Cement mixture as well as preparation method and application thereof

Abstract

The invention provides a cement mixture as well as a preparation method and application thereof, and the cement mixture comprises the following components in percentage by weight: 97.5-99.5% of Portland cement; 0.5%-2.5% of co-pyrolysis biochar; wherein the co-pyrolysis biochar is prepared by mixing the oily sludge and the agricultural waste according to the mass ratio of 1: (0.5-1.5) and performing pyrolysis at the temperature of 500-600 DEG C for 1.5-2.5 hours. According to the invention, the co-pyrolysis product of the oily sludge and the agricultural waste is used for replacing part of the cement, so that the use amount of the cement is reduced, the mechanical property of the cement is improved, the treatment problem of the oily sludge and the agricultural waste is solved, the resource utilization of the waste is realized, the cost is lower, and the cement is more environment-friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of cement materials, and in particular to a cement mixture and a preparation method and application thereof. Background Art

[0002] With the acceleration of global urbanization, large-scale infrastructure construction, high-rise buildings, large bridges, tunnels, and other engineering projects are constantly emerging. These large-scale structures place higher demands on concrete's strength, durability, and other properties. As a key material in concrete production, cement's performance directly determines its quality and performance. Therefore, with the development of the construction industry, the performance requirements for cement are also constantly increasing to meet the growing demand for construction.

[0003] Fibers are widely used to improve concrete performance. They can enhance concrete's crack resistance and toughness. However, during the concrete mixing process, fibers tend to aggregate, forming clumps. This not only affects concrete workability and creates stress concentration points within the concrete, affecting its mechanical properties, but can also make pumping difficult, increase construction complexity, and reduce construction efficiency. Polymer emulsion-modified concrete is also a common method in the prior art. Polymer emulsions can improve concrete's flexural strength, but this improvement often comes at the expense of the compressive strength of the cementitious materials. Additionally, some researchers have attempted to use biochar as an additive in concrete preparation. However, biochar has relatively low activity and poor compatibility with cementitious materials. This results in poor dispersion in concrete, hindering its full performance-enhancing properties. Other researchers have used oily sludge as a raw material for concrete preparation. Oily sludge is an industrial waste, and its use in concrete production can achieve a certain degree of resource recovery. However, oily sludge contains large amounts of organic matter and hazardous substances, which can adversely affect the durability of concrete. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a cement mixture and a preparation method and application thereof. The cement mixture has a simple formula and low preparation cost, and the cement products made from the cement mixture have better mechanical properties.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The present invention provides a cement mixture, which comprises, based on the total weight of the cement mixture being 100%, 97.5% to 99.5% of Portland cement and 0.5% to 2.5% of co-pyrolysis biochar. The co-pyrolysis biochar is prepared by mixing oily sludge and agricultural waste in a mass ratio of 1:(0.5 to 1.5), and pyrolyzing the mixture at a temperature of 500 to 600°C for 1.5 to 2.5 hours.

[0007] Unless otherwise specified, oily sludge refers to waste materials containing large amounts of oil generated during oil extraction, refining, storage, transportation, and oily wastewater treatment. It primarily consists of oil, water, suspended solids, and heavy metal salts. Oil includes hydrocarbon compounds such as crude oil and diesel, as well as benzene series and polycyclic aromatic hydrocarbons, accounting for 10% to 50% by mass; water, in the form of free or emulsified water, accounts for 30% to 80% by mass; and solid particles include inorganic and organic matter. Inorganic materials include clay, sand, metal oxides, and heavy metals, while organic materials include colloidal asphaltene and microbial residues, accounting for 10% to 60% by mass.

[0008] When oily sludge is pyrolyzed alone, the concentration of oxygen compounds exceeds the standard and the stability is also unsatisfactory. The present invention pyrolyzes oily sludge and agricultural waste together. During the pyrolysis process, agricultural waste mainly composed of lignocellulosic biomass will generate a large number of active free radicals, and its H / C ratio is much higher than that of other substances. This enables the biomass to act as an ideal hydrogen donor when co-pyrolyzed with oily sludge, thereby increasing the yield of stable pyrolysis oil and optimizing the quality of pyrolysis coke. At the same time, the co-pyrolysis of the two has a synergistic effect, and the carbon content, specific surface area and adsorption properties of the co-pyrolysis products can be improved. Replacing part of the cement raw materials with the co-pyrolysis products can better fill the gaps in the cement mortar, making the internal space of the gel material more compact and solid, thereby achieving uniform particle size distribution, changing the spatial structure, and playing a good promoting role in the cement hydration process, thereby improving the mechanical properties of the material system.

