A soil solidifying agent and preparation method thereof

Abstract

The invention discloses a soil solidifying agent and a preparation method thereof, and belongs to the technical field of soil solidifying agents in highway engineering. The soil solidifying agent is mainly composed of the following components: 5% to 10% of steel slag powder, 10% to 20% of slag powder, 50% to 70% of quicklime blocks, 5% to 10% of waste gypsum, 2% to 5% of activator, and 5% to 10% of desulfurized ash. The initial setting time of the soil solidifying agent is about 12 hours, and the effective working time exceeds 24 hours. It is particularly suitable for the situation of uneven soil moisture, and is convenient for local re-pressing of the compacted surface on site, thereby improving the overall quality of construction; its unconfined compressive strength and CBR value are higher than those of soil solidified by cement, and it can replace traditional cement, lime, etc. for roadbed treatment in engineering, thereby improving the quality of engineering.

Description

Technical Field

[0001] The invention belongs to the technical field of soil solidifiers in highway engineering, and in particular to a soil solidifier and a preparation method thereof. Background Art

[0002] In the current rapidly developing field of infrastructure construction, innovation in soil stabilization technology is one of the key factors in promoting sustainable development and environmental protection. Although traditional soil stabilizers, such as cement and lime, have played an important role in history, their inherent limitations are becoming increasingly prominent. In particular, cement solidification, although it can quickly improve soil strength and shorten the construction period, its rapid solidification characteristics often lead to limited construction flexibility, and the large amount of heat and carbon dioxide released during the solidification process increases the environmental burden. In addition, cement-solidified soil is susceptible to chemical erosion and freeze-thaw cycles, and its long-term durability and impermeability are insufficient, affecting the overall quality and service life of the project.

[0003] With the increasing awareness of environmental protection and the advancement of science and technology, the market demand for new soil stabilizers is becoming increasingly urgent. It is expected that such stabilizers can overcome the defects of existing technologies while maintaining efficient soil reinforcement capabilities. The ideal new stabilizer should have the following key characteristics: First, it has a moderate setting time, which ensures the convenience of construction without affecting the progress of the project; second, it has a moderate initial strength to ensure construction safety and structural stability, and then gradually increases to reach or even exceed the long-term strength and durability of cement-solidified soil; third, it has excellent environmental adaptability and weather resistance, significantly improving the water penetration resistance, freeze-thaw resistance and chemical stability of the roadbed or structure, thereby extending the service life and reducing maintenance costs.

[0004] At present, although several studies have attempted to improve the performance of soil stabilizers through biopolymers, mineral admixtures, organic-inorganic composite materials, etc., they still face many challenges such as cost control, large-scale production feasibility and environmental impact assessment.

[0005] The invention with application number 201210157819.X discloses an inorganic soil solidifying agent and its preparation method. The components of the solidifying agent are: 28% to 45% cement clinker; 30% to 45% of secondary or higher fly ash; 10% to 15% of slag; 12% to 15% of quicklime; 1% to 3% of phosphogypsum; and alkaline activator. The raw materials are transported to a ball mill, ground for 12 to 15 minutes, and mixed and stirred until uniform to form a gray powder material with a specific surface area of ​​280 to 300 m 2 / kg, the residue after passing through a 80μm square hole sieve shall not exceed 4%; during construction, 6% to 15% of the above soil solidifier is mixed with loose soil, rolled and formed at the optimum soil moisture content, and then cured. The solidifier contains both cement clinker and quicklime, which may cause alkali aggregate reaction (AAR), a slow chemical reaction that can cause concrete expansion and cracking under certain conditions, affecting the stability and durability of the structure.

[0006] The invention with application number 202110368423.9 discloses a solid waste soil solidifier and its preparation process, a solid waste soil solidifier and its preparation process, comprising the following raw materials in percentage by mass: 18-20% of ordinary Portland cement (P.O42.5), 18-20% of waste phosphogypsum, 12-15% of quicklime, 10-15% of steel slag powder, 8-10% of fly ash, 0.08-0.1% of water reducer, 0.09-0.1% of accelerator, 1.3-3% of adsorbent, 2.5-3% of sodium carbonate, and 10-13.8% of additive. The solidifier component contains a high proportion of ordinary Portland cement and quicklime, which may lead to a slower early strength development of the solidified body, and due to the presence of quicklime, it may induce an alkali-aggregate reaction, affecting the long-term durability and stability of the solidified body, especially in humid or harsh environments.

