at 40 °C;

[0045] S105. Put 195 g of biochar treated in step S104 into a mixed solution of 780 g of epichlorohydrin and 1.17 kg of DMF, heat up to 85 °C and react for 0.8 h, then dropwise add 293 g of diethylenetriamine and continue to react for 1.5 h. Filter the product, wash it with sufficient deionized water, and vacuum dry it at 40 °C to obtain modified biochar.

[0046] Example 2

[0047] A preparation method of a cementitious material based on solid waste, comprising the following steps:

[0048] S1. Calcinate 162 g of red mud and 204 g of slag at 800 °C for 2 h, and dry 30 g of carbide slag and 60 g of phosphogypsum at 100 °C.

[0049] S2. Put the red mud and slag treated in step S1 into a mixed solution of 3-mercaptopropyltrimethoxysilane and isopropanol and stir for 2 h. The dosages of 3-mercaptopropyltrimethoxysilane and isopropanol are 366 g and 2.92 kg respectively. Filter the product, wash it with sufficient absolute ethanol, and vacuum dry it at 20 °C.

[0050] S3. Immerse the red mud and slag treated in step S2 into 1.83 kg of hydrogen peroxide with a mass fraction of 30%, react at 40 °C for 0.5 h, and vacuum dry the filtered product at 20 °C.

[0051] S4. Put the slag and red mud treated in step S3, the carbide slag and phosphogypsum treated in step S1, and 60 g of modified biochar into a blender and stir for 20 min to obtain a cementitious material.

[0052] The above preparation method of modified biochar comprises the following steps:

[0053] S101. Disperse 432 g of cellulose into 6.48 kg of sodium hydroxide solution with a concentration of 0.5 mo / L, soak for 0.2 h, centrifuge and separate. After the product is washed with sufficient deionized water, freeze-dry it at -30 °C for 12 h.

[0054] S102. Disperse 408 g of cellulose treated in step S101 into a mixed solution of 12.24 kg of ammonium dihydrogen phosphate and sodium bicarbonate, soak for 1 h, where the concentration of ammonium dihydrogen phosphate is 0.1 mol / L and the concentration of sodium bicarbonate is 0.5 mol / L. Centrifuge and filter, and vacuum dry at 20 °C.

[0055] S103. Pyrolyze the cellulose treated in step S102 under a nitrogen atmosphere, with a pyrolysis temperature of 800 °C and a pyrolysis time of 3 h. After pyrolysis is completed and ground, sieve it through an 800-mesh sieve to obtain biochar.

[0056] S104. Immerse the 96 g of biochar obtained in step S103 in 1.15 kg of hydrochloric acid with a concentration of 5 mol / L for 6 h. After washing with sufficient deionized water, vacuum dry at 30 °C.

[0057] S105. Put the 72 g of biochar treated in step S104 into a mixed solution of 216 g of epichlorohydrin and 144 g of DMF. Heat up to 70 °C and react for 0.5 h, then dropwise add 72 g of diethylenetriamine and continue to react for 1 h. Filter the product, wash it with sufficient deionized water, and vacuum dry at 30 °C to obtain modified biochar.

[0058] Example 3

[0059] A preparation method of a cementitious material based on solid waste, comprising the following steps:

[0060] S1. Calcinate 210 g of red mud and 276 g of slag at 1000 °C for 4 h, and dry 180 g of carbide slag and 150 g of phosphogypsum at 150 °C.

[0061] S2. Put the red mud and slag treated in step S1 into a mixed solution of 3-mercaptopropyltrimethoxysilane and isopropanol and stir for 10 h. The dosages of 3-mercaptopropyltrimethoxysilane and isopropanol are 1.46 kg and 4.86 kg respectively. Filter the product, wash it with sufficient absolute ethanol, and vacuum dry at 40 °C.

[0062] S3. Immerse the red mud and slag treated in step S2 in 3.88 kg of hydrogen peroxide with a mass fraction of 30%, react at 70 °C for 2 h, and vacuum dry the filtered product at 40 °C.

[0063] S4. Put the slag and red mud treated in step S3, the carbide slag and phosphogypsum treated in step S1, and 108 g of modified biochar into a blender and stir for 20 min to obtain a cementitious material.

[0064] The preparation method of the above-mentioned modified biochar includes the following steps:

[0065] S101. Disperse 528 g of cellulose into 13.2 kg of sodium hydroxide solution with a concentration of 2 mo / L and soak for 1 h. Centrifuge and separate, and after washing the product with sufficient deionized water, freeze-dry at -70 °C for 24 h.

