A preparation method of solidified loess suitable for high-grade highway base construction

Abstract

The application provides a preparation method of solidified loess suitable for high-grade highway base construction, and relates to the technical field of loess solidification, and comprises the following steps: uniformly mixing cement, lime and loess to obtain a mixture 1; adding citric acid into distilled water, stirring and dissolving, then adding calcium lignosulfonate, calcium chloride and aluminum chloride, and uniformly mixing to obtain a solidification liquid A; mixing the solidification liquid A with the mixture 1 to obtain a mixture 2; mixing sodium silicate with distilled water, dissolving, then adding polyacrylamide, sodium chloride and potassium chloride, and uniformly mixing to obtain a solidification liquid B; mixing the solidification liquid B with the mixture 2, and adding water to obtain a mixture 3; and compacting the mixture 3 to obtain the solidified loess. The solidified loess has high early compressive strength, strong late strength growth capacity, is not prone to cracking during use, and has low lime and cement consumption.

Description

Technical Field

[0001] This invention relates to the field of loess solidification technology, specifically to a method for preparing solidified loess suitable for the construction of high-grade highway base courses. Background Technology

[0002] The consumption of natural resources for global construction and transportation infrastructure has surged, with sand and gravel becoming the most consumed material due to their irreplaceable nature. However, long-term over-exploitation has led to a severe shortage of sand and gravel resources, and the extraction process also poses risks such as landslides and soil erosion. Even more serious is the fact that the production of traditional cementitious materials (such as lime and cement) not only accelerates the depletion of sand and gravel resources but also generates large amounts of dust during use, causing environmental pollution.

[0003] Solidified soil is a composite material with improved engineering properties obtained by modifying soil through various physicochemical reactions using soil solidification technology. Soil solidification technology can transform ordinary soil into high-strength, water-stable road construction materials. Its core principle lies in reconstructing the soil particle structure and enhancing the cohesion between particles. Using solidified soil in engineering construction not only reduces the use of traditional cementing materials such as lime and cement, but also transforms widely distributed natural soil or engineering waste soil into stable building materials. This alleviates the pressure of sand and gravel resource shortages and enables the resource utilization of waste. While numerous solidification technologies exist for different soil types, research on loess solidification is relatively limited. Loess, as a typical regional soil, although widely distributed and abundant, suffers from weak mechanical properties due to its unique metastable porous structure, making it prone to subsidence and cracking in its natural state. While traditional silicate-based materials (such as lime and cement) can partially improve loess properties, their shrinkage can easily lead to cracking. Furthermore, the production process is energy-intensive and generates significant carbon emissions. Excessive use of these materials can also negatively impact plant growth and the ecological environment, failing to meet the demands of green and low-carbon development. Meanwhile, current soil solidification research largely focuses on expansive soils and silt, leaving a significant gap in the development of specialized solidification methods for loess's collapsibility and functional defects. Although existing soil solidification methods can generally improve soil strength, they often suffer from limited performance, poor adaptability, long solidification times, and uneven strength development (inflated early strength, slow later strength growth, or insufficient strength throughout). These shortcomings limit the use of most existing solidified loess methods to rural and urban roads—strumental layers with lower strength requirements—and prevent their application as structural materials for high-grade highways.

[0004] It is evident that the solidified loess in the existing technology has low early compressive strength, limited ability to increase strength in the later stage, weak resistance to freeze-thaw cycles and water erosion, is prone to frost heave and cracking, and has poor durability. Summary of the Invention

[0005] This invention provides a method for preparing solidified loess suitable for the construction of high-grade highway base courses, in order to solve the technical problems of low early-stage compressive strength, limited later-stage strength growth, and easy cracking of solidified loess in the prior art.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing solidified loess suitable for the construction of high-grade highway base courses, comprising the following steps:

[0007] S1. Mix 4-5 parts cement, 4-5 parts lime and 90-92 parts loess evenly by weight to obtain mixture 1;

[0008] S2. Add citric acid to distilled water, stir to dissolve, then add calcium lignosulfonate, calcium chloride and aluminum chloride, mix well to obtain curing solution A;

[0009] S3. Mix the curing liquid A with the mixture 1 to obtain the mixture 2;

[0010] S4. Mix sodium silicate with distilled water, dissolve it, then add polyacrylamide, sodium chloride and potassium chloride, mix evenly to obtain curing solution B;

[0011] S5. Mix the curing liquid B with the mixture 2, add water and stir evenly to obtain the mixture 3, wherein the moisture content of the mixture 3 is 17.2%-18.6%;

[0012] S6. The mixture 3 is compacted to a compaction degree of greater than or equal to 95% to obtain solidified loess.

