High impermeability curing agent for sandy soil and preparation method thereof

Abstract

The application discloses a high-impermeability curing agent for sandy soil and a preparation method thereof. The high-impermeability curing agent is composed of the following components in parts by mass: solid waste-based sulpho-aluminum-iron series cementing material 30-50 parts; slag powder 10-30 parts; ordinary portland cement 5-30 parts; desulfurization gypsum 5-20 parts; and silica fume 1-10 parts. The curing agent system not only further strengthens the hydration and cementing performance of the cementing material, but also contributes to the stability and dense microstructure of the cured sandy soil by forming a crystal-gel composite hydration product system, so that the impermeability and mechanical properties of the sandy soil can be greatly improved. The comprehensive application of the desulfurization gypsum, mineral powder and other solid waste materials is realized, and the accumulation cost of the solid waste and the influence on the environment are reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of curing agents, and particularly relates to a high-impermeability curing agent for sandy soil and a preparation method thereof. BACKGROUND

[0002] The statements herein are provided only to enhance understanding of the application and are not necessarily intended to constitute the prior art.

[0003] Sandy soil has high permeability, and under the influence of rainfall scouring, surface runoff erosion and the like, water can easily enter the inside of the structure, resulting in cracking, collapse and other serious problems, which seriously affect engineering construction and people's life and property safety. Therefore, the sandy soil should be cured with high impermeability to realize its resource utilization. However, the high-impermeability curing of sandy soil is a major technical problem, and ordinary curing materials are difficult to achieve good impermeability curing effect on sandy soil.

[0004] For example, the commonly used curing material, Portland cement, is difficult to fill the pores of sandy soil, thereby resulting in limited improvement of the impermeability of the cured soil, and has the disadvantages of large production energy consumption and carbon emission; the alkali-activated material often uses water glass and other activating materials, which are not uniform, and often needs more than 28 days of curing time to form a good effect of improving the impermeability; the fibrous structure of the hydration product of sulphoaluminate cement, ettringite, can form a network structure in the soil, play a skeleton supporting role and fill the loose soil structure, and can improve the early strength and impermeability of the soil, and is particularly suitable for high-impermeability curing of sandy soil, but the cementing property is not enough to bond the sand particles, resulting in that the improvement of the mechanical properties and impermeability of the cured sandy soil by the sulphoaluminate cement is affected, and the sulphoaluminate cement should be compounded and optimized. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a high-impermeability curing agent for sandy soil and a preparation method thereof.

[0006] In order to achieve the above-mentioned purpose, the present application is realized by the following technical scheme:

[0007] In a first aspect, the present application provides a high-impermeability curing agent for sandy soil, which is composed of the following components in parts by mass: 30-50 parts of solid waste-based sulphoaluminate-ferrous cementitious material; 10-30 parts of slag powder; 5-30 parts of ordinary Portland cement; 5-20 parts of desulfurization gypsum; and 1-10 parts of silica fume.

[0008] The solid waste-based sulphoaluminate-ferrous cementitious material provides ettringite for early rapid hydration and provides early strength; the ettringite is a short rod-shaped crystal, which forms a skeleton structure in the cured soil by mutual lapping, thereby providing stability.

[0009] Slag powder: with pozzolanic activity, Si and Al phases in its chemical composition can be activated in alkaline environment to form C-(A)-S-H gel, providing cementation for the solidified soil system. - C-(A)-S-H gel is generated, providing cementation for the solidified soil system.

[0010] Ordinary Portland cement: itself hydrates to form C-S-H gel, and the generated Ca(OH)2 can provide sufficient OH- for the system, promoting the activation effect of the mineral powder.

[0011] Desulfurized gypsum: composed of CaSO4, stabilizing the form of ettringite and reducing the existence of monosulfate type hydrated calcium aluminate sulfate in the system.

[0012] Silica fume: with pozzolanic activity, Si phase in its chemical composition can be activated in alkaline environment to form C-S-H gel.