[0066] S102. Disperse the 474 g of cellulose treated in step S101 into a mixed solution of 23.7 kg of ammonium dihydrogen phosphate and sodium bicarbonate and soak for 2 h. The concentration of ammonium dihydrogen phosphate is 2 mol / L, and the concentration of sodium bicarbonate is 1 mol / L. Centrifuge and filter, and vacuum dry at 30 °C.

[0067] S103. Pyrolyze the cellulose processed in step S102 under a nitrogen atmosphere at a pyrolysis temperature of 1000 °C for 6 h. After pyrolysis, grind the product through a 500-mesh sieve to obtain biochar.

[0068] S104. Immerse 144 g of the biochar obtained in step S103 in 2.88 kg of hydrochloric acid with a concentration of 8 mol / L and treat for 10 h. After washing with sufficient deionized water, dry it under vacuum at 50 °C.

[0069] S105. Put 144 g of the biochar processed in step S104 into a mixed solution of 720 g of epichlorohydrin and 1 kg of DMF. Heat up to 90 °C and react for 1 h, then dropwise add 288 g of diethylenetriamine and continue to react for 2 h. Filter the product, wash it with sufficient deionized water, and dry it under vacuum at 50 °C to obtain modified biochar.

[0070] Example 4

[0071] A preparation method of a cementitious material based on solid waste, comprising the following steps:

[0072] S1. Calcinate 186 g of red mud and 246 g of slag at 900 °C for 2.5 h, and dry 72 g of carbide slag and 108 g of phosphogypsum at 120 °C.

[0073] S2. Put the red mud and slag processed in step S1 into a mixed solution of 3-mercaptopropyltrimethoxysilane and isopropanol and stir for 8 h. The dosages of 3-mercaptopropyltrimethoxysilane and isopropanol are 840 g and 4.14 kg respectively. Filter the product, wash it with sufficient absolute ethanol, and dry it under vacuum at 30 °C.

[0074] S3. Immerse the red mud and slag processed in step S2 into 2.58 kg of hydrogen peroxide with a mass fraction of 30%, react at 55 °C for 1 h, and filter the product and dry it under vacuum at 25 °C.

[0075] S4. Put the slag and red mud processed in step S3, the carbide slag and phosphogypsum processed in step S1, and 90 g of modified biochar into a blender and stir for 20 min to obtain a cementitious material.

[0076] The above preparation method of modified biochar comprises the following steps:

[0077] S101. Disperse 456 g of cellulose into 9 kg of sodium hydroxide solution with a concentration of 1.2 mo / L, soak for 1.4 h, and perform centrifugal separation. After washing the product with sufficient deionized water, freeze-dry it at -50 °C for 20 h.

[0078] S102. Disperse 384 g of cellulose treated in step S101 into a mixed solution of 16.8 kg of ammonium dihydrogen phosphate and sodium bicarbonate, soak for 1.6 h, where the concentration of ammonium dihydrogen phosphate is 1.2 mol / L and the concentration of sodium bicarbonate is 0.8 mol / L, and perform centrifugal filtration and vacuum drying at 30°C;

[0079] S103. Pyrolyze the cellulose treated in step S102 under a nitrogen atmosphere, with a pyrolysis temperature of 1000°C and a pyrolysis time of 4.5 h. After pyrolysis is completed, grind it through a 600-mesh sieve to obtain biochar;

[0080] S104. Immerse 126 g of the biochar obtained in step S103 in 1.83 kg of hydrochloric acid with a concentration of 6 mol / L and treat for 8 h. After washing with sufficient deionized water, perform vacuum drying at 45°C;

[0081] S105. Put 108 g of the biochar treated in step S104 into a mixed solution of 432 g of epichlorohydrin and 636 g of DMF, heat up to 80°C and react for 1 h, then dropwise add 132 g of diethylenetriamine and continue to react for 2 h. Filter the product, wash it with sufficient deionized water, and perform vacuum drying at 40°C to obtain modified biochar.

[0082] Comparative Example 1

[0083] The difference between Comparative Example 1 and Example 1 is that step S102 is omitted, thereby canceling the soaking process of cellulose in the mixed solution of ammonium dihydrogen phosphate and sodium bicarbonate, and the remaining steps are exactly the same as those in Example 1.

[0084] Comparative Example 2

[0085] The difference between Comparative Example 2 and Example 1 is that step S105 is omitted, thereby canceling the dropwise addition of diethylenetriamine, and the remaining steps are exactly the same as those in Example 1.

[0086] Comparative Example 3

[0087] The difference between Comparative Example 3 and Example 1 is that step S2 is omitted, thereby canceling the treatment process of red mud and slag in the mixed solution of 3-mercaptopropyltrimethoxysilane and isopropanol, and the remaining steps are exactly the same as those in Example 1.