[0007] The invention with application number 202111053822.2 discloses a humic acid soil solidifier and a preparation method thereof, wherein the mass percentage of each substance is: 25% to 40% steel slag, 15% to 25% fly ash, 10% to 15% quicklime, 10% to 20% ordinary Portland cement, 6% to 10% activator, 1% to 5% ion replacer, 1% to 3% hydrophobic agent, 4% to 6% retarder, 1% to 2% early strength agent, 1% to 3% filler, 1% to 3% stabilizer, 1% to 2% air entraining agent, 0.5% to 1% water reducer, and 0.5% to 2% humic acid modifier. However, the challenges brought by its complex formula, such as cost, operation, performance optimization, and environmental health risks, cannot be ignored.

[0008] Therefore, developing a new type of soil stabilizer that can effectively prolong the setting time, making construction more flexible, and can also show excellent strength growth in the later stage and significantly improve the durability and water resistance of the roadbed is not only a major breakthrough in existing technology, but also an important contribution to the sustainable development of future infrastructure construction. Summary of the invention

[0009] The first purpose of the present invention is to provide a soil solidifier with high compressive strength and economic and environmental protection. The soil solidifier is made by adding active excitation components to industrial solid wastes such as calcium carbide slag powder, desulfurization ash powder, slag powder, gypsum powder, etc., and then grinding them together to form a green and ecological industrial solid waste composite soil solidifier. The raw materials for the production of the soil solidifier are easily available, the production process is simple, and the cost is low.

[0010] To achieve the above purpose, the present invention provides a soil solidifying agent, which is mainly composed of the following components: 5% to 10% steel slag powder, 10% to 20% slag powder, 50% to 70% quicklime block, 5% to 10% waste gypsum, 2% to 5% activator, and 5% to 10% desulfurized ash.

[0011] The soil solidifier undergoes a series of physical and chemical reactions when mixed with soil, changing the microstructure and macroscopic properties of the soil, making it more stable and firm, and enhancing its engineering applicability, making it suitable for various civil engineering and infrastructure construction. The soil solidifier converts free water in the soil into the form of crystal water, so that water molecules are no longer free between soil particles in liquid form, but participate in the crystal structure of soil minerals or the soil solidifier, greatly reducing the water mobility in the soil and increasing the stability of the soil; in addition, the soil solidifier can reduce the current on the surface of the soil floccules, which helps to reduce the repulsive force between soil particles and promote the coagulation between particles; at the same time, the double electric layer adsorbed by the soil floccules is thinned under the action of the soil solidifier, which helps to tightly bind the soil particles; and the soil solidifier can enhance the electrolyte concentration in the soil, and the high concentration of electrolyte can more effectively compress the double electric layer around the soil particles, further promote the aggregation and coagulation of particles, and is conducive to the compaction of the soil structure; with the weakening of the repulsive force between soil particles and the aggregation of soil particles, the contact points between soil particles increase, the friction and cohesion between them increase, and the soil particles tend to be more closely arranged. In this process, the soil pores are filled with finer particles or crystal water, reducing the existence of large pores and improving the density and uniformity of the soil. This high density not only enhances the overall structural strength of the soil, but also greatly improves its unconfined compressive strength, CBR (California Bearing Ratio) and other properties, thereby extending the service life of the road, saving engineering maintenance costs, and achieving excellent economic and environmental benefits.

[0012] Preferably, the specific surface area of ​​the steel slag powder is ≥400m 2 / kg, 7d activity index ≥65%, 28d activity index ≥80%, density ≥2.8g / cm 3 , moisture content ≤2.0%.

[0013] Preferably, the specific surface area of ​​the slag powder is ≥400m 2 / kg, 7d activity index ≥70%, 28d activity index ≥95%, density ≥2.8g / cm 3 , moisture content ≤2.0%.

[0014] Preferably, the waste gypsum is in powder form, with a particle size of 5 to 150 μm and a calcium sulfate content of ≥80%.

[0015] Waste gypsum has different types due to different sources. For example, the waste residue produced by making phosphoric acid with phosphate ore and sulfuric acid is phosphogypsum, the gypsum generated when hydrofluoric acid is produced with calcium fluoride and sulfuric acid is fluorgypsum, and the gypsum produced in the process of making salt from seawater is salt gypsum, etc.; however, by controlling the quality of waste gypsum, the performance stability of the curing agent is improved.

[0016] Preferably, the activator is a powder material composed of potassium sulfate, phosphoric acid, sodium nitrate and sodium chloride.

[0017] More preferably, the mass ratio of potassium sulfate, phosphoric acid, sodium nitrate and sodium chloride is 0.5-1:1-3:1-2:1.

[0018] Preferably, the total content of effective calcium oxide and magnesium oxide in the quicklime block is ≥80%, and the undigested residue is ≤11.0%.

