Regenerated solidified soil as well as preparation method and application thereof

Abstract

The invention discloses regenerated solidified soil as well as a preparation method and application thereof, and belongs to the technical field of building materials and resource utilization. The regenerated solidified soil comprises the following raw materials: waste solidified soil, a precursor, an alkali activator and water. According to the method, the waste solidified soil is used for replacing natural soil to serve as a main raw material, an alkali-activated material (a precursor and an alkali activator) is used as a cementing material to achieve re-solidification of the waste solidified soil, and the regenerated solidified soil is obtained. According to the method, waste utilization can be more effectively achieved by utilizing the physicochemical properties of the waste solidified soil, harmless treatment and resource utilization of the waste solidified soil can be achieved through the method, compared with traditional solidified soil, building materials with better physical and mechanical properties can be obtained, carbon emission is remarkably reduced, and environmental protection is achieved. And green development of the building industry is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials and resource utilization, and in particular to a regenerated solidified soil and a preparation method and application thereof. Background Art

[0002] Solidified soil is a technology for chemically improving soil. It is usually made by mixing an inorganic solidifier with soil (including ordinary soil or engineering slag) to form solidified soil. The chemical reaction products of the inorganic solidifier are used to bond soil particles to achieve soil solidification. Solidified soil is usually used for building materials (for example: cement walls, earth-based unburned bricks / blocks) or filling of various roads and building foundations. Solidified soil is widely used in various scenarios, and is usually used in large quantities (such as solidified soil in foundations and roadbeds). However, any building material has a service life. When its service life is reached, it will be discarded and become construction waste. This leads to the generation of a large amount of abandoned solidified soil, and the subsequent disposal of waste will face the problem of waste.

[0003] In addition, in recent years, with the development of a large number of infrastructure projects, a large amount of construction waste has been generated. In response to the needs of waste-free cities and green development of the construction industry, the resource utilization technology of construction waste will gradually replace the traditional high-energy consumption, high-carbon emission, and high-pollution transportation and landfill methods. Among them, the preparation of solidified soil is an important waste resource technology and has been widely used. In this context, a larger amount of waste solidified soil may be generated in the future and need to be disposed of, which further exacerbates the demand for the disposal of waste solidified soil.

[0004] At present, the method of treating waste solidified soil is still mainly transportation and landfill, but this will lead to environmental pollution problems, because the waste solidified soil contains alkaline substances, which are easy to dissolve and pollute groundwater after landfill. According to the type and dosage of the curing agent previously added to the solidified soil, the pH value of the soluble alkaline liquid can reach 10-12. In addition, the pollutants (such as heavy metals) that have been successfully fixed by the solidified soil are also easy to dissolve again and pollute the environment due to the landfill treatment of the waste solidified soil. Therefore, it is very important to recycle and reuse the waste solidified soil. However, there is currently a lack of attention to the recycling of waste solidified soil, and no method for the recycling of waste solidified soil has been found. Therefore, the development of a method for the recycling and utilization of waste solidified soil has a very broad application prospect. Summary of the invention

[0005] The purpose of the present invention is to provide a regenerated solidified soil and a preparation method and application thereof, so as to solve the problems existing in the above-mentioned prior art. The present invention uses waste solidified soil instead of natural soil (or engineering slag) as the main raw material, and adopts alkali-activated materials (including precursors and alkali activators) as cementitious materials. Under the action of alkali-activated materials, the waste solidified soil is solidified again to obtain regenerated solidified soil, thereby realizing the recycling of waste solidified soil (this process can be called alkali-activated regenerated solidified soil, that is, regenerating waste solidified soil through alkali activation). Compared with the use of traditional cement, lime and other cementitious materials, the use of alkali-activated materials as cementitious materials can additionally activate the active silicon and aluminum components remaining in the waste solidified soil and use them as supplementary cementitious materials, which is beneficial to improve the physical and mechanical properties of the regenerated solidified soil.

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

[0007] One of the technical solutions of the present invention is to provide a regenerated solidified soil, wherein the raw materials include, by weight:

[0008] 50-100 parts of waste solidified soil, 5-50 parts of precursor, 1-10 parts of alkali activator and 15-100 parts of water.

[0009] The precursor and the alkali activator together constitute the alkali-activated material (a new type of gelling material based on the principle of alkali-activated reaction).

[0010] Furthermore, the waste solidified soil is waste generated when solidified soil formed by mixing soil and cementitious materials is used and then discarded.