[0088] The component tables of red mud, slag, phosphogypsum, and carbide slag used in Examples 1-4 and Comparative Examples 1-3 of the present invention are shown in Table 1 below:

[0089] Table 1: Composition table of red mud, slag, phosphogypsum, and carbide slag

[0090]

[0091]

[0092] 1. Fluidity Test

[0093] In Examples 1-4 and Comparative Examples 1-3, 450 g of cementitious materials were respectively taken, and water, cementitious materials and standard sand were mixed according to a mass ratio of 0.6:1:3. Specifically, 270 g of water was added to the mixing pan, and then 450 g of cementitious materials were added to the mixing pan. The machine was started, and after stirring at a low speed for 30 seconds, 1350 g of standard sand was evenly added, and then stirred at a high speed for 30 seconds, stopped stirring for 90 seconds, and finally stirred at a high speed for 60 seconds to obtain a mixture sample;

[0094] The mortar fluidity test was carried out by the method specified in GB2419 "Determination Method for Fluidity of Cement Mortar". The table top of the jumping table, test molds and related utensils were wiped with a wet towel; the freshly mixed mortar was quickly poured into the truncated cone mold in two portions, and at the same time leveled with a spatula and tamped with a tamper; then, the mold cover was removed, the jumping table was immediately opened, and vibrated at a frequency of 1 time per second for a total of 25 times; after the vibration ended, the diameter of the mortar spread was measured with a caliper, that is, the fluidity of the mortar. From the start of mixing the mortar to the end of the fluidity test, it should be within five minutes. The fluidity test results are shown in Table 2 below:

[0095] Table 2: Fluidity Test Table of Examples 1-4 and Comparative Examples 1-3

[0096] Flowability (mm) Example 1 245 Example 2 233 Example 3 228 Example 4 239 Comparative Example 1 225 Comparative Example 2 209 Comparative Example 3 214

[0097] It can be seen from the data in Table 1 above that the red mud and slag in the present invention can be effectively improved in fluidity and the mixing effect is improved by treatment with a mixed solution of 3-mercaptopropyltrimethoxysilane and isopropanol and the addition of modified biochar.

[0098] 2. Strength Test

[0099] After the fluidity test was completed, the mixture sample was quickly transferred to a steel test mold and vibrated twice with a vibrating table. After vibration, the test specimen was wrapped with plastic wrap for 24 h and then demolded, and then cured in a standard curing box at a temperature of 20 °C and a relative humidity of more than 90% for 3 d, 7 d and 28 d respectively;

[0100] The specific test method is as follows: The test is carried out by the method specified in GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)"; the instrument used is a fully automatic cement flexural and compressive testing machine (30t); the cured test specimens are placed on the support columns of the testing machine, and a vertical load of 50 N / s is applied until the specimen breaks, and the flexural strength (MPa) is recorded; then the two broken specimens are placed in the compressive fixture, and a vertical load of 2400 N / s is applied until it breaks, and the compressive strength (MPa) is recorded. The test results are shown in Table 3 as follows:

[0101] Table 3: Strength test result table of Examples 1-4 and Comparative Examples 1-3

[0102] 3d Flexural Strength 3d Compressive Strength 7d Flexural Strength 7d Compressive Strength 28d Flexural Strength 28d Compressive Strength Example 1 4.6 14.52 7.4 19.3 8.7 28.98 Example 2 3.7 14.06 6.8 18.89 8.9 28.84 Example 3 4.1 12.12 5.8 21.44 6.5 29.43 Example 4 4.2 13.87 7.1 18.53 8.2 27.39 Comparative Example 1 3.9 12.74 6.6 17.05 7.1 22.84 Comparative Example 2 3.5 11.74 5.6 16.05 6.6 19.84 Comparative Example 3 3.6 12.7 5.3 15.83 6.9 18.57

[0103] It can be seen from the data in Table 2 above that in the present invention, the red mud and slag are treated with a mixed solution of 3-mercaptopropyltrimethoxysilane and isopropanol and the addition of modified biochar effectively improves the flexural and compressive strengths of the mixture at 3d, 7d and 28d.