[0013] By means of the early strength and impermeability of the solid waste-based sulpho-alumino-ferrous cementitious material, the slag, ordinary Portland cement, desulfurized gypsum, and silica fume are compounded to enrich the types of hydration products, providing a "skeleton-filling-cementation" effect for the sand, and supplementing the colloidal products on the basis of the hydration of sulpho-alumino-ferrous cementitious material to form ettringite crystals, so that the soil, particles, and hydration products are effectively connected, not only further strengthening the hydration and cementation performance of the cementitious material, but also contributing to the stability and dense microstructure of the solidified sand by the crystal-colloid composite hydration product system, which can effectively improve the impermeability and mechanical properties of the sand, realize the resource utilization of the sand, and realize the comprehensive application of desulfurized gypsum, slag, and other solid waste materials, reducing the accumulation cost of solid waste and the impact on the environment.

[0014] In some embodiments, the preparation method of the solid waste-based sulpho-alumino-ferrous cementitious material is as follows: uniformly mixing 30-40 parts of desulfurized gypsum, 10-20 parts of red mud, 20-25 parts of aluminum ash, and 20-30 parts of carbide slag, calcining the mixed raw materials in a kiln for 20-40 min at a temperature of 1150-1300℃ to obtain clinker;

[0015] Mixing 80 parts of clinker, 15 parts of desulfurized gypsum, and 5 parts of limestone powder after drying to prepare the solid waste-based sulpho-alumino-ferrous cementitious material.

[0016] The iron content in the solid waste-based sulpho-alumino-ferrous cementitious material is about 8.35%, and the iron phase can form iron gel to cement the soil particles during cement hydration. The raw materials of the high impermeability solidifier are all derived from solid waste, which is low-carbon and solves the problem of large-scale solid waste disposal.

[0017] Preferably, in the preparation of the solid waste-based sulpho-alumino-ferrous cementitious material, the raw materials are 35-40 parts of desulfurized gypsum, 15-20 parts of red mud, 20-25 parts of aluminum ash, and 25-30 parts of carbide slag.

[0018] Further preferably, the desulfurized gypsum 36 parts, red mud 16 parts, aluminum ash 22 parts and carbide slag 26 parts.

[0019] In some embodiments, the high impermeability curing agent for sandy soil consists of, by mass fraction: solid waste-based sulfur-aluminum-iron-based cementing material 30-40 parts; slag powder 20-30 parts; ordinary Portland cement 10-30 parts; desulfurized gypsum 5-20 parts; silica fume 4-10 parts.

[0020] Preferably, the high impermeability curing agent for sandy soil consists of, by mass fraction: solid waste-based sulfur-aluminum-iron-based cementing material 30-35 parts; slag powder 20-25 parts; ordinary Portland cement 15-20 parts; desulfurized gypsum 15-20 parts; silica fume 4-7 parts.

[0021] In some embodiments, each component in the high impermeability curing agent for sandy soil is subjected to grinding treatment, and the fineness is less than 10% of the residue on a 200-mesh square hole screen.

[0022] In a second aspect, the present application provides a preparation method of the high impermeability curing agent for sandy soil, comprising the following steps:

[0023] The solid waste-based sulfur-aluminum-iron-based cementing material, slag powder, ordinary Portland cement, desulfurized gypsum and silica fume are weighed in proportion, ground to less than 10% of the residue on a 200-mesh square hole screen, and mixed to obtain the high impermeability curing agent for sandy soil.

[0024] In some embodiments, the method for modifying sandy soil using the high impermeability curing agent is: adjusting the water content of the sandy soil, mixing the high impermeability curing agent with the sandy soil at a mass ratio of 5-15:85-95 to obtain a mixed soil material; and preparing a test piece from the mixed soil material.

[0025] Preferably, when modifying the sandy soil, the water content of the sandy soil is 8%-20%.

[0026] Preferably, the mass ratio of the high impermeability curing agent to the sandy soil is 7-12:87-92, preferably 10:90.