[0013] Preferably, the mass ratio of citric acid to distilled water in S2 is 1:10-20.

[0014] Preferably, in S2, the citric acid is 0.014 to 0.033 parts by mass, the calcium lignosulfonate is 0.044 to 0.063 parts, the calcium chloride is 0.014 to 0.024 parts, and the aluminum chloride is 0.01 to 0.021 parts by mass.

[0015] Preferably, the pH value of the curing liquid A in S2 is 3.7~5.6.

[0016] Preferably, the mass ratio of sodium silicate to distilled water in S4 is 1:15-20.

[0017] Preferably, the dissolution temperature in S4 is 50~60℃.

[0018] Preferably, the sodium silicate in S4 is 0.052-0.081 parts by mass, the polyacrylamide is 0.02-0.03 parts, the sodium chloride is 0.018-0.027 parts, and the potassium chloride is 0.012-0.021 parts.

[0019] Preferably, by weight, S1 contains 4 parts cement, 4 parts lime, and 92 parts loess; S2 contains 0.014 parts citric acid, 0.046 parts calcium lignosulfonate, 0.02 parts calcium chloride, and 0.01 parts aluminum chloride; and S4 contains 0.052 parts sodium silicate, 0.021 parts polyacrylamide, 0.021 parts sodium chloride, and 0.016 parts potassium chloride.

[0020] Preferably, the pH of the curing liquid B in S4 is 10.3~11.7.

[0021] In this invention, the solidified loess undergoes a solidification process where cement and lime first react with water to generate calcium silicate hydrate (CSH) gel and ettringite, forming a basic cementitious framework. Simultaneously, calcium chloride in the solidification liquid A accelerates cement hydration, and aluminum chloride promotes the early formation of ettringite crystals. These hydration products rapidly fill the large pores of the soil, collectively constructing a high-density, rigid early-stage framework for the solidified soil. During this process, calcium lignosulfonate in solidification liquid A not only provides calcium ions to promote hydration but also adsorbs onto the surface of loess particles, forming a hydrophobic film that coats clay minerals such as illite and montmorillonite, thereby preventing water intrusion and inhibiting loess collapse. Citric acid in the solidification liquid temporarily locks in Al in the system. 3+ and Ca 2+ To avoid deactivation of the curing solution due to component hydrolysis under excessively high pH conditions, thus preventing Al 3+ and Ca 2+ It can fully participate in the curing reaction, achieving precise targeting of early-strength components.

[0022] Sodium silicate in curing solution B first hydrolyzes into silicate ions, generating silica gel. After adding curing solution B, this silica gel continues to fill the pores of the soil and forms a dense cementitious film on the particle surface, further enhancing the soil's strength. Some silicate ions also directly participate in the hydration reaction, activating the active silica-alumina components within the loess. These components undergo a continuous pozzolanic reaction with calcium hydroxide produced during cement hydration, generating secondary CSH gel, which gradually seals the micropores, achieving sustained strength growth in the later stages. Simultaneously, polyacrylamide (PAM) in curing solution B, with its high viscosity and adsorption bridging effect, forms a flexible polymer network between soil particles and hydration products, creating a spatially interpenetrating structure of "rigid gel skeleton + flexible polymer network." This inhibits the expansion of microcracks in the soil, ultimately forming a dense, honeycomb-like whole. The microporous structure of the soil is further improved, achieving the solidification and enhancement of the loess. This densely interwoven three-dimensional honeycomb mesh structure can resist compressive stress (inorganic phase dominant) and buffer tensile stress caused by shrinkage or load (organic phase dominant), significantly improving the material's toughness and long-term stability.

