Nano-material soil stabilizer for mucky soil

Abstract

The invention discloses a nanometer material soil stabilizer for mucky soil, which is prepared from the following components in percentage by mass: 47 to 59 percent of cement, 36 to 48 percent of slaked lime, 1.6 to 2.4 percent of nanometer silicon dioxide, 1.2 to 1.9 percent of nanometer aluminum oxide, 0.4 to 0.7 percent of sodium silicate and 0.4 to 0.9 percent of sodium sulfate. When the stabilizer is used for curing mucky soil, the first four powder and the liquid prepared from the second two components need to be combined, so that the dispersion uniformity of the stabilizer in the mucky soil can be effectively improved, the chemical excitation efficiency is improved, and the content of gelling substances generated by reaction is increased; the stabilizer has strong adaptability to mucky soil, and the stabilized soil prepared by mixing the stabilizer with the mucky soil has the characteristics of high strength and good water stability, and is suitable for engineering scenes such as road subgrade and base layer, foundation reinforcement, slope protection and the like.

Description

Technical Field

[0001] The present invention belongs to the field of soil stabilization, and particularly relates to a nano-material soil stabilizer for silty soil. Background Art

[0002] Currently, various engineering waste soils represented by silty soil

[0003] Recycling and comprehensive utilization have become a new industrialization direction. On the one hand, waste soils such as silty soil are currently mostly stacked in yards, generally with a high water content, polluting the environment and lacking an economically efficient disposal method. On the other hand, the mining of natural sand and gravel materials in engineering construction is increasingly strictly controlled, resulting in problems such as insufficient road construction materials in road engineering construction. Using soil stabilization technology to treat waste soils such as silty soil and then use them in engineering construction can not only solve the problem of insufficient engineering materials, but also intensively and economically utilize resources and protect the environment.

[0004] Due to the complex and variable composition of silty soil, high clay mineral content and fine particles, it usually has poor engineering properties such as high water content, high compressibility and low shear strength. Currently, the use of traditional soil curing / stabilizers for stabilization often has poor effects. A single traditional cementitious material, such as cement, lime, etc., mainly relies on gel phases such as calcium silicate hydrate and calcium aluminate hydrate to cement solid-phase particles in the soil and fill the pores between particles to improve the strength and water stability of the soil. However, due to the presence of a large amount of clay minerals, organic acids and other components in the soil, the reaction processes such as hydration, hardening, ion exchange, crystallization and carbonation of cement and lime are restricted. To meet the requirements of engineering applications, the method of increasing the dosage is often adopted, which not only has high costs and large carbon emissions, but also is prone to cracking, poor impermeability, slow early strength development, and general final strength and water stability after stabilization. Moreover, a single cementitious material has poor adaptability to silty soil with complex composition or high water content, often resulting in large variability in the stabilization effect.

[0005] Currently, existing multi-component curing / stabilizers are usually single powders or liquids. A single powder stabilizer often has poor dispersibility, and the dissolution-precipitation process of the powder brings about the evolution of the soil microstructure and pores, often resulting in the spatio-temporal variability of the macroscopic mechanical properties of the stabilized soil, causing uneven development of strength and water stability, etc.; and the early strength development is slower, the curing period is long, and it is prone to micro-damage such as cracking under the action of temporary construction loads and natural environmental conditions; the strength attenuation under the action of dry-wet cycles and freeze-thaw cycles is relatively fast, and the long-term water stability and durability are insufficient. A single liquid stabilizer mainly relies on principles such as ion exchange and surface modification to improve the water stability of the soil, but the bonding between the particles of the stabilized soil is weak and the macroscopic strength is low. At the same time, the existing stabilizers are not specifically developed for the characteristics of silty soil, and their applicability to silty soil is usually poor. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a nano-material soil stabilizer for silty soil, and the specific technical solution is as follows:

[0007] A nano-material soil stabilizer for silty soil, comprising the following components by mass percentage:

[0008] (1) Cement 47 - 59%;

[0009] (2) Slaked lime 36 - 48%;

[0010] (3) Nano-silica 1.6 - 2.4%;

[0011] (4) Nano-aluminum oxide 1.2 - 1.9%;

[0012] (5) Sodium silicate 0.4 - 0.7%;

[0013] (6) Sodium sulfate 0.4 - 0.9%.