[0027] The beneficial effects achieved by one or more embodiments of the present application are as follows:

[0028] The sulphur-aluminum-iron composite cementitious material prepared by the application is suitable for high anti-seepage solidification of sandy soil, and the early strength and anti-seepage characteristics of the solid waste-based sulphur-aluminum-iron composite cementitious material are used to compound slag, ordinary portland cement, desulfurization gypsum, silica fume and the like, so that the types of hydration products are enriched, the "skeleton-filling-cementation" effect is provided for the sandy soil, the colloid product is supplemented on the basis of the calcium aluminate crystal formed by the hydration of the sulphur-aluminum-iron composite cementitious material, the soil, particles and hydration products are effectively connected, the hydration and cementation performance of the cementitious material is further strengthened, the crystal-colloid composite hydration product system contributes to the stability and dense microstructure of the solidified sandy soil, the anti-seepage and mechanical properties of the sandy soil are effectively improved, the resource utilization of the sandy soil is realized, and the comprehensive application of the solid waste raw materials such as desulfurization gypsum and mineral powder is realized, so that the accumulation cost of solid waste and the influence on the environment are reduced.

[0029] In terms of performance, the high anti-seepage solidifying agent has good compressive and flexural strength, and superior mechanical properties. When the high anti-seepage solidifying agent is applied to solidify sandy soil, the anti-seepage coefficient of the sandy soil completely exceeds the engineering requirements of dam fillers. This invention not only provides important technical guidance for the current solidification of sandy soil, but also promotes the resource utilization of sandy soil and environmental sustainable development.

[0030] When the high anti-seepage solidifying agent is used to solidify sandy soil, the solidification efficiency is high, and relatively fast solidification can be achieved, thereby improving the work efficiency.

[0031] The prepared high anti-seepage solidifying agent has the advantages of early strength, high strength and stable strength improvement, and the compressive and flexural strength is greatly improved compared with ordinary sulphoaluminate cement, and has superior mechanical properties.

[0032] The 7d anti-seepage coefficient of the sandy soil solidified by the prepared high anti-seepage solidifying agent reaches 5.9x10 -7 cm / s, which meets the general soil anti-seepage material quality technical index (≤1x10 -5 ) in the relevant national regulations, and the performance improvement speed is fast and the effect is good.

[0033] The prepared high anti-seepage solidifying agent uses multiple solid wastes (mineral powder and desulfurization gypsum) to replace the cement clinker, thereby reducing the calcination cost, and the cost is reduced by more than half compared with traditional sulphoaluminate cement.

[0034] The prepared high anti-seepage solidifying agent has a large amount of solid waste, thereby reducing the accumulation cost of solid waste and the influence on the environment, and reducing the energy consumption and carbon emissions in the production process.

[0035] The preparation process is simple, the modification method for the sandy soil is simple, the prepared high anti-seepage solidifying agent is simple to use, and the mechanical use difficulty is low. BRIEF DESCRIPTION OF DRAWINGS

[0036] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application and are incorporated herein by reference. The illustrations are of exemplary embodiments of the application and explain the principles of the application, but do not limit the application.

[0037] Figure 1 is a process flow diagram of the present application. DETAILED DESCRIPTION

[0038] It should be noted that the following detailed description is merely illustrative, and is intended to provide further description of the application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0039] The application will be further described with reference to the following examples.

[0040] Example 1

[0041] A high impermeability stabilizer for sand soil solidification, which is composed of the following components in mass fraction: solid waste-based sulfur-aluminum-iron-based cementitious material 35 parts, slag powder 30 parts, ordinary portland cement 15 parts, desulfurization gypsum 5 parts, silica fume 15 parts.

[0042] The preparation method of the solid waste-based sulfur-aluminum-iron-based cementitious material is as follows: 36 parts of desulfurization gypsum, 16 parts of red mud, 22 parts of aluminum ash, and 26 parts of carbide slag are mixed, and the mixed raw materials are added to a kiln for calcination for 30 min at a calcination temperature of 1250℃, to obtain a sulfur-aluminum clinker;

[0043] The sulfur-aluminum clinker 80 parts, desulfurization gypsum 15 parts, and limestone powder 5 parts are mixed after drying.