[0011] Furthermore, the waste solidified soil includes but is not limited to at least one of waste clay unburned bricks, waste soil unburned bricks, solidified soil roadbed, solidified soil foundation, solidified soil pile foundation (such as cement mixing pile) and fluidized solidified soil filler. These waste solidified soils come from common projects, and are essentially solidified soils formed by mixing soil (including ordinary soil and engineering waste soil) with cementitious materials (mainly cement, lime, alkali-activated materials, etc.). When these solidified soils are damaged, re-excavated, and abandoned, they become the waste solidified soils.

[0012] Furthermore, the engineering waste soil includes waste soil from multiple sources such as construction foundation pit waste soil, subway shield waste soil, road excavation waste soil, etc., and its main component is soil.

[0013] Furthermore, the precursor is a substance that can be activated and dissolved by an alkaline activator to produce free silicon, aluminum, and calcium elements, and has a particle size of no more than 0.075 mm (used in the form of powder).

[0014] Furthermore, the precursor includes, but is not limited to, one or more of slag, fly ash, metakaolin, recycled brick powder, steel slag, carbide slag, red mud and calcined sludge. The present invention does not explicitly limit the type of precursor, and any substance that can be activated by an alkaline activator and dissolved to produce free silicon, aluminum, calcium and other elements belongs to the precursor of the present invention.

[0015] Furthermore, when one or more of recycled brick powder, steel slag, carbide slag, red mud and calcined sludge are used as precursors, the activity of these materials may be insufficient, and a certain proportion of slag, fly ash or kaolin can be added to improve the activity, with the addition amount being 10 to 90 wt % of the former.

[0016] Furthermore, the alkaline activator includes water glass, NaOH, KOH, Ca(OH) 2 and Na 2 CO 3 The base activator acts as a catalyst to promote the base activation reaction.

[0017] Furthermore, the modulus of the water glass is 3.0-3.3.

[0018] The second technical solution of the present invention: the preparation method of the above-mentioned regenerated solidified soil (i.e., the method of alkali-activated regenerated solidified soil) comprises the following steps:

[0019] The waste solidified soil is dried and crushed to obtain pre-treated waste solidified soil;

[0020] Evenly mixing the alkaline activator and water to obtain an alkaline activator solution;

[0021] The pretreated waste solidified soil, the precursor and the alkaline activator solution are mixed evenly to obtain the regenerated solidified soil.

[0022] Furthermore, the particle size of the pretreated waste solidified soil is not higher than 4.75 mm.

[0023] Furthermore, when the alkali activator includes water glass, the alkali activator and water are mixed evenly, and the modulus of the obtained alkali activator solution is 0.5-2.

[0024] The third technical solution of the present invention: application of the above-mentioned regenerated solidified soil in construction projects.

[0025] Furthermore, the application specifically includes the following three forms:

[0026] Form 1: forming and curing the regenerated solidified soil to obtain unfired bricks or unfired blocks;

[0027] Form 2: Using the recycled solidified soil as filling material for roadbed, foundation or pile foundation;

[0028] Form three: using the regenerated solidified soil as fluidized solidified soil backfill material for pouring and backfilling fluidized solidified soil.

[0029] Through the above three forms, the regenerated solidified soil can be made into different products, or directly applied in various scenarios.

[0030] Furthermore, it is preferred to carry out in-situ application at the site where the waste solidified soil is produced.

[0031] The alkali-activated regenerated solidified soil described in the present invention specifically refers to a process in which waste solidified soil is used instead of natural soil (or engineering slag) as the main raw material, and alkali-activated materials (including precursors and alkali activators) are used as gelling materials. Under the action of alkali-activated materials, the waste solidified soil is solidified again to obtain regenerated solidified soil, thereby realizing the recycling of waste solidified soil. The product obtained in this process is the regenerated solidified soil described in the present invention.

[0032] In the present invention, the dosage of precursor and alkali activator can be adaptively regulated according to the specific application scenario and the physical and mechanical properties of the prepared product. The higher the dosage, the better the physical and mechanical properties. The amount of water is regulated according to the type of product to be prepared and the fluidity and physical and mechanical properties required for the specific application scenario. The higher the amount of water, the better the fluidity, the lower the density and compressive strength. For example, if fluidized solidified soil requires high fluidity, a higher amount of water is required, while solidified soil roadbed filler or unfired bricks require a lower amount of water.

