Curing agent for engineering spoil as well as preparation method and use method of curing agent

Abstract

The invention relates to the technical field of building materials, in particular to a curing agent for engineering spoil as well as a preparation method and a use method of the curing agent. The curing agent for the engineering spoil comprises the following components in parts by weight: 20-60 parts of steel slag and 40-80 parts of mineral slag, the sum of the parts by weight of the steel slag and the mineral slag is 100. By implementing the method, high-efficiency and low-cost solidification of the engineering spoil can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a solidifying agent for engineering spoil and a preparation method and use method thereof. BACKGROUND

[0002] Engineering spoil refers to spoil produced in various construction projects, specifically spoil, slurry, spoil stone and the like produced in the construction process of building projects, bridge projects, rail transit projects, comprehensive pipe gallery projects and the like. Engineering spoil includes substances such as clay, crushed stone, silt, sandy soil, pebbles and gravel. At present, the treatment methods of engineering spoil mainly include landfill, hill making and road shelter forest belt, but there is a problem of low efficiency in treatment at present, and therefore resource utilization becomes an important research direction.

[0003] According to the geotechnical properties of engineering spoil, it can be divided into good quality soil and poor quality soil. Good quality soil is mainly soil that has good compaction performance and is easy to construct, and it can be directly applied to roadbeds and pipe gallery backfill. Poor quality soil generally includes shallow silt, shield spoil and waste slurry, and has a high water content (≥80 wt%) and a low unconfined compressive strength (≤50 kPa), and therefore cannot be directly utilized and needs to be treated before application. The commonly used treatment methods at present include physical drying method, chemical solidification method and sintering method. The physical drying method refers to drying and dewatering engineering spoil by physical methods, and then using it as a filling material, but its strength is weak. The chemical solidification method refers to adding cement and other solidifying materials to engineering spoil to use it as a filling material, but the cost of cement is high. The sintering method refers to using engineering spoil as an admixture to prepare bricks, tiles and ceramsite, but due to the large difference in the chemical composition of spoil, the performance of finished products such as bricks, tiles and ceramsite is greatly different, and the yield is low. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a solidifying agent for engineering spoil and a preparation method and application method thereof, which can realize efficient and low-cost solidification of poor quality soil.

[0005] In order to solve the above problems, the present application provides a solidifying agent for engineering spoil, which comprises the following components by weight:

[0006] 20-60 parts of steel slag and 40-80 parts of slag; the sum of the weight parts of the steel slag and the slag is 100 parts.

[0007] As an improvement of the above technical solution, the content of RO phase in the steel slag is ≥15 wt%, the content of glass phase is ≤10 wt%, and the total content of tricalcium silicate phase and dicalcium silicate phase is ≥60 wt%.

[0008] As the improvement of the above technical scheme, the content of the RO phase in the steel slag is 18wt%-25wt%, the content of the glass phase is 5wt%-10wt%, and the total content of the tricalcium silicate phase and the dicalcium silicate phase is 60wt%-65wt%.

[0009] And the ratio of the content of the dicalcium silicate phase to the content of the tricalcium silicate phase is greater than or equal to 15.

[0010] As the improvement of the above technical scheme, the ratio of the content of the dicalcium silicate phase to the content of the tricalcium silicate phase in the steel slag is 18-25.

[0011] As the improvement of the above technical scheme, the content of the glass phase in the slag is greater than or equal to 85wt%, and the content of the dicalcium silicate phase is greater than or equal to 3wt%.

[0012] As the improvement of the above technical scheme, the content of the glass phase in the slag is 85wt%-92wt%, and the content of the dicalcium silicate phase is 3wt%-6wt%.

[0013] Correspondingly, the application also discloses a preparation method of the solidifying agent for engineering spoil.

[0014] Correspondingly, the application also discloses a use method of the solidifying agent.

[0015] The engineering spoil and the solidifying agent are uniformly mixed to obtain a mixture, and the content of the solidifying agent in the mixture is greater than or equal to 15wt%.

[0016] The mixture is subjected to carbonization reaction in a carbon dioxide atmosphere to obtain solidified soil.

[0017] As the improvement of the above technical scheme, in the step of subjecting the mixture to carbonization reaction in a carbon dioxide atmosphere to obtain solidified soil, the carbonization reaction is performed for 10h-15h, at a temperature of 15℃-35℃, and at a relative humidity of 50%-70%.