[0023] Simultaneously, multiple electrolytes (calcium chloride, aluminum chloride, sodium chloride, potassium chloride) produce a synergistic ionic effect: high-valence cations (Ca... 2+ Al 3+ Compression of the double electric layer of clay particles promotes flocculation and aggregation; monovalent ions (Na+) + K + This process maintains an alkaline environment and stabilizes the hydrolysis of sodium silicate. This significantly reduces the porosity of the soil. Combined with a high-pressure compaction process of over 95%, it ultimately forms a dense, uniform, and finely textured reinforced body, completely solving the problem of imbalance between early and later strength development in traditional solidified soils.

[0024] Furthermore, the loess prepared by the method of this invention can achieve a cross-scale synergistic effect during the solidification process. Solidifying liquid A, in addition to promoting the hydration reaction of cement, can also reduce the surface potential of loess particles, compress their surface double layer, and promote tighter bonding between particles. Solidifying liquid A mainly improves the pore structure of soil particles at the microscopic level. Solidifying liquid B has strong cohesive properties, enabling dispersed particles to aggregate and link together to form a dense whole. Solidifying liquid B mainly improves the spatial distribution of soil particles at the macroscopic level. The evolution process of the microstructure of the solidified soil confirms the synergistic strengthening effect of components A and B in loess solidification. The early addition of solidifying liquid A creates conditions for the further coagulation of loess particles by solidifying liquid B. Electret (curing solution A) rapidly forms and grows, filling large pores in the soil and forming a rigid framework, laying the foundation for early strength. Secondary CSH gel (generated by the reaction of SiO2 and Al2O3 in loess, activated by sodium silicate in curing solution B, with Ca(OH)2 in the system) continuously fills mesopores. The PAM polymer network, with its long-chain molecules, forms "organic bridges" across microcracks and interweaves with the inorganic gel to form an interpenetrating network. The inorganic phase provides rigid support, while the organic phase enhances toughness. The interface between the two is formed by Ca... 2+ The ionic bonding with PAM creates a tight connection, ultimately achieving the overall rigid-flexible composite properties.

[0025] The technical solution of the present invention has at least the following beneficial effects compared with the prior art:

[0026] In this invention, cement and lime serve as the primary cementing materials, forming the basic framework of ettringite and CSH gel. Sodium silicate acts as an activator, participating in early hydration reactions to generate cementitious products and continuously activating active SiO2 and Al2O3 in loess to form secondary gels. These three components constitute a three-tiered cementing system of "foundation-activation-replenishment," ensuring the continuity and stability of the strength development of the solidified soil.

[0027] Calcium chloride accelerates cement hydration and provides early strength, aluminum chloride supplements the formation of ettringite, while citric acid selectively inhibits the formation of calcium chloride.2+ Al 3+ Hydrolysis enables precise targeting of early-strength components. These three elements form a synergistic relationship of "acceleration-reinforcement-regulation," which not only solves the problem of insufficient early strength in solidified soil but also reserves key components for later reactions.

[0028] Polyacrylamide forms an interpenetrating network structure with inorganic gels through molecular chain bridging and ionic bonding; while the mixed electrolyte (Ca... 2+ / Al 3+ / Na + / K + By regulating the interfacial electrical properties of the particles and the chemical environment of the solution, the reaction process is optimized. These two types of components work together to achieve multi-scale reinforcement of the microstructure of the solidified soil, from nanoscale molecular bonding to macroscale particle arrangement.

[0029] The solidified loess of this invention possesses both high early-stage strength and good later-stage strength, solving the problem of uneven strength development in existing solidified loess. The method for preparing solidified loess suitable for high-grade highway base course construction in this invention, through optimizing material formulation, proportioning, and solidification process, significantly improves the strength and road performance of traditional lime-cement solidified loess while effectively reducing the amount of traditional cementitious materials used, thus combining excellent engineering performance and environmental characteristics. The mechanical and road performance properties of the solidified loess of this invention can meet the base course construction requirements of high-grade highways and Class I highways with medium and light traffic levels, as well as Class II and lower-level highways with heavy traffic levels. Attached Figure Description

[0030] Figure 1 This is a photograph of the curing liquid A in Example 1;

[0031] Figure 2 This is a photograph of the curing liquid B in Example 1;

[0032] Figure 3 This is a photograph of the solidified loess from Example 1. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] The polyacrylamide is a non-ionic polyacrylamide produced by Shanghai Maclean Biochemical Technology Co., Ltd., with a molecular weight of 12 million.