[0033] The present invention adopts alkali-activated materials as cementitious materials, which have better curing effect and environmental impact. Compared with traditional curing agents such as cement and lime, the curing effect is better and the carbon emission is lower. Moreover, slag, fly ash, steel slag and recycled brick powder are common industrial and construction solid wastes, which have high volcanic ash activity and can be used as alkali-activated precursors to generate geopolymers under the catalytic action of alkali activators. The geopolymers have high-quality mechanical properties and durability, are very potential building materials, and are also high-quality and low-carbon cementitious materials. The active substances remaining in the abandoned solidified soil, such as residual unhydrated cement particles, unreacted slag / fly ash, etc., calcium hydroxide, etc., are rich in active silicon, aluminum, calcium and other elements, which can be reactivated under the catalytic action of alkali activators, play a role similar to that of precursors, and are fully utilized as active ingredients during re-curing, so that the total amount of precursors of the regenerated solidified soil is increased, which is conducive to improving the physical and mechanical properties of the regenerated solidified soil.

[0034] The principle of soil solidification is the chemical reaction of the cementitious material to generate gel and hydration products and bond soil particles, and the flocculation of soil particles and free alkali metal cations. Based on the reaction principle of soil solidification, the reaction principle of the present invention for preparing regenerated solidified soil adds the following parts:

[0035] (1) Physical principle: In the abandoned solidified soil, some soil particles have been consolidated, agglomerated and hardened, and the clay particles have been solidified, which will change their physical and chemical properties. These solidified clay particles will no longer absorb water and swell and adsorb cations, and their physical and chemical properties are more stable. Therefore, these solidified clay particles can be regarded as sand particles. Overall, it can be considered that the sand content of the abandoned solidified soil has increased, which in turn leads to better working performance of the recycled solidified soil than ordinary solidified soil, and the compressive strength is also improved.

[0036] (2) Chemical principle: After the solidified soil is discarded, some active substances will still remain in it, such as residual unhydrated cement particles, unreacted slag / fly ash, calcium hydroxide, etc. These active substances are re-excited under the catalytic action of the alkaline activator and participate in the alkaline excitation reaction to generate more reaction products, thereby improving the physical and mechanical properties of the regenerated solidified soil.

[0037] The present invention discloses the following technical effects:

[0038] (1) The present invention uses waste solidified soil instead of natural soil as the main raw material to prepare solidified soil. The waste solidified soil used contains alkaline substances, which are essentially active substances remaining from inorganic solidifying agents. They are rich in active silicon, aluminum, calcium and other elements, and can be effectively activated by alkaline activators. They are fully utilized as active ingredients during re-solidification, which is beneficial to improving the physical and mechanical properties of regenerated solidified soil. Moreover, re-solidification can also avoid the re-dissolution of pollutants (such as heavy metals), which is beneficial to protecting the environment.

[0039] (2) The present invention proposes for the first time to recycle waste solidified soil, filling the technical gap in the life cycle of solidified soil materials from dismantling and discarding to recycling. In the past, the main method of disposing of waste solidified soil was transportation and landfill, which had the disadvantages of environmental pollution, high disposal cost, and high carbon emissions. The technical path of the present invention not only solves the environmental pollution problem caused by waste solidified soil, but also realizes the transformation of waste into treasure, generating recycled solidified soil products with higher performance and higher quality than ordinary solidified soil.

[0040] (3) Compared with traditional curing agents such as cement and lime used in traditional solidified soil, the present invention uses alkali-activated materials as curing agents, which not only have better curing effects than cement and lime, but also have lower carbon emissions. In addition, alkali-activated materials can effectively utilize the active substances remaining in the waste solidified soil, further improving the performance of the regenerated solidified soil, making the regenerated solidified soil not only a resource utilization strategy for waste solidified soil, but also a performance optimization strategy for solidified soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0042] Figure 1 The technical route for the preparation method and application of regenerated solidified soil;

[0043] Figure 2 The compressive strength of the solidified soil obtained in Examples 1 to 4 and Comparative Example 1 after curing for 7 days and 28 days;

[0044] Figure 3 The compressive strength of the solidified soil obtained in Examples 5-6 and Comparative Examples 2-3 after curing for 7 days and 28 days. DETAILED DESCRIPTION

[0045] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0046] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0047] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0048] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0049] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0050] Figure 1 The invention relates to a preparation method and application technical route of regenerated solidified soil (wherein the regenerated solidified soil raw material represents pre-treated waste solidified soil particles).