[0018] As the improvement of the above technical scheme, the water content of the engineering spoil is less than or equal to 40wt%.

[0019] The content of the solidifying agent in the mixture is 15wt%-25wt%.

[0020] The application has the following beneficial effects:

[0021] The solidifying agent for engineering spoil in the embodiment of the application comprises 20-60 parts of steel slag and 40-80 parts of slag, and Ca 2+ The solidifying agent can react with Na + , K+ The ion exchange reaction occurs, the double electron layer is thinned, the aggregation strength of the soil particles is increased, and compaction is facilitated. The CaO and SiO2 in the steel slag and the slag can react with CO2 and water in the construction waste soil to generate calcium carbonate, which not only can reduce the water content of the construction waste soil, but also can effectively fill the large pores in the construction waste soil after volume expansion, thereby reducing the porosity and facilitating compaction. After the construction waste soil is carbonized and solidified by the solidifying agent in the embodiment, the high liquid limit construction waste soil can be converted into low liquid limit silty solidified soil, which can be used for backfilling of roadbeds, pipe corridors and the like, thereby improving the resource utilization efficiency. Meanwhile, the method in the application also realizes fixation of carbon dioxide, which is green and environmentally friendly. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of the present application, the present application will be described in more detail below. However, it should be understood that the present application can be realized in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the disclosure of the present application more thorough and comprehensive.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein is for the purpose of describing particular embodiments or examples only and is not intended to be limiting of the present application. As used herein, the term "and / or" is intended to include any and all combinations of one or more of the associated listed items.

[0024] The following examples are given for the purpose of illustrating various embodiments of the present application and are not intended to limit the present application in any way. Those skilled in the art will appreciate that variations and modifications of the embodiments described herein can be made which fall within the spirit and scope of the application as defined by the appended claims. Materials, reagents and the like used in the following examples are of a quality and type that is commonly available to those in the art.

[0025] In the present application, the technical features described in an open manner include both a closed technical solution consisting of the listed features and an open technical solution containing the listed features.

[0026] In the present application, the percentage content involved, unless otherwise specified, refers to mass percentage for solid-liquid mixing and solid-solid mixing, and refers to volume percentage for liquid-liquid mixing.

[0027] The percentage concentration involved in the present application refers to the final concentration, unless otherwise specified. The final concentration refers to the proportion of the added component in the system after the component is added.

[0028] The temperature parameter in the present application, unless otherwise specified, allows both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows fluctuations within the accuracy range controlled by the instrument.

[0029] As a first aspect of the present application, the present application provides a solidifying agent for engineering spoil, which comprises the following components by weight:

[0030] Steel slag 20-60 parts, slag 40-80 parts, the sum of the weight parts of steel slag and slag being 100 parts.

[0031] The steel slag is a waste residue generated during the steelmaking process, specifically a slag formed by the reaction of a slagging agent added during the smelting of molten steel with impurities in the molten steel, furnace lining, etc. The main chemical components of the steel slag include CaO, SiO2, Al2O3, FeO, Fe2O3, MgO, MnO2, etc. The main phase components of the steel slag include tricalcium silicate (3CaO·SiO2, C3S), dicalcium silicate (2CaO·SiO2, C2S), calcium ferrite (2CaO·Fe2O3), f-CaO, f-MgO, and RO phase (a multi-component compound mainly composed of FeO-MgO). The active components C3S and C2S in the steel slag can undergo hydration reactions, reducing the moisture content in the engineering spoil, and also forming calcium carbonate with the CO2 introduced, thereby filling the pores in the engineering spoil and improving its strength. In addition, the active f-CaO and f-MgO in the steel slag can also directly react with CO2, filling the pores in the engineering spoil and improving its strength. Furthermore, due to the high alkalinity of the steel slag, Ca(OH)2 is formed, which can also stimulate the slag to some extent, thereby improving the strength of the engineering spoil.

[0032] For example, the amount of steel slag used is 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, or 55 parts, but is not limited thereto. Preferably, the amount is 20-40 parts, and more preferably, the amount is 20-30 parts.