[0035] The cement is PO42.5 cement produced by China National Building Materials Co., Ltd.

[0036] The lime is Grade A lime produced by China National Building Materials Co., Ltd.

[0037] Sodium silicate has a modulus of 2;

[0038] The loess used in the experiment was taken from Wanrong County, Shanxi Province.

[0039] The method for solidifying loess is standard curing, which involves curing in a standard curing box under conditions of relative humidity ≥90% and temperature 20℃±2℃.

[0040] The unconfined compressive strength test method for solidified loess was conducted according to the relevant standards of JTG 3441-2024 "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering". When testing solidified loess specimens, the specimens, which had been soaked in water for 24 hours, were first removed, and excess water was gently removed from their surface with a soft cloth. Then, the specimens were placed between the indenters of the compressive strength testing instrument, and the loading rate was set to 1 mm / min. During the test, axial pressure was gradually applied until the specimen fractured, and the corresponding pressure value was recorded.

[0041] Example 1

[0042] This embodiment provides a method for preparing solidified loess suitable for the construction of high-grade highway base courses, including the following steps:

[0043] S1. Mix 50g of cement, 50g of lime and 900g of loess evenly to obtain mixture 1;

[0044] S2. Weigh 0.33g citric acid, 0.63g calcium lignosulfonate, 0.24g calcium chloride, and 0.21g aluminum chloride. First, add the citric acid to 4.95ml of water and stir at 150RPM for 5 minutes. Then add the calcium lignosulfonate, aluminum chloride, and calcium chloride and continue stirring for 10 minutes to obtain curing solution A. The pH value of curing solution A is 3.7. Its physical image is shown below. Figure 1 Mix all of the curing liquid A with mixture 1, stir evenly, and let stand for 15 minutes to obtain mixture 2;

[0045] S3. Weigh 0.81g of sodium silicate, 0.30g of polyacrylamide, 0.27g of sodium chloride, and 0.21g of potassium chloride. First, add the sodium silicate to 14.5ml of water at 60℃ and stir at a constant speed of 150RPM for 5 minutes. Then add the polyacrylamide, sodium chloride, and potassium chloride, and continue stirring for 50 minutes to obtain curing solution B. The pH of curing solution B is 11.4. Its physical image is shown below. Figure 2 ;

[0046] S4. Mix all of the curing liquid B with all of the mixture 2, add water and stir evenly to obtain mixture 3, wherein the moisture content of mixture 3 is 18.6%;

[0047] S5. Prepare solidified loess by compacting mixture 3 with a compaction degree of 95%. Its physical image is shown below. Figure 3 .

[0048] In this embodiment, the unconfined compressive strength of the solidified loess after 7 days of curing was 3.08 MPa, and the unconfined compressive strength after 28 days of curing was 5.18 MPa; no cracking occurred during the curing process of the solidified loess.

[0049] Example 2

[0050] This embodiment provides a method for preparing solidified loess suitable for the construction of high-grade highway base courses, including the following steps:

[0051] S1. Mix 45g of cement, 45g of lime and 910g of loess evenly to obtain mixture 1;

[0052] S2. Weigh 0.2g citric acid, 0.44g calcium lignosulfonate, 0.14g calcium chloride, and 0.16g aluminum chloride. First, add citric acid to 4ml of water and stir at 150RPM for 5min. Then add calcium lignosulfonate, aluminum chloride, and calcium chloride and continue stirring for 10min to obtain curing solution A. The pH of curing solution A is 4.4. Mix all of curing solution A with mixture 1, stir evenly, and let stand for 15min to obtain mixture 2.

[0053] S3. Weigh 0.56g of sodium silicate, 0.20g of polyacrylamide, 0.18g of sodium chloride, and 0.12g of potassium chloride. First, add sodium silicate to 11.2ml of water at 55℃ and stir at a constant speed of 150RPM for 5min. Then add polyacrylamide, sodium chloride, and potassium chloride, and continue stirring for 50min to obtain curing solution B. The pH of curing solution B is 11.7. S4. Mix all of curing solution B with all of mixture 2, add water and stir for 10min to obtain mixture 3. The water content of mixture 3 is 17.2%.