[0051] The raw materials and reagents used in the specific implementation of the present invention are all commercially available products, among which the modulus of directly purchased water glass is 3.0-3.3. When water glass is used as an alkaline activator, it needs to be mixed with a strong base to adjust the modulus, that is, in addition to water glass, a strong base (NaOH, KOH, Ca(OH) 2 and Na 2 CO 3 ), the modulus of the water glass (i.e., the alkaline activator solution obtained by mixing purchased water glass, strong alkali and water) in actual use is 0.5-2.

[0052] In some specific embodiments, the waste solidified soil used is waste slag brick (waste slag brick), which is a waste slag brick prepared by using alkali-activated slag as a cementitious material to solidify engineering slag. By weight, the raw materials for preparing the slag brick are: 100 parts of engineering slag, 30 parts of slag, 3.0 parts of NaOH, 4.7 parts of water glass, and 55.5 parts of water; wherein the modulus of water glass is 3.26 and the solid content is 35.5wt%. The preparation method is: put it into a mold, compact it, form the required brick shape, and then cure it under standard curing conditions (temperature 20±2℃, relative humidity ≥90%).

[0053] In some specific embodiments, the waste solidified soil used is cement solidified soil waste, which is a waste cement solidified soil prepared by using cement as a cementitious material to solidify construction waste soil. The raw materials for its preparation are, by weight, 100 parts of construction waste soil, 30 parts of ordinary Portland cement (PO 42.5), and 52 parts of water. The preparation method is: curing under standard curing conditions (temperature 20±2°C, relative humidity ≥90%).

[0054] The "parts" mentioned in the specific embodiments of the present invention are parts by mass unless otherwise specified.

[0055] The technical solution of the present invention is further described below through specific embodiments.

[0056] Example 1

[0057] A preparation method of regenerated solidified soil comprises the following steps:

[0058] S1. Dry and crush the solidified soil unfired brick waste to a particle size of less than 2 mm to obtain pretreated waste solidified soil particles for later use; wherein the solidified soil unfired brick waste is the alkali-activated solidified soil waste in Comparative Example 1, and its components include 54.6wt% silicon oxide, 27.1wt% aluminum oxide, 6.1wt% calcium oxide, 6.6wt% iron oxide, 1.5wt% sodium oxide, 1.3wt% magnesium oxide and the remaining components with a content of less than 1wt%.

[0059] S2, 3 parts of NaOH, 4.7 parts of water glass (modulus of 3.26, solid content of 35.5wt%) and 55.5 parts of water were mixed and allowed to stand for one day to obtain an alkaline activator solution (modulus of 0.5);

[0060] S3, take 100 parts of the waste solidified soil particles pretreated in S1 and 30 parts of S95 grade slag (particle size <0.075mm), mix them evenly, then add the alkali activator solution prepared in S2 and mix them evenly to obtain a regenerated solidified soil mixture.

[0061] Example 2

[0062] A preparation method of regenerated solidified soil comprises the following steps:

[0063] S1, drying the solidified soil unburned brick waste (same as in Example 1) and crushing it to a particle size of less than 2 mm to obtain pre-treated waste solidified soil particles for later use;

[0064] S2, 2.5 parts of NaOH, 3.9 parts of water glass (modulus of 3.26, solid content of 35.5wt%) and 53.7 parts of water were mixed and allowed to stand for one day to obtain an alkaline activator solution (modulus of 0.5);

[0065] S3, take 100 parts of the waste solidified soil particles pretreated in S1 and 25 parts of S95 grade slag (particle size <0.075mm), mix them evenly, then add the alkali activator solution prepared in S2 and mix them evenly to obtain a regenerated solidified soil mixture.

[0066] Example 3

[0067] A preparation method of regenerated solidified soil comprises the following steps:

[0068] S1, drying the solidified soil unburned brick waste (same as in Example 1) and crushing it to a particle size of less than 2 mm to obtain pre-treated waste solidified soil particles for later use;

[0069] S2, 2.0 parts of NaOH, 3.2 parts of water glass (modulus of 3.26, solid content of 35.5wt%) and 52.7 parts of water were mixed and allowed to stand for one day to obtain an alkaline activator solution (modulus of 0.5);

[0070] S3, take 100 parts of the waste solidified soil particles pretreated in S1 and 20 parts of S95 grade slag (particle size <0.075mm), mix them evenly, then add the alkali activator solution prepared in S2 and mix them evenly to obtain a regenerated solidified soil mixture.