[0009] In some embodiments, based on the total weight of the cement mixture being 100%, the cement mixture comprises:

[0010] Portland cement 98% to 99.2%;

[0011] Co-pyrolysis biochar 0.8% to 2%.

[0012] Further preferably, based on the total weight of the cement mixture being 100%, the cement mixture comprises:

[0013] Portland cement 98.5% to 99%;

[0014] Co-pyrolysis biochar 1% to 1.5%.

[0015] In some embodiments, the co-pyrolysis biochar is a mixture of oily sludge and agricultural waste in a mass ratio of 1: (0.8-1.2).

[0016] Further preferably, the co-pyrolysis biochar is a mixture of oily sludge and agricultural waste in a mass ratio of 1: (0.9-1.1).

[0017] In some embodiments, the agricultural waste is selected from one or more of corn cobs, rice husks, and wheat husks.

[0018] In some embodiments, the silicate cement is PO type 42.5 silicate cement.

[0019] In some embodiments, the oily sludge is oily sludge with a moisture content of no more than 1%, and the agricultural waste is agricultural waste with a moisture content of no more than 1%.

[0020] A second aspect of the present invention is to provide a method for preparing the cement mixture as described above, the method comprising the following steps:

[0021] (1) Drying oily sludge and agricultural waste separately to a moisture content of less than or equal to 1%, and then mixing and pyrolyzing them to produce co-pyrolysis biochar;

[0022] (2) Mixing the co-pyrolyzed biochar with silicate cement to prepare the cement mixture.

[0023] In some embodiments, the drying temperature is 60-80°C, more preferably 65-75°C.

[0024] The third aspect of the present invention is to provide an application of the cement mixture as described above, comprising using the cement mixture to prepare cement parts.

[0025] A fourth aspect of the present invention is to provide a cement product, which is formed by mixing a cement mixture, water, and standard sand, stirring, shaping, and curing the mixture, wherein the cement mixture is the cement mixture described above. The stirring, shaping, and curing steps may be referred to the prior art.

[0026] In some embodiments, the mass ratio of the cement mixture, the water, and the standard sand is 1:(0.3-0.8):(2-4), preferably 1:(0.4-0.7):(2.5-3.5), and more preferably 1:(0.4-0.6):(2.8-3.2).

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention replaces part of the cement with the co-pyrolysis products of oily sludge and agricultural waste, thereby improving the mechanical properties of cement, reducing the amount of cement used, solving the disposal problem of oily sludge and agricultural waste, and realizing waste resource utilization, with lower cost and greater environmental protection. DETAILED DESCRIPTION

[0029] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0030] The oily sludge involved in the following text comes from an oil company; silicate P.O42.5 silicate P.O42.5 cement is purchased from Zhucheng Jiuqi Building Materials Company.

[0031] Example 1

[0032] Oily sludge and corncobs were oven-dried at 70°C to reduce their moisture content to below 1% (mass percentage), collected, and thoroughly mixed in a 1:1 mass ratio. The mixture was then placed in a crucible and pyrolyzed in a muffle furnace at 500°C for 2 hours. After cooling to room temperature, the mixture was removed from the muffle furnace to produce co-pyrolysis biochar.

[0033] The co-pyrolyzed biochar is mixed with silicate P.O.42.5 cement to produce a cement mixture, wherein, based on the total weight of the cement mixture being 100%, the co-pyrolyzed biochar accounts for 1% by weight and the silicate P.O.42.5 cement accounts for 99% by weight.