[0104] 3. Heavy metal leaching test

[0105] The heavy metal leaching concentrations of the red mud, slag, carbide slag and phosphogypsum used in this application are tested. The leaching concentrations of the red mud, slag, carbide slag and phosphogypsum are measured at pH 7, and the amounts of the red mud, slag, carbide slag and phosphogypsum are the same as those used in Example 1. The test standard is HJ 557-2010 "Horizontal Oscillation Method for Leaching Toxicity of Solid Waste". The test results are shown in Table 4 below;

[0106]

[0107] The concentrations of six heavy metals in the leachate of the mixture sample prepared in Example 1 were measured, and three different pH values, namely 3.2, 5 and 7, were set to simulate different leaching environments; the test was carried out by the method specified in GB / T30810-2014 "Test Method for Leachable Heavy Metals in Cement Mortar". The test results are shown in Table 5:

[0108] Table 5: Heavy metal leaching test result table of the mixture sample prepared in Example 1

[0109]

[0110] It can be seen from the data in Table 3 above that when the cementitious material prepared in the present invention is used for solidification, the heavy metal leaching test results can meet the three national standards listed in the table, and the harmful impact on the environment in practical applications is very small.

[0111] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A cementitious material based on solid waste, characterized in that: The components include the following by mass: 27-35 parts of red mud, 34-46 parts of slag, 5-30 parts of carbide slag, 10-25 parts of phosphogypsum, and 10-18 parts of modified biochar; The preparation method of the modified biochar comprises the following steps: S101, dispersing cellulose in a sodium hydroxide solution with a concentration of 0.5 to 2 mol / L and soaking for 0.2 to 1 hour, centrifuging and separating, washing the product with sufficient deionized water and freeze-drying it at -30 to -70°C for 12 to 24 hours; S102, dispersing the cellulose treated in step S101 into a mixed solution of ammonium dihydrogen phosphate and sodium bicarbonate and soaking for 1 to 2 hours, centrifugally filtering and vacuum drying at 20 to 30° C.; S103, pyrolyzing the cellulose treated in step S102 under a nitrogen atmosphere, and grinding the cellulose through a 500-800 mesh sieve to obtain biochar after pyrolysis; S104, immersing the biochar obtained in step S103 in hydrochloric acid with a concentration of 5 to 8 mol / L for 6 to 10 hours, washing with sufficient deionized water, and then vacuum drying at 30 to 50° C.; S105, placing the biochar treated in step S104 into a mixed solution of epichlorohydrin and DMF, heating to 70-90°C for reaction for 0.5-1h, then dropping diethylenetriamine to continue the reaction for 1-2h, filtering the product, washing with sufficient deionized water, and vacuum drying at 30-50°C to obtain modified biochar.

2. The solid waste-based cementitious material according to claim 1, characterized in that: The mass ratio of cellulose to sodium hydroxide solution in step S101 is 1:(15-25).

3. The solid waste-based cementitious material according to claim 1, characterized in that: In step S102, the concentration of ammonium dihydrogen phosphate is 0.1-2 mol / L, the concentration of sodium bicarbonate is 0.5-1 mol / L, and the mass ratio between the cellulose treated in step S101 and the mixed solution of ammonium dihydrogen phosphate and sodium bicarbonate is 1:(30-50).

4. The solid waste-based cementitious material according to claim 1, characterized in that: The pyrolysis temperature in step S103 is 800-1000° C., and the pyrolysis time is 3-6 hours.

5. The solid waste-based cementitious material according to claim 1, characterized in that: The mass ratio between the biochar and the hydrochloric acid in step S104 is 1:(12-20).

6. The solid waste-based cementitious material according to claim 1, characterized in that: The mass ratio of epichlorohydrin, DMF and diethylenetriamine in step S105 to the biochar treated in step S104 is (3-5):(2-7):(1-2):

1.

7. A method for preparing a cementitious material based on solid waste according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Calcine red mud and slag at 800-1000°C for 2-4h according to the proportion, and dry carbide slag and phosphogypsum at 100-150°C; S2, placing the red mud and slag treated in step S1 into a mixed solution of 3-mercaptopropyltrimethoxysilane and isopropanol and stirring for 2-10 hours, filtering the product, washing it with sufficient anhydrous ethanol, and vacuum drying it at 20-40° C.; S3, immersing the red mud and slag treated in step S2 into 30% by mass hydrogen peroxide, reacting at 40-70° C. for 0.5-2 h, filtering the product and vacuum drying it at 20-40° C.; S4. Put the slag and red mud treated in step S3, the carbide slag and phosphogypsum treated in step S1, and the modified biochar into a mixer and stir for 20 minutes to obtain a cementitious material.

8. The method for preparing a cementitious material based on solid waste according to claim 7, characterized in that: The mass ratio of the red mud and the slag to the mass ratio of 3-mercaptopropyltrimethoxysilane and isopropanol in step S2 is 1:(1-3):(8-10).

9. The method for preparing a cementitious material based on solid waste according to claim 7, characterized in that: The mass ratio of the red mud to the slag and to the hydrogen peroxide in step S3 is 1:(5-8).

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