[0054] S5. Prepare solidified loess by compacting the mixture 3 with a compaction degree of 95%.

[0055] In this embodiment, the unconfined compressive strength of the solidified loess after 7 days of curing was 2.86 MPa, and the unconfined compressive strength after 28 days of curing was 4.61 MPa; no cracking occurred during the curing process of the solidified loess.

[0056] Example 3

[0057] This embodiment provides a method for preparing solidified loess suitable for the construction of high-grade highway base courses, including the following steps:

[0058] S1. Mix 40g of cement, 40g of lime and 920g of loess evenly to obtain mixture 1;

[0059] S2. Weigh 0.14g citric acid, 0.46g calcium lignosulfonate, 0.20g calcium chloride, and 0.10g aluminum chloride. First, add citric acid to 1.4ml of water and stir at 150RPM for 5min. Then add calcium lignosulfonate, aluminum chloride, and calcium chloride and continue stirring for 10min to obtain curing solution A. The pH of curing solution A is 5.6. Mix all of curing solution A with mixture 1, stir evenly, and let stand for 15min to obtain mixture 2.

[0060] S3. Weigh 0.52g of sodium silicate, 0.21g of polyacrylamide, 0.21g of sodium chloride, and 0.16g of potassium chloride. First, add sodium silicate to 7.8ml of water at 50℃ and stir at 150RPM for 5min. Then add polyacrylamide, sodium chloride, and potassium chloride and continue stirring for 40min to obtain curing solution B. The pH of curing solution B is 10.3.

[0061] S4. Mix all of the curing liquid B with all of the mixture 2, add water and stir for 10 minutes to obtain mixture 3, wherein the moisture content of mixture 3 is 17.8%;

[0062] S5. Solidified loess was prepared by compacting the mixture 3 with a compaction degree of 95%.

[0063] In this embodiment, the unconfined compressive strength of the solidified loess after 7 days of curing is 2.83 MPa, and the unconfined compressive strength after 28 days of curing can reach 4.57 MPa; no cracking occurs during the curing process of the solidified loess.

[0064] Comparative Example 1

[0065] A mixture of 40g cement, 40g lime, 164g water, and 920g loess was prepared. The mixture was then compacted to a compaction degree of 95% to prepare solidified soil. The unconfined compressive strength of the solidified soil after 7 days of curing under standard conditions was 1.82MPa, and the unconfined compressive strength after 28 days of curing was 3.24MPa. The solidified soil exhibited good appearance during the curing process.

[0066] Comparative Example 2

[0067] The method in this comparative example is similar to that in Example 3, except that the amount of sodium silicate in S3 in this comparative example is 0.36 g. The unconfined compressive strength of the solidified loess in this comparative example is 2.09 MPa after seven days of curing and 3.41 MPa after 28 days of curing.

[0068] Comparative Example 3

[0069] The method in this comparative example is similar to that in Example 3, except that the amount of sodium silicate in S3 in this comparative example is 1.1 g. The unconfined compressive strength of the solidified loess in this comparative example is 2.41 MPa after seven days of curing and 3.83 MPa after 28 days of curing.

[0070] Comparative Example 4

[0071] This comparative example uses a method similar to that in Example 3, except that the amount of calcium chloride in S2 is 0.1 g. The solidified loess in this comparative example has an unconfined compressive strength of 2.38 MPa after seven days of curing and 3.97 MPa after 28 days of curing.

[0072] Comparative Example 5

[0073] This comparative example uses a method similar to that in Example 3, except that the amount of calcium chloride in S2 is adjusted to 0.4 g. The solidified loess in this comparative example has an unconfined compressive strength of 2.62 MPa after seven days of curing and 4.05 MPa after 28 days of curing.

[0074] Comparative Example 6

[0075] This comparative example is similar to the method in Example 3, except that in this comparative example, sodium chloride and potassium chloride in S2 are replaced with polyacrylamide in equal amounts. The solidified loess in this comparative example has an unconfined compressive strength of 2.41 MPa after seven days of curing and an unconfined compressive strength of 3.72 MPa after 28 days of curing.

[0076] Comparing Examples 1, 2, and 3 with Comparative Example 1, it was found that the curing liquid can effectively improve the early and long-term compressive strength of the cured soil.