[0034] Mix water and cement mixture in a mass ratio of 0.5:1. After stirring at low speed (140±5r / min) for 60 seconds, add standard sand evenly within 5 seconds (the mass of standard sand is 3 times the total mass of the cement mixture), stir at high speed (285±10r / min) for 30 seconds, stop stirring for 90 seconds, and stir at high speed for 60 seconds to obtain slurry. Pour the slurry into the mold and form it. Vibrate it on a vibrating table to reduce the internal bubbles. Then cure the mold at 20±1℃ and 96% relative humidity for 24 hours. After demolding, obtain the rough blank. Cure the rough blank in water, and then cure the crude product to the specified age before mechanical property testing. For details, please refer to "Test Method for Strength of Cement Mortar (ISO Method) GBT17671-2021".

[0035] The cement composite gel material produced by this method exhibited mechanical properties of 9.7 MPa (flexural strength) and 28 MPa (compressive strength) after 3 days. The mechanical properties after 28 days were 15.8 MPa (flexural strength) and 52.2 MPa (compressive strength). Mechanical property testing methods were based on the "Test Method for Cement Mortar Strength (ISO Method) GBT 17671-2021."

[0036] Example 2

[0037] This embodiment is basically the same as embodiment 1, except that rice husks are used instead of corn cobs to prepare co-pyrolysis biochar.

[0038] The cement composite gel material prepared in this example has the following mechanical properties: flexural strength 9.9 MPa and compressive strength 29.5 MPa after 3 days; and flexural strength 13 MPa and compressive strength 49.7 MPa after 28 days.

[0039] Example 3

[0040] This embodiment is basically the same as embodiment 1, except that wheat hulls are used instead of corn cobs to prepare co-pyrolysis biochar.

[0041] The cement composite gel material prepared in this example has the following mechanical properties: flexural strength of 9.2 MPa and compressive strength of 26.1 MPa after 3 days; and flexural strength of 14.0 MPa and compressive strength of 45.1 MPa after 28 days.

[0042] Example 4

[0043] This embodiment is basically the same as embodiment 1, except that the pyrolysis parameter is set to 600°C.

[0044] The cement composite gel material prepared in this example has the following mechanical properties: flexural strength of 9.5 MPa and compressive strength of 26.4 MPa after 3 days; and flexural strength of 14.4 MPa and compressive strength of 48.8 MPa after 28 days.

[0045] Example 5

[0046] This embodiment is basically the same as embodiment 1, except that rice husks are used instead of corn cobs, and the pyrolysis parameters are set to 600°C.

[0047] The cement composite gel material prepared in this example has the following mechanical properties after 3 days: flexural strength 9.8 MPa, compressive strength 26.9 MPa; and 28 days: flexural strength 14.3 MPa, compressive strength 46.5 MPa.

[0048] Example 6

[0049] This embodiment is basically the same as embodiment 1, except that wheat hulls are used instead of corn cobs, and the pyrolysis parameters are set to 600°C.

[0050] The cement composite gel material prepared in this example has the following mechanical properties: flexural strength 9.9 MPa and compressive strength 29.2 MPa after 3 days; and flexural strength 13.5 MPa and compressive strength 48.8 MPa after 28 days.

[0051] Comparative Example 1

[0052] This comparative example is basically the same as Example 1, except that no co-pyrolyzed biochar is added to the cement mixture, and only silicate P.O42.5 cement is used.

[0053] The mechanical properties of the cement gel material prepared in this comparative example after 3 days are as follows: flexural strength 6.6 MPa, compressive strength 26.6 MPa; and mechanical properties after 28 days are as follows: compressive strength 13 MPa, flexural strength 45.6 MPa.

[0054] Comparative Example 2

[0055] This embodiment is basically the same as embodiment 1, except that the co-pyrolysis biochar accounts for 3% of the total mass of the cement mixture.

[0056] The cement composite gel material prepared in this example has the following mechanical properties: flexural strength of 9.7 MPa and compressive strength of 29.2 MPa after 3 days; and flexural strength of 14.4 MPa and compressive strength of 48.9 MPa after 28 days.

[0057] Comparative Example 3

[0058] This comparative example is basically the same as Example 1, except that the co-pyrolysis biochar accounts for 5% of the total mass of the cement mixture.