[0044] The high impermeability stabilizer is applied to solidify sandy soil, including the following steps:

[0045] (1) Take 35 parts of solid waste-based sulfur-aluminum-iron-based cementitious material, 30 parts of slag powder, 15 parts of ordinary portland cement, 5 parts of desulfurization gypsum, and 15 parts of silica fume, and perform grinding and premixing treatment, with a fineness requirement of less than 10% on a 200-mesh square hole sieve, to obtain a composite cementitious material;

[0046] (2) Dry the sandy soil, pass it through a 2mm sieve, and then add water to adjust the sandy soil to an optimal moisture content of 15%, mix uniformly, and then seal for 24 hours for standby;

[0047] (3) Respectively, the composite cementitious material and sulphoaluminate cement 52.5 in step (1) are mixed with mortar according to the water-cement ratio of 0.45, according to the national standard GB / T17671-2021 "Cement mortar strength test method (ISO method)", to prepare 40x40x160mm mortar samples and detect their compressive strength and flexural strength.

[0048] (4) The composite cementitious material in step (1) is 10 parts, and the wet soil in step (2) is 90 parts by mass, mixed and stirred, first slow stirring for 120s, and then fast stirring for 3 minutes, to make mixed soil material.

[0049] (5) According to 100% compaction degree, static pressure forming method is used to prepare 50mmx50mm cylindrical samples, which are placed in the curing room after demolding, standard curing (temperature 20±2℃, humidity≥95%) to 7d, 28d and 60d, to carry out unconfined compressive strength test of solidified soil. The preparation of test pieces and the determination of unconfined compressive strength are based on GB / T 50123-2019 "Standard for Soil Test Methods".

[0050] (6) According to 100% compaction degree, static pressure forming method is used to prepare 61.8mmx40mm cylindrical samples, which are placed in the curing room after demolding, standard curing (temperature 20±2℃, humidity≥95%) to 7d, 28d and 60d, to carry out solidified soil permeability test. The preparation of test pieces and the determination of impermeability are based on GB / T 50123-2019 "Standard for Soil Test Methods".

[0051] Table 1 Mechanical properties of solidifying agent

[0052]

[0053] Table 2 Unconfined compressive strength of solidified sandy soil

[0054]

[0055] Table 3 Impermeability of solidified sandy soil

[0056]

[0057] Example 2

[0058] A high impermeability solidifying agent for solidifying sandy soil, which is composed of the following components by mass fraction: solid waste-based sulphoaluminate cement 40 parts, slag powder 30 parts, ordinary Portland cement 15 parts, desulfurized gypsum 5 parts, silica fume 5 parts.

[0059] When it is applied to solidify sandy soil, the following steps are included:

[0060] (1) Take 40 parts of solid waste-based sulfur-aluminum-iron-based cementitious material, 30 parts of slag powder, 15 parts of ordinary portland cement, 10 parts of desulfurization gypsum, and 5 parts of silica fume, and perform grinding and premixing treatment. The fineness requirement is that the sieve residue of 200 mesh square hole sieve is less than 10%. The preparation method of the solid waste-based sulfur-aluminum-iron-based cementitious material is the same as that of Example 1.

[0061] (2) Dry the sandy soil, pass it through a 2mm sieve, and then add water to adjust the sandy soil to an optimal moisture content of 15%. After mixing evenly, seal for 24 hours for standby use.

[0062] (3) According to the national standard GB / T17671-2021 "Cement Mortar Strength Test Method (ISO Method)", the composite cementitious material and the sulphoaluminate cement 52.5 in step (1) are mixed with a water-cement ratio of 0.45 to prepare 40x40x160mm mortar samples and test their compressive strength and flexural strength.

[0063] (4) According to the mass, mix and stir 10 parts of the composite cementitious material in step (1) and 90 parts of the wet soil in step (2) at a slow speed for 120s and then at a high speed for 3 minutes to prepare the mixed soil material.

[0064] (5) According to 100% compaction, use static pressure molding to prepare 50mmx50mm cylindrical samples. After demolding, place them in a curing room for standard curing (temperature 20±2℃, humidity ≥95%) for 7d, 28d and 60d, and perform unconfined compressive strength test of solidified soil. The preparation of test pieces and the determination of unconfined compressive strength are based on GB / T 50123-2019 "Standard for Soil Test Methods".