[0077] Comparing the test results in Example 3 with those in Comparative Examples 2 and 3, it can be seen that both excessively high and low sodium silicate dosages reduce the early and long-term strength of the solidified soil. This is because too little sodium silicate leads to a reduction in the hydrolysis product silicate ions, thus decreasing its promoting effect on cement hydration. Simultaneously, too little sodium silicate also reduces its activation effect on the active silica-alumina components in the loess, thereby hindering further reactions between the loess and the hydration products. Conversely, excessive sodium silicate leads to an excess of silicate ions, resulting in a loosely structured, low-strength gel network rather than a dense, high-strength gel (such as CSH gel).

[0078] The test results in Comparative Examples 3, 4, and 5 show that both excessively high and low calcium chloride dosages will reduce the early and long-term strength of the solidified soil. When the calcium chloride dosage is too low, there will be insufficient calcium ions, which will weaken the promoting effect of calcium chloride hydration reaction. At the same time, the ion exchange between calcium ions and the loess surface will also be weakened. When the calcium chloride dosage is too high, it will lead to loess salinization and affect the strength of the solidified soil.

[0079] The test results in Comparative Examples 3 and 6 show that replacing potassium chloride and sodium chloride with equal amounts of polyacrylamide reduces both the early and long-term compressive strength of the solidified soil. This is because polyacrylamide, as a polymer, mainly flocculates soil particles through adsorption and bridging. However, its effectiveness is highly dependent on the ionic environment of the solution. When sodium chloride and potassium chloride are removed, the ion concentration in the soil solution drops sharply, causing the polyacrylamide molecular chains to overextend, reducing effective adsorption sites. Simultaneously, the presence of monovalent ions maintains an alkaline environment and stabilizes the dissolution of sodium silicate. Replacing potassium chloride and sodium chloride with polyacrylamide affects the hydrolysis of sodium silicate.

[0080] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing solidified loess suitable for the construction of high-grade highway base courses, characterized in that, Includes the following steps: S1. Mix 4-5 parts cement, 4-5 parts lime and 90-92 parts loess evenly by weight to obtain mixture 1; S2. Add citric acid to distilled water, stir to dissolve, then add calcium lignosulfonate, calcium chloride and aluminum chloride, mix well to obtain curing solution A; S3. Mix the curing liquid A with the mixture 1 to obtain the mixture 2; S4. Mix sodium silicate with distilled water, dissolve it, then add polyacrylamide, sodium chloride and potassium chloride, mix evenly to obtain curing solution B; S5. Mix the curing liquid B with the mixture 2, add water and stir evenly to obtain the mixture 3, wherein the moisture content of the mixture 3 is 17.2%-18.6%; S6. Compact the mixture 3 to obtain solidified loess; In S2, by mass, the citric acid is 0.014 to 0.033 parts, the calcium lignosulfonate is 0.044 to 0.063 parts, the calcium chloride is 0.014 to 0.024 parts, and the aluminum chloride is 0.01 to 0.021 parts; In S4, by mass, the sodium silicate is 0.052-0.081 parts, the polyacrylamide is 0.02-0.03 parts, the sodium chloride is 0.018-0.027 parts, and the potassium chloride is 0.012-0.021 parts.

2. The preparation method according to claim 1, characterized in that, The mass ratio of citric acid to distilled water in S2 is 1:10-20.

3. The preparation method according to claim 1, characterized in that, The pH value of the curing solution A mentioned in S2 is 3.7~5.

6.

4. The preparation method according to claim 1, characterized in that, The mass ratio of sodium silicate to distilled water in S4 is 1:15-20.

5. The preparation method according to claim 1, characterized in that, The dissolution temperature described in S4 is 50~60℃.

6. The preparation method according to claim 1, characterized in that, By weight, S1 contains 4 parts cement, 4 parts lime, and 92 parts loess; S2 contains 0.014 parts citric acid, 0.046 parts calcium lignosulfonate, 0.02 parts calcium chloride, and 0.01 parts aluminum chloride; and S4 contains 0.052 parts sodium silicate, 0.021 parts polyacrylamide, 0.021 parts sodium chloride, and 0.016 parts potassium chloride.

7. The preparation method according to claim 1, characterized in that, The pH of the curing solution B mentioned in S4 is 10.3~11.7.

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