[0059] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 8.8 MPa, compressive strength 24.3 MPa; and 28 days: flexural strength 12.8 MPa, compressive strength 44.6 MPa.

[0060] Comparative Example 4

[0061] This embodiment is basically the same as embodiment 1, except that wheat hulls are used instead of corn cobs to prepare the co-pyrolysis biochar, and the co-pyrolysis biochar accounts for 3% of the total mass of the cement mixture.

[0062] The cement composite gel material prepared in this example has the following mechanical properties: flexural strength of 8.4 MPa and compressive strength of 21.7 MPa after 3 days; and flexural strength of 13.6 MPa and compressive strength of 48.5 MPa after 28 days.

[0063] Comparative Example 5

[0064] This comparative example is basically the same as Example 1, except that wheat hulls are used instead of corn cobs to prepare the co-pyrolysis biochar, and the co-pyrolysis biochar accounts for 5% of the total mass of the cement mixture.

[0065] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 8.8 MPa, compressive strength 24.2 MPa; and 28 days: flexural strength 12.8 MPa, compressive strength 44.6 MPa.

[0066] Comparative Example 6

[0067] This comparative example is basically the same as Example 1, except that rice husks are used instead of corn cobs, and the co-pyrolysis biochar accounts for 3% of the total mass of the cement mixture.

[0068] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 9.7 MPa, compressive strength 26.1 MPa; and 28 days: flexural strength 12.8 MPa, compressive strength 46.5 MPa.

[0069] Comparative Example 7

[0070] This comparative example is basically the same as Example 1, except that rice husks are used instead of corn cobs, and the co-pyrolysis biochar accounts for 5% of the total mass of the cement mixture.

[0071] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 8.5 MPa, compressive strength 24.7 MPa; and 28 days: flexural strength 11.2 MPa, compressive strength 44.3 MPa.

[0072] Comparative Example 8

[0073] This comparative example is basically the same as Example 1, except that the pyrolysis parameter is set to 600° C., and the co-pyrolysis biochar accounts for 3% of the total mass of the cement mixture.

[0074] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 9.0 MPa, compressive strength 25.8 MPa; and 28 days: flexural strength 12.5 MPa, compressive strength 44.9 MPa.

[0075] Comparative Example 9

[0076] This comparative example is substantially the same as Example 1, except that the pyrolysis parameters are set at 600° C., and the co-pyrolysis biochar accounts for 5% of the total mass of the cement mixture.

[0077] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 8.5 MPa, compressive strength 23.5 MPa; and 28 days: flexural strength 11.9 MPa, compressive strength 40.1 MPa.

[0078] Comparative Example 10

[0079] This comparative example is basically the same as Example 1, except that rice husks are used instead of corn cobs, the pyrolysis parameters are set to 600° C., and the co-pyrolysis biochar accounts for 3% of the total mass of the cement mixture.

[0080] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 9.2 MPa, compressive strength 25.6 MPa; and 28 days: flexural strength 13.7 MPa, compressive strength 44.8 MPa.

[0081] Comparative Example 11

[0082] This comparative example is basically the same as Example 1, except that rice husks are used instead of corn cobs, the pyrolysis parameters are set to 600° C., and the co-pyrolysis biochar accounts for 5% of the total mass of the cement mixture.

[0083] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 8.3 MPa, compressive strength 24.5 MPa; and 28 days: flexural strength 13.1 MPa, compressive strength 40.4 MPa.

[0084] Comparative Example 12

[0085] This comparative example is substantially the same as Example 1, except that wheat hulls are used instead of corn cobs, the pyrolysis parameters are set to 600° C., and the co-pyrolysis biochar accounts for 3% of the total mass of the cement mixture.

[0086] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 9.2 MPa, compressive strength 25.5 MPa; and 28 days: flexural strength 12.5 MPa, compressive strength 43.6 MPa.

[0087] Comparative Example 13

[0088] This comparative example is basically the same as Example 1, except that wheat hulls are used instead of corn cobs, the pyrolysis parameters are set to 600° C., and the co-pyrolysis biochar accounts for 5% of the total mass of the cement mixture.