[0033] The slag is a byproduct of the blast furnace ironmaking process, which is a molten material generated by the reaction of impurities in iron ore with lime, etc., and is obtained by cooling. The chemical composition of the slag is mainly composed of CaO, SiO2, Al2O3, and MgO oxides. The main phase components of the slag include glass and a small amount of dicalcium silicate and calcium aluminum yellow long stone. The glass phase in the slag has pozzolanic activity and can react with the steel slag and CO2 to form calcium carbonate, thereby reducing the moisture content and improving the strength of the engineering spoil. Moreover, the large amount of glass phase in the slag has high hydration activity, and the Ca2+ Na + , K + ions exchange with Na

[0034] For example, the amount of slag is 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts or 75 parts, but not limited to this. Preferably, 60-80 parts, more preferably 70-80 parts.

[0035] Preferably, in some embodiments, the content of RO phase in steel slag is ≥15wt%, the content of glass phase is ≤10wt%, and the total content of tricalcium silicate phase and dicalcium silicate phase is ≥60wt%. The RO phase is an inert phase, which does not have pozzolanic reaction and hydration reaction, and has large hardness, and remains relatively complete during the steel slag grinding process, with a particle size of about 30-50 μm. Therefore, the RO phase can play the role of aggregate, help to maintain the pore structure of the mixture of the solidifying agent and the engineering waste soil, and further optimize the carbonation reaction and improve the strength. Therefore, the content of RO phase is controlled to be ≥15wt%. The glass phase has strong hydration activity, which can form calcium silicate gel at a faster speed. After CO2 reacts with the calcium silicate gel, the volume of the gel becomes small, which reduces the porosity, and further makes it difficult for CO2 to penetrate into the interior of the mixture of the solidifying agent and the engineering waste soil, thereby reducing the strength. Therefore, the content of the glass phase is controlled to be ≤10wt%. The tricalcium silicate phase and the dicalcium silicate phase are the main active phases, and the activation thereof can produce calcium hydroxide and hydrated calcium silicate to provide reactants for the carbonation reaction, thereby improving the strength. In order to ensure the strength, the total content of the tricalcium silicate phase and the dicalcium silicate phase is controlled to be ≥60wt%.

[0036] It should be noted that in the present application, the carbonation reaction is mainly carried out by CO2 to improve the strength. CO2 needs to penetrate into the interior of the mixture of the solidifying agent and the engineering waste soil to carry out the carbonation reaction. In the steel slag, if the glass phase content is high, the hydration activity is high, and a large amount of calcium silicate gel is easily generated in a short time. After CO2 reacts with the calcium silicate gel, the volume of the gel becomes small, which reduces the porosity, and further makes it difficult for CO2 to penetrate into the interior, thereby reducing the strength. Therefore, the content of the glass phase is controlled to be ≤10wt%, and the content of the RO phase is ≥15wt%, so as to optimize the pore structure. Further, the total content of the tricalcium silicate phase and the dicalcium silicate phase is controlled to be ≥60wt%, so as to provide more active phases while maintaining the pore structure, and ensure the strength.

[0037] More preferably, in some embodiments, the content of RO phase in the steel slag is 18wt%-25wt%, the content of glass phase is 5wt%-10wt%, and the total content of dicalcium silicate phase and tricalcium silicate phase is 60wt%-65wt%. When the content of RO phase is too large, the hydration activity is too low, and the strength is limited to be improved, so the content of RO phase is controlled to be 18wt%-25wt%. When the content of glass phase is too small, the alkaline phase is relatively small, and the activation of slag is poor, so the content of glass phase is controlled to be 5wt%-10wt%. The dicalcium silicate phase and the tricalcium silicate phase are main active phases, and by controlling the content of dicalcium silicate phase and tricalcium silicate phase to be 60wt%-65wt%, the strength can be improved.

[0038] Preferably, in some embodiments, the ratio of the content of dicalcium silicate phase to the content of tricalcium silicate phase is greater than or equal to 15; it should be noted that since the activity of tricalcium silicate phase is better than that of dicalcium silicate phase, it is easy to react to form more hydrated calcium silicate, ettringite and the like in the early stage, and it is easy to reduce the porosity faster. The dicalcium silicate phase has a slower hydration reaction rate, which can effectively avoid the rapid reduction of porosity. More preferably, the ratio of the content of dicalcium silicate phase to the content of tricalcium silicate phase in the steel slag is 18-25.