[0019] Preferably, the desulfurization ash is dry desulfurization ash. Dry desulfurization ash contains almost no water and is more stable than wet desulfurization ash.

[0020] Preferably, the soil solidifying agent also includes microsilica fume, which can improve the microstructure of the solidified body, enhance the long-term strength and durability of the solidified body, especially the impermeability and freeze-thaw resistance in a humid environment.

[0021] More preferably, the mass percentage of the microsilica powder is 2% to 6%.

[0022] Preferably, the particle size of the soil solidifier is less than 300 mesh.

[0023] The second object of the present invention is to provide a method for preparing the soil solidifier, which has a simple production process and low cost.

[0024] The preparation method of the soil solidifying agent comprises the following steps:

[0025] S1. Dehydrating all raw materials separately until the moisture content is less than 2wt%;

[0026] S2. According to a preset ratio, the raw materials dehydrated in step S1 are measured, the measured dehydrated raw materials are fully mixed to ensure uniform distribution of the components, and the mixed materials are ground to obtain the soil solidifying agent.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The soil solidifying agent provided by the present invention uses industrial waste residue as raw materials, which reduces costs and utilizes widely available resources. At the same time, compared with traditional materials such as lime and 42.5 cement, the carbon emissions are significantly reduced, which are only 15.56% of lime and 40.1% of 42.5 cement respectively. This helps to reduce environmental pollution, save natural resources, and meet the requirements of green and low-carbon development.

[0029] 2. The present invention reduces the amount of traditional cementing materials used, is conducive to resource conservation and energy protection, and has a positive impact on the ecological environment. In large projects such as highway construction, local materials can be used to support the sustainable development of highways, which is consistent with my country's policy of promoting a resource-saving and environmentally friendly society.

[0030] 3. By adjusting the proportion of components, the soil solidifier provided by the present invention can cooperate well with different types of soil and aggregates, has excellent road performance, and has a wide range of applications.

[0031] 4. The soil treated with the soil solidifier provided by the present invention has good mechanical properties, and its unconfined compressive strength and CBR value are higher than those of the soil solidified by cement. It can replace traditional cement, lime, etc. for roadbed treatment in engineering, thereby improving engineering quality.

[0032] 5. The soil solidifier provided by the present invention has an initial setting time of about 12 hours and an effective working time of more than 24 hours. It is particularly suitable for situations where soil moisture is uneven, and is convenient for local re-compaction of the compacted surface on site, thereby improving the overall quality of construction. DETAILED DESCRIPTION

[0033] The technical scheme of the present invention is further described below by way of examples. The raw materials used in the examples can be purchased from the market or prepared by conventional methods.

[0034] Example 1

[0035] A soil solidifying agent, wherein the weight percentages of the components are: 5% steel slag powder, 15% slag powder, 60% quicklime blocks, 8% waste gypsum, 4% activator, and 8% desulfurized ash; the activator is compounded from potassium sulfate, phosphoric acid, sodium nitrate and sodium chloride in a mass ratio of 1:1:1:1.

[0036] The soil solidifying agent is prepared by the following preparation method:

[0037] S1. Dehydrate the raw materials, steel slag powder, phosphogypsum, desulfurized ash, quicklime blocks, and slag powder, respectively, using a dryer at 60°C until the moisture content is less than 2%;

[0038] S2. According to 500g of steel slag powder, 1500g of slag powder, 6000g of quicklime block, 800g of waste gypsum, 400g of activator and 800g of desulfurized ash, the materials were mixed evenly and ground at a speed of 38r / min for 20min using a conical ball mill (purchased from Red Star Machine, model φ900*1800). All the ground materials were sieved through a 300-mesh standard sieve to obtain a soil solidifier having a particle size less than 300 mesh.

[0039] Example 2

[0040] A soil solidifying agent, wherein the weight percentages of the components are: 6% steel slag powder, 20% slag powder, 57% quicklime blocks, 6% waste gypsum, 5% activator, and 6% desulfurized ash; the activator is compounded from potassium sulfate, phosphoric acid, sodium nitrate and sodium chloride in a mass ratio of 0.5:1:2:1.

[0041] The soil solidifying agent is prepared by the following preparation method:

[0042] S1. Dehydrate the raw materials, steel slag powder, phosphogypsum, desulfurized ash, quicklime blocks, and slag powder, respectively, using a dryer at 60°C to a moisture content of less than 2%;

[0043] S2. According to the ratio of 600g steel slag powder, 2000g slag powder, 5700g quicklime block, 600g waste gypsum, 500g activator, and 600g desulfurization ash, the materials were mixed evenly with a conical ball mill (purchased from Red Star Machine, model ) was ground at a speed of 38 r / min for 18 min, and all the ground materials were sieved through a 300-mesh standard sieve to obtain the soil solidifying agent with a particle size less than 300 mesh.