[0089] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 8.3 MPa, compressive strength 23.5 MPa; and 28 days: flexural strength 11.6 MPa, compressive strength 42.1 MPa.

[0090] Comparative Example 14

[0091] This comparative example is basically the same as Example 1, except that the oily sludge and corn cobs are dried and mixed in a ratio of 1:2.

[0092] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 8.3 MPa, compressive strength 22.5 MPa; and 28 days: flexural strength 11.1 MPa, compressive strength 40.8 MPa.

[0093] Comparative Example 15

[0094] This comparative example is basically the same as Example 1, except that the oily sludge and corn cobs are dried and mixed in a ratio of 1:2, and the co-pyrolysis biochar accounts for 3% of the total mass of the cement mixture.

[0095] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength of 8.6 MPa, compressive strength of 21.5 MPa; and 28 days: flexural strength of 15.3 MPa, compressive strength of 39.4 MPa.

[0096] Comparative Example 16

[0097] This comparative example is basically the same as Example 1, except that the oily sludge and corn cobs are dried and mixed in a ratio of 1:2, and the co-pyrolysis biochar accounts for 5% of the total mass of the cement mixture.

[0098] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 9.2 MPa, compressive strength 24.5 MPa; and 28 days: flexural strength 12.8 MPa, compressive strength 42.5 MPa.

[0099] Comparative Example 17

[0100] This comparative example is basically the same as Example 1, except that wheat hulls are used instead of corn cobs, and the oily sludge and wheat hulls are dried and mixed in a ratio of 1:2.

[0101] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 9.2 MPa, compressive strength 24.6 MPa; and 28 days: flexural strength 11.8 MPa, compressive strength 44.9 MPa.

[0102] Comparative Example 18

[0103] This comparative example is basically the same as Example 1, except that wheat husks are used instead of corn cobs, the oily sludge and wheat husks are dried and mixed in a ratio of 1:2, and the co-pyrolysis biochar accounts for 3% of the total mass of the cement mixture.

[0104] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 9.0 MPa, compressive strength 24.0 MPa; and 28 days: flexural strength 12.7 MPa, compressive strength 43.0 MPa.

[0105] Comparative Example 19

[0106] This comparative example is basically the same as Example 1, except that wheat husks are used instead of corn cobs, the oily sludge and wheat husks are dried and mixed in a ratio of 1:2, and the co-pyrolysis biochar accounts for 5% of the total mass of the cement mixture.

[0107] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 8.5 MPa, compressive strength 23.0 MPa; and 28 days: flexural strength 11.3 MPa, compressive strength 41.6 MPa.

[0108] Comparative Example 20

[0109] This comparative example is basically the same as Example 1, except that rice husks are used instead of corn cobs, and the oily sludge and rice husks are dried and mixed in a ratio of 1:2.

[0110] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 9.3 MPa, compressive strength 24.9 MPa; and 28 days: flexural strength 14.8 MPa, compressive strength 44.1 MPa.

[0111] Comparative Example 21

[0112] This comparative example is basically the same as Example 1, except that rice husks are used instead of corn cobs, the oily sludge and rice husks are dried and mixed in a ratio of 1:2, and the co-pyrolysis biochar accounts for 3% of the total mass of the cement mixture.

[0113] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 9.0 MPa, compressive strength 24.1 MPa; and 28 days: flexural strength 13.5 MPa, compressive strength 42.9 MPa.

[0114] Comparative Example 22

[0115] This comparative example is basically the same as Example 1, except that rice husks are used instead of corn cobs, the oily sludge and rice husks are dried and mixed in a ratio of 1:2, and the co-pyrolysis biochar accounts for 5% of the total mass of the cement mixture.

[0116] The cement composite gel material prepared in this comparative example has the following mechanical properties after 3 days: flexural strength 8.8 MPa, compressive strength 23.9 MPa; and 28 days: flexural strength 13.3 MPa, compressive strength 42.3 MPa.

[0117] Comparative Example 23

[0118] This example is essentially the same as Example 1, except that only the oily sludge is dried and pyrolyzed, and the pyrolysis product is then mixed with silicate P.O. 42.5 cement to produce a cement mix. The drying and pyrolysis conditions are similar to those in Example 1.