[0014] Furthermore, it comprises the following components by mass percentage:

[0015] (1) Cement 59%;

[0016] (2) Slaked lime 36%;

[0017] (3) Nano-silica 2.3%;

[0018] (4) Nano-aluminum oxide 1.2%;

[0019] (5) Sodium silicate 0.6%;

[0020] (6) Sodium sulfate 0.9%.

[0021] Furthermore, the cement is P·O42.5 ordinary Portland cement, with the sulfur trioxide content not exceeding 3%, and the fineness of the cement meeting the requirement that the residue on an 80μm sieve ≤ 10%.

[0022] Furthermore, the effective calcium oxide content of the slaked lime ≥ 85%, and the fineness is less than 200 mesh.

[0023] Furthermore, the nano-silica is hydrophilic, with a particle size of 20 - 50nm and a specific surface area ≥ 200m 2 / g.

[0024] Furthermore, the nano-aluminum oxide is a γ-phase white powder, with a particle size of 10 - 20nm and a specific surface area ≥ 100m 2 / g.

[0025] Furthermore, the sodium silicate is solid crystalline, with a modulus of 2.0 - 3.3 and soluble in water.

[0026] Furthermore, the sodium sulfate is industrial grade anhydrous sodium sulfate with an effective content of ≥94%.

[0027] An application of a nano-material soil stabilizer in the stabilization treatment of silt soil includes the following steps:

[0028] Step 1: Pretreat the silt soil to obtain pretreated silt soil;

[0029] Step 2: Weigh the corresponding cement, slaked lime, nano-silica, and nano-aluminum oxide according to the amount of the pretreated silt soil, and stir to mix them evenly to obtain Powder A; Stir the prepared Powder A and the pretreated silt soil in proportion to mix them evenly to form a dry mixture;

[0030] Step 3: Weigh the corresponding sodium silicate and solid sodium sulfate according to the amount of the pretreated silt soil, and weigh the corresponding mass of water according to the optimal moisture content obtained from the standard Proctor compaction test of the soil to be stabilized. Add the weighed sodium silicate and sodium sulfate and stir until the sodium silicate and sodium sulfate solids are completely dissolved to obtain Liquid B; Then inject Liquid B into the dry mixture and continue to stir to mix them evenly to form a wet mixture;

[0031] Step 4: Transport the wet mixture to the construction site, and through paving, shaping, rolling, and curing, form a structural layer with high strength and good water stability.

[0032] Furthermore, the dosage of the soil stabilizer is 6% - 15% of the pretreated silt soil in Step 2.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. When the stabilizer of the present invention is used, Powder A ensures the uniformity of its full mixing with the solid-phase particles of the soil on the premise of not being invalidated due to chemical reactions through dry mixing. Liquid B ensures the dispersion of sulfate ions and silicate ions in the solution by pre-dissolving the active ingredients, accelerating the subsequent reaction process, and improving the early strength and water stability of the stabilized soil. Moreover, Powder A and Liquid B are mixed in sequence, reducing the probability of the active ingredients of the stabilizer being invalidated due to moisture absorption.

[0035] 2. The stabilizer of the present invention contains nano-silica and nano-aluminum oxide, increasing the content of the gel substances generated by the reaction and improving the water stability and long-term durability of the stabilized soil under freeze-thaw cycles and wet-dry cycles. At the same time, the introduced aluminum oxide can react with sulfate ions to adjust the structure of calcium sulfoaluminate hydrate in the cement reaction products, reducing the expansibility of the stabilizer reaction products, minimizing the micro-damage caused by the micro-expansion effect during the strength development process, and improving the strength and water stability of the stabilized soil.