[0071] Example 4

[0072] A preparation method of regenerated solidified soil comprises the following steps:

[0073] S1, after drying, the solidified soil unburned brick waste (same as in Example 1) is crushed to a particle size of less than 2 mm to obtain pre-treated waste solidified soil particles for later use

[0074] S2, 2.0 parts of NaOH, 3.2 parts of water glass (modulus of 3.26, solid content of 35.5wt%) and 52.7 parts of water were mixed and allowed to stand for one day to obtain an alkaline activator solution (modulus of 0.5);

[0075] S3, take 100 parts of the waste solidified soil particles pretreated in S1 and 20 parts of Class C primary fly ash and mix them evenly, then add the alkali activator solution prepared in S2 and mix them evenly to obtain a regenerated solidified soil mixture.

[0076] Example 5

[0077] A preparation method of regenerated solidified soil comprises the following steps:

[0078] S1. After drying, the cement-solidified soil waste is crushed to a particle size of less than 2 mm to obtain pretreated waste solidified soil particles for later use; wherein the cement-solidified soil waste is the cement-solidified soil waste in Comparative Example 2, and its components include 53.8wt% silicon oxide, 26.6wt% aluminum oxide, 8.0wt% calcium oxide, 7.8wt% iron oxide, 0.3wt% sodium oxide, 0.6wt% magnesium oxide, 1.1wt% potassium oxide and the remaining components whose contents are all less than 1wt%.

[0079] S2, 3.1 parts of NaOH, 4.8 parts of water glass (modulus of 3.26, solid content of 35.5wt%) and 48.9 parts of water were mixed and allowed to stand for one day to obtain an alkaline activator solution (modulus of 0.5);

[0080] S3, take 100 parts of the waste solidified soil particles pretreated in S1 and 30 parts of S95 grade slag (particle size <0.075mm), mix them evenly, then add the alkali activator solution prepared in S2 and mix them evenly to obtain a regenerated solidified soil mixture.

[0081] Example 6

[0082] A preparation method of regenerated solidified soil comprises the following steps:

[0083] S1, drying the cement-solidified soil waste (same as in Example 5) and crushing it to a particle size of less than 2 mm to obtain pre-treated waste solidified soil particles for later use;

[0084] S2, 3.1 parts of NaOH, 4.8 parts of water glass (modulus of 3.26, solid content of 35.5wt%) and 48.9 parts of water were mixed and allowed to stand for one day to obtain an alkaline activator solution (modulus of 0.5);

[0085] S3, take 100 parts of the waste solidified soil particles pretreated in S1 and 30 parts of Class C primary fly ash and mix them evenly, then add the alkali activator solution prepared in S2 and mix them evenly to obtain a regenerated solidified soil mixture.

[0086] Comparative Example 1

[0087] A preparation method of alkali activated solidified soil comprises the following steps:

[0088] S1. Raw material preparation: 100 parts of construction slag, 30 parts of S95 grade slag (particle size <0.075mm), 3.0 parts of NaOH, 4.7 parts of water glass (modulus is 3.26, solid content is 35.5wt%), and 55.5 parts of water; wherein, the construction slag is yellow fully weathered slate with a particle size of 0 to 0.075mm, a plastic limit of 31.68%, a liquid limit of 66.01%, and a plasticity index of 34.33, and is a high liquid limit clay.

[0089] S2, NaOH, water glass and water are mixed evenly and left to stand for one day to obtain an alkaline activator solution (modulus is 0.5);

[0090] S3, mixing the construction waste soil and slag evenly, then adding the alkali activator solution prepared in S2 and mixing evenly to obtain an alkali-activated solidified soil mixture (actually the raw material of the solidified soil unfired brick waste used in Examples 1 to 3).

[0091] Comparative Example 2

[0092] A preparation method of cement-solidified soil comprises the following steps:

[0093] S1. Raw material preparation: 100 parts of construction waste soil, 30 parts of ordinary Portland cement (PO 42.5), and 52 parts of water; the construction waste soil is yellow fully weathered slate with a particle size of 0 to 0.075 mm, a plastic limit of 31.68%, a liquid limit of 66.01%, and a plasticity index of 34.33, which is a high liquid limit clay.

[0094] S2. Mix the construction waste soil, slag and water evenly to obtain a cement-solidified soil mixture (actually the raw material of the cement-solidified soil waste used in Example 4).

[0095] Comparative Example 3

[0096] A preparation method of recycled cement-solidified soil comprises the following steps:

[0097] S1, drying the cement-solidified soil waste (same as in Example 5) and crushing it to a particle size of less than 2 mm to obtain pre-treated waste solidified soil particles for later use;

[0098] S2. Take 100 parts of the waste solidified soil particles pretreated in S1, 30 parts of cement and 52 parts of water and mix them evenly to obtain a recycled cement solidified soil mixture.