[0039] Preferably, in some embodiments, the content of glass phase in the slag is greater than or equal to 85wt%, and the content of dicalcium silicate phase is greater than or equal to 3wt%. The activity of such slag is stronger, which is beneficial to reduce the moisture in the engineering spoil and improve the strength. It should be noted that since the glass phase matrix structure in the slag is mainly SiO2-Al2O3, it is more stable than the glass body in the steel slag, and it is easy to form calcium-sodium-aluminum silicate on the surface, which reduces the generation speed of hydrated calcium silicate gel, so its role in hindering the diffusion of CO2 is smaller. Moreover, if the content of glass phase in the slag is too low, the activity is poor, and it is difficult to improve the strength, so the content of glass phase in the slag is controlled to be greater than or equal to 85wt%.

[0040] More preferably, in some embodiments, the content of glass phase in the slag is 85wt%-92wt%, and the content of dicalcium silicate is 3wt%-6wt%.

[0041] Correspondingly, as a second aspect of the present application, the present application also discloses a preparation method of engineering spoil, which comprises uniformly mixing steel slag and slag to obtain the engineering spoil.

[0042] Correspondingly, as a third aspect of the present application, the present application provides a use method of a solidifying agent, which comprises:

[0043] uniformly mixing the engineering spoil and the solidifying agent to obtain a mixture;

[0044] carrying out carbonization reaction on the mixture in a carbon dioxide atmosphere to obtain solidified soil.

[0045] Specifically, the engineering spoil can be good soil or poor soil, but is not limited thereto. In some embodiments, the engineering spoil is poor soil, and the solidifying agent in the present application can effectively improve the strength of the poor soil, increase the particle aggregation strength thereof, and reduce the liquid limit thereof, so that the poor soil can be applied to roadbeds, trenches, and pipe gallery filling. Moreover, the solidifying agent in the present application can also fix carbon dioxide and reduce the use amount of cement, thereby achieving green energy saving.

[0046] Preferably, in some embodiments, in order to facilitate the mixing of the solidifying agent and the engineering spoil, the engineering spoil is dried before mixing, so that the water content thereof is ≤40 wt%. Specifically, the engineering spoil can be dried by air drying, filter pressing, drying, or the like, but is not limited thereto. More preferably, in some embodiments, the engineering spoil is filter pressed to a water content of 35 wt% to 40 wt% by a filter pressing process, and then mixed with the solidifying agent.

[0047] Specifically, the content of the solidifying agent in the mixture is ≥15 wt% to improve the strength of the engineering spoil. Preferably, the content of the solidifying agent in the mixture is 15 wt% to 25 wt%.

[0048] Specifically, the carbonization reaction has a duration of 10 h to 20 h, a temperature of 15℃ to 35℃, and a relative humidity of 50% to 70%. Preferably, the carbonization reaction has a duration of 10 h to 14 h, and by controlling the specific phase composition of the steel slag, the duration of the carbonization reaction can be effectively shortened.

[0049] The present application is further described below with specific examples.

[0050] Example 1

[0051] The present example provides a solidifying agent for engineering spoil, which is composed of the following components in parts by weight:

[0052] 20 parts of steel slag and 80 parts of slag.

[0053] In the steel slag, the content of RO phase is 12.5 wt%, the content of glass phase is 12.3 wt%, the content of dicalcium silicate phase is 57.4 wt%, and the content of tricalcium silicate phase is 6.2 wt%.

[0054] In the slag, the content of glass phase is 80.5 wt%, and the content of dicalcium silicate phase is 8.5 wt%.

[0055] The preparation method of the solidifying agent in the present example is as follows: the steel slag and the slag are uniformly mixed, and the solidifying agent is obtained.

[0056] Example 2

[0057] The present example provides a solidifying agent for engineering spoil, which is composed of the following components in parts by weight:

[0058] Steel slag 60 parts, slag 40 parts.

[0059] The content of RO phase in the steel slag is 28.5wt%, the content of glass phase is 5.6wt%, the content of dicalcium silicate phase is 51.8wt%, and the content of tricalcium silicate phase is 3.3wt%.

[0060] The content of glass phase in the slag is 95.3wt%, and the content of dicalcium silicate phase is 1.4wt%.