[0119] The mechanical properties of the cement composite gel material prepared in this comparative example after 3 days are as follows: flexural strength 7.9 MPa, compressive strength 25.0 MPa; and mechanical properties after 28 days are as follows: flexural strength 9.0 MPa, compressive strength 45.6 MPa.

[0120] Comparative Example 24

[0121] This example is essentially the same as Example 1, except that only the corn cobs are dried and pyrolyzed, and the pyrolysis products are then mixed with silicate P.O. 42.5 cement to produce a cement mix. The drying and pyrolysis conditions are similar to those in Example 1.

[0122] The mechanical properties of the cement composite gel material prepared in this comparative example after 3 days are as follows: flexural strength 7.4 MPa, compressive strength 22.5 MPa; and mechanical properties after 28 days are as follows: flexural strength 8.6 MPa, compressive strength 41.6 MPa.

[0123] Using only the pyrolysis products of oily sludge or agricultural waste to partially replace cement in preparing a cement mix does not significantly improve the performance of the cement mix. Surprisingly, the present invention improves the performance of the cement mix, particularly the mechanical properties of the cement composite gel material prepared from the cement mix, by replacing part of the cement with co-pyrolysis biochar produced by mixing and co-pyrolyzing oily sludge and agricultural waste. However, when the mass ratio of oily sludge to agricultural waste, the pyrolysis temperature, and the amount of co-pyrolysis biochar added are not appropriate, the performance of the cement mix is ​​not significantly improved, and may even be reduced. See Comparative Examples 2 to 22 for details.

[0124] The above detailed description of the present invention is intended to enable persons familiar with the art to understand the contents of the present invention and implement them. It does not limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A cement mixture, characterized in that: Taking the total weight of the cement mixture as 100%, the cement mixture comprises: Portland cement 97.5% to 99.5%; Co-pyrolysis biochar 0.5% to 2.5%; The co-pyrolysis biochar is prepared by mixing oily sludge and agricultural waste in a mass ratio of 1: (0.5-1.5) and pyrolyzing them at a temperature of 500-600° C. for 1.5-2.5 hours.

2. The cement mixture according to claim 1, characterized in that Taking the total weight of the cement mixture as 100%, the cement mixture comprises: Portland cement 98% to 99.2%; Co-pyrolysis biochar 0.8% to 2%.

3. The cement mixture according to claim 2, characterized in that Taking the total weight of the cement mixture as 100%, the cement mixture comprises: Portland cement 98.5% to 99%; Co-pyrolysis biochar 1% to 1.5%.

4. The cement mixture according to claim 1, characterized in that The oily sludge and agricultural waste in the co-pyrolysis biochar are mixed in a mass ratio of 1: (0.8-1.2).

5. The cement mixture according to claim 1, characterized in that: The agricultural waste is selected from one or more of corn cobs, rice husks, and wheat husks; And / or, the Portland cement is PO type 42.5 Portland cement; And / or, the oily sludge is oily sludge with a moisture content of no more than 1%, and the agricultural waste is agricultural waste with a moisture content of no more than 1%.

6. The method for preparing a cement mixture according to any one of claims 1 to 5, wherein: The preparation method comprises the following steps: (1) Drying oily sludge and agricultural waste separately to a moisture content of less than or equal to 1%, and then mixing and pyrolyzing them to produce co-pyrolysis biochar; (2) Mixing the co-pyrolyzed biochar with silicate cement to prepare the cement mixture.

7. The method for preparing a cement mixture according to claim 6, wherein: The drying temperature is 60-80°C.

8. Use of the cement mixture according to any one of claims 1 to 5, characterized in that: The application is to use the cement mixture for preparing cement products.

9. A cement product, characterized in that: The cement mixture is formed by mixing cement admixture, water and standard sand, stirring, molding and curing. The cement admixture is the cement admixture according to any one of claims 1 to 5.

10. The cement article according to claim 9, characterized in that: The mass ratio of the cement mixture, the water and the standard sand is 1:(0.3-0.8):(2-4).