[0065] (6) According to 100% compaction, use static pressure molding to prepare 61.8mmx40mm cylindrical samples. After demolding, place them in a curing room for standard curing (temperature 20±2℃, humidity ≥95%) for 7d, 28d and 60d, and perform permeability test of solidified soil. The preparation of test pieces and the determination of permeability performance are based on GB / T 50123-2019 "Standard for Soil Test Methods".

[0066] Table 4 Mechanical properties of solidified agent

[0067]

[0068] Table 5 Unconfined compressive strength of solidified sandy soil

[0069]

[0070] Table 6 Permeability performance of solidified sandy soil

[0071]

[0072] Example 3

[0073] A high impermeability curing agent for sand soil curing, which is composed of the following components in mass fraction: solid waste-based sulfur aluminum iron-based cementing material 30 parts, slag powder 30 parts, ordinary portland cement 15 parts, desulfurization gypsum 15 parts, silica fume 10 parts.

[0074] Its application to curing sandy soil includes the following steps:

[0075] (1) Take solid waste-based sulfur aluminum iron-based cementing material 30 parts, slag powder 30 parts, ordinary portland cement 15 parts, desulfurization gypsum 15 parts, and silica fume 10 parts, and perform grinding and premixing treatment, with fineness requirement meeting 200 mesh square hole sieve residue less than 10%; the preparation method of the solid waste-based sulfur aluminum iron-based cementing material is the same as that of Example 1;

[0076] (2) Dry the sandy soil, pass it through a 2mm sieve, then add water to adjust it to the optimum moisture content of the sandy soil (15%), mix it evenly, and then seal it for 24 hours for standby use;

[0077] (3) Compound cementing material and sulfur aluminate cement 52.5 in step (1) are mixed according to the water-cement ratio of 0.45, and mortar is prepared according to the national standard GB / T 17671-2021 "Cement mortar strength test method (ISO method)", and the compressive strength and flexural strength of the mortar sample are detected.

[0078] (4) Take 10 parts of compound cementing material in step (1) and 90 parts of wet soil in step (2) by mass, mix and stir, first slow stirring for 120 seconds, then fast stirring for 3 minutes, to make mixed soil material.

[0079] (5) According to 100% compaction degree, prepare 50mm×50mm cylindrical samples by static pressure molding, place them in the curing room after demolding, standard curing (temperature 20±2℃, humidity≥95%) for 7d, 28d and 60d, and conduct unconfined compressive strength test of cured soil. The preparation of test pieces and the determination of unconfined compressive strength are based on GB / T 50123-2019 "Standard for Soil Test Methods".

[0080] (6) According to 100% compaction degree, prepare 61.8mm×40mm cylindrical samples by static pressure molding, place them in the curing room after demolding, standard curing (temperature 20±2℃, humidity≥95%) for 7d, 28d and 60d, and conduct permeability test of cured soil. The preparation of test pieces and the determination of impermeability are based on GB / T 50123-2019 "Standard for Soil Test Methods".

[0081] Table 7 Mechanical properties of curing agent

[0082]

[0083] Table 8 Unconfined compressive strength of solidified sand

[0084]

[0085] Table 9 Impermeability of solidified sand

[0086]

[0087] Comparative Example 1

[0088] The difference from Example 1 is that:

[0089] (4) 10 parts of sulphoaluminate cement 52.5 and 90 parts of wet soil in step (2) were weighed by mass, mixed and stirred, first stirred slowly for 120 seconds, and then stirred quickly for 3 minutes to prepare a mixed soil material.

[0090] Table 10 Unconfined compressive strength of solidified sand

[0091]

[0092] Table 11 Impermeability of solidified sand

[0093]

[0094] Comparative Example 2

[0095] The difference from Example 1 is that: 35 parts of solid waste-based sulphoaluminate-ferrous cementing material were replaced by 35 parts of sulphoaluminate cement 52.5, and the others were the same as Example 1.

[0096] Table 12 Unconfined compressive strength of solidified sand

[0097]

[0098] Table 13 Impermeability of solidified sand

[0099]

[0100] Comparative Example 3

[0101] The difference from Example 1 is that: 15 parts of silica fume were replaced by 15 parts of slag powder, and the others were the same as Example 1.