[0099] Test example

[0100] 1. Liquidity test

[0101] The fluidity of the solidified soil mixtures prepared in Examples 1 to 6 and Comparative Examples 1 to 3 was tested in accordance with the Standard for Test Methods for Basic Properties of Building Mortar JGJ70-2009. The results are shown in Table 1.

[0102] Table 1 Solidified soil formula design (by mass fraction) and measured fluidity values

[0103]

[0104] 2. Mechanical properties test

[0105] The solidified soils prepared in Examples 1 to 4 and Comparative Example 1 were cast and cured under standard curing conditions (temperature 20±2°C, relative humidity ≥90%), and the compressive strength after curing for 7 and 28 days was tested. The results are as follows: Figure 2 shown.

[0106] Figure 2 The compressive strength of the solidified soil obtained in Examples 1 to 4 and Comparative Example 1 after curing for 7 days and 28 days. It can be seen from the figure that compared with Comparative Example 1 (equivalent to the predecessor of the waste solidified soil used in Examples 1 to 4, which can be regarded as the original solidified soil), when the waste solidified soil is used as the raw material (Examples 1 to 4), the compressive strength of the regenerated solidified soil is greatly improved under the same cementitious material formula (Example 1). Even if the cementitious material dosage of Example 2 is reduced by 17% (from 30 parts of slag to 25 parts of slag), the compressive strength is still higher than that of Comparative Example 1.

[0107] The solidified soils prepared in Examples 5 to 6 and Comparative Examples 2 to 3 were cast and cured under standard curing conditions (temperature 20±2°C, relative humidity ≥90%). The compressive strength after curing for 7 and 28 days was tested. The results are as follows: Figure 3 shown.

[0108] Figure 3 The compressive strength of the solidified soil obtained in Examples 5-6 and Comparative Examples 2-3 after curing for 7 days and 28 days. It can be seen from the figure that, relative to Comparative Example 2 (equivalent to the predecessor of the waste solidified soil used in Examples 5-6, which can be regarded as the original solidified soil), when waste solidified soil is used as raw material, the compressive strength of the regenerated cement-solidified soil is greatly improved at the same dosage (Comparative Example 3). However, if alkali-activated slag is used as the cementitious material, the strength of the obtained regenerated solidified soil is higher (Examples 5-6).

[0109] Figure 2 and Figure 3 The specific compressive strength values ​​of different stabilized soils are shown in Table 2:

[0110] Table 2

[0111]

[0112] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A regenerated and stabilized soil, characterized in that: By mass, the raw materials include: 50-100 parts of waste solidified soil, 5-50 parts of precursor, 1-10 parts of alkali activator and 15-100 parts of water.

2. The regenerated and stabilized soil according to claim 1, characterized in that: The waste solidified soil is waste generated when solidified soil formed by mixing soil and cementitious materials is used and then discarded.

3. The regenerated and stabilized soil according to claim 1, characterized in that: The precursor is a substance that can be activated and dissolved by an alkali activator to produce free silicon, aluminum and calcium elements, and the particle size is not higher than 0.075 mm.

4. The regenerated and stabilized soil according to claim 1, characterized in that: The alkaline activator includes at least one of water glass, NaOH, KOH, Ca(OH)2 and Na2CO3.

5. The method for preparing regenerated solidified soil according to any one of claims 1 to 4, characterized in that: The following steps are involved: The waste solidified soil is dried and crushed to obtain pre-treated waste solidified soil; Evenly mixing the alkaline activator and water to obtain an alkaline activator solution; The pretreated waste solidified soil, the precursor and the alkaline activator solution are mixed evenly to obtain the regenerated solidified soil.

6. The preparation method according to claim 5, characterized in that: The particle size of the pretreated waste solidified soil is not higher than 4.75 mm.

7. Use of the regenerated solidified soil as claimed in any one of claims 1 to 4 in construction projects.

8. The use according to claim 7, characterized in that The application specifically includes the following three forms: Form 1: forming and curing the regenerated solidified soil to obtain unfired bricks or unfired blocks; Form 2: Using the recycled solidified soil as filling material for roadbed, foundation or pile foundation; Form three: using the regenerated solidified soil as fluidized solidified soil backfill material for pouring and backfilling fluidized solidified soil.

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