[0036] 3. The stabilizer of the present invention uses an aqueous solution of sodium sulfate and sodium silicate as an alkaline activator. On the one hand, it improves the uniformity of the dispersion of sulfate and silicate ions, increases the content of cementitious substances. On the other hand, it improves the efficiency of alkali activation, ensures the normal reaction process of cement and lime, promotes the dissolution of active silicon and aluminum components, and enhances the stabilization effect.

[0037] 4. The stabilizer of the present invention has strong adaptability to silty soil and good stabilization effect. When using the stabilizer of the present invention to stabilize silty soil, due to the relatively high alkalinity of the water film during the reaction process and the sufficient content of exogenous calcium ions, it can overcome the problems of slow strength development, low ultimate strength, and poor water stability of stabilized soil caused by the consumption of calcium ions and hydroxide ions by substances such as clay minerals and organic acids rich in silty soil, ensuring the stabilization effect.

[0038] 5. The dosage of nanomaterials in the stabilizer of the present invention is relatively low, and the cost is controllable; the raw materials used are all common materials in the process of engineering construction, and the raw materials are easy to obtain and the cost is low, with high economic benefits. Specific Embodiments

[0039] The present invention will be described in detail below according to preferred embodiments, and the purpose and effect of the present invention will become more clear. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] The nano-material soil stabilizer for silty soil of the present invention, when used for stabilizing silty soil, mixes two cementitious materials, namely cement and slaked lime, and two nano-material additives, namely nano-silica and nano-aluminum oxide, into the silty soil by dry mixing, ensuring the spatio-temporal uniformity of subsequent reactions. At the same time, due to less water in the dry mix, the dry mix will not cause the failure of the stabilizer components due to the reaction during the mixing process. Subsequently, two activators, namely sodium silicate and sodium sulfate, are dissolved in water to form an aqueous solution, enhancing the dispersion of sulfate and silicate radicals. After injecting this aqueous solution into the dry mix and mixing evenly, the cement, lime, nano-silica, nano-aluminum oxide in the stabilizer and the active components in the silty soil react with the connected water film as the reaction medium. Cement hydrates to form gel phases such as C-S-H and C-A-H to cement soil particles, and at the same time releases calcium hydroxide. The calcium hydroxide generated by cement hydration and the calcium hydroxide in slaked lime form calcium sulfate and calcium silicate solids with sulfate and carbonate radicals in the aqueous solution, cementing soil particles and increasing the content of hydroxide radicals in the aqueous solution, that is, increasing the alkalinity of the aqueous solution. On the one hand, this promotes the hydration and hardening of cement, and on the other hand, it also ensures the dissolution of active components such as nano-silica, nano-aluminum oxide and clay minerals in the soil, promoting the formation of cementitious geopolymers. Slaked lime, on the one hand, replenishes the calcium ions reduced due to adsorption caused by ion exchange in the soil double electric layer, ensuring the formation amount of gel phases such as C-S-H and C-A-H, and on the other hand, it also provides a highly alkaline environment through the reaction with sulfate and carbonate radicals, overcoming the problem of reducing the solution alkalinity due to the reaction of organic acids in silty soil with hydroxide radicals, ensuring the normal reaction process of cement hydration and hardening. Nano-silica and nano-aluminum oxide increase the content of gelling substances in an alkaline environment. At the same time, due to the small particle size and huge specific surface area of nano-silica and nano-aluminum oxide, they can fill pores, improving the impermeability of the stabilized soil. In addition, the uniformly distributed nano-materials can act as crystallization nuclei, improving the water stability and long-term durability of the stabilized soil under freeze-thaw cycles and wet-dry cycles. At the same time, nano-aluminum oxide and sulfate radicals can adjust the structure of calcium sulfoaluminate hydrate in the cement reaction products, reducing the expansibility of the stabilizer reaction products, reducing the micro-damage caused by the micro-expansion effect during the strength development process, and improving the strength and water stability of the stabilized soil.