[0044] Example 3

[0045] A soil solidifying agent, wherein the weight percentages of the components are: 7% steel slag powder, 18% slag powder, 55% quicklime block, 10% waste gypsum, 3% activator, and 7% desulfurized ash; the activator is compounded from potassium sulfate, phosphoric acid, sodium nitrate and sodium chloride in a mass ratio of 1:3:2:1.

[0046] The soil solidifying agent is prepared by the following preparation method:

[0047] S1. Dehydrate the raw materials such as steel slag powder, phosphogypsum, desulfurized ash, quicklime block, slag powder, etc. in a dryer at 60°C until the moisture content is less than 2%;

[0048] S2. According to the ratio of 700g steel slag powder, 1800g slag powder, 5500g quicklime block, 1000g waste gypsum, 300g activator, and 700g desulfurization ash, the materials were mixed evenly with a conical ball mill (purchased from Red Star Machine, model ) was ground at a speed of 38 r / min for 15 min, and all the ground materials were sieved through a 300-mesh standard sieve to obtain the soil solidifying agent with a particle size less than 300 mesh.

[0049] Example 4

[0050] A soil solidifier, wherein the weight percentages of the components are: 5% steel slag powder, 13% slag powder, 60% quicklime blocks, 8% waste gypsum, 4% activator, 8% desulfurized ash, and 2% microsilica powder; the activator is compounded from potassium sulfate, phosphoric acid, sodium nitrate and sodium chloride in a mass ratio of 1:1:1:1.

[0051] The soil solidifying agent is prepared by the following preparation method:

[0052] S1. Dehydrate the raw materials, steel slag powder, phosphogypsum, desulfurized ash, quicklime block, slag powder and microsilica powder, respectively, in a dryer at 60°C until the moisture content is less than 2%;

[0053] S2. According to the ratio of 500g steel slag powder, 1300g slag powder, 6000g quicklime block, 800g waste gypsum, 400g activator, 800g desulfurization ash and 200g microsilica powder, the materials were mixed evenly with a conical ball mill (purchased from Red Star Machine, model ) was ground at a speed of 38 r / min for 20 min, and all the ground materials were sieved through a 300-mesh standard sieve to obtain the soil solidifying agent with a particle size less than 300 mesh.

[0054] Example 5

[0055] A soil solidifier, wherein the weight percentages of the components are: 5% steel slag powder, 10% slag powder, 60% quicklime blocks, 8% waste gypsum, 4% activator, 7% desulfurized ash, and 6% microsilica powder; the activator is a compound prepared from potassium sulfate, phosphoric acid, sodium nitrate and sodium chloride in a mass ratio of 1:1:1:1.

[0056] The soil solidifying agent is prepared by the following preparation method:

[0057] S1. Dehydrate the raw materials, steel slag powder, phosphogypsum, desulfurized ash, quicklime block, slag powder and microsilica powder, respectively, in a dryer at 60°C until the moisture content is less than 2%;

[0058] S2. According to the ratio of 500g steel slag powder, 1000g slag powder, 6000g quicklime block, 800g waste gypsum, 400g activator, 700g desulfurization ash and 600g microsilica powder, the materials were mixed evenly with a conical ball mill (purchased from Red Star Machine, model ) was ground at a speed of 38 r / min for 20 min, and all the ground materials were sieved through a 300-mesh standard sieve to obtain the soil solidifying agent with a particle size less than 300 mesh.

[0059] Experimental Results

[0060] The soil solidifier and cement prepared in Examples 1 to 5 were respectively added to the soil by the external addition method, and the addition amount was 3% of the soil mass. The optimum moisture content of the solidified soil mixture was determined with reference to JTG 3441-2024 "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering". Water was added according to the optimum moisture content of the solidified soil mixture and compacted uniformly. The soil was maintained according to the test method in JTG 3441-2024 "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering". After reaching the age, the various properties of the solidified soil were tested.

[0061] The CBR value and unconfined compressive strength of the stabilized soil were determined with reference to JTG 3430-2020 "Highway Geotechnical Test Code".

[0062] Refer to CJ / T 486-2015 "Soil Stabilization Admixtures" to determine the 4h setting time influence coefficient of stabilized soil.