[0061] The preparation method of the solidifying agent in the embodiment is as follows: the steel slag and the slag are uniformly mixed, and the solidifying agent is obtained.

[0062] Example 3

[0063] The embodiment provides a solidifying agent for engineering spoil, which is composed of the following components in parts by weight:

[0064] Steel slag 25 parts, slag 75 parts.

[0065] The content of RO phase in the steel slag is 17.6wt%, the content of glass phase is 4.5wt%, the content of dicalcium silicate phase is 66.6wt%, and the content of tricalcium silicate phase is 3.9wt%.

[0066] The content of glass phase in the slag is 87.4wt%, and the content of dicalcium silicate phase is 5.8wt%.

[0067] The preparation method of the solidifying agent in the embodiment is as follows: the steel slag and the slag are uniformly mixed, and the solidifying agent is obtained.

[0068] Example 4

[0069] The embodiment provides a solidifying agent for engineering spoil, which is composed of the following components in parts by weight:

[0070] Steel slag 25 parts, slag 75 parts.

[0071] The content of RO phase in the steel slag is 22.4wt%, the content of glass phase is 8.3wt%, the content of dicalcium silicate phase is 58.5wt%, and the content of tricalcium silicate phase is 2.7wt%.

[0072] The content of glass phase in the slag is 89.6wt%, and the content of dicalcium silicate phase is 4.3wt%.

[0073] The preparation method of the solidifying agent in the embodiment is as follows: the steel slag and the slag are uniformly mixed, and the solidifying agent is obtained.

[0074] Comparative Example 1

[0075] The comparative example directly uses the steel slag in the example 1 as the solidifying agent.

[0076] Comparative Example 2

[0077] This comparative example directly uses the slag in Example 1 as the solidifying agent.

[0078] Test Example

[0079] This test example provides a method for using the solidifying agent, which specifically comprises:

[0080] (1) uniformly mixing the construction spoil and the solidifying agent to obtain a mixture;

[0081] The initial water content of the construction spoil is 94.5%, and the unmeasured line compressive strength is 35 kPa. The construction spoil is dried by pressure filtration to a water content of 38.5 wt%, and then uniformly mixed with the solidifying agent in Example 1-4 and Comparative Example 1-2. The content of the solidifying agent in the obtained mixture is 22.5 wt%.

[0082] (2) performing carbonization reaction on the mixture under a carbon dioxide atmosphere to obtain solidified soil.

[0083] The temperature of the carbonization reaction is 25°C, the relative humidity is 60%, the pressure is 0.22 MPa, and the reaction time is as shown in Table 1.

[0084] Comparative Test Example

[0085] This comparative example provides a method for using the solidifying agent, which specifically comprises:

[0086] (1) uniformly mixing the construction spoil and the solidifying agent to obtain a mixture;

[0087] The initial water content of the construction spoil is 94.5%, and the unmeasured line compressive strength is 35 kPa. The construction spoil is dried by pressure filtration to a water content of 38.5 wt%, and then uniformly mixed with the solidifying agent in Example 1. The content of the solidifying agent in the obtained mixture is 22.5 wt%.

[0088] (2) curing the mixture under an air atmosphere to obtain solidified soil.

[0089] The curing time is 20 h, the relative humidity is 60 wt%, and the pressure is normal pressure.

[0090] Experiments are performed on the solidified soil obtained in the test example and the comparative test example, specifically as follows:

[0091] (1) precipitation rate: test the water content of the construction spoil before and after solidification, and calculate the precipitation rate; precipitation rate = (water content of the construction spoil before solidification - water content of the construction spoil after solidification) / water content of the construction spoil before solidification; it should be noted that the water content of the construction spoil before solidification is based on the water content after pressure filtration drying.

[0092] (2) Weight gain rate: take two portions of the same mass of engineering spoil, one of which is completely dried and tested for mass m2; the other portion is subjected to solidification experiment according to the procedure of the test example, and the mass m1 of the obtained solidified soil after complete drying is measured, and the weight gain rate is calculated according to the following formula:

[0093] W = (m1-m2) / (m2*m3)

[0094] In the formula: m1 is the dried mass of the solidified engineering spoil / g, m2 is the dried mass of the solidified engineering spoil / g, and m3 is the dosage of the solidifying agent in the test piece / g;

[0095] (3) Unconfined compressive strength: tested according to the “Highway Engineering Inorganic Binder Stabilized Material Test Procedure” (JTG 3441-2024);

[0096] (4) Porosity: tested by the mercury intrusion test method.