[0041] Example 1

[0042] In this example, the silty soil used was taken from a road construction site in a certain place in Zhejiang Province. Through indoor tests, the plasticity index was measured to be 18, the natural moisture content was 54%, and the compression coefficient α 1-2 = 0.7 MPa -1 , and the maximum dry density was 1.81 g / cm 3, the optimal moisture content is 14.36%. First, remove the sundries such as turf, tree roots, stones, plastics, etc. in the soft soil to be stabilized, and then reduce its moisture content by turning, drying, and baking (the measured moisture content of the dried soil sample is 7%); then use machinery to crush it until the maximum particle size of the soil mass is not greater than 4.75 mm, and the nominal maximum particle size is not greater than 2.36 mm; the pretreated soil sample is put into a plastic bucket, covered, and stored for later use.

[0043] The stabilizer in this example includes the following components by mass percentage: cement 59%; slaked lime 36%; nano-silica 2.3%; nano-aluminum oxide 1.2%; sodium silicate 0.6%; sodium sulfate 0.9%; the dosage is 8.4% of the dry soil weight.

[0044] The preparation process of the stabilizer in this example is as follows: Put the weighed cement, slaked lime, nano-silica, and nano-aluminum oxide into a forced dry powder stirrer, and stir forcibly at a rate of 60 - 120 revolutions per minute for 5 minutes to obtain powder A; weigh the sodium silicate and sodium sulfate, weigh the corresponding mass of water according to the optimal moisture content obtained from the indoor standard compaction test of the soil to be stabilized, pour it into a container, put a magnetic rotor, and stir at a rate of 300 - 500 revolutions per minute until the sodium silicate and sodium sulfate solids are completely dissolved to obtain liquid B.

[0045] The application steps of the stabilizer in this example are as follows: Stir the prepared powder A and the pretreated soft soil in proportion to make them evenly mixed to form a dry mixture; then inject liquid B into the dry mixture and continue to stir to make them evenly mixed to form a wet mixture; the obtained mixture is formed and cured according to the "Test Regulations for Inorganic Bound Material Stabilized Materials in Highway Engineering" (JTG 3441—2024).

[0046] Example 2

[0047] In this example, the soft soil used is the same as that in Example 1.

[0048] The stabilizer in this example includes the following components by mass percentage: cement 48%; slaked lime 48%; nano-silica 1.6%; nano-aluminum oxide 1.6%; sodium silicate 0.4%; sodium sulfate 0.4%; the dosage is 6.3% of the dry soil weight.

[0049] The preparation process of the stabilizer in this example is the same as that in Example 1.

[0050] The application steps of the stabilizer in this example are the same as those in Example 1.

[0051] Example 3

[0052] In this example, the soft soil used is the same as that in Example 1.

[0053] The stabilizer in this embodiment includes the following components by mass percentage: cement 47.4%; slaked lime 47.4%; nano-silica 1.9%; nano-aluminum oxide 1.9%; sodium silicate 0.7%; sodium sulfate 0.7%; the dosage is 10.5% of the dry soil weight.

[0054] The preparation process of the stabilizer in this embodiment is the same as that in Example 1.

[0055] The application steps of the stabilizer in this embodiment are the same as those in Example 1.

[0056] Using the A powder and B liquid agent obtained in Examples 1 to 3 of the present invention to stabilize typical silty soil, the 7-day unconfined compressive strength and water stability coefficient are obtained, as shown in Table 1.

[0057] For comparison of the stabilization effect, the 7-day unconfined compressive strength and water stability coefficient of the same silty soil stabilized with 8.4% single cement and 5% cement + 3.4% lime double admixture were also tested. See Table 1 for details.

[0058] By comparing the data in Table 1, it is found that compared with the traditional single cement admixture and the combined cement + lime stabilized soil, at the same admixture level (8.4%), the 7-day unconfined compressive strength of the silty soil stabilized by the embodiments of the present invention is increased by 2 to 2.5 times, and the water stability coefficient is increased by 10% to 16%; even at a lower admixture level (6.3%), the strength and water stability coefficient of the silty soil stabilized by the present invention are still higher than those of the single cement admixture and the combined cement and lime stabilized soil. The results show that the silty soil stabilized by the nano-material stabilizer of the present invention has good strength and water stability.