[0063] Table 1 Performance data of stabilized soil

[0064]

[0065] It can be seen from the CBR data in Table 1 that, under the same dosage conditions, the CBR value of the solidified soil treated with the soil solidifier provided by the present invention is significantly higher than the CBR value of the solidified soil treated with cement. The CBR value is an important indicator for measuring the bearing capacity of a material. A high CBR value indicates that the solidified soil has better bearing capacity and stability and is more suitable for use as a road base or subbase. And the CBR value of the solidified soil treated with the soil solidifier provided by the present invention is higher than the requirement of JTG / T 3610-2019 "Technical Specifications for Highway Roadbed Construction" that the CBR value of the upper roadbed is greater than 8%, indicating that the solidified soil treated with the soil solidifier provided by the present invention not only meets the requirements of the specification, but also provides more superior performance.

[0066] It can be seen from the data of unconfined compressive strength in Table 1 that under the same dosage conditions, the growth rate of unconfined compressive strength of the solidified soil treated with the soil solidifier provided by the present invention is faster than that of the solidified soil treated with cement solidification, and the 28d unconfined compressive strength of the solidified soil treated with the soil solidifier provided by the present invention is higher than that of the solidified soil treated with cement solidification, which not only shows that the solidified soil treated with the soil solidifier provided by the present invention has a higher early strength, but also the continuous growth of its later unconfined compressive strength also reflects that the solidified soil has good water resistance. Good water resistance means that the solidified soil can still maintain high mechanical properties in a humid or water-saturated environment, which is particularly important for projects that need to withstand the influence of water environment for a long time.

[0067] It can be seen from the data of the 4h setting time influence coefficient in Table 1 that under the same dosage conditions, the 4h setting time influence coefficient of the solidified soil treated with the soil solidifying agent provided by the present invention is greater than the 4h setting time influence coefficient of the solidified soil treated with cement solidification. This shows that the initial setting time of the solidified soil treated with the soil solidifying agent provided by the present invention is longer, and the effective working time after mixing exceeds 24h. The longer working time is conducive to construction operation and improves the flexibility and efficiency of construction, especially in large-scale or complex terrain projects, the construction team has more time to complete mixing, transportation, laying and compaction.

[0068] The soil solidifying agent provided by the present invention has a short construction period, simple construction equipment, and greatly reduced labor costs, machinery rental fees, and fuel costs. Moreover, the soil solidifying agent provided by the present invention utilizes a large amount of industrial solid waste materials, reduces the amount of traditional cementing materials used, is beneficial to resource conservation and energy conservation, and is beneficial to the protection of the ecological environment. In addition, the soil solidifying agent provided by the present invention, as an improved material, reduces the construction cost while also protecting the surrounding environment of the construction, and has obvious economic and environmental benefits.

[0069] It should be understood that the above embodiments are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims

1. A soil solidifying agent, characterized in that: The invention mainly consists of the following components: 5%-10% steel slag powder, 10%-20% slag powder, 50%-70% quicklime block, 5%-10% waste gypsum, 2%-5% activator, and 5%-10% desulfurization ash; the activator is a powder material composed of potassium sulfate, phosphoric acid, sodium nitrate, and sodium chloride; the powder material composed of potassium sulfate, phosphoric acid, sodium nitrate, and sodium chloride is compounded according to a mass ratio of 0.5-1:1-3:1-2:

1.

2. The soil solidifying agent according to claim 1, characterized in that: The specific surface area of ​​the steel slag powder is ≥400 m 2 / kg, 7-day activity index ≥65%, 28-day activity index ≥80%, density ≥2.8 g / cm 3 , moisture content ≤2.0%.

3. The soil solidifying agent according to claim 1, characterized in that: The specific surface area of ​​the slag powder is ≥400 m 2 / kg, 7-day activity index ≥70%, 28-day activity index ≥95%, density ≥2.8 g / cm 3 , moisture content ≤2.0%.

4. The soil solidifying agent according to claim 1, characterized in that: The total content of effective calcium oxide and magnesium oxide in the quicklime block is ≥80%, and the undigested residue is ≤11.0%.

5. The soil solidifying agent according to claim 1, characterized in that: The waste gypsum is in powder form, with a particle size of 5-150 μm and a calcium sulfate content of ≥80%.

6. The soil solidifying agent according to claim 1, characterized in that: The desulfurization ash is dry desulfurization ash.

7. The soil solidifying agent according to claim 1, characterized in that: The particle size of the soil solidifying agent is less than 300 meshes.

8. A method for preparing the soil solidifying agent according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Dehydrate all raw materials separately until the moisture content is less than 2wt%; S2. According to a preset ratio, the raw materials dehydrated in step S1 are measured, the measured dehydrated raw materials are fully mixed to ensure uniform distribution of the components, and the mixed materials are ground to obtain the soil solidifying agent.

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