[0097] The specific test results are shown in Table 1:

[0098] Table 1: Solidification time of the solidifying agent and properties of the solidified soil obtained by solidification

[0099]

[0100]

[0101] As can be seen from Table 1, the solidifying agent in the present application can effectively solidify poor quality engineering spoil, improve its unconfined compressive strength, and reduce its porosity. As can be seen from the comparison of Comparative Example 1, Comparative Example 2 and Example 1, if only one of steel slag or slag is used, the improvement in the strength of the engineering spoil is limited. As can be seen from the comparison of the test example and the comparative test example, if carbonization solidification is not performed, it is also difficult to greatly improve the strength of the engineering spoil in a short time.

[0102] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, however, as long as the combinations of the technical features do not contradict each other, they should be considered within the scope of the present disclosure. The above-described embodiments only express several implementation manners of the present application, which are convenient for understanding the technical solutions of the present application in detail, but should not be considered as limitations on the scope of patent protection. It should be noted that, for those skilled in the art, without departing from the concept of the present application, some modifications and improvements can be made, which are within the scope of protection of the present application.

[0103] It should be understood that, on the basis of the technical solutions provided by the present application, the technical solutions obtained by logical analysis, reasoning or limited experiments by those skilled in the art are within the protection scope of the appended claims of the present application. Therefore, the protection scope of the present application patent should be subject to the content of the appended claims, and the description can be used to explain the content of the claims.

Claims

1. A curing agent for engineering spoil, characterized in that: The composition comprises the following components in parts by weight: 20 to 60 parts of steel slag and 40 to 80 parts of mineral slag; the sum of the weight of the steel slag and the mineral slag is 100 parts.

2. The curing agent for engineering spoil according to claim 1, wherein The content of the RO phase in the steel slag is ≥15 wt %, the content of the glass phase is ≤10 wt %, and the total content of the tricalcium silicate phase and the dicalcium silicate phase is ≥60 wt %.

3. The curing agent for engineering spoil according to claim 1, wherein The content of the RO phase in the steel slag is 18wt% to 25wt%, the content of the glass phase is 5wt% to 10wt%, and the total content of the tricalcium silicate phase and the dicalcium silicate phase is 60wt% to 65wt%; The ratio of the content of the dicalcium silicate phase to the content of the tricalcium silicate phase is ≥15.

4. The curing agent for engineering spoil according to any one of claims 1 to 3, characterized in that: The ratio of the content of the dicalcium silicate phase to the content of the tricalcium silicate phase in the steel slag is 18-25.

5. The curing agent for engineering spoil according to claim 1, characterized in that: The content of the glass phase in the slag is ≥85wt%, and the content of the dicalcium silicate phase is ≥3wt%.

6. The curing agent for engineering spoil according to claim 4, characterized in that: The content of the glass phase in the slag is 85wt% to 92wt%, and the content of the dicalcium silicate phase is 3wt% to 6wt%.

7. A method for preparing a curing agent for engineering spoil, for preparing the curing agent for engineering spoil according to any one of claims 1 to 6, characterized in that: include: Mix steel slag and ore slag evenly to obtain the product.

8. A method for using the curing agent according to any one of claims 1 to 6, characterized in that: include: Uniformly mixing the engineering waste soil and the curing agent to obtain a mixture; wherein the content of the curing agent in the mixture is ≥15wt%; The mixture is subjected to a carbonization reaction under a carbon dioxide atmosphere to obtain solidified soil.

9. The method for using the curing agent according to claim 8, wherein: In the step of subjecting the mixture to carbonization reaction under a carbon dioxide atmosphere to obtain solidified soil, the carbonization reaction time is 10 hours to 15 hours, the temperature is 15° C. to 35° C., and the relative humidity is 50% to 70%.

10. The method for using the curing agent according to claim 8, wherein: The moisture content of the engineering spoil is ≤40wt%; The content of the curing agent in the mixture is 15 wt % to 25 wt %.

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