[0059] Table 1 7-day unconfined compressive strength and water stability coefficient of different examples

[0060] Example Unconfined compressive strength (MPa) of 7d Coefficient of water stability (%) Example 1 2.5 85 Example 2 1.8 80 Example 3 2.2 81 8.4% cement 1.0 73 5% cement + 3.4% lime 1.2 77

[0061] Those of ordinary skill in the art can understand that the above are only preferred examples of the invention and are not used to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, for those skilled in the art, they can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, etc. made within the spirit and principle of the invention shall be included within the protection scope of the invention.

Claims

1. A nano-material soil stabilizer for silty soil, characterized in that, It comprises the following components by mass percentage: (1) 47 - 59% of cement; (2) 36 - 48% of slaked lime; (3) 1.6 - 2.4% of nano-silica; (4) 1.2 - 1.9% of nano-aluminum oxide; (5) 0.4 - 0.7% of sodium silicate; (6) 0.4 - 0.9% of sodium sulfate.

2. The nano-material soil stabilizer for silty soil according to claim 1, characterized in that (7) It comprises the following components by mass percentage: (1) 59% of cement; (2) 36% of slaked lime; (3) 2.3% of nano-silica; (4) 1.2% of nano-aluminum oxide; (5) 0.6% of sodium silicate; (6) 0.9% of sodium sulfate.

3. The nano-material soil stabilizer for silty soil according to claim 1 or 2, characterized in that, The cement is P·O 42.5 ordinary Portland cement, in which the content of sulfur trioxide shall not exceed 3%, and the fineness of the cement shall meet the requirement that the residue on 80μm sieve ≤ 10%.

4. The nano-material soil stabilizer for silty soil according to claim 1 or 2, characterized in that, The effective calcium oxide content of the slaked lime ≥ 85%, and the fineness is less than 200 mesh.

5. The nano-material soil stabilizer for silt soil according to claim 1 or 2, characterized in that, The nano-silica is hydrophilic, with a particle size of 20 to 50 nm and a specific surface area of ≥ 200 m 2 / g.

6. The nano-material soil stabilizer for silty soil according to claim 1 or 2, characterized in that, The nano-aluminum trioxide is a γ-phase white powder with a particle size of 10-20 nm and a specific surface area of ≥ 100 m 2 / g.

7. The nano-material soil stabilizer for silty soil according to claim 1 or 2, characterized in that, The sodium silicate is solid crystal, with a modulus of 2.0 - 3.3 and soluble in water.

8. The nano-material soil stabilizer for silty soil according to claim 1 or 2, characterized in that The sodium sulfate is industrial grade anhydrous sodium sulfate, with an effective content ≥ 94%.

9. Use of a nano-material soil stabilizer prepared as claimed in claim 8 in the stabilization treatment of silt soil, characterized in that, It includes the following steps: Step 1: Pretreat the silty soil to obtain the pretreated silty soil; Step 2: Weigh the corresponding cement, slaked lime, nano-silica, and nano-aluminum oxide according to the amount of the pretreated silty soil, stir to mix them evenly to obtain powder A; stir the prepared powder A and the pretreated silty soil in proportion to mix them evenly to form a dry mixture; Step 3: Weigh the corresponding sodium silicate and sodium sulfate solids according to the amount of the pretreated silty soil, weigh the corresponding mass of water according to the optimum moisture content obtained from the indoor standard compaction test of the silty soil to be stabilized, add the weighed sodium silicate and sodium sulfate into it and stir until the sodium silicate and sodium sulfate solids are completely dissolved to obtain liquid B; then inject liquid B into the dry mixture and continue to stir to mix them evenly to form a wet mixture; Step 4: Transport the wet mixture to the construction site, and through paving, shaping, rolling and curing, form a structural layer with high strength and good water stability.

10. The application according to claim 9, characterized in that, The dosage of the soil stabilizer is 6% - 15% of the pretreated silty soil in Step 2.