[0102] Table 14 Unconfined compressive strength of solidified sand

[0103]

[0104] Table 15 Impermeability of solidified sand

[0105]

[0106] Comparative Example 4

[0107] The difference from Example 1 is that 15 parts of slag powder is replaced by 15 parts of silica fume, and the others are the same as Example 1.

[0108] Table 16 Unconfined compressive strength of cured sand

[0109]

[0110] Table 17 Permeability of cured sand

[0111]

[0112] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A high impermeability curing agent for sandy soil, characterized by: By weight, it consists of the following components: 30-50 parts of solid waste-based sulfur-aluminum-iron cementitious material; 10-30 parts of slag powder; 5-30 parts of ordinary silicate cement; 5-20 parts of desulfurized gypsum; and 1-10 parts of silica fume. The preparation method of solid waste-based sulfur-aluminum-iron cementitious material is as follows: 30-40 parts of desulfurized gypsum, 10-20 parts of red mud, 20-25 parts of aluminum ash, and 20-30 parts of carbide slag are mixed evenly. The mixed raw materials are added to a kiln and calcined for 20-40 minutes at a temperature of 1150-1300℃ to obtain clinker. 80 parts of clinker, 15 parts of desulfurized gypsum, and 5 parts of limestone powder are dried and then mixed together to prepare solid waste-based sulfur-aluminum-iron cementitious material.

2. The high impermeability curing agent for sandy soil according to claim 1, characterized by: By weight, it consists of the following components: 30-40 parts of solid waste-based sulfur-aluminum-iron cementitious material; 20-30 parts of slag powder; 10-30 parts of ordinary silicate cement; 5-20 parts of desulfurized gypsum; and 4-10 parts of silica fume.

3. The high impermeability curing agent for sandy soil according to claim 2, characterized by: By weight, it consists of the following components: 30-35 parts of solid waste-based sulfur-aluminum-iron cementitious material; 20-25 parts of slag powder; 15-20 parts of ordinary silicate cement; 15-20 parts of desulfurized gypsum; and 4-7 parts of silica fume.

4. The high impermeability stabilizer for sandy soil according to any one of claims 1 to 3, characterized in that: When preparing solid waste-based sulfur-aluminum-iron cementitious materials, the raw materials are 35-40 parts of desulfurized gypsum, 15-20 parts of red mud, 20-25 parts of aluminum ash, and 25-30 parts of carbide slag.

5. The high impermeability curing agent for sandy soil according to any one of claims 1 to 3, characterized by: When preparing solid waste-based sulfur-aluminum-iron cementitious materials, the raw materials are 36 parts of desulfurized gypsum, 16 parts of red mud, 22 parts of aluminum ash, and 26 parts of carbide slag.

6. The high impermeability curing agent for sandy soil according to any one of claims 1 to 3, characterized by: In the high impermeability solidifying agent for sandy soil, each component is ground to a fineness such that the residue on a 200-mesh square hole sieve is less than 10%.

7. The process for the preparation of a high impermeability consolidating agent for sandy soils according to any one of claims 1 to 6, characterized in that: Includes the following steps: Weigh the solid waste-based sulfur-aluminum-iron cementitious material, slag powder, ordinary silicate cement, desulfurized gypsum and silica fume in proportion, grind them until the residue on a 200-mesh square hole sieve is less than 10%, mix them, and you will get the product.

8. The method for preparing a high impermeability curing agent for sandy soil according to claim 7, characterized by: The method for modifying sandy soil using the high impermeability solidifying agent is as follows: adjust the moisture content of the sandy soil, mix the high impermeability solidifying agent and the sandy soil evenly at a mass ratio of 5-15:85-95 to obtain a mixed soil material; and prepare test specimens from the mixed soil material.

9. The method for preparing a high impermeability curing agent for sandy soil according to claim 8, characterized by: When modifying sandy soil, the moisture content of the sandy soil is 8%-20%.

10. The method for preparing a high impermeability curing agent for sandy soil according to claim 8, characterized by: The mass ratio of high impermeability solidifying agent to sandy soil is 7-12:87-92.

11. The method for preparing a high impermeability curing agent for sandy soil according to claim 10, characterized by: The mass ratio of the high impermeability solidifying agent to sandy soil is 